Mechanic A

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Limitations....................................................................... 2 Mechanica Wildfire Installation Issues ....................................................... 2 HP........................................................................................................ 2 Getting Started with Mechanica ..................................................................... 3 Getting Started ......................................................................................... 3 Configuration File Options .......................................................................... 3 config.pro Overview................................................................................ 4 config.pro Options .................................................................................. 4 Mechanica Products ..................................................................................21 Introducing the Mechanica Product Line....................................................21 Mechanica Structure ..............................................................................21 Mechanica Thermal................................................................................22 Mechanica Workflow .................................................................................23 Native Mode Workflow ...........................................................................23 FEM Mode Workflow...............................................................................24 Operating Modes ...................................................................................25 Integrated Mode....................................................................................26 Independent Mode.................................................................................27 vii Table of Contents Operating Mode Comparison ...................................................................28 Planning and Modeling Considerations.........................................................28 Building Part and Assemblies ..................................................................29 Using Effective Modeling Techniques ........................................................36 Planning for Optimization .......................................................................46 User Interface Basics for Integrated Mode ...................................................48 Working With the User Interface..............................................................48 Using Dialog Boxes and Message Boxes....................................................48 Mechanica Toolbar.................................................................................50 Process Guide .......................................................................................52 Selection Methods .................................................................................52 Using Layers.........................................................................................52 Managing Modeling Entities Through Suppression and Family Tables ............54 Simulation Display.................................................................................55 Color References ...................................................................................59 Getting Information on Your Model ..........................................................60 Removing Simulation Entities from Your Model ..........................................60 Transferring Your Model to Independent Mode...........................................61 Printing Your Model ...............................................................................61 Changing Configuration Settings..............................................................61 Setting Environment Variables ................................................................62 Online Help .............................................................................................63 Getting Help for Mechanica .....................................................................63 Online Help for Mechanica ......................................................................63 Supplemental Online Documents for Mechanica .........................................64 viii Table of Contents Simulation Advisor ................................................................................65 Viewing Specifications for Simulation Advisor ............................................65 Using Simulation Advisor ........................................................................66 Using Online Help ..................................................................................66 Troubleshooting Browser Problems For Simulation Advisor ..........................67 To Customize the Mechanica Toolbar ..........................................................68 To Control Icon Appearance.......................................................................68 To Set Icon Visibilities for Modeling Entities .................................................68 To Suppress Modeling Entities Through a Family Table ..................................68 To Set Icon Visibilities for Loads and Constraints ..........................................69 To Set Simulation Entity Prehighlighting Filters ............................................70 To Move the Mechanica Toolbar .................................................................70 Optimizing a Model (Native Mode) ..............................................................70 Developing a Model (Native Mode) .............................................................71 Defining Design Changes (Native Mode) ......................................................73 Analyzing a Model (Native Mode)................................................................73 Search Tool .............................................................................................73 Controlling Mesh Display ...........................................................................74 Comparing Mirror and Cyclic Symmetry.......................................................75 Defining an Analysis (FEM Mode)................................................................76 Solving a Model (FEM Mode) ......................................................................76 FEM Mode ...............................................................................................77 Creating a Mesh (FEM Mode) .....................................................................77 Developing a Model (FEM Mode).................................................................78 Tolerance Report......................................................................................79 ix Table of Contents Suppression and Family Tables ..................................................................80 Simulation Model .....................................................................................81 Displaying the Mesh Model ........................................................................82 Mechanica Mass Properties ........................................................................82 Example: Dependent Movement in Patterned Features ..................................83 When a Nonessential Feature Causes Unexpected Model Behavior Changes......84 Mechanica Fatigue Advisor ........................................................................84 Example: Avoiding Interference .................................................................85 When a Nonessential Feature Provides Hidden Benefits .................................85 Example: Using a Simplified Part................................................................86 FEM Mesh Display Buttons .........................................................................87 Example: Modeling Specialized Loads with a Cylindrical Coordinate System .....87 Controlling FEM Mesh Display ....................................................................88 Example: Pre-planning for Shape Changes ..................................................90 SIM SELECT Menu ....................................................................................91 Object Action Shortcut Menu .....................................................................92 Methods of Simplifying Your Model .............................................................92 Customizing the Mechanica Toolbar ............................................................93 Permanent and Session-based Configuration Files ........................................93 Building and Saving Queries ......................................................................94 Assembly Modeling Entities, Idealizations, and Connections ...........................94 Guidelines and Tips for Using Datum Points .................................................95 Considerations for Multiple Model Sessions ..................................................96 Pro/ENGINEER Parameters as Measures ......................................................96 Pro/ENGINEER Parameters as Design Parameters .........................................96 x Table of Contents Example: Featuring Your Part ....................................................................97 Driven and Driving Parameters ..................................................................98 Model Accuracy........................................................................................99 Object Action......................................................................................... 100 Example: Setting up a Solid Model for a 2D Analysis on an Internal Surface... 100 Connected and Unconnected Parts............................................................ 102 Search Tool Dialog Box ........................................................................... 103 Units .................................................................................................... 104 To Set a Principal System of Units ......................................................... 104 To Review an Individual Unit................................................................. 105 To Review a System of Units................................................................. 105 To Edit a Custom Unit .......................................................................... 105 To Edit a Custom System of Units.......................................................... 106 To Create a Custom Unit ...................................................................... 106 Units Management............................................................................... 107 Systems of Units Management .............................................................. 108 Custom Unit ....................................................................................... 108 Custom System of Units ....................................................................... 109 Guidelines for Specifying Units .............................................................. 110 Unit Conversion Tables......................................................................... 111 Introduction ....................................................................................... 111 Basic Equalities ................................................................................... 112 System of Units .................................................................................. 115 Basic Units ......................................................................................... 117 xi Table of Contents Examples of Values for Gravitational Acceleration and Selected Properties of Steel ................................................................................................. 120 Correspondence Between Mass and Force ............................................... 120 Correspondence Between Mass and Pounds-mass .................................... 121 Conversion of Basic Units ..................................................................... 121 Correspondence Between Degrees Celsius and Degrees Fahrenheit ............ 125 Predefined Systems of Units ................................................................. 126 Predefined Units .................................................................................. 127 Set the Principal System of Units ........................................................... 127 About Units ........................................................................................ 128 To Create a Custom System of Units ...................................................... 129 Modeling Structure and Thermal Problems.................................................... 129 About Creating Models in Mechanica ......................................................... 129 Model Type ........................................................................................... 130 About Specifying a Product, Mode, and Model Type .................................. 130 About Model Types .............................................................................. 131 Structure Model Types ......................................................................... 132 Thermal Model Type ............................................................................ 135 Guidelines for Working with Model Types ................................................ 138 To Specify a Product, Mode, and Model Type ........................................... 138 To Define 2D Model Types .................................................................... 139 Example: 2D Axisymmetric Modeling ..................................................... 140 Example: 2D Plane Strain Modeling........................................................ 140 Features ............................................................................................... 141 About Features ................................................................................... 141 xii Table of Contents Datum Features in Pro/ENGINEER and Mechanica .................................... 142 Creating Features ................................................................................ 142 Datum Point ....................................................................................... 144 Datum Plane....................................................................................... 145 Datum Axis ........................................................................................ 145 Datum Curve ...................................................................................... 146 Coordinate Systems............................................................................. 147 Surface Region.................................................................................... 156 Volume Region.................................................................................... 158 Connections .......................................................................................... 160 About Connections............................................................................... 160 Welds ................................................................................................ 161 Rigid Connections................................................................................ 166 Fasteners ........................................................................................... 168 Contact Regions .................................................................................. 179 Condensation Interfaces....................................................................... 181 Rigid Links (FEM mode)........................................................................ 181 Weighted Links (FEM mode).................................................................. 183 Interfaces........................................................................................... 185 Gaps (FEM mode)................................................................................ 188 Precedence Rules ................................................................................ 190 Weighted Link Icon .............................................................................. 192 Reference Entities for Weighted Links..................................................... 192 Override Coordinate System for Weighted Links ...................................... 193 Example: Bending Stiffness .................................................................. 193 xiii Table of Contents Rigid Link Icon .................................................................................... 194 Override Coordinate System for Rigid Links............................................. 195 Guidelines for Surface-Surface Connections and Interfaces (FEM mode)...... 195 Rotation and Separation ....................................................................... 196 Example: Fix Rotations ........................................................................ 197 Degrees of Freedom for Rigid Links........................................................ 198 Pass or Fail Results — 2D ..................................................................... 199 Pass or Fail Results — 3D ..................................................................... 199 About Interfaces ................................................................................. 199 Example: Screw Fastener ..................................................................... 200 Axial Stiffness ..................................................................................... 200 Normal Stiffness.................................................................................. 201 Example: Intervening Geometry............................................................ 207 Example: Carries Shear........................................................................ 208 Reviewing Contact Regions ................................................................... 209 Idealizations.......................................................................................... 210 About Idealizations .............................................................................. 210 Shells ................................................................................................ 210 Beams ............................................................................................... 225 Masses............................................................................................... 230 Springs .............................................................................................. 234 Precedence Rules ................................................................................ 239 Results When Using Automatic Midsurface Connections ............................ 241 Spring References ............................................................................... 242 Extra Tab on Beam Definition Dialog Box ................................................ 243 xiv Table of Contents Auto Detect Paired Surfaces.................................................................. 243 Guidelines for Assigning Mass Properties ................................................ 243 Parameter-Capable Edit Fields............................................................... 244 Fix and Flip Normals ............................................................................ 245 Example: Geometric Precedence Rules ................................................... 245 Example: Invalidating a Modeling Entity ................................................. 246 Example: Multiconstant-Thickness Pairs ................................................. 247 Point–Point Pairs ................................................................................. 248 Example: Collet Illustration................................................................... 249 Example: Unpaired Surface on L-Bracket ................................................ 250 Omit Unopposed Surfaces..................................................................... 250 Example: T-Bracket ............................................................................. 251 Example: Part with Unopposed Surfaces ................................................. 251 Example: Assembly Model with Gap ....................................................... 252 Masses Based on Components (FEM mode)............................................. 253 Properties According to Mass Type (FEM mode) ....................................... 254 Surfaces and Curves Used in Shell Definition........................................... 254 Masses Based on Components............................................................... 255 Properties ............................................................................................. 256 About Properties ................................................................................. 256 Deleting Properties .............................................................................. 256 Background Information ....................................................................... 257 Beam Sections .................................................................................... 258 Beam Orientation ................................................................................ 264 Beam Releases ................................................................................... 267 xv Table of Contents Shell Properties................................................................................... 269 Spring Properties................................................................................. 276 Mass Properties................................................................................... 281 Materials ............................................................................................ 282 Material Orientation ............................................................................. 305 Reentrant Corners ............................................................................... 312 Display AutoGEM Messages................................................................... 312 Creating............................................................................................. 313 Example: Brick.................................................................................... 313 Boundary Processing Takes Too Long ..................................................... 313 Automatic Interrupt ............................................................................. 314 Max Aspect Ratio................................................................................. 314 Allowable Edge and Face Angles ............................................................ 315 AutoGEM Overconstrained .................................................................... 316 Required Modeling Entities.................................................................... 316 Create Links Where Needed .................................................................. 317 AutoGEM Interruption Guidelines ........................................................... 317 Detailed Fillet Modeling ........................................................................ 317 Minimum and Maximum Angles ............................................................. 318 Create a Full Set of Elements ................................................................ 318 Shell , 2D Plate Element Type, 2D Solid Element Type.............................. 319 Solids ................................................................................................ 319 Invalid Curves for 2D Axisymmetric Models............................................. 320 Example: Wedge ................................................................................. 321 Example: Point Loads........................................................................... 321 xvi Table of Contents Max Edge Turn (Degrees) ..................................................................... 323 Validate ............................................................................................. 323 Example: Tetra ................................................................................... 323 Invalid Surfaces for 2D Axisymmetric Models .......................................... 323 Modify or Delete Existing Elements ........................................................ 324 Point Loads, Point Constraints, Point Heat Loads, Point Prescribed Temperatures, Point Convection Conditions............................................. 324 Move or Delete Existing Points .............................................................. 325 Example: Insert Points ......................................................................... 326 Insert Points ....................................................................................... 327 Example: Reentrant Corners ................................................................. 328 Fatigue Properties ............................................................................... 329 Thermal Values for Orthotropic Properties............................................... 330 Shear Modulus .................................................................................... 330 Projected Vector.................................................................................. 331 Poisson's Ratio .................................................................................... 331 Parameter-Capable Edit Fields............................................................... 332 Order of Rotation ................................................................................ 332 Example: Material Directions................................................................. 333 Material Directions 1, 2, and 3 .............................................................. 333 Transversely Isotropic Properties ........................................................... 334 Thermal Values for Transversely Isotropic Properties................................ 334 Review Stiffness.................................................................................. 335 Review Layup ..................................................................................... 335 Material Property Requirements — Failure Criterion.................................. 336 xvii Table of Contents Example: Project a Vector onto a Surface ............................................... 337 Warp & Mass Tab ................................................................................ 337 Square............................................................................................... 338 Rotate About ...................................................................................... 338 Property Type ..................................................................................... 339 Example: Applying a Material to a Solid Portion of Your Model ................... 340 Tsai Definition for Poisson's Ratios ......................................................... 341 Example: Orienting the BSCS to the BACS .............................................. 342 Example: Orienting the BSCS Shear Center ............................................ 343 Review Beam Section Properties............................................................ 344 Coefficient of Thermal Expansion — Isotropic .......................................... 346 Tsai-Wu Failure Criterion ...................................................................... 346 Calculate Stresses and Strains .............................................................. 346 Structural Options for Material Definition ................................................ 347 Thermal Options for Material Definition................................................... 348 Thickness ........................................................................................... 348 Working with the Laminate Layup Dialog Box .......................................... 348 Layup ................................................................................................ 349 Example: Material Coordinate System for a Cylindrical UCS....................... 350 Young's Modulus — Isotropic................................................................. 350 Poisson's Ratio — Isotropic ................................................................... 350 Isotropic Properties ............................................................................. 351 Isotropic ............................................................................................ 351 Maximum Strain Failure Criterion........................................................... 351 Example: Curved Surface Directions ...................................................... 352 xviii Table of Contents Failure Criterion .................................................................................. 352 Coefficient of Thermal Expansion ........................................................... 353 Ultimate Compressive Strength ............................................................. 353 Example: Laminate Layup .................................................................... 354 Example: Variable Material Orientation................................................... 354 Example: Rotation for Shells and Surfaces .............................................. 355 Modified Mohr Failure Criterion .............................................................. 355 Maximum Shear Stress (Tresca) Failure Criterion..................................... 355 Density .............................................................................................. 356 Example: Laminate Orientation ............................................................. 356 Orientation ......................................................................................... 357 Young's Modulus ................................................................................. 357 Number ............................................................................................. 358 Example: 2D Surface Directions ............................................................ 358 Normalized Tsai-Wu Interaction Term .................................................... 358 Thermal Values for Isotropic Properties .................................................. 358 Material or Sub-laminate ...................................................................... 359 Shell Thickness ................................................................................... 359 Solid Circle ......................................................................................... 360 Stress Grids........................................................................................ 361 Example: Cylindrical Coordinate System................................................. 361 Maximum Stress Failure Criterion .......................................................... 361 Distortion Energy (von Mises) Failure Criterion ........................................ 362 Function — Material Properties .............................................................. 362 Rectangle ........................................................................................... 362 xix Table of Contents L-Section ........................................................................................... 363 Beam Sections Dialog Box .................................................................... 364 General.............................................................................................. 365 Factors Determining the Selection of Entities........................................... 365 Hollow Rect ........................................................................................ 366 Material Assignment in Part Mode and Assembly Mode ............................. 366 J ....................................................................................................... 367 Coordinate System Types ..................................................................... 367 Cost .................................................................................................. 368 Orthotropic......................................................................................... 368 Parameter Button ................................................................................ 368 Referenced Coordinate System.............................................................. 369 Shear Strength ................................................................................... 369 Ultimate Tensile Strength (UTS) ............................................................ 370 Transversely Isotropic.......................................................................... 370 Solid Ellipse ........................................................................................ 370 Iyy, Iyz, Izz ........................................................................................ 371 Hollow Ellipse ..................................................................................... 371 Hollow Circle....................................................................................... 372 Diamond ............................................................................................ 373 Area .................................................................................................. 373 Channel ............................................................................................. 374 I-Beam .............................................................................................. 375 Shear FY, Shear FZ.............................................................................. 375 Shear DY, Shear DZ............................................................................. 376 xx Table of Contents Structural Constraints ............................................................................. 376 About Structure Constraints.................................................................. 376 Adding Constraints .............................................................................. 377 Constraints, Loads, and Analysis Types .................................................. 378 Constraints on Entities ......................................................................... 380 Guidelines for Structure Constraint Sets ................................................. 380 Guidelines for Structure Constraints....................................................... 381 Displacement Constraints ..................................................................... 382 Symmetry Constraints ......................................................................... 388 Along Surface Constraints..................................................................... 394 Structure Constraints on Geometry ........................................................ 395 About Thermal Boundary Conditions ...................................................... 396 Example: Axis of Symmetry.................................................................. 397 Constraints on Compressed Midsurfaces ................................................. 397 Troubleshooting Constraints.................................................................. 398 Example: Cut for Cyclic Symmetry......................................................... 398 Guidelines for Prescribed Displacement Constraints.................................. 399 Structure Constraints on Regions........................................................... 399 Structure Constraints on Datum Points ................................................... 400 Structure Constraints and Coordinate Systems ........................................ 400 Improperly Constrained Springs, Beams, or Shells ................................... 401 Improperly Connected Idealizations ....................................................... 402 Problems with Elements ....................................................................... 402 Insufficiently Constrained Models........................................................... 403 Problems with Loads and Constraints ..................................................... 403 xxi Table of Contents Singularities and Loads ........................................................................ 404 Singularities and Constraints................................................................. 404 Strategy: Minimizing Singularities.......................................................... 405 Singularities ....................................................................................... 405 Problems with Properties ...................................................................... 406 Constraints and Loads on Compressed Geometry..................................... 406 Thermal Boundary Conditions .................................................................. 407 Guidelines for Thermal Boundary Conditions ........................................... 407 Guidelines for Thermal Boundary Conditions for Geometry ........................ 407 Boundary Condition Sets ...................................................................... 408 Convection Conditions.......................................................................... 409 Prescribed Temperatures ...................................................................... 421 Radiation Conditions (FEM Mode)........................................................... 425 To Define a Radiation Condition............................................................. 426 To Use External Conv Coefficient Spatial Variation for 3D Models ............... 427 To Use External Conv Coef & Bulk Temp Spatial Variation for 3D Models ..... 427 To Use Uniform Spatial Variation for 3D Models ....................................... 428 To Use External Bulk Temperature Spatial Variation for 3D Models ............. 428 Variations for Convection Conditions in FEM Mode.................................... 429 Understanding Thermal Boundary Condition Sets..................................... 429 Structure Loads ..................................................................................... 430 About Loads ....................................................................................... 430 About Structure Loads ......................................................................... 430 Relations Functions for Loads and Constraints ......................................... 431 Load Basics ........................................................................................ 432 xxii Table of Contents Guidelines for Structure Loads .............................................................. 434 Guidelines for Load Sets....................................................................... 434 Force and Moment Loads...................................................................... 436 Bearing Loads ..................................................................................... 440 Centrifugal Loads ................................................................................ 442 Gravity Loads ..................................................................................... 445 Pressure Loads.................................................................................... 447 Temperature Loads.............................................................................. 450 Mechanism Loads ................................................................................ 457 Troubleshooting Your Loads .................................................................. 459 To Define Structural Temperature Loads................................................. 461 Function of Coordinates........................................................................ 461 Example: Function of Coordinates.......................................................... 462 Functional Form of Interpolation............................................................ 462 Structural Temperature Loads ............................................................... 463 Structure Loads on Regions .................................................................. 464 Example: Bearing Load ........................................................................ 465 Example: Bearing Load on an Open Curve .............................................. 465 Sample FNF File for External Temperature .............................................. 465 Example: Bearing Load on a Surface ...................................................... 467 Strategy: Scaling Results for Centrifugal Loads in a Combined Load Set...... 467 Add for Interpolation............................................................................ 467 Structure Loads on Points ..................................................................... 468 Force Per Unit Type ............................................................................. 469 Load Interpolation ............................................................................... 470 xxiii Table of Contents Total Load .......................................................................................... 470 Total Load At Point .............................................................................. 471 Remove for Interpolation...................................................................... 472 How Loads Transfer to Structure ........................................................... 472 Force Per Unit Type Guidelines .............................................................. 474 From and To Fields for Dir Points & Mag ................................................. 474 Structure Loads on Geometry ............................................................... 475 How Structure Imports Loads from Mechanism Design ............................. 475 Interpolated Over Entity ....................................................................... 476 Load Resultant Dialog Box for Structure Loads ........................................ 476 Mechanism Load Import Dialog Box ....................................................... 477 Guidelines for Spatially Varying Loads .................................................... 478 Example: Pressure Load ....................................................................... 479 Example: Spatially Varying Loads .......................................................... 479 Preview for Interpolation ...................................................................... 481 Thermal Loads ....................................................................................... 481 About Loads ....................................................................................... 481 About Heat Loads ................................................................................ 481 Guidelines for Heat Loads ..................................................................... 482 Guidelines for Load Sets....................................................................... 482 Defining Heat Loads............................................................................. 484 Defining Component Heat Loads............................................................ 488 FEM Heat Loads .................................................................................. 490 Reviewing Total Heat Loads .................................................................. 492 To Review Total Heat Loads .................................................................. 492 xxiv Table of Contents Load Resultant Dialog Box for Heat Loads ............................................... 492 Heat Loads on Internal Surfaces ............................................................ 493 Units According to Model Type and Entity ............................................... 494 Measures .............................................................................................. 494 About Simulation Measures................................................................... 494 Uses of Measures ................................................................................ 495 Measure Basics ................................................................................... 495 Measures Dialog Box............................................................................ 512 Measures Definition Dialog Box ............................................................. 514 Results Available for Measures .............................................................. 533 Selecting One or More Measures............................................................ 533 To Define a Failure Index Measure ......................................................... 534 To Define a Center of Mass Measure ...................................................... 534 To Define a Displacement Measure ........................................................ 535 To Define a Velocity Measure ................................................................ 535 To Define a Fatigue Measure ................................................................. 535 To Define a Force Measure.................................................................... 536 To Define a Moment of Inertia Measure .................................................. 536 To Define a Moment Measure ................................................................ 537 To Define a Rotation Measure ............................................................... 537 To Define a Contact Measure ................................................................ 537 To Define a Driven Pro Parameter Measure ............................................. 538 To Define a Heat Flux or Temperature Gradient Measure .......................... 538 To Define a Phase Measure ................................................................... 539 To Define a Rotational Acceleration Measure ........................................... 539 xxv Table of Contents To Define a Rotational Velocity Measure ................................................. 539 To Define a Temperature Measure ......................................................... 540 To Define a Time Measure .................................................................... 540 To Define a Stress or Strain Measure ..................................................... 540 To Define an Acceleration Measure ........................................................ 541 Time/Frequency Eval ........................................................................... 541 RMS .................................................................................................. 541 Maximum ........................................................................................... 542 Max Absolute ...................................................................................... 542 Minimum............................................................................................ 542 Example: Near Point Measures and Model Types...................................... 543 Component — Dynamic Analyses........................................................... 543 Component — Thermal Analyses ........................................................... 544 At Each Step — Time or Frequency Evaluation Method.............................. 544 Minimum — Time or Frequency Evaluation Method................................... 545 Quantity — Basic Analyses.................................................................... 545 At Each Step....................................................................................... 546 Example: Near Point Measures and Geometric Intersection ....................... 546 Maximum — Time or Frequency Evaluation Method .................................. 547 Component — Stress and Strain Quantities ............................................. 547 Component — Basic Analyses................................................................ 547 Global Spatial Evaluation Methods ......................................................... 548 Measures Not Calculated for Dynamic Random ........................................ 548 Datum Points for User-Defined Measures ................................................ 548 Time/Frequency Eval Options ................................................................ 549 xxvi Table of Contents Component — Center of Mass Quantities ................................................ 550 Component — Stress, Strain ................................................................. 550 Quantity — Dynamic Analyses............................................................... 551 Quantity — Thermal Analyses ............................................................... 552 Spatial Evaluation Method — Basic and Dynamic Analyses ........................ 552 Spatial Evaluation Method — Thermal Analyses ....................................... 553 Time or Frequency Evaluation Method — Dynamic Analyses ...................... 554 Component — Moment of Inertia Quantities ............................................ 555 Component — Displacement, Rotation, and Reaction Quantities................. 555 Apparent Frequency............................................................................. 556 Component — Contact Force Quantity .................................................... 556 Time Evaluation Method — Thermal Analyses .......................................... 556 Maximum Absolute — Time Evaluation (Thermal Analysis) ........................ 557 Minimum — Time Evaluation (Thermal Analysis) ...................................... 557 Maximum Absolute — Time or Frequency Evaluation Method ..................... 558 Maximum — Time Evaluation (Thermal Analysis) ..................................... 558 At Each Step — Time Evaluation (Thermal Analysis)................................. 559 Radius ............................................................................................... 559 Spatial Evaluation — Thermal ............................................................... 559 Dynamic Evaluation in Thermal ............................................................. 560 Phase Type......................................................................................... 561 Quantity for Measure Definition ............................................................. 561 UCS-Based Measures ........................................................................... 562 Spatial Evaluation — Structure .............................................................. 562 Time Stamp........................................................................................ 563 xxvii Table of Contents Dynamic Evaluation in Structure............................................................ 563 Meshes ................................................................................................. 564 Native Mode Meshes ............................................................................ 564 FEM Meshes........................................................................................ 591 Elements with Approximated Linear Edges .............................................. 636 Example: Orientation and Tolerance Settings .......................................... 637 AutoGEM File Names............................................................................ 637 Design Controls ..................................................................................... 638 About Design Controls.......................................................................... 638 Design Parameters .............................................................................. 638 Shape Review ..................................................................................... 645 Shape Animate ................................................................................... 649 Guidelines for Using Relations ............................................................... 651 Example: Relations.............................................................................. 652 Design Parameters with Laminate Layup ................................................ 653 Strategy: Using Design Parameters........................................................ 653 Verifying Models .................................................................................... 654 Checking Your Model............................................................................ 654 Validity Checking................................................................................. 655 Structure and Thermal Errors................................................................ 655 Structure Errors .................................................................................. 656 Thermal Errors.................................................................................... 656 To Promote Simulation Features to Pro/ENGINEER...................................... 657 To Create a Pro/ENGINEER Parameter ...................................................... 657 Creating Analyses ..................................................................................... 658 xxviii Table of Contents About Analyses ...................................................................................... 658 Creating Analyses and Design Studies....................................................... 658 Analyses and Design Studies Dialog Box.................................................... 659 Analysis Types ....................................................................................... 659 Structural Analysis ................................................................................. 660 About Structural Analysis ..................................................................... 660 Constraint and Load Sets in Structural Analyses ...................................... 661 Static and Prestress Static Analyses ....................................................... 661 Large Deformation Static Analysis ......................................................... 665 Contact Analysis.................................................................................. 667 Modal and Prestress Modal Analyses ...................................................... 669 Buckling Analysis................................................................................. 672 Fatigue Analysis .................................................................................. 674 To Use Previous Analysis Results in a Fatigue Analysis.............................. 676 To Define the Load History for a Fatigue Analysis..................................... 676 To Select Output Options for a Structural Analysis ................................... 677 To Select Load Interval Options for Large Deformation and Contact Analyses ........................................................................................................ 677 To Set Convergence for a Structural Analysis .......................................... 677 To Select Temperature Distribution for an Analysis .................................. 678 To Use Previous Analysis Results in a Prestress Analysis ........................... 678 To Use Previous Analysis Results in a Buckling Analysis ............................ 679 To Select Mode Options for a Modal Analysis ........................................... 679 Convergence Options for Structural Analyses .......................................... 680 Previous Analysis Options for Buckling Analysis ....................................... 680 xxix Table of Contents Buckling Load Factor and Optimization Studies ........................................ 681 Previous Analysis Options for Prestress Analyses ..................................... 681 Temperature Distribution Options .......................................................... 682 Strategy: Using Contact Analysis Effectively............................................ 682 Strategy: Determining the Presence of a Non-Linear Problem .................... 683 Contact Analyses in Design Studies........................................................ 684 Plotting Grid ....................................................................................... 684 Calculate Quantities for Analysis............................................................ 685 Number of Load Intervals ..................................................................... 685 Number of Modes, All Modes in Frequency Range..................................... 686 Min Frequency, Max Frequency ............................................................. 686 Load Interval Options for Large Deformation and Contact Analyses ............ 687 Loading Types for Fatigue Analysis ........................................................ 687 Previous Analysis Options for Fatigue Analysis......................................... 688 Output Options for Structural Analyses................................................... 688 Sample Uses for Prestress and Buckling Analyses .................................... 688 Model Temperature Distribution............................................................. 689 Use Temperatures from Previous Design Study........................................ 690 Use Static Analysis Results From Previous Design Study ........................... 690 Load Scale Factor for Prestress Analyses ................................................ 691 Combine Results with Results from Previous Static Analysis ...................... 691 Units of Modal Frequency Results .......................................................... 691 Load History Options for Fatigue Analysis ............................................... 691 Spin Softening .................................................................................... 692 Mode Options for Modal and Prestress Modal Analyses.............................. 692 xxx Table of Contents Strain Measures in Large Deformation Static Analysis............................... 692 Load Types in Large Deformation Static Analysis ..................................... 693 Adjusting Cyclic Material Properties for Fatigue........................................ 694 Adjusting the Mean Stress Parameter for Fatigue..................................... 694 Adjusting the Material Confidence Level for Fatigue.................................. 695 Advanced Tuning for Fatigue Advisor ..................................................... 695 Adjusting the Biaxiality Parameter for Fatigue ......................................... 696 Guidelines for Entering Polynomial Order ................................................ 696 Strategy: Specifying Polynomial Order for a Multi-Pass Adaptive Analysis.... 697 Temperature Load Information for Static Analyses ................................... 697 Single-Pass Adaptive Convergence Method ............................................. 698 Multi-Pass Adaptive Convergence Method ............................................... 699 Convergence Quantity for Static, Prestress Static, Large Deformation, and Contact Analyses................................................................................. 699 Percent Convergence ........................................................................... 700 Convergence Method ........................................................................... 700 Polynomial Order................................................................................. 701 Convergence Quantity for Modal and Prestress Modal Analyses .................. 701 Localized Mesh Refinement ................................................................... 702 Convergence Quantity for Buckling Analyses ........................................... 703 Unconstrained..................................................................................... 703 Constrained, With Rigid Mode Search ..................................................... 704 Thermal Analysis.................................................................................... 704 About Thermal Analysis........................................................................ 704 Boundary Condition and Load Sets in Thermal Analyses............................ 705 xxxi Table of Contents Steady Thermal Analysis ...................................................................... 705 Transient Thermal Analysis ................................................................... 706 To Select Output Options for a Thermal Analysis...................................... 708 To Select Temperature Options for a Transient Thermal Analysis ............... 709 To Set Convergence for a Thermal Analysis............................................. 710 Estimated Variation ............................................................................. 710 Initial Temperature Distribution............................................................. 711 Transient Thermal Convergence Method ................................................. 711 Automatically Smooth Convections ........................................................ 712 Accuracy ............................................................................................ 712 Percent Convergence ........................................................................... 713 Convergence Quantities for Steady Thermal Analysis................................ 713 Steady Thermal Convergence Method .................................................... 713 Understanding Accuracy ....................................................................... 714 Time Range Specification...................................................................... 714 Time Range ........................................................................................ 715 User-defined Steps for Transient Thermal Analysis................................... 715 Output Intervals for Transient Thermal Analysis ...................................... 715 Temperature Options for Transient Thermal Analysis ................................ 716 Thermal Measures ............................................................................... 716 Plotting Grid ....................................................................................... 717 Local Temperatures and Local Energy Norms .......................................... 717 Local Temperatures and Local and Global Energy Norms........................... 717 Heat Flux ........................................................................................... 718 Convergence Percentage Calculation ...................................................... 718 xxxii Table of Contents Output Options for Thermal Analyses ..................................................... 718 Convergence Options for Thermal Analyses............................................. 719 Vibration Analysis .................................................................................. 719 About Vibration Analysis....................................................................... 719 Dynamic Time, Dynamic Frequency, and Dynamic Random Analyses .......... 719 Dynamic Shock Analysis ....................................................................... 724 To Create a Dynamic Shock Analysis ...................................................... 724 To Use Previous Analysis Results in a Dynamic Analysis............................ 725 To Define the Response Spectrum for a Dynamic Shock Analysis ............... 725 To Select Output Options for a Dynamic Analysis ..................................... 726 To Select Mode Options for a Dynamic Analysis ....................................... 727 To Select Load Functions for a Dynamic Analysis ..................................... 728 To Specify Base Excitation for a Dynamic Analysis ................................... 728 Results Output Intervals....................................................................... 728 Response Spectrum Options for Dynamic Shock Analysis .......................... 729 Use Modes From Previous Design Study ................................................. 730 Previous Analysis Options for Dynamic Analysis ....................................... 730 Modes Included ................................................................................... 731 Frequency Range ................................................................................ 731 For Individual Modes............................................................................ 731 Function of Frequency .......................................................................... 732 Damping Coefficient (%) ...................................................................... 732 Calculate Quantities and Factors for Vibration Analysis ............................. 732 User-defined Steps .............................................................................. 733 Output Options for Dynamic Analyses .................................................... 733 xxxiii Table of Contents Mode Options for Dynamic Analyses....................................................... 734 Mass Participation Factor Results ........................................................... 734 Full Results......................................................................................... 734 Base Excitation ................................................................................... 734 Sum Load Sets.................................................................................... 735 Load Set Functions .............................................................................. 735 Time Range ........................................................................................ 736 Direction of Base Excitation .................................................................. 736 FEM Analysis ......................................................................................... 737 About FEM Analysis ............................................................................. 737 Using the FEM Analysis Command in FEM Mode ....................................... 737 Defining a FEM Analysis........................................................................ 738 Defining a Modal FEM Analysis .............................................................. 738 To Create an Output File ...................................................................... 739 To Review the Mesh............................................................................. 740 To Solve a FEM Model Online or in the Background .................................. 740 To Create a Modal FEM Analysis ............................................................ 741 Suppressing Loads, Constraints, and Boundary Conditions ........................ 741 NASTRAN Templates ............................................................................ 741 Fixing Parabolic Elements ..................................................................... 742 Storing and Retrieving FEA Results ........................................................ 742 Using Solver Results in the Postprocessor ............................................... 743 Output Formats................................................................................... 743 FEM Neutral Format ............................................................................. 744 MSC/NASTRAN.................................................................................... 744 xxxiv Table of Contents ANSYS ............................................................................................... 745 To Create a FEM Analysis ..................................................................... 746 Analysis and Design Study Workflow......................................................... 747 Strategy: Identifying and Resolving Potential Trouble Spots in a Model.......... 748 About Creating and Running Analyses and Design Studies ........................... 749 Creating Design Studies............................................................................. 749 About Design Studies ............................................................................. 749 Strategies for Running a Standard Design Study ........................................ 750 Design Study Files.................................................................................. 750 Creating Design Studies .......................................................................... 751 Analyses and Design Studies Dialog Box................................................. 751 Design Study Definition Dialog Box ........................................................ 752 Standard Study for Structure and Thermal.............................................. 752 Global Sensitivity Study for Structure and Thermal .................................. 754 Local Sensitivity Study for Structure and Thermal .................................... 757 Optimization Study for Structure and Thermal ......................................... 759 To Save an Optimized Shape ................................................................... 765 To Create a Design Study........................................................................ 765 To Define an Optimization Study Limit ...................................................... 766 To Define an Optimization Study Goal ....................................................... 766 To Run a Regeneration Analysis ............................................................... 767 Local Sensitivity Dialog Box ..................................................................... 768 Strategy: Viewing Optimization Results ..................................................... 768 Strategy: Running a Global Sensitivity Study ............................................. 768 Varying a Single Design Parameter in a Global Sensitivity Study................... 769 xxxv Table of Contents Using Global Sensitivity Studies Effectively ................................................ 769 Track.................................................................................................... 770 Redefine the Design Study ...................................................................... 771 Strategy: Optimizing a Model................................................................... 771 Strategy: Defining Optimization Studies .................................................... 771 Strategy: After You Run an Optimization Study .......................................... 772 Selecting Load Sets and Modes for Optimization Studies.............................. 773 Using Measures More than Once for Optimization Limits .............................. 773 Strategy: Preparing for Optimization Studies ............................................. 774 Running Solvers ....................................................................................... 774 Native Mode Solvers ............................................................................... 774 Running Analyses and Design Studies .................................................... 774 Before You Run an Analysis or Design Study ........................................... 775 Analyses and Design Studies Dialog Box................................................. 776 To Start an Analysis or Design Study Run ............................................... 776 Setting Up a Run ................................................................................. 777 Start.................................................................................................. 780 Restart .............................................................................................. 782 Batch................................................................................................. 784 Stop .................................................................................................. 785 Monitoring an Analysis or Design Study Run............................................ 785 Time and Disk Usage Information .......................................................... 788 Diagnose............................................................................................ 789 Troubleshoot Run Problems .................................................................. 789 mecbatch ........................................................................................... 791 xxxvi Table of Contents msengine ........................................................................................... 792 FEM Solvers .......................................................................................... 795 About Running FEM Analyses and Generating Output Decks ...................... 795 Solving a Model Using an FEA Program................................................... 796 Selecting a Solver ............................................................................... 797 FEM Analysis Types ............................................................................. 797 Element Shape.................................................................................... 798 Determining a Run Method ................................................................... 799 To Display Run Errors ............................................................................. 802 To Select the Iterative Solver .................................................................. 803 Guidelines for Allocating RAM for Solver and Element Data .......................... 803 Detailed Summary ................................................................................. 804 Restrictions When Specifying Multiple Working Directories ........................... 804 Managing Memory and Swap Space .......................................................... 805 Guidelines for Managing Disk Space Resources........................................... 806 Managing Performance ........................................................................... 806 Modifying Analyses and Design Studies ..................................................... 807 Analyses and Design Studies Toolbar ........................................................ 807 Strategy: Improving Convergence ............................................................ 807 -massnorm ........................................................................................... 808 BLF Convergence ................................................................................... 808 –iter n .................................................................................................. 808 –i input_dir ........................................................................................... 808 Optimization Studies .............................................................................. 808 Measure Convergence............................................................................. 809 xxxvii Table of Contents Local Sensitivity Studies.......................................................................... 809 Local Disp/Energy Index, Local Temp/Energy Index .................................... 809 Global RMS Stress Index ......................................................................... 809 Global Sensitivity Studies ........................................................................ 810 Global Energy Index ............................................................................... 810 Convergence Indicators .......................................................................... 810 Strategy: Fixing Convergence Problems .................................................... 810 Frequency Convergence .......................................................................... 811 Temperature Distribution ........................................................................ 811 Error Detection in Optimization Studies ..................................................... 811 –solram ram_size................................................................................... 811 Inconsistent Shell Normals ...................................................................... 812 –sturm option........................................................................................ 812 Error Resolution ..................................................................................... 812 Convergence Measures ........................................................................... 813 Boundary Faces ..................................................................................... 813 Boundary Edges..................................................................................... 813 Allowable Errors..................................................................................... 813 Standard Design Study with Parameters.................................................... 814 Standard Studies: Static, Large Deformation Static, Contact, Prestress Static, Modal, Prestress Modal, Buckling, Steady-State Thermal, and Transient Thermal Analyses ............................................................................................... 814 Standard Studies: Dynamic Time, Frequency, and Random Analyses ............ 815 Standard Studies, Dynamic Shock Analyses ............................................... 815 –T........................................................................................................ 815 Matching Parameters .............................................................................. 815 xxxviii Table of Contents –p password.......................................................................................... 815 -gdp ..................................................................................................... 816 –elram ram_size .................................................................................... 816 –bsram ram_size ................................................................................... 817 –ascii ................................................................................................... 817 Sample mecbatch File ............................................................................. 817 Strategy: If Solver RAM Is Too Low .......................................................... 818 Strategy: If Solver RAM Is Too High ......................................................... 818 Select the Solver.................................................................................... 819 Guidelines for Allocating Swap Space ........................................................ 819 Guidelines for Setting Solram .................................................................. 820 mech_extopt.out File Format ................................................................... 821 –w working_dir1:working_dir2:................................................................ 821 Strategy: Running the Engine with Parallel Processing................................. 822 mech_extopt.in File Format ..................................................................... 823 After P-Loop Pass ................................................................................... 823 Maximum Number of Iterations................................................................ 824 Reviewing Results ..................................................................................... 824 Results for Native Mode .......................................................................... 824 About Results ..................................................................................... 824 Working with the Results User Interface ................................................. 825 Results User Interface Menu Bar............................................................ 826 Results User Interface Toolbar .............................................................. 827 Basic Functions for the Results User Interface ......................................... 828 Defining and Viewing Results ................................................................ 828 xxxix Table of Contents Evaluating Results ............................................................................... 835 Loading Result Windows ....................................................................... 836 To Load a Result Window...................................................................... 836 Saving Results .................................................................................... 837 Generating Reports.............................................................................. 838 To Define an Acceleration Quantity ........................................................ 839 To Animate a Results Display ................................................................ 839 To Specify a Result Window Quantity ..................................................... 839 To Specify Result Window Display Options .............................................. 840 To Define a Displacement Quantity ........................................................ 840 To Define a Deformed Results Display .................................................... 840 To Define a Contour Results Display....................................................... 841 To Define a Contact Pressure Quantity ................................................... 841 To Define a Beam Resultant Quantity ..................................................... 841 To Define a Rotation Quantity ............................................................... 842 To Define a Rotation Velocity Quantity ................................................... 842 To Define a Rotation Acceleration Quantity ............................................. 842 To Define a Shear & Moment Quantity.................................................... 843 To Define a Strain Quantity................................................................... 843 To Define a Results Display Location ...................................................... 843 To Define a Vectors Results Display ....................................................... 844 To Define a Flux or Temp Gradient Quantity............................................ 844 To Define a Reactions at Point Constraints Quantity ................................. 844 To Define a Reaction Quantity ............................................................... 845 To Define a Model Results Display.......................................................... 845 xl Table of Contents To Define a Measure Quantity ............................................................... 845 To Define a Graph Results Display ......................................................... 846 To Define a Fringe Results Display ......................................................... 846 To Define a Shell Resultant Quantity ...................................................... 846 To Define a Failure Index Quantity......................................................... 847 To Define a Velocity Quantity ................................................................ 847 To Define a Thermal Strain Quantity ...................................................... 847 To Define a Thermal Strain Energy Quantity............................................ 847 To Define a Temperature Quantity ......................................................... 848 To Define a Strain Energy Quantity ........................................................ 848 To Define a Stress Quantity .................................................................. 848 To Define a Fatigue Quantity................................................................. 848 Components for Fatigue ....................................................................... 849 Reviewing the Results .......................................................................... 850 Component and Layer Visibility in Results ............................................... 851 Results Relative to Ply Orientation ......................................................... 851 Component......................................................................................... 852 Recovery Points for Beam Results .......................................................... 852 Stress Notes ....................................................................................... 853 Example: Contour Plot ......................................................................... 854 Quantity Notes for Modal and Dynamic Analyses...................................... 854 Top and Bottom Shell Location .............................................................. 855 Maximum and Minimum Shell Values ..................................................... 855 Results Relative to Material Orientation .................................................. 855 Reaction Results Reporting ................................................................... 856 xli Table of Contents Velocity Results Quantity ...................................................................... 856 Thermal Strain Results Quantity ............................................................ 856 Vectors Display Type ........................................................................... 857 Animating Your Results Display ............................................................. 858 Insert Result Windows From Template Dialog Box.................................... 859 Tips for Fringe Displays ........................................................................ 859 Example: Max Principal Stress Vector Plot............................................... 860 Components for Beam Bending, Tension, Torsion, and Total...................... 860 Contour Results Display ....................................................................... 861 Strategy: Using Convergence Graphs to Review Results ........................... 861 Strategy: Interpreting Beam Resultant Forces and Moments ..................... 863 Types of Measure Results Graphs .......................................................... 865 Results Relative to Coordinate Systems .................................................. 866 Results Relative to Beam Orientation ..................................................... 866 Example: Vector Plot ........................................................................... 867 Example: Fringe Display....................................................................... 868 Local Sensitivity Graph Notes................................................................ 868 Deformed Results Display ..................................................................... 869 Acceleration Results Quantity................................................................ 869 Components for Acceleration, Displacement, Reaction, Rotation, Rotation Acceleration, Rotation Velocity, or Velocity.............................................. 870 Secondary Quantity Option Menu........................................................... 871 Displacement Results Quantity .............................................................. 871 Contact Pressure Results Quantity ......................................................... 872 Graph Location ................................................................................... 872 xlii Table of Contents Components for Beam Resultant ........................................................... 872 Fatigue Results Quantity ...................................................................... 873 Beam Resultant Results Quantity........................................................... 873 Shell Contribution................................................................................ 873 Relative To ......................................................................................... 874 Rotation Acceleration Results Quantity ................................................... 874 Temp Gradient Results Quantity ............................................................ 875 Thermal Strain Energy Results Quantity ................................................. 875 Temperature Results Quantity ............................................................... 876 Strain Energy Results Quantity.............................................................. 876 Shell Resultant Results Quantity ............................................................ 876 Shear & Moment Results Quantity ......................................................... 877 Rotation Velocity Results Quantity ......................................................... 877 Rotation Results Quantity ..................................................................... 878 Flux Results Quantity ........................................................................... 879 Model Display Type.............................................................................. 879 Components for Shell Resultant............................................................. 880 Components for Shear and Moment ....................................................... 880 Components for Reactions at Point Constraints........................................ 881 Components for Flux and Temp Gradient ................................................ 881 Reactions at Point Constraints Quantity .................................................. 882 Graph Display Type ............................................................................. 882 Quantity for Result Windows ................................................................. 882 Reaction Results Quantity..................................................................... 883 P-Level Results Quantity....................................................................... 884 xliii Table of Contents Components for Stress or Strain............................................................ 884 Failure Index Results Quantity .............................................................. 885 Measure Results Quantity ..................................................................... 885 Fringe Display Type ............................................................................. 886 Stress Results Quantity ........................................................................ 887 Strain Results Quantity ........................................................................ 888 How Stress Components Relate to Textbook Examples ............................. 888 Beam Contribution............................................................................... 889 Results for FEM ...................................................................................... 890 About FEM Results............................................................................... 890 Using the Postprocessor in FEM Mode..................................................... 891 Loading NASTRAN Results Database ...................................................... 891 Graphical Result Windows..................................................................... 892 FEA Parameters .................................................................................. 905 Analysis Statistics................................................................................ 907 Hard Point Reports .............................................................................. 908 Supported FEA Solvers......................................................................... 910 To Generate an Edge Graph .................................................................. 910 To Display or Output Parameters ........................................................... 911 To Delete Parameters .......................................................................... 911 Shell Side........................................................................................... 912 Outputting FEM Analysis Statistics ......................................................... 912 Output of Statistics and Reports for Thermal Analyses.............................. 913 Output of Statistics and Reports for Structural or Modal Analyses .............. 914 Limitations of Averaging in Results ........................................................ 914 xliv Table of Contents Graphing Statistics .............................................................................. 914 FEA Parameter Types ........................................................................... 915 Outputting Hard Point Reports............................................................... 915 Creating Statistics, Parameters, or Reports from Shell Elements ................ 916 Defining Parameters Based on Results.................................................... 916 Generating Point Data .......................................................................... 916 To Annotate a Result Window .................................................................. 917 To Save a Result Window ........................................................................ 918 To Edit a Result Window.......................................................................... 918 To Format a Fringe, Contour, Vector, Model, or Animation Result Window...... 918 To Customize Annotation Styles ............................................................... 919 Adjusting Color Scale for Fringe, Contour, and Vector Legends ..................... 919 Controlling Animations ............................................................................ 920 Adjusting Fringe, Contour, and Vector Legends .......................................... 920 Examining Model Interiors for Fringe and Contour Plots ............................... 921 Example: Comparing Animation Stages for the Same Model......................... 922 Example: Comparing Mode Animations for the Same Model ......................... 923 Determining the Minimum and Maximum Locations for a Quantity ................ 924 Modifying and Deleting Cutting and Capping Surfaces ................................. 924 Copying and Deleting Result Windows....................................................... 925 Clearing Query Tags from a Result Window................................................ 925 Comparing Animations ............................................................................ 925 Displaying Element IDs, Node IDs, and Result Values (FEM mode)................ 926 Note Style Dialog Box ............................................................................. 926 Reviewing and Altering Result Windows..................................................... 927 xlv Table of Contents Format Result Window Dialog Box ............................................................ 928 Querying Quantities for Fringe Plots and Linearized Stress Analyses.............. 928 Displaying Result Windows ...................................................................... 929 Saved Views.......................................................................................... 929 Before You Use the Results Command....................................................... 929 Comparing Results ................................................................................. 930 Shading Your Model................................................................................ 930 Probing Graphs ...................................................................................... 931 Probing Fringe, Contour, and Vector Plots.................................................. 932 Using Maximum and Minimum Legend Values to Get More Details................. 932 Orientation Dialog Box ............................................................................ 933 Controlling Result Window Appearance...................................................... 934 How Mechanica Handles Your Working Model ............................................. 935 To Modify a Cutting Surface..................................................................... 935 To Create a Cutting Surface..................................................................... 936 To Create a Capping Surface ................................................................... 936 To Set Titles .......................................................................................... 937 To Untie Multiple Result Windows ............................................................. 937 To Tie Multiple Result Windows ................................................................ 937 To Set Labels......................................................................................... 938 To Query for Linearized Stress ................................................................. 938 To Generate a Report for Linearized Stress ................................................ 939 To Export a File in VRML ......................................................................... 939 To Tie Multiple Graph Result Windows, Procedure 1 .................................... 939 To Modify a Capping Surface.................................................................... 939 xlvi Table of Contents To Segment a Graph .............................................................................. 940 To Export a File as an MPEG .................................................................... 940 To Export a File in HTML ......................................................................... 941 To Edit the Legend ................................................................................. 941 To Create an Excel Graph Report.............................................................. 942 To Tie Multiple Graph Result Windows, Procedure 2 .................................... 942 Strategy: Displaying Graphs with Logarithmic Scales .................................. 942 Customizing Graph Display Settings ......................................................... 943 Managing Graphs ................................................................................... 944 Querying for Linearized Stress ................................................................. 945 Graph Report......................................................................................... 945 Dynamic Query ...................................................................................... 946 Relabel Contour ..................................................................................... 946 Results Surface Definition Dialog Box........................................................ 946 Titles .................................................................................................... 947 Printing Result Windows.......................................................................... 947 Labels .................................................................................................. 948 Contour Labels ...................................................................................... 948 Overlay................................................................................................. 949 Excel .................................................................................................... 949 HTML Report ......................................................................................... 950 Tie Multiple Graph Result Windows ........................................................... 950 Linearized Stress Report ......................................................................... 951 Generate Report for Linearized Stress Results ............................................ 952 Defining Reference Planes for Cutting or Capping Surfaces .......................... 952 xlvii Table of Contents Dynamic Cutting and Capping Surface Displays .......................................... 952 Defining Cutting or Capping Surface Depth ................................................ 953 Defining Cutting or Capping Surface References ......................................... 953 MPEG Export Dialog Box.......................................................................... 954 Log Scale .............................................................................................. 955 Linearized Stress Value Calculation........................................................... 955 Component for Linearized Stress Results ................................................... 956 Graphtool Window.................................................................................. 956 X Axis and Y Axis Tabs............................................................................ 957 Segmenting a Graph............................................................................... 958 Legend Value......................................................................................... 958 Redistribute Levels ................................................................................. 959 Direct VRML .......................................................................................... 959 Tie — Contour, Fringe, Graph, or Vectors Result Windows ........................... 959 MPEG ................................................................................................... 960 Default ................................................................................................. 960 Graphic Size .......................................................................................... 960 View Menu on Results Window Toolbar...................................................... 961 Graph Display Tab.................................................................................. 961 Orientation Dialog Box ............................................................................ 961 File Menu on Results Window Toolbar........................................................ 962 Export VRML Dialog Box.......................................................................... 962 Export HTML Setup Dialog Box................................................................. 962 Export HTML Dialog Box .......................................................................... 962 Guidelines for Changing Legend Values ..................................................... 963 xlviii Table of Contents Alignment ............................................................................................. 963 Data Series Tab ..................................................................................... 963 Untie — Contour, Fringe, Graph, or Vectors Result Windows ........................ 964 Tie Graph Windows ................................................................................ 964 General Guidelines for Tying Result Windows ............................................. 965 Guidelines for Tying Graphs..................................................................... 965 Spin ..................................................................................................... 965 Refit ..................................................................................................... 966 Paper ................................................................................................... 966 Pan ...................................................................................................... 967 Output Format ....................................................................................... 967 Common Facilities..................................................................................... 968 Working With Normals ............................................................................ 968 Surface Normals.................................................................................. 968 Specifying Y Direction for Beams ........................................................... 969 Shell Normals ..................................................................................... 970 Working with Functions ........................................................................... 970 Functions for Native Mode .................................................................... 970 Functions for FEM Mode........................................................................ 976 To Create a Table Function ................................................................... 979 To Create a Symbolic Function .............................................................. 980 Use of Function Definitions ................................................................... 980 Additional Information ............................................................................... 982 Background Information.......................................................................... 982 Long-Term Limitations ......................................................................... 982 xlix Table of Contents Icons Used in Mechanica ...................................................................... 984 Icons Common to Structure and Thermal................................................ 984 Icons Specific to Structure .................................................................... 987 Icons Specific to Thermal ..................................................................... 991 Bibliography ....................................................................................... 992 The Database ........................................................................................ 995 Database Considerations ...................................................................... 995 Native Mode Files ................................................................................ 995 Using Pro/ENGINEER File Commands ..................................................... 998 FEM Database Considerations ............................................................... 998 Support for Pro/INTRALINK and Windchill ............................................. 1000 Files Created by Mechanica ................................................................. 1003 Engine Files ...................................................................................... 1003 Library Files...................................................................................... 1009 Results Files ..................................................................................... 1010 AutoGEM Files................................................................................... 1010 FEM Mode Files ................................................................................. 1011 Miscellaneous Files ............................................................................ 1012 Information Transfer ............................................................................ 1013 Transferring Entities From Integrated Mode to Independent Mode ............ 1013 Transferring Geometry ....................................................................... 1013 Geometry Transfer Limitations ............................................................ 1016 Transferring Loads and Constraints ...................................................... 1016 Import Considerations........................................................................ 1017 What Does Not Transfer ..................................................................... 1018 l Table of Contents FEM Neutral Format File ..................................................................... 1019 About the FEM Neutral Format ............................................................ 1019 Defining an Object............................................................................. 1020 Sections of a FEM Neutral Format File .................................................. 1026 Specialized Information......................................................................... 1052 Understanding Fatigue Analysis ........................................................... 1052 Shell Property Equations .................................................................... 1071 Overview.......................................................................................... 1071 Formulae for Calculating Shell Properties .............................................. 1072 List of Symbols ................................................................................. 1079 Bibliography ..................................................................................... 1080 Verification Guide .............................................................................. 1081 Glossary for Mechanica............................................................................... 1264 Index ....................................................................................................... 1297 li Structural and Thermal Simulation Help About Structural and Thermal Simulation Structural and Thermal Simulation is a multi-discipline CAE (Computer Aided Engineering) tool that enables you to simulate the physical behavior of a model and to understand and improve the mechanical performance of your design. You can directly calculate stresses, deflections, frequencies, heat transfer paths, and other factors, showing you how your model will behave in a test lab or in the real world. The Structural and Thermal Simulation product line features two modules—Structure and Thermal—each of which solves for a different family of mechanical behaviors. Structure focuses on the structural integrity of your model, while Thermal evaluates heat-transfer characteristics. Structural and Thermal Simulation is available in two basic modes—integrated mode and independent mode. In integrated mode, you perform all Structural and Thermal Simulation functions within Pro/ENGINEER. This version of the product offers the convenience and power of Pro/ENGINEER's parametric feature-creation technology coupled with the full range of Structural and Thermal Simulation's solution software. In independent mode, you work in a separate user interface, developing your model from imported geometry or geometry you create using Structural and Thermal Simulation's geometry-creation facilities. Note: Beyond providing a general description of independent mode, this online help system covers Structural and Thermal Simulation's integrated mode only. To access the independent mode online help system, start independent mode and access online help from the independent mode user interface. Structural and Thermal Simulation's broad range of analytical solutions, excellent modeling capabilities, and flexibility make it a powerful tool for meeting your simulation needs. As you begin to work with Structural and Thermal Simulation, take a few moments to familiarize yourself with the basics of this software package. Also, spend a few minutes reviewing updates and special considerations for this release. For the body of this help system, you will see Structural and Thermal Simulation referred to as Mechanica. You will also see this terminology in a number of commands in the product user interface. Updates for Mechanica Wildfire 2.0 Read this document before using Mechanica Wildfire 2.0. It contains updated information that does not appear anywhere else in the documentation. It also contains descriptions of limitations you may encounter. 1 Structural and Thermal Simulation - Help Topic Collection This document contains discussions of: • • • Compatibility Issues Functionality Limitations Platform-Specific Limitations Compatibility Issues • • • • • Mechanica Wildfire 2.0 is not compatible with Pro/ENGINEER Wildfire, or lower. To run Mechanica Wildfire 2.0, upgrade to Pro/ENGINEER Wildfire 2.0. Mechanica Wildfire 2.0 supports Pro/INTRALINK, version 3.3. Mechanica Wildfire 2.0 supports Unigraphics NX 2.0. Mechanica Wildfire 2.0 supports CATIA 4.2.4 release 2. Mechanica's FEM mode no longer supports the Mold product. Functionality Limitations • In assemblies where the points, edges, or surfaces of individual parts overlap to form the assembly, Structure and Thermal do not support beams, shells, and springs placed on the overlapping geometry. This limitation is specific to native mode and does not occur in FEM mode. The Mechanica Motion Help for Integrated mode is available at <proe_load_point>/html/usascii/proe/motion/start.htm in your Pro/ENGINEER installation. You can use the browsers Mozilla 1.4 or IE 6.0 SP1 and later browsers to view the Motion Integrated Help. • Platform-Specific Limitations The following discussion covers limitations specific to a given platform or specific to localized versions of the product, and includes: • • Mechanica Wildfire 2.0 Installation Issues HP Mechanica Wildfire Installation Issues • • Do not install Mechanica Wildfire 2.0 over an existing Wildfire installation. The showlic utility may not show the following Wildfire 2.0 licenses: Fatigue UI, Fatigue Engine, and Independent Mechanica UI. However, the licenses may still be available when using the product. HP For the HP-UX operating system, the maxdsize parameter fixes a ceiling on the amount of swap space any single process can utilize. If this parameter is set too low, the Structure engine may terminate when solving large models due to insufficient swap space. In this case, the system displays the error 2 Structural and Thermal Simulation message "An engine database error has occurred. Please check available disk and swap space." If the available swap space appears more than adequate, the maxdsize parameter may be limiting the amount of the available swap space that Mechanica can utilize. You can use the HP-UX utility sam to check the current value of this parameter. You need to reconfigure the HP-UX kernel to change the value for this parameter to a minimum value of 500 MB. Getting Started with Mechanica Getting Started You start Mechanica by selecting the Application>Mechanica command from the Pro/ENGINEER menu bar. The Mechanica command is available for most models you develop in Pro/ENGINEER, but is inactive if Mechanica does not support the model type or some of the model features. When you select this command, Mechanica displays the Model Type dialog box. You use this dialog box to select the Mechanica product that you want to work with and as a starting point for your simulation modeling session. As you begin to use Mechanica, you will want to understand some basics of Mechanica operation, how to use Mechanica efficiently, and how Mechanica and Pro/ENGINEER interrelate. Review these topics to learn about the fundamentals of the Mechanica product line and software usage: • • • • • • • Mechanica products Mechanica workflow operating modes planning and modeling considerations working with the user interface configuration options getting help for Mechanica Configuration File Options Mechanica stores several internal settings in configuration files associated with your session. You use the config.pro file to store configuration options. Configuration options are an important tool that can help you make your Mechanica sessions more efficient by ensuring that meshing and solver settings are consistent, your display is the same from session to session, and so forth. See the following topics for more information about these files and the options you can set in them: • • config.pro Overview config.pro Options 3 Structural and Thermal Simulation - Help Topic Collection config.pro Overview The settings in config.pro control various aspects of your Mechanica session. This discussion covers all config.pro options supported for integrated mode. Here are some guidelines to consider when creating or amending a config.pro file: • • • In general, configuration file options and values are not case sensitive. In both UNIX and Windows, the actual file names on disk must use lowercase characters only. In both UNIX and Windows, directory names can contain a mix of uppercase and lowercase characters. However, if Mechanica encounters two or more directories in the same path that have the same parent and the same name except for a different mix of uppercase and lowercase characters, it accesses only the directory with the earliest uppercase characters (since their ASCII values are lower.) This is true if you enter the full path with correct case sensitivity. For example, if it encounters directories named aBc, ABc, and Abc, it only looks in/through directory ABc. A config.pro line should not exceed 80 characters. You cannot continue a search path or mapkey on a second line. In Windows, you should specify the drive at the beginning of the path, so as to avoid problems if you change your working directory to another drive. You can set these options from the Tools>Options menu, or you can manually edit your config.pro file using a text editor. • • • config.pro Options Here are the config.pro option categories available for Mechanica: • • • • • • • • Mechanica Unit Settings Option Simulation Display Options General Modeling Options FEM Mode Modeling, Meshing, and Output Options Fatigue Options Run Options Result Display Options Miscellaneous Options Options in each category begin with the keyword or attribute name in boldface type, followed by a brief paragraph describing the option and a list of valid value types. The options in each category appear in alphabetical order. Mechanica Unit Settings Option Use this option to control the default units setting for your model. PRO_UNIT_SYS Customizes your units settings by controlling the default principal system of units for your model. 4 Structural and Thermal Simulation o PROE_DEF — • length = in • mass = lbm • time = sec • temperature = F In this system, the unit of force is in x lbm/sec (inch lbm second), which is not a common unit. o o o o o MKS — meter kilogram second CGS — centimeter gram second mmNs — millimeter Newton second FPS — foot pound second IPS — inch pound second Simulation Display Options Use these options to control which icons are on by default for your session. For most of the following options, the settings are TRUE or FALSE. SIM_DISPLAY_AGEM_CONTROLS Toggles display of AutoGEM controls. SIM_DISPLAY_ARROW_SCALE Toggles automatic arrow scaling. SIM_DISPLAY_ARROW_TAIL_TOUCHING Toggles display of load and reaction force arrows to have tails or heads touching. SIM_DISPLAY_BEAM_RELEASES Toggles display of beam release icons. SIM_DISPLAY_BEAM_SECTIONS Toggles display of beam section icons. SIM_DISPLAY_BEAMS Toggles display of beam icons. SIM_DISPLAY_CONTACT_REGIONS Toggles display of contact region icons. 5 Structural and Thermal Simulation - Help Topic Collection SIM_DISPLAY_FASTENERS Toggles display of fastener icons. SIM_DISPLAY_GAPS Toggles display of gap icons. SIM_DISPLAY_IN_SPIN Toggles display of icons when a model is spinning. SIM_DISPLAY_INTERFACES Toggles display of interface icons. SIM_DISPLAY_LOAD_COLORS Toggles display of individual colors. SIM_DISPLAY_LOAD_DISTRIBUTION Toggles display of distributed load vectors over entire entity. SIM_DISPLAY_LOAD_ICONS Toggles display of load icons. SIM_DISPLAY_LOAD_VALUE Toggles display of load value tags. SIM_DISPLAY_MASSES Toggles display of mass icons. SIM_DISPLAY_MATL_ASSIGNEMNTS Toggles display of material assignment icons. SIM_DISPLAY_MEASURES Toggles display of Simulation Measure icons. SIM_DISPLAY_MESH_AND_MODEL Toggles display of geometry and mesh models. 6 Structural and Thermal Simulation SIM_DISPLAY_MESH_CONTROLS Toggles display of Mesh Control icons in FEM mode. SIM_DISPLAY_MESH_ENTITIES Toggles display of all mesh entities. SIM_DISPLAY_MESH_MODE Determines the initial state of the mesh display mode. You can set the initial state so that it displays your mesh as wireframe, hidden line, visible line (no hidden lines), or shaded. You can also set the initial state to display the geometry only. o o o o o NO_MESH WIREFRAME (default) HIDDEN NOHIDDEN SHADING SIM_DISPLAY_MESH_QUALITY Specifies the display refinement for mesh viewing. o o o COARSE (default) FINE MEDIUM SIM_DISPLAY_MESH_SHELLS_THICK Determines whether Mechanica displays shells meshes with zero thickness or the thickness that you defined for the shell. When this option is set to no, Mechanica displays the shell mesh with a zero thickness. If you set this option to Yes, Mechanica displays the shell mesh using the actual thickness. o o NO (default) YES SIM_DISPLAY_MESH_SHRINK_ELEMS Specifies the size of displayed mesh elements. Enter a value between 0 and 100. If you do not want Mechanica to shrink the elements, you can use the default value, which is 0. Note that, for complex models that have very high element counts, shrinking the elements can degrade performance. SIM_DISPLAY_NAMES Toggles display of icon name tags. 7 Structural and Thermal Simulation - Help Topic Collection SIM_DISPLAY_RIGID_CONNECTIONS Toggles display of rigid connection icons. SIM_DISPLAY_RIGID_DOF Toggles display of DOF icons for rigid links. SIM_DISPLAY_RIGID_LINKS Toggles display of rigid link icons. SIM_DISPLAY_SHELLS Toggles shell boundary highlighting. SIM_DISPLAY_SPOT_WELDS Toggles display of spot weld icons. SIM_DISPLAY_SPRINGS Toggles display of spring icons. SIM_DISPLAY_STRUCT_CONSTRAINTS Toggles display of all Structure constraint icons. SIM_DISPLAY_STRUCT_LOADS Toggles display of all Structure load icons. SIM_DISPLAY_THERM_BCS Toggles display of Thermal constraint icons. SIM_DISPLAY_THERM_LOADS Toggles display of Thermal load icons. SIM_DISPLAY_WEIGHTED_DOF Toggle display of DOF icons for weighted links. SIM_DISPLAY_WEIGHTED_LINKS Toggles display of weighted link icons. 8 Structural and Thermal Simulation SIM_DISPLAY_WELDS Toggles display of weld icons. General Modeling Options Use these options to control various aspects of model definition and handling. SIM_ASM_MODELING For assembly models with shells defined as midsurfaces, determines whether Mechanica automatically creates links to connect midsurfaces of mated assembly components. If you set this option to "yes," Mechanica automatically creates these links, and you do not need to manually create welds, beams, or rigid connections to simulate mated connections. When you set this option to "no," Mechanica does not create links. In this case, you must manually create idealizations to simulate the behavior of the mated components. o o YES (default) NO SIM_BEAMSECTION_PATH Specifies the path for the beam sections directory, which contains the beam section library files. You must use the full path. SIMULATION_PRODUCT Specifies the product that you want to use as the default when you enter Mechanica. If you set this option to "prompt," the Model Type dialog box appears whenever you enter Mechanica with a new model. This behavior persists until you save your model while working in a Mechanica product. After the save occurs, Mechanica assumes that you will continue working in the selected product and no longer displays the Model Type dialog box upon entry. However, if you set this option to one of the product types, the software assumes that all models you bring into Mechanica are 3D, will use the specified product type, and, unless you specify otherwise through the SIMULATION_FEM_MODE config.pro option, will use native mode. In this case, Mechanica does not display the Model Type dialog box on entry. It simply applies the appropriate assumptions. If you want to use a different product, mode, or model type, you need to select the Edit>Mechanica Model Type command after you enter Mechanica. o o o PROMPT (default) STRUCTURE THERMAL 9 Structural and Thermal Simulation - Help Topic Collection FEM Mode Modeling, Meshing, and Output Options Use these options to control a variety of settings in FEM mode. FEM_ALLOW_NAMED_MESH_FILES Determines whether Mechanica prompts you to enter a name of a mesh file when saving a mesh, and to select a mesh file when loading a mesh. When this option is set to "no," Mechanica automatically assigns the name of model_name.fmp(a) to the mesh file when you use the File>Save FEM Mesh command, and automatically retrieves the mesh from the model_name.fmp(a) file when you use the File>Open FEM Mesh command. If you set this option to "yes," Mechanica adds the Open Named FEM Mesh and Save Named FEM Mesh commands to the File menu. When you click one of these commands, Mechanica prompts you to either select the mesh file to load, or to enter the name for the mesh file to store. o o NO (default) YES FEM_ANSYS_ANNOTATIONS Enables Mechanica to output notes as ANSYS annotations. o o NO (default) YES FEM_ANSYS_GROUPING Determines your ability to group ANSYS commands. When you set this option to "yes," you can use ANSYS CM commands for grouping nodes and elements on a part-by-part basis. Group names must be shorter than 8 characters. If the component name is longer than 8 characters, the software generates a default name. A part in part mode is not a group because you can select its elements and nodes. An element or a node may be part of more than one group. An element defined on a feature mentioned in a layer appears in the layer group and in the parent group. Bar elements connecting two assembly members do not belong to any group. o o NO (default) YES 10 Structural and Thermal Simulation FEM_ASP_RATIO Sets the value against which FEM mode compares the aspect ratios of the elements it creates. The value type is numeric and the default value is 7. FEM_DEFAULT_SOLVER Specifies the path to one of the solvers. o o ANSYS (default) MSC/NASTRAN FEM_DIST_INDEX Sets the value against which FEM mode compares the distortion indices of the elements it creates. The value type is numeric and the default value is 0.4. FEM_EDGE_ANGLE Sets the angle between two adjacent element edges. Enter a value between 0 and 90. The value type is numeric and the default value is 30. FEM_IGNORE_UNPAIRED Determines whether Mechanica notifies you of unpaired surfaces when you test shell compression. If you set this option to "no," Mechanica alerts you when it encounters unpaired surfaces during a compression test. In this case, the software shows you the entire model and highlights the unpaired surfaces. If you set this option to "yes," Mechanica does not notify you of unpaired surfaces. Instead, it displays your model without the unpaired surfaces. o o NO (default) YES FEM_MESH_OPERATIONS Activates the OPERATIONS menu, which enables you to perform specialized operations on NASTRAN files and the finite element mesh for NASTRAN. When you set this option to "yes," the Operations command appears on the Mesh menu. If you set the option to "no," the Operations command does not appear. o o NO (default) YES FEM_MESH_PRESERVE Determines whether Mechanica should automatically store the mesh in a model_name.fmp(a) file. The storage location is the current directory, and 11 Structural and Thermal Simulation - Help Topic Collection Mechanica overwrites any existing model_name.fmp(a) file in that directory without warning. If you set this option to "yes," Mechanica assumes that you want to use retained meshes rather than transient meshes. The use of retained meshes has a number of implications that affect how FEM mode behaves, the assembly meshing methods you can use, and so forth. To learn more, see Transient and Retained Meshes. With FEM_MESH_PRESERVE set to "yes," the software automatically retrieves the mesh from the model_name.fmp(a) file when you reopen the model in Structure or Thermal for FEM mode, provided the model has not changed. If the model has changed, a warning message appears. o o NO (default) YES FEM_SOLID_SHELL_AUTO_CONSTRAINT Determines whether Mechanica constrains rotation for shell nodes. The default is "no," Mechanica does not create rotational constraints for the nodes of solid elements that are connected to adjacent shell elements. In this case, you are responsible for ensuring that the nodes at the interface are not underconstrained. When you set this option to "yes," Mechanica adds rotational constraints to shell nodes at the interface between shell and solid elements at the shell node. These additional constraints prevent unwanted degrees of freedom (DOFs) in shell elements at the interface. Unwanted DOFs occur because the solid elements typically have 3 translational DOFs while shells have 3 translational DOFs and 3 rotational DOFs. Mechanica also freezes the rotational DOFs, creating a more consistent interface between the shells and solids. You can also set this option such that Mechanica asks you whether you want automatic constraints or plan to constrain the nodes yourself. o o o NO (default) YES ASK FEM_MID_RATIO Sets the value against which FEM mode compares the mid ratios of the elements it creates. The value type is numeric and the default value is 0.1. 12 Structural and Thermal Simulation FEM_NEUTRAL_VERSION Specifies the version number of the FEM neutral file. o o o 1 2 3 (default) FEM_REMOVE_UNOPPOSED Defines the default state of the UseUnopposed toggle. The UseUnopposed toggle determines whether Mechanica will keep or ignore unopposed surfaces during compression. If you set this option to "yes," the system ignores unopposed surfaces when meshing the model; the system also deselects the UseUnopposed toggle. When you set this option to "no," the system uses the unopposed surfaces in the shell model. o o NO (default) YES FEM_SKEW_ANGLE Sets the maximum acceptable default skew angle value, measured in degrees. Enter a value between 0 and 90. The value type is numeric and the default value is 45. FEM_SOLVER_TIME_LIMIT For MSC/NASTRAN solutions, this option interrupts the solver after the specified time limit. The default value is 60, and you specify values for this option in minutes. FEM_TAPER Sets the minimum acceptable default taper value. Enter a value between 0 and 1. The value type is numeric and the default value is 0.5. FEM_TWIST_ANGLE Sets the maximum acceptable default twist angle between opposing element faces. Applies to brick and wedge elements only. Enter a value between 0 and 90. FEM_WARP_ANGLE Sets the maximum acceptable default warp angle value, measured in degrees. Enter a value between 0 and 90. The value type is numeric and the default value is 10. 13 Structural and Thermal Simulation - Help Topic Collection FEM_WHICH_ANSYS_SOLVER Specifies whether Mechanica uses the Frontal, Iterative, or Powersolver ANSYS solver. o o o FRONTAL (default) ITERATIVE POWERSOLVER FEM_Y_DIR_COMPRESS Specifies the Y direction based on compressed and uncompressed geometry. The default value is "no," which indicates that Mechanica will use uncompressed geometry. o o NO (default) YES PRO_ANSYS_PATH Specifies the path to the ANSYS executable. PRO_NASTRAN_PATH Specifies the path to the MSC/NASTRAN executable (nastran). PRO_SOLVER_NAME Specifies the name of the user-defined solver to be included in the Run FEM Analysis dialog box. PRO_SOLVER_PATH Specifies the path to the user-defined solver whose name is included in the Run FEM Analysis dialog box. SIM_ADDITIVE_MASS Adds any masses that reference the same geometrical entity or resolve to the same mesh node. If you set this option to "yes," FEM suppresses the precedence rules that apply to masses. o o NO (default) YES SIM_FEM_NASTRAN_USE_PSHELL For MSC/NASTRAN solutions, this option determines the form that FEM mode uses to output laminated composite shell properties to the solver. When you set this option to "no," FEM outputs laminated composite shell properties using 14 Structural and Thermal Simulation PCOMP cards that reference MAT8 material cards. If you set this option to "yes," FEM outputs laminated composite shell properties using PSHELL cards that reference MAT2 material cards. o o NO (default) YES SIM_NASTRAN_USE_COUPMASS For MSC/NASTRAN solutions, this option enables you to enforce consistent mass matrix generation. When you set this option to "yes," FEM adds PARAM,COUPMASS,1 to the NASTRAN deck to ensure that the solver generates a consistent mass matrix. If you set this option to "no," FEM does not add this statement, and NASTRAN generates a lumped mass matrix. o o NO (default) YES SIM_OUTPUT_OBJ_NAMES Output beam sections name, analyses name, coordinate systems names as comments. SIM_OUTPUT_IDS_FOR_LAYERS Determines whether Mechanica will generate an XML file containing layer data when you output a NASTRAN deck. If you set this option to "yes," Mechanica generates the XML file that provides a listing of node and element IDs for any idealizations—such as beams, shells, and masses—that you place on layers. The file provides lists for all layers that contain simulation entities. The filename for the XML file is outputfilename_layers.xml, where outputfilename is the name that you specified for the .nas file on the Run FEM Analysis dialog box. Mechanica places the file in the same directory as the .nas file. o o NO (default) YES SIM_REGEN_ON_ENTRY Determines whether Mechanica regenerates your model when you initiate a session. o o YES (default) NO SIM_SMOOTH_ASPECT_RATIO Determines the element aspect ratio criterion that Mechanica will use when smoothing a FEM mesh during mesh optimization. You must specify a real 15 Structural and Thermal Simulation - Help Topic Collection number for this option, and the default setting is 7.0. As a general rule, you should not change the default setting unless the first optimization pass shows that the overall element quality has degraded such that setting a new aspect ratio criterion would result in better shaped elements. SIM_SMOOTH_EDGE_ANGLE Determines the element edge angle criterion that Mechanica will apply to quadrilateral elements when smoothing a FEM mesh during mesh optimization. You must specify a real number in degrees for this option, and the default setting is 30 . As a general rule, you should not change the default setting unless the first optimization pass shows that the overall element quality has degraded such that setting a new edge angle criterion would result in better shaped elements. SIM_SMOOTH_SKEW Determines the element skew angle criterion that Mechanica will apply to quadrilateral elements when smoothing a FEM mesh during mesh optimization. You must specify a real number in degrees for this option, and the default setting is 45 . As a general rule, you should not change the default setting unless the first optimization pass shows that the overall element quality has degraded such that setting a new skew angle criterion would result in better shaped elements. SIM_SMOOTH_TAPER Determines the element taper criterion that Mechanica will apply to quadrilateral elements when smoothing a FEM mesh during mesh optimization. You must specify a real number for this option, and the default setting is 0.5. As a general rule, you should not change the default setting unless the first optimization pass shows that the overall element quality has degraded such that setting a new taper criterion would result in better shaped elements. SIM_SMOOTH_WARP_ANGLE Determines the element warp angle criterion that Mechanica will apply to quadrilateral elements when smoothing a FEM mesh during mesh optimization. You must specify a real number in degrees for this option, and the default setting is 10 . As a general rule, you should not change the default setting unless the first optimization pass shows that the overall element quality has degraded such that setting a new warp angle criterion would result in better shaped elements. SIMULATION_FEM_MODE Determines the initial state of the FEM Mode check box on the Model Type dialog box. The default is "prompt," indicating that the Model Type dialog appears when you enter Mechanica with a new or unsaved model and the check box is unchecked. 16 Structural and Thermal Simulation If you select "No," the software assumes you always want to work in native mode, and the check box is unchecked. If you select "Yes," the software assumes you always want to work in FEM mode, and the check box is checked. In either case, if the SIMULATION_PRODUCT config.pro option is set to a specific product, the software bypasses the Model Type dialog box altogether when you enter Mechanica with a new or unsaved model. o o o PROMPT (default) NO YES STD_NASTRAN_TEMPLATE Sets the file path of a NASTRAN deck template. Use the full path to avoid problems. Fatigue Options Use these options to control fatigue analysis. You can also access some of these options on the Fatigue Analysis Definition dialog box. For more information on each of these settings, see Fatigue Analysis. SIM_FATIGUE_BIAXIALITY_CORRECT Controls the use of biaxiality correction. The value types are as follows: o o YES (default) NO SIM_FATIGUE_BIAXIALITY_METHOD Specifies the method Mechanica uses to model biaxiality: Klann-Tipton-Cordes, Hoffman-Seeger, or the most conservative (WORST) of the two methods. The value types are as follows: o o o WORST (default) KTC HS SIM_FATIGUE_CONFIDENCE_LEVEL Specifies the percentage confidence in the predicted life result value. The value type is numeric and may range from 0.1 to 99.9. The default value is 90. SIM_FATIGUE_EXTERNAL_MATDATA Controls the use of external material data. The value types are as follows: o o NO (default) YES 17 Structural and Thermal Simulation - Help Topic Collection SIM_FATIGUE_HYSTERESIS_GATE Specifies the gate Mechanica applies to cycle counting as a percentage of peak load. The value type is numeric and may range from 0 to 50. The default value is 1. SIM_FATIGUE_INFINITE_LIFE_VALUE Specifies a value for the lives beyond cutoff. The value type is numeric and may range from 1e15 to 1e30. The default value is 1e20. SIM_FATIGUE_MEAN_STRESS Controls the application of the mean stress correction. The value types are as follows: o o YES (default) NO SIM_FATIGUE_MEAN_STRESS_METHOD Specifies the method Mechanica uses to model mean stress: the SmithWatson-Topper Approach, Morrow Correction, or the most conservative (WORST) of the two methods. The value types are as follows: o o o WORST (default) SWT MORROW SIM_FATIGUE_SAFETY_MARGIN Specifies the factor Mechanica uses to determine the Life Confidence quantity. The value type is numeric and may range from 1.1 to 100. The default value is 3. SIM_FATIGUE_USER_DIRECTORY Specifies the directory for user files, for example, external materials files. The value is the path to the directory. The default value is the current directory. SIM_FATIGUE_WRITE_SURF_STRESS Controls the writing of surface stresses to a neutral file. The value types are as follows: o o NO (default) YES 18 Structural and Thermal Simulation Run Options Use these options to control the engine run. You can also access many of these functions through the Analysis>Mechanica Analyses and Design Studies command and the associated dialog box. For more information on each of these settings, see Setting Up a Run. SIM_MAX_MEMORY_USAGE Specifies the maximum amount of memory that the Mechanica mesher and solver or the FEM mesher can use for the run. The value type is a numeric value that is measured in megabytes and should be greater than 0. The default value is 128. Be aware that, if you are a FEM user and enter a value of 0, the FEM mesher will assume that it can use all available memory. SIM_RUN_COPY_FEM_NEUTRAL_FILE Controls whether Mechanica copies the FEM neutral file (.fnf extension) into the study directory. The value types are as follows: o o YES (default) NO SIM_RUN_OUT_DIR Specifies the directory for output storage. The value type is a complete path name. By default, Mechanica uses the current directory. SIM_RUN_TMP_DIR Specifies the directory for temporary file storage. The value type is a complete path name. By default, Mechanica uses the current directory. Result Display Options Use these options to control the results display. BMGR_PREF_FILE Specifies the path to a text file that you create to control the default settings for your graphs. SIM_PP_BACKGROUND_COLOR Specifies the background color of the work area for the results display. The value types are as follows: o o PROE (default) BLUE 19 Structural and Thermal Simulation - Help Topic Collection o o BLACK WHITE SIM_PP_PATH_ABSOLUTE Controls whether Mechanica uses an absolute path for study directories when it writes an .rwd file for results. When you create an .rwd file, Mechanica includes the results windows currently defined in the results session. Further, it includes path information on that indicates where the study directories for the results windows are located. The path for the study directories can be either absolute or relative, depending on how you set this config.pro option. If you set this option to "yes," Mechanica uses absolute paths for study directories when it writes the .rwd file. When you set the option to "no," Mechanica writes relative paths in the .rwd file. If you use this configuration option, you should be sure you have a thorough understanding of your operating environment and sharing needs. Setting this option to "no" can be beneficial if you plan to share the entire file structure with another location or plan to move the file set in the future. The value types are as follows: o o YES (default) NO SIM_PP_VRML_EXPORT_FORMAT Specifies the VRML export format that Mechanica uses when exporting VRML reports: o o VRML2.0 (default) VRML1.0 SIM_PP_VRML_FEATURE_EDGES Specifies that the VRML file will represent feature edges. By default, no feature edges are represented in the VRML file. The value types are as follows: o o NO (default) YES Miscellaneous Options These options are not a part of any other larger category. SIM_MAT_POISSONS_NOTATION Specifies the convention used for defining Poisson's ratio for anisotropic materials as being either Tsai (column-normalized) or Jones (row-normalized). This option affects only the labels for Poisson's ratio on the Material Definition dialog box. 20 Structural and Thermal Simulation The value types are as follows: o o TSAI (default) JONES SIM_USE_LAYERS Specifies that Mechanica allows Pro/ENGINEER layers to transfer as groups into independent mode. When set to "no," Mechanica transfers components as groups, but does not transfer layers as groups. When set to "yes," Mechanica transfers each relevant layer to a group. Note that Mechanica transfers blanked or hidden layers as invisible. Also, if a Pro/ENGINEER coordinate system resides on a blanked layer that transfers to independent mode, the corresponding Mechanica UCS entity will be invisible. o o NO (default) YES Mechanica Products Introducing the Mechanica Product Line The Mechanica product line features the Structure and Thermal modules, each of which focuses on different aspects of mechanical behavior: • Stucture — Use this module to evaluate the structural behavior of a part or assembly. This module lets you create structural loads and constraints for your model, then perform static, modal, prestress, buckling, and vibration analyses. You can also evaluate the fatigue life of your model and solve contact problems. Structure's primary emphasis lies with linear, smalldeformation problems, but you can use this module to solve largedeformation problems as well. Depending on licensing, Structure incorporates Fatigue Advisor, a module that enables you to study the fatigue life of your model. Thermal — Use this module to evaluate the thermal behavior of a part or assembly. This module lets you apply heat loads, prescribed temperatures, and convection conditions to your model, then perform steady-state or transient thermal analyses. You can use the results of these analyses to study heat transfer in your model. You can also use the results of a thermal analysis as the basis of a temperature load in Structure. • Mechanica Structure Mechanica Structure allows design engineers to evaluate, understand, and optimize the static and dynamic structural performance of their designs in a real-world environment. Structure's unique adaptive solution technology provides fast, accurate solutions automatically—solutions that help to improve product quality and decrease design costs. In addition to its native solver, Structure's FEM mode offers specialized 21 Structural and Thermal Simulation - Help Topic Collection analyses that automatically create fully associative FEA meshes for third-party finite element solvers. Structure enables you to: • • • set up a real-world environment for your design by applying properties, loads, and constraints to model geometry control how Mechanica meshes your model to ensure the most efficient solution define the level of solution accuracy up front by specifying convergence settings before running a simulation, and watch as Mechanica automatically checks for errors, converges to an accurate solution, and generates convergence information for verification use the functionality of Mechanica's adaptive solver or use FEM mode to solve finite element models with NASTRAN or ANSYS select one or more sensitivity parameters to vary over a range and then review graphs of desired outputs as a function of that changing parameter optimize designs to best meet design goals such as minimizing the cost of the design or its total stress. For example, you can ask Structure to minimize the mass of an assembly while keeping stress, first modal frequency, and maximum displacement within limits. store and view displacement, stress, and strain over selected model entities as fringes, contours, and query plots view vector plots of displacements and principal stresses as well as results on standard beam sections, animations of displacements, mode shapes, and optimization shape history save and review results of displacement, velocity, acceleration, stress, and RMS quantities as fringes, contours, and query plots evaluate graphs of any measure at each step in linear and logarithmic format obtain summary values for all single-value evaluation methods (minimum, maximum, maximum absolute value, and RMS) • • • • • • • • Mechanica Thermal Mechanica Thermal provides design engineers with expert tools to simulate the behavior of parts and assemblies subject to thermal loading. Thermal relies on unique adaptive solution technology that provides fast, accurate solutions automatically, helping you improve product quality and decrease design costs. In addition to its native solver, Thermal's integrated mode offers specialized analyses that automatically create fully associative FEA meshes for third-party finite element solvers. Thermal enables you to: • • • set up a real-world environment by applying heat loads, prescribed temperatures, and convection conditions to model geometry specify convergence settings based on local temperature, energy norm, global error norm, or measures you define. Then, review graphs to visually inspect the convergence behavior. study your design's thermal behavior at a single point in time or as that behavior changes through a set of user-specified intervals 22 Structural and Thermal Simulation • • • • use the functionality of Mechanica's adaptive solver or use FEM to solve finite element models with ANSYS select one or more sensitivity parameters to vary over a range and then graphically review results as a function of that changing parameter optimize designs to best meet such design goals as minimizing the temperature heat flux, temperature gradients, or any other aspect of the design. For example, you can ask Thermal to minimize the mass of an assembly while keeping stress, first modal frequency, and maximum model temperature within limits. store and view results as fringes, contours, and query plots of temperature, temperature gradient, and heat flux over selected model entities Mechanica Workflow When you use any of the Mechanica products to analyze and optimize your design, you typically complete the various activities required for simulation modeling and analysis in a particular order. The workflow you use depends on the product. These links take you to a discussion of the workflow for each product: • • Native mode FEM mode The workflows described in these discussions represent the most common approach to each product. However, there are several alternatives, some more efficient than others. The workflow that you ultimately develop will depend on your design process, the goals you are trying to achieve, and the nature of your model. Native Mode Workflow When you analyze and optimize a design in native mode, you complete the following four-step process: • • • • Develop Your Model • • • Create your model geometry in Pro/ENGINEER. Simplify the model. Define a system of units. Add modeling prerequisites such as coordinate systems and regions, if desired. Add materials, loads, constraints, contact regions, and measures. Add idealizations such as springs, beams, shells, and so forth. Check the mesh. 23 Structural and Thermal Simulation - Help Topic Collection Analyze the Model • • • Define an analysis. Run the analysis. Review the analysis results. Define Design Changes • • Define the design parameters. Review and modify the shape or property changes. • • • • Optimize the Model Define sensitivity and optimization studies. Run the studies. Review the study results. If satisfied with the optimization results, update your model to reflect the optimized design. Be aware that the order of the steps—particularly during the model development phase—may be different depending on your preferences, modeling goals, and techniques. FEM Mode Workflow When you analyze a design in FEM mode, you typically complete the following fourstep process: • • • • Develop Your Model • • • • Create model geometry in Pro/ENGINEER. Simplify your model. Define a system of units. Add modeling prerequisites such as coordinate systems and regions, if desired. Add materials, loads, and constraints. Add idealizations such as shells, springs, beams, gaps, and masses. Add connections such as welds, links, and interfaces. Define the analysis. 24 Structural and Thermal Simulation • • Define an Analysis Select the analysis type. Select the constraints, loads, modes, and frequencies to be used in the analysis, as applicable. Create the Mesh • • • Apply mesh controls. Create the mesh. Review the mesh and refine, if necessary. • • • • Solve Your Model Export the mesh to FEA solvers such as NASTRAN or ANSYS. Review the exported mesh. Optionally, run the analysis. If you ran an analysis, define and view the results windows and reports. Be aware that the order of the steps—particularly during the model development phase—may be different depending on your preferences, modeling goals, and techniques. Additionally, if you plan to export a deck rather than run a FEM analysis from within Mechanica, you can skip defining an analysis. You can also consider an alternative workflow if you are working with an assembly and create a hierarchical mesh. Operating Modes You can work with Mechanica in two operating modes—integrated mode or independent mode. The mode you use governs whether you work primarily within the Pro/ENGINEER or Mechanica user interface, how you apply modeling entities, the modeling functions available to you, and the types of analyses you can perform. • Integrated mode incorporates Mechanica functionality into Pro/ENGINEER. In integrated mode, you create, analyze, and optimize Mechanica models within Pro/ENGINEER. Because you never start the Mechanica user interface, integrated mode eliminates the need to manually switch back and forth between Pro/ENGINEER and Mechanica. Thus, integrated mode represents the 25 Structural and Thermal Simulation - Help Topic Collection • most streamlined approach to part or assembly modeling and optimization. Within integrated mode, you can work in either of two submodes depending on your modeling needs: o Native mode enables you to run integrated mode using Mechanica's adaptive P-code functionality. Native mode lets you create modeling entities like loads, constraints, idealizations, connections, properties, and measures. In this mode, Mechanica meshes your model with Pcode elements and uses its own adaptive solvers to find a solution. o FEM mode enables you to run integrated mode using Mechanica's finite element modeling functionality instead of its P-code functionality. This functionality enables you to create FEM modeling entities like loads, constraints, and idealizations. It also enables you to mesh your model with H-code elements, run various types of finite element analyses including NASTRAN, ANSYS, and so forth, and review the results of the run. You can activate FEM mode by selecting the FEM Mode toggle on the Model Type dialog box before you enter Structure or Thermal in integrated mode. Independent mode utilizes a separate, fully featured Mechanica user interface for all part modeling, analysis, and design studies. With independent mode, you can build your part or assembly in Pro/ENGINEER and transfer it to independent mode to perform simulation modeling and analysis. Alternatively, you can build your model geometry in Mechanica itself or import a model from a supported MCAD interface. Note: If you transfer a Pro/ENGINEER model to independent mode and then save it in the independent Mechanica user interface, you cannot return any model changes or analysis results to the Pro/ENGINEER environment. Integrated Mode Integrated mode incorporates Mechanica simulation functionality into Pro/ENGINEER. In integrated mode, you create, analyze, and optimize your simulation model in the same user environment that you use to create your Pro/ENGINEER geometry. Here are some unique features of integrated mode: • • You can choose whether to define your model for use in native mode or FEM mode. Native mode provides P-element solutions and FEM mode lets you solve your model using any of several third-party H-element solvers. Mechanica creates the mesh automatically as part of model analysis. For solid models, Mechanica uses solid elements such as tetrahedrons, wedges, or bricks while, for shell models, it applies both triangle and quadrilateral shell elements to achieve the best mesh. You can also have models that combine solid and shell elements to create a mixed mesh. As an option, you can manually add several specialized element types, or idealizations and connections, to your model. These include beams, various types of welds, springs, gaps, contacts, rigid connections, and masses. 26 Structural and Thermal Simulation Although native mode does not normally display elements except as a background for study or analysis results, you can test and refine your mesh before you run an analysis. • You indicate which aspects of your model can change during a sensitivity or optimization study by defining design parameters for dimensions and properties. For dimension changes, you create design parameters using Pro/ENGINEER relations. You can work in more than one model at a time. When you wish to work on another model, you simply open it, and a new work area window opens displaying the newly-chosen model. You do not need to save until you exit integrated Mechanica. For more information, see Considerations for Multiple Model Sessions. • To get a better idea of how integrated mode differs from independent mode, see Operating Mode Comparison. Independent Mode Independent mode relies on the independent Mechanica user interface for all simulation modeling, analysis and design study execution, and results viewing. In independent mode, you have the option of building your model geometry in Pro/ENGINEER, importing geometry from a third-party CAD package, or building the geometry exclusively within Mechanica. After you work with your model in independent mode, you break all association with Pro/ENGINEER and you can no longer automatically update the Pro/ENGINEER model from Mechanica. Here are some features of independent mode: • You can create elements manually or automatically. For solid models, you can create solid elements such as tetrahedrons, wedges, or bricks. For shell models, you can apply triangular and quadrilateral shell or plate elements. As an option, you can manually add several specialized element types to your model. These element types include beams, spot welds, springs, and masses. Mechanica provides a variety of manual element generation methods including geometry selection, point seeding, extrusion, and revolution. If you want Mechanica to create elements automatically, you can use AutoGEM, a tool that generates elements on curves, surfaces, and volumes. • You indicate which aspects of your model can change during a sensitivity or optimization study by defining design variables for dimensions and design parameters for properties. You cannot, however, use Pro/ENGINEER relations or parameters to control shape changes. You can create element-based measures to get information on stress intensity factors (cracking) in your model, resultant forces and moments, and net heat flux. • To get a better idea of how integrated mode differs from independent mode, see Operating Mode Comparison. 27 Structural and Thermal Simulation - Help Topic Collection Operating Mode Comparison Here is a summary of how integrated mode differs from independent mode. Integrated Mode All analysis types P-code native solver and thirdparty H-code solvers 2D and 3D models Geometry created in Pro/ENGINEER only Independent Mode All analysis types P-code native solver only • • • • • • • • 2D and 3D models Geometry created in Pro/ENGINEER, Mechanica, or one of several CAD file formats Modeling entities created in a separate Mechanica user interface or transferred from integrated mode Geometry-based and elementbased measures Elements created manually or through AutoGEM • Modeling entities created in the Pro/ENGINEER user interface • • Geometry-based measures • • Elements generated automatically with testing and refinement capabilities Design parameters only— created in Pro/ENGINEER • • • Shape and property design variables—created in Mechanica Classic results definition and viewing workflow • Streamlined results definition and viewing workflow • Planning and Modeling Considerations The basis of good part or assembly design is planning. When planning any Pro/ENGINEER part or assembly, you consider a variety of issues including dimensioning schemes, feature relationships, tolerances, and assembly connection methods. You also take a careful look at the context in which a part will be used. As a simple example, if you are building an assembly, you need to make sure each part in the design fits its connecting parts. Similarly, if you work with Mechanica, you need to plan ahead for all aspects of simulation model development. You consider such issues as whether the methods you use to build your part will result in a model that can be easily optimized, 28 Structural and Thermal Simulation whether you have created auxiliary features that will support modeling situations such as localized loads, and so forth. You also need to think about the effect that optimization and shape change will have on any related parts. For example, you need to determine whether a new optimized part shape will still fit into a parent assembly. In developing Pro/ENGINEER parts and assemblies that you plan to evaluate in Mechanica, you may want to experiment with various techniques that can make your simulation model easier to use and improve solution times. You may also want to add certain modeling entities to serve as a basis for other simulation modeling entities such as loads and constraints. Here are some considerations and techniques you can review: • • • part and assembly development techniques simulation modeling techniques and prerequisites factors to consider when planning for optimization Each of these discussions assumes that you are already familiar with Pro/ENGINEER part and assembly building techniques. Therefore, the focus lies with explaining general methodology rather than with providing detailed instructions on how to create Pro/ENGINEER parts and assemblies. Building Part and Assemblies Planning and Building Parts and Assemblies There are a number of strategies you may want to consider when planning and building Pro/ENGINEER parts and assemblies for use with Mechanica. These strategies can help you develop models that have faster mesh and solution times, promote a broad choice of shape changes that you can have Mechanica work with during sensitivity and optimization studies, and let you more easily identify components in your model or work with its parts. Here are some techniques you can consider: • • • Keep your parts simple. Suppress nonessential features. Determine which aspects of your design you want Mechanica to change, and develop your parts and assemblies to allow these changes. Most of the above guidelines focus on part planning and building, but some are valid for assemblies as well. To learn more about issues you should consider if you are working with assemblies, see Assembly Considerations. 29 Structural and Thermal Simulation - Help Topic Collection Strategy: Keeping Models Simple Strive for simplicity as you build your part. When you work with a part in Mechanica, you want the software to focus on the essentials of your design, not the cosmetics. If a feature is not necessary for an analysis or design study and has no anticipated effect on the results, omit it for the time being. Also, if possible, omit areas of your design that cannot be changed. After you finish your Mechanica optimization, you can add these items back into your design. This approach offers several advantages. First, Mechanica design studies run more quickly for simpler parts. Second, if you omit unnecessary portions of the design from your part, you do not risk setting up relationships that may artificially restrict the movement of your design parameters. Third, you can use analysis results from a partly-developed model to answer questions about how you should build the remainder of the model. Simplified designs offer different advantages at each design stage. • • Conceptual Design Stage — In this early design stage, you can quickly and easily conduct feasibility studies, even though you do not have a fully constructed part or assembly. Intermediate Design Stage — You can complete a finite element model of a partially defined assembly, or a part that has a few key areas still undefined. There are two advantages: o You can vary the completed areas of your part without having to wait for the incomplete areas to be fully defined. o You can guide the design of the incomplete areas with the results of the analysis. Analysis of a Complete Part — You can reduce the complexity of the finite element representation of the part or assembly. • There are a number of methods you can use to simplify a part or assembly. You should determine the best approach by evaluating the nature of your model and your simulation goals. Strategy: Suppressing Nonessential Features Feature interference can occur for a variety of reasons. If you have already built your part and find that Mechanica cannot perform a shape change due to the interference of two features, identify the feature that is causing the problem and suppress it if possible. When you suppress a feature, that feature becomes nonexistent from Mechanica's point of view. Note: Do not suppress a feature that carries a load or constraint unless you are doing so to prepare for an analysis type that does not require loads or constraints, such as a modal analysis with rigid mode search. 30 Structural and Thermal Simulation Before defeaturing an aspect of your design, ask yourself the following questions: • • Would suppressing the feature change the behavior of the model? Would suppressing the feature eliminate a factor that Mechanica should consider during a sensitivity study or optimization? If the answer to both questions is no, consider suppressing the feature. Otherwise, you need to limit the design parameter range to eliminate the problem or, in some cases, rebuild the part using a different development scheme. Note: If your part includes a large number of datum points that have no use in Mechanica, consider suppressing these points before accessing Mechanica. An excessive number of datum points can affect performance. Planning for Shape Changes The intent of Mechanica optimization is to redesign a part so that it better meets your design goals. To achieve this purpose, Mechanica changes the shape and size of the part’s features according to your instructions. The aspects of the part that Mechanica changes are known as design parameters. A design parameter is a dimension or property that you direct Mechanica to alter within a specified range for the purpose of a sensitivity or optimization study. You can also use design parameters in a standard Mechanica design study to achieve a singlepoint solution. In this case, however, you change the design parameter to a specific setting rather than allow it to move through a range of settings. As an example, before you optimize a model, you can designate the position of a hole as a design parameter or a set of design parameters. You can then specify the optimization study so that Mechanica moves the hole until it finds a new location that minimizes stress in the model. When you design a part for use with Mechanica, always think ahead and consider how you want the part’s features to move. Decide in advance which aspects of your part you want to define as design parameters and what the parameter ranges might be. As you build the part, ensure that the movement of these features is not artificially restrained by relationships, topology, and so forth. Here are some techniques you can consider: • • • • • Plan your shape changes and develop your part to allow these changes. Build larger, more basic features first. Identify relationships that prevent desired movement or cause undesired movement. Change dimension names for easy identification. Avoid topology conflicts introduced by design parameter ranges and part building techniques that create interference between features or introduce extreme topological changes. 31 Structural and Thermal Simulation - Help Topic Collection Strategy: Planning Ahead for Shape Changes The first step in planning a part is to evaluate your basic design and determine which aspects of that design you want Mechanica to change. The shape changes you plan to experiment with can have a marked influence on how you feature your part. For example, a part you might normally create as a single feature in Pro/ENGINEER may be better suited to shape changes if you create the part using multiple features. As another example, in parts you create using some of Pro/ENGINEER's more advanced techniques such as blends, sweeps, patterning, and mirroring, you may experience unexpected or unwanted geometry changes during optimization. Strategy: Developing a Featuring Scheme If your part has more than one feature, develop the large features first. Build all features as simply as possible. Add the smaller details as separate features. This approach provides you with a measure of flexibility that helps you address the following situations: • Mechanica is unable to change areas of your design because one of the details artificially limits movement. Provided you originally designed the details as separate features, you can suppress the problem features and rerun the Mechanica study. Your part includes features that do not affect solution quality. By suppressing these features, you often can achieve faster run times and smaller file sizes. • Strategy: Identifying Relationships that Affect Shape Changes As you build your part, consider the relationships you are creating as these relationships can freeze a shape change or introduce an unwanted shape change. Be particularly aware of the following relationships: • • parent/child relationships — If you move a parent, the child moves with it. dimension relations — If you define relations between your part’s dimensions and assign a design parameter to the independent dimension, the dependent dimension changes in accordance with the relation you established. alignment — If you align an aspect of your part with another aspect of your part and assign design parameters in such a way that the aspect you used for alignment disappears, your part fails to regenerate. declared layout relations — If you use a Pro/NOTEBOOK layout when building your part or assembly, Pro/ENGINEER defines relations between the aspects of the part or assembly you declare to the layout and the associated aspect of the layout. For example, if you declare the length of a part to the layout, Pro/ENGINEER defines a relation tying the part’s length dimension to the layout’s length dimension. The layout dimension is the independent dimension. 32 • • Structural and Thermal Simulation Because Pro/ENGINEER treats any part dimension you declare to a layout as dependent, you cannot select the dimension as a Mechanica design parameter without first undeclaring it. • patterning and mirroring — Patterning and dependent mirroring link the movements of multiple geometric entities. If you use these techniques, you will not be able to move geometric entities individually. Further, you may introduce unexpected topology changes or Mechanica may eliminate a geometric entity altogether. Before using these techniques, consider how you may want the shape of your part to change during sensitivity or optimization studies. Because it is fairly easy to set up unintentional relationships while building a part, you should perform the following checks: • • Use the Info>Parent/Child command to review parent-child relationships and reassign dimensions when necessary. Before you enter Mechanica, select the Edit>References>Reroute Feat>Ref Info command to display the reference information window. Review the data in this file to determine each of the dimension references. When necessary, redefine the dimensioning scheme or redesign the feature. Test your design by animating or reviewing the shape changes using the Analysis>Mechanica Design Controls>Shape Animate and Analysis>Mechanica Design Controls>Shape Review commands. If you see any problems or Pro/ENGINEER fails to regenerate the part, redesign the part in a way that prevents conflicts. • Strategy: Changing Dimension Names When you add dimensions to your part, Pro/ENGINEER assigns a generic name to each dimension. This name consists of the letter "d" with a number appended. This naming convention can be confusing in Mechanica, especially if there are multiple design parameters associated with your part. In processing design parameters, Mechanica uses dimension names, Pro/ENGINEER parameter names, or beam section names as the design parameter names. If you create design parameters for your part's dimensions, you may find that changing the generic dimension names to meaningful names helps you identify which design parameter produces what shape change. Because Mechanica tracks the dimensions for all parts in an assembly, changing dimension names is especially important if you are doing assembly work. For assemblies whose parts still have generic dimension names, Mechanica will likely encounter multiple dimensions with the same name. For example, every part in the assembly will probably include a dimension with the generic name of d0. If you try to create design parameters for two different dimensions that have the same name, Mechanica will display a warning and ask you to rename the second dimension. 33 Structural and Thermal Simulation - Help Topic Collection Here are some tips for working with dimension names: • You can check your part's current dimension names with the Analysis>Mechanica Design Controls>Switch Dim command in Mechanica or the Info>Switch Dimensions command on the Relations dialog box in Pro/ENGINEER. You access the Relations dialog box through the Tools>Relations command. You can change dimension names when you define design parameters in Mechanica. If you want to change the names before accessing Mechanica, activate the dimension display in standard mode, select dimension, and use the Edit>Properties command. Once you click this command, you can use the Dimension Text tab on the Dimension Properties dialog box to change the name. • Strategy: Avoiding Topology Conflicts Mechanica cannot resolve certain topological conflicts when it meshes a model. While your part may appear topologically sound at the modeling stage and may mesh successfully during analysis, it may experience unacceptable topological changes when you change its shape during a sensitivity or optimization study. You can inadvertently introduce this type of problem during design parameter or feature creation. Design parameters can cause problems if the movement of one parameter conflicts with that of another or conflicts with the natural boundaries of the part. When adding design parameters to a part, be sure that the ranges you define do not change part topology by introducing interference between features or part boundaries. You should take special care with features created by patterning or dependent mirroring. Additionally, use special care when creating geometry using blends and sweeps. Both of these part building techniques may restrict the movement of your part and make new shapes difficult for Mechanica to mesh during a sensitivity or optimization study. Here are some tips for using blends and sweeps: • • blends — Avoid building complex, multiple blends one on top of another. Mechanica may have trouble resolving the blends if the shape change twists the multiple blends in relation to one another. sweeps — You can introduce meshing problems if you create the sweep using highly complex datum curves or irregular section-to-section transitions. Sweeps with either of these characteristics are more likely to develop topological wrinkles as Mechanica changes their shape and may fail to mesh. To avoid this, you can use advanced surfacing techniques in Pro/ENGINEER to smooth the topology of the section transitions. To test for topology interference, animate or review your shape changes using the Analysis>Mechanica Design Controls>Shape Animate and Analysis>Mechanica Design Controls>Shape Review commands in Mechanica prior to starting your design study. Start with smaller shape changes to make sure the shape changes are realistic before specifying the full range of movement. 34 Structural and Thermal Simulation In addition to interference and topology problems caused by complex blends and sweeps, be aware that topology changes can introduce the following situations: • • Mechanica may experience conflicts between existing loads. In this case, the software may modify one of the loads as a result of the conflict. If the topology change is large and sudden, as with the dynamic suppression or addition of a feature through Pro/PROGRAM, the change may affect the quality of the optimization. The sudden introduction or removal of a feature can increase stresses in such a way that the optimizer stops prematurely, assuming that it has found a lower-stress design immediately prior to the topology change. Assembly Considerations Working with an assembly is similar to working with a part. However, you should bear the following in mind as you work: • • When you model an assembly, you are working with a nonmoving entity. Regardless of the appearance or behavior of the assembly in real-world conditions, Structure and Thermal treat all assemblies as nonmoving. Mechanica requires that all the parts in the assembly use the same system of units. You are responsible for ensuring that all dimensioning systems in your assembly are consistent. If you use a different system of units for some of the parts, Mechanica displays a message indicating that the software automatically converts the part's units so that the units of measure are the same. Up to the point when you run an analysis or study, Mechanica treats your assembly as a collection of individual parts. Thus, during the model development phase, you add modeling entities to parts, rather than to the assembly as a whole. After you start a run, Mechanica merges the individual parts into a single, multivolume body, where individual parts are either connected or unconnected. • If you want Mechanica to treat your assembly as a set of shells, you must first define shells or shell pairs for each part in the assembly. You define shells and shell pairs on a part-by-part basis by accessing Mechanica after opening the individual parts. After you have defined shells and shell pairs for each of your parts, you can access Mechanica from assembly mode and work with the assembly as a whole. For more information on shells and shell pairs, see About Shells. If you use midsurface compression for any parts in your assembly that are made up of shells or shells and solids, gaps can form in your model where the curves (edges) or surfaces (faces) are mated or have assembly constraints applied to them. Mechanica creates connections between these gaps so the parts deform together as if they are one entity. Although Mechanica uses shell, surface region, beam, mass, and spring definitions from the individual parts that make up an assembly, it ignores any modeling entities and idealizations you added to the parts while working in • • • • 35 Structural and Thermal Simulation - Help Topic Collection • • • part mode. Consequently, you need to assign new modeling entities and idealizations when you work with the assembly. Mechanica disregards all design parameters assigned to individual parts. For assemblies, be aware that you cannot place loads or constraints on geometry that Mechanica merges during a run. If a portion of a merged surface is free—for example, two volumes that have mated surfaces, but one surface is larger than the other—you can create a surface region on the free area and then apply the load or constraint to that surface region. When using family table instances in assemblies, note that any modeling entities you create are stored with the assembly rather than with the part. Using Effective Modeling Techniques Simulation Modeling Techniques and Prerequisites When preparing a part for modeling and analysis, you create Mechanica modeling entities such as materials, constraints, loads, and measures. Before you can create certain types of modeling entities, you need to add specific features to your part. You may also need to add datum geometry to your part for the following reasons: • • to create an origin for certain constraints and loads to simulate conditions applied to surface regions You may need to take special steps to prepare your model for 2D analysis, such as adding a Cartesian coordinate system, or to prepare a symmetric model, such as defining cuts along the axes of symmetry. As a step in your part planning process, decide which types of modeling entities you want to add to your model. After you have your plan in mind, determine the requirements for each of the entities you will define. Here are some of the techniques and prerequisites you may want to consider: • • • • • • • determining your model's system of units adding coordinate systems adding datum features defining surface and volume regions defining Pro/ENGINEER parameters using symmetry preparing a 2D model Units Settings Before designing your model, you need to select a system of units in which Pro/ENGINEER stores all data in the database. You can use the Pro/ENGINEER Units Manager menu to select a system of units for your Mechanica model. If you do not define a system of units, Pro/ENGINEER uses a default system of units—inch pound-mass second (inch lbm second). 36 Structural and Thermal Simulation You can select from a predefined system of units, create a custom system of units, or set a default system of units for your model. You can learn more about units by reviewing these references: • • • Predefined systems of units or custom systems of units — See Systems of Units Management. Setting a default system of units — See the discussion of pro_unit_sys in Configuration File Options. Unit conversion tables and other units tables — See Unit Conversion Tables. The Pro/ENGINEER default, inch pound-mass second (inch lbm second), is not a standard system of units, and thus is not described in the tables. Using Coordinate Systems Many Mechanica modeling entities reference coordinate systems, either implicitly or explicitly. Mechanica uses reference coordinate systems to determine such functions as the direction of a load, the placement of a load, the orientation of a material, and so forth. When you start your Mechanica session, the software adds a default coordinate system to your model. This coordinate system is known as the World Coordinate System (WCS). The WCS is a Cartesian coordinate system with an origin at 0 0 0. At the time that it comes up, Mechanica defines the WCS as the current coordinate system and assumes the WCS is the coordinate system it should use when creating modeling entities. If you want to apply your modeling entities relative to a different coordinate system, you can set that coordinate system as current using the Edit>Current Coordinate System command. Making a coordinate system current means that Mechanica will base the creation of certain modeling entities on that coordinate system. You can also create new coordinate systems in Mechanica using the Insert>Model Datum>Coordinate System command. You can define coordinate systems you create in Mechanica as Cartesian, cylindrical, or spherical, enabling a more flexible and accurate realization of mechanical behavior. For example, cylindrical coordinate systems can be handy when defining cyclic symmetry constraints. Note: If you select a 2D model type, you must choose a Cartesian coordinate system that you want Mechanica to use as the reference coordinate system. Using Datum Features Using datum features such as datum points, curves, surfaces, and axes can help you simulate a variety of effects and apply a number of different types of modeling entities. For example, you need datum points to create such entities as point loads, local measures, mesh controls, and certain idealizations such as springs, masses, and spot welds. You use datum curves and surfaces to create surface and volume 37 Structural and Thermal Simulation - Help Topic Collection regions, enabling you to isolate loads and constraints, add loads and constraints to free portions of merged surfaces, and so forth. You can create datum features for your part in either Pro/ENGINEER or Mechanica. There are differences implicit in where you create these features: • Pro/ENGINEER — If you create the datum features in Pro/ENGINEER, the datum features will be visible on your part in both Pro/ENGINEER and Mechanica. You can also take advantage of certain Pro/ENGINEER part building techniques not available with Mechanica datum geometry creation, such as patterning and mirroring. However, you may find that adding these features in Pro/ENGINEER creates visual clutter that may prove distracting when you use your model for other purposes, such as manufacturing or documentation. If this is the case, consider creating the datum features within Mechanica instead, as they will not be visible when you return to Pro/ENGINEER. • Mechanica — If you create the datum features within Mechanica, these are known as simulation features. You can create simulation features at any time during your Mechanica session—before you add modeling entities or as you define those modeling entities. Simulation features are only available to you during your Mechanica sessions unless you promote them. The software turns off these features each time you return to Pro/ENGINEER. Working with Surface and Volume Regions In some situations, you may want to isolate particular areas of your model to create a more refined mesh or to more closely simulate real world conditions. For example, if a portion of a surface on your model undergoes repeated force from a piston, you may want to apply a load only to the circular profile where the piston contacts the surface. As another example, you may have a solid model that demonstrates poor mesh quality and singularities at a re-entrant corner. In this case, you can create a volume region around the re-entrant corner to ensure a better mesh outside of the volume region. You can then chose to disregard the results within the volume region, as the P-orders will be falsely high. Mechanica enables you to isolate both surface areas and portions of a volume. To do so, you create surface regions and volume regions. By definition, a region is the child of the following: • • The geometry that describe the region The original surface or volume As such, a region’s location can change if you apply design parameters that change the shape of the original surface or volume. 38 Structural and Thermal Simulation A surface region is a contour that subdivides a part surface or volume to allow partial loading, constraining, or shell pairing of that surface. In situations where you want to constrain or load a specific portion of a part surface, you can create a region on the surface and apply the load or constraint to that region only. A volume region is, essentially, a cut or protrusion that subdivides a volume into two distinct subvolumes. There are a variety of methods that you can use to define the contour of a volume region, including extruding the volume region, revolving the region, and developing the regions from a blend, sweep, or quilt surface. You can also use advanced volume region creation techniques such as helical sweeps, variable section sweeps, and sweeps based on blended sections retrieved from a file. You use volume regions primarily if you want to refine your mesh in either native mode or FEM mode. Additionally, in FEM mode, you can apply different material properties to the parent volume and the solid chunk created by the volume region. In this case, you place the differing material property on the surface that defines the volume region, and the material propagates through the solid chunk. You can also place loads, constraints, and other modeling entities on the surfaces that define the volume region, be they internal or external surfaces. Creating surface or volume regions can also prove handy if you want to define a small contact region for contact analysis instead of using an entire part as the contact region. Pro/ENGINEER Parameters You can use Pro/ENGINEER parameters as Mechanica material properties, certain load and constraint values, design parameters, or measures. This functionality enables you to do the following: • • • Define material properties in such a way that Mechanica can vary individual characteristics of the material—for instance, Young's modulus or mass density—during a design study Vary Pro/ENGINEER dimensional parameters as part of a design study Use Pro/ENGINEER parameters as the limits or goals of an optimization study You can also use Pro/ENGINEER parameters to define the thickness of simple shells or the stiffness properties of simple springs. Before addressing the specific issues that you need to consider when creating Pro/ENGINEER parameters for use in Mechanica, let us take a moment to review some basic concepts. In Pro/ENGINEER, you can control many aspects of part design through the use of parameters. Parameters enable you to set particular values for a dimension, drive the value of one dimension based on the behavior of another dimension, dynamically suppress features based on changes in the part, and so forth. 39 Structural and Thermal Simulation - Help Topic Collection You can define Pro/ENGINEER parameters in the following two ways: • Through the Tools>Relations command in Pro/ENGINEER — In this case, the value of the resulting parameter depends on other values, and can change as those values change. For example, if you define parameter1 as equal to d0 using the Relations command, Pro/ENGINEER ties the value of parameter1 to d0 as a symbolic variable and does not record d0's current value. Thus, if you later change the value of d0, parameter1 changes along with d0. Parameters created through the Relations command are sometimes known as driven—or dependent—parameters because they are controlled by the equation you define. • Through the Tools>Parameters command in Pro/ENGINEER — In this case, the resulting parameter is a symbolic constant—in other words, a single, unchanging value. For example, if you define parameter1 as equal to d0 using the Parameters command, Pro/ENGINEER determines the current value of d0 and records parameter1 as equaling that value. Even if you later change the value of d0, the value of parameter1 does not change. Parameters created through the Parameters command are sometimes known as driving—or independent—parameters because they are capable of controlling activity. If a conflict occurs, bear in mind that parameters created through the Tools>Relations command override parameters created through the Parameters command. Taking Advantage of Symmetry Working with Symmetric Models If the model you create is symmetric, you have the option of subdividing the model and working with a symmetric section instead of the entire model. By modeling only a portion of the part, you can greatly reduce the number of elements in your model, thus saving significant analysis time and system resources. Depending on the model, you can also save yourself the overhead spent defining repeated versions of a load or constraint or selecting multiple surfaces, edges, or points during load or constraint definition. For example, if you were trying to determine how a disk reacted to a uniform load applied to the top surface, you might decide that you only wanted to analyze a portion of the disk. Because the part and modeling conditions are symmetrical, the analysis results for a section of the disk would provide information accurate enough to give you an idea of how the model will behave as a whole. 40 Structural and Thermal Simulation For a model to be symmetric for Mechanica's purposes, it must exhibit the following characteristics: • • The geometry must be symmetric. The loads, constraints, and idealizations must be symmetric. There are two types of symmetry you can model in Mechanica—mirror symmetry and cyclic symmetry. Mirror symmetry relies on the principle that one segment of a model is the mirror image of other segments. An example of this type of model would be a rectangular plate with a hole at its center. In native mode you can use the mirror symmetry constraint to take advantage of your model's symmetry. To use mirror symmetry in FEM mode you must apply a displacement constraint to fix translation normal to the plane of symmetry and fix rotations in opposition to the plane of symmetry. Cyclic symmetry relies on the principle that a segment of the geometry is repeated in a cyclic manner throughout the model, but the segment is not a mirror image, either in its geometry or its load scheme. An example of this type of geometry would be a fan blade or turbine. You can only use cyclic symmetry in native mode. FEM mode does not support this type of modeling. The methods you use to develop these two types of symmetry differ, as does the application of constraints and certain loads. Both types of symmetry can prove efficient for a 3D solid or shell model. The choice of which symmetry type you use depends on the model and the problem you wish to solve. Note that, in some situations, you can use 2D axisymmetric modeling in place of symmetry. While not strictly a form of symmetry, 2D axisymmetric modeling provides an extremely efficient alternative to treating your model as a symmetric solid. This form of modeling relies on the principle that a 2D slice of your solid model, if rotated around an axis, can accurately depict the whole of your model's geometry, loads, and constraints. For an example of this type of model, see Setting up a Solid Model for a 2D Analysis on an Internal Surface. Example: Using Mirror Symmetry Mirror symmetry relies on the principle that you can describe the behavior of an entire model using one segment, provided that segment is the mirror image of each of the other segments. Therefore, you can model the segment rather than the whole, and still get an accurate idea of your model's behavior. To use mirror symmetry, you must be able to divide your model in such a way that each segment you remove mirrors the segment that remains. The easiest way to determine whether a model shows this type of symmetry is to imagine folding the model. If you can fold the model in such a way that the segments are geometrically identical and have loads and constraints with identical orientation and placement, your model demonstrates mirror symmetry. Additionally, all loads on each segment must have the same value. If you want to take advantage of mirror symmetry in your model, you need to complete two steps—identifying the axes or planes of symmetry in your model and 41 Structural and Thermal Simulation - Help Topic Collection applying mirror constraints. For example, let us say you are working with a rectangular plate that has a hole at its center. A bolt secures the plate at the hole, locking it in place, and the plate bears an identical force load acting on either end. The model qualifies for mirror symmetry because the geometry, loads, and constraints are all symmetrical. Looking at the model as a whole, you would first decide how to divide the model. The best choice is as follows: You can choose to cut the original model at the division lines, or simply apply mirror symmetry constraints along those lines. Note that, if you use the division plan proposed above, you will end up working with one quarter of your model. You could also choose to cut the original model in half instead, but your resulting model would have more elements and be less efficient for the Mechanica solver. Thus, you should always strive to find the smallest symmetric section. The remainder of this discussion assumes that you are working with a cut model. To apply mirror symmetry constraints you must select enough geometric entities to define a plane. If you cut the model as in the figure below, you can create mirror symmetry constraints by selecting the surfaces created by the cuts. If you choose not to cut the model, you would need to define enough datum points or axes to define the plane. 42 Structural and Thermal Simulation Here, you add a mirror constraint in the X direction along the vertical cut, where the surface would normally merge with the rest of the part geometry. Similarly, you add a mirror constraint in the Y direction along the horizontal cut. In this way, you mimic the way that the geometry would behave were it part of the full model. Note that mirror symmetry constraints are not available in FEM mode. However, you can add constraints simply by defining a displacement constraint and selecting the surfaces at the horizontal and vertical cuts as the constraint references. In addition to adding the mirror symmetry constraints at the cuts, you also need to adjust the load on the symmetric section by dividing the additive load seen by the model by the number of segments that result from the cut process. This situation occurs whenever you apply your load using a total load distribution. In this case, the model sees an additive total force load of 200 pounds—100 pounds on one end of the model, and 100 on the other. To develop the symmetric segment, you cut the model into 4 parts. Dividing 200 by 4 yields a 50 pound load on the symmetric segment. Tip: If you had modeled this problem using a pressure load or force per unit area load distribution, you would not need to divide the load. For both of these load types, Mechanica performs any load division automatically. Example: Using Cyclic Symmetry Cyclic symmetry relies on the principle that, in a given model, a segment of the geometry can be repeated in a cyclic manner an integer number of times to form the whole of the model. In this case, the segment is not a geometric mirror image. With cyclic symmetry, loading conditions also repeat cyclically. As with mirror symmetry, you work with a segment of the model, but still get an accurate idea of your model's behavior as a whole. Cyclic symmetry is particularly useful for models where the symmetric segment has a complex shape or the cuts you must make to isolate the symmetric segment are not fully planar. For example, the cuts you would make to isolate one blade of a turbine are likely to bend in one or more directions. 43 Structural and Thermal Simulation - Help Topic Collection To use cyclic symmetry, you must be able to divide your model in such a way that the segment you chose to work with is repeated cyclically throughout the model. The easiest way to determine whether a model shows this type of symmetry is to imagine cutting the model into identical wedges. If you can slice the model in such a way that the segments are geometrically identical and have loads, constraints, and material properties with cyclically repeatable orientation and placement, your model demonstrates cyclic symmetry. Additionally, for loads applied to specific geometry such as total force loads, the load seen by each segment must have the same value. If you want to take advantage of cyclic symmetry in your model, you need to complete two steps—cutting the model into a cyclically repeated segment and applying a cyclic symmetry constraint to the cut surfaces or, in the case of a shell model, to the cut curves. For example, let us say you are working with a fan that has a hole at its center. A shaft secures the fan at the hole, locking it in place in the Z direction but allowing free movement in the T and R directions. The fan bears a centrifugal load with an angular velocity of 700 radians per second about the Z axis. The model qualifies for cyclic symmetry because the geometry, loads, and constraints are all repeated symmetrically. Looking at the model as a whole, you would first plan the cut lines using a cylindrical coordinate system as a reference. The best choice is as follows: 44 Structural and Thermal Simulation The segment defined by the cuts repeats four times to form the circumference of the fan. After you cut the model, you need to add a cyclic symmetry constraint to the model so that the solver will correctly interpret the geometry as a cyclic symmetry segment: Here, you add a cyclic symmetry constraint to both of the cut surfaces. Note that you do not need to change the value of the load to reflect the fact that the load acts on a smaller segment. This is primarily a function of the load type. For example, this model uses a centrifugal load—a body load that, in this case, behaves cyclically. Therefore, the load requires no adjustment. However, if you were working with a total load against the outer surface of the hole, you would need to adjust the load just as you would for standard symmetry. Note that this model does not qualify for mirror symmetry because the fan blades are set at an angle, which would preclude mirroring. Additionally, the centrifugal load would not mirror correctly as, in the mirror image, the direction of the load would oppose the actual direction of the load. Preparing a 2D Model There are several good reasons for treating your model as a 2D model rather than a 3D model. One of the most compelling is the simplicity of 2D models from a meshing and solution perspective. Mechanica can solve your model in a fraction of the time it would take to mesh and solve a 3D model. However, 2D modeling is a specialized form of simulation modeling and is appropriate only if your model displays certain geometric, constraint, and load characteristics. If you plan to perform 2D analysis on your model, you must first define your model as a 2D model type using the Model Type dialog box. The software displays this dialog box when you enter Mechanica, or you can activate the dialog box from within Mechanica by selecting Edit>Mechanica Model Type if you want to convert a 3D model to a 2D model during your simulation session. When you define your model as a 2D model, you use the Model Type dialog box to select the geometry on which you want to perform the 2D analysis and a reference coordinate system. As you 45 Structural and Thermal Simulation - Help Topic Collection prepare your 2D model, be aware that the geometry you select for analysis must be coplanar, and the reference coordinate system must be Cartesian. You may need to create a Cartesian reference coordinate system for your model so that the geometry you select for 2D analysis lies in the XY plane. For 2D axisymmetric models, all coordinates must be positive in X. To read more about specifying a reference coordinate system for your model, see About Coordinate Systems. Mechanica cannot perform 2D analysis on midsurface models, sketches, or sections. If you have a sketch on which you want to perform 2D analysis, you can extrude the sketch into a solid in order to carry out a 2D analysis. Planning for Optimization Planning for Optimization Effects When Mechanica optimizes your part, the shape changes it performs can affect any items associated with your part, such as reference parts. Shape changes can also affect features that you suppress prior to running Mechanica, in that these features may no longer fit the part or may lose a dimensioning basis. Before you start Mechanica, take a moment to consider the effects of optimization shape changes in a wider context. Look at the various ways you use your part and make sure that the optimization does not inadvertently change related parts. Click on these topics to learn how optimization affects various aspects of your part: • • • • Optimization Optimization Optimization Optimization and and and and Suppressed Features Assemblies Generic Parts Reference Parts Optimization and Suppressed Features When it optimizes a part with suppressed features, Mechanica may change the shape of the part such that the suppressed feature no longer fits the part or loses a dimensioning basis. Whether this phenomenon occurs depends on how you developed the part as well as how you planned your design parameters. One of the most common examples of a suppressed feature problem lies in the area of parent/child relations. If you build a suppressed feature as a child of a dimension that Mechanica eliminates during optimization, the suppressed feature is no longer valid when you unsuppress it. You then need to rebuild that feature using a different dimensioning scheme. Before suppressing any feature, review its dependencies on unsuppressed features and other aspects of the design. This approach enables you to better calculate predictable results of your shape changes and, thus, define your design parameter 46 Structural and Thermal Simulation ranges more effectively. You can also determine in advance which suppressed features you may need to redesign after the optimization. Optimization and Assemblies If you optimize an assembly part, the changes that Mechanica makes during optimization may result in a part that no longer fits the assembly. In most cases, these changes will be obvious when you preview your design parameters by animating or reviewing the part's shape. Subtle changes, however, may be more difficult to catch. Fit problems may be even less obvious if you suppressed any features to better accommodate a Mechanica sensitivity study or optimization. As you prepare your part for use with Mechanica, be aware of which features and dimensions are critical in the context of the assembly. Determine whether the benefits of using such a feature or dimension in the optimization outweigh the cost of changing an entire assembly. Where possible, avoid creating design parameters for these features and dimensions. Optimization and Generic Parts When you optimize a generic part from a family table, the dimension changes Mechanica makes can affect other family members. For example, if you optimize the thickness of a generic plate and thickness is not a table-driven dimension, the other parts in the family undergo an identical change in thickness. If you plan to optimize a generic part, review the family table to make sure you understand which dimensions are table-driven. Make sure you want Mechanica to change all instances of a particular dimension before creating design parameters that use the dimension. Pay particular attention to table-driven dimensions that do not have values assigned for each part instance. In cases like these, Mechanica changes all part instances except those that have predefined values. Optimization and Reference Parts A reference part is a duplicate of a design part that maintains a two-way association with the design part. Various Pro/ENGINEER manufacturing modules, such as Pro/MOLDESIGN and Pro/DIEFACE, create reference parts for use in developing manufacturing tools. You define manufacturing features like mold runners and sprues using the reference part as a basis instead of the design part. This approach allows Pro/ENGINEER to maintain a record of tooling features separate from the design part. The associativity between the design part and reference part enables Pro/ENGINEER to dynamically update manufacturing tools created through its manufacturing 47 Structural and Thermal Simulation - Help Topic Collection modules. In other words, if you alter your design part, you simultaneously change the reference part and the manufacturing tool built from the reference part. With this in mind, be aware that Mechanica changes the shape of any associated manufacturing tools at the same time that it changes the shape of your part. If Mechanica changes aspects of your design that define manufacturing tool features, the manufacturing tool may no longer be valid. For example, when you use Pro/MOLDESIGN to create a mold and you define one of the runners as Point–Surface, Pro/MOLDESIGN places a runner between a datum point and the specified part surface. If Mechanica then eliminates the surface as part of an optimization, the runner will have lost its placement geometry and the mold will no longer be valid. User Interface Basics for Integrated Mode Working With the User Interface To use Mechanica effectively, you need to understand the basics of the user interface and some of the tools available to you through that user interface. A solid knowledge of how to operate the user interface effectively will help you perform tasks such as defining modeling entities and analyses, or reviewing study results. Browse this area of the online Help to learn about the following common activities you perform in Mechanica as well as several tools that can help you make your Mechanica sessions more efficient: • • • • • • • • • • • • • using dialog boxes and message boxes using the Mechanica toolbar selecting geometry and modeling entities using layers using suppression and family tables to manage modeling entities setting simulation visibilities interpreting color references getting information on your simulation model removing all simulation entities from your model transferring your model to independent mode printing your model working with Mechanica configuration options setting environment variables Using Dialog Boxes and Message Boxes Dialog boxes and message boxes are the common communication tools for Mechanica. You use dialog boxes to define such items as modeling entities, analyses, design studies, and results. You use message boxes to answer questions that Mechanica may ask as you work. Message boxes also inform you of problems with your model or provide you with information pertinent to an activity you are performing. 48 Structural and Thermal Simulation Dialog boxes are windows with entry boxes, lists of options, buttons, and other items that enable you to apply settings and values to entities, analyses, and design studies you create or modify. Because dialog boxes are windows, you can move or close them if necessary. Commands that use dialog boxes open the dialog boxes automatically when you select the command. Some commands may use more than one dialog box. Here is an example of a typical Mechanica dialog box. Note that this dialog box does not contain all of the possible items you might see on a dialog box, but does include the most common items. To apply settings using a dialog box, enter or select values using the items on the dialog box. When you select a button on a dialog box, additional buttons or entry boxes related to your selection may appear on the dialog box. The following list describes most dialog box items and how to use them: button check box display-only text entry box Enables you to perform an action. Enables you to select an item. From a group of check boxes, you can select one or many. Displays a name or value that you cannot edit. Provides a place for you to enter a value, name, or 49 Structural and Thermal Simulation - Help Topic Collection list box option menu tab table comment. Displays a list of items with a scroll bar. You usually select an item on the list. Enables you to select one of several options. The dialog box displays the name of the currently selected option. Enables you to select an activity to perform on a dialog box. When you click a tab, the dialog box brings that tab to the forefront for you to fill out. Lists a variety of attributes associated with an entity. You use dialog box tables to select entities that you want Mechanica to act on or that you want to define. You can insert new rows into dialog box tables and delete existing rows. In some cases, you can edit the contents of a table by right-clicking on an item. Mechanica displays message boxes to provide you with important information you need before continuing with a command. Some Mechanica commands use message boxes to display a question or a message. If this is the case, the message box includes buttons that you can use to respond to the question. You select the buttons on these message boxes with the left mouse button. You can also select the default response, the button with the double border, by pressing RETURN. Like dialog boxes, a message box is a separate window that you can move or close. Mechanica Toolbar You can access many of the Mechanica functions by using toolbar buttons. When you start Mechanica, a toolbar appears to the right of the graphics window. The toolbar is customizable. Use Tools>Customize Screen to control the position of the toolbar, and to control which icons Mechanica displays. For more information on customizing the user interface, search the Basic Pro/ENGINEER functional area in the Pro/ENGINEER Help Center. Note: The default selection of buttons changes depending on the Mechanica module you are in. Click the links in the following table to get information on the functions of each toolbar button. Button Description New Displacement Constraint New Along Surface Constraint New Symmetry Constraint New Bearing Load New Centrifugal Load New Gravity Load 50 Module* S, SF SF S S S, SF S, SF Structural and Thermal Simulation New Global Temperature Load New Heat Load on Point New Heat Load on Edge New Heat Load on Surface New Heat Load on Volume New Force or Moment Load New Pressure Load New Structural Temperature Load on Point New Structural Temperature Load on Curve S, SF T, TF T, TF T, TF TF S, SF S, SF SF SF New Structural Temperature Load on Surface SF New Structural Temperature Load on Volume SF New Beam New Interface New Weld New Fastener New Measure New Gap New Mass New Shell Pair New Spring New Rigid Link New Weighted Link New Material Assignment New Cyclic Constraint New Point Convection Condition New Edge Convection Condition New Surface Convection Condition New Prescribed Temperature New Radiation Condition * S, T, SF, TF SF, TF S, T, SF, TF S S, T SF S, SF S, T, SF, TF S, SF SF SF SF, TF T T T T, TF T, TF TF S = Structure, T = Thermal, SF = Structure in FEM mode, TF = Thermal in FEM mode 51 Structural and Thermal Simulation - Help Topic Collection Process Guide Selection Methods There are several ways to select entities on your model as you are performing various Mechanica operations. These include: • Direct Selection — Use Pro/ENGINEER selection methods to select objects directly on your model. The direct selection can be handy when you want to select geometric references for simulation entities (springs, beams, loads, constraints, and so forth) before opening an entity definition dialog box. In this case, if your geometric selections are valid, they appear in the References area when you open the corresponding entity definition dialog box. If they are not valid, along with the entity definition dialog box appears the SIM SELECT menu that you can use to make new selections. Model Tree — Use the Model Tree to select model entities from its list of entities and features. You can select entities from the Model Tree just as you would select them directly on your model. You can also work from the Model Tree, highlighting an item, and then right-clicking to display information about the selected entity. Object Action — Select any entity on your model, or on the Model Tree, and right-click to perform operations on the shortcut menu that appears. Search Tool — Use the Search Tool dialog box to find modeling entities by using criteria such as name, type, and property. • • • Using Layers You can group different kinds of modeling entities and control their visibility in part or assembly mode by creating and maintaining layers. For example, by placing items on a layer, you can show or blank the items by showing or blanking the layer. You create and maintain layers through the Layers dialog box. When you select on the Pro/ENGINEER toolbar, the Layers dialog box appears. You can also access the Layers dialog box by selecting Show>Layer Tree on the Model Tree. Use this dialog box to: • • • create, edit, and delete layers add appropriate simulation features to a layer show, hide, or isolate features by layers 52 Structural and Thermal Simulation In Mechanica, you can place the following objects on layers: • • • • loads constraints simple or advanced shells shell pairs • • • • gaps (FEM mode) rigid links (FEM mode) weighted links (FEM mode) material assignments (FEM mode) interfaces end and perimeter welds • • • beams springs masses • • You place idealizations on layers primarily so that you can hide and show the element renderings for a layer when working with or viewing the mesh. Note that elements associated with simulation objects are only visible if the parent objects are visible. Thus, to hide and show elements, you place the associated idealizations on layers. In addition, you can use layers to hide and show particular idealizations or sets of idealizations as you develop your model. You also place idealizations on layers if you want to transfer them to independent mode as groups. If you transfer a model to independent mode, the layers you define become groups if the config.pro option sim_use_layers is set to "Yes" and if the assembly or part contains layers with geometry. Layers containing datum axes and planes do not transfer to independent mode groups. The transfer also converts all components into groups. In results, you can use layers to selectively display parts of your model in the results window display. You can display or hide beam and shell definitions that you placed on layers before running an analysis, and you can display or hide different components of an assembly. Here are some of the highlights of layer creation that you should consider as you develop layers for simulation features: • • • You can create as many layers as you want in a model. You can associate items with more than one layer or create nested layers. For example, you can associate a mass with several layers. You can use simulation default layer types to organize families of simulation features in your model. For example, if you assign a newly-created layer as the SIM_BEAM default layer, Mechanica places all beams that you subsequently create on that layer. 53 Structural and Thermal Simulation - Help Topic Collection For more detailed information on layers, search the Basic Pro/ENGINEER functional area in the Pro/ENGINEER Help Center. Managing Modeling Entities Through Suppression and Family Tables You can use a number of techniques to manage the appearance or availability of the modeling entities in your model. Many of these techniques primarily manage visibility states. However, two of these techniques are more powerful—affecting not only the visibility of a modeling entity, but its presence or absence during meshing and analysis. These two techniques are: • • suppression of specific modeling entities through the Suppress command suppression of specific modeling entities through the creation of family table instances tailored to the specific types of simulation Managing your model through these techniques can help you simplify and organize its modeling entities. It can also help you meet a variety of different simulation needs without having to create and maintain separate versions of the same model. For example, assume you have a model that you want to evaluate using both static analysis and dynamic analysis. However, you want to apply a different set of AutoGEM controls for the static analysis than you do for the dynamic analysis. In this case, you would create all the mesh controls in the same model. But, prior to running the static analysis, you would use the Suppress command to turn off the dynamic analysis AutoGEM controls. With these entities suppressed, Mechanica only uses the static analysis mesh controls and ignores the suppressed dynamic analysis AutoGEM controls when it creates the mesh at the beginning of the static analysis. Thus, the Suppress command has given you the option of using either of the two AutoGEM control sets without having to maintain separate models. You can achieve a similar effect using family tables within the simulation environment. In this case, you would create two family table instances in your model—instance1 containing the static AutoGEM controls, and instance 2 containing the dynamic analysis controls. You would work in instance 1 when running the static analysis and instance 2 when running the dynamic analysis. You can suppress the following modeling entities using either the Suppress command or the family table instances: • • • • • Loads Constraints Connections Idealizations Mesh controls The way you use the Suppress command and create family table instances in Mechanica is similar to how you work with this functionality in Pro/ENGINEER. However the progression, implications, and cases for use are different. To learn 54 Structural and Thermal Simulation about the specifics of using suppression and family tables in Mechanica, see Suppression and Family Tables. To learn the basics of entity suppression and family tables, search the Fundamentals module of the PTC Help system. Simulation Display Setting Simulation Visibilities You can control how Mechanica displays icons and mesh entities on your model. To do so, select View>Simulation Display or click the Setup Simulation Display button, Mechanica opens the Simulation Display dialog box. Then, use the following tabs on the dialog box to turn on and off particular icon displays and mesh visibility states. • • • • • Settings — Control the appearance of your icons and activate or deactivate the display of mesh control icons. Modeling Entities — Control visibilities of idealization and connection icons. Loads/Constraints — Control visibilities of load and constraint icons. Set Visibilities — Control visibilities of groups of loads or constraints. You can make groups of loads or constraints visible or invisible by turning on or off a load/constraint set from those listed for your model. Mesh — Control how Mechanica displays a mesh. At the bottom of this dialog box is the Show Simulation Entities check box. You can use this to display or hide all simulation entity icons. This check box appears on all tabs. The changes you make in the Simulation Display dialog box affect the current session only. You can change the icon visibilities to affect all Mechanica sessions by making changes in the config.pro file. 55 Structural and Thermal Simulation - Help Topic Collection Settings Tab Use this tab on the Simulation Display dialog box to control the appearance of the icons on your model. When you create certain entities, the software places an icon on the associated geometry. Icons enable you to keep track of entities you apply, let you select these entities for editing or deletion, and give you an idea of where you placed these items. Displaying or hiding the icons on your model allows you to simplify the model's appearance making it easier to view specific areas when necessary. These options are available on the Settings tab: Setting Type Common Settings Display Names Display or hide name tags of idealization and load/constraint icons. Turn icons on or off when model spins. No names Value Default Value Display Icons While Spinning Load/Constraint Display Icons Icons on Display load and constraint icons or turn them off. Display or hide distributed load vectors over geometry. Display in individual colors or all yellow. Scale load icons with the given coefficient. Display or hide tags containing load value. Scale or do not scale load arrows. Display load arrows with heads or tails touching geometry. Icons on Distribution Distribution icons on Individual Colors Individual colors Icon Scale Default size Value Values displayed Arrows Scaled Arrows scaled Arrow Tails Touching Heads touching Mesh Control Display Display Mesh Controls Display or hide mesh control icons. Mesh control icons displayed 56 Structural and Thermal Simulation Modeling Entities Tab Use this tab on the Simulation Display dialog box to control visibilities of idealization and connection icons. The tab lists all idealization and connection icons available in native mode or FEM Mode. However, you can only access icons of those entities that are associated with the particular mode and product you are currently working in, while the others remain inactive. By default, Mechanica sets all accessible icons to be visible. To hide them, you can either use the Clear All button or turn off the icons of specific idealizations or connections. Idealizations, Properties, and Measures • • • • • Beams Beam Sections Beam Releases Springs Gaps • • • • Masses Shells Material Assignments Measures Connections • • • • • • Rigid Links Rigid Link DOFs Weighted Links Weighted Link DOFs Interfaces Fasteners • • • • • End/Perimeter Welds Spot Welds Rigid Connections Contact Regions Gaps To obtain more information about icons, see Icons Used in Mechanica. Another method you can use to manage visibilities is layers. You can place varying combinations of modeling entities as well as loads and constraints on a layer. Then, you can blank the layer to remove the entities on it from view, or show the layer to restore the layer entities to view. For more information on layers, search the Basic Pro/ENGINEER functional area of the Pro/ENGINEER Help Center. 57 Structural and Thermal Simulation - Help Topic Collection Loads/Constraints Tab Use this tab on the Simulation Display dialog box to control visibilities of load and constraint icons. Two sections of the tab list icons available in Structure and Thermal. Although the two products do not share the icons, each having its own set, all icons on the tab are accessible from both products. By default, all Structure icons are set to be visible and all Thermal icons are invisible if you are working in Structure. In Thermal, all Thermal icons are set to be on and all Structure icons are off. If you want to change these settings, use the Clear All or Select All buttons, or make individual selections in the Structure or Thermal section of the tab. Structure • • • • • • Constraints Cyclic Symmetry Forces/Moments Pressures Bearing Loads Gravity Load • • • • • • Centrifugal Load Global Temperature Structural Temperature External Temperature MEC/T Temperature Thermal • • • Prescribed Temperatures Cyclic Symmetry Convection Conditions • • • Radiation Heat Loads Volume Heat To obtain more information about icons, see Icons Used in Mechanica. Another method you can use to manage visibilities is layers. You can place varying combinations of loads and constraints along with the modeling entities on a layer. Then, you can blank the layer to remove from view the entities on it, or show the layer to restore the layer entities to view. For more information on layers, search the Basic Pro/ENGINEER functional area of the Pro/ENGINEER Help Center. 58 Structural and Thermal Simulation Mesh Tab Use this tab on the Simulation Display dialog box to control the appearance of meshes generated in native mode and FEM mode. Depending on which mode you are working in, the content of the tab changes. Native Mode After you generate a mesh using the AutoGEM command, Mechanica displays all mesh elements by default. You can hide them by clicking the Clear All button on the tab or by turning off individual entities from the following list: • • • Mesh Points Solids Shells • • Beams Links You can control the size of mesh entities and the quality of mesh display using the Mesh Display area on the Mesh tab of the Simulation Display dialog box. FEM Mode The FEM version of the tab provides the following options for you to control the FEM mesh display: • • Mesh and Model Mesh Display Mode Color References Mechanica uses color to identify modeling entities, distinguish icons and geometry, indicate the selection state of icons, show meshes, and so forth. In addition, when it displays fringe plots, vector plots, and graphs, Mechanica uses color to show stresses, strains, and other types of results. Pro/ENGINEER uses several basic color schemes, among which are the default color scheme, the black on white color scheme, and so forth. You can work in any of these color schemes, or customize the user interface by establishing a color scheme of your own. Mechanica online help refers to entity and icon color when the color has significance from a modeling perspective—such as the different colors of the top and bottom surfaces in a shell pair—or when the color will help you identify an entity on your screen. Be aware that all references to color in the online help system are based on the default color scheme. If you use a different color scheme, you will need to understand how the colors in your scheme correspond to the colors in the default scheme in order to correctly interpret the online help. 59 Structural and Thermal Simulation - Help Topic Collection For information on the Pro/ENGINEER color schemes and how to set them, search the Fundamentals functional area in the Pro/ENGINEER Help Center. To learn how to customize the colors Mechanica uses for result windows, see Adjusting Color Scale for Fringe, Contour, and Vector Legends and Managing Graphs. Getting Information on Your Model You can obtain informational files and reports on various aspects of your model during your Mechanica session, including model tolerances, contact regions, mass properties, and so forth. To review these files and reports, use the following commands on the Info menu: • • • • • • Simulation Model Tolerance Report Review Total Load for Structure Review Total Load for Thermal Review Contacts Mechanica Mass Properties Some of the commands on the Info menu are present for all models—for example, Simulation Model. Others, such as Review Total Load and Tolerance Report, are only present for certain types of models or for models that include the appropriate modeling entities. Removing Simulation Entities from Your Model The most common way to remove modeling entities from your model is to delete them individually. However, you may occasionally find that you have created a simulation model that does not serve your purposes or that you want a fast way to clean up a model by deleting all simulation entities. In this case, you can use File>New Simulation Model to remove all the simulation modeling entities for the current part or assembly. This command deletes all simulation modeling entities directly applied to your model, including those not visible in the Model Tree. For example, New Simulation Model deletes all materials, loads, constraints, contact regions, and so forth from the model. However, it does not remove library entities such as material definitions, beam section definitions, and so forth. After it deletes the model entities, Mechanica opens a clean version of your model and displays the Model Type dialog box so that you can respecify the product, mode, and model type you want to work with. Do not use the New Simulation Model command if you are trying to delete individual modeling entities. Reserve this command for situations where your model requires deep-level cleanup. If you use New Simulation Model and immediately decide that you wanted to keep the modeling entities after all, you can exit Mechanica without saving the model, and the original modeling entities will return when you next open the model. 60 Structural and Thermal Simulation Transferring Your Model to Independent Mode If you decide to work with your model in independent mode, use the File>Independent Mechanica command to start a separate Mechanica user interface. Mechanica merges all model information—whether your model is a part or assembly—into an independent mode model file known as an .mdb file. This operation creates a complete Mechanica database file that you cannot use in integrated mode. If you want to transfer Pro/ENGINEER layers to the independent mode model, you need to set the sim_use_layers config.pro option. Printing Your Model You can print the model from your work area in Mechanica at any time during the creation and modification of your model. This is very useful for creating reports that track the evolution of your model. You use the File>Save A Copy command, and then choose the format for the image. Most of the popular formats, such as JPEG and TIFF, are available. Changing Configuration Settings You can control certain aspects of your Mechanica sessions by creating a configuration file that Pro/ENGINEER references each time you open the software, or during the course of a specific session. Configuration files let you control: • • • • • • Mechanica icon display various aspects of FEM mode operation such as mesh defaults, solver parameters, shell compression controls, and output options default unit settings Fatigue parameters run options result display options There are two methods you can use to create or update a configuration file: • • You can manually enter the various configuration options into a text file using a standard text editor like Notepad, WordPad, or vi. You perform this process outside of Pro/ENGINEER. You can select the Tools>Options command from within Pro/ENGINEER. When you select this command, Pro/ENGINEER displays the Options dialog box. You use this form to set a configuration option, update an existing configuration file, create a new configuration file, or activate a different configuration file. There are also two different types of configuration files—permanent files and sessionbased files. Permanent configuration files are usually named config.pro and sessionbased configuration files are called current_session.pro. You should understand the difference between these files before deciding which type will best suit your situation. 61 Structural and Thermal Simulation - Help Topic Collection For more information on configuration files and how to create them, see the appropriate area of the Pro/ENGINEER Help Center. To review a list of the configuration options pertinent to Mechanica and read about issues that you may want to consider when developing a configuration file, see Configuration File Options. Setting Environment Variables You may need to set environment variables during installation or to alter a user environment. Therefore, you should know the commands used to set environment variables. The UNIX command syntax depends on the shell environment you are using. Currently, there are three types of shells available—C, Korn, and Bourne shells. If a shell has been changed, it is possible that the env command will not return the correct information. When trying to set an environment variable in these cases, you will get a "Command not found" message. Trying the command for the other shell type usually solves the problem. In order to find out what type of shell you are using, enter the following at the command prompt: env | grep -i shell One of the following lines will be returned: For a C Shell For a Korn Shell For a Bourne Shell shell = /bin/csh shell = /bin/ksh shell = /bin/sh As an example, consider setting the environment variable for MECH_ARCH. The variable setting changes depending upon the platform and shell type. For a C shell, the following syntax defines the environment variable for a Sun system when entered from the command prompt: setenv MECH_ARCH sun4_solaris For a Korn or Bourne shell, the following syntax defines the environment variable for a Sun system when entered from the command prompt: MECH_ARCH=sun4_solaris; export MECH_ARCH The Windows command syntax is the same for all Windows systems. As an example, the following syntax defines MECH_ARCH for a Windows system when entered from the command prompt in an MS-DOS shell: set MECH_ARCH=i486_nt 62 Structural and Thermal Simulation Online Help Getting Help for Mechanica Mechanica provides several types of online documents to meet various needs that might arise in your use of the software. For the most part, you will use the topics found in the online help. Those topics answer questions and provide instructions related to specific menus, commands, procedures, and processes that tie directly to tasks you are performing in the software. In addition to the online help, Mechanica also provides supplemental online documents that you can use to gain a more in-depth understanding of various aspects of the software. For an overview of basic simulation tasks and workflow, Mechanica provides Simulation Advisor. Mechanica documents are written for mechanical engineers and assume a working knowledge of mechanical engineering theory, terminology, and practice. However, you do not need specialized knowledge of design analysis to use either Mechanica software or this documentation. Viewing methods for Mechanica help vary as follows: • • For online help, use the same methods you would use for Pro/ENGINEER. For more information on viewing help for Pro/ENGINEER, see the Pro/ENGINEER Help Center. For Simulation Advisor, see Using Simulation Advisor. Simulation Advisor primarily covers the Structure product. There are several tools that help you navigate through the help system easily. You can use the contents, index, and search functions to help you find specific information, and the hyperlinks inside each help topic to jump to related information. Most online help topics have a "Return to" link at the bottom that links to the topic's parent page or to a previous page. You can also use the browser's Back button to return to a previous topic. Online Help for Mechanica Mechanica's online help provides extensive reference information on each Mechanica menu and command. Help topics also guide you through many of the tasks you need to complete as you work with your models. Online help for Mechanica offers help on the following subjects: • Getting Started with Mechanica — Introduces the Mechanica product line, workflow, operating modes, user interface tools, and online documents. This area of online help also provides planning and modeling considerations and configuration file options. Modeling — Explains all aspects of modeling in Mechanica. • 63 Structural and Thermal Simulation - Help Topic Collection • • Analyses and Design Studies — Details each type of analysis and design study you can run in Mechanica. This area of online help also provides instructions for performing a run. Results — Explains the commands you use to obtain and customize the results of analyses and design studies. Supplemental Online Documents for Mechanica In addition to its online help, Mechanica provides a variety of online documents to help increase the ease, confidence, and success with which you use the software. These supplemental online documents are longer than the help screens. Following is a list of supplemental Mechanica online documents, grouped into sets to meet possible needs that arise in your use of the product. • Using Mechanica o Updates for Mechanica — Contains important information that does not appear elsewhere in the documentation and that you should be aware of before using the current Mechanica release. Also contains descriptions of limitations you may encounter in your use of the software. o Long-Term Limitations — Lists long-term limitations you will encounter when using Mechanica. o Transferring Entities From Integrated Mode to Independent Mode — Describes how to transfer geometry, loads, constraints, and other entities from Mechanica's integrated mode to independent mode. o Icons Used in Mechanica — Illustrates and briefly describes icons that Mechanica uses. This information is relevant mainly to independent mode. o Bibliography — Lists references to books and articles on topics relevant to Mechanica. o Glossary for Mechanica — Contains brief definitions of Mechanica terms. Mechanica Files o Database Considerations — Discusses the Mechanica database, file interactions, Pro/ENGINEER file management commands you can use during Mechanica sessions, and some guidelines for using Mechanica with Pro/INTRALINK or Windchill. o Files Created by Mechanica — Describes files that Mechanica creates. o FEM Neutral Format File — Provides details on the FEM neutral format files used to transfer FEM model information to FEA solvers and Mechanica. Mechanica Background o Understanding Fatigue Analysis — Provides background information on fatigue and describes the methodology used in Mechanica fatigue analysis. o Shell Property Equations — Describes how the mechanical properties of shells are represented mathematically in Mechanica. • • 64 Structural and Thermal Simulation o Verification Guide — Presents a series of problems based on finite element models for which analytic solutions are known, and compares Mechanica results to the textbook results. Simulation Advisor Simulation Advisor presents an overview of basic Mechanica processes, mostly for Structure. It starts with a general workflow and goes through each of the major areas you need to be familiar with as you create your model. You access Simulation Advisor through the Simulation Area top page of the Pro/ENGINEER Help Center. The majority of the Simulation Advisor provides information on the following: • • • • • • • What Mechanica Does — Provides a general workflow for Mechanica. Using Single Parts and Assemblies — Explains how to deal with interfaces between parts in an assembly and make sure you have a consistent system of units. Defining Suitable Geometry — Helps you define the geometry in your model in the best way. Setting Up the Simulation Model — Provides information on assigning material properties, applying loads and other boundary conditions, and controlling solution quality. Simulations You Can Perform — Explains the different types of analysis that you can perform. Running the Solution and Viewing the Results — Gives helpful information on optimizing your computer resources and ensuring the quality of the results you generate. Improving the Design — Provides design optimization techniques. How and when you use Simulation Advisor depends on your individual needs. Simulation Advisor lends itself to a variety of uses. As time allows, take a quick tour through the different areas to familiarize yourself with the overall content. If you need information on such topics as fatigue analysis or family tables or allocating computer resources, just to name a few, Simulation Advisor can provide you with this type of information. Viewing Specifications for Simulation Advisor To view Simulation Advisor, you need to: • Have one of these web browsers available: o o • Internet Explorer 5.0 or higher Mozilla 1.4 Make sure Java, JavaScript, and style sheets are enabled in your browser. 65 Structural and Thermal Simulation - Help Topic Collection In Mozilla, select Edit>Preferences, go to the Advanced category and select Enable Java. Next, select the Scripts & Plugins subcategory and ensure that the Navigator check box is selected. In Internet Explorer select Tools>Internet Options, then do the following: o To enable Java, select the Advanced tab and select the Java JIT Compiler For Virtual Machines Enabled (requires restart) check box under the Java VM heading. To enable style sheets, select the General tab, click the Accessibility button, and make sure the options under Formatting are not selected. o There is no option to turn off JavaScript in Internet Explorer. Using Simulation Advisor Use Simulation Advisor to learn basic Mechanica processes that will help you produce the desired results for your model. You access Simulation Advisor through the Simulation Area top page. Simulation Advisor includes the following navigation tools: • • • Tabs — At the top of the Simulation Advisor window, there are tabs that organize the information into different areas. Click a tab to display the topic list and first page of information for that area. Topic List — On the tabs, Simulation Advisor lists the topics related to the tab's area of information. Click a topic to display it. Hyperlinks — Within each topic there are hyperlinks that take you to related information both in Simulation Advisor and in the Mechanica online help system. Click the hyperlink to access the related information. Note: Hyperlinks to Mechanica help topics require that you have Mozilla or Internet Explorer. For additional information on Simulation Advisor, see: • • Viewing Specifications for Simulation Advisor Troubleshooting Browser Problems Using Online Help When you select the Show Navigation link on an online help file, the navigation pane opens on the left. The navigation pane has three tabs—Contents, Index, and Search. • Contents — View the Contents, which includes all help topics connected to menus or commands, but does not include many lower-level help topics. Click a topic title to display the help topic. 66 Structural and Thermal Simulation The Contents list is hierarchical. Use the + and – symbols next to a book to open or close the list that comes under that book. There are no topics associated with the books. Use the vertical scroll bar to move up and down the Contents list. Use the horizontal scroll bar to move left and right. • Index — View the Index. Type the first few letters of the item you are looking for. The index scrolls down to the appropriate part of the list. To open the topic that goes with an index entry, either double-click the entry or select the entry and select the Display button. • Search — Search the help system for topics that contain one or more keywords that you enter. Type one or more keywords in the search pattern text box. When you click the Find button, a list of topics that contain the keyword appears. To open one of the topics from the search, either double-click the topic you want or click the topic and select the Display button. Searches are not case-sensitive. Use Boolean operators (AND, OR, NOT) to combine search terms. Use wildcards (* or ?) if you also want to see variations of the search term, or enclose the search term in quotation marks if you want to search for an exact phrase. You can also use the hyperlinks inside each help topic to jump to related information. Among other links, most online help topics have a "Return to" link at the bottom. This contains one of the following types of links: • • A link to the topic's parent page. If you arrive at the topic from a different page, use the browser's Back button instead. A link called "previous". This is identical to the browser's Back button. If you need to go back more than one level, use the Back button. Troubleshooting Browser Problems For Simulation Advisor If you already have a valid browser running when you start Simulation Advisor, Mechanica uses that browser. If you do not have a valid browser running, Mechanica checks for a browser in your registry and starts that browser. If you experience regular browser problems, you should: • • Make sure you have one of the browsers listed in Viewing Specifications for Simulation Advisor. Make sure you have set the browser as suggested. 67 Structural and Thermal Simulation - Help Topic Collection To Customize the Mechanica Toolbar To change the buttons displayed on the Mechanica toolbar, follow these steps: 1. Select Tools>Customize Screen. The Customize dialog box appears. 2. Click the Commands tab. 3. Select Mechanica Actions, Mechanica Objects, or Simulation Display from the list of Pro/ENGINEER modules. Mechanica displays the available toolbar buttons under Commands on the right. 4. If you want to add a button to the toolbar, drag it from the Customize dialog box to the toolbar. 5. If you want to remove a button, drag it from the toolbar to any location in the window. To Control Icon Appearance 1. Select View>Simulation Display or click Display dialog box. 2. Click the Settings tab. to open the Simulation Default values display all icons without names and show icons when you spin your model. All load and constraint icons appear in individual colors, and load icons are not scaled or displayed with heads touching. 3. Change any of the default values. 4. Select OK to accept the settings and close the dialog box. To Set Icon Visibilities for Modeling Entities 1. Select View>Simulation Display or click to open the Simulation Display dialog box. 2. Click the Modeling Entities tab. 3. To select all the entities, click the Default button. The default settings for this tab are all accessible items selected. 4. Use or to select all or none of the listed sets. 5. To disable or enable a particular icon type, clear or check a box next to this entity. 6. Select OK to accept the settings and close the dialog box. To Suppress Modeling Entities Through a Family Table 1. In standard mode, select Tools>Family Table. The Family Table dialog box appears. 2. Using the Insert>Instance Row command, create the generic model and as many instances in the family table as you want. 68 Structural and Thermal Simulation 3. Select OK. 4. Verify that you are working in the generic model and click Applications>Mechanica. 5. Select Tools>Family Table. 6. Using the Insert>Columns command and the Model Tree, add the desired modeling entities to the generic model. Mechanica adds each modeling entity to the generic model and the instances. For a modeling entity in each model instance, the Family Table dialog box provides a drop-down menu that you can use to suppress or activate the entity. 7. In each of the model instances, suppress or activate the modeling entities in the modeling entity columns appropriately to what you are planning to simulate with the instance. 8. Select OK. After you create the desired family table instances, you can switch to the instance you want to work with. When you open the instance model in Mechanica, the modeling entities that you suppressed in the family table do not appear in the Model Tree and no associated icons appear in the work area. 9. Use the Windows menu to switch to the desired instance. When the instance model is opened, the modeling entities that you suppressed in the family table get suppressed in the instance model. To Set Icon Visibilities for Loads and Constraints 1. Select View>Simulation Display or click to open the Simulation Display dialog box. 2. Click the Loads/Constraints tab. In Structure, the default settings for this tab are all Structure items selected, all Thermal items clear. The defaults in Thermal are all Thermal items selected and all Structure items clear. 3. Use or to select all or none of the listed sets. 4. To disable or enable a particular icon type, clear or check a box next to this item. 5. Select OK to accept the settings and close the dialog box. 69 Structural and Thermal Simulation - Help Topic Collection To Set Simulation Entity Prehighlighting Filters You can select the simulation entities you want to be prehighlighted by completing these steps: 1. Select Edit>Select>Preferences. The Selection Properties menu appears. All items are selected by default. 2. You can deselect any items that you do not want prehighlighted. 3. Click OK to save your selections. Note: Mechanica does not save prehighlighting settings from one session to the next. To Move the Mechanica Toolbar When you start Mechanica, the toolbar appears beside the graphics window. Follow these steps to change the location: 1. 2. 3. 4. Select Tools>Customize Screen. The Customize dialog box appears. Click the Toolbars tab. Select Mechanica Actions, Mechanica Objects, and Simulation Display. From the adjacent list, select one of the following options: o o o Top Right Left The Mechanica toolbar appears in the location you specified. 5. Click OK to accept the change, or Cancel to ignore the change. Optimizing a Model (Native Mode) After you define design controls, Mechanica can perform local and global sensitivity studies that show you how your model behaves as the design controls change its shape and properties. The information from these studies enables you to define your optimization so that it includes only the design controls that have a strong effect on the goals you are trying to achieve. When you determine which design controls you want to include in the optimization, you can define a Mechanica optimization study that will automatically find the design that best meets your goals. 70 Structural and Thermal Simulation The following is a list of the tasks that are part of the optimization process: • • • Defining standard, sensitivity, and optimization studies — You need to define the type of study (standard, sensitivity, or optimization) that you want Mechanica to perform and indicate the study’s parameters and goals. Running the studies — You instruct Mechanica to run your study. Reviewing the results of the studies — You evaluate the results of the run to determine how your model behaved. The nature of your evaluation differs depending on the type of study you ran. The following is a summary of the factors you want to focus on when reviewing results for the different types of studies: o Standard studies — Look at the results to find out how your model behaved during a single analysis or combination of analyses. If you used a particular parameter setting for a standard design study, you can use the results to determine how your model behaved at that parameter setting. These results can help you determine the feasibility of a design. They can also help you evaluate the effect of slightly modifying an optimized shape to bring it within manufacturing tolerances. Sensitivity studies — Look at the results to find out which design controls had an effect on your goals. Additionally, use the results to determine appropriate starting points and range limits for your parameters during optimization. o Optimization studies — Look at the results to see the optimized shape and determine whether the final shape is acceptable. Accepting the optimized design — If you want to go forward with your model's optimized shape instead of the original shape, you need to accept the optimized design. When you accept an optimized design, Mechanica updates your original Pro/ENGINEER model to reflect any shape changes. o • Developing a Model (Native Mode) Before you can analyze or optimize a model, you must develop it. In developing a model, you complete a number of different tasks—from creating the part geometry to adding the characteristics, properties, and definitions that transform the part into a Mechanica model. The following is a list of the tasks you complete: • • Planning and building your model — You need to build your model geometry. In integrated mode, you build your geometry in Pro/ENGINEER using methods that promote Mechanica modeling and analysis. Simplifying your model — You can speed up your solution times and ease your simulation modeling tasks if you work with a simplified model. You can use various techniques to simplify your model within Pro/ENGINEER. Defining a system of units for your model — You need to define a system of units for your model. You can select a predefined system of units or create a custom system of units. Defining modeling prerequisites for your model — You can define a variety of modeling prerequisites in Mechanica. For example, you can define 71 • • Structural and Thermal Simulation - Help Topic Collection coordinate systems for your model in Mechanica. Mechanica uses coordinate systems to help determine the direction and placement of a load, the orientation of a material, and for certain types of constraints and measures. You can also define datum geometry, surface regions, and volume regions. These features give you a more versatile approach to placing loads, constraints, measures, and idealizations. • Defining modeling entities for your model — You can add the following modeling entities: o Materials — You need to define the material or materials your model will be made of. You can also define material orientations. o Constraints — For Structure, you need to define the extent to which your model can move in space. For Thermal, you need to define the convection conditions and prescribed temperatures that act as boundary conditions for the model. o Loads — For Structure, you need to define the external forces that will act on your model relative to its constraints. For Thermal, you need to define the heat loads that act on your model. Defining idealizations — Mechanica treats Pro/ENGINEER parts and assemblies as solid models. As an alternative, you can define your model as a shell or beam model. Shell and beam modeling can reduce run times and disk space requirements. Shell modeling is appropriate for parts that are thin in one dimension, such as sheet metal parts. Beam modeling is a good choice for parts that are thin in two dimensions, such as rods or struts. With beam modeling, you can define your entire model as a set of beams, or you can define beams for a portion of the model and use solids or shells for the remainder. You can also add specialized idealizations such as masses and springs. These entities enable you to model concentrated masses and general six-degree-offreedom spring connections. • Defining connections — You can define various connections in your model. For example, you can create contact regions for your model or add spot welds. Connections tell Mechanica where the different parts of your model contact as well as describe the nature of that contact. Mechanica uses this information to develop an appropriate mesh. Defining measures — You can define custom measures to obtain result values for specific points on your model or to obtain response information for vibration analyses. Checking the mesh — Mechanica automatically creates a model mesh as part of analysis. However, you can use AutoGEM, Mechanica's automatic mesh creation facility, to check this mesh prior to run time. If, when you examine the AutoGEM mesh, you feel there may be problems with certain areas in your model, you can use AutoGEM to refine or correct the mesh. • • • 72 Structural and Thermal Simulation Defining Design Changes (Native Mode) After you review the results of your analysis, you can establish which aspects of your model you want Mechanica to alter as it searches for the optimal design. The items you decide to modify are called design controls, or design parameters. Design parameters change your model’s shape and properties. When defining model changes, you complete the following tasks: • Defining design controls — You need to select the dimensions and properties that you want Mechanica to change during sensitivity and optimization studies. As part of this step, you also need to specify the ranges within which these changes can occur. Reviewing and modifying shape changes — You need to preview the effect of shape changes on your model, either by looking at the model shape at particular dimension settings or by animating the model so you can see progressive shape changes. • When you preview your shape changes, you may find that some design controls do not behave as you want them to. In this case, you need to modify the design control. You may also need to alter or define Pro/ENGINEER relations to help control the shape change. Analyzing a Model (Native Mode) After you develop your model, Mechanica can analyze its behavior under the conditions you defined when you added constraints and loads. The following is a list of the tasks you complete: • • Defining the analysis — You need to define the type of analysis you want Mechanica to perform and indicate the analysis conditions. Running the analysis — You need to instruct Mechanica to run the analysis. Note: Before you run an analysis, you should verify Mechanica's run settings. Run settings determine which solver the engine uses, how much memory you want to allocate, and so forth. • Reviewing the results of the analysis — You need to evaluate the results of the run to determine how your model behaved. Search Tool Use the Edit>Find command to access the search tool that allows you to search for simulation entities in a model. When you select the Edit>Find command, the Search Tool dialog box appears. This dialog box includes four tabs—Attributes, History, Status, and Geometry. Mechanica uses only specific rules on the Attributes and Status tabs to perform the search for simulation entities. 73 Structural and Thermal Simulation - Help Topic Collection The search tool allows you to specify the search criteria based on the type of the model. The supported types of models are 2D, 3D, Structure, and Thermal in native and FEM modes. Additionally, the search tool allows you to define rules to build and save queries. You save the search queries by defining a new layer in the model. Defining a layer while saving a query allows you to group certain simulation entities on a layer. Use the Search Tool dialog box to: • • • • • Specify rule classes to search by name, type, property, or layer of the simulation entities. Specify search criteria by defining the comparison, category or value of the simulation entities. Define a layer to organize simulation entities. Build a query by defining rules and operations for the query. Save a query based on the defined rules. In Mechanica, you can search for the following objects in a model: • • • • • • • • • • Structural loads Thermal loads Structural constraints Thermal boundary conditions Idealizations Connections Simulation measures Material assignments AutoGEM Controls FEM mesh controls After you apply the rules and specify the search criteria, Mechanica highlights and displays the search results. Controlling Mesh Display Using the Simulation Display dialog box, you can control various aspects of the mesh display enabling you to: • • • view the elements in a mesh in a larger model more clearly view shell elements in a mesh with zero or actual thickness specify display refinement for mesh viewing Use the Mesh Display area on the Mesh tab of the Simulation Display dialog box to control the appearance of a mesh. This area includes: • Shrink Elements — Shrink elements in a mesh to clearly view their 3D shapes. Enter a value in the spin box to shrink the elements by the given percentage. This option is primarily useful for large models or models with meshing problems, where shrinking the elements can help you identify poor element shapes or locate problem areas. Display Shells with Zero Thickness — Display shells in a mesh with zero thickness. This option is available only if you select the Shells option on the Mesh Entities area. • 74 Structural and Thermal Simulation Selecting this option ensures a quicker mesh display because Mechanica displays the elements as a 2D rendition, which provides an accurate footprint of the mesh while saving the time required for a 3D rendition. To display shells with the actual thickness, clear this check box. Displaying actual thickness lets you make sure that shells in a mesh are correctly defined and have the intended thickness. Note that if a shell is made up of layers, Mechanica displays the shell elements with the total shell thickness and not with the individual layer thicknesses. Display Quality — Change the display quality of a mesh for better viewing of the curved elements. Select Coarse, Medium, or Fine where Fine is the closest approximation to the original shape of the curved element. Mechanica displays a coarse quality mesh by default. Mechanica enhances the display quality by improving the tesselation of the nonlinear curved elements in a mesh. Therefore, selecting Medium or Fine may not be effective for models with linear shaped elements or for models with highly refined meshes, where the curved elements are already very small. The only time you may need a Medium or Fine setting for a refined mesh is if you are zooming in closely on the curved elements. You can also set the initial state of your mesh display through the Simulation Display Mesh options in the config.pro file. • Comparing Mirror and Cyclic Symmetry Here is a summary of how mirror symmetry differs from cyclic symmetry. Mirror Symmetry Useful for symmetry problems with relatively simple geometric profiles. You reduce the geometry by placing constraints along planes of reflective symmetry. Each plane, in effect, reduces the model or model segment by one half. If you choose to use cuts to isolate the symmetric segment, the cuts must be planar. You must explicitly define separate constraints for each unique plane of symmetry to indicate that the segment is Cyclic Symmetry Useful for symmetric problems with complex geometry. • • • • You reduce the geometry by finding the smallest symmetric segment and applying cuts to isolate this segment. • • Cuts you use to isolate the symmetric segment need not be planar. • • You define a single cyclic symmetry constraint for both cut surfaces or, in the case of shells, both cut curves. 75 Structural and Thermal Simulation - Help Topic Collection connected to the parent model. Mechanica interprets the constraint to mean that the model is a symmetric segment. • You can define only one cyclic symmetry constraint for a single model. • You can define more than one mirror symmetry constraints for a single model. The mirror symmetry planes must be parallel or orthogonal to each other. Defining an Analysis (FEM Mode) After you develop your model, you can define an analysis that Mechanica can use with the FEA solver you select. The analysis definition that you create indicates the type of analysis you want and tells the FEA solver which loads, constraints, and so forth you want considered. The following is a list of the tasks you complete. • • Selecting the analysis type — You need to select the type of analysis— structural, modal, or thermal—that you want Mechanica to perform. Defining the analysis conditions — You need to indicate the loads and constraints that you want the FEA solver to consider for the run. For modal analysis, you need to indicate the modes and frequency range you want to solve for. For some models and in some situations, you may be primarily interested in generating a mesh to use with an offline solver rather than running an FEM analysis within Mechanica. In this case, you do not need to define an analysis. Solving a Model (FEM Mode) After you mesh your model, you can solve it using an FEA solver and then, in most cases, review the results within Mechanica. Following is a list of the tasks you complete. • Exporting and reviewing the model — You export and review a model to examine its mesh quality, how loads and constraints apply to the mesh, verify materials, and so forth. We recommend this step before using the exported deck with an outside solver or running a FEM analysis within Mechanica. While this step is optional, it provides you the advantage of reviewing the mesh and model to ensure that you are satisfied before committing to a lengthier solver run. Running an analysis — You run an analysis by outputting your model, including one or more analysis definitions, to one of the supported FEA solvers or by starting a supported solver from within Mechanica. FEA solvers create a mathematical approximation of the model, its boundary conditions, and its loads. It then analyzes the structural or thermal integrity of 76 • Structural and Thermal Simulation the model based on the analysis you specified and the way you defined the simulation features, materials, and mesh. In FEM mode, you can perform online runs with the NASTRAN and ANSYS solvers from within Mechanica, or run either of these solvers in the background. FEM mode also enables you to output NASTRAN or ANSYS decks for use outside Mechanica or output the model as a neutral file. • Reviewing results — After you run your analyses, you can import the solved model into Mechanica's postprocessor and review the results. You can examine such graphical renditions of model behavior as fringe plots, animations, and graphs, define FEA parameters for your results, review analysis statistics, and look at results information at particular points in your model. FEM Mode FEM mode enables you to create a mathematical model based on a Pro/ENGINEER part or assembly, then analyze that part using any of several third-party finite element solvers such as NASTRAN, ANSYS, and so forth. The activities you perform in FEM mode are similar to those you perform in native mode. You complete such tasks as adding modeling entities such as loads, constraints, and so forth as well as defining analyses. However, unlike native mode, you must explicitly create a mesh for your model instead of having Mechanica perform this step automatically at run time. You also need to explicitly output your model to one of the supported FEA solvers, which analyzes the structural or thermal integrity of the model based on how you set up the simulation. Creating a Mesh (FEM Mode) After you define analyses for your model, you create a mesh that the FEA solver uses to mathematically approximate your model's behavior. Mechanica's FEM mode enables you to create a variety of mesh types and features. Following is a list of the tasks you complete. • Defining mesh controls — You can control the way Mechanica creates the mesh in a number of ways. For example, you can limit element size and define points and curves in your model so that Mechanica adds nodes at these locations. You can control node ID ranges or instruct Mechanica to use a specific coordinate system when creating the mesh. You typically define mesh controls before you create the mesh, but you may find that you want to impose additional controls after you review the mesh. Creating a mesh — When you instruct Mechanica to create a FEM mesh, it subdivides the model into a set of smaller, simpler, interconnected components called finite elements used by FEA solvers. Finite elements differ from the geometric elements that Mechanica creates for its native P-code solver in that finite elements have a more regular, consistent shape. For FEM meshes, you can create solid, shell, and bar meshes, or a mesh that incorporates all three element types. 77 • Structural and Thermal Simulation - Help Topic Collection • Reviewing and refining a mesh — After you mesh your model, you can examine the element quality by checking such characteristics as aspect ratio, warp angle, edge angle, skew, and so forth. You can also review more general aspects of the mesh to determine its quality, the connectivity of its nodes, whether it has sufficient granularity, and so forth. If you are not satisfied with the mesh, you can improve it by: o asking the FEM mesher to optimize the mesh o using the information you gathered during your mesh review to create additional mesh controls. With new mesh controls in place, you then remesh the model. Developing a Model (FEM Mode) Before you can analyze a model in FEM mode, you must develop it. In developing a model, you complete a number of different tasks—from creating the part geometry to adding the characteristics, properties, and definitions that transform the part into a Mechanica model. The following is a list of the tasks you complete: • • Planning and building your part — You need to build your model geometry. You build your geometry in Pro/ENGINEER using methods that promote easy simulation modeling and improve analysis times. Simplifying your model — You can speed up your solution times and ease your simulation modeling tasks if you work with a simplified model. Pro/ENGINEER provides various techniques that you can use to simplify your model before or during your Mechanica session. Defining a system of units for your model — You need to define a system of units for your model. You can select a predefined system of units or create a custom system of units. Defining modeling prerequisites for your model — You can define a variety of modeling prerequisites in Mechanica. For example, you can define coordinate systems for your model. Mechanica uses coordinate systems to help determine the direction and placement of a load, the orientation of a material, and for certain types of constraints. You can also define datum geometry, surface regions, and volume regions. These features give you a more versatile approach to placing loads, constraints, connections, and idealizations. • Defining modeling entities for your model — You can add the following modeling entities: o Materials — You need to define the material or materials that your model will be made of. You can also define material orientations. o Constraints — For Structure, you need to define the extent to which your model can move in space. For Thermal, you need to define the convection conditions and prescribed temperatures that act as boundary conditions for the model. o Loads — For Structure, you need to define the external forces that act on your model relative to its constraints. For Thermal, you need to define the heat loads that act on your model. Defining idealizations — Mechanica typically treats Pro/ENGINEER parts and assemblies as solid models. Some models, or portions of a model, may • • • 78 Structural and Thermal Simulation be better suited for other types of meshes—shell or bar meshes, for example. To accommodate this type of model, Mechanica provides you with the ability to create shell or beam idealizations that the software will include when you mesh the model. You can also add specialized idealizations such as masses, gaps, and springs. These entities enable you to model concentrated masses, enforced gaps between geometry, and general six-degree-of-freedom spring connections between points. • Defining connections — You can define various connections in your model. For example, you can create contact regions for your model or add spot welds. Connections tell Mechanica where the different parts of your model contact as well as describe the nature of that contact. Mechanica uses this information to develop an appropriate mesh. Tolerance Report Use the Info>Tolerance Report command if you experience problems meshing an assembly model in either native mode or FEM mode. This command displays a report that lists the tolerance values for all assembly components whose model tolerance contributes to the global tolerance for the assembly. If the assembly contains entities such as quilts or beams, the report includes the tolerance value for the assembly itself. The report includes all those components that have geometry, and is arranged in descending order with components that have the highest tolerance values listed first. To better understand how to use the values in this report, you need background information on model accuracy, both relative and absolute. Tolerance, as reported by Mechanica, is calculated in a manner similar to absolute accuracy. However, the calculated values are somewhat different. You use the Mechanica Info>Tolerance Report command to compare the tolerance—and, in effect, the accuracy—of assembly components if your assembly mesh fails. For Mechanica to mesh the assembly successfully, these values must be very close to each other. When reviewing a tolerance report, look for significant differences in the tolerance values of components, the assembly as compared to the components, and so forth. Although it can vary depending on the assembly, a significant difference is generally considered to be a difference in the decimal order of magnitude. For example, the difference in two tolerance values of 0.274 and 0.513 would not typically be significant, but the difference between 2.874 and 0.513 probably would be. If you notice significant differences in the tolerance values reported by Mechanica, return to Pro/ENGINEER and use the Edit>Setup>Accuracy command to decrease the relative or absolute accuracy value for the component whose tolerance value is too high. If you want to change the accuracy value for the top-level assembly, work in assembly mode. If you want to change the accuracy value for one component, work in part mode. When working with the Accuracy command, be aware that a decrease in the accuracy value actually represents an increase in the accuracy, or precision, of the geometry. After you lower the accuracy value, the tolerance value of the component will decrease as well. For more information on accuracy, see the Part Modeling area of the Pro/ENGINEER Help Center. 79 Structural and Thermal Simulation - Help Topic Collection Suppression and Family Tables You manage modeling entities through the Suppress command or through family table instances. The Suppress command and the family table instance methods are useful in slightly different situations. Here is an overview: • Suppress command — Use the Edit>Suppress command to suppress specific modeling entities. Mechanica hides suppressed entities in the model display and ignores them during meshing and analysis. You can reactivate any suppressed modeling entity through the Edit>Resume command. Using the Suppress command is handy if you want to suppress modeling entities on the fly, or if you do not want the overhead of creating family table instances. Optionally, you can Suppress or Resume by right-clicking the specific modeling entity from the Model Tree. Modeling features cannot be suppressed or resumed for example, Datum Curves. Note: To display all the modeling entities in a Model Tree, you must ensure that you select the Suppressed Objects check box on the Model Tree Items dialog box that you access through the Settings>Tree Filters command. • Creation of family table instances — Use the Tools>Family Table command to create separate instances of the simulation model, each with a different set of suppressed modeling entities. This technique is useful if you plan to solve several different types of simulation problems for a single model and want a slightly different set of modeling entities for simulation problem. The advantage of this technique is that you can set up each instance to solve a particular problem. Each instance acts as a record of the modeling entity state required to solve the associated simulation problem. Use of family table instances can save substantial model adjustment overhead for large, complex models, but requires preplanning and additional setup time. To setup family table instances for simulation, you begin in standard mode, where you create one or more family table instances for your model. You create one instance for each problem that requires a unique set of modeling entities. After you create family table instances, you enter Mechanica while in the generic version of the model. You then add modeling entities by inserting family table columns and selecting from the Model Tree. After you have all the desired modeling entity columns in place, you can work through the model instances, suppressing and activating individual modeling entities for each instance. Having now defined the simulation family table, you can now decide which problem you want to solve and open the associated model instance, working through the problem in that instance only. When working in a family table instance, be aware that Mechanica promotes any modeling entity you create within an instance to the generic model. However, the modeling entity appears as suppressed, and you must resume the entity if you want to use it in the generic model or any of the other instances. 80 Structural and Thermal Simulation Note: When you are working in Mechanica, you can only add simulation modeling entities to the family table. You cannot add Pro/ENGINEER values, features, components, or parameters. You also cannot create new family table instances while you work in Mechanica. Simulation Model Use the Info>Simulation Model command to view information about your model in Mechanica. When you select this command, an information window appears with your model's name and model type, as well as summaries of the materials, idealizations, connections, loads, and constraints in your model. For example, here is an information window entry for a spring: Spring "Spring1" Reference: Feature of Points (Model COMPONENT_NAME) — Edge Type: Advanced Y direction: Cartesian CSYS — "WCS" Spring Property "SpringProp1" You can edit and save the information window text as a .inf file. Use the following commands on the information window toolbar to manipulate the information: • File o o o Edit o Save — Saves the file as model_name.inf. Save As — The Save A Copy dialog box appears. Enter a name for the file and browse to find a directory. Close — Closes the dialog box. Edit Mode — Activates the commands Cut, Copy, Paste, and Delete Line. Use these commands to edit the text. To insert text, move the red mark to the desired location and enter text. Cut — Removes the selected text. Use the cursor to highlight text, and click this command. Copy — Moves the selected text to a buffer. Use the cursor to highlight text, and click this command. Paste — Adds copied text from the buffer to the cursor location. Delete Line — Removes the line of text at the cursor location. Search — Opens the Search dialog box. Enter a search term and click Search. The software highlights any instances of the search term it finds in the information window. • o o o o o • View o Line Number — Turn on or off the display of line numbers. This command is not active in edit mode. You can also display the information window by using the shortcut menu in the Model Tree. 81 Structural and Thermal Simulation - Help Topic Collection Displaying the Mesh Model After you mesh a FEM model, Mechanica treats the model as though it has two separate objects to display—a geometry model and a mesh model. The geometry model includes the geometry itself as well as the properties and entities associated with the geometry. The mesh model includes the mesh as well as any attributes of the mesh. The following Simulation Display options control how Mechanica displays the geometry and mesh models: • • Mesh and Model check box on the Mesh tab. No Mesh option from the Mesh Display Mode drop-down menu You can use the Mesh And Model check box on the Mesh tab of the Simulation Display dialog box to display both the geometry and mesh models while you are working with functionality in which only the mesh model is active. This prevents portions of your model from disappearing from the screen if you remove a mesh. Here are the situations in which only the mesh model is active: • • • • • • • Immediately after you create a mesh When you are refining a mesh using Mesh>Improve When you are reviewing a mesh using Mesh>Review When you are deleting a mesh using Mesh>Erase When you are performing mesh operations using Mesh>Operation When you are running an analysis When you are viewing results You use the No Mesh option to turn off the mesh line display. Regardless of how you set the Mesh and Model check box, you can only use the No Mesh option when both the geometry and mesh models are active in the overall model—for example, when you add properties, loads, constraints, and so forth. You cannot use the No Mesh option if only the mesh model is active. Mechanica Mass Properties Use the Info>Mechanica Mass Properties command to view the Mechanica mass and moments of inertia for your model. Mechanica calculates mass properties for your model based on material properties, so you must assign a material to your model before you can view mass properties. This command is not available in FEM mode. When you select this command in assembly mode, Mechanica prompts you to select a body. In part or assembly mode, Mechanica also prompts you to select or create a reference point or accept the body's center of mass as the reference point. When you complete your selections, the Pro/ENGINEER embedded browser opens with the following information: • 82 Coordinates of the selected reference point in the UCS Structural and Thermal Simulation • • • • Mass of the selected body Center of mass relative to the selected reference point in the UCS Moments and products of inertia about the reference point and relative to UCS Principal moments of inertia about the center of mass and principal axes relative to WCS Example: Dependent Movement in Patterned Features Some part-building techniques, such as patterning, can link the movements of multiple parts. In some cases, this effect may be exactly what you want during an optimization—for example, you may need to retain an established distance between two geometric entities. In other cases, linked movement may cause undesirable shape changes. For instance, one way to add the two holes to the shelf plate is to build the second hole as an identical pattern of the first: When you pattern the holes in this way, the surface placement of hole 2 is tied to hole 1 through the dimensioning scheme. If you took this approach, and then assigned a horizontal translation design parameter for hole 1, Mechanica would move hole 2 along with hole 1. Depending on the range of movement you defined for hole 1, you could encounter unexpected topology conflicts between hole 2 and the left surface of the plate, as shown below: 83 Structural and Thermal Simulation - Help Topic Collection To move hole 2 independently, you would define a translation design parameter for hole 2. However, in this case, all movement would be based on the position of hole 1, which would also be dynamic. When a Nonessential Feature Causes Unexpected Model Behavior Changes Some features that appear cosmetic can have an effect on the way a part behaves. As a simple example, a round that blends a horizontal and vertical surface performs the cosmetic function of smoothing the join between the surfaces. More importantly, however, a round can help distribute a force load applied to one of the surfaces so the stresses where the two surfaces join become finite and acceptable. If you suppressed the round, Mechanica's analysis of the load would be inaccurate due to the fact that the round was bearing part of the load. Further, the model would now contain a high stress concentration that might distort the results of the analysis. Mechanica Fatigue Advisor When a model undergoes repeated cycles of loading and unloading, it can fail even if the stresses are below safe values for static, constant load levels. The mechanism underlying this class of failure is known as fatigue, and studies of the fatigue performance are commonly known as durability assessments. Fatigue Advisor allows you to predict and improve the fatigue performance of your designs early in the product life-cycle, helping reduce design cost. Fatigue Advisor uses fatigue technology supplied in partnership with nCode International, a world leader in durability software. Fatigue Advisor works entirely within Mechanica Structure. You simply specify an existing static analysis, then define the material properties and loading history along with the required design life for the study. You can either use the material library and load history generator included in the software or import this information. Fatigue Advisor calculates the following results quantities: • • • • Life — Determines the predicted cycles to failure. Damage — Measures percentage of damage due to loading. Factor of safety — Estimates the factor of safety based upon predicted failure. Confidence of life — Measures the reliability of the results. You can define and review these results using standard Mechanica visualization tools including fringes, contours, and graphs. In addition, you can define and track local and global measures of the results quantities for sensitivity and optimization design studies. You can create parametric geometry models, assign a permissible range to each parameter, and specify design goals and performance limits. 84 Structural and Thermal Simulation Example: Avoiding Interference In designing parts, be sure to avoid creating features that may interfere with each other during a shape change. For example, if your part includes two perpendicular bolt holes as shown below, avoid moving the bolt holes so far that they interfere with each other: In this case, if the design parameters you create to translate hole 1 and hole 2 have too large a range, Mechanica may optimize the shape so that the bolt holes are in conflict, and you could no longer place both bolts. When a Nonessential Feature Provides Hidden Benefits Although they may not play a central role in the function of a part, some features provide optimization benefits if included in the feature set that Mechanica studies. For instance, a round on the edge of a part may have a purely cosmetic function in terms of how the model bears a load. However, if one of your design goals is to reduce the mass of the part, increasing the radius of the edge round would help decrease the total mass. If you suppress the round, Mechanica would be unable to optimize the round's radius. Therefore, despite the fact that the edge round is not crucial to the part's behavior, you would want to keep the edge round as an unsuppressed feature so that you could define a design parameter. 85 Structural and Thermal Simulation - Help Topic Collection Example: Using a Simplified Part Simplifying your parts means removing any feature or geometry that is not significant to the analysis you plan to perform. To understand this principle more clearly, consider the following example of a proposed shelf bracket design: This bracket is made of steel and supports a bookshelf that rests on two rods. The bracket ears and vertical face slide into a die-cast slot in the shelf post. Note that the support holes accept a rod with a predetermined diameter. Looking at the prior example, you can omit the following two items from your initial design: • • the rear plate, provided it is stiff enough not to affect the analysis results the rounds If you leave these items out of your initial design, the part you prepared for Mechanica would resemble the following: As you can see, all nonessential areas of the design are gone. Only the portion you want to analyze or optimize remains. At this point, you can perform a complete Mechanica analysis, sensitivity study, and optimization for your part. 86 Structural and Thermal Simulation After Mechanica develops the optimized shape for this part, you can add the rear plate and rounds. To ensure that the part is still valid, always return to Mechanica for a standard analysis of the complete part. FEM Mesh Display Buttons For fast access to the FEM mesh display controls, Mechanica provides these buttons on the menu bar: Button Action/Name No Mesh — Removes mesh lines from your model. The mesh remains intact, but does not appear on your screen. Wireframe — Turns geometry lines white and element lines yellow. The software displays all elements with boundary faces. Hidden Line — Turns visible geometry lines white and element lines on visible surfaces yellow. Hidden geometry and hidden element edges are gray. The software displays all elements with boundary faces. No Hidden — Turns visible geometry lines white and external, visible surfaces of elements yellow. The software does not display hidden geometry and hidden element edges. Shaded — Turns visible geometry lines red and external, visible edges of elements blue. The software does not display hidden geometry and hidden element edges. These buttons become available only when you work in FEM mode. Example: Modeling Specialized Loads with a Cylindrical Coordinate System You can use user-defined coordinate systems to apply specialized loads, such as loads with an unusual force profile. For example, let us say that you want to find out how the plate below reacts to a nonuniform radial force applied to only a 120 segment of the hole, as though a rod smaller than the radius of the hole were pulling outward against the far surface of the hole. 87 Structural and Thermal Simulation - Help Topic Collection To accomplish this, you could create a specialized load as a function of a cylindrical coordinate system, as follows: In this case, you would create a cylindrical coordinate system as shown above. You would then create a force-per-unit-area load based on the following symbolic function: if(theta>=–pi/3&&theta<=pi/3,cos(theta),0) The load resulting from this function has a sinusoidal profile, with the load at its greatest where T=0. The load tapers symmetrically about T=0, reaching a 0 force at T=60 and T=–60. This load profile is similar to that of a bearing load. However, Mechanica's bearing load always applies to a 180 segment, while this load applies to a 120 segment. Controlling FEM Mesh Display Use the Mesh Display Mode option list on the Mesh tab of the Simulation Display dialog box to control the appearance of a mesh generated in FEM mode. The option list includes: • No Mesh — No mesh lines are visible, and the software displays only the model geometry. Use this display type if you want to simplify the appearance of your model so you can focus solely on the geometry. This is particularly handy as you add loads, boundary conditions, and other properties to the geometry. Note: This option is not available when Mechanica is displaying the mesh model only. • Wireframe — Geometry lines are white and element lines are yellow. The software displays all elements with boundary faces. For solid models, this display type has the most complex appearance. 88 Structural and Thermal Simulation • • • Hidden Line — Visible geometry lines are white and element lines on visible surfaces are yellow. Hidden geometry and hidden element edges are gray. The software displays all elements with boundary faces. No Hidden — Visible geometry lines are white and external, visible surfaces of elements are yellow. The software does not display hidden geometry and hidden element edges. For solid models, this display type has the simplest appearance. Shading — Visible geometry lines are red and external, visible edges of elements are blue. The software does not display hidden geometry and hidden element edges. Be aware that, if you customize the colors you use for shading, the Shading option may display element lines using different colors. If you are displaying your model geometry as shaded and you select the Shading mesh display option, Mechanica retains geometry shading. However, instead of shading the elements as well, the software renders them as outlines on the surface of the shaded geometry. To create the model appearance you want, you can use the mesh display options in combination with the geometry display buttons always present on the Pro/ENGINEER menu bar. For example, you can set the geometry of your model to a Shaded display and the mesh to a No Hidden display. This renders a geometrically accurate, realistic-looking model with a simple element overlay. The Wireframe, Hidden Line, and No Hidden settings are primarily useful for solid and mixed models. For shell and midsurface models, all these settings look similar because shell elements have no displayed depth. Additionally, if you shade the geometry of your model, you will be able to see the element display more easily if you ensure that the model color has some transparency. As an alternative to using the option list to change mesh visibilities, you can use the mesh display buttons on the menu bar. You can also set the initial state of your mesh display through the sim_display_mesh_mode config.pro option. 89 Structural and Thermal Simulation - Help Topic Collection Example: Pre-planning for Shape Changes In planning for shape change, you may need to build your parts differently than you might normally build them in Pro/ENGINEER. To understand this principle more clearly, consider the following example of a proposed shelf bracket design: This bracket is made of steel and supports a bookshelf that rests on two rods. The bracket ears and vertical face slide into a die-cast slot in the shelf post. Note that the support holes accept a rod with a predetermined diameter. If you were trying to determine the best design for this part, you would probably want to optimize the shape for the lowest mass that would support a specified weight. In this case, you might want to change the following aspects of the design: • • • • the the the the angle of curve a length of the part thickness of the part placement of the rod support holes However, due to external restrictions like the support rod diameter, you cannot change the following three aspects of the design: • • • the diameter of the rod support hole the shape and dimensions of the bracket ears the overall height of the part If you had no interest in optimizing this part, you might design the bracket as a single plate with a uniform thickness and treat the body of the plate as a single Pro/ENGINEER feature. However, because you plan to optimize for mass, you want Mechanica to be able to change any aspect of the design that reduces the mass. This objective can affect the way you develop your part in Pro/ENGINEER. For example, one of the aspects directly tied to mass is part thickness. Because the bracket ear shape and part height cannot change, you cannot alter the part thickness if you develop the bracket as a single plate. Instead, you might choose to treat the 90 Structural and Thermal Simulation body of the plate as two separate features—a rear plate and a shelf plate, as shown below: This approach lets you maintain a predefined thickness for the rear plate while allowing Mechanica to vary the thickness of the shelf plate. SIM SELECT Menu Use this menu to specify what you are going to select on your model. This menu appears when you are defining new shells, masses, beams, springs, gaps, constraints, loads, and so forth. Depending on which entity you are creating, different options appear on the menu. • • • • • • • • • • • Select — Select a geometric reference for the location of the entity you are placing on your model. Depending on the type of entity you are adding, this can be a point, curve, or surface, or any of several other reference types. Individual — Select an individual surface on the model. Surf Options — Select the surface that you want using advanced surface selection functionality to indicate the type of surfaces you want to include or exclude. Part Boundary — Select the boundary surfaces of the model. Box Select — Select multiple geometric entities by left-clicking and dragging your mouse to rubber-band the entities. Quilts — When defining shells only, use this option to select a whole quilt. Fix Normals — When defining shells and pressure loads, use this option to fix the normals of specified quilt surfaces. Flip Normals — When defining shells and pressure loads, use this option to flip the normals of specified quilt surfaces. Single — Select a single datum point on your model. Feature — Select a feature of datum points on your model. Pattern — Select a pattern of datum points on your model. 91 Structural and Thermal Simulation - Help Topic Collection Object Action Shortcut Menu When you right-click simulation entities in the Model Tree or a prehighlighted icon in the model, a shortcut menu appears containing some or all of the following commands, depending on the entity you select: • • • • • • • • Promote — Move the selected datum simulation feature into Pro/ENGINEER so that it is permanently visible there. Delete — Delete the selected entity from your model. Edit Definition — Open the appropriate menus or dialog boxes so you can change the definition of the simulation entity or feature. Edit — Display simulation feature dimensions so that you can modify feature geometry. Edit References — Open the appropriate menus or dialog boxes so that you can reroute the selected entity. Rename — Rename a simulation entity or feature. Suppress — Suppress a simulation entity or feature. Info — Open a window that displays information about the selected entity or, depending on the situation, open another shortcut menu displaying these commands: o Simulation Model Info — Open a window that displays information about the model's simulation entities. o Model Info — Open a window that displays information about the model's units, features, and, if you have assigned a material in Pro/ENGINEER, the material name. Copy — Copy a load set, constraint set, boundary condition set, or measure, creating an identical set or measure that bears a new name. • Other commands general to Pro/ENGINEER, such as Rehighlight, Show Selection Bin, and so forth may appear on the object action menu. For information on these commands, search the Fundamentals and Part Modeling areas of the Pro/ENGINEER Help Center. Methods of Simplifying Your Model You can use a variety of techniques to simplify your model, including: • suppressing features that are not germane to the analysis. You can make this process easier if you use these techniques: o Create the simulation model using a family table instance of the Pro/ENGINEER model that suppresses the features not critical to the analysis. o Place features that you want to suppress or resume for a particular analysis on a layer. You can then use the commands on the Layers dialog box to control which features the analysis includes. Access the Layers dialog box by selecting the Show>Layers Tree command on the Model Tree, or by clicking on the Pro/ENGINEER toolbar. using simplified representations of your model when appropriate. Simplified representations give you a greater degree of modeling freedom while preserving your original model. • 92 Structural and Thermal Simulation • • • • modeling thin features with beams and shells rather than as solids. This simplifies the model from the solver's perspective, greatly reducing model size, disk usage, RAM requirements, and analysis times. aligning edges and surfaces that are nearly aligned in the part or assembly using cut features to remove portions of the model that are not pertinent to the analysis using cut features to reduce the model to its symmetric section for models that exhibit both geometric symmetry and modeling symmetry (symmetric loads and constraints) Customizing the Mechanica Toolbar When you select Tools>Customize Screen in standard mode, the Customize dialog box appears. Use the Commands tab of the Customize dialog box to add buttons to or remove them from the Mechanica toolbar. You can use the following items: • • • • Categories — Select a toolbar or menu. Commands — The software displays the buttons available for the selected toolbar or menu. Description — Click to get a brief description of a selected button. Click the message box to return to the Customize dialog box. Modify Selection — The following items refer only to the display of the buttons on this dialog box. The commands do not affect the display on the Pro/ENGINEER window. o Copy Button Image o Paste Button Image o Reset Button Image o Choose Button Image o Edit Button Image Default — Reset all values on the dialog box to the default values. • If you want to save the configurations you have selected, choose the option Automatically Save To filename. The default value for filename is config.win. The default directory is the current working directory. Permanent and Session-based Configuration Files Pro/ENGINEER supports two different types of configuration files—permanent files and session-based files. Either one can control the session, and you are free to chose which of these you want to work with. Here is how these files differ: • Permanent configuration files — This type of configuration file is typically called a config.pro file, but you can use a different name. For recognizability, we recommend using the .pro extension regardless of what you name the file. Note: If you name a configuration file anything other than config.pro, Pro/ENGINEER cannot reference it during start-up, and you will need to 93 Structural and Thermal Simulation - Help Topic Collection explicitly specify the file through the Options dialog box after your session begins. When it starts, Pro/ENGINEER searches for a config.pro file in your working directory. If it finds one, it references the settings contained in that file when it begins your session. If Pro/ENGINEER does not find a config.pro file in your working directory, it also searches your home directory and the Pro/ENGINEER load point, in that order. Should it fail to find any config.pro files in those locations, Pro/ENGINEER applies default configuration option settings. • Session-based configuration files — This type of configuration file is called current_session.pro and contains configuration options that you intend to use only for the current session. You should consider any settings you place in this file as transient. After you finish the session, Pro/ENGINEER ignores the content of the current_session.pro file and, if you store new configuration option settings in the file, will overwrite any past content. Building and Saving Queries You can build and save queries to search for simulation entities in a model by using the Options button in the Search Tool dialog box. Additionally, you can save the search results on a layer using the Layer option on the Status tab. For example, you can check if a particular group of loads and constraint sets that you want in a static analysis, includes all the specific loads and constraints that you require. • Build Query — When you select the Build Query option, the Search Tool dialog box changes to include the Query Builder section in the dialog box. This section allows you to define rules and operations for your search. The Query Builder uses the Boolean AND and OR operations. You can change the operation by selecting the required operation in the Operator column. After you have defined the rules for your model, you can add, remove, or update the rules by using the Add, Remove, or Update options, respectively. The Add option adds a new rule to the Query Builder. The Remove option removes a selected rule while the Update option replaces a selected rule with the current rule. • Save Query — Saves a query. After you have built a query, you can save the query by selecting Options>Save Query. Specify a layer name in the Save Rules dialog box to save your query as a new layer. Mechanica displays the new layer in the Model Tree. Select Layer in the Status tab to display layers in the Value field. Include or exclude selected simulation entities so that only the required items are displayed in the mesh. Assembly Modeling Entities, Idealizations, and Connections If you have created modeling entities and idealizations in part mode, Mechanica disregards them in assembly mode. You must define in assembly mode any modeling entities and idealizations that you want to use in this mode. 94 Structural and Thermal Simulation The following is a list of the modeling entities, idealizations, and connections that Mechanica ignores in assembly mode: Modeling Entities materials applied to geometry constraints in native mode loads in native mode measures Idealizations and Connections spot welds contacts Note: In FEM mode, Mechanica respects part-level loads and constraints at the assembly level. For example, if you are working in native mode and you model the individual parts of your assembly in part mode, the software ignores the loads you assigned to each part after you access Mechanica from assembly mode. When you access Mechanica from assembly mode, you can then define loads relevant to the assembly as a whole. In any case, modeling entities that you assign while working from assembly mode have no bearing on modeling entities you assign while working from part mode, and the reverse. Guidelines and Tips for Using Datum Points Datum points are particularly useful in Mechanica for a variety of reasons. You need to add datum points to define certain types of constraints, loads, idealizations, connections, measures, and mesh controls. These include: • • • • • • • • • • • • point constraints prescribed temperatures applied to a point convection conditions applied to a point loads applied to a point loads distributed as a total load at point interpolated loads resultant loads connections such as welds, weighted links, rigid links, and rigid connections idealizations such as springs, masses, beams, and trusses local measures associated with a point FEM mesh hard points AutoGEM mesh seed points Be aware that, although you can apply constraints, force loads, and moment loads to points, this application method can cause high stress concentrations that make the correct interpretation of analysis results difficult. You can often produce a more realistic effect by distributing the load or constraint over a small surface region or using a TLAP instead. 95 Structural and Thermal Simulation - Help Topic Collection If you decide to use point loads or constraints, always place your datum points on a boundary curve or surface. Do not locate these points in the interior of the part. You can add datum points to your model singly or, if you are adding the points in Pro/ENGINEER, as a pattern. Although datum points prove useful for certain types of modeling, large numbers of datum points in your part can result in slower Mechanica performance. If your part includes datum points that have no use in Mechanica, consider suppressing these points before accessing Mechanica. Considerations for Multiple Model Sessions When you are working on more than one model at a time in Mechanica, be aware of the following: • If you have a part and an assembly open at the same time, and the part is a component of the assembly, the part and assembly interact as follows: o Saving the assembly automatically saves any changes you made to the part. o Any feature or idealization you add to the part is automatically transferred to the assembly. Running an analysis automatically saves the model. • Pro/ENGINEER Parameters as Measures To use Pro/ENGINEER parameters as measures, you use parameters created through the Tools>Relations command—not the Tools>Parameters command. The reason for this restriction lies in the fact that you want a measure quantity to be able to change during the course of a study so that you can evaluate what happens to the quantity as the study runs. For example, if you define the Young's modulus of your material as a Pro/ENGINEER parameter, you can vary that parameter during a global sensitivity study. If you wanted to see how the change in Young's modulus affects model stresses, you could also create a parameter-based measure for Young's modulus. This measure would enable you to graph other measure quantities in terms of Young's modulus. To learn more about using Pro/ENGINEER parameters as measures, see ParameterBased Measures. Pro/ENGINEER Parameters as Design Parameters To use Pro/ENGINEER parameters as Mechanica design parameters, you must use parameters created through the Tools>Parameters command—not the Tools>Relations command. 96 Structural and Thermal Simulation The reason for this restriction lies with how Mechanica uses design parameters during a design study. When it performs a design study, Mechanica varies the value of the selected design parameters within the range you specified as you defined the design parameter and study. This, in turn, changes the value of the Pro/ENGINEER driving parameter. If you define the Pro/ENGINEER parameter as a variable instead of a constant, you can create situations where both Pro/ENGINEER and Mechanica try to change the parameter. The resulting conflicts would prove undesirable for the study. In creating the Pro/ENGINEER parameters that you plan to use as design parameters, take special care not to use these parameters in relations that would in any way restrict their movement in Mechanica. In other words, do not use these parameters on the left side of any relation equations. To learn more about using Pro/ENGINEER parameters as design parameters, see Design Parameters. Example: Featuring Your Part The order in which you create features and the aspects of your part that you choose to develop as separate features affect how easily you can change the shape of your model. For example, let us say you are building the following shelf bracket: This bracket is made of steel and supports a bookshelf that rests on two rods. The bracket ears and vertical face slide into a die-cast slot in the shelf post. The support holes accept a rod with a predetermined diameter. 97 Structural and Thermal Simulation - Help Topic Collection If you want Mechanica to look at all the features of the shelf bracket when performing shape changes instead of focusing only on the shelf plate and holes, you might develop the part as follows: In this case, you define the shelf plate (feature 1) as the base feature and build the rear plate (feature 2) off the back surface of the base feature. Because you want Mechanica to move the two holes independently, you design each as a separate feature (feature 3 and feature 4). When planning the rounds (feature 5 and feature 6), you can choose between two alternatives. You can either incorporate the rounds into the profile of feature 1 as you build that feature or you can treat the rounds as a separate feature. For the purposes of Mechanica, you should strongly consider the latter method. With this method, you can suppress the rounds if Mechanica encounters a conflict between a round and the movement of any of the defining surfaces. Driven and Driving Parameters A Pro/ENGINEER parameter can be either a driven or a driving parameter. This distinction is an important one for Mechanica, where certain modeling entities require constant values and others require variable values. In planning your Pro/ENGINEER parameters, bear the following Mechanica entity requirements in mind: • For material properties — If you plan to use Pro/ENGINEER parameters to define the characteristics of your material properties, you can use either driven or driving parameters. The difference between the two approaches lies in how directly you want to control the characteristic in question. For a complete discussion of using Pro/ENGINEER parameters as part of a material property definition, see Pro/ENGINEER Parameters. For measures — If you plan to use Pro/ENGINEER parameters as measures, you must select parameters that have a variable value in Pro/ENGINEER. For design parameters — If you plan to use Pro/ENGINEER parameters as Mechanica design parameters, you must select parameters that have a constant value in Pro/ENGINEER. • • 98 Structural and Thermal Simulation If you plan to use Pro/ENGINEER parameters in Mechanica, you may find it handy to create all parameters before you enter Mechanica. If you are creating parameters through the Tools>Parameters command, be aware that Mechanica does not accept parameters that are created using Integer or String as a parameter type. Be aware that Mechanica limits many modeling entity names to 16 characters. You can use alphanumeric characters and underbars only. Names must always start with alphabetic characters. Because Mechanica uses the Pro/ENGINEER parameter names as design parameter and measure names, always observe these naming conventions when creating Pro/ENGINEER parameters. If your Pro/ENGINEER parameter name is too long, the software will truncate it. For your convenience, Mechanica also enables you to define Pro/ENGINEER parameters from the dialog boxes that you use to create design parameters. In this case, the software only accepts a constant, numerical value as the Pro/ENGINEER parameter definition. You can use the Pro/ENGINEER parameters defined by this method as design parameters only—you cannot use them as measures. Note: Mechanica does not enable you to define Pro/ENGINEER parameters from the dialog boxes you use to create measures. Model Accuracy In Pro/ENGINEER, model accuracy is the granularity, or precision, with which the software creates the geometry. For example, model accuracy determines such characteristics as how finely the software tessellates the model's curves. A finely tessellated curve is a smoother curve, whereas a coarsely tessellated curve would give the appearance of a series of straight lines that approximate the shape of the curve. Model accuracy in assemblies can determine whether geometry is treated as merged or separate as well as how successfully you can mesh two components. There are two types of model accuracy—relative accuracy and absolute accuracy. Pro/ENGINEER applies a relative accuracy value when it creates geometry. The default relative value is the same regardless of the part size. Pro/ENGINEER determines the overall accuracy of the geometry by multiplying the relative accuracy value by the part size to determine the absolute accuracy of the geometry. Thus, using the default relative accuracy, the software would create a small part with a greater degree of geometric refinement than a large part. For example, if the size of a small part were 100 and the relative accuracy were 0.012, the absolute accuracy of the geometry would be 1.2. If the size of the larger part were 10,000 and the relative accuracy were also 0.012, the absolute accuracy of the geometry would be 120. The significant difference between the geometric accuracy of these two parts can make it difficult to create a cohesive assembly that includes both parts. In this case, if you were to mate the two components, the differences in tessellation refinement could cause geometric incompatibilities. This is of particular concern for meshing, where the software uses the geometry to determine element edge length, element size, and so forth. For instance, if you 99 Structural and Thermal Simulation - Help Topic Collection mated the two example parts along a nonlinear curve, Mechanica might experience problems in trying to match the small elements that would be a byproduct of the small part's refined tessellation with the larger elements that the larger part's coarser tessellation would produce. Object Action Object action is a feature that enables you to perform an action on an object you select on your model or in the Model Tree. You can right-click highlighted simulation entities in the Model Tree or entity icons on your model to display a shortcut menu listing Mechanica operations that you can perform on the entity. The list of simulation entities on which you can perform object action operations includes, but is not limited to, the following: • • • • • • • • • loads constraints beams shells masses springs shell pairs perimeter welds end welds • • • • • • • • • simulation features gaps (FEM mode) mesh controls (FEM mode) rigid links (FEM mode) weighted links (FEM mode) interfaces meshes material assignments simulation measures As you move your cursor over an icon representing any simulation entity that has been set for prehighlighting, the software highlights the icon in red. If your cursor pauses, a display tag appears showing the entity name. If you select a highlighted icon or select an entity directly from the Model Tree, the icon highlights in red on the model and you can right-click to display the shortcut menu to perform operations on the entity. The object action operations are always in effect, whether or not prehighlighting is set for a simulation entity. Example: Setting up a Solid Model for a 2D Analysis on an Internal Surface You can perform 2D analyses on internal surfaces of a solid model provided you first prepare the model so that Mechanica can isolate the internal geometry to a 2D planar surface. For example, assume that you want to perform a 2D analysis on an internal section of the following solid model. 100 Structural and Thermal Simulation First, you would define a cut through the solid in Pro/ENGINEER to create an external, planar surface. Then, in Mechanica you select the resulting surface for your 2D analysis. The following model is defined as a 2D axisymmetric model type because the 2D geometry is intended to rotate about an axis. Be aware that, in some cases, when you define a cut through a 2D axisymmetric model, you may not be able to select only the surface that you want to include in your analysis. Pro/ENGINEER may instead select multiple surfaces created by the cut. If this occurs, you can define a surface region that includes only the surface or surfaces required to define your 2D model. You can then use the Sketcher to sketch the curve and the Use Edge geometry tool to trace around the geometry. The surfaces created by the cut are effectively separated, and you are able to select the geometry required for the 2D analysis. 101 Structural and Thermal Simulation - Help Topic Collection Connected and Unconnected Parts After you start a run, Mechanica merges the individual parts into a single, multivolume body, where individual parts are either connected or unconnected. Mechanica merges the individual parts as follows: • If parts in an assembly touch, Mechanica views the touching parts as individual volumes with common faces (surfaces) or edges (curves). In this case, the software recognizes an association between the volumes and treats that portion of the assembly as a single Mechanica body with multiple volumes. One exception occurs if the common faces separating two volumes have contact regions defined. Contact regions allow the two volumes to separate during the simulation. If you compress the parts using midsurface compression, you can use end welds or perimeter welds, or let the software create automatic midsurface connections, to eliminate the gaps that occur between mating edges or surfaces of the parts. This ensures that touching entities remain connected. For more information, see Gaps in Assemblies. • If a part does not touch any other part, Mechanica treats the part as an unconnected body. Depending on the tolerance between parts and the degree to which parts touch, Mechanica may or may not connect some of the parts in an assembly. For example, if you create the following assembly, Mechanica connects the parts as shown: The two rectangular parts are close enough to be within tolerance, and they share enough surface for Mechanica to merge them into a single body. However, the sphere and rectangle have only one point of contact. Therefore, Mechanica does not merge the sphere with the rest of the assembly. In this case, the assembly would contain two connected parts and one unconnected part—two bodies in all. Before you run an analysis or design study, Mechanica asks you whether you want error detection. If you do, Mechanica checks for various modeling conditions 102 Structural and Thermal Simulation including the presence of multiple bodies in the model. Should it encounter more than one body, Mechanica displays a message indicating the number of separate, or disjoint, bodies it finds. You can use this information to determine whether parts you thought were connected are truly connected. If you see an unexpected number of bodies, you may want to cancel the analysis or study and correct the assembly. Search Tool Dialog Box Use the Edit>Find command to search for simulation entities, define rules, and specify the search criteria for your search. When you select this command, the Search Tool dialog box appears. The Search Tool dialog box includes the following items: • • Look for — The default selection is Simulation Modeling objects. Look in — This is available only for assemblies. Select the component or assembly from the list in which you want to search for simulation entities. Select Include submodels if you want to search for simulation entities in the submodels of the assembly. In Mechanica, you use two tabs—Attributes and Status—to examine the simulation entities in your model. The Attributes tab enables you to search for classes of simulation entities, and the Status tab lets you search for simulation objects on the layers you have created in your model. The Attributes tab on the Search Tool dialog box allows you to define the rule for Mechanica to use when searching for simulation entities in the model you have selected. You can search by selecting a rule class from Name, Type, or Property. Depending on the rule class you select, the fields in the Criteria area of the dialog box change. • Name — Search for simulation entities by Name. Specify the search criteria by selecting the required Comparison operation from the available list. Select or enter the required value or manually type the name for the simulation entity in the Value list. Based on the model you have selected, the fields in the Value list are populated at runtime. Mechanica searches the model for simulation entities that match the values specified in the Comparison and Value fields. For example, you have selected "is equal to" as the comparison operation and the value specified is BEAM1, Mechanica searches for entities that have the name BEAM1 and displays the search results in the items found: window. Additionally, Mechanica highlights these items in the Model Tree. • • Type — Search for simulation entities by Type. Specify the search criteria by selecting the required Comparison operation, the Category type the entity belongs to, and the Value of the entity from the lists, respectively. Property — Search for simulation entities by Property. Specify the search criteria by selecting the required Property type and Comparison operation. Select or manually enter the value for the entity in the Value field. 103 Structural and Thermal Simulation - Help Topic Collection For the entity value, you can type an alphabetic character followed by a wild card. For example, B*. The wild card is represented by a *. You use the Status tab to examine the contents of a layer that you have defined for your model. When you are working in Mechanica, the Status tab has only one active option button, Layer. The Layer option button lists all the layers available in the model. Layer is a rule that allows you to search for simulation entities in any of the layers in your model by selecting the operation from the Comparison field and the desired layer from the Value field. The Value list contains all layers in your model regardless of the method you used to create the layer—the Layer tool or the Search Tool query builder—or whether you created these layers in Pro/ENGINEER or in Mechanica. Select Add New option to include the new layer in the Query Builder. You can also use the Options button in the Search Tool dialog box to search for simulation entities in the model you have selected by building a query, saving the query, highlighting and displaying selected items, and displaying the filtered selections. Use the Find Now option in the Search Tool dialog box to display a list of simulation objects that the filter finds and, in case of only one matching object, highlights the object. In case of more than one object, you can select an object, and Mechanica highlights that object. You can view the search results in the items found: window. Use the New Search option to start a new search by defining rules, operations, and criteria for the new search operation. Units To Set a Principal System of Units You can use any previously defined system of units as the principal system of units for your model. This procedure assumes you are in Pro/ENGINEER. 1. Select Edit>Set Up>Units. The Units Manager dialog box appears. The Systems Of Units tab displays a list of existing systems of units, and a red arrow marks the current principal system of units. 2. Select the system of units that you want to set as the principal system of units. 3. Click the Set button. A message box appears. 4. Select an option for changing your model's units: • Convert dimensions (for example 1" becomes 25.4mm) • Interpret dimensions (for example 1" becomes 1mm) 5. Click OK. 104 Structural and Thermal Simulation Pro/ENGINEER sets the selected system of units as the principal system of units for your model. You return to the Units Manager dialog box. In the list of systems of units, the arrow points to the principal system of units you just set. To Review an Individual Unit This procedure assumes you are in Pro/ENGINEER. 1. Select Edit>Set Up>Units. The Units Manager dialog box appears. 2. Click the Units tab. 3. If you want to see a list of units of only one type, select an option from the Type drop-down list. 4. Select a unit from the list. You can review the description for the selected unit displayed in the Description box. To Review a System of Units You can display a read-only information window that describes a system of units. This procedure assumes you are in Pro/ENGINEER. 1. Select Edit>Set Up>Units. The Units Manager dialog box appears. 2. Select a system of units from the list on the Systems Of Units tab. 3. Click the Info button. The Information Window appears displaying units information for the selected system of units. You can scroll down or sideways for more information. 4. Click Close to return to the Units Manager dialog box. To Edit a Custom Unit This procedure assumes you are in Pro/ENGINEER. 1. Select Edit>Set Up>Units. The Units Manager dialog box appears. 105 Structural and Thermal Simulation - Help Topic Collection 2. Click the Units tab. 3. Select a custom unit from the list. The Edit button becomes available only when you select a custom unit. 4. Click the Edit button. Or, you can also double-click the name of a custom unit to edit it. The Unit Definition dialog box appears. 5. Make any changes to the dialog box. 6. Click OK to apply the changes you made to the dialog box. To Edit a Custom System of Units This procedure assumes you are in Pro/ENGINEER. 1. Select Edit>Set Up>Units. The Units Manager dialog box appears. 2. Select a custom system of units from the list on the Systems Of Units tab. The Edit button becomes available only when you select a custom system of units. 3. Click the Edit button. Or, you can double-click the name of a system of units to edit it. The System Of Units Definition dialog box appears. 4. Make any changes to the dialog box. 5. If you want more information about the system of units, click the Info button. A read-only Information Window appears, displaying information about the selected system of units. You can scroll down or sideways for more information. 6. Click Close. You return to the System Of Units Definition dialog box. 7. Click OK to apply the changes you made to the dialog box. To Create a Custom Unit Pro/ENGINEER defines a custom unit as follows: new unit = scale x existing unit This procedure assumes you are in Pro/ENGINEER. 106 Structural and Thermal Simulation 1. Select Edit>Set Up>Units. The Units Manager dialog box appears. 2. Click the Units tab. 3. Click the New button. The Unit Definition dialog box appears. 4. Select an option from the Physical Dimension list. Use the Derived option if you want to define a derived custom unit. 5. Enter a name for the custom unit or use the default name. Note: If you selected the Derived option in step 4, go to step 9. 6. Select a reference unit from the drop-down list of existing units. 7. Enter a Scale factor. All custom units are scaled from existing units, including other custom units. 8. If you selected Temperature in step 4, enter an Offset value. 9. If you selected Derived in step 4, enter a Numerical Unit Expression for your derived unit. 10. Click OK. The Units Manager dialog box appears with the name of your new custom unit displayed in the list of units. Units Management You can use the Units tab on the Units Manager dialog box to create, copy, edit, and delete units. This tab displays a list of existing units in Pro/ENGINEER—predefined units and any custom units. You can select a Type option to display units of a particular type only. For more information about the units provided in Pro/ENGINEER, see Predefined Units. The following buttons appear on the Units tab: • • • • New — Creates a custom unit. Copy — Click this button to make a duplicate of an existing unit. On the Copy Unit dialog box, enter a name for the new copy of the unit. This new name will appear in the list on the Units tab. Edit — Active only if you select a custom unit. Click this button to edit a custom unit. Delete — Active only if you select a custom unit. Click this button to delete a custom unit. You cannot delete a custom unit if it is used to define another unit or system of units. 107 Structural and Thermal Simulation - Help Topic Collection Systems of Units Management You can use the Systems Of Units tab on the Units Manager dialog box to work with systems of units and to set a principal system of units for your model. This tab displays a list of the existing systems of units in Pro/ENGINEER—predefined systems of units and any custom systems of units. You can select a principal system of units from the list. A red arrow points to the current principal system of units for your model. For more information about the systems of units provided in Pro/ENGINEER, see Predefined Systems of Units. The following buttons appear on the Systems Of Units tab: • • • Set — Sets the principal system of units. New — Creates a custom system of units. Copy — Click this button to make a duplicate of an existing system of units. On the Copy System of Units dialog box, enter a name for the new copy of the system of units. This new name will appear in the list on the Systems Of Units tab. Edit — Active only if you select a custom system of units. Click this button to edit a custom system of units. Delete — Active only if you select a custom system of units that is not the principal system of units. Click this button to delete a custom system of units. Info — Click to display an Information Window with units information for the selected system of units. • • • Custom Unit Use the New button on the Units tab of the Units Manager dialog box to create a custom unit. A custom unit is a unit that the user defines. You can combine predefined units and custom units to create a custom system of units. When you click the New button, the Unit Definition dialog box appears. Select an option from the Physical Dimension list for the type of unit you want to create: • If you select Length, Mass, Force, Time, or Temperature, the following items appear on the dialog box for the Unit Definition: o Name — Enter a name for the custom unit. o Scale — Enter a scale factor. All custom units are scaled from existing units, including other custom units. o Reference Unit List — Select a reference unit from the list of existing units. o Offset — Appears only if you selected Temperature for the physical dimension. Enter an offset value. If you select the Derived option, the following items appear on the dialog box for the Derived Unit Definition: o Name — Enter a name for the custom derived unit. • 108 Structural and Thermal Simulation o Numerical Unit Expression — Enter a value to define your derived unit. The following expressions are examples of custom derived units: square_feet = ft*ft gravity = 9.81 m/sec^2 atmosphere = 14.7 psi gallon = 231 in^3 speed_of_light = 3e8 m/sec After you click OK on the Unit Definition dialog box, the name of the new custom unit appears in the list of units on the Units Manager dialog box. Custom System of Units Use the New button on the Systems Of Units tab of the Units Manager dialog box to create a custom system of units. You create a custom system of units by combining individual units. You can combine predefined units and custom units to create a custom system of units. For a list of unit values available in Pro/ENGINEER, see Predefined Units. When choosing a system of units, decide which quantities will form the basic physical dimensions and which quantities will be derived from the basic dimensions. The basic dimensions can be either of the following: • • mass, length, time, and temperature force, length, time, and temperature When you define force or mass as your primary unit, the other becomes a derived unit. For example, if you select force as one of your primary units, mass becomes a derived unit for your model. The connection between these two systems is given by Newton's second law of motion: force = mass x acceleration the dimensions of which are: F = ML/T2 When you click the New button, the System Of Units Definition dialog box appears. Enter a name for the new system of units and use these radio buttons to determine the basic physical dimension type: • • Mass Length Time (MLT) — Select this radio button if you want your system of units to be based on mass. Force Length Time (FLT) — Select this radio button if you want your system of units to be based on force. 109 Structural and Thermal Simulation - Help Topic Collection Then, select values for the following units: • • • • Length Mass or Force Time Temperature Guidelines for Specifying Units Before you specify a system of units for your model, read these guidelines: • Default System of Units — If you do not specify a system of units, Pro/ENGINEER uses inch pound-mass second (inch lbm second) as the default system of units. In this system, units of force are defined as lbm * in/sec2. These units of force are not generally used, so you should change the system of units before applying loads in Mechanica. You can also set a default principal system of units in Pro/ENGINEER using the Tools>Options command. • Use Consistent Units for Parts and Assembly — You can specify units in part or assembly mode. If you are working in assembly mode, the units for all the parts must be the same as the assembly. You need to make sure your parts and assembly use consistent units. Also, when you specify values in Mechanica, you need to keep those values consistent with your principal system of units. Entering Numerical Data — When you enter numerical data for quantities with physical dimensions, Pro/ENGINEER interprets the data as having units consistent with the principal system of units. Density — Pro/ENGINEER displays density as mass per unit volume, not weight per unit volume. Modeling Data — Pro/ENGINEER and Mechanica store all data for your model in terms of the principal system of units. When you design a model, you should select a system of units in Pro/ENGINEER before defining modeling data. Exporting to Independent Mode — If you plan to export your model to Mechanica independent mode, make note of your system of units. Mechanica does not display your system of units in independent mode. Material Library — Mechanica displays in the material library only materials with units. • • • • • 110 Structural and Thermal Simulation Unit Conversion Tables This document contains information on using units in Mechanica and on converting values between different systems of units. This document includes the following sections: Topic Introduction Basic Equalities System of Units Basic Units Examples of Values for Gravitational Acceleration and Selected Properties of Steel Correspondence Between Mass and Force Correspondence Between Mass and Pounds-mass Conversion of Basic Units Correspondence Between Degrees Celsius and Degrees Fahrenheit Note: Throughout this document, scientific notation is written as you would type it in Mechanica. For example, 2.07 x 1011 is written as 2.07e11. Introduction Mechanica does not store information concerning the physical dimensions (units) of the numerical data that you enter. Therefore, whenever you enter numerical data into Mechanica, you must ensure that you are using a consistent set of units. For example, if you enter distance in terms of inches and force in terms of poundsforce, then you must enter Young's modulus in terms of pounds-force per square inch. In this system of units, Mechanica reports stress in terms of pounds-force per square inch. If you do not use a consistent set of units when entering data, the values computed by Mechanica will be meaningless. This document provides an overview of the physical dimensions of many of the quantities in Mechanica. The following abbreviations are used throughout this document: L = length M = mass T = time F = force 111 Structural and Thermal Simulation - Help Topic Collection E = energy (heat) P = power D = temperature (such as F, C, K) R = angle radian When choosing a consistent set of units, you must decide which quantities will form the basic physical dimensions and which quantities will be derived from the basic dimensions. Usually, you will choose either mass, length, and time (MLT) or force, length, and time (FLT) as the basic dimensions. The connection between these two systems is given by Newton's second law of motion: force = mass x acceleration the dimensions of which are: F = ML/T2 Some quantities in Thermal are usually expressed in terms of energy and power, the dimensions of which are determined from their definitions: energy (work, heat) = force x distance E = FL power = energy ÷ time P = E/T Basic Equalities Following is a list of many of the quantities in Mechanica and the physical dimensions of each expressed in terms of common physical dimensions and also in terms of MLT and FLT. Quantity length Common L L MLT L FLT time T T T mass M M FT2/L 112 Structural and Thermal Simulation Quantity force Common F MLT ML/T2 F FLT temperature D D D area L2 L2 L2 volume L3 L3 L3 velocity L/T L/T L/T acceleration L/T2 L/T2 L/T2 angle, rotation R R R rotational velocity R/T R/T R/T rotational acceleration R/T2 R/T2 R/T2 density M/L3 M/L3 FT2/L4 moment, torque FL ML2/T2 FL distributed force along a curve F/L M/T2 F/L distributed moment along a curve F ML/T2 F distributed force over a surface, pressure, stress, Young's modulus F/L2 M/LT2 F/L2 113 Structural and Thermal Simulation - Help Topic Collection Quantity distributed moment over a surface Common F/L MLT M/T2 FLT F/L translational stiffness F/L M/T2 F/L rotational stiffness FL/R ML2/T2R FL/R coefficient of thermal expansion /D /D /D moment of inertia of beam cross-sectional area L4 L4 L4 mass moment of inertia ML2 ML2 FLT2 energy, work, heat (E) FL ML2/T2 FL power, heat transfer rate (P) E/T ML2/T3 FL/T temperature gradient D/L D/L D/L heat flux P/L2 M/T3 F/TL thermal conductivity P/LD ML/T3D F/TD convection coefficient P/L2D M/T3D F/LTD 114 Structural and Thermal Simulation Quantity specific heat (Cp) Common E/MD MLT L2/T2D FLT FL/MD System of Units To define a system of units, you assign a unit of measure to each of the physical dimensions. This section provides the units of the above quantities in four different systems of units, two different metric systems, MKS and mmNs, and two different English systems, FPS and IPS. The MKS system of units uses MLT as the basic dimensions. The mmNs, FPS, and IPS systems of units use FLT as the basic dimensions. MKS Following are the basic and some of the derived units of the MKS system: Basic Units M: kilogram (kg) Some Derived Units F: kg-m/sec2 = Newton (N) L: meter (m) E: N-m = Joule (J) T: second (sec) P: J/sec = Watt (W) D: degree Celsius ( C) mmNS Following are the basic and some of the derived units of the mmNS system: Basic Units F: Newton (N) Some Derived Units M: (N-sec2/mm) (kg-m/N-sec2) (1000mm/m) = 1000 kg = tonne(t) 115 Structural and Thermal Simulation - Help Topic Collection Basic Units L: millimeter (mm) Some Derived Units E: (N-mm) (J/N-m) (m/1000mm) = J/1000 = mJ T: second (sec) P: (mJ/sec) (J/1000mJ) (W-sec/J) = W/1000 = mW D: degree Celsius ( C) FPS Following are the basic and some of the derived units of the FPS system: Basic Units F: pound-force (lbf) Some Derived Units M: lbf-sec2/ft = slug L: foot (ft) E: ft-lbf T: second (sec) P: ft-lbf/sec D: degree Fahrenheit ( F) IPS Following are the basic and some of the derived units of the IPS system: Basic Units F: pound-force (lbf) Some Derived Units M: lbf-sec2/in 116 Structural and Thermal Simulation Basic Units L: inch (in) Some Derived Units E: lbf-in T: second (sec) P: lbf-in/sec D: degree Fahrenheit ( F) Basic Units Using the definitions from the previous section, the units of the quantities in these four systems are as follows: Units Length Metric (MKS) m Metric (mmNS) mm English (FPS) ft English (IPS) in Time sec sec sec sec mass kg tonne slug lbfsec2/in force N N lbf lbf temperature C C F F area m2 mm2 ft2 in2 volume m3 mm3 ft3 (cu-ft) in3 (cuin) velocity m/sec mm/sec ft/sec in/sec 117 Structural and Thermal Simulation - Help Topic Collection Units Metric (MKS) Metric (mmNS) English (FPS) English (IPS) acceleration m/sec2 mm/sec2 ft/sec2 in/sec2 angle, rotation rad rad rad rad rotational velocity rad/sec rad/sec rad/sec rad/sec rotational acceleration rad/sec2 rad/sec2 rad/sec2 rad/sec2 density kg/m3 tonne/mm3 slug/ft3 lbfsec2/in4 moment, torque N-m N-mm ft-lbf in-lbf distributed force along a curve N/m N/mm lbf/ft lbf/in distributed moment along a curve N N lbf lbf distributed force over a surface, pressure, stress, Young's modulus N/m2 (Pa) N/mm2 (MPa) lbf/ft2 lbf/in2 (psi) translational stiffness N/m N/mm lbf/ft lbf/in rotational stiffness N-m/rad N-mm/rad lbf-ft/rad lbf-in/rad 118 Structural and Thermal Simulation Units coefficient of thermal expansion Metric (MKS) / C Metric (mmNS) / C English (FPS) / F English (IPS) / F moment of inertia of beam cross-sectional area m4 mm4 ft4 in4 mass moment of inertia kg-m2 tonne-mm2 slug-ft2 lbf-insec2 energy, work, heat (E) J mJ ft-lbf in-lbf power, heat transfer rate (P) W mW ft-lbf/sec in-lbf/sec temperature gradient C/m C/mm F/ft F/in heat flux W/m2 mW/mm2 lbf/ft-sec lbf/in-sec thermal conductivity W/m- C mW/mm- C lbf/sec- F lbf/sec- F convection film coefficient W/m2- C mW/mm2C lbf/ftsec- F lbf/insec- F specific heat (Cp) J/kg- C mJ/tonneC ftlbf/slugF in2/sec2F Note: 1W = 1N-m/sec, 1mJ = 1N-mm, 1mW = 1N-mm/sec, N/m2 = Pascal (Pa) The numerical values of conductivity are the same in the MKS and mmNS systems and in the FPS and IPS systems. 119 Structural and Thermal Simulation - Help Topic Collection In Structure, units of modal frequency results are always cycles per unit time or Hz. The units of time are affected by the force/length/time units you used to define the model. Structure never reports modal frequency in terms of radians per unit time. Examples of Values for Gravitational Acceleration and Selected Properties of Steel The following table shows examples of approximate values for acceleration, density, Young's modulus, thermal coefficient of expansion, and thermal conductivity: Units g (gravitational acceleration) Metric (MKS) 9.81 m/sec2 Metric (mmNS) 9810 mm/sec2 English (FPS) 32.2 ft/sec2 English (IPS) 386 in/sec2 density (steel) 7830.0 kg/m3 7.83e-9 tonne/mm3 15.2 slug/ft3 7.33e-4 lbsec2/in4 Young's modulus (steel) 2.07e11 N/m2 2.07e5 N/mm2 4.32e9 lb/ft2 3.0e7 lb/in2 coefficient of thermal expansion (steel) 12e-6/ C 12e-6/ C 6.5e-6/ F 6.5e-6/ F thermal conductivity (steel) 43.37 W/m- C 43.37 mW/mm- C 5.4 lbf/sec- F (25 Btu/ hr-ft- F) 5.41bf/sec- F (2.083 Btu/ hr-in- F) Correspondence Between Mass and Force The following list describes the correspondence between mass and force at sea level for four common unit systems: 1 kg weighs 9.81 Newtons 1 tonne weighs 9810 Newtons 1 slug weighs 32.2 lbs 120 Structural and Thermal Simulation 1 (lb-sec2/in) weighs 386 lbs Correspondence Between Mass and Poundsmass In some English systems of units, mass is sometimes given in pounds-mass (lbm). The relationship between pounds-mass and mass in the FPS and IPS systems of units is determined by the fact that one pound-mass weighs one pound-force in the gravitational field of the earth at sea level: lbf = lbm x g where g = 32.2 ft/sec2 = 386 in/sec2 Therefore: lbm = 1/386 lbf-sec2/in lbm = 1/32.2 lbf-sec2/ft = 1/32.2 slug Conversion of Basic Units The following tables show conversion factors for various quantities: Length Conversion Factors m mm ft in 1m= 1 1000 3.281 39.37 1 mm = 1.0e-3 1 3.281e-3 3.937e-2 1 ft = 0.3048 304.8 1 12 121 Structural and Thermal Simulation - Help Topic Collection 1 in = 2.54e-2 25.4 8.333e-2 1 Mass Conversion Factors slug (lb-sec2/ ft) kg tonne (N-sec2/mm) lb-sec2/in 1 kg = 1 1.0e-3 6.852e-2 5.71e-3 1 tonne = 1000 1 68.52 5.71 1 slug = 14.59 14.59e-3 1 8.333e-2 1 lb-sec2/in = 175.1 0.1751 12 1 Moments of Inertia kg m2 tonne mm2 slug ft2 lbf-sec2 -in 1 kg m2 = 1 1000 .738 8.85 1 tonne mm2 = 1e-3 1 7.375e-4 8.85e-3 1 slug ft 2 = 1.356 1.356e3 1 12 1 lbf-sec2-in = 0.113 113 1/12 1 Force Conversion Factors 122 Structural and Thermal Simulation N lb 1N= 1 0.2248 1 lb = 4.448 1 Moment Conversion Factors N-m N-mm lb-ft lb-in 1 N-m = 1 1000 0.7376 8.851 1 N-mm = 1.0e-3 1 7.376e-4 8.851e-3 1 lb-ft = 1.356 1356 1 12 1 lb-in = 0.113 113 8.33e-2 1 Density Conversion Factors tonne/ mm3 1e-12 lb-sec2/ in4 9.36e-8 kg/m3 1 kg/m3 = 1 slug/ft3 1.94e-3 1 tonne/mm3 = 1e12 1 1.94e9 9.36e4 1 slug/ft3 = 515 5.15e-10 1 4.82e-5 1 lb-sec2/in4 = 1.07e7 1.07e-5 20700 1 123 Structural and Thermal Simulation - Help Topic Collection Stress Conversion Factors N/m2 N/mm2 lb/ft2 lb/in2 1 N/m2 = 1 1e-6 2.09e-2 1.45e-4 1 N/mm2 = 1e6 1 20900 145 1 lb/ft2 = 47.9 47.9e-5 1 6.94e-3 1 lb/in2 = 6890 6.89e-3 144 1 Translational Stiffness Conversion Factors N/m 1 N/m = 1 N/mm 1.0e-3 lb/ft 6.8525e-2 lb/in 5.7104e-3 1 N/mm = 1000 1 68.525 5.710 1 lb/ft = 14.593 1.4593e-2 1 8.33e-2 1 lb/in = 175.118 1.7512e-5 12 1 Rotational Stiffness Conversion Factors N-m/rad 1 N-m/rad = 1 N-mm/rad 1000 lb-ft/rad 0.7376 lb-in/rad 8.851 1 N-mm/rad = 1.0e-3 1 7.376e-4 8.851e-3 124 Structural and Thermal Simulation 1 lb-ft/rad = 1.356 1356 1 12 1 lb-in/rad = 0.113 113 8.33e-2 1 Thermal Conductivity Conversion Factors W/m- C 1 W/m- C = 1 mW/ mm- C 1 Btu/ hr-ft- F 0.5777 Btu/ hr-in- F 4.817e-2 lbf/ sec- F 0.1249 1 mW/mm- C = 1 1 0.5777 4.817e-2 0.1249 1 Btu/hr-ft- F = 1.731 1.731 1 8.333e-2 0.2162 1 Btu/hr-in- F = 20.76 20.76 12 1 2.594 1 lbf/sec- F = 8.007 8.007 4.626 0.3854 1 Correspondence Between Degrees Celsius and Degrees Fahrenheit The following two formulas describe the correspondence between the Celsius and Fahrenheit degree scales: C = ( F – 32)/1.8 F = 1.8 C + 32 Thus, a temperature difference of 1 C is equal to a difference of 1.8 F. 125 Structural and Thermal Simulation - Help Topic Collection Predefined Systems of Units The Systems Of Units tab displays a list of six predefined systems of units as well as any custom systems of units. You can select any system of units as the principal system of units for your model. The predefined systems are as follows: • • • • • • meter kilogram second (MKS) centimeter gram second (CGS) millimeter Newton second (mmNs) foot pound second (FPS) inch pound second (IPS) inch pound-mass second (inch lbm second) — Pro/ENGINEER default Pro/ENGINEER displays the units for the physical dimensions as follows: System MKS CGS mmNs FPS IPS Pro/ENGINEER Default Type MLT MLT FLT FLT FLT MLT Length m cm mm ft in in lbm Mass Kg G tonne * slug * Force N* erg * N lbf lbf Time sec sec sec sec sec sec Temp K C C F F F * derived unit For a description of each predefined system of units and its basic dimensions, see System of Units in Unit Conversion Tables. The Pro/ENGINEER default, inch poundmass second (inch lbm second), is not a standard system of units, and thus is not described in System of Units. 126 Structural and Thermal Simulation Predefined Units You can combine predefined units with custom units to create a custom system of units. The following predefined units for length, mass, force, time, and temperature are available in Pro/ENGINEER: Length cm ft in micron mil m mm Mass g kg lbm ounce-m mg slug ton-m tonne Force dyne kg-f kip kN lbf N ounce-f ton Time day hr micro-sec min msec sec week Temperature C F K R Set the Principal System of Units Use the Set button on the Systems Of Units tab to set a system of units as the principal system of units for your model. When you select a system of units from the list and click the Set button, a dialog box appears. Select one of the following options in the dialog box: • Convert dimensions (for example 1" becomes 25.4mm) Select this option if you change your system of units after you design your model. Pro/ENGINEER converts your existing Pro/ENGINEER or Mechanica data to the new system of units but does not change the physical size of your model. Pro/ENGINEER converts the following values for your model: o o o o geometric dimensions materials loads prescribed displacements 127 Structural and Thermal Simulation - Help Topic Collection o o o o idealizations (mass, springs, beams) Mechanica design parameters based on Pro/ENGINEER dimensions or beam sections in a global sensitivity study, start and end values of Mechanica design parameters based on Pro/ENGINEER dimensions or beam section dimensions in an optimization sensitivity study, minimum and maximum values of Mechanica design parameters based on Pro/ENGINEER dimensions or beam section dimensions Pro/ENGINEER does not convert the following values: o design parameters based on Pro/ENGINEER parameters o limits for measures in an optimization design study Interpret dimensions ( for example 1" becomes 1mm) Select this option if your model has correct values but an undesired system of units. Pro/ENGINEER does not convert existing Pro/ENGINEER or Mechanica data to the new system of units. Pro/ENGINEER changes the physical size of your model but not your model's dimensional values. When you click OK in the Warning message box, Pro/ENGINEER sets the selected system of units as the principal system of units for your model. • About Units Before designing your model, you should define a principal system of units in Pro/ENGINEER using the Edit>Set Up>Units command in either part or assembly mode. As you build your model, Pro/ENGINEER and Mechanica associate your principal system of units to all aspects of the model-building process. Thus, Pro/ENGINEER and Mechanica store your model's data and perform analyses based on your principal system of units. You must enter all modeling data in the principal system of units, except on the Material Definition dialog box. Before choosing a principal system of units, see Guidelines for Specifying Units. When you select the Units command, the Units Manager dialog box appears. The dialog box includes the following tabs: • • Systems of Units — Use this tab to set a principal system of units, or to create, copy, edit, and delete systems of units. Units — Use this tab to create, copy, edit, and delete individual units. The Description box at the bottom of the Units Manager dialog box displays a short description of the selected unit or system of units. 128 Structural and Thermal Simulation The following icon appears in front of the description for predefined units or systems of units: To Create a Custom System of Units This procedure assumes you are in Pro/ENGINEER. 1. Select Edit>Set Up>Units. The Units Manager dialog box appears. 2. Click the New button. The System Of Units Definition dialog box appears. 3. Enter a name for the new system or use the default name. 4. Select the Mass Length Time (MLT) or Force Length Time (FLT) radio button to indicate the system type. 5. Select a length unit from the Length option list. 6. Select a mass or force unit from the Mass or Force option list. 7. Select a time unit from the Time option list. 8. Select a temperature unit from the Temperature option list. 9. Click OK. The Units Manager dialog box appears with the name of your custom system of units displayed in the list of systems. Modeling Structure and Thermal Problems About Creating Models in Mechanica Before you can analyze a part or assembly in Mechanica, you must create a simulation model that captures the real world conditions that the model will undergo and such characteristics as the material, the presence of masses, and so forth. You create a simulation model by adding modeling entities that define the nature of the model. In addition, you can evaluate and refine meshes as part of the model creation process. The modeling entities you can use to define a simulation model include: • • • model type — Indicate whether you want Mechanica to treat your model as a 3D model or any of several 2D model types. simulation features — Add datum geometry to your model, select and create coordinate systems, and add surface or volume regions. idealizations — Define idealized representations of your model or portions of your model to more accurately represent your model to the solver and improve solver efficiency. 129 Structural and Thermal Simulation - Help Topic Collection • • • • • • • • • • connections — Indicate how areas of your model connect and how loads should transfer. constraints and loads for Structure — Add the loads that affect your model and constrain the model's spatial degrees of freedom, giving the loads something to act against. prescribed temperatures, convection conditions, and heat loads for Thermal — Subject your model to heat loads and define the boundary conditions that describe the model's thermal environment. materials — Define the material your model is made of. material orientations — Describe any material orientations that you want the solver to consider. properties — Define the properties of the idealizations in your model, such as spring properties, shell properties, beam properties, and so forth. measures — Define measures that the solver will calculate. You can define some measures for the entire model, some for specific areas of interest, and some for both. AutoGEM meshes (native mode) — Create a mesh for your native mode model, determine whether the mesh is adequate for your analysis, and refine the mesh if necessary. FEM meshes (FEM mode) — Create and evaluate a mesh for your FEM mode model and refine the mesh if necessary. design parameters (native mode) — Add design parameters to your native mode model so that you can determine the effect of varying geometry and properties in your model as you strive to improve your design. Model Type About Specifying a Product, Mode, and Model Type When you enter Mechanica with a new model, you need to specify the product that you want to use, the mode that you want to operate in, and the model type. You do this using the Model Type dialog box that Mechanica displays after you select the Applications>Mechanica command. This dialog box includes these items: • • • Mode area — Specify the product that you want to use. You can select Structure or Thermal. FEM Mode — In its default state, Mechanica assumes that you want to operate in native mode. Select this check box to work in FEM mode instead. Advanced button — Open the advanced portion of the Model Type dialog box, enabling you to choose between 3D and 2D modeling. 3D modeling is the default for native mode. If you plan to treat your model as a 3D model from the beginning, you do not need to use the Advanced button. However, if you have already specified your model as a 2D model and then want to convert it to a 3D model, you must select the Advanced button to redefine the model as 3D. Note: Because FEM mode supports 3D modeling only, Mechanica deactivates the Advanced button if you select the FEM Mode check box. 130 Structural and Thermal Simulation After you have defined your model using the Model Type dialog box and saved the model, Mechanica stores the information with your model. From this point onward, the software no longer displays the Model Type dialog box whenever you enter Mechanica. If you want to change the product, mode, or model type, you can use the Edit>Mechanica Model Type command. This command opens the Model Type dialog box with its current settings. You can switch products, modes, or model types by altering these settings. If you tend to work in only one product or mode and you typically work with 3D models, you can streamline your entry into Mechanica—and possibly bypass the Model Type dialog box altogether—through the use of config.pro options. There are two situations in which this might prove useful: • If you only use one Mechanica product — If you work primarily in one product—for example, Thermal—you can set that product as the default for the Model Type dialog box through the simulation_product config.pro option. In this case, the software assumes that all your models will be 3D Thermal models and, provided the simulation_fem_mode config.pro option is set to "yes" or "no," will bypass the Model Type dialog box when you enter Mechanica. If you only use FEM mode — If you work exclusively in FEM mode, you can set FEM mode as the default for the Model Type dialog box through the simulation_fem_mode config.pro option. In this case, the software assumes that all your models will be 3D FEM mode models, and the FEM Mode check box will be turned on by default whenever the Model Type dialog box displays for a new model. If you also set the product type using the simulation_product config.pro option, the software will default to your chosen product and will bypass the Model Type dialog box altogether when you enter Mechanica. You will then automatically work in FEM mode for the chosen product. • About Model Types Use the Advanced button on the Model Type dialog box to open the Type portion of the dialog box. The check boxes in this area enable you to select a 3D model type or one of several 2D model types, depending on the kind of analysis that you want to perform in Mechanica. Before selecting a model type, see Guidelines for Working with Model Types. The following model types are available on the Model Type dialog box for Structure and Thermal: Structure 3D 2D Plane Stress (Thin Plate) Thermal 3D 2D Plane Stress (Thin Plate) 131 Structural and Thermal Simulation - Help Topic Collection Structure 2D Plane Strain (Infinitely Thick) 2D Axisymmetric Thermal 2D Plane Strain (Unit Depth) 2D Axisymmetric If you select one of the 2D model types, Mechanica activates the Geometry and Coordinate System areas of the dialog box. You use these areas as follows: • • Geometry area — Select the 2D geometry that you want to use for your 2D model. Coordinate System area — Select a reference Cartesian coordinate system so that Mechanica can correctly interpret your model and verify that the loads and constraints lie in the model plane. Be aware that if your model meets the criteria for a 2D model type, you can save significant calculation time when you run a design study. Additionally, if you perform a function that removes the highlighting of your 2D model, you can use the Repaint option to restore the highlighting. Regardless of which model type you select, Mechanica creates a mesh made up of elements specific to the model type. The type of elements that Mechanica creates for the model type depends on whether you are working in Structure or Thermal. After you select a model type, Mechanica adjusts commands and dialog boxes to reflect the idealizations and degrees of freedom available for the model type you selected. If you change the model type later, Mechanica will delete a variety of modeling entities such as loads, constraints, thermal boundary conditions, idealizations, and meshes. It will, however, keep predefined measures and design parameters. Structure Model Types 3D Model Type Use this option if anything about the model will be outside the XY plane, including idealizations, loads, design parameters, or displacements. You can create the following types of idealizations for a 3D model: • • • shells connections beams • • • masses (Structure only) springs (Structure only) spot welds 132 Structural and Thermal Simulation You can define loads, constraints, design parameters, and other model attributes in six degrees of freedom for a 3D model: • • translation in X, Y, and Z rotation in X, Y, and Z For solids, only three degrees of freedom are available—translation in X, Y, and Z. 2D Plane Stress Structure Model Type Use this option if you are modeling a thin, flat plate—for example, a piece of sheetmetal under tension. In 2D plane stress models: • All included geometry must lie in the XY plane of the Cartesian coordinate system that you select as the reference coordinate system for your model. If you are working with assemblies, all included geometry from the assembly components must lie at the same Z depth. Loads and displacements must be in the XY plane. • For 2D plane stress models, Mechanica meshes your model using 2D plate elements. To successfully run an analysis, you must first assign a simple or advanced shell idealization to any surfaces you plan to include in your plane stress model. In addition to the shell idealizations that you must assign, you can create the mass and spring idealizations for a 2D plane stress model. As mentioned, you must use a Cartesian coordinate system as the model type reference coordinate system. However, you can base other modeling entities on Cartesian, cylindrical, or spherical coordinate systems. You can define loads, constraints, design parameters, and other model attributes in two degrees of freedom for a plane stress model—translation in X and Y (or the cylindrical and spherical equivalents). 2D Plane Strain Structure Model Type Use this option if the strain in one direction is negligible. This is typically the case for structures that are long in one dimension and loaded transversely—for example, long pipes, dams, and retaining walls. 2D plane strain models represent a unit thickness slice of the actual 3D model. In 2D plane strain models: • All included geometry must lie in the XY plane of the Cartesian coordinate system that you select as the reference coordinate system for your model. If you are working with assemblies, all included geometry from the assembly components must lie at the same Z depth. Loads and displacements must be in the XY plane. • 133 Structural and Thermal Simulation - Help Topic Collection If your model meets these criteria, you can model a cross-section of your structure as a 2D plane strain model using shells or solids, or a combination of both. Depending on your choice, Mechanica takes one of the following actions: • Pure solid models — Mechanica meshes your model using 2D solid elements. For solid modeling, you need to assign material properties to the cross-section surface. You should not assign shell idealizations to any of the curves in your model. Pure shell models — Mechanica meshes your model using 2D shell elements. For shell modeling, you should choose only edges when you select the geometry to include in your plane strain model. Do not select surfaces. You also need to create simple or advanced shell idealizations on each curve that you want Mechanica to mesh. You should not assign material properties to the cross-section surface. Mixed models — Mechanica meshes your model using both 2D solid and 2D shell elements. For mixed modeling, you need to create simple or advanced shell idealizations on each curve that you want Mechanica to mesh. You must also assign material properties to the cross-section surface. • • In addition to shell idealizations, you can create the mass and spring idealizations for a 2D plane strain model. As mentioned, you must use a Cartesian coordinate system as the model type reference coordinate system. However, you can base other modeling entities on Cartesian, cylindrical, or spherical coordinate systems. You can define loads, constraints, design parameters, and other model attributes in three degrees of freedom for a plane strain model: • • translation in X and Y (or the cylindrical and spherical equivalents) rotation in Z (or the cylindrical and spherical equivalent) For solid treatments of your model, only two degrees of freedom are available— translation in X and Y. 2D Axisymmetric Structure Model Type Use this option if the geometry of your model and the loads and constraints you plan to place on it are symmetric about an axis—for example, cylindrical and conical structures such as tanks, flanges, or certain clamps. 2D axisymmetric models represent a slice of the actual 3D model that, if revolved around the Y axis of the reference Cartesian coordinate system, would become the original 3D structure. In 2D axisymmetric models: • All included geometry must lie in the XY plane of the Cartesian coordinate system that you select as the reference coordinate system for your model. If you are working with assemblies, all included geometry from the assembly components must lie at the same Z depth. All the geometry must lie in the X > 0 portion of the XY plane. Loads and displacements must be specified in the XY plane. • • 134 Structural and Thermal Simulation If your model meets these criteria, you can model a cross-section of your structure as a 2D axisymmetric model using shells or solids, or a combination of both. When you use a cross-section for 2D axisymmetric modeling, you need to observe several rules that govern Mechanica's ability to treat the cross-section geometry as an entity that can be revolved about an axis. These rules differ depending on whether you are working with surfaces or curves. Depending on how you treat your model, Mechanica takes one of the following actions: • Pure solid models — Mechanica meshes your model using 2D solid elements. For solid modeling, you need to assign material properties to the cross-section surface. You should not assign shell idealizations to any of the curves in your model. Pure shell models — Mechanica meshes your model using 2D shell elements. For shell modeling, you should choose only edges when you select the geometry to include in your 2D axisymmetric model. Do not select surfaces. You also need to create simple or advanced shell idealizations on each curve that you want Mechanica to mesh. You should not assign material properties to the cross-section surface. Mixed models — Mechanica meshes your model using both 2D solid and 2D shell elements. For mixed modeling, you need to create simple or advanced shell idealizations on each curve that you want Mechanica to mesh. You must also assign material properties to the cross-section surface. • • In addition to shell idealizations, you can create the mass and spring idealizations for a plane strain model. As mentioned, you must use a Cartesian coordinate system as the model type reference coordinate system. However, you can base other modeling entities on Cartesian, cylindrical, or spherical coordinate systems. You can define loads, constraints, design parameters, and other model attributes in three degrees of freedom for a 2D axisymmetric model: • • translation in X and Y (or the cylindrical and spherical equivalents) rotation in Z (or the cylindrical and spherical equivalent) For solid treatments of your model, only two degrees of freedom are available— translation in X and Y. Thermal Model Type 3D Model Type Use this option if anything about the model will be outside the XY plane, including idealizations, loads, design parameters, or displacements. 135 Structural and Thermal Simulation - Help Topic Collection You can create the following types of idealizations for a 3D model: • • • shells connections beams • • • masses (Structure only) springs (Structure only) spot welds You can define loads, constraints, design parameters, and other model attributes in six degrees of freedom for a 3D model: • • translation in X, Y, and Z rotation in X, Y, and Z For solids, only three degrees of freedom are available—translation in X, Y, and Z. 2D Plane Stress Thermal Model Type Use this option if you are modeling a thin, flat plate—for example, a piece of glass. In 2D plane stress models, all included geometry must lie in the XY plane of the Cartesian coordinate system that you select as the reference coordinate system for your model. If you are working with assemblies, all included surfaces from the assembly components must lie at the same Z depth. For 2D plane stress models, Mechanica meshes your model using 2D plate elements. To successfully run an analysis, you must first assign a simple or advanced shell idealization to any surfaces that you plan to include in your plane stress model. 2D Plane Strain Thermal Model Type Use this option if the heat flow in one direction is negligible—for example, the temperature varies in two directions but not the third. This is typically the case for structures that are long in one dimension such as a long pipe or a heat sink. 2D plane strain models represent a slice of the actual 3D model. In 2D plane strain models, all included geometry must lie in the XY plane of the Cartesian coordinate system that you select as the reference coordinate system for your model. If you are working with assemblies, all included geometry from the assembly components must lie at the same Z depth. If your model meets these criteria, you can model a cross-section of your structure as a 2D plane strain model using shells or solids, or a combination of both. Depending on your choice, Mechanica takes one of the following actions: • Pure solid models — Mechanica meshes your model using 2D solid elements. For solid modeling, you need to assign material properties to the 136 Structural and Thermal Simulation • cross-section surface. You should not assign shell idealizations to any of the curves in your model. Pure shell models — Mechanica meshes your model using 2D shell elements. For shell modeling, you should choose only edges when you select the geometry to include in your 2D plain strain model. Do not select surfaces. You also need to create simple or advanced shell idealizations on each curve you want Mechanica to mesh. You should not assign material properties to the cross-section surface. Mixed models — Mechanica meshes your model using both 2D solid and 2D shell elements. For mixed modeling, you need to create simple or advanced shell idealizations on each curve you want Mechanica to mesh. You must also assign material properties to the cross-section surface. • 2D Axisymmetric Thermal Model Type Use this option if the geometry of your model and the heat loads, prescribed temperatures, and convection conditions you plan to place on it are symmetric about an axis—for example, cylindrical and conical structures such as storage tanks or conduit. 2D axisymmetric models represent a slice of the actual 3D model that, if revolved around the Y axis of the reference Cartesian coordinate system, would become the original 3D structure. In 2D axisymmetric models: • • All included geometry must lie in the XY plane of the Cartesian coordinate system that with assemblies, all included geometry from the assembly components must lie at the same Z depth. All the geometry must lie in the X > 0 portion of the XY plane. If your model meets these criteria, you can model a cross-section of your structure as a 2D axisymmetric model using shells or solids, or a combination of both. When you use a cross-section for 2D axisymmetric modeling, you need to observe several rules that govern Mechanica's ability to treat the cross-section geometry as an entity that can be revolved about an axis. These rules differ depending on whether you are working with surfaces or curves. Depending on how you treat your model, Mechanica takes one of the following actions: • Pure solid models — Mechanica meshes your model using 2D solid elements. For solid modeling, you need to assign material properties to the cross-section surface. You should not assign shell idealizations to any of the curves in your model. Pure shell models — Mechanica meshes your model using 2D shell elements. For shell modeling, you should choose only edges when you select the geometry to include in your 2D axisymmetric model. Do not select surfaces. You also need to create simple or advanced shell idealizations on each curve that you want Mechanica to mesh. You should not assign material properties to the cross-section surface. • 137 Structural and Thermal Simulation - Help Topic Collection • Mixed models — Mechanica meshes your model using both 2D solid and 2D shell elements. For mixed modeling, you need to create simple or advanced shell idealizations on each curve that you want Mechanica to mesh. You must also assign material properties to the cross-section surface. Guidelines for Working with Model Types Before selecting a model type, you should be aware of the following: • • • If you do not select a 2D model type, your model defaults to 3D. If you select a 2D model type, you must select the geometry on which you want to perform a 2D analysis. For 2D model types, you must also select a Cartesian reference coordinate system. You may need to create a reference coordinate system for your model so that the geometry you select lies in the XY plane. For 2D axisymmetric models, all the geometry must lie in the X > 0 portion of the XY plane. for more information about specifying a reference coordinate system for a 2D model, see About Coordinate Systems. If you change the model type after creating loads, constraints, or other modeling entities, Mechanica deletes all the modeling entities. After you have selected the geometry for a 2D analysis, if you decide to change your model to 3D and then back to a 2D type, Mechanica will highlight the previously selected geometry. You can perform a 2D analysis on all 2D model types. Mechanica supports all analyses and design study types for 2D models, except transient thermal analysis. Large deformation static analysis is supported for 2D plane strain and 2D plane stress models, but not for 2D axisymmetric models. You can perform a contact analysis on two disjoint surfaces. Mechanica cannot perform 2D analysis on midsurface models, sketches, or sections. Mechanica treats assemblies that include 2D components differently depending on whether the top-level assembly component is a 2D or 3D component. Here is a summary of the difference: o If the top-level component is 2D, Mechanica suppresses most simulation data from lower-level assembly components, including loads, constraints, boundary conditions, properties, and idealizations. o If the top-level component is 3D, Mechanica suppresses the simulation data listed above from any 2D lower-level assembly component. If you switch between 2D and 3D model types for the top-level component, Mechanica suppresses or unsuppresses lower-level component simulation data according to the rules just described. • • • • • • • • To Specify a Product, Mode, and Model Type The following procedure assumes that you have already specified a product, mode, and model type, but want to change your original specification. In this case, you need to open the Model Type dialog box and edit your specification as indicated in the procedure. 138 Structural and Thermal Simulation If, instead, you are beginning work on a new model or are working with a model you have not yet saved in Mechanica, the software automatically displays the Model Type dialog box after you select the Applications>Mechanica command. In this case, simply skip step 1 of the following procedure. 1. Select Edit>Mechanica Model Type. The Model Type dialog box appears. 2. Select the product you want to work with—Structure or Thermal—from the Mode option list. 3. If you want to work with your model in FEM mode, ensure that the FEM Mode check box is selected. 4. If you are working in native mode and you want to choose a model type other than the default of 3D or you want to convert a 2D model to a 3D model, click the Advanced button and select the appropriate model type. If you select a 2D model type, see To Define 2D Model Types for additional details and procedures. To Define 2D Model Types This procedure assumes that you are working in native mode, have opened the Model Type dialog box, and selected the product you want to work with. 1. Click the Advanced button. The dialog box expands to display a Type area that lists all model types you can define, as well as additional areas that enable you to select geometry references and a coordinate system. 2. Select the desired 2D model type. 3. Use the arrow selector in the Geometry area to select the geometric entities that will form the 2D model. For all 2D model types, you can select one or more coplanar faces or surfaces. For 2D plane strain and 2D axisymmetric models, you can select one or more of the following entities either alone or in combination: • • coplanar edges or curves faces or surfaces If you want to create pure shell models for any of the model types just listed, be sure to select edges only. 4. Use the arrow selector in the Coordinate System area to select the Cartesian coordinate system that you want to use as the reference coordinate system for your 2D model. 139 Structural and Thermal Simulation - Help Topic Collection All the selected geometry must lie in the XY plane of the reference coordinate system you select. For 2D axisymmetric models only, all geometry must lie in the positive X direction relative to the coordinate system. Example: 2D Axisymmetric Modeling The following example shows a simple tank model and indicates how you would select geometry to rotate about an axis in a 2D axisymmetric model—in this case, the Y axis. The example also shows the differing results of modeling the tank as a 2D solid model and as a 2D shell model. Note that the geometry you select for the 2D solid version of this model is the cross-section surface, whereas the geometry you select for the 2D shell version is a curve to which you have already assigned a simple or advanced shell idealization—in this case, the outside curve. Example: 2D Plane Strain Modeling The following example shows the differing results of modeling a pipe as a 2D solid model and as a 2D shell model. Note that the geometry you select for the 2D solid version of this model is the cross-section surface, whereas the geometry you select for the 2D shell version is a curve to which you have already assigned a simple or advanced shell idealization—in this case, the outside curve. 140 Structural and Thermal Simulation Features About Features Use the Insert>Model Datum command to create simulation features on your model. Simulation features are modeling features, such as datum points and coordinate systems, that you can use to help define modeling entities, such as loads and constraints. Mechanica saves and regenerates these features each time you reenter the Mechanica environment. You can promote certain simulation features (datum points, datum curves, datum planes, and datum axes) to Pro/ENGINEER features, where they remain permanently visible. If you do not promote the features, they are not visible in Pro/ENGINEER. You cannot promote coordinate systems, surface regions, or volume regions to Pro/ENGINEER. You can create the following simulation features. Click on these topics for more information: • • • • • • • Datum points Datum curves Datum planes Coordinate systems Datum axes Surface regions Volume regions You can add simulation features to your model while you are working with modeling entities such as loads, constraints, and beams. To do so, use the datum features creation buttons on the toolbar. 141 Structural and Thermal Simulation - Help Topic Collection Datum Features in Pro/ENGINEER and Mechanica You can create datum features (datum points, datum curves, datum planes, coordinate systems, datum axes) for your model in Pro/ENGINEER, as well as in Mechanica. • • • If you create datum features in Pro/ENGINEER, the features are visible on your model in both Pro/ENGINEER and Mechanica. If you create datum features in Pro/ENGINEER, you can take advantage of certain Pro/ENGINEER part-building techniques not available in Mechanica, such as patterning and mirroring. If you create datum simulation features in Mechanica, they are visible and accessible only in Mechanica unless you promote them to Pro/ENGINEER. Promoting Datum Features to Pro/ENGINEER When you create datum features in Mechanica, the features are not visible or accessible in Pro/ENGINEER unless you promote them. To promote a datum feature, select the feature on your model and select Edit>Promote or right-click the feature in the Model Tree and select Promote from the shortcut menu. The following gives you more information about promoting simulation features to Pro/ENGINEER: • In the Pro/ENGINEER environment, if you delete or suppress a promoted simulation feature that another simulation entity (load, constraint, feature, and so on) references, the software deletes the referencing entity without a warning message. You must promote a parent simulation feature before you promote a child simulation feature. You cannot transfer a promoted simulation feature back to Mechanica. You cannot promote a simulation feature that is a child of a non-promotable feature (surface region, volume region). You cannot promote a Pro/ENGINEER feature to Mechanica. • • • • Creating Features Datum Feature Creation Use the Insert>Model Datum command and its subcommands to create datum features. You can create the following datum features from these subcommands. • • Curve — Takes you directly to the CRV OPTIONS menu, from which you can select the type of datum curve you want to create. Plane — Takes you directly to the DATUM PLANE dialog box, which you can use to create and place the datum plane. 142 Structural and Thermal Simulation • • • Axis — Takes you directly to the DATUM AXIS dialog box, which you can use to create and place the datum axis. Point — Takes you directly to the DATUM POINT dialog box, which you can use to create and place the datum point. Coordinate System — Takes you directly to the OPTIONS menu from which you can select the method you want to use to create the coordinate system. For information on these methods, you can use the help information on the status bar or search for coordinate system information in the Part Modeling functional area of the Pro/ENGINEER Help Center. The methods that you use to create datum points, curves, axes, and planes are the same as those you use in Pro/ENGINEER. For more information, search the Part Modeling functional area of the Pro/ENGINEER Help Center. If you create datum curves, datum planes, datum axes, or datum points in Mechanica, you can promote them so they are permanently visible and accessible in Pro/ENGINEER. Simulation Feature Creation Methods Simulation features are modeling features that you create while you are working in Mechanica—either native mode or FEM mode. These features exist only in your Mechanica session and are not visible in Pro/ENGINEER unless you promote them. Mechanica saves and regenerates simulation features each time you reenter the Mechanica environment. You can use simulation features to help define modeling entities, such as loads and constraints. You can create simulation features on your model in three different ways: • • While in Mechanica, use the Insert>Model Datum command to create datum axes, all three types of coordinate systems, datum points, datum curves, datum planes, surface regions, and volume regions. While in Pro/ENGINEER, use the Insert>Model Datum command to create datum axes, coordinate systems, datum points, datum curves, and datum planes. Note that you cannot create surface or volume regions while in Pro/ENGINEER. Additionally, you can only create Cartesian coordinate systems. Even if you attempt to create cylindrical or spherical coordinate systems in Pro/ENGINEER by using offsets, Mechanica treats the resulting coordinate system as Cartesian. To create true cylindrical or spherical coordinate systems, work from within Mechanica. • Use the icons on the toolbar to create datum axes, datum points, datum curves, or datum planes. Guidelines for Simulation Features • You can create simulation features in assembly components or subassemblies. When you create a feature like this, all instances of the component or subassembly are updated with the created feature. 143 Structural and Thermal Simulation - Help Topic Collection • • You cannot delete simulation features from a part or subassembly of an assembly. You can perform all simulation feature operations on master representations of parts. For non-master representations (or instances), you can only create simulation features. Datum Point Use the Insert>Model Datum>Point command to create datum points. You may need datum points on your model to create a number of Mechanica modeling entities. For example, point loads, springs, and Near Point measures require a datum point. When you select Insert>Model Datum>Point, Mechanica opens the DATUM POINT dialog box, which you use just as you would in Pro/ENGINEER. If you are working with an assembly, Mechanica displays the FEM SELCOMP menu first. Use this menu to indicate whether you want to create the datum point at the assembly level or on one of the assembly components. Note: As an alternative, you can create the datum point by selecting the Insert>Model Datum>Point command and then selecting the Sketched, Offset Coordinate System, or Field command. If you use these methods, you work with dialog boxes other than the DATUM POINT dialog box. Also, you can use the button to add a datum point to your model during the creation of other Mechanica entities. For more information on these methods of creating datum points, search the Part Modeling functional area of the Pro/ENGINEER Help Center. When you create datum points, Mechanica treats the points as simulation features. Simulation features are not visible or accessible when you return to Pro/ENGINEER unless you promote them. To Create Datum Points 1. Select Insert>Model Datum>Point>Point or click . If your model is an assembly and you want to create datum points at the assembly level, select Top Level from the FEM SELCOMP menu. The DATUM POINT dialog box appears. 2. Use this dialog box to specify the datum point placement and properties. 3. Click OK. The DATUM POINT dialog box functions as it would in Pro/ENGINEER. For more information on the dialog box, search the Part Modeling functional area of the Pro/ENGINEER Help Center. 144 Structural and Thermal Simulation As an alternative, you can create the datum point by selecting the Insert>Model Datum>Point command and then selecting the Sketched, Offset Coordinate System, or Field command. If you use these methods, you work with dialog boxes other than the DATUM POINT dialog box. For more information on these methods of creating datum points, search the Part Modeling functional area of the Pro/ENGINEER Help Center. Datum Plane Use the Insert>Model Datum>Plane command to create datum planes. You may need datum planes on your model to create a number of Mechanica modeling entities. For example, you can use datum planes as references for modeling other simulation features, like datum curves, volume regions, and so on. When you select this command, Mechanica opens the DATUM PLANE dialog box, which you use just as you would in Pro/ENGINEER. If you are working with an assembly, Mechanica displays the FEM SELCOMP menu first. Use this menu to indicate whether you want to create the datum plane at the assembly level or on one of the assembly components. Also, you can use the button to add a datum plane to your model during the creation of other Mechanica entities. For more information on creating datum planes, search the Part Modeling functional area of the Pro/ENGINEER Help Center. When you create datum planes, Mechanica treats the planes as simulation features. Simulation features are not visible or accessible when you return to Pro/ENGINEER unless you promote them. To Create Datum Planes 1. Select Insert>Model Datum>Plane or click . If your model is an assembly and you want to create datum planes at the assembly level, select Top Level from the FEM SELCOMP menu. The DATUM PLANE dialog box appears. 2. Use this dialog box to define the datum plane placement and properties. 3. Click OK. The DATUM PLANE dialog box functions as it does in Pro/ENGINEER. For more information on the dialog box, search the Part Modeling functional area of the Pro/ENGINEER Help Center. Datum Axis Use the Insert>Model Datum>Axis to create datum axes. You may need datum axes on your model to create a number of Mechanica modeling entities. For example, 145 Structural and Thermal Simulation - Help Topic Collection you can use a datum axis when designing a cyclic symmetry constraint or defining a coordinate system. When you select this command, Mechanica opens the DATUM AXIS dialog box, which you use just as you would in Pro/ENGINEER. If you are working with an assembly, Mechanica displays the FEM SELCOMP menu first. Use this menu to indicate whether you want to create the datum axis at the assembly level or on one of the assembly components. Also, you can use the button to add a datum axis to your model during the creation of other Mechanica entities. For more information on creating datum axes, search the Part Modeling functional area of the Pro/ENGINEER Help Center. When you create datum axes, Mechanica treats the axes as simulation features. Simulation features are not visible or accessible when you return to Pro/ENGINEER unless you promote them. To Create Datum Axes 1. Select Insert>Model Datum>Axis or click . If your model is an assembly and you want to create datum axes at the assembly level, select Top Level from the FEM SELCOMP menu. The DATUM AXIS dialog box appears. 2. Use this dialog box to define the datum axis placement and properties. 3. Click OK. The DATUM AXIS dialog box functions as it does in Pro/ENGINEER. For more information on the dialog box, search the Part Modeling functional area of the Pro/ENGINEER Help Center. Datum Curve Use the Insert>Model Datum>Curve command to create datum curves. You may need datum curves on your model to create a number of Mechanica modeling entities. For example, some loads and constraints can require a datum curve for designing certain idealization features, like beams. When you select this command, Mechanica opens the CRV OPTIONS menu, which you use just as you would in Pro/ENGINEER. If you are working with an assembly, Mechanica displays the FEM SELCOMP menu first. Use this menu to indicate whether you want to create the datum curve at the assembly level or on one of the assembly components. Note: As an alternative, you can create the datum curve using the Insert>Model Datum>Sketched Curve command. If you use this method, you work with the Sketched Datum Curve dialog box. 146 Structural and Thermal Simulation button to add a datum curve to your model during the Also, you can use the creation of other Mechanica entities. For more information on creating datum curves, search the Part Modeling functional area of the Pro/ENGINEER Help Center. When you create datum curves, Mechanica treats the curves as simulation features. Simulation features are not visible or accessible when you return to Pro/ENGINEER unless you promote them. To Create Datum Curves 1. Select Insert>Model Datum>Curve or click . If your model is an assembly and you want to create datum curves the assembly level, select Top Level from the FEM SELCOMP menu. The CRV OPTIONS menu appears. 2. Select one of the options, and then specify the location of the datum curve. 3. Click Done. The commands on the CRV OPTIONS menu function as they do in Pro/ENGINEER. For more information on each option, search the Part Modeling functional area of the Pro/ENGINEER Help Center. As an alternative, you can create the datum curve using the Insert>Model Datum>Sketched Curve command. If you use this method, you work with the Sketched Datum Curve dialog box. For more information on this dialog box, search the Part Modeling functional area of the Pro/ENGINEER Help Center. Coordinate Systems About Coordinate Systems Your model has two kinds of coordinate systems: • • WCS (world coordinate system) — The default coordinate system in Mechanica, which is a Cartesian coordinate system with its origin at 0, 0, 0. UCS (user coordinate system) — A coordinate system you create. A UCS can be Cartesian, cylindrical, or spherical. You can make a UCS the current coordinate system in place of the WCS. Mechanica associates user coordinate systems with the current body. You can create a coordinate system using one of the following methods: • Use the Insert>Model Datum>Coordinate System command. If you want to create the coordinate system for an entire assembly, be sure to select assembly datum geometry as coordinate system references. Click Datum Coordinate System Tool) on the Pro/ENGINEER toolbar. 147 • Structural and Thermal Simulation - Help Topic Collection In either case, you may want to make the new coordinate system current if you plan to use it as a reference for multiple modeling entities. Also see Axis and Component Equivalents in Different Coordinate Systems and Coordinate System Guidelines for more information. To Create a Coordinate System 1. You can create a coordinate system using one of the following methods: o Select Insert>Model Datum>Coordinate System. o Click Datum Coordinate System Tool) on the Pro/ENGINEER toolbar. After using one of these methods, the COORDINATE SYSTEM dialog box appears. 2. Select Cartesian, Cylindrical, or Spherical from the Type option menu. 3. Select reference geometry for the coordinate system as follows: o If you want to create the coordinate system for an entire assembly, select assembly datum geometry as the coordinate system references. o If you want to create the coordinate system for a part or a single part assembly component, select geometry on the part as the coordinate system references. 4. Complete the tabs on the dialog box to define the coordinate system. For more information on the dialog box and how to define coordinate systems, search the Part Modeling functional area of the Pro/ENGINEER Help Center. 5. Click OK. 6. The coordinate system appears in the model. If you want to make this coordinate system the current coordinate system, see To Set a Current Coordinate System. To Edit a Coordinate System Definition You can edit the definition of a coordinate system once it has been created. 1. Select the coordinate system and then select Edit Definition. 2. Use the COORDINATE SYSTEM dialog box to change the aspects of the coordinate system you are interested in (such as Origin, Orientation, and so on). 3. Click OK. 148 Structural and Thermal Simulation To Modify an Offset Coordinate System You can modify an offset coordinate system. 1. Select the offset coordinate system, click the right mouse button, and select Edit from the pop-up menu. Mechanica displays the offset dimensions in relation to the reference coordinate system. 2. Modify the dimensions you want to change and repaint the work area. The offset coordinate system updates. To Set a Current Coordinate System You can set a coordinate system already defined in your model as the current coordinate system. 1. Select Edit>Current Coordinate System. 2. Select the coordinate system you want to make current. Mechanica highlights the current coordinate system in green. Axis and Component Equivalents in Different Coordinate Systems This table lists the names for equivalent axes in the three different types of coordinate systems you can create (T=theta, P=phi): Cartesian X Y Z Cylindrical T=0, Z=0 T=90, Z=0 Z Spherical P=0, T=90 P=90, T=90 T=0 Mechanica documentation usually uses the Cartesian axes to describe the action of various commands. If you are using cylindrical or spherical coordinate systems, you need to substitute the appropriate equivalents of the X, Y, and Z axes. 149 Structural and Thermal Simulation - Help Topic Collection In addition, Mechanica dialog boxes use Cartesian component nomenclature for certain property types. This table lists the cylindrical and spherical equivalents: Cartesian XX YY ZZ XY XZ YZ ZZ R RZ Z R Cylindrical RR Spherical RR R Coordinates for Spherical UCS When a spherical coordinate system is active, you enter coordinates in the order R, T, P, where: • • • R is the distance from the point to the origin. T( ) is the angle from the T = 0 axis in a plane defined by the point, the origin, and the T = 0 axis (enter in degrees). P( ) is the angle between the P = 0 axis and the line connecting the point as projected onto the T = 90 plane (enter in degrees). The following illustration shows a location (A) in spherical coordinates: Note that the P = 0 axis is the line along which P = 0 and T = 90, and the P = 90 axis is the line along which P = 90 and T = 90. 150 Structural and Thermal Simulation The following illustration shows you how to determine the direction of the unit vectors for theta and phi using the right hand rule (r, , ). Coordinates for Cylindrical UCS When a cylindrical coordinate system is active, you enter coordinates in the order R, T, Z, where: • • • R is the distance from the point to the Z axis. T( ) is the angle in the counterclockwise direction between the T = 0 axis and the line connecting the point as projected onto the Z = 0 plane and the origin (enter in degrees). Z is the distance along the Z axis. The illustration below shows a location (A) in cylindrical coordinates: Note that the T = 0 axis is the line along which T = 0 and Z = 0, and the T = 90 axis is the line along which T = 90 and Z = 0. Cartesian Coordinate System Mechanica creates a Cartesian coordinate system as follows: • • Uses the origin and the X axis location to define the X axis. Defines the Y axis as perpendicular to the X axis and in the plane defined by the origin, the X axis location, and the Y axis location. 151 Structural and Thermal Simulation - Help Topic Collection • If the Y axis location is not on a line perpendicular to the X axis, Mechanica places the positive Y axis in the direction perpendicular to the X axis that is closest to the location you specified. The Y axis still lies in the same plane in which you placed it: The positive Z axis is perpendicular to the XY plane with the positive direction determined by the right-hand rule. Mechanica automatically makes the new coordinate system current. Coordinate Systems and Loads and Constraints You can use coordinate systems to describe the direction of loads and constraints. For example, a load applied to a circular hole, in the X direction relative to a Cartesian coordinate system, should appear as follows: 152 Structural and Thermal Simulation The same load defined in a cylindrical coordinate system with FR=1 now points in the radial direction as shown below: Coordinate Systems and Functions You can use a coordinate system to define functions for prescribed temperatures, heat loads, and spatially varying loads. For a spatially varying load, the load depends on the location of the coordinate system with respect to the geometry. Depending on the coordinate system you choose, the load can have different variations. For example, the following illustrates the magnitude of a load component that varies with the X coordinate of a Cartesian coordinate system: Spherical UCS When you create a spherical user defined coordinate system, you specify the coordinates, which include the origin, the direction of the T = 0 (theta = 0) axis, and the direction of the P = 0 (phi = 0) axis. Mechanica creates the coordinate system as follows: • • Uses the origin and the T = 0 axis location to define the T = 0 axis. Makes the P = 0 axis perpendicular to the T = 0 axis and in the plane defined by the origin, the T = 0 axis location, and the P = 0 axis location. 153 Structural and Thermal Simulation - Help Topic Collection • If you specified a P = 0 axis location that is not on a line perpendicular to the T = 0 axis, Mechanica places the positive P = 0 axis in the direction perpendicular to the T = 0 axis that is closest to the location you specified. The P = 0 axis still lies in the same plane in which you placed it: The positive P = 90 axis is perpendicular to the other axes with the positive direction determined by the right-hand rule. Mechanica displays an icon, showing the origin of the new user coordinate system and the direction of each axis. The orientation of the icon depends on the axes you entered. Here are two views of the icon: Coordinate System Guidelines When you create coordinate systems, be aware of the following: • • When Mechanica displays coordinates, they are coordinates of the current coordinate system, unless otherwise indicated. Mechanica displays an icon for the WCS and for each UCS you create. If you have multiple windows, Mechanica displays the WCS icon in each window, but only displays UCS icons in one window. Mechanica highlights the icon of the current coordinate system in green. • Mechanica saves user coordinate systems with your model. When you reopen a model, Mechanica automatically uses the current coordinate system active when you last saved the model as the current coordinate system for the new 154 Structural and Thermal Simulation • session. However, if you are working in Mechanica, switch to another Pro/ENGINEER application, and return to Mechanica in the same session, the software uses the last coordinate system you designated as current before you switched applications. If you use a UCS as a reference for a load, constraint, or measure, Mechanica warns you if you try to delete that UCS. If you delete the UCS, Mechanica also deletes the load, constraint, or measure. Cylindrical UCS When you define a cylindrical user coordinate system, you enter the coordinates, which include the origin and the locations of the axes. Mechanica creates the coordinate system as follows: • • • Uses the origin and the Z axis location you specify to define the Z axis. Makes the T = 0 axis perpendicular to the Z axis and in the plane defined by the origin, the Z axis location, and the T = 0 axis location. If you specified a T = 0 axis location that is not on a line perpendicular to the Z axis, Mechanica places the positive T = 0 axis in the direction perpendicular to the Z axis that is closest to the location you specified. The T = 0 axis still lies in the same plane in which you placed it: The positive T = 90 axis is perpendicular to the other axes with the positive direction determined by the right-hand rule. Mechanica displays an icon that shows the origin of the new user coordinate system and the direction of each axis. 155 Structural and Thermal Simulation - Help Topic Collection The orientation of the icon depends on the orientation of the axes you entered. Here are two views of the icon: Setting a Current Coordinate System If you want to define multiple modeling entities—for example, a series of loads, constraints, and so forth—relative to a particular coordinate system, you can set that coordinate system as current. You can set an existing coordinate system as current using the Edit>Current Coordinate System command. When you set a coordinate system as current, Mechanica uses it as the reference coordinate system for all entity creation unless you explicitly select a different coordinate system when you define the entity. If you do not set a current coordinate system, Mechanica will treat the WCS as the current coordinate system. Surface Region Use the Insert>Surface Region command to create surface regions. Surface regions enable you to split up a surface so you can perform an operation on a portion of a surface, such as applying loads or constraints. Applying a load to a region is useful for models that require forces in one or more specific areas of a surface. Region definition is a two-step process: • • First, you define the contour that bounds the region. Second, you identify the contour as a region boundary, in effect splitting the bounded area from the parent surface. To do this, you use the SURFACE REGION dialog box. Before you assign a surface region, consider the effect the new region will have on your model. After you fully define a surface region, you can apply constraints, loads, and contact regions to the region, exclusive of the parent surface or other regions on that surface. All rules and procedures that govern loads, constraints, and contact regions applied to full surfaces hold true when you apply these entities to surface regions. 156 Structural and Thermal Simulation Before You Assign a Surface Region Here are some factors to be aware of before when you work with surface regions: • • Be sure the contours you plan to use as region boundaries are in place. If you add surface regions to a fully periodic surface such as a cylinder, cone, or sphere, be sure to select both the segments that make up the surface. This approach eliminates problems like improper region handling if you leave Mechanica and change the periodic surface's geometry. When you add or remove a region for a surface you already defined as part of a shell model pair, Mechanica invalidates the associated pairing scheme, and informs you of the situation. Thus, if you plan to treat your part as a shell model, create all regions before pairing your part surfaces. If you cannot avoid adding or removing a region associated with a paired surface, redefine your pairing scheme to include both the region and parent surface as part of the pair before starting Mechanica analysis. For information on how the software creates shell pairs, see Pairing Schemes. • • If you plan to place loads on surface regions for a shell model, see Model Entities and Idealizations for information on how Mechanica processes this type of load. When you add a region to a surface that already has a constraint, load, or contact region, Mechanica associates the modeling entity with both surfaces. The program adjusts the constraint, load, or contact region icon according to the new placement of the entity. Thus, if you add a region to a surface, be sure to review any associated constraint, load, or contact region placement. Otherwise, the load the surface sees may not be what or where you expect. In the case of constraints, the constraint may no longer be sufficient to prevent rigid body movement. • Defining a Surface Region Contour Before you define a surface region, you must define the contour that defines the region. If you plan to define multiple regions, be sure to create the defining contour for each region as a separate feature; do not group all the contours in one feature. If you do, Mechanica will be unable to region the surface. Also, be aware that Mechanica disregards regions built using techniques such as patterning or mirroring. Use one of the following approaches: • Add a datum curve — Create a datum curve directly on the surface you want to split. If the surface region you want to define requires more than one curve to complete, you can define the region using multiple datum curves. If you use multiple datum curves, you must compile all defining curves into a single composite curve. For more information, search for datum curves and 157 Structural and Thermal Simulation - Help Topic Collection composite datum curves in the Part Modeling area of the Pro/ENGINEER Help Center. • Add a cosmetic feature — Create the desired shape as a cosmetic feature and project the feature onto the part. If you use this approach, the cosmetic feature you create must be parametric. In other words, you must be able to regenerate the section sketch. For more information, search for sketched cosmetic features in the Part Modeling area of the Pro/ENGINEER Help Center. If you use an unregenerated cosmetic feature to create a region, Mechanica displays an error message when you attempt to split the region from its parent surface. You must then return to Pro/ENGINEER part mode to redefine and regenerate the feature. • Add a projected sketch — Create the desired shape as a datum curve and project the curve onto the surface you want to subdivide. While projecting the curve, Pro/ENGINEER treats connected datum curves as composites. To Create Surface Regions 1. Select Insert>Surface Region. If your model is an assembly and you want to create surface regions at the assembly level, select Top Level from the FEM SELCOMP menu. The SPLSRF OPTS menu appears. 2. Select one of the following methods for creating a surface region: o Sketch — Use the sketcher to sketch a boundary for the surface region. o Select — Specify a datum curve boundary for the surface region. 3. Click Done. 4. Use the SURFACE REGION dialog box to define the surface region by selecting or creating the curve that defines the region and then selecting the surface that you want Mechanica to split into regions. Volume Region Use the Insert>Volume Region command to create a volume region so you can break a part into multiple volumes. Volume regions are primarily useful for: • • • facilitating mesh refinement for both AutoGEM and the FEM solvers adding heat loads to internal surfaces of a parent volume. In this case, you apply the heat load to one or more of the surfaces created by the volume region. applying different material properties to different volumes in FEM mode. In this case, you apply one material property to your part and another to the defining surface for the volume region. Mechanica propagates the material property throughout the volume region. 158 Structural and Thermal Simulation When you select the Volume Region command, Mechanica displays the SOLID OPTS menu with these options: • • • • • • Extrude — Extrude a single section. Revolve — Revolve a single section. Sweep — Sweep a section along a trajectory. Blend — Blend two or more sections. Use Quilt — Use quilt surfaces as the boundaries of a volume region. This option is not active if your model contains no quilts. Advanced — Select any of several advanced volume creation methods. These commands open various versions of the VOLUME REGION dialog box—the tool you use to create the geometry that will define the volume region. The procedure for creating volume region geometry using these options is almost identical to the procedure you use to create similar features in Pro/ENGINEER. For more information, search the Part Modeling area of the Pro/ENGINEER Help Center. After you create the volume region, Mechanica treats the volume region geometry as a region boundary, in effect splitting the bounded area from the parent volume. Options for Advanced Volume Region Creation When you select Advanced from the SOLID OPTS menu, Mechanica displays the ADV FEAT OPT menu. Use the commands on this menu to create advanced volume regions. • • • • • • • • Var Sec Swp — Create a volume region based on a variable section sweep of a surface from the trajectories of points on the swept surface. Swept Blend — Create a volume region based on a swept blend from sections at different points on the trajectory of sweep. Helical Swp — Create a volume region based on a sweep along the trajectory defined by profile and pitch. Boundaries — Create a volume region based on the boundaries of a surface. Sect To Srfs — Create a volume region based on a transitional surface between a set of tangent surfaces and a sketched contour. Srfs to Srfs — Create a volume region based on a blend from one tangent surface to another. From File — Create a volume region based on blend sections that are specified from a file. TangentToSrf — Create a volume region that is tangent to a surface. For more information on these techniques, search the Part Modeling functional area in the Pro/ENGINEER Help Center. To Create Volume Regions 1. Select Insert>Volume Region. The SOLID OPTS menu appears. 159 Structural and Thermal Simulation - Help Topic Collection 2. Select one of the following methods for creating volume regions. o Extrude o Revolve o Sweep o Blend o Use Quilt o Advanced 3. Click Done. 4. Use the VOLUME REGION dialog box to define the volume region by selecting or creating the volume that defines the region and then selecting the volume that you want Mechanica to split into regions. Connections About Connections Use the Insert>Connection command to create connections in Mechanica. A connection is the area of contact between two assembly components. When analyzing an assembly for which you have created connections, the software uses the connection type and definition to determine the nature of the contact between the connected areas. You can create the following kinds of connections: Native Mode welds interfaces fasteners rigid connections contacts FEM Mode welds interfaces rigid links weighted links gaps If you work with native mode assemblies that include compressed midsurface shells, you need to consider how you want Mechanica to treat mated and overlapping surfaces. Wherever the surfaces of a component modeled with midsurfaces mate or overlap with the surfaces of another component, Mechanica creates automatic midsurface connections between all contacting surfaces of the two components. Mechanica makes an exception for any surface where you explicitly create a weld, fastener, rigid connection, or free interface. 160 Structural and Thermal Simulation Welds About Welds You can use welds in Mechanica to bridge the gaps that form during shell compression between plates that have been mated because they touch or overlap. You can create the following types of welds: • • • End Welds Perimeter Welds Spot Welds (native mode) When you work with native mode assemblies that include compressed midsurface shells, you need to consider how you want Mechanica to treat mated and overlapping surfaces. Wherever the surfaces of a component modeled with midsurfaces mate or overlap with the surfaces of another component, Mechanica creates automatic midsurface connections between all contacting surfaces of the two components. Mechanica makes an exception for any surface where you create welds, fasteners, or rigid connections. If you do not want Mechanica to apply automatic midsurface connections to given surfaces, you need to use one of the connection types just mentioned or assign free interfaces to those surfaces. About Automatic Midsurface Connections If you work with native mode assemblies that include components with compressed midsurface shells, Mechanica determines which components are modeled with midsurfaces. For these components, the software creates automatic midsurface connections wherever surfaces mate or overlap with those of another component. Mechanica makes an exception for those surfaces that you explicitly designate as free interfaces or those in contact through a weld, fastener, or rigid connection. FEM mode does not support automatic midsurface connections. Automatic midsurface connections allow the mated areas of the assembly to deform as if they were one body. When you mesh your model, these connections appear as dotted magenta lines along the edges of all connected curves and surfaces. In general, you should only use automatic midsurface connections if the area of contact is small relative to the size of the model. Also, for certain models, Mechanica can give results that do not reflect the actual displacement if you use automatic midsurface connections. If this concern you, you can disable automatic midsurface connections by setting the sim_asm_modeling config.pro option to "no." 161 Structural and Thermal Simulation - Help Topic Collection End Welds Use end welds in assembly models to connect plates. Plates can be curved and placed at oblique or right angles, such as T or L configurations. Using the end weld, the shell mesh from one plate is extended to meet the mesh from the base plate, as shown here: When Mechanica creates an end weld, it attempts to keep the neighboring geometry consistent. When a plane surface is moved to a new location during the shell compression process (to the midsurface of its contacting surface), sometimes the surface cannot be extended to the new location. You must make sure, therefore, that a surface to which you are adding an end weld can be extended in this way. If it cannot be extended, consider using the automatic midsurface connection provided by Mechanica. You can use end welds to join the following entities: • • • two thin-wall components connecting at a right or oblique angle two offset thin-wall components mated at a right angle with a gap between the compressed surfaces of the components two offset thin-wall components mated at an oblique angle with no contact between the components To define an end weld, select the Insert>Connection>Weld command to open the Weld Definition dialog box. After you create an end weld, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting an end weld, Mechanica asks you for confirmation first. 162 Structural and Thermal Simulation Defining End Welds and Perimeter Welds Use the Weld Definition dialog box to create end welds and perimeter welds for your model. The dialog box contains the following options: • • Type — Select one of the following weld types: • End Weld • Perimeter Weld References — Use to specify the surfaces to which Mechanica will attach the end weld or perimeter weld. If you selected valid geometric references before entering the dialog box, your selections appear next to the selector arrow when the dialog box opens. Properties — If you selected Perimeter Weld, the following options appear: • Edge(s) — Use the selection arrow to select the edges of the first surface. This selection is optional. If you do not select any edges, Mechanica uses all the edges from the first surface. • Thickness — Enter a value if you want to specify the thickness of the edges. • To Create an End Weld 1. Select Insert>Connection>Weld. The Weld Definition dialog box appears. 2. Enter a name or accept the default name. 3. Select End Weld from the Type option menu. 4. If you did not select geometry before opening the dialog box, click and use the regular selection methods to select the first and second surfaces now. Your selections appear next to the selector arrow in the References area. 5. Click OK. The end weld icon appears where the two surfaces meet. 163 Structural and Thermal Simulation - Help Topic Collection Perimeter Welds Use perimeter welds in assembly models to connect parallel plates, that may be curved, along the perimeter of one of the plates, as shown here: Before mesh generation, a sequence of surfaces is automatically created to connect the selected edges of the top plate to the base plate. Mechanica adds shell elements to the newly created surfaces. A series of welds on one or more of the perimeter edges of the top plate connects it to the base plate. In this case, the components are touching, but the resulting compressed surfaces are parallel to one another and do not touch. For this type of geometry, you should use a perimeter weld to connect the two plates, or allow Mechanica to create automatic midsurface connections. For more information on allowed surfaces, see Guidelines for Surface-Surface Connections and Interfaces (FEM mode). To define a perimeter weld, select the Insert>Connection>Weld command to open the Weld Definition dialog box. After you create a perimeter weld, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a perimeter weld, Mechanica asks you for confirmation first. Defining End Welds and Perimeter Welds Use the Weld Definition dialog box to create end welds and perimeter welds for your model. The dialog box contains the following options: • • Type — Select one of the following weld types: • End Weld • Perimeter Weld References — Use to specify the surfaces to which Mechanica will attach the end weld or perimeter weld. If you selected valid geometric references before entering the dialog box, your selections appear next to the selector arrow when the dialog box opens. Properties — If you selected Perimeter Weld, the following options appear: • Edge(s) — Use the selection arrow to select the edges of the first surface. This selection is optional. If you do not select any edges, Mechanica uses all the edges from the first surface. • Thickness — Enter a value if you want to specify the thickness of the edges. • 164 Structural and Thermal Simulation To Create a Perimeter Weld 1. Select Insert>Connection>Weld. The Weld Definition dialog box appears. 2. Enter a name or accept the default name. 3. Select Perimeter Weld from the Type option menu. 4. If you did not select geometry before opening the dialog box, click in the References area and use the regular selection methods to select the doubler surface on which you will place the weld and the base surface to which the weld will extend. 5. Use the selector arrow under Edges to select one or more edges you want Mechanica to weld. 6. Enter a thickness for the shell elements that will represent the perimeter weld. The perimeter weld icon appears between the two surfaces. Spot Welds Use spot welds to connect two somewhat parallel surfaces at a datum point you specify. Mechanica creates a spot weld entity that connects the two surfaces using a circular beam section to simulate the weld. Spot welds are not available in FEM mode. When you add spot welds to your model, Mechanica connects the two surfaces in a circular spot at a point, and transfers displacements from one part to another. If you are creating an assembly that has rivets, spot welds are one way to model the rivets. When working with spot welds, be aware of the following: • • • The surfaces that you connect must be within 15 of being parallel to each other, and some distance apart. The surfaces cannot be touching. Spot welds transfer load forces. However, stresses close to the welds can be inaccurate. You cannot apply beam releases to the beams created with spot welds. To create a spot weld, select the Insert>Connection>Spot Weld>Create command and follow the prompts. After you create a spot weld, you can edit or delete it using the Insert>Connection>Spot Weld>Edit command or the Insert>Connection>Spot Weld>Delete command, respectively. 165 Structural and Thermal Simulation - Help Topic Collection To Create a Spot Weld 1. Select Insert>Connection>Spot Weld>Create. 2. Select the first and second surfaces that you want to connect. 3. Select a datum point where you want to locate the spot weld. Or, use the button to create a datum point. 4. If you want to create multiple spot welds for the two surfaces, simply create or select more datum points. Mechanica creates a spot weld for each datum point. 5. Enter a weld diameter. 6. Select a material for your weld. If the material you want is not in the material library or already in the model, create a new material for your spot weld and then assign it. 7. Click OK or Close. For each spot weld, Mechanica adds a spot weld icon and a beam icon to your model. Rigid Connections About Rigid Connections A rigid connection connects geometric entities such as surfaces, curves, and points so that they remain rigidly connected during an analysis. Use the Insert>Connection>Rigid Connection>Create command to create rigid connections in your model. Rigid connections are not available in FEM mode. When you connect entities using rigid connections, be aware of the following: • • The entities move together as if part of a single rigid body. The entities do not deform, but the rigid body can move as a whole. Because Mechanica uses linear constraint equations to enforce the rigid rotations, rather than equations with sines and cosines, you should use rigid connections only for small rotation angles of rigidly connected entities. Use rigid connections in this way, even if you intend to use them in a large deformation analysis. The following apply to 3D and 2D models: • • You can create, edit, and delete rigid connections. You can turn rigid connection visibility on and off by selecting or deselecting Rigid Connections on the Simulation Display dialog box (View>Simulation Display>Modeling Entities tab). Additionally, you can use rigid connections to connect two or more parts at selected surfaces, or to help idealize complex models. For example, you can use a rigid connection to connect a point mass representing an engine to the engine mount bolt holes. 166 Structural and Thermal Simulation You can create a rigid connection from one point to a second point. If you are working with a 3D model, at least one of the points must meet one of these two conditions: • • The point must lie on a spring, beam, or shell. The point must act as the reference for a point constraint with at least one free rotation, a point load with a moment, or a point mass with a nonzero moment of inertia. You can create a rigid connection from one or more curves or surfaces on your model to a free point that is not otherwise associated with the model geometry. Use a rigid connection from a surface to a free point with a constraint, for example, to model a pin support. If you create a rigid connection from one edge, to a free point, and then to a second edge, the two edges will move together when you apply a load. When you create a rigid connection to a free point, be aware of the following: • • You can create a displacement measure on a free point with a rigid connection, but the point will not be visible when you view results. You cannot query displacements or rotations at rigidly connected free points. However, Mechanica will include loads or constraints on a rigidly connected point when calculating measures over the entire model, such as maximum displacement. To Create a Rigid Connection You can create a rigid connection that connects points, vertices, edges/curves, or surfaces so they will move together as if part of a single rigid body. 1. Select Insert>Connection>Rigid Connection>Create. 2. Click in the References area and use the regular selection methods to select one or more points, vertices, curves/edges, and/or surfaces that you want to connect. You can select entities of more than one type. 3. If you want to make a rigid connection to a free point, you must select the point and at least one other entity on your model. 4. Click OK to complete the definition. Mechanica places rigid connection icons on the selected entities and assigns a name to each rigid connection. 167 Structural and Thermal Simulation - Help Topic Collection To Edit a Rigid Connection After you have created rigid connections, you can redefine them. 1. Select Insert>Connection>Rigid Connection>Edit. 2. Select the rigid connection that you want to edit. 3. Click the selector arrow in the References area of the Rigid Connection dialog box. Mechanica highlights the entities you defined as associated with this rigid connection. 4. Use the normal selection methods to deselect any of the highlighted entities, and/or select new ones. 5. Click OK to complete the edit. To Delete a Rigid Connection 1. Select Insert>Connection>Rigid Connection>Delete. 2. Select the rigid connections that you want to delete. Mechanica deletes the rigid connections you chose. Fasteners About Fasteners Fasteners simulate bolt or screw connections joining two assembly components. Using fasteners, you can simulate the load path within the assembly as well as the amount of load carried by each bolt or screw. Fasteners are not available in FEM mode or for Thermal. If you plan to add fasteners to your model, the model must meet the certain basic conditions. In most cases, Mechanica informs you if your model does not meet these conditions as you are creating the fastener. However, certain problems do not become apparent until you mesh or analyze the model. Mechanica models fastener stiffness using springs. When it meshes a model that includes fasteners, Mechanica tailors the mesh to improve results about the fastener. The mesh also accounts for the pressure exerted by the bolt head and nut or screw head by refining the mesh in that area. You can use the Insert>Connection>Fastener command to create fasteners in your model. You can create either simple or advanced fasteners: • Simple Fasteners — Mechanica creates the fastener using the material and shaft diameter you specify. The software develops all of the fastener 168 Structural and Thermal Simulation • characteristics based solely on these specifications and various assumptions concerning part separation, rotation, and so forth. Advanced Fasteners — You have the option of creating a fastener based on either material and shaft diameter or on spring properties. Additionally, you can specify various aspects of fastener behavior such as whether the fastener carries shear, restricts rotations for the fastened parts, includes preloads, and so forth. Regardless of the fastener type, you can only create fasteners made of isotropic materials. After you create a fastener, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a fastener, Mechanica asks you for confirmation first. Modeling Prerequisites If you plan to add fasteners to your model, the model must meet the following basic conditions: • • The model must be an assembly. You can add as many fasteners to your assembly as you want, but you can only pass any given fastener through two components. Mechanica does not support zero-length fasteners. When adding fasteners to quilt assemblies, you can inadvertently create zero-length fasteners if you do not correctly account for shell thickness when you place the assembly components. To prevent this problem, be sure to impose offsets equivalent to at least: (part1 shell thickness + part2 shell thickness) / 2 When adding fasteners to midsurface assemblies, take care that the midsurface offsets you use do not result in direct contact between two midsurfaces you intend to fasten. • If you plan to create a fastener based on actual holes in your model, both components must have holes through which the bolt or screw pass. In the case of bolts, both holes must fully pierce the component. For screws, only the component on the screw head side of the fastener connection must be fully pierced. The component on the screw tip side can be fully or partially pierced. Any hole that participates in a fastener connection must be a right cylindrical hole. In other words, the hole must be perpendicular to the component surface and have straight sides. The two holes must be approximately the same size, with the hole axes not further apart than 5% of the hole diameter. The axes of the holes must also be approximately parallel to each other. If the axes are not parallel to within 5 , Mechanica warns you. 169 Structural and Thermal Simulation - Help Topic Collection • • • If you plan to create a fastener based on points in your model, both components must have points to establish the bolt or screw axis. The axes established by the two points must be approximately parallel to each other. If the axes are not parallel to within 5 , Mechanica warns you. There should not be any interfering or intervening geometry in the fastener path—for example, interfering or intervening geometry from one of the fastener components, or a third component that lies between the two fastener components and in the fastener path. You must limit the degrees of freedom in your model by establishing separation between fastened components and limiting their ability to rotate about the bolt or screw axis. When you create simple fasteners, Mechanica automatically enforces certain degrees of freedom for you. However, if you create advanced fasteners, you can either specify that Mechanica takes care of this automatically or use other modeling techniques to deal with any unwanted degrees of freedom. These techniques include adding appropriate constraints or, for separation, defining contact regions. If you choose one of these alternative methods, you must have them in place before running an analysis. Fastener Meshes When it meshes a model that includes fasteners, Mechanica creates the mesh according to the type of fastener you specify and refines the mesh about the fastener to increase the accuracy of your results. To create the mesh, Mechanica determines whether the fastener is a bolt or screw, then creates one or two annular areas about the fastener hole depending on whether the fastener is a bolt or screw, as shown below. Note that the annular area serves only to guide mesh creation, and does not appear as an entity or simulation feature on your model. The illustration shows that if the fastener is a bolt, Mechanica creates two annular areas—one on each of the outside fastener surfaces where the bolt head and nut would contact the fastened components. For screws, Mechanica creates the annular area on the screw head side only. 170 Structural and Thermal Simulation In both cases, the size of the annular area is equivalent to the head diameter. For simple fasteners and most advanced fasteners, Mechanica assumes the head diameter to be 1.7 times the hole diameter. However, if you define a preload, Mechanica instead uses the head diameter you specify as part of the preload definition. The annular areas act as a form of mesh control enforcing smaller elements within its boundaries than might ordinarily be present on the surface. When Mechanica meshes the model, it ensures that no element boundaries cross the border of the annular area. For solid models, this surface mesh refinement extends into the volume, radiating outward from the annular area so that you typically see a concentration of small elements about the annular area with element size increasing as you move away. This mesh refinement enables Mechanica to more accurately calculate the pressure introduced by the fastener head and, for bolts, the fastener nut. If you create simple fasteners or turn on Fix Separation for an advanced fastener, Mechanica creates additional annular areas on the inner surfaces as follows. Here, Mechanica inserts the separation annular areas where the two inner surfaces would contact, enabling Mechanica to correctly model the separation for the solver. These annular areas have a similar effect on the mesh as do the ones for the fastener head and nut—they serve to refine the mesh about the separation area and ensure that element boundaries do not cross the border. For simple fasteners and for advanced fasteners defined using hole references or materials and diameter, the separation annular areas are always 2 the diameter of the fastener shaft. If you define advanced fasteners using both point references and spring stiffness properties, the separation annular areas are always 1.4 (t1 + t2) where t1 is the thickness of the first fastener component and t2 is the thickness of the second. Note: If you are working with a midsurface model or a pure surface, the fastener head and nut annular areas physically coincide with the separation annular areas. In this case, Mechanica uses the fastener head to determine the size of the shared annular area. 171 Structural and Thermal Simulation - Help Topic Collection Creating Fasteners When you select the Insert>Connection>Fastener command, the Fastener Definition dialog box appears. The following items appear on the Fastener Definition dialog box: • • Name — Specify a name for the fastener. If you do not specify a name, Mechanica uses a default name of Fastener1, Fastener2, and so forth. References — Specify the reference type and select geometric entities for your fastener. If you already selected valid geometric references for the fastener before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. Otherwise, use the selector arrow and the regular selection methods to choose the desired geometry. Type — Specify either Simple or Advanced. The remaining fields on the dialog box change depending on your selection. • After you define the fastener and click the OK button, Mechanica automatically creates measures that compute the stresses in the fastener. Mechanica also adds a fastener icon to your model. The size of the icon depends on the head size of the fastener, which is either automatically defined or based on a preload you define. Fastener References You can select from several fastener reference types when you define the location and nature of your fastener. The way you define references indicates the type of fastener you are creating—bolt or screw—as well as the holes or points through which the fastener passes. To define the fastener references, select one of the following reference types on the Fastener Definition dialog box: • Bolt (edges of holes) — Select two edges of holes. The holes can be through either a solid or a surface. The holes you select must meet certain criteria. Mechanica designates the hole associated with the first edge you select as the head side of the bolt. Bolt (points on surfaces) — Select one point on each of two quilts or midsurfaces. If you select this form of reference, your model need not contain actual holes. Instead, Mechanica uses the points you select to form the bolt centerline. The points you select must meet certain criteria. Mechanica designates the surface associated with the first point you select as the head side of the bolt. Note: Before meshing or analyzing the model, you must assign shell idealizations to both quilts. • Screw (edges of holes) — Select two edges of holes. The holes can be through either a solid or a surface. As with bolts, the holes you select must meet certain criteria. Mechanica designates the hole associated with the first edge you select as the head side of the screw. • 172 Structural and Thermal Simulation Simple Fasteners After you select Simple as a fastener type on the Fastener Definition dialog box, the following items appear: • Diameter — Specify the diameter of the fastener shaft. You can use a realnumber value, parameter name, or expression. If you are using holes as references, Mechanica sets the default in the Diameter field to the diameter of the smallest fastener hole. If you change the default diameter, be sure you do not enter a negative number or specify a diameter larger than the diameter of the smaller hole. If you are using points as references, Mechanica does not display a default diameter in the Diameter field. Materials — Specify the material that the fastener is made of. Click the arrow to display a drop-down list of material properties already associated with your model. If you do not see what you want in the drop-down list, use the More button to display more materials, or to create a new material. Note: Because you can not use orthotropic or transversely isotropic materials when creating fasteners, the drop-down list contains only isotropic materials. If you define a simple fastener, Mechanica assumes that: • There is an enforced separation between the fastened components to prevent interpenetration. If there is a valid contact region, Mechanica uses the contact region to enforce separation. If you have not defined a valid contact region, Mechanica enforces the separation automatically when solving for the fastener. The components are free to rotate about each other relative to the fastener axis. To prevent the solver from failing, you must impose constraints to prevent this rotation or define an advanced fastener instead. The fastener carries all the shear force. In other words, there is no friction between the components. • • • To Create a Simple Fastener 1. Select Insert>Connection>Fastener. The Fastener Definition dialog box appears. 2. Enter a name for the fastener in the Name field. 3. Select Simple from the Type option menu. 4. Select a reference type from the drop-down menu in the Reference area. 5. If you did not select geometry before opening the dialog box, click and use the regular selection methods to select the appropriate geometry now. Your selections appear next to the selector arrow in the References area. 6. Enter a real-number value, parameter name, or expression for the Diameter of the fastener. 173 Structural and Thermal Simulation - Help Topic Collection 7. Select a material from the drop-down list. If you do not see the material you want, click More to select a material from the library or to define a new one. 8. Click OK. The fastener icon appears at the fastener location. Advanced Fasteners After you select Advanced as a fastener type on the Fastener Definition dialog box, the following items appear: • Stiffness — Specify the method you are using to define the fastener as follows: • Using Material And Diameter — Define the fastener by specifying the fastener diameter and material. • Using Spring Stiffness Property — Define the fastener by specifying the spring properties of the fastener. Depending on your choice, the items available on the dialog box change. • Fix Separation — Ensure that the fastened components do not interpenetrate. You can select from: • Automatic — Enforces separation based on standard fastener separation or based on a contact region that touches an inside hole edge. If there is a contact region, the contact region ensures that the components do not interpenetrate. If there is no contact region, Mechanica uses standard fastener separation—a faster, less accurate method of preventing interpenetration. One of the effects of using standard fastener separation is that the components cannot separate even if they would naturally do so. • On — Enforces standard fastener separation regardless of the presence of any contact regions about the fastener hole. • Off — Does not enforce any separation. If you select this option, you must enforce separation between the components in some other way— with a contact region, for example. The selection you make has an effect on the mesh and, if you select an option that results in using contact regions, an effect on solver run time. Fix Separation is not active for bolts that use points as fastener references, and the separation for this type of bolt defaults to Automatic. • Include Preload — Define a preload for the fastener. A preload simulates the degree to which the bolt or screw will be tightened and enables you to determine that the fastener properly compresses the components. Include Preload is not active for bolts that use points as fastener references. 174 Structural and Thermal Simulation Defining Advanced Fasteners Using Material and Diameter When you select the Using Material and Diameter option to define fastener stiffness, the Fastener Definition dialog box displays or activates the following items: • Diameter — Specify the diameter of the fastener shaft. You can use a realnumber value, parameter name, or expression. If you are using holes as references, Mechanica sets the default in the Diameter field to the diameter of the smallest fastener hole. If you change the default diameter, be sure you do not enter a negative number or specify a diameter larger than the diameter of the smaller hole. If you are using points as references, Mechanica does not display a default diameter in the Diameter field. Materials — Specify the material of the fastener. Click the arrow to display a drop-down list of material properties already associated with your model. If you do not see what you want in the drop-down list, use the More button to display more materials, or to create a new material. Note: Because you can not use orthotropic or transversely isotropic materials when creating fasteners, the drop-down list contains only isotropic materials. • Fix Rotations — Constrain the components from rotating relative to each other about the fastener axis. Unless you have fully constrained rotations about the fastener by adding displacement constraints, defining extra fasteners, or some other means, be sure this option box is turned on. Carries Shear — Specify that the bolt or screw carries all of the shear force that passes through the fastener connection. If you turn this option box off, the fastener carries none of the shear force. Instead, Mechanica assumes that the shear force passes through the components by friction where the components meet. • • Defining Advanced Fasteners Using Spring Stiffness Properties When you select the Using Spring Stiffness Property option to define fastener stiffness, the Fastener Definition dialog box displays a Spring Property option list you can use to select a spring property that you have already defined. You can also use the More button to create new spring properties, edit existing properties, and so forth. 175 Structural and Thermal Simulation - Help Topic Collection If you choose this method to define a fastener, Mechanica uses spring properties to model the fastener. The spring property you select or create determines the stiffness of the spring, governs the ability of the components to rotate about the fastener, and determines how the fastener carries shear. The X direction of the spring lies along the fastener axis so that Kxx is the axial stretching stiffness of the fastener, Kyy and Kzz are the shearing stiffness, and Txx is the axial rotational stiffness, as illustrated below: Note that, for any spring property you select or define when creating fasteners, you must ensure that Kyy = Kzz. Also, to prevent components from rotating relative to each other about the fastener axis, be sure to specify a relatively high axial rotational stiffness—Txx. Fastener Preloads For advanced fasteners on solid components, you can define the tensile preload that results from the torque you expect the fastener to be tightened to. With this information, Mechanica can calculate such behaviors as component compression and fastener tension, allowing more realistic distribution of stresses between the fastener and the fastened components. If you select the Include Preload check box, the Fastener Definition dialog box displays the following items. For any of these items, you can enter a real-number value, parameter name, or expression. • • Preload Force — Define the tensile force in the fastener that results from tightening the bolt or screw. You must express the force as a positive value. Fastener Head and Nut Diameter — Define the head and nut diameter for the fastener. You can specify a head and nut diameter for screws as well as bolts. If the fastener is a bolt, Mechanica uses the value you enter for both the head and nut. For screws, there is no nut, so the value applies to the 176 Structural and Thermal Simulation • head only. If you do not specify the value, Mechanica uses the default value displayed in this field, which is 1.7 the fastener shaft diameter. Separation Test Diameter — Define an area within which Mechanica will track normal stresses during analysis. Mechanica uses the value you specify to determine a sampling area about the fastener. This area is an annulus with the inside ring as the fastener shaft/hole diameter and the outside ring as the separation test diameter. These annular areas are located on the inner surfaces of the fastener components. As the analysis runs, Mechanica checks the normal stresses at sampling points in the annular area to be sure the stresses remain less than zero. Values of zero or greater mean that there is no compression between the components and the components are separating. Mechanica reports this situation in the analysis summary. If you do not specify a value for Separation Test Diameter, Mechanica uses a default value that it determines as follows: o o If you select Using Material and Diameter from the Stiffness option menu or are using holes as reference, the default is 2 the fastener shaft diameter. If you select Using Spring Stiffness Property from the Stiffness option menu and are using points as references, the default is 1.4 (t1 + t2) where t1 is the thickness of the first fastened component and t2 is the thickness of the second. When you define a preload for a fastener, Mechanica creates a fastener_separation_stress measure that it uses to track compression by evaluating the stresses normal to the inner component surfaces. To Create an Advanced Fastener 1. Select Insert>Connection>Fastener. The Fastener Definition dialog box appears. 2. Enter a name for the fastener in the Name field. 3. Select Advanced from the Type option menu. 4. Select a reference type from the drop-down menu in the Reference area. 5. If you did not select geometry before opening the dialog box, click and use the regular selection methods to select the appropriate geometry now. Your selections appear next to the selector arrow in the References area. 6. Select the method that you want to use to determine stiffness from the Stiffness menu. You can select from these options: • Using Material and Diameter • Using Spring Stiffness Property To Define an Advanced Fastener Using Spring Stiffness Properties 177 Structural and Thermal Simulation - Help Topic Collection This procedure assumes that you have completed the appropriate preliminary steps in To Create an Advanced Fastener. 1. Select a spring property from the drop-down list. If you do not see the spring property you want, click More to define a new spring property. 2. If you are creating the fastener with hole edges as references, select a separation option from the Fix Separation option menu. 3. If you are creating the fastener with hole edges as references and want to include a preload, select the Include Preload check box. 4. Enter a real-number value, parameter name, or expression for the following fields in the Include Preload area: • Preload Force • Fastener Head and Nut Diameter • Separation Test Diameter 5. Click OK. The fastener icon appears at the fastener location. To Define an Advanced Fastener Using Material and Diameter This procedure assumes that you have completed the appropriate preliminary steps in To Create an Advanced Fastener. 1. Enter a real-number value, parameter name, or expression for the Diameter of the fastener shaft. 2. Select a material from the drop-down list. If you do not see the material you want click More to select a material from the library or to define a new one. 3. If you want Mechanica to remove all rotational degrees of freedom from the fastened components, select Fix Rotations. 4. If you want the fastener to carry all the shear force, select Carries Shear. 5. If you are creating the fastener with hole edges as references, select a separation option from the Fix Separation option menu. 6. If you are creating the fastener with hole edges as references and want to include a preload, select the Include Preload check box. 7. Enter a real-number value, parameter name, or expression for the following fields in the Include Preload area: • Preload Force • Fastener Head and Nut Diameter • Separation Test Diameter 8. Click OK. The fastener icon appears at the fastener location. 178 Structural and Thermal Simulation Contact Regions About Contact Regions Use the Insert>Connection>Contact Region>Create command to create contact regions for use in a native mode contact analysis. A contact region indicates the curves or surfaces on which Mechanica considers the effects during a contact analysis. Mechanica ignores contact regions for all other analysis types. You can create contact regions for: • • 2D models 3D models After you create a contact region, you can review it to ensure that you have correctly selected the geometric entities that you want to include in the contact region. You can also delete the contact region using the Insert>Connection>Contact Region>Delete command Contact Regions — 2D Models When you select Insert>Connection>Contact Region for 2D models, Mechanica asks you to specify the two curves that you want to use. Be sure the second curve is near and approximately parallel to the first. After you select the curves, Mechanica checks for the following on a pass or fail basis: • • • The distance between the curves must be less than one half of the average of the lengths of the two curves. At one or more points along the first curve, the normal to the first curve must intersect the second curve. A contact region associated with the two selected curves cannot already exist. Mechanica also checks to see if any points in common between the two selected curves will prevent the curves from moving completely apart during an analysis. If there are any such points, a warning box appears and you should respond appropriately. For each valid pair of curves, Mechanica places a contact region icon at the point where the curves are closest to each other, oriented along the point of closest approach. 179 Structural and Thermal Simulation - Help Topic Collection Contact Regions — 3D Models For 3D models, you can create a contact region between two surfaces. When you select Insert>Connection>Contact Region, Mechanica asks you to specify the two entities that you want to use. If you select two surfaces, Mechanica checks for the following on a pass or fail basis: • The distance between the two surfaces must be less than one half the average of the length of the diagonals of the surfaces. Tip: When creating contacts between surfaces, Structure limits the separation distance and angle between the two surfaces. If you are certain that the two surfaces will eventually contact and you want to work around this restriction, move the surfaces together, define the contact region, and then move them apart again. • • The surfaces must be no more than 36 off parallel at one point at minimum. A contact region associated with the two selected surfaces cannot already exist. Mechanica also checks to see if: • • • the contact region lies between two interpenetrating volumes. any curves in common between the two selected surfaces prevents the surfaces from moving completely apart during an analysis. If there are any such curves, a warning box appears and you should respond appropriately. you are attempting to create a contact region on a surface that is on the boundary of two volumes. Applying a contact region to this surface allows the volumes to separate. If you split a surface that two volumes share, you must place contact regions on all split surfaces to allow the volumes to separate. For each valid pair of surfaces, Mechanica places a contact region icon at the point where the surfaces are closest to each other, oriented along the point of closest approach. To Create Contact Regions You can create a contact region between two surfaces or two parts in an assembly. Mechanica monitors contact regions only for contact analyses. 1. Select Insert>Connection>Contact Region>Create. If you have an assembly loaded, Mechanica displays the CREATE CON menu. Select Face/Surface or Part. 2. Select a surface on a part, or a surface region on a part in an assembly. 180 Structural and Thermal Simulation o For information on requirements for contact regions between surfaces, see Contact Regions — 2D Models. o For information on requirements for contact regions between surface regions, see Contact Regions — 3D Models. 3. Select a second surface or surface region. 4. Repeat steps 2 and 3 for each contact region. Condensation Interfaces Rigid Links (FEM mode) About Rigid Links (FEM mode) A rigid link is a rigid bar element that provides a stiff connection between nodes in your model. The rigid link has two sides, dependent and independent. The independent side governs the movement of a node on the dependent side. Any motion on the dependent side is determined by the motion on the independent side. The dependent side has six degrees of freedom that you can control and fix selectively according to specific modeling needs. Rigid links are useful in performing the following functions: • Connect elements with unmatched DOFs. For example, it is common to connect shell elements, which have rotational degrees of freedom, to solids, which do not. In this case, rigid links can minimize perturbation of the elements' stress and strain at the interface boundary. Tie together components with different meshes. For both hierarchical and flat meshes, rigid links serve as load paths that transmit loads and displacements through assembly components. For more information about the load paths, see Creating Load Paths for FEM Meshing. • You can use the Insert>Connection>Rigid Link command to create rigid links in your model. After you create a rigid link, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a rigid link, Mechanica asks you for confirmation first. While creating, editing, or deleting rigid links, keep in mind the following: • • • • Use the rules that govern the way you work with the rigid links. Control visibility of the rigid link icons by using the View>Simulation Display command. Mechanica places two icons—one for the link, another for the degrees of freedom—on the model. Place the rigid links on layers. Use object action to make any changes to the rigid links. Mechanica outputs rigid links as RBAR cards to be used with the NASTRAN solver. One rigid link may create multiple RBAR cards in the output NASTRAN deck. Because Mechanica supports only NASTRAN for the rigid link output, if you try to choose 181 Structural and Thermal Simulation - Help Topic Collection another solver, Mechanica ignores the rigid link. Mechanica does not output the rigid link whose dependent side has constraints. Creating Rigid Links (FEM mode) When you select the Insert>Connection>Rigid Link command, the Rigid Link Definition dialog box appears. To fully define a rigid link, you must name it and specify the following on the Rigid Link Definition dialog box: • References — Use to specify the reference type and select geometry for your rigid link. The first geometric entity you select applies to the independent side of the link, and the second—to the dependent. If you already selected valid geometric references for your rigid link before entering the dialog box, your selections appear next to the selector arrow when the dialog box opens. Otherwise, use the selector arrow and the regular selection methods to choose the desired geometry. You can select one of the following reference types: Point–Point — Creates a rigid link between two points or two vertices. o Point–Surface — Creates a rigid link between a point and a surface, or a vertex and a surface. o Point–Edge — Creates a rigid link between a point and an edge, or a vertex and an edge. o Surface–Surface — Creates a rigid link between two surfaces. For more information on allowed surfaces, see Guidelines for SurfaceSurface Connections and Interfaces (FEM mode). Override Coordinate System — This option is available for both dependent and independent reference entities of the rigid link. Check this box if you want to select a new coordinate system for the reference entities. The selected coordinate system overrides the default WCS or the displacement coordinate system that you have assigned using the Mesh Control dialog box. Note: You cannot override the displacement coordinate system that has been earlier specified by another rigid link, load, or constraint associated with the selected reference entity. If you output to NASTRAN, conflicts between coordinate systems may occur. • Degrees of Freedom — Use to specify degrees of freedom for the dependent reference entity. Degrees of freedom define the ability of a node on the dependent side of the link to move in any direction in space. The node may have six degrees of freedom—three translational and three rotational. o • Note that if you change references or delete a link that has already been meshed, Mechanica erases the mesh. 182 Structural and Thermal Simulation After you create your rigid link, Mechanica displays two icons on the model—one for the rigid link and another for the degrees of freedom. To Create a Rigid Link (FEM mode) 1. Select Insert>Connection>Rigid Link. The Rigid Link Definition dialog box appears. 2. Enter a name for the rigid link, or use the default name. 3. If you did not select references for the rigid link before entering the dialog box, choose the reference type and click in the References area to select geometry on your model. The first reference you select corresponds to the independent side. The second one—to the dependent side. The points you use for any reference type requiring points can be any of the following: o a single point or vertex o a point feature (includes one or more single points) o a pattern of point features For the independent side, select the Override Coordinate System check box if you want to select a new displacement coordinate system. For the dependent side, select the Override Coordinate System check box if you want to select a new displacement coordinate system. For the dependent side, accept the default degrees of freedom or select a different combination of DOF. Click OK to save the new rigid connection. Mechanica places two icons on the model—one for the rigid link and another for the degrees of freedom. 4. 5. 6. 7. Weighted Links (FEM mode) About Weighted Links (FEM mode) A weighted link is an interpolation constraint element that takes masses or loads acting at a single source node and distributes them to a collection of target nodes. Weighted links have the following characteristics: • • Weighted links distribute masses or loads in a balanced manner. Weighted links help you to control this distribution through degrees of freedom that you assign to a target node group as a whole. Assigning degrees of freedom enables the target nodes to move in specific directions. Mechanica uses degrees of freedom to construct linear constraint equations while calculating load or mass distribution. Weighted links can have only one source node that follows the average motion of the target node group. Thus, the source node is called dependent and the target nodes—independent. Nodes at the independent side determine the motion of a single node at the dependent side. In other words, any • 183 Structural and Thermal Simulation - Help Topic Collection motion of a node on the dependent side reflects the average motion of the nodes on the independent side. These characteristics make weighted links useful when you need to attach mass idealizations to your model without stiffening the structure. You can use the Insert>Connection>Weighted Link command to create weighted links in your model. After you create a weighted link, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a weighted link, Mechanica asks you for confirmation first. While creating, editing, or deleting weighted links, keep in mind the following: • • • • Use the precedence rules. Control visibility of the weighted link icons by using the View>Simulation Display command. Mechanica places two icons—one for the link, another for the degrees of freedom—on the model. Place the weighted links on layers. Use object action to make any changes to the weighted links. Mechanica outputs weighted links as RBE3 cards to be used with the NASTRAN solver only. If you try to choose another solver, Mechanica ignores the weighted links. Mechanica does not output the weighted link whose dependent side has constraints. Creating Weighted Links (FEM mode) When you select the Insert>Connection>Weighted Link command, the Weighted Link Definition dialog box appears. To fully define a rigid link, you must name it and specify the following on the Weighted Link Definition dialog box: • Independent Side — Specify the location of target nodes that receive a mass or load distributed from a source node. If you already selected valid geometric references for the independent side before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. Otherwise, click the selector arrow to choose the geometric reference entity for the independent side. Override Coordinate System — Select a new coordinate system for the reference entities of the independent side. The selected coordinate system overrides the default WCS or the displacement coordinate system that you have assigned using the Mesh Control dialog box. Note: If you output to NASTRAN, conflicts between coordinate systems may occur. • • Degrees of Freedom — Specify degrees of freedom for the independent reference entity. Dependent Side — Specify a source point where you apply a load or a mass to be distributed. You can select a single point or vertex. • 184 Structural and Thermal Simulation • Override Coordinate System — Select a new coordinate system for the reference entities of the dependent side. The same rules that govern your selection of the coordinate system for the independent side apply here. Note that if you change the references or delete a weighted link that has already been meshed, Mechanica automatically erases the mesh. After you create your weighted link, Mechanica displays two icons on the model—one for the weighted link and another for the degrees of freedom. To Create a Weighted Link (FEM mode) 1. Select Insert>Connection>Weighted Link. The Weighted Link Definition dialog box appears. 2. Enter a name for the weighted link or use the default name. 3. If you did not select geometry for the independent side of the link before entering the dialog box, choose the reference type and click to select any of the following geometric references: o Point(s) o Edge(s)/Curve(s) o Surface(s) For the independent side, select the Override Coordinate System check box if you want to select a new displacement coordinate system. For the independent side, accept the default degrees of freedom or select a different combination of DOF. For the dependent side of the link, select or create a point as a reference entity. For the dependent side, select the Override Coordinate System check box if you want to select a new displacement coordinate system. Click OK to save the new weighted connection. Mechanica places two icons on the model—one for the weighted link and another for the degrees of freedom. 4. 5. 6. 7. 8. Interfaces Interfaces in Native Mode The default interface type for mated surfaces in native mode is bonded, meaning that the surfaces will share nodes and Mechanica will, in effect, treat them as merged surfaces. If this is undesirable, use the Insert>Connection>Interface command in native mode to specify which surfaces you want Mechanica to treat as free interfaces during meshing and analysis. When you select this command, the Interface Definition dialog box appears, enabling you to assign free interfaces for any mated surfaces in your assembly that you do not want Mechanica to treat as bonded. 185 Structural and Thermal Simulation - Help Topic Collection The Interface command is available only if you have a 3D assembly open. You can define free interfaces for the following types of entity pairs in Mechanica: • • • • • • Solid—solid Solid—shell Solid—midsurface Shell—shell Shell—midsurface Midsurface—midsurface To define a free interface on a midsurface, you select the surface that will be compressed to a midsurface. If your assembly includes components modeled with midsurfaces, Mechanica compresses these components during meshing, potentially creating gaps in the assembly. To prevent these assembly gaps, Mechanica creates automatic midsurface connections where the original surfaces of midsurface components mate or overlap with surfaces from other assembly components. If you want to avoid these automatic midsurface connections, you can define a free interface between the overlapping surfaces. In this case, your model will have inconsistent meshes for the contacting components where you have placed the free interfaces, and there will be assembly gaps at the free interfaces. When you define an interface as Free, Mechanica outlines the interface and adds an interface icon to your assembly. When you transfer the assembly to independent mode Mechanica, the free interfaces will be outlined with a bold border. Keep the following in mind if you work with your assembly in both native mode and FEM mode: • The default interface type in native mode is Bonded. You cannot change the definition of the default interface type in native mode, but you can in FEM mode. If you define the default type in FEM mode as Free, and then enter native mode, Mechanica uses a default interface type of Bonded. If you specify a Bonded interface for surfaces in your assembly in FEM mode, and then enter native mode Mechanica, the bonded interface definition will be suppressed. • After you create an interface, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting an interface, Mechanica asks you for confirmation first. 186 Structural and Thermal Simulation Interfaces in FEM Mode In addition to end welds and perimeter welds, Mechanica uses interfaces to connect surfaces. When you create an interface, you specify how your surfaces will be treated during meshing and analysis. When you select the Insert>Connection>Interface command in FEM mode, the Interface Definition dialog box appears with the following items: • • Bonded — Mechanica considers two surfaces as bonded. This means that matching nodes on surfaces merge. Instead of two geometrically consistent nodes, a shared one exists. Free — Mechanica specifies two surfaces as contacting, but does not define the type of contact. Meshes on the surfaces are identical, and matching nodes are geometrically consistent unless you specify otherwise by deselecting the Generate Compatible Mesh check box. References — Use the selector arrow in this area and the regular selection methods to select two surfaces on your model that you want to define as Bonded or Free. You can select any two surfaces that you defined as mated or mated with offset in Pro/ENGINEER. For more information on allowed surfaces, see Guidelines for Surface-Surface Connections and Interfaces (FEM mode). If you already selected valid surfaces before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. Generate Compatible Mesh — This option is available only for Free interfaces, and is on by default. If you clear this check box in the Properties area, Mechanica treats the surfaces on your interface as having no contact and does not create geometrically-consistent node locations when it generates the mesh for the surfaces. This is the same behavior as seen in previous releases for the None interface type. Note: If you defined an interface type None for your assembly in a previous release, Mechanica converts the interface type to Free with the Generate Compatible Mesh option turned off. If you defined an interface type Free for your assembly in a previous release, Mechanica converts the interface type to Free with the Generate Compatible Mesh option selected. You can set either Bonded or Free as the default contact type for FEM mode. In this case, Mechanica applies the default you set to all mated surfaces in your model except those for which you explicitly define a different type of contact. To set the default contact type, use the Properties>Default Interface Type command. Note: In native mode, the Free connection type is not supported as a default setting. If you define the default connection type for your assembly as Free in FEM mode, and open the assembly in native mode, any analyses you run will use a default connection type of Bonded. After you create an interface, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting an interface, Mechanica asks you for confirmation first. • • 187 Structural and Thermal Simulation - Help Topic Collection To Create an Interface 1. Select the Insert>Connection>Interface command. The Interface Definition dialog box appears. 2. Enter a name or accept the default name. 3. In FEM mode, select Bonded or Free from the option menu under Type. In native mode, this option menu is inactive, and Free is the only available interface Type. 4. If you did not select geometry before entering the dialog box, click and use the regular selection methods to select two surfaces on your assembly now. 5. In FEM mode, if you selected Free, the Generate Compatible Mesh check box is available, and is selected by default. Clear this check box if you do not want Mechanica to create geometrically-consistent node locations when it generates the mesh for the surfaces of your interface. 6. Click OK. Mechanica adds an interface icon to your model. Gaps (FEM mode) About Gaps (FEM mode) A gap is a nonlinear element you use to model contact between points, edges, or surfaces in your model by connecting two nodes in separated geometries. You can use a vertex as a point by selecting the vertex location. Use gaps to represent a nonlinear flexible and friction link that can resist either compression or tension. Depending on the FEA solver, a gap can have friction or flexible characteristics. To learn how the FEA solvers treat gaps, see ANSYS and MSC/NASTRAN. To create a gap, select Insert>Connection>Gap to display the Gap Definition dialog box. After you create a gap, you can edit or delete it as follows: • • editing a gap — Select the gap icon for the gap you want to edit. Then, select Edit>Definition to re-open the Gap Definition dialog box and edit the current settings. deleting a gap — Right-click on the gap icon for the gap you want to delete. Then, select the Delete command from the object action menu. Mechanica deletes the gap without confirmation. You can control the visibility of gaps on your model by using the View>Simulation Display command, or by placing them on layers. 188 Structural and Thermal Simulation Creating Gaps (FEM mode) Use these items on the Gap Definition dialog box to specify the properties for your gap. • • Name — Enter a descriptive name or accept the default name. References — Select geometric entities on your model. You can create a gap between a point and an edge, a surface, or a second point. You can also create a gap between two surfaces. If you already selected valid geometric references for your gap before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. Otherwise, use the selector arrow and the regular selection methods to choose the desired geometry. For a point–point, point–edge, or point–surface gap, you can select any of the following entities. See Precedence Rules for more information. o o o single point or vertex point feature (includes one or more single points) pattern of point features For a surface-surface gap, you can select any of the following entities: o o o surfaces on two different parts in an assembly a surface and a quilt on the same part surfaces with the same type of curvature. For example, you cannot form a surface-surface gap between a planar surface and a spherical surface, or a cylindrical surface and a cone surface. • • • • Clearance — Define the distance between two nodes at which Mechanica activates axial and transverse stiffnesses due to displacement during an analysis. If you specify Clearance as zero, the gap acts as a spring. Axial Stiffness — Define the axial stiffness value. Where applicable, this parameter defines the stiffness or a spring factor. Transverse Stiffness — Define the transverse stiffness value. This parameter defines elastic stiffness, characterizing resistance of the material until the slippage occurs. This parameter is optional. Y direction — Define the Y direction by selecting a datum point, edge, curve, axis, surface, or vertex to identify the XY plane of the element. You can also specify a vector in the WCS. The X direction is given by the gap length, which is the shortest distance between the two selected references. A zero-length gap has no length between the two references. For example, you can define a gap between a point on a surface and the surface itself. For a zero-length gap, the X direction is normal to the surface. • Distribution — Select the method that Mechanica uses to calculate the axial and transverse stiffnesses for your gap. This option is available only for 189 Structural and Thermal Simulation - Help Topic Collection surface–surface gaps. The stiffnesses are distributed uniformly across the surfaces. o Total — The entered value represents the sum of stiffnesses for all gap elements. o Per Unit Area — The entered value is multiplied by the surface area to give the stiffness values. The area of the first selected surface is used for the stiffness calculations. See Surface-Surface Gaps for more information. To Create a Gap (FEM mode) 1. Select Insert>Connection>Gap. The Gap Definition dialog box appears. 2. Enter a name or accept the default name. 3. If you did not select geometry before opening the dialog box, select one of these references for the gap from the drop-down list, and use the normal selection methods to select the appropriate geometric entities on your model: o Point–Point — Select two points or two vertices. o Point–Edge — Select a point and an edge, or a vertex and an edge. o Point–Surface — Select a point and a surface, or a vertex and a surface. o Surface–Surface — Select two surfaces. 4. Select and define Y-direction and these stiffness properties: o Clearance o Axial Stiffness o Transverse Stiffness 5. If you select Surface–Surface under Reference, select one of these methods for calculation of the stiffness values from the Distribution dropdown list: o Total o Per Unit Area 6. Click OK. Mechanica places a gap icon at the specified location on your model. Precedence Rules Precedence rules for your idealizations and connections determine which modeling entity takes precedence when you apply two modeling entities of the same type on or between the same reference entities. There are two types of precedence rules, modeling precedence rules and geometric precedence rules. Modeling Precedence Rules These rules apply when you work with assemblies, and are determined by the assembly hierarchy: • When you apply a modeling entity from a top-level assembly, this modeling entity takes precedence over a modeling entity applied from a subassembly or a part. 190 Structural and Thermal Simulation • When you apply a modeling entity from a subassembly, this modeling entity takes precedence over a modeling entity applied from a part. Geometric Precedence Rules Keep these rules in mind when working with the modeling entities that require points, curves, or surfaces as their reference entities. With some of these modeling entities, you can use multiple geometric entities as reference entities. For example, you can select a feature or a pattern of points and create a beam, spring, or rigid link that runs along a sequence of points. You can also apply a beam on multiple curves, or place a shell on a collection of surfaces. If you later create a new modeling entity of the same type, placing it on or between the same reference entities, it overrides the existing one when the following conditions are met: • • You select a higher precedence geometric entity as a reference entity for your new modeling entity. The higher precedence geometric entity belongs to a lower precedence geometric entity already referenced by your existing modeling entity. For example, if you select a single point as a reference entity for your new beam, the new beam overrides an existing one that references a feature of points that include this single point. The following table illustrates how the precedence rules work for modeling entities that can reference points, curves, or surfaces. Modeling Entity or Mesh Control Reference Entity Geometric Precedence Rule A single point takes precedence over a feature of points or a pattern of points. A feature of points takes precedence over a pattern of points. Points take precedence over curves, edges, and surfaces. • • • • • • beam spring mass gap rigid link weighted link points • • beam mass (in FEM mode) An individual curve takes precedence over a composite curve. curves or edges Curves and edges take precedence over surfaces. 191 Structural and Thermal Simulation - Help Topic Collection Modeling Entity or Mesh Control • shell • beam (surfacesurface, in FEM mode) • mass (in FEM mode) Reference Entity Geometric Precedence Rule surfaces A single surface takes precedence over a whole quilt. Weighted Link Icon After you create a weighted link, Mechanica displays two graphical icons on your model—one for the weighted link and another for the degrees of freedom. Mechanica places the degrees of freedom icon on the independent side of the weighted link. The icon is a triad, with each leg of the triad representing the X, Y, and Z directions of the coordinate system you select. If you check any degree of freedom in any direction, Mechanica adds the appropriate indicator to the icon: • • Arrow head — Indicates a translational degree of freedom for the given direction. Ring — Indicates a rotational degree of freedom for the given direction. The degrees of freedom icon changes orientation depending on the coordinate system you select for the independent side of the weighted link. However, if you do not check the Override Coordinate System box on the Weighted Link Definition dialog box and do not select a new coordinate system for the independent side, Mechanica displays the legs of the triad parallel to the axes of the default WCS. This may not be correct if you have previously assigned a different displacement coordinate system to the same node. Reference Entities for Weighted Links You can select one of the following reference entities for the independent side of your weighted link: • Point(s) — Select this option to distribute a load or mass over a point/vertex or several points/vertices. You can create points as needed, or you can select any of the following: o a single point or vertex o a point feature (includes one or more single points) o a pattern of point features Edge(s)/Curve(s) — Select this option to distribute a load or mass over a single edge/curve or a number of edges/curves. You can select edges/curves or create curves as needed. If you choose to create a curve, Mechanica displays the Pro/ENGINEER CRV OPTIONS menu. Use this menu as you would in Pro/ENGINEER. Surface(s) — Select this option to distribute a load or mass over a single surface or a number of surfaces. You can select any of the following: o Individual — Selects one or more individual surfaces. • • 192 Structural and Thermal Simulation o o Surf Options — Displays the Pro/ENGINEER surface menus, which you use as you would in Pro/ENGINEER. Part Boundary — Selects the part boundary. Override Coordinate System for Weighted Links If you check the Override Coordinate System box on the Weighted Link Definition dialog box and then click the selector arrow, Mechanica opens the SIM CSYS SEL menu, which displays the following options: • • • Current — Selects the current coordinate system for the model. WCS — Sets the WCS for the model. Select — Enables you to select a coordinate system for the model. If you want to create a new coordinate system to use as a reference, use the Insert>Model Datum>Coordinate System command. Example: Bending Stiffness In the following figure if you do not define a contact to overcome the bending moment, the model will be under constraint. • In the figure below, Mechanica applied a boundary mesh to an assembly with offset-mated surfaces. The purple lines represent the gaps between the mesh nodes. 193 Structural and Thermal Simulation - Help Topic Collection • • If you select the Per Unit Area option under Distribution when you define your surface–surface gap, the software uses the total area of the first surface that you select to calculate the axial and transverse stiffness values. However, if the two surfaces that you select only partially overlap, the software first determines the portion of the first surface area that it can use to form a coincident mesh during meshing, and uses that area for the calculation of stiffness values. For example, in the illustration above, if you first selected the top surface on the lower, smaller box for your surface– surface gap definition, Mechanica would designate that surface for the Per Unit Area calculation. The actual value the software uses in the calculation would consist of only that surface area with the purple gap icons. A gap can be applied between two surfaces in a model containing shells compressed to midsurfaces. If you specify your model as a midsurface shell model, and the first surface you select for your gap undergoes midsurface compression to an edge, the software uses the area of the surface before compression for the distribution calculation. Rigid Link Icon After you create a rigid link, Mechanica displays two graphical icons on your model— one for the rigid link and another for the degrees of freedom. Mechanica places the degrees of freedom icon on the dependent side of the rigid link. The icon is a triad, with each leg of the triad representing the X, Y, and Z directions of the coordinate system you select. If you check any degree of freedom in any direction, Mechanica adds the appropriate indicator to the icon: • • Arrow head — Indicates a translational degree of freedom for the given direction. Ring — Indicates a rotational degree of freedom for the given direction. The degrees of freedom icon changes orientation depending on the coordinate system you select for the dependent side of the rigid link. However, if you do not check the Override Coordinate System box on the Rigid Link Definition dialog box and do not select a new coordinate system for the dependent side, Mechanica 194 Structural and Thermal Simulation displays the legs of the triad parallel to the axes of the default WCS. This may not be correct if you have previously assigned a different displacement coordinate system to the same node. Override Coordinate System for Rigid Links If you select the Override Coordinate System check box on the Rigid Link Definition dialog box and then click the selector arrow, Mechanica opens the SIM CSYS SEL menu, which displays the following options: • • • Current — Selects the current coordinate system for the model. WCS — Sets the WCS as the coordinate system for the model. Select — Enables you to select a coordinate system for the model. If you want to create a new coordinate system to use as a reference, use the Insert>Model Datum>Coordinate System command. Guidelines for Surface-Surface Connections and Interfaces (FEM mode) There are several types of connections and interfaces in FEM mode that you can create using two surfaces. These entities include: • • • • • Interfaces (FEM mode only) Beams Gaps Rigid links Perimeter welds To mesh your model successfully, you should keep the following points in mind when you create surface-surface connections and interfaces: • • • In most cases, the selected surfaces must belong to different parts in your assembly. If you are creating an interface, however, you can select a quilt surface and a solid surface on the same part. You cannot select two surfaces of different geometric types. For example, you cannot create a surface-surface perimeter weld between a cylindrical surface and a planar surface. If you want to create a solid mesh in which the meshes on the two surfaces are compatible, you cannot use offset mate constraints when you create the assembly in Pro/ENGINEER. If there is any offset between the mated surfaces, Mechanica will not generate a compatible mesh. 195 Structural and Thermal Simulation - Help Topic Collection Rotation and Separation When you define a fastener, you need to prevent unwanted movement about the fastener. You can choose how you want to eliminate unwanted degrees of freedom in your model: • Separation — In the real world, fasteners do not cause components to interpenetrate. So that your Mechanica model reflects this behavior, you must establish separation between the two components to ensure that the solver does not treat them as interpenetrating. You can establish separation by: • Defining a small contact region between the components. This method is the most accurate, but requires substantially more solver time. Note that the contact region must touch the edge of the hole on the inside fastener surface. • Allowing Mechanica to automatically define standard fastener separation when you create an advanced fastener. While this method yields faster solution times, it does not allow the components to separate even if they would naturally do so. If you do not enforce separation using one of these methods, the model will be underconstrained. In this case, the components may either interpenetrate or fly apart. Note that, for simple fasteners and for advanced fasteners that use point references, you do not need to specify anything in the fastener definition to ensure proper separation. For these fastener types, Mechanica assumes that there should be an enforced separation between the fastened components, and uses a contact region, if present, or standard fastener separation to prevent interprenetration. • Rotation — You should prevent the fastened components from rotating relative to each other about the bolt or screw axis. You can prevent rotation by: • • Creating constraints that eliminate all rotational degrees of freedom in the fastened components, adding more fasteners, or other means Allowing Mechanica to automatically prevent rotation when you create advanced fasteners If you do not prevent rotation using one of these methods, the model will be underconstrained. In this case, one or both components will spin and the solver will fail. Note that, for simple fasteners, Mechanica does not provide any automatic mechanism for preventing rotation as part of the fastener definition. Therefore, you need to add constraints or create one or more additional, appropriatelylocated fasteners. 196 Structural and Thermal Simulation Example: Fix Rotations The Fix Rotations option on the Fastener Definition dialog box allows you to decide if the two reference edges you select will be free to rotate against each other or not. In the figure, the model on the left has Fix Rotations activated while the model on the right does not. To create a bolt, the two holes must fully pierce the components and you must select the top hole edge of the top component and the bottom hole edge of the bottom component. Select the first curve to create the head of the bolt Select the second curve at the point where the nut rests against the second component The components will be linked as shown in the following figure. The two annular areas shown in green are twice the diameter of the bolt and the areas are connected to points Bt and Bb using weighted links. A very stiff separation spring connects point Bt to Bb and a spring between the points At and Ab. Points At and Ab are connected to their respective parts using weighted links that pass between the points and the respective orange surfaces. Simple bolts do not prevent rotations on the axis of the bolt. 197 Structural and Thermal Simulation - Help Topic Collection An example with separation set to off is represented in the following figure. You can select any combination of the six degrees of freedom. If you do not make any specific selection, Mechanica assumes that all degrees of freedom participate. • • T1, T2, T3 — These degrees of freedom specify translation of the node along an axis or axes of the coordinate system you select. R1, R2, R3 — These degrees of freedom specify rotation of the node about an axis or axes of the coordinate system you select. For information on correspondence between the axes in three coordinate systems, see Axis Equivalents in Different Coordinate Systems. Degrees of Freedom for Rigid Links Use the Degrees Of Freedom field on the Rigid Link Definition dialog box to specify the degrees of freedom for the dependent side of the link. You can select any combination of the six degrees of freedom. If you do not make any specific selection, Mechanica assumes that all degrees of freedom are allowed. • • T1, T2, T3 — These degrees of freedom specify translation of the node along an axis or axes of the coordinate system you select. R1, R2, R3 — These degrees of freedom specify rotation of the node about an axis or axes of the coordinate system you select. For information on correspondence between the axes in three coordinate systems, see Axis and Component Equivalents in Different Coordinate Systems. 198 Structural and Thermal Simulation Pass or Fail Results — 2D If the curves fail any of these checks, Mechanica does not create a contact region. If the curves pass, Mechanica places a contact region icon at the point where the curves are closest to each other, oriented along the vector between the points of closest approach. Pass or Fail Results — 3D If the surfaces fail any of these checks, Mechanica does not create a contact region. If the surfaces pass, Mechanica places a contact region icon at the point where the surfaces are closest to each other, oriented along the vector between the points of closest approach. About Interfaces In addition to end welds and perimeter welds, you can use interfaces to connect surfaces in an assembly model. When you create an interface, you specify how Mechanica will treat a particular pair of mated or overlapping surfaces during meshing and analysis. Mechanica provides two basic interface types—bonded and free. • • Bonded — Mechanica considers contacting surfaces as bonded. This means that matching nodes on contacting surfaces merge. Instead of two coincident nodes, a shared one exists. Free — Mechanica specifies that two surfaces have matching, geometrically consistent nodes, but does not merge the nodes. Meshes on the contacting surfaces are identical. As an exception for FEM mode only, you can also specify free interfaces where the nodes have no geometric consistency. To create an interface between components in your model, select the Insert>Connection>Interface command. The way you create interfaces and the interface type that Mechanica uses as a default differs depending on whether you are working in native mode or FEM mode. 199 Structural and Thermal Simulation - Help Topic Collection Example: Screw Fastener Use the Insert>Connection>Fastener command to create a screw fastener. Select Screw (edges of holes) for the references. Select the Type as Simple and select the edges as shown in the following figure In this example, the bolt type selected is simple. This means that the stiffness is defined by the materials and their geometries. A free connection is automatically added at the interface of the two parts to keep them from merging with each other. The bolt diameter is automatically set to be equal to the diameter of the smaller of the two holes. You can also manually change the value of the bolt diameter. Axial Stiffness Assumptions: • • • The axial stiffness acts in the direction along the bolt fastener. The bolt head diameter is assumed to be 1.7*(Bolt Diameter). The stiffness is calculated from the diameter of the bolt, the material, and the equivalent length of the screw, that is, the distance between the point At and point Ab. The Point Ab is at half the distance of the bottom hole. 200 Structural and Thermal Simulation Normal Stiffness Assumptions: • • Stiffness is in the direction perpendicular to the bolt (shear). Stiffness is calculated from the diameter of the bolt and the material. If you run such a model with a load that tries to separate the two components, then you will get results as shown in the following figure. 201 Structural and Thermal Simulation - Help Topic Collection Note that the cap lifts up from the bottom part, and that the two parts are not welded together and are held only by the screw fastener. The stress is due to the screw and not due to the contact between the cap and the bottom part. You must remember that an automatic free connection has been defined between the two mated surfaces and the cap and the bottom part interpenetrate. You can create a new traction model as shown in the following figure. 202 Structural and Thermal Simulation In the above figure, you can see that the two parts are stuck together as displayed by the red circle. Mechanica creates two annular areas on the mated surface and surfaces and a separation spring to enforce separation between these two areas. You use the separation spring to place a contact to ensure that the two parts do not . However, this separation spring may have the undesired consequence of forcing these two areas to remain in contact with each other, even though they should naturally separate. The state of the separation spring is recorded with a separation stress measure that is automatically created for each fastener. If the separation stress measure is negative, then the separation spring is acting as it should. On the other hand, if the separation stress measure is positive, then the spring is acting to hold the parts together as shown above. Alternatively, you may choose to define a contact region between the two parts that allows the parts to separate. This approach requires more calculation time than when using the separation spring. 203 Structural and Thermal Simulation - Help Topic Collection The two annular areas in green are created automatically. For simple fasteners, the diameter of these areas is twice the diameter of the bolt. And these are connected to the point Bt and Bb using weighted links, and a very stiff separation spring connects Bt to Bb. As explained earlier, the screw fastener is modeled as a spring between At and Ab and the points At and Ab are connected to their respective parts using weighted links that go between the points and the respective orange surfaces. These annular areas act as a form of mesh control enforcing smaller elements within its boundaries. For solid models, this surface mesh refinement extends into the volume. If the parts are not in compression, the separation stiffness carries some of the tensile load. For a simple type of fastener,you can add a contact region between the two mated surfaces. Note that in this case, you can run the analysis without the included contact regions selected or turn off separation for advanced fasteners. See the following figure without the included contact regions option selected. 204 Structural and Thermal Simulation Note the mesh refinement on the top surface where the screw head lies and also note that you get stress all along the hole in which the screw is tightened. The new properties options in the Fastener Definition dialog box are available only if you change the screw fastener type from Simple to Advanced. The options available to define the stiffness of the fastener are Using material and diameter and Using spring stiffness properties. In this case, the model may be underconstrained and the Structure engine may fail. The following example illustrates two versions of the model—the first, underconstrained, and the second, correctly constrained. 205 Structural and Thermal Simulation - Help Topic Collection In the first example, both parts are solids, so there is no need to constrain the component rotations. However, the constraint for part b allows translation in the X and Y directions, thus failing to prevent part b from rotating about the fastener axis. In the second example, both parts are fully constrained so there is no unwanted rotation. Even though the parts cannot rotate, you can still model realistic behaviors like flexion at the fastener by placing a force load on the front surfaces near the centerline of the fastener holes. The examples just discussed involve fixing rotations using constraints, but you can also fix rotations by adding other fasteners, provided you consider extra fasteners acceptable for your model and your model includes reference geometry. 206 Structural and Thermal Simulation Example: Intervening Geometry The components you connect with bolts or screws must fasten directly, with no intervening geometry. The following illustration shows two common forms of intervening geometry that you need to avoid if you are creating fasteners and, for contrast, also shows a valid fastener assembly: In the invalid 3-component assembly, part a and part c are fastened with a bolt or screw. Part b lies between parts a and c, directly in the fastener path, causing problems with the fastener path regardless of the fact that, in a physical model, the bolt or screw could easily pass through all 3 parts. The invalid 2-component assembly presents a similar situation—in this case, with the lower horizontal member of part a causing the problem. Again, this construction would not present any issues in a real world environment, but Mechanica considers it invalid. As you can see, the valid assembly includes two components, one of which incorporates two spacers. Note that, while the spacers enforce a distance between the two components, the fastener path includes no interfering geometry. Because the fastener path is clear, you can model the connection between the two components using a bolt or screw. 207 Structural and Thermal Simulation - Help Topic Collection Example: Carries Shear Use the Carries Shear option on the Fastener Definition dialog box to specify that the fastener carries the shear force that passes through the fastener connection. If you clear this option, the fastener does not carry the shear force. Instead, Mechanica assumes that the shear force passes through the components by friction where the components meet. The figure represents two screw fasteners under pure shear stresses. In the model on the left,the shear passes through the components. Note that the bottom component bends. In the model on the right, the shear passes only though the screw. This is useful for shell models but can be used for solid model too,for example if you have a model with no holes, you must consider the following points: • • • The components must not touch each other and a gap must exist between the parts if they are quilts. Fasteners cannot be of zero length The order of selection of the points is not important. Axial Stiffness The diameter of the nut is the same as the diameter of the bolt head. Normal Stiffness The reaction is applied to points between which the fastener is defined. 208 Structural and Thermal Simulation Fix Separation Stiffness Fix separation stiffness is automatically set to On as you cannot define a contact between shells. Mechanica defines a Z direction normal to this XY plane, and defines a Y direction that is perpendicular to the X and Z vectors. The X vector for a gap is defined by the gap length, which is the shortest distance between the entities used to define the gap. For a zero-length gap, the X direction is normal to the surface. You can define the Y direction of a gap by selecting any of the following entities on your model: • • • • • • Point — Defines the XY plane with the gap X vector and the selected point. Edge — Defines the XY plane with the gap X vector and the projection from the first point of the gap to the selected edge. Curve — Defines the XY plane with the gap X vector and the projection from the first point of the gap to the selected datum curve. Axis — Creates a line through the first point of the gap, which is parallel to the selected axis. The parallel line and the gap's X axis form the XY plane of the gap. Surface — Defines the XY plane with the gap X vector and the projection of the first gap point to the selected surface. Vector in WCS — Defines the XY plane with the gap X vector and a line projected from the first gap point in a direction parallel to the X, Y, or Z vector in the WCS. The default vector is 0, 1, 0, which defines the Y direction in the WCS. Not defined — The gap definition does not include a Y direction. You cannot select this option if you output to the NASTRAN solver. Mechanica blocks output to NASTRAN if the Y direction for gaps in the model is not defined. • Reviewing Contact Regions Use the Info>Review Contacts command to examine contact regions that you define. When you select this command, Mechanica prompts you to select the contact region you are interested in. Mechanica then highlights the edges and surfaces associated with the contact region so that you can ensure that you used the correct geometric entities to model the contact area. This function is particularly handy for large or complex models where the risk of inadvertently selecting the geometry that does not participate in the contact region can be higher. 209 Structural and Thermal Simulation - Help Topic Collection Idealizations About Idealizations You create idealizations to represent your model with a set of elements that simplifies the actual design, resulting in a faster simulation. Idealizations are a means of fine-tuning the design of your model. Mechanica provides these idealizations: • • • • Shells Beams Masses (Structure only) Springs (Structure only) Shells About Shells Use shells to model a thin layer of a defined thickness for your part. If your part is relatively thin compared to its length and width, shell modeling is more efficient. You have several options for including shells in your model: • • • Create a single shell as a layer on a solid. In this case, you can define the shell as a composite of layers, or specify the material and thickness. Create a shell pair based on the surfaces in your part. The software compresses the pair to a midsurface that it uses in the analysis. Create a volume-based shell that has specific material or thickness properties. In this case, the software compresses your model to a midsurface. But, it uses the material and thickness definitions of the shell rather than that of the surfaces associated with the volume for the midsurface thickness. You create both single shells and shell pairs using the Insert menu. The command you select differs depending upon whether you want to create single shells or midsurface compressed shells: • If your design includes shells that are made of the same material as your part, use the Insert>Midsurface command to create shell pairs. To create a shell pair in this way your model must include at least two surfaces on opposite sides of a volume. When Mechanica analyses a shell model, it compresses shell pairs to a midsurface or set of midsurfaces. To perform midsurface compression, Mechanica requires a pairing scheme. To ensure the successful analysis of your shell model, you should check the shell compression before you run an analysis. 210 Structural and Thermal Simulation • If you want to create a single shell, for example as a layer on a solid, or if you want to create a shell pair that is composed of a different material than the rest of your part, or if you want to include properties such as laminates or material orientation, use the Insert>Shell command. You may choose to design a model solely with midsurface compressed shells, or your design may benefit from a mixture of shells, solids, beams, and other idealizations. If you are working with midsurface compressed shells, before you begin analysis, you should define your model as a solid, as a shell, or as a mixed model. The model type determines how Mechanica analyzes your part. Before you create shells on your model, read about recommended geometry for your model. You can control the visibility of shells on your model by using the View>Simulation Display command, or by placing them on layers. After you create a shell, you can edit or delete it by right-clicking on the shell idealization—either Shell Pair or Shell—in the model tree and using Edit Definition or Delete command, as appropriate. If you are deleting a shell, Mechanica asks you for confirmation first. Standard Shells Shell Definition Use the Insert>Shell command to define a simple or advanced shell on a model surface. Simple shells differ from advanced shells in this way: • • Simple — A simple shell is of uniform thickness. If you select Simple as the shell type, you can define a thickness and a material for the shell. Advanced — An advanced shell can be homogenous, or have laminated properties. If you select Advanced as the shell type, the software displays fields prompting you to define its shell property, material, and material orientation. When you select the Insert>Shell command, Mechanica displays the Shell Definition dialog box, which includes: • • Name — Specify a name for the shell. The software provides default names, such as Shell1, Shell2, and so on. You can change these default names to more meaningful names if you like. Surface(s) — Specify the surfaces associated with the shell. If you already selected a valid surface or surfaces for the shell before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. Otherwise, use the selector arrow and the regular selection methods to choose the surfaces. When you select the surface, you can change the normal direction of the shell. 211 Structural and Thermal Simulation - Help Topic Collection Note: The software shares data across several selected surfaces or quilts. Therefore, if you change data on one surface or quilt with shared data, the others will be affected as well. • Type — Specify either Simple or Advanced. The remaining fields on the dialog box change depending on your selection. Simple Shells After you have specified a name, associated surfaces, and the Simple shell type, you need to provide Mechanica with the following information as well: • Thickness — You can specify the thickness of your shell as a numerical value. A numerical thickness is measured in the principal system of units that is associated with all of your modeling activities. When Mechanica creates the shell elements for the surface, it applies the thickness you specify equally on both sides of the selected surface. For example, if you specify a shell thickness of 1, Mechanica places 0.5 on the top side of the surface and 0.5 on the bottom side. The thickness field is a parameter-capable edit field. This field accepts Pro/ENGINEER parameters, which you can select from a displayed list. You can also enter an expression as a thickness value. The shell thickness you assign to an individual quilt surface overrides any other thickness that might be assigned to that quilt surface as part of another shell definition. • Material — Specify the material of the shell. Click the arrow to display a drop-down list of material properties already associated with your model. If you do not see what you want in the drop-down list, use the More button to display more materials, or to create a new material. You can only use isotropic materials with simple shells, so the drop-down list contains only those. If you select a non-isotropic material after clicking the More button, the software reminds you that you must use isotropic material properties with simple shells. To Define a Simple Shell This procedure assumes that you are working with the Shell Definition dialog box and have selected Simple in the Type area. 1. Enter a real-number value for the Thickness of the shell. 2. If you want to use a Pro/ENGINEER parameter for the thickness, click P. The Select Pro/ENGINEER Parameter dialog box appears with a list of available parameters. Select an existing parameter, or click Create to define a new one. 212 Structural and Thermal Simulation 3. Select a material from the drop-down list. If you do not see the material you want, click More to select a material from the library or to define a new one. 4. Click OK to accept the shell definition. Advanced Shells After you have specified a name, associated surfaces, and the Advanced shell type, you need to provide Mechanica with the following information as well: • Shell Property — Click the arrow to display a drop-down list of shell properties already associated with your model. If you do not see what you want in the drop-down list, use the More button to open the Shell Properties dialog box, where you can define a new shell property, name it, and specify its type and thickness. Material — Click the arrow to display a drop-down list of material properties already associated with your model. If you do not see what you want in the drop-down list, use the More button to display the Materials dialog box, where you can assign a material from the library to your model, or define a new material. The Material drop-down list may not be active if you select certain shell properties. For example, if the shell property you select is a laminate layup, the Material drop-down list is not active. • Material Orientation — Click the arrow to display a drop-down list that shows the material orientations on the surfaces of your model. If you do not see what you want in the drop-down list, use the More button to display the Material Orientations dialog box, where you can assign a material orientation to your shell, or create a new orientation. • To Define an Advanced Shell This procedure assumes that you are working with the Shell Definition dialog box and have selected Advanced under Type. 1. Select a Shell Property from the drop-down list. If you do not see a shell property that you want in the list, click More to select a shell property from the library or to define a new one. 2. Select a Material from the drop-down list. If you do not see a material that you want in the list, click More to select a material from the library or to define a new one. 3. Select a Material Orientation from the drop-down list. If you do not see a material orientation that you want in the list, click More to select a material orientation from the library or to define a new one. 4. Click OK to accept the shell definition. 213 Structural and Thermal Simulation - Help Topic Collection Midsurface Shells Before You Define a Shell Model Before You Define a Shell Model Before you define your part as a shell model, be sure you have all the geometry you need already in place. Following are several factors you should be aware of when working with shell models: • Regions — If you plan to use loads or constraints for surface regions, be aware that adding a region invalidates any prior shell definitions for that surface. Therefore, be sure to add all regions and parent surfaces before starting the shell model definition process. As an alternative, you can redefine shell definitions after you add the region. For more information, see Surface Region. Variable Thickness — In FEM mode, your part can have a variable thickness. In native mode, Mechanica does not perform shell modeling for surfaces that have a variable thickness. If any of the surfaces you plan to model have a variable thickness, redesign the surface or suppress the associated feature. For more information on surface thickness, see Model Thickness. Properties — You can assign shells to faces, regions, or datum surfaces, and to surfaces that will be compressed. The assigned shells can then reference shell properties you define. You can also define a shell property that is not assigned to any entity. For more information, see About Shell Properties. Complex Models — Simplify your model as much as possible before defining it as a shell model. Keep your model's geometry symmetric whenever possible. Be sure to suppress any features that have no bearing on the analysis of the part. You can start by identifying areas of the model that have minimal significance in terms of carrying the load. In those areas, suppress features that serve cosmetic purposes only. Feature suppression reduces the following: o o the amount of time required to define surface pairs. Also, you can sometimes reduce the amount of complex geometry you may need to add in order to accommodate your pairing scheme. the time required to analyze the model by reducing the number of calculations the engine needs to complete • • • When determining which features to suppress, weigh the benefits of suppressing the feature against the reduction in model accuracy. • Unopposed Surfaces — Make sure all surfaces you shell pair have an opposing surface. 214 Structural and Thermal Simulation Pairing Schemes Mechanica uses the surface pairs that you define to form a network of compressed surfaces called the midsurface. When it models your part, the software places elements on the midsurface only, using the thickness associated with each portion of the shell to determine the depth of the elements. For example, if you were modeling a T-bracket, you might take the approach shown in the T-Bracket example. Mechanica highlights the first surface or set of surfaces you select for a pair in red and the opposing surface or surfaces in yellow. The red surface acts as a point of reference for the pair. Mechanica uses this surface as a viewpoint when determining which opposing surfaces in the model are part of the pair. In addition, Mechanica defines the normal direction for a compressed midsurface from the red surface to the yellow surface. If you omit opposing surfaces from your model, Mechanica compresses the model differently than if you include all opposing surfaces. Mixed Models Certain models contain some areas best suited for shells and others best suited for solids. For these models, you can create shell pairs for the areas that you want Mechanica to treat as shells. Then, you use the following commands on the MIDSURFACES>COMPR OPTS menu to get an idea of how Mechanica will treat your model during analysis, provided you select the equivalent meshing options in native mode and FEM mode. • Shells Only — Select this command if you want to view what your model would look like if you have Mechanica treat it as a pure shell model. In this case, the software applies shell elements to the paired portion of the model at analysis time and omits any unpaired portions from analysis. Shells And Solids — Select this command if you want to view what your model would look like if you have Mechanica treat it as a mixed model. In this case, the software applies shells to the paired portion of the model and solids to the unpaired portion. This is the default option. • Once you have decided whether you want Mechanica to treat the model as a pure shell model or a mixed model, you can use the Midsurface or Solid/Midsurface option box on the AutoGEM menu to indicate your choice to the mesher and, consequently, the solver. 215 Structural and Thermal Simulation - Help Topic Collection Model Thickness Mechanica uses the thickness associated with each midsurface to calculate the thickness of the shell elements. If it encounters unopposed surfaces in your model, the software uses the thickness of a neighboring or related pair to define the thickness for that portion of the model. Mechanica supports shell pairs with both constant and multiconstant thickness. • • Constant-thickness pairs — All opposing paired surfaces are parallel to each other and equidistant from the opposing surface. Multiconstant-thickness pairs — One or both of the opposing surfaces include multiple surfaces. Although all the surfaces are parallel to the opposing surface, they are not equidistant from the opposing surface. Your model is a good candidate for use with multiconstant thickness if: o o it does not require high accuracy or solution quality near the multiconstant-thickness pairs its behavior is not sensitive to minor shape changes When it encounters surfaces with multiconstant-thicknesses, Mechanica compresses the bottom surfaces and top surfaces into a single continuous midsurface. • Variable thickness pairs (in FEM mode) — Both opposing surfaces are neither parallel nor concentric. If you decide that your model is not a good candidate, rework the part geometry in Pro/ENGINEER to improve midsurface coincidence or treat the model as a solid instead of a shell. Unopposed Surfaces For Mechanica to create a complete shell model, you need to make sure all the surfaces you pair have an opposing surface. Unopposed surfaces can be the result of omitting a surface or surface region from a pair, or they can occur because of slight geometrical differences between surfaces that make up a pair. You can use any of the following approaches to resolve problems due to unopposed surfaces: • If the unopposed surface is a separate feature, such as a round, you can suppress the feature. 216 Structural and Thermal Simulation • • You can elect to use or ignore unopposed surfaces during analysis through the COMPRES MDL menu. If you choose to ignore these surfaces, Mechanica omits the unopposed surfaces from your model, and your model may have gaps. To understand how the midsurface compression of a part may differ depending upon whether you use or ignore an unopposed surface, see Example: Part with Unopposed Surfaces. You can add an opposing surface to the model. Model Entities and Idealizations Mechanica supports the same modeling entities and idealizations for both solid and shell models. However, because Mechanica redefines geometry during midsurface compression, you need to exercise care when placing these items. Be aware of the following factors when planning modeling entities and idealizations for shell models: • You cannot place certain types of loads or constraints on entities whose type changes when Mechanica compresses the model. The loads and constraints that fall into this category are loads distributed or applied based on unit type. For example, a force load with a distribution of Force Per Unit of Length or Force Per Unit of Area falls into this category, but a force load applied with a Total Load distribution does not. Other types of loads and constraints in this category include interpolated loads, bearing loads, heat loads distributed based on unit type, pressure loads, and convection conditions. Following are examples of entity-type changes that invalidate these types of loads or constraints: o compressing a loaded or constrained surface to a curve. There is one exception—surface constraints that have fully fixed translations with no prescribed displacements. In this case, Mechanica compresses the surface constraint to an edge constraint whose translations and rotations are fully fixed. compressing a loaded or constrained surface region to a partial curve, unless you applied the load or constraint to the curve instead of the region as a whole compressing a loaded or constrained curve to a point o o For example, if you decide to model a rectangular plate as a shell, Mechanica would ask you to redefine the problem load. • • • If you place regional loads on both pair surfaces and those loads overlap, Mechanica calculates the overlapping area by adding or subtracting the load values and directions for the two regions. Mechanica maintains constraints applied to overlapping regions. If you place a constraint or load on a region and omit the region when you define your pairs, the software may not include that constraint or load. In this case, Mechanica displays a warning message when you try to analyze the model. 217 Structural and Thermal Simulation - Help Topic Collection Gaps in Parts Depending on how you pair your single-part model, Mechanica can encounter gaps in the midsurface. A gap is a section of the model where the midsurfaces do not meet. Gaps often occur in portions of a solid model that are not symmetric. In asymmetric models, various sections of the model have different thicknesses and the midsurfaces of the sections do not coincide. Thus, if you define individual shell pairs for each thickness, the midsurfaces do not meet. In addition, gaps can occur in Pro/SHEETMETAL models, depending on how you create your features. This situation results from the fact that Pro/SHEETMETAL does not typically merge common feature faces, or wall junctions. In the solid following model, there are two gaps: Be aware that no modeling information passes between gaps. For example, if you create a constraint set that fixes the far end of section a for the model shown above, sections b and c would not see this constraint. Gaps can cause problems during analysis. If Mechanica analyzed the example model using the constraint set just described, the software would interpret the model as three independent bodies, only one of which is constrained. Because the model contains unconstrained bodies, Mechanica would display an error message and halt the analysis. You can correct this problem by inspecting the model closely for gaps. When you locate a gap, you can do one of the following: • Use the Multiconstant Thickness command to redefine pairs for the surrounding geometry. For more information on this command, see Model Thickness. When you define multiconstant-thickness pairs for asymmetric models, slight shape differences can occur between the Pro/ENGINEER part and the model analyzed by Mechanica. Before using multiconstant thicknesses, determine whether this type of shape change is acceptable in terms of the results you want Mechanica to provide. 218 Structural and Thermal Simulation • • • Rework the part geometry in Pro/ENGINEER to improve midsurface coincidence. Treat the model as a solid instead of a shell. For Pro/SHEETMETAL, rework the features using the Merge Walls command. For information on merged walls and how to create them, search the Sheetmetal functional area in the Pro/ENGINEER Help Center. Gaps in Assemblies For assemblies, gaps typically occur at locations where two parts meet or overlap. Pro/ENGINEER assembly constraints are such that Mechanica treats an assembly as a single body for solid modeling. However, when you treat an assembly as a shell and perform midsurface compression, Mechanica sees more than one body, resulting in a gap. For an analysis of a model to be accurate, you must correct these gaps so that the parts of the assembly move together as if they were a single body. For assemblies, the likelihood of gaps caused by midsurface compression is greater than it is for single parts because an assembly can have gaps between parts as well as within a particular part. For an example of an assembly that has a gap caused by midsurface compression, see Example: Assembly Model with Gap. To find gaps in your model, be sure to perform a compression test before starting an analysis. To avoid gaps in assemblies, you must make sure the midsurfaces of the parts connect. You can correct assembly gaps in various ways depending on your model geometry and sensitivities. Here are some methods you can consider: • In native mode, Mechanica creates automatic midsurface connections wherever two components have mated or overlapping surfaces. When you mesh your model, these connections appear as dotted magenta lines along the edges of all connected curves and surfaces. If your meshed model shows automatic midsurface connections in areas where you do not want them, define free interfaces for these areas. In general, you should use automatic midsurface connections only if the size of the connections is small relative to the size of the model. In a model that uses automatic midsurface connections to connect two overlapping surfaces that are subject to displacement, Mechanica can give results that do not reflect the actual displacement. For a comparison of the expected results versus the actual results, see Results When Using Automatic Connections. • • • • You can use end welds, perimeter welds, or, in native mode, spot welds. You can use a rigid connection. You can use a fastener. You can use the Pair Place command on the MODIFY PAIR menu to define the midsurface placement so the midsurfaces of the parts touch in the merged area. This can result in coincident curves and surfaces, which can cause meshing problems. 219 Structural and Thermal Simulation - Help Topic Collection When you start your first analysis or design study for an assembly, you should request error checking. Among other things, error checking includes a count of the disjoint bodies in the assembly. If Mechanica finds multiple disjoint bodies during error checking, your assembly may have gaps that you should consider before progressing further. The software does not consider spot welds when determining the number of disjoint bodies. Note: Do not confuse the term gaps as discussed here with the gap idealizations that you can create in FEM mode. Shell Model Development Defining Solid or Shell Models You can define your model as a solid, as a shell, or as a mixed model. The model type determines the type of elements Mechanica uses to define your part. • • A solid model is a part that you model using solid elements like tetrahedrons, bricks, or wedges. A shell model is a part that you model using shell elements like triangles and quadrilaterals. Typically, you use shell modeling when your part is relatively thin compared to its length and width. To meet Mechanica's criteria for shell models, your part must have either a constant or multiconstant thickness in native mode. In FEM mode, your part can have a variable thickness. You can change the elements used for modeling with the AutoGEM>Settings command in native mode or the Mesh>Create command in FEM mode. For example, you can direct Mechanica to use only triangles to model your native mode shell model rather than using both triangles and quadrilaterals. • A mixed model is a combination of both a solid and a shell model, where some areas of the model are better suited to shell elements and others are better served by solid elements. In native mode, Mechanica treats all models as solid models by default. To direct Mechanica to treat your model as a midsurface shell model, or as a mixed model, you first need to define the model, or some areas of it, using midsurface shells. Then, use the following options buttons to indicate how Mechanica should mesh and analyze the model: • To direct Mechanica to mesh and analyze your model as a shell model, select the AutoGEM>Midsurface option button. The Midsurface command is selected by default when you create shell pairs, but if you start a new session of Mechanica with a model for which you created shells, you should check the setting. For example, if you have defined shell pairs for the surfaces in your model, but want to analyze the model as a solid without deleting the shells, you would select the AutoGEM>Solid command instead. 220 Structural and Thermal Simulation • To direct Mechanica to mesh and analyze your model as a mixture of midsurface shells and solids, select the AutoGEM>Solid/Midsurface option button. In FEM mode, the way you indicate how you want Mechanica to treat models that include midsurface shells is different. In this case, you select the model treatment when you create the mesh. Specifying Mesh Treatment for Models with Midsurfaces The Solid, Midsurface, and Solid/Midsurface options on the AutoGEM menu let you specify whether Mechanica will treat models that include midsurfaces as solid models, midsurface shell models, or a mixture of both during meshing and analysis. These toggle keys are only available in the native mode. In the FEM mode, you indicate model treatment at the time you create the FEM mesh. In models that have no midsurfaces, the Solid option is turned on and the Midsurface and Solid/Midsurface options are deactivated. However, when you define shell pairs for your model, the software automatically activates these two options and turns on the Midsurface option. Provided that you keep the option on, Mechanica meshes and analyzes the model as a shell model. If any potion of the model is a solid, Mechanica omits that portion from the mesh and, consequently the analysis. If you want to include the solid portions of the model, turn on the Solid/Midsurface option instead. For models with midsurfaces, the Midsurface option stays on by default unless you select one of the other two options and then save your model in that state. If you delete all the shell pairs in your model, Mechanica automatically turns off and deactivates the Midsurface and Solid/Midsurface options, reverting to the Solid option. MIDSURFACES Menu When you select Insert>Midsurface, the MIDSURFACES menu appears. From this menu, you can use the following commands: • • • • • • • Auto Detect — This command automatically creates shell pairs by pairing any suitable surfaces. New — This command lets you specify the shell thickness type and select the surfaces that are to be paired. Edit — This command takes you to the MODIFY PAIR menu, where you can edit an existing shell pair. Show — This command lets you display the surfaces included in a shell pair. At the same time, the software displays a message telling you the thickness type associated with the shell pair. Delete — This command lets you delete a shell pair from the model. Compress — This command lets you compress the shell pair to its midsurface to review the result of compression. Done/Return — This command returns you to the previous menu. 221 Structural and Thermal Simulation - Help Topic Collection To Create a Midsurface You create a midsurface by pairing two surfaces. Mechanica creates a midsurface from the surface pair and assigns shell elements to them. 1. Select Insert>Midsurface or click . 2. Select one of the following commands: o Auto Detect — Select this command to automatically pair any surfaces that can be automatically created. o New — Select this command to manually pair surfaces. 3. Select Constant to define a constant-thickness pair or Multi Const to define a multi-constant-thickness pair. In FEM mode, select Constant or Variable. 4. Select the surfaces you want to include in the pair. 5. Select Show to review the model's pairing scheme. 6. Select Compress to review the midsurface compression and check for errors. 7. If you find any unpaired surfaces that you do not want to treat as a solid, repeat the appropriate procedures from step 2. MODIFY PAIR Menu When you select Insert>Midsurface>Edit, the MODIFY PAIR menu appears. From this menu, you can use the following commands: • • Edit Pair — This command lets you add or delete a surface from a pair. Pair Place — This command lets you change the placement of the surface pair to any of these locations: o the red surface of the surface pair o the yellow surface of the surface pair o the midsurface o a selected surface, which can be a datum surface For any of these choices, you can click the Adj Tan Nbrs button to change the placement of any neighboring surface pairs that are adjacent and tangent to the surface pair you are modifying. • • Flip Pair — This command lets you swap the red and yellow surfaces in order to flip the resulting mesh normal. Thick Type — This command lets you specify whether the thickness of the surface pair you select is constant (the default value) or multiconstant. Shell Compression Mechanica processes all solid models as single volumes. However, the software uses a different approach when processing models with paired shells. With shell models, Mechanica compresses the model to a midsurface or set of midsurfaces. To perform midsurface compression, Mechanica requires a pairing scheme for the surfaces you want to model. 222 Structural and Thermal Simulation To Test Shell Compression Testing shell compression lets you identify problem areas in your model, specifically pairing errors. Run this test before you run your analysis so that you can see the midsurface that Mechanica has developed from your pairing scheme. 1. Select Insert>Midsurface>Compress. Mechanica displays the COMPR OPTS menu. 2. Select one of these options to tell Mechanica how to analyze your model: o Shells only o Shells and Solids 3. If it encounters unopposed surfaces in your pairing scheme, Mechanica displays a warning message and a diagnostic version of the COMPRES MDL menu. If you see this diagnostic menu, see To Handle Unopposed and Unpaired Surfaces. 4. Select one or more commands from the COMPRES MDL menu. 5. Examine your model to determine whether there are any errors in your pairing scheme. Pay special attention to gaps in the midsurface, paired areas where Mechanica did not generate a midsurface, and areas where you may have selected the wrong surfaces to pair. If there are gaps in your model, see either Gaps in Parts or Gaps in Assemblies. 6. Select Done from the COMPRES MDL menu when you finish reviewing the compressed model. 7. Be sure to correct any pairing problems using the commands on the MODIFY PAIR menu. To Handle Unopposed and Unpaired Surfaces If it finds any unopposed or unpaired surfaces during the compression test, Mechanica displays a warning message, highlights the surfaces in question, and displays a version of the COMPRES MDL menu that includes commands you can use to direct how the software processes the model. 1. If you want to display a particular aspect of model compression, select one or more of the commands on the COMPRES MDL menu. 2. If you want to redefine your pairing scheme or geometry to correct a problem, complete one of the following steps: o If Mechanica (FEM mode only) provides the Paired Only and Abort commands, select Abort. o If Mechanica provides the Done command, select Done. Mechanica closes the COMPRES MDL menu. You can then return to the MIDSURFACES menu to modify your pairing scheme. 3. If you want to work with the model as is, review the state of the UseUnopposed check box. 223 Structural and Thermal Simulation - Help Topic Collection COMPRES MDL Menu Mechanica displays the COMPRES MDL menu if it finds unopposed or unpaired surfaces during the compression test. From this menu, you can select one of the following commands: • • • • • IGES — creates an IGES file that represents the shell model. You must specify a coordinate system before the IGES file creation takes place. SUPERTAB — creates a SUPERTAB universal file that represents the shell model. ShowCompress — displays the compressed midsurface. Mechanica highlights the midsurface in yellow, unopposed surfaces in cyan, and surfaces that may be missing from a pair in red. ShowOriginal — displays the original model geometry. Mechanica highlights the original three-dimensional geometry in green and surfaces that may be missing from a pair in red. Show Both — displays the original model geometry and compressed midsurface. Mechanica highlights the original three-dimensional geometry in green, the compressed midsurface in yellow, and surfaces that maybe be missing from a pair in red. Show Paired — displays the paired surfaces only, if you have both paired and unpaired surfaces in your model. The unpaired surfaces (shown in red) disappear when you select this command. • If your model includes unopposed surfaces, the UseUnopposed check box appears on this menu, and is selected by default. Clear this check box if you do not want Mechanica to include unopposed surfaces during analysis. UseUnopposed Check Box The UseUnopposed check box on the COMPRES MDL menu tells Mechanica whether to include unopposed surfaces during analysis. If you select this check box, Mechanica keeps the unopposed surfaces as part of the analyzed model, and assumes that the intended pair surface is parallel to the unopposed surface. The on state is the default state for this toggle. Mechanica reverts to the default state each time you select Compress from the MIDSURFACES menu or exit the Mechanica menu structure. If you do not select this check box, Mechanica disregards any unopposed surfaces during analysis. In effect, this state results in the elimination of these surfaces and any associated midsurfaces from modeling. The software uses the thickness of a neighboring or related pair to define a thickness for the unopposed surface. Thus, Mechanica may sometimes calculate pair thickness at a different value than the pair's true value. When using unopposed surfaces, be aware that, if you place a constraint or load on the surface that was missing from the pair, Mechanica may not include that 224 Structural and Thermal Simulation constraint or load. In this case, Mechanica displays a warning message when you try to analyze the model. Note: You can change the default state of the UseUnopposed toggle by editing your config.pro file. To learn about config.pro options that affect shell compression, see Configuration File Options. To Create Shells 1. Select the Insert>Shell command or click The Shell Definition dialog box appears. 2. Enter a name for your shell, or accept the default name. 3. If you did not select geometry before opening the dialog box, click and use the regular selection methods to select the geometric references now. 4. Select one of the Types. The options on the dialog box are different depending upon your choice. Click each type for more information. o Simple o Advanced . Beams About Beams A beam is a one-dimensional idealization that, in three dimensions, represents a structure whose length is much greater than its other two dimensions. You create a beam by specifying the cross-section shape and position, the degrees of freedom at the beam ends, and the location of the beam with respect to the axis where Mechanica applies the beam load. Mechanica sees beams slightly differently in native mode and FEM mode. • • Native mode — A beam has a constant cross section that maintains the same dimensions from end to end. When you define your beam, you specify the section shape and size, and the orientation for the start of the beam only. FEM mode — A beam can have a variable cross section. In other words, you can create a tapered beam, in which the starting end has one dimension or shape and the terminal end, another. You can also select a different section shape and a different orientation for the beam beginning and end. If your beam has different section shapes at the two ends, Mechanica interpolates the cross section. FEM mode allows you to create trusses as well as beams. When you select the Insert>Beam command, the Beam Definition dialog box appears. Use this dialog box to create beams in native mode, and to create beams and trusses in FEM mode. After you create a beam, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a beam, Mechanica asks you for 225 Structural and Thermal Simulation - Help Topic Collection confirmation first. To manage beam sections, orientations, and releases, use the Properties menu. There are three coordinate systems that govern the way Mechanica defines and analyzes beams. To understand how to use these coordinate systems to design your beams and to obtain the desired results for your beam read Beam Coordinate Systems. You can control the visibility of beams on your model by using the View>Simulation Display command, or by placing them on layers. Beam Coordinate Systems When you create a beam in Mechanica, one of the properties you can specify is beam orientation. The beam orientation affects how your beam relates to the axis where the software applies loads, and how the software calculates results. To understand how to specify beam orientation, you must first understand the three different beam coordinate systems that Mechanica uses: • • • Beam Shape Coordinate System (BSCS) — The software draws the beam sections with respect to the beam shape coordinate system. Beam Action Coordinate System (BACS) — The software applies loads to beams at locations defined with respect to the beam action coordinate system. Beam Centroidal Principal Coordinate System (BCPCS) — The software defines the BCPCS based on the beam section, and reports most of the results in this coordinate system. When you create your beam, you use the Y Direction option on the Beam Definition dialog box to specify how the BACS relates to the WCS. You can then offset the BSCS from the BACS by using the options on the Beam Orientation Definition dialog box. Creating Beams Beam Definition Dialog Box When you select the Insert>Beam command, the Beam Definition dialog box appears. Use the following items on this dialog box to define your beam or truss: • References — Specify the geometric entities for your beam. If you already selected valid geometric references for the beam before entering the dialog box, your selections appear next to the selector arrow when the dialog box opens. Otherwise, use the selector arrow and the regular selection methods to choose the desired geometry. Material — Specify the material Mechanica uses to create the beam. Type — In FEM mode only, specify the type of beam you want to create— either a beam or a truss. If you create a truss, you do not need to specify Y direction, orientation, or release. • • 226 Structural and Thermal Simulation • • • Y direction — Specify the orientation of the Y axis for the beam action coordinate system. Start and End tabs — Define the start and end properties for beams. In FEM mode, you can specify different section and orientation properties for the two ends of your beam. However, in native mode, you can only specify section and orientation properties for the beam start. These tabs include the following items: o Section — Define the cross-section properties for beams and save sections in a library. o Orientation — Specify the orientation of the beam shape coordinate system with respect to the beam action coordinate system. o Release — Specify the degrees of freedom at each beam end. Extra tab — In FEM mode only,define, stress relief factors and specify whether to include stress recovery information. When you create a beam or a truss, Mechanica displays an icon on your model that includes a line representing the beam X axis and a figure representing the beam cross section. To learn how FEM mode's FEA solvers treat beams, see ANSYS and MSC/NASTRAN. Beam References The geometric entities that you use for your beam define the location and direction of the beam X axis. Select one of the following reference types on the Beam Definition dialog box to define the location of your beam on your model: • • • Point–Point — Create a beam between two points or vertices, or any combination of the two. The positive direction of the beam goes from the first selected point to the second. Point–Surface — Create a beam between a point or vertex and a surface. The positive direction of the beam goes from the point to the surface. Point–Edge — Create a beam between a point or vertex and an edge. The positive direction of the beam goes from the point to the edge. Note: For the location of the beam end positioned on the surface/edge, the software selects the spot that is closest to the first point of the beam. If you need to position the beam at a particular place on the surface/edge, use the Point-Point option and create a datum point along the surface/edge. • • • Point–Point Pairs — Create multiple point-to-point beams with the same characteristics. Chain (feature/pattern of points) — Create a beam that runs along a sequence of points. Edge/Curve — Create a beam that runs along an edge or a curve. You can select multiple curves and edges with which to associate a beam. To indicate the direction of a beam, Pro/ENGINEER displays a purple arrow at the center of each selected edge or curve. To invert the direction of an already-selected edge or curve beam, click on it again and the software redraws the arrow. 227 Structural and Thermal Simulation - Help Topic Collection If you select a curve that is not straight, the beam X axis lies along the length of and tangent to the curve. The Y direction is in the plane of the curve. If you select a vector direction for the Y direction that is not within the plane of the curve, Mechanica chooses the closest direction within the plane, or perpendicular to the plane. • Surface–Surface (Beam contact) — Create a beam between two surfaces. This option is available only in FEM mode. For information on allowed surfaces, see Guidelines for Surface-Surface Connections and Interfaces (FEM mode). The points you use for any reference type requiring points can be any of the following: • • • single point or vertex point feature (includes one or more single points) pattern of point features The software treats the beams you create from point features or patterns of points as single entities. You cannot specify different properties for different beams created from the same point feature or pattern of point features. Beam Type In FEM mode, only, select the type of beam you want to define on the Beam Definition dialog box. You can define two types of beams: • • Beam — A beam has an assigned material, Y direction, beam section(s), beam orientation(s), and beam releases. You can specify different beam section shapes and sizes for the beam ends in FEM mode. Truss — A truss is a special kind of beam that has properties that define its material and cross-sectional area. You cannot define the orientation or release properties for a truss. A truss has no rotational DOF, and experiences no bending or torsional effects under load. Y Direction for Beams You specify the orientation of the XY plane of a beam by defining its Y direction with respect to the WCS on the Beam Definition dialog box. The X axis is along the length of the beam. For the Y direction, you can enter vector coordinates, or select a geometric entity to specify a direction. Mechanica then defines the Z axis of the beam action coordinate system as perpendicular to the XY plane. The Y and Z axes you define in this way orient the BACS. You can define the Y direction of a beam by selecting any of the following entities on your model: • Point — Define the beam's XY plane by the X axis of the beam and its Y vector, which extends from the start point of the beam to the selected datum point or vertex. 228 Structural and Thermal Simulation • • • • • Edge — In FEM mode only, define the beam's XY plane with the beam's X vector and the projection from the start point of the beam toward the selected edge. Curve — In FEM mode only, define the beam's XY plane with the beam's X vector and the projection from the start point of the beam to the selected datum curve. Axis — Define the beam's XY plane with the beam's X vector and the projection from the beam start point to the selected axis. Surface — In FEM mode only, define the beam's XY plane with the beam X vector and the projection of the start point of the beam to the selected surface. Vector in WCS — Define the beam's Y direction by entering the X, Y, and Z components of a vector. The default is 0, 1, 0, which specifies a Y direction parallel to the positive Y axis of the WCS. To Create a Beam 1. Select Insert>Beam or click . The Beam Definition dialog box appears. 2. Type a name for the beam, or use the default name. 3. Select a reference type for the beam location from the drop-down list. 4. If you did not select reference(s) before opening the dialog box, click to select them now. 5. Select the material for the beam from the drop-down list, or click More to create a new material or select a material from the library. 6. Select one of the following options from the drop-down list to define the Y direction: o Point o Axis o Vector in WCS 7. On the Start tab, select a beam section from the drop-down list or click the More button to create a new beam section. 8. Select a beam orientation from the drop-down list or click the More button to define a new beam orientation. 9. Select a beam release from the drop-down list or click the More button to create a new beam release. 10. On the End tab, select a beam release from the drop-down list or click the More button to create a new beam release. 11. Select OK to accept your definition, or Cancel to close the dialog box without creating the beam. To Create a Beam (FEM mode) 1. Select Insert>Beam or click . The Beam Definition dialog box appears. 229 Structural and Thermal Simulation - Help Topic Collection 2. Type a name for the beam, or use the default name. 3. Select a reference type for the beam location from the drop-down list. and 4. If you did not select geometry before opening the dialog box, click use the regular selection methods to select the geometric entities now. 5. Select the material for the beam. 6. Select the beam type. 7. Select one of the following options from the drop-down list to define the Y direction: o Point o Edge o Curve o Axis o Surface o Vector in WCS 8. On the Start tab, select a beam section from the drop-down list or click the More button to create a new beam section. 9. Select a beam orientation from the drop-down list or click the More button to define a new beam orientation. 10. Select a beam release from the drop-down list or click the More button to create a new beam release. 11. Repeat steps 8 through 10 on the End tab. 12. On the Extra tab, enter values for the shear relief coefficient for planes XY and XZ. 13. Select the check box if you want to include stress recovery. Masses About Masses A mass is an idealization that you can use to represent a concentrated mass without a specified shape. The mass of an object determines how that object resists translation and rotation. If you are interested in the way your model behaves with mass at a given location, but not in the geometry or other features of that mass, use mass idealization. For example, you can represent the mass of an engine on a car frame without specifying the engine geometry. To create a mass, select Insert>Mass and use the Mass Definition dialog box to create a mass and specify its properties. After you create a mass, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a mass, Mechanica asks you for confirmation first. For some types of masses, you may need to assign mass properties. You can create mass properties by selecting Properties>Mass Properties or from the Mass Definition dialog box as you are creating the spring. Your options for creating masses differ in native mode and FEM mode: • Native mode — You can add a mass to a vertex or a point. You can also add a mass to multiple single points, point features, and point patterns in most cases. However, if you are working in the assembly mode and want to use a 230 Structural and Thermal Simulation • component's mass for your mass idealization definition, you can only select a single point. FEM mode — In addition to adding a mass to a point, you can also add a mass that is distributed over geometric entities such as curves, edges, or surfaces. Use distributed masses, for example, to represent the mass contribution from paint, or from a large number of small objects. You can select several curves, edges, or surfaces. To learn how FEM mode's FEA solvers treat masses, see ANSYS and MSC/NASTRAN. If you want to override the precedence rules for masses in FEM mode, you can use the config.pro option sim_additive_mass. When you set this option to "Yes," you can create several masses that reference the same geometric entity and the software will include all of the masses. Also, with this option turned on you can override the precedence rules that normally govern mass creation. For example, if sim_additive_mass is set to "No" and you try to create two masses, mass a on a single point and mass b on a feature of points containing the single point, mass a on the single point overrides mass b on that same single point, leaving mass b on the other points in the feature unchanged. But if sim_additive_mass is set to "Yes," you can create both masses, and include both masses in your analysis. Use this option, for example, to simulate two layers of paint as distributed masses on a surface. If you need to create additional datum points or curves before you begin the process of adding masses to your model, you can use the Insert>Model Datum>Point or Insert>Model Datum>Curve command. Keep in mind that if you want to model a mass on a point that is separate from your model, you must connect it to the model, for example, with rigid links or beams. Otherwise, the mass will not be included in any analyses. You can control the visibility of masses on your model by using the View>Simulation Display command, or by placing them on layers. Native Mode Mass Definition Dialog Box When you select Insert>Mass, the Mass Definition dialog box appears. Use the items on this dialog box to create a mass in native mode. • • Name — Enter a descriptive name, or accept the default name. References — If you already selected valid geometric references for your mass before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. Otherwise, use the selector arrow to select a datum point or a vertex. For Simple or Advanced masses you can also select multiple single points, multiple points, vertices or features, or a single point pattern for your mass. Use the SIM SELECT menu to specify which type of entity you want to use. Tip: Read Precedence Rules for information on how the software applies masses to these references. 231 Structural and Thermal Simulation - Help Topic Collection • Type — The Properties area of the dialog box changes depending upon the type you select from the drop-down list. o Simple — Enter a real-number value for the mass, or click p to create or select a Pro/ENGINEER parameter. o Advanced — Select a coordinate system or accept the default WCS. You must also specify a mass property for advanced masses. The mass properties are relative to the selected coordinate system. You can use any mass property previously defined for your model, or you can click the More button to define new mass properties. Tip: You cannot locate an advanced mass on the Z axis of a cylindrical coordinate system, or on the = 0 axis of a spherical coordinate system. o Component (for assembly mode only) — Select a part or subassembly on your model. The software uses the mass property definition of the component for your mass idealization, as described in Masses Based on Components. Setting a Coordinate System for an Advanced Mass On the Mass Definition dialog box, click the selector arrow under Coordinate System. From the SIM CSYS SEL menu, select one of the following options: • • • Current — Select the existing current coordinate system set for the model. WCS — Set the WCS (World Coordinate System). This is the default selection. Select — Use the normal selection methods to set the coordinate system. To Add a Mass to a Point 1. Select Insert>Mass or click . The Mass Definition dialog box appears. 2. Enter a descriptive name for your mass, or use the default name provided. 3. Accept Point(s) as the reference. 4. Click , select one of the following from the SIM SELECT menu to specify where the mass will be located, and select the appropriate entity on your model. o Single (default) o Feature o Pattern 5. Select one of the following from the drop-down list under Type. o Simple o Advanced o Component 232 Structural and Thermal Simulation 6. If you select Simple, enter a real-number value for the mass or click p to open the Select Pro/ENGINEER Parameter dialog box. 7. If you select Advanced, specify mass properties and select a coordinate system, or accept the WCS as the default. and use the 8. In assembly mode only, if you select Component, click normal selection methods to select a part or subassembly to supply the mass value. 9. Select OK to accept your definition, or Cancel to close the dialog box without creating the mass. FEM Mode Mass Definition Dialog Box (FEM mode) When you select Insert>Mass, the Mass Definition dialog box appears. Use the following items on this dialog box to create a mass in FEM mode. • • Name — Enter a descriptive name, or accept the default name. References — If you already selected valid geometric references for your mass before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. Otherwise, select one of these items from the drop-down list, and use the selector arrow to select a reference on your model. o Point(s) — Use the selector arrow to select a point or vertex on your model. If you want to create a simple or advanced mass, you can also select multiple single points, point features and point patterns. o Edge(s) or Curve(s) — Use the selector arrow to select an edge or datum curve. o Surface(s) — Use the selector arrow to select a surface. Note: If the config.pro option sim_additive_mass is set to "Yes," you can create multiple masses on the same geometric entity, or on geometric entities, which would share the same node after meshing, and thus would invoke the precedence rules if the option were turned off. If you create a mass using a geometric reference on which you previously created a mass, the software opens a dialog box stating that another entity uses the same references. When you confirm, the software creates the second mass. • Type — Select from these mass types: o Simple — Create a simple mass on a point, pattern of points, or feature of points, along a curve or edge, or across a surface. o Advanced — Create an advanced mass with mass properties relative to a coordinate system. You can only assign advanced masses to points, patterns of point, or features of points. o Component — Create a mass based on an assembly component's mass, moments of inertia, and center of gravity as described in Masses Based on Components (FEM mode). You can only assign component 233 Structural and Thermal Simulation - Help Topic Collection masses to points, patterns of point, or features of points in an assembly. The Properties area of the dialog box changes depending upon the type you select from the drop-down list. To Add a Mass (FEM mode) 1. Select Insert>Mass or click . The Mass Definition dialog box appears. 2. Enter a descriptive name for your mass, or accept the default name. 3. If you did not select valid geometry as references before you entered the dialog box, select one of these options from the References drop-down list: o Point(s) o Curves(s)/Edges(s) o Surface(s) 4. If you select Point(s), see the procedure To Add a Mass to a Point. 5. If you select Curves(s)/Edges(s), or Surfaces(s), click and use the regular selection methods to select one or more curves(s), edges(s), or surfaces(s). 6. Select Simple or Component (for assemblies) from the drop-down list under Type. 7. If you select Simple, select Total, Per Unit Length (curves and edges), or Per Unit Area (surfaces) from the drop-down list under Properties. 8. Enter a real-number value for the mass, or click p and select or create a Pro/ENGINEER parameter. 9. In assembly mode only, if you select Component, click and use the normal selection methods to select a part or subassembly to supply the mass value. 10. Select OK to accept your definition, or Cancel to close the dialog box without creating the mass. Springs About Springs A spring connects two points or a point to ground in your model. You can use a vertex as a point by selecting it. Any spring you add provides the stiffness that, you specify at the location on your model where you place it. The stiffness can be translational (force per unit length) or torsional (torque). The force generated by the spring is proportional to the amount of displacement that occurs—for example, if you double the displacement, you double the force. When you model a spring, you must specify the spring's geometrical references, as well as its stiffness and orientation. Use the Insert>Spring command to create springs. For some types of springs, you may need to assign spring properties. You 234 Structural and Thermal Simulation can create spring properties by selecting Properties>Spring Properties or from the Spring Definition dialog box as you are creating advanced or to-ground-type springs. When you select the Insert>Spring command, Mechanica displays the Spring Definition dialog box, which includes the following items: • • Name — The name of the spring. You can enter a descriptive name or accept the default. References — Use this area to select the geometric references for your spring. If you already selected valid geometric references before entering the dialog box, your selections appear next to the selector arrow when the dialog box opens. Otherwise, use the selector arrow and the regular selection methods to choose the desired geometry. Type — When you select one of these types of spring from the drop-down list, the dialog box changes. o Simple — You define a simple spring by specifying the extensional and torsional stiffness with a real-number value or a Pro/ENGINEER parameter. o Advanced — You define an advanced spring by specifying the magnitude and direction of components for the spring extensional and torsional stiffness. o To Ground — You define this type of spring by specifying the orientation of the components for the extensional and torsional stiffness in terms of a selected coordinate system. • When you click OK to accept your definition, the software adds a spring icon to your model. You can control the visibility of springs on your model by using the View>Simulation Display command, or by placing them on layers. After you create a spring, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a spring, Mechanica asks you for confirmation first. To learn how FEM mode's FEA solvers treat springs, see ANSYS and MSC/NASTRAN. Guidelines for Spring Creation Before you begin the process of creating a spring, keep in mind the following points: • A spring is attached to at least one point in your model. If you need to create additional points before you add a spring, you can use datum point creation functionality to do so. For more information on creating points this way, see Datum Point. You can also click a vertex to use it as a point. A spring can act as a constraint in your model, and in some instances may be all the constraint that you need. However, be aware that while a spring can remove degrees of freedom in one direction, it can allow freedom of movement in other directions. If you plan to place springs on a shell model, see Model Entities and Idealizations to learn about how Mechanica processes idealizations applied to a point. 235 • • Structural and Thermal Simulation - Help Topic Collection Simple Springs Using Simple Springs Use a simple spring to connect two points, two vertices, a point to a point on an edge or a surface, a point to a pattern of points, or a point to a single point feature. Note: You cannot define a zero-length simple spring. Use the following areas on the simple version of the Spring Definition dialog box to define a simple spring: • • Extensional stiffness — The stiffness that resists the stretching or compression of the spring. You can enter a real-number value or an expression that contains parameter names. Torsional stiffness — The stiffness that resists the twisting of the spring. You can enter a real-number value or an expression that contains parameter names. These two stiffness fields are parameter-capable edit fields. They can accept Pro/ENGINEER parameters as stiffness values, which you can select from a displayed list. Note: If you are using a simple spring to join two parts, make sure that the parts are attached to each other in another manner, or that they are constrained. Simple springs do not require that you specify an orientation. To Create a Simple Spring 1. Select Insert>Spring or click . The Spring Definition dialog box appears. 2. Enter a name for the spring, or use the default name provided. 3. Select Simple as the spring type. 4. If you did not select geometric references before opening the dialog box, click under References and use the normal methods to select references on your model to specify the locations of the spring's end points. 5. Define the spring stiffness properties by entering real-number values for the following properties, or click p to use a Pro/ENGINEER parameter: o Extensional Stiffness o Torsional Stiffness 6. Click OK to save the new spring. 236 Structural and Thermal Simulation To Ground Springs Using To Ground Springs Use a To Ground spring to connect to ground a point, multiple points, a vertex, a point feature, or a single pattern of points. Note: In FEM mode, To Ground springs are not supported for ANSYS. Use the following areas on the To Ground version of the Spring Definition dialog box to define an advanced spring: • • Properties — Use any stiffness properties previously defined for your model, or define new stiffness properties. Y Direction — Define the orientation of the spring by selecting a coordinate system. This defines the directions to which the spring stiffnesses refer. You can select any coordinate system for this purpose. The default is the WCS. To Create a To Ground Spring 1. Select Insert>Spring or click . The Spring Definition dialog box appears. 2. Enter a name for the spring, or use the default name provided. 3. Select To Ground as the spring type. 4. If you did not select points as geometric references before opening the dialog box, click and use the normal methods to select references on your model to specify a location for the spring. 5. Define stiffness properties for the spring. You can select a previously-defined stiffness property from the drop-down list, or you can click the More button to define new stiffness properties. 6. Click in the Y Direction area to select a coordinate system to specify the orientation of your spring. The default is the WCS. 7. Click OK to save the new spring. Advanced Springs Using Advanced Springs You can use an advanced spring to model a connection between two objects characterized by stiffness, and in FEM mode, by damping as well. The characteristics of an advanced spring, such as its stiffness components, are evaluated regardless of the location of its ends, but only with regard to the X, Y, Z directions of its coordinate system. 237 Structural and Thermal Simulation - Help Topic Collection Use these areas on the advanced version of the Spring Definition dialog box to define an advanced spring: • • • Properties — Use any stiffness properties previously defined for your model, or define new spring properties. Y Direction — Select a method to define the orientation of the spring properties. Additional Rotation — Enter a real-number value for the number of degrees to rotate the spring's Y axis. In FEM mode, advanced springs can have a zero length—that is, they can have coincident ends. An example might be a spring between a point on a surface and the surface itself. To learn how the FEA solvers treat advanced springs, see ANSYS and MSC/NASTRAN. Advanced Spring Restrictions (FEM mode) In FEM mode, for model output to ANSYS, the following restrictions apply when you specify a coordinate system for an advanced spring: • • Two advanced springs with a common end must use the same orientation. A constraint defined at one of the ends of the advanced spring must use the advanced spring's coordinate system. Y Direction for Advanced Springs When you create an advanced spring, you must specify a coordinate system for the stiffness properties to reference. The spring's X axis is along the spring length. The software defines the Y direction as lying in the XY plane, and perpendicular to the spring X axis, and uses the right-hand convention to define the Z direction. Use the following options on the advanced version of the Spring Definition dialog box to define the XY plane for the stiffness properties of an advanced spring: • Point — Use the selector arrow to select a reference point that lies in the spring's XY plane. • Axis — Use the selector arrow to select a reference axis that is parallel to the spring's XY plane. 238 Structural and Thermal Simulation • Vector in WCS — Specify the X, Y, and Z components, relative to the WCS, of a direction vector that lies in the spring's XY plane. This option is the default selection. • Coordinate System — Specify the coordinate system to which the spring properties refer. You can select any coordinate system for this purpose. The default is the WCS. Note: You can define zero-length springs in FEM mode. In this case, to define the orientation, you should select a coordinate system. To Create an Advanced Spring 1. Select Insert>Spring or click . The Spring Definition dialog box appears. 2. Enter a name for the spring, or use the default name provided. 3. Select Advanced as the spring type. 4. If you did not select geometric references before opening the dialog box, click and use the normal methods to select references on your model to specify a location for the spring. Define stiffness properties for the spring. You can select a previously-defined stiffness property from the drop-down list, or you can click the More button to define new stiffness properties. Define the Y direction of your spring. Enter an additional rotation if you want a value other than zero. If you do not enter a value, the software assumes a value of zero. Click OK to save the new spring. 5. 6. 7. 8. Precedence Rules Precedence rules for your idealizations and connections determine which modeling entity takes precedence when you apply two modeling entities of the same type on or between the same reference entities. There are two types of precedence rules, modeling precedence rules and geometric precedence rules. 239 Structural and Thermal Simulation - Help Topic Collection Modeling Precedence Rules These rules apply when you work with assemblies, and are determined by the assembly hierarchy: • • When you apply a modeling entity from a top-level assembly, this modeling entity takes precedence over a modeling entity applied from a subassembly or a part. When you apply a modeling entity from a subassembly, this modeling entity takes precedence over a modeling entity applied from a part. Geometric Precedence Rules Keep these rules in mind when working with the modeling entities that require points, curves, or surfaces as their reference entities. With some of these modeling entities, you can use multiple geometric entities as reference entities. For example, you can select a feature or a pattern of points and create a beam, spring, or rigid link that runs along a sequence of points. You can also apply a beam on multiple curves, or place a shell on a collection of surfaces. If you later create a new modeling entity of the same type, placing it on or between the same reference entities, it overrides the existing one when the following conditions are met: • • You select a higher precedence geometric entity as a reference entity for your new modeling entity. The higher precedence geometric entity belongs to a lower precedence geometric entity already referenced by your existing modeling entity. For example, if you select a single point as a reference entity for your new beam, the new beam overrides an existing one that references a feature of points that include this single point. The following table illustrates how the precedence rules work for modeling entities that can reference points, curves, or surfaces. Modeling Entity or Mesh Control Reference Entity Geometric Precedence Rule A single point takes precedence over a feature of points or a pattern of points. A feature of points takes precedence over a pattern of points. Points take precedence over curves, edges, and surfaces. • • • • • • beam spring mass gap rigid link weighted link points 240 Structural and Thermal Simulation • • beam mass (in FEM mode) An individual curve takes precedence over a composite curve. curves or edges Curves and edges take precedence over surfaces. • • • shell beam (surfacesurface, in FEM mode) mass (in FEM mode) surfaces A single surface takes precedence over a whole quilt. Results When Using Automatic Midsurface Connections When you model an assembly using midsurface compression and the automatic midsurface connections established by this type of modeling connect overlapping surfaces subject to displacement, Mechanica can give results that do not reflect the actual displacement. This figure shows an assembly with two mated parts before you apply any displacement stress. This figure shows the actual results when the two parts are modeled as solids resulting in no slippage along the common surface. This figure shows what happens when you use midsurface compression with automatic midsurface connections. Mechanica displaces the assembly about four times further than it does for solid parts. 241 Structural and Thermal Simulation - Help Topic Collection If the difference between the actual displacement and the displacement reported by Mechanica is beyond an acceptable tolerance, consider one of these alternatives: • • In situations where the difference is unacceptable for the entire model, we suggest that you model your assembly as a solid. In situations where the difference is only unacceptable for certain mated components, you can create welds, fasteners, or rigid connections to model the behavior in these areas. Alternatively, you can use beams to stiffen the model and, thus, correct the behavior. Spring References You can define the location of a spring on your model by selecting one of the following reference types from the References area on the Spring Definition dialog box: • • • Point–Point — Create a spring between two points or two vertices. Point–Surface — Create a spring between a point and a surface, or a vertex and a surface. Point–Edge — Create a spring between a point and an edge, or a vertex and an edge. Note: For the location of the spring-end positioned on the surface/edge, the software selects the spot that is closest to the first point of the spring. If you need to position the spring at a particular place on the surface/edge, use the Point–Point option and create a datum point along the surface/edge. • Point–Point Pairs — Create multiple point-to-point springs with the same characteristics. The points you use for any reference type requiring points can be any of the following: • • • single point or vertex point feature (includes one or more single points) pattern of point features The software treats the springs you create from point features or patterns of points as single entities. You cannot specify different properties for different springs created from the same point feature or pattern of point features. 242 Structural and Thermal Simulation Extra Tab on Beam Definition Dialog Box You can use the following items on the Extra tab of the Beam Definition dialog box to include shear and stress information in your beam results. This tab is only active in FEM mode. • Shear Relief — Enter values in this area for the components of the shear relief coefficient in the XY plane and XZ plane. You may want to specify a shear relief coefficient if your beam is tapered and includes thick flanges. In a tapered flanged beam, the flanges support a portion of the transverse shear load, and the shear relief coefficients take this support into consideration. For a beam for which the thicknesses at ends A and B are given by hA and hB, respectively, the shear relief coefficient is given by: S = 2(hA - hB)/(hA + hB) • Include Stress Recovery — Check this box if you want Mechanica to include beam stress recovery points in analyses. Auto Detect Paired Surfaces If you used feature creation methods that implicitly paired the surfaces in your model, you can use the Insert>Midsurface>Auto Detect command to detect and pair these surfaces automatically. Feature creation methods that implicitly pair surfaces in your model include: • • • • • shells ribs ears thin protrusions sheet metal When you select Auto Detect, Mechanica highlights the pairs that it was able to create. One surface in each pair is red and the other yellow. If you determine that Auto Detect did not pair all the applicable pairs in the model, use New to complete the pairing process manually. See Example: Unpaired Surface on L-Bracket for an example of geometry with unpaired surfaces. Guidelines for Assigning Mass Properties Before you create a mass idealization that is based on a component (part or subassembly) in Mechanica, you must use Pro/ENGINEER to calculate mass properties for the component, and save the component before leaving Pro/ENGINEER. 243 Structural and Thermal Simulation - Help Topic Collection Here are a few methods you can use to get the necessary mass information: Part • • Open the part in Pro/ENGINEER and use the Edit>Setup>Mass Props command. Enter a density value on the Setup Mass Properties dialog box. Be sure you save the part before leaving Pro/ENGINEER. Open the part in Pro/ENGINEER and use the Edit>Setup>Material>Define command to specify material properties. Then use the Edit>Setup>Mass Props command to obtain the mass from the material properties. Be sure you save the part before leaving Pro/ENGINEER. Use material properties from Mechanica with the Pro/ENGINEER Edit>Setup>Material>Assign command. Then use the Edit>Setup>Mass Props command to obtain the mass from the material properties. Be sure you save the part before leaving Pro/ENGINEER. • Subassembly • To use a subassembly as the component for your mass idealization, you must assign mass properties to all of the parts in the subassembly using one of the methods above. Be sure to use the Edit>Setup>Mass Props command and save the subassembly before you leave Pro/ENGINEER. If you have not assigned any mass properties for your subassembly or its components in either Pro/ENGINEER or Mechanica, you can use the Pro/ENGINEER Edit>Setup>Mass Props command to calculate mass properties for the entire subassembly. Select Geometry and Parameters under Source, and enter a density value. When you click OK, Pro/ENGINEER calculates mass properties for all the components in your subassembly based on that density. • Parameter-Capable Edit Fields When an edit field is parameter-capable, you can enter expressions that contain the names of Pro/ENGINEER parameters. During design studies, Mechanica evaluates these expressions and uses the resulting value in the computation. If an edit field is parameter-capable, Mechanica displays a P button to the left of the edit field. When you click the P button, the software displays the Select Pro/ENGINEER Parameter dialog box. If no Pro/ENGINEER parameters are defined, the data form appears but does not list any parameters. If Pro/ENGINEER parameters are defined, you can select one from the displayed list. Mechanica then displays the parameter you select in the edit field. 244 Structural and Thermal Simulation Fix and Flip Normals If your shell is not part of a volume or part of a shell pair in a midsurface compressed model, these options appear on the SIM SELECT menu after you select a surface for the Insert>Shell or Insert>Pressure Load command: • Fix Normals — Use this option to adjust all surfaces so that the normal directions in each element are consistent across the model. Mechanica changes the normal direction of some surfaces to make the normals as consistent as possible. For certain models, it is not possible to generate a completely consistent set of directions. Review the normals and use Flip to fine-tune the global fix. • Flip Normals — Use this option to change the direction of the normal in selected surfaces. Select the surfaces. Mechanica flips the direction of the arrow for each surface you selected. Example: Geometric Precedence Rules Suppose you apply your first beam between a single point and a feature of points. Although the software creates multiple beams, it treats them as a single entity. For your second beam, you select two single points, one of them belonging to the feature of points referenced for the first beam. The second beam overrides the one that already existed between the same single points. The remainder of the first beam referencing the point feature is not changed. 245 Structural and Thermal Simulation - Help Topic Collection Example: Invalidating a Modeling Entity You cannot use a force load with a force per unit area distribution on a geometric entity that you midsurface compress to another type of geometric entity. For example, if you decide to model the following rectangular plate as a shell, Mechanica would display a warning indicating that you need to redefine the problem load. If you applied the load with a force per unit of length distribution to the top or bottom curve for the surface shown above, Mechanica would keep the load. If you loaded both the top and bottom curve, Mechanica would calculate the compressed load based on the value of both loads. 246 Structural and Thermal Simulation Example: Multiconstant-Thickness Pairs One of the simplest illustrations of a part you can model with a multiconstantthickness pair is the following: In this case, you select all three top surfaces and pair them with the three corresponding bottom surfaces. When it processes the pair, Mechanica compresses the bottom surfaces and top surfaces into a single, continuous midsurface. The software divides the midsurface into segments that coincide with the layout of the top surfaces and associates the individual thicknesses with each of these segments. Note: Make sure the compressed midsurfaces all intersect so that there are no gaps or discontinuities. If they do not intersect, correct the model manually to eliminate the gaps. When it builds elements during an analysis run, Mechanica places half of the thickness on top of the midsurface and half on the bottom. If your model includes shell pairs of variable thickness, or one where you have modified the pair placement, the shape of the final model may be different from that of the uncompressed model, as in the following example: 247 Structural and Thermal Simulation - Help Topic Collection Point–Point Pairs When you select Point–Point Pairs from the Reference option menu on the Beam Definition or Spring Definition dialog boxes, you can create multiple beams or springs on individual pairs of points. These beams or springs will all share the same definition. In contrast, if you select Point–Point, Point–Surface, or Point–Edge from the Reference option menu, the definition applies to only one spring or beam at a time. To create multiple beams or springs, you select Point–Point Pairs from the Reference option menu, click the selector arrow under the Reference option menu, and then select the beginning and end points of each beam or spring you want to create. You must select an even number of points and you can select the same point twice. All the settings you make on the dialog box will apply to all the beams or springs you create before you click the OK button. You can use the Point–Point Pairs option to create multiple continuous or individual beams or springs, all having the same definition. For example: • You can create a continuous string of end-to-end beams or springs where the end of one beam or spring is at the same point as the beginning of the next. As shown on the left in the example below, you can create four continuous end-to-end beams or springs that have the same beginning and end point by clicking points 1, 2, 2, 3, 3, 4, 4, and 1, in that order. You can create multiple individual beams or springs by clicking the beginning and end points of each one. As shown on the right in the example below, you can create two individual beams or springs that do not touch each other by clicking points 1, 2, 3, and 4. • 248 Structural and Thermal Simulation Example: Collet Illustration 249 Structural and Thermal Simulation - Help Topic Collection Example: Unpaired Surface on L-Bracket The following L-bracket includes one unpaired surface. Shown with this example are two solutions: In this case, the L-bracket round does not have a surface that the software can pair it with. To remedy the situation, you should suppress the round, as in solution A, or create an opposing round, as in solution B. Omit Unopposed Surfaces If you omit unopposed surfaces from a pair, Mechanica compresses the model differently depending on the following factors: • • whether the surface you omitted is on the red side of the pair or the yellow side of the pair the state of the UseUnopposed toggle on the COMPRES MDL menu For example, if you designed a collet and wanted to constrain a small section of the outside surface, you might add a region to the model. If you then omitted the region from your pairing scheme, Mechanica would compress and subsequently analyze the model differently depending on which surface had the red highlighting. To see how the compression results change when the unopposed surface is on the red side or the yellow side of the pair, see the collet cross section illustration. After you pair your model, you can inspect the pairing scheme by shading your model. To shade your model, select View>Shade and highlight Shell Pairs in the 250 Structural and Thermal Simulation Model Tree. Reviewing the shaded model can disclose areas that are unpaired but may not be noticeable in the wireframe view of the model. Example: T-Bracket In the following approach, Mechanica compresses shell pair a to form the horizontal plane of the T-bracket and shell pair b to form the vertical plane. 7 Note: If your model includes a meeting of more than two surface pairs, make sure the compressed midsurfaces all intersect at a common point or axis. If they do not, correct the model manually to ensure a proper intersection. The original model in the above example was created as a solid model. However, if you created this model using Pro/SHEETMETAL, the software may not merge the common surface of the two perpendicular plates, resulting in a gap between the two midsurfaces. In this case, you may need to correct the geometry to ensure that Mechanica solves the model correctly. Example: Part with Unopposed Surfaces The part in the figure is an example of geometry that can lead to unopposed surfaces in a shell model. The top of the part, surface a, is selected first for the shell pair. There are three shorter, non-continuous surfaces opposite and parallel to surface a. Suppose you select only surface b on the bottom portion of the horizontal bar to complete the shell pair. This means that surface a does not have an opposing surface for its entire length. To see how the presence or absence of an unopposed surface affects the midsurface compression, select the Insert>Midsurface>Compress>Shells only command. The COMPRES MDL menu appears with the UseUnopposed check box selected. If you select the Show Pairs command with the UseUnopposed check box selected, Mechanica uses the entire length of surface a for the compressed midsurface, as shown on the right. If you select Show Pairs with the UseUnopposed check box 251 Structural and Thermal Simulation - Help Topic Collection cleared, Mechanica uses the length of surface b, and displays the shorter midsurface on the left. Example: Assembly Model with Gap This figure shows that after midsurface compression, the resulting model develops a gap between the collet and the bracket. By nature, the collet midsurface is smaller than the outer surface and no longer reaches the bracket despite the assembly constraints. Because it applies a shell thickness that would interfere with the bracket were the bracket to move, Mechanica does not adjust the position of the bracket midsurface to meet the collet midsurface. 252 Structural and Thermal Simulation Masses Based on Components (FEM mode) Keep the following points in mind when using components for mass definitions in assembly mode: • Before you create a mass idealization that is based on a component, you must calculate mass properties for the component or the entire assembly using the Pro/ENGINEER command Edit>Setup>Mass Props. This command opens the Setup Mass Properties dialog box. Enter a density for the assembly or components and click OK to assign or update the mass property values. If you want to review the mass properties values, click Generate Report. Be sure to save the component so that the mass will be available for Mechanica. Note: For tips on alternative methods to assign mass properties before you create a mass idealization, see Guidelines for Assigning Mass Properties. For more information on the Mass Props command, search the Fundamentals functional area of the PTC Help system. • • • The component that you use to define your mass cannot contain volumes that will be meshed as solids during a FEM analysis. You can select a curve or surface on a master representation or a simplified representation. For information on simplified representations, search the Fundamentals functional area in the PTC Help system. The component that you use to define your mass can be specified as excluded or substituted in the simplified representation. In this case, select the excluded or substituted component from the Model Tree when you define your mass. After you define a mass by component, you can confirm the values of the mass, moments of inertia, and center of gravity for the component by using object action or by right-clicking the mass item under Idealizations on the Model Tree and selecting the Info command. The moments of inertia and center of gravity are reported in terms of the component's WCS. The location of the selected point affects the analysis of your FEM mesh data. If the point you select for your mass idealization coincides with the center of gravity of the component, you can output mesh data to the ANSYS or MSC/NASTRAN solvers. If the point you select for your mass idealization does not coincide with the center of gravity of the component, you can only output to the NASTRAN solver. You cannot use the other FEM solvers with this type of mass idealization. After you run the NASTRAN solver, you can view the center of gravity offset on the NASTRAN output. • • • 253 Structural and Thermal Simulation - Help Topic Collection Properties According to Mass Type (FEM mode) The information you need to enter in the Properties area of the Mass Definition dialog box changes depending on whether you select Simple, Advanced, or Component from the Type option list. Here is an overview: • Simple — For simple masses on points, enter a real-number value or click p to create or select a Pro/ENGINEER parameter. For simple masses on edges, curves, or surfaces, select one of these properties to define a simple mass: o Total — Enter a real-number value for the mass, or click p to create or select a Pro/ENGINEER parameter. The distribution of the mass along the surface or curve depends upon the mesh nodes. Each node contributes to its neighboring nodes. The mass distribution is weighted by the contribution from adjacent nodes. For example, a node on a curve with two neighboring nodes will have twice the mass distribution as a node with only one neighbor. o Per Unit Length or Per Unit Area — Enter a real-number value or click p to create or select a Pro/ENGINEER parameter. For a curve, the total mass is the product of the entered value times the length. For a surface, the total mass is the product of the entered value times the area. The mass distribution is weighted by the contribution from adjacent nodes. Advanced — For advanced masses, select a coordinate system or accept the default WCS. You must also specify a mass property for advanced masses. The mass properties are relative to the selected coordinate system. You can use any mass property previously defined for your model, or you can click the More button to define new mass properties. Tip: You cannot locate an advanced mass on the Z axis of a cylindrical coordinate system, or on the = 0 axis of a spherical coordinate system. • Component — For component masses, select one of the parts or subassemblies on your assembly. The software uses the component's mass, moments of inertia, and center of gravity for the mass definition. • Surfaces and Curves Used in Shell Definition You can use the following surfaces and curves to define a shell: Mode Native mode Surfaces/Curves You Can Select You can select surfaces or quilts as references. Surface references are valid only for 3D model types and 2D plane stress model 254 Structural and Thermal Simulation Mode Surfaces/Curves You Can Select types. Curve references are valid only for 2D plane strain and 2D axisymmetric model types. FEM mode You can select quilts and quilt surfaces, or surfaces of shell pairs. When you choose a shell pair, Mechanica respects any shell properties, such as thickness or material, provided you assign the properties to the red surface of the pair. If you choose the yellow surface of the compressed pair, Mechanica ignores the shell properties and derives such properties from the geometry of the solid. Masses Based on Components Keep the following points in mind when using components for mass definitions in assembly mode: • Before you create a mass idealization that is based on a component, you must calculate mass properties for the component using the Pro/ENGINEER command Edit>Setup>Mass Props. This command opens the Setup Mass Properties dialog box. Enter a density and click OK to assign or update the mass property values. If you want to review the mass properties values, click Generate Report. Be sure to save the component so that the mass will be available for Mechanica. Note: For tips on alternative methods to assign mass properties before you create a mass idealization, see Guidelines for Assigning Mass Properties. For more information on the Mass Props command, search the Fundamentals functional area of the PTC Help system. • • You can select a point or vertex on a master representation or a simplified representation. For information on simplified representations, search the Fundamentals functional area in the Pro/ENGINEER Help Center. The component that you use to define your mass can be specified as excluded or substituted in the simplified representation. In this case, select the excluded or substituted component from the Model Tree when you define your mass. After you define a mass by component, you can confirm the values of the mass, moments of inertia, and center of gravity for the component by using object action or by right-clicking the mass item under Idealizations on the • 255 Structural and Thermal Simulation - Help Topic Collection Model Tree and selecting the Info command. The moments of inertia and center of gravity are reported in terms of the component's WCS. Properties About Properties You must assign properties to your model and to its idealizations to provide Mechanica with the information it needs to analyze your model. Mechanica provides the following property types: • • • • • • • • Materials Material Orientations Shell Properties Beam Sections Beam Orientations Beam Releases Spring Properties Mass Properties For most properties, you must perform two main activities—creating the property and assigning the property: • • Property Creation — You can create properties at any time through the Properties menu and the dialog boxes for each property type. You can also create properties associated with idealizations as you create the idealization. Property Assignment — You can assign most properties that are associated with idealizations while creating the idealization. For example, you can assign spring properties as you create a spring idealization. You can assign properties associated with geometry or with the model as a whole at any time prior to analysis. Material properties assigned to a part or surface fall into this category. To learn more about the properties required by idealizations, see Properties on Idealizations and Geometry. For information on factors you should consider when using properties, see Considerations for Using Properties Deleting Properties You can delete properties using the following commands: • Material Properties — Properties>Materials. The Materials dialog box appears. You select a material from the Materials in Model list and click the Delete button to eliminate it. In FEM mode, you can also unassign materials you have assigned to your model. Shell Properties — Properties>Shell Properties. The Shell Properties dialog box appears. You select a shell property from the Shell Properties in Model list and click the Delete button to eliminate it. • 256 Structural and Thermal Simulation • Beam Section Properties — Properties>Beam Sections. The Beam Sections dialog box appears. You select a beam section from the Beam Sections in Model list and click the Delete button to eliminate it. Background Information Properties on Idealizations and Geometry You typically assign properties to model geometry and, in some cases, idealizations. Assigning properties to idealizations can be indirect, as in the case of assigning a material to a part that you then compress as a midsurface shell. Or, it can take place as part of creating an idealization on a geometric entity—for example, when you create a beam section directly assigned to a curve. The properties you assign vary with the type of idealization you are using: Idealization beam Properties Needed Material Beam Section Beam Orientation Beam Releases mass Mass Value Moments of Inertia shell Material Thickness solid Material Considerations for Using Properties Some considerations for using properties include the following: • Assigning Properties to Geometric Entities — You assign properties to geometric entities, not individual elements. For example, you can assign shell properties to curve and surface geometric entities. During a run, the elements Mechanica creates inherit properties from the geometric entity on which the element lies. Using Orthotropic or Transversely Isotropic Material Properties — If you plan to use orthotropic or transversely isotropic material properties, you 257 • Structural and Thermal Simulation - Help Topic Collection need to assign material orientation properties to solids, 2D solids, and 2D plates. See About Material Orientation for more information. Beam Sections About Beam Sections Use the Properties>Beam Sections command to define the shape and size of the cross sections when you create beams. You can also define a beam section and save it in a library file, called mbmsct.lib, for future use. There are three categories of beam section types that you can use: • • • Sketched — Create your own cross section using the sketch thin or sketch solid beam type. Standard — Use Mechanica's standard cross sections, such as square, rectangle, I-beam, and so on. General — Use Mechanica's general type to design a cross section. The general beam section does not have a specific shape, but you must provide the area, as well as section properties, shear parameters, and stress grids. When you select the Properties>Beam Sections command, the Beam Sections dialog box appears. You can also access this dialog box by clicking the More button in the Section area of the Beam Definition dialog box. Use the items on this dialog box to create, edit, copy, or delete beam sections. You can create several types of beam sections from these three categories. Standard beam sections reflect a particular predefined beam shape. You use the sketcher to define the shapes for sketched beam sections. General types do not reflect a particular shape. When you create a beam, Mechanica represents each of the standard beam section types with a unique icon that represents their shape and size. Icons for sketched sections reproduce the sketch, and General section icons are not associated with any shape. Beam Section Library Library Lists for Beam Sections, Shell Properties, and Spring Properties You can save beam section definitions, shell properties, and spring stiffness properties in property-specific libraries. These libraries are a convenient way to use the same property definition for more than one model. There is no limit to the number of property definitions you can have in a model or in your library. You can use the library lists on the Beam Sections, Shell Properties, and Spring Properties dialog boxes to add property definitions to these libraries, or to move property definitions from a library to your model. For information on how Mechanica saves the libraries, see Managing Library Files. 258 Structural and Thermal Simulation • Adding to the libraries — After you create a property definition, use the left arrow button on the appropriate dialog box to move the definition from the Entity in Model list to the Entity in Library list. This places the current property definition in your library. Be aware that Mechanica creates and saves the property-specific library file as soon as you move the first property from the Entity in Model list to the Entity in Library list. If the property definition you are adding has the same name as a definition already in the library, Mechanica tells you that the name already exists and asks if you want to overwrite it. If you select No, Mechanica does not add the current definition to the library. You cannot, overwrite a property definition in the Entity in Model list with a property definition with the same name from the Entity in Library list. If you create a new property definition with the same name as a definition already in the library, the left arrow button becomes inactive. • Editing library definitions — To edit a property definition from the library, use the right arrow button to move the property definition from the Entity in Library list to the Entity in Model list and select Edit to open the dialog box that you used to create the property definition. When you are finished editing, use the left arrow button to move it back to the Entity in Library list. Managing Library Files Mechanica handles the libraries for beam sections differently from the libraries for shell and spring properties. • Beam sections — beam_sections directory The beam_sections directory contains one file for every beam section definition in your library. The files have the same name as the beam section definition, with the extension .bsf. In addition, for sketched sections, Mechanica saves a .sec file with the sketch information. To delete a property definition from the beam section library, delete the appropriate .bsf file. Note that if you have a beam section library file (mbmsct.lib) from an earlier release present in one of the directories where Mechanica searches for the libraries and you save a new beam section into that library, the software creates a beam_sections directory that includes a .bsf file for each of the previous beam section definitions. Mechanica retains the original beam section library file so you can archive it or use it with older Mechanica releases that support .lib files for beam sections. • • Shell properties — mshlprp.lib. Spring stiffness properties — mspstf.lib The default location for all library files is your home directory, but you can move it to a different directory. You can use the environment variable $HOMEDRIVE to set your home directory on Windows platforms. 259 Structural and Thermal Simulation - Help Topic Collection When you access the library, Mechanica looks for the library file in the following directories in this order: 1. the directory from which you started Mechanica 2. your home directory 3. the lib subdirectory of the Mechanica home directory You can move or copy the library files into any of the above directories. Note: For the beam section library, you can specify another location for the beam_sections directory with the config.pro option sim_beamsec_path. You must use a full path for this option. Beam Section Definition Dialog Box When you click New on the Beam Sections dialog box, this dialog box appears with the following items. Use the Beam Section Definition dialog box to choose a crosssection type and specify the properties for your beam sections. • • • Name — Enter a descriptive name or accept the default name. Description — Enter an optional description for your beam section. The description appears on the Beam Sections dialog box when you highlight a beam section in one of the lists. Section tab — Select one of these sections from the Type drop-down list. The dialog box changes depending upon the type of section you choose. You can create the following beam section types: o General o Square o Rectangle o Hollow Rect o Channel o I-Beam o L-Section o Diamond o Solid Circle o Hollow Circle o Solid Ellipse o Hollow Ellipse o Sketched Solid o Sketched Thin Review — Click this button to open the embedded browser with a summary of the parameters that Mechanica calculates for your section. Warp & Mass tab — In FEM mode only, use this tab to define additional beam values when you use the MSC/NASTRAN solver. • • 260 Structural and Thermal Simulation Sketched Thin and Sketched Solid As you create sketched beam cross sections, you will be working with the section sketcher. Following are some guidelines for working with the sketcher: • • For Sketched Thin and Sketched Solid beam types, use the sketcher to draw and dimension the cross section of your beam. When you sketch a beam section, Mechanica displays the sketcher coordinate system with Y as the vertical axis and X as the horizontal axis. After you leave the section sketcher, Mechanica translates this coordinate system to one with Y as the vertical axis and Z as the horizontal axis. When you complete the beam the software displays a beam section icon on the appropriate model geometry. This icon shows the beam section's shape coordinate system (BSCS) in Y and Z, and reproduces the sketch in the correct size. You can add sketched sections to Mechanica's section library. If you created your sketched section in a previous release, be sure that the units for the beam section are consistent with the current principal system of units. If you want your solid sketched section to have a shear center that is different from the beam centroid, you must specify values for Shear DY and Shear DZ on the Beam Section Definition dialog box. To view stress results for recovery points for your sketched beam section, you must create points on the sketched section. When you view results, Mechanica displays a graphic of your sketch showing the location of the points. Keep in mind that the maximum number of recovery points is nine in native mode and four in FEM mode. Once you have completed your sketched beam sections, you can define shape changes for these sections by creating design parameters for them. In this case, the design parameters control the sketch dimensions you defined for the beam section. Thus, you can dynamically modify your beam profile during sensitivity and optimization studies. You can create design parameters using any sketched solid or thin beam section. Note: You cannot create design parameters for predefined Mechanica beam sections. Only sketched sections allow design parameters. • For thin sections, you must define thickness using the Sketch>Feature Tools>Thickness command. • • • • Beam Stress Calculations When you review results for beams, you can look at the maximum, minimum, or maximum absolute stress for each beam. You can also look at stress at any of the locations on each beam at which Mechanica reports bending stresses. The standard beam section types have default locations for the points at which you can view stress. For the general section, you must enter coordinates in Y and Z for the stress recovery points in the Stress Grids area of the Beam Section Definition dialog box. For a sketched section, you must explicitly create datum points on the section sketch in the location where you want to view stress results. When you define your result window, the software displays a graphic with the available stress 261 Structural and Thermal Simulation - Help Topic Collection recovery point locations for standard and sketched sections. The graphic for general sections displays default locations that may not correspond to the location of the points you enter in the Stress Grids area of the Beam Section Definition dialog box. Mechanica assumes that the shear center of the beam element lies on the neutral bending axis, which is true in general only for symmetric cross sections. If the beam cross section you are modeling is not symmetric about one or both principal bending axes, the displacement or stress results reported by Mechanica may not be correct. There are a few differences in reviewing results for beam stress in FEM mode: • • • You can only view stress recovery points in FEM mode results if you run with the MSC/NASTRAN solver and view the .xdb results file. There is a maximum of four beam stress recovery points. To compare the location of the allowed stress recovery points in native mode and FEM mode, see the help topic for each section type. You can create beams in FEM mode that have different section types at the start and end. Mechanica interpolates the cross-sections internally. If you create a beam with different start and end section types, you cannot view results for the stress recovery points. Beam Section Icons When you have entered values and accepted them on the Beam Section Definition dialog box, Mechanica places wireframe icons of the beam section on the beam. The icon is a full-scale representation of the beam section you defined. The beam section icon allows you to verify the sizing of the beam section, beam orientation, and beam offsets. For example, if you specify non-zero values for the DY and DZ offset on the Beam Orientation Definition dialog box, the icon is offset from the beam axis the specified distance. The beam section icon lies in a plane orthogonal to the beam X axis, as shown in this illustration: Note that for general sections, the software does not display an icon. For sketched sections, the software uses a reproduction of the sketch for the icon. 262 Structural and Thermal Simulation For information on the icons used for each beam section type, see Beam Section Definition Dialog Box and select the description for the appropriate beam section type. Beam Section Property Calculations Depending on the type of beam cross section, Mechanica uses the following formulations for beam section property calculations: • Solid Sections — The shear center is not calculated for solid sections. It is assumed to be at the centroid of the section, coincident with the neutral axis. You can modify the location of the shear center. Torsional stiffness, the second polar moment of area J, is approximated as: J = 4 Iy Iz / (Iy + Iz) Note: This equation gives the exact value only for circular sections and can have an error as high as 20% for rectangular sections. For other shapes, the error can be even higher. Exercise caution when using the calculated value of J. You can find exact values of J for torsional stiffness in R.J. Roark and W.C. Young, Formulas for Stress and Strain, 6th edition, Table 20, pages 348–359. • Thin Wall Sections — The calculation for this section type assumes the thickness is small relative to the overall dimensions of the section. The thickness is assumed to be distributed equally about both sides of the section. It is recommended, therefore, that you use this section type only when this length-to-thickness ratio exceeds 20:1. The overall exterior dimension of the sketch is a suitable characteristic length for this purpose. The calculation of torsional stiffness depends on the type of section. The section types, and their torsional stiffness calculations, are as follows: o An open section: J = 1/3 Ut3 where U is the total length of the sketched section, and t is the thickness. o A section containing a single closed cell: J = 4 Am2 t / U where Am is the area enclosed by the loop that defines the section, t is the thickness, and U is the total length. For more complex sections, the software applies a numerical procedure. See R.J. Roark and W.C. Young, Formulas for Stress and Strain, 6th edition, for examples. 263 Structural and Thermal Simulation - Help Topic Collection Note: For beams likely to experience torsional loading or deformation, it is recommended that you use the standard, predefined Mechanica sections. To Create a Beam Section 1. Select Properties>Beam Sections. The Beam Sections dialog box appears. Note: You can also access this dialog box by clicking the More button in the Section area of the Beam Definition dialog box. 2. 3. 4. 5. 6. Click the New button. The Beam Section Definition dialog box appears. Enter a section name or use the default name. Optionally, enter a description. On the Section tab, select the type of beam you want to create. In FEM mode only, on the Warp & Mass tab, define beam section information. 7. Optionally, you can click the Review button to review the beam section properties. 8. Click OK to save the beam section and exit the dialog box. Beam Orientation About Beam Orientations Use the Properties>Beam Orientations command to define beam orientations. Beam orientation specifies the orientation of the BSCS relative to the BACS. When you select this command, the Beam Orientations dialog box appears. Use this dialog box to create, edit, select, or delete beam orientations. When you create beam orientation definitions Mechanica saves the definition with your model file. You can associate the beam orientation definitions with beams as you create the beam or later. The Beam Orientations dialog box displays a list of the beam orientations you defined previously. When you highlight an orientation name, any description you included with the definition appears. This dialog box includes the following buttons: • • • • New — Opens the Beam Orientation Definition dialog box to allow you to define a new orientation. Edit — Opens the Beam Orientation Definition dialog box to allow you to modify the selected orientation. Copy — Adds a copy of the orientation to the list. Mechanica names the copy BeamOrientx, where x is a number calculated as one plus the number of beam orientations in the list. To change the name, use Edit. Delete — Removes the selected orientation from the list. 264 Structural and Thermal Simulation For information on how the software defines beam orientation, see Beam Coordinate Systems. Beam Action Coordinate System Loads applied to beams act through the beam action coordinate system (BACS). Forces and moments transmit to beams at beam connections through the BACS. The origin of the BACS is on the curve that the software draws as a blue line when you create a beam. The X axis of the BACS is parallel to the axis of the beam. You control the direction of the Y and Z axes of the BACS by setting the Y direction on the Beam Definition dialog box. Beam Shape Coordinate System Mechanica defines the beam cross-section shape relative to the beam shape coordinate system (BSCS). The X axis for beams is along the length of the beam, with the positive X direction determined when you select the beam references. For standard beam section types, the software determines the Y and Z axes for the BSCS. Here are a few examples of BSCS for standard beam sections: If you create a sketched beam section, the orientation of the Y and Z axes for the BSCS is the same as the orientation of the Y and X axes in the sketcher. For a general cross section, the software determines the BCPCS based on your specifications, and the BSCS is essentially the same as the BCPCS for this crosssection type. When Mechanica draws the beam section outline as part of the beam icon in the model window, it also draws the BSCS, with a Y-shape at the tip of the Y axis and an arrow at the tip of the Z axis. You can position the origin of the BSCS relative to the BACS by entering values for DY and DZ on the Beam Orientation Definition dialog box. You can also rotate the BSCS around the beam X axis by entering a value for Orientation Angle on the same dialog box. As an alternative adjustment, you can click the Shear Center radio button to position the shear center of the beam section relative to the BACS. When you assign a beam orientation to your beam, Mechanica adjusts the beam icon in the model window to reflect the rotational and linear offsets. 265 Structural and Thermal Simulation - Help Topic Collection Beam Centroidal Principal Coordinate System The origin of the beam centroidal principal coordinate system (BCPCS) is at the centroid, or mass center, of the section. The Y and Z axes of this coordinate system are the principal axes that pass through the centroid of the section. The principal axes define the axes of maximum and minimum moments of inertia. The location and orientation of the BCPCS relative to the BSCS is a function of the shape of the beam's section only. For general sections and all standard sections except channel and L, the BSCS is coincident with the BCPCS. For sketched, channel, and L sections, Mechanica determines the BCPCS automatically. The BCPCS is sometimes referred to as the principal coordinate system. When you review properties for a beam section, Mechanica uses the BCPCS to report many of the values. Beam Orientation Definition Dialog Box Use the items on the Beam Orientation Definition dialog box to specify the orientation of the BSCS relative to the BACS. To see how the values you enter here affect the orientation of the BSCS relative to the BACS, it may be helpful to view the example of shifting the shape origin or shifting the shear center. You can access this dialog box by selecting Properties>Beam Orientations, or by clicking the New button on the Beam Orientations dialog box. The Beam Orientation Definition dialog box includes these items: • • • • Name — Enter a name or accept the default name, BeamOrientx, where x is a number that Mechanica increments by 1 with each succeeding definition. Description — Enter an optional description. After you complete the beam orientation definition, the description appears in the Beam Orientations dialog box when you highlight the orientation name. Orientation Angle — Specify the angle to rotate the BSCS about the BSCS X axis. Shape Origin, Shear Center — Select one of these as the attribute for Mechanica to offset. The software uses the values you enter for DX, DY, or DZ to offset the BSCS from the beam action coordinate system (BACS). o Shape Origin is the point of origin of the beam shape coordinate system (BSCS). o Shear Center is the point on a beam section about which the section rotates under deflection. For many of the standard beam sections, the shear center is coincident with the shape origin. Channel sections and L-sections are exceptions. For channel sections, for example, the shear center is below the shape origin. You can view the offset of the shear center from the shape origin when you define or edit your beam section by reviewing beam section properties. 266 Structural and Thermal Simulation • • DX (FEM mode only) — Offset of the BSCS X axis from the BACS X axis. The offset occurs along the direction of the BSCS X axis. DY, DZ — Offset of the BSCS from the BACS along the axis direction of the BSCS. To Define Beam Orientation 1. Select Properties>Beam Orientations. The Beam Orientations dialog box appears with a list of previously defined orientations. Note: You can also access this dialog box from the Beam Definition dialog box by clicking the More button in the Orientation area. 2. Click the New button. The Beam Orientation Definition dialog box appears. 3. Enter a descriptive name for the beam orientation, or accept the default name. 4. Optionally, enter a description. 5. Enter the orientation angle. 6. Select Shape Origin or Shear Center as the attribute that you want to offset with respect to the BACS. 7. Enter values for DY and DZ. In the FEM mode, you can also enter a value for DX. 8. Click OK to save the definition and return to the Beam Orientations dialog box. The beam orientation definition appears in the list. Beam Releases About Beam Releases Use the Properties>Beam Releases command to specify the degrees of freedom you want to release for a beam's ends. If you do not define a beam release, Mechanica fixes all degrees of freedom at the ends of the beam. Beam releases determine the degrees of freedom that do not participate in a connection at the end of a beam. You can specify beam releases for both straight and curved beams if they are defined using two entities, such as point-to-point beams. You cannot specify beam releases for beams based on edges or curves. When you apply a beam release definition to your beam, Mechanica displays a beam release icon on the model that illustrates which degrees of freedom are fixed and which are free. When you select the Properties>Beam Releases command, the Beam Releases dialog box appears. You can also access this dialog box by clicking the More button in the Releases area of the Beam Definition dialog box. Use the items on the 267 Structural and Thermal Simulation - Help Topic Collection Beam Releases dialog box to manage the beam releases for your model. The dialog box includes these items: • • • Description — Displays any description you entered for the beam release on the Beam Release Definition dialog box. New — Opens the Beam Release Definition dialog box to allow you to specify the degrees of freedom for the beam end. Copy — Copies the selected beam release to a new name and adds it to the list. Mechanica gives the copy the default name BeamReleasex, where x is a number that is one greater than the number of beam releases in the list. To change the name, use Edit. Edit — Opens the Beam Release Definition dialog box to allow you to modify the current definition for the selected beam release. Delete — Remove the selected beam release from the list. • • Beam Release Definition Dialog Box Use the Beam Release Definition dialog box to specify the degrees of freedom you want to release on the ends of your beams. When you click the New button on the Beam Release dialog box, this dialog box appears with the following items: • • • Name — Enter a name or accept the default name. Description — Enter an optional description for the beam release. The description appears on the Beam Releases dialog box when you select the beam release from the list. Degree of Freedom to Release Relative to Beam Action Coordinate System — Select a button to instruct Mechanica to release that degree of freedom on the beam end. The software uses the BACS to define the direction for the degrees of freedom. o Translation — Dx, Dy, Dz o Rotation — Rx, Ry, Rz Beam Release Icons When you create a beam release, the software displays a graphical icon on the beam, positioned toward the end to which the release is applied. The icon is a triad, with each leg of the triad representing the X, Y, and Z directions. The X direction is aligned with the positive X direction of the beam, the Y direction with the positive Y direction. Note: The software does not display beam releases by default. You can display them by selecting View>Simulation Display>Visibilities, and clicking their check box. 268 Structural and Thermal Simulation If a degree of freedom is released in any direction, Mechanica adds the appropriate indicator to the icon: • • arrow head — indicates a translational release of the degree of freedom for the indicated direction ring — indicates a rotational release of the degree of freedom for the indicated direction In the following illustration, the beam release has degrees of freedom released in all six directions: To Create a Beam Release 1. Select Properties>Beam Releases. The Beam Releases dialog box appears. Note: You can also access this dialog box by clicking the More button in the Release area of the Beam Definition dialog box. Click the New button. The Beam Release Definition dialog box appears. Enter a name for the beam release or accept the default name. Optionally, enter a description. Select the degrees of freedom you want to release by toggling on any of the Translation or Rotation buttons. 6. Click OK to complete the definition. 2. 3. 4. 5. Shell Properties About Shell Properties Use the Properties>Shell Properties command to create and manage shell properties. If you want shells that are not homogeneous or shells that are comprised of several layers, or plies, you must create shell properties for your model. 269 Structural and Thermal Simulation - Help Topic Collection You can assign shell properties to the following geometric entities, depending on the model type: Model Type 3D Entity surface (applies the shell property to shell elements) surface (applies the shell property to 2D plate elements) curve (applies the shell property to 2D shell elements) curve (applies the shell property to 2D shell elements) 2D Plane Stress 2D Plane Strain 2D Axisymmetric You can assign a shell property (its thickness and laminate matrices) to a face, region, or datum surface. You can also define a shell property that will reside in the shell property library, but is not assigned to a particular entity. The shell property library file is named mshlprp.lib. When you select the Properties>Shell Properties command, the Shell Properties dialog box appears. You use this dialog box to define the properties of a shell as you define the shell, or you can define a shell property and save it in the library. Before you define shell properties, see Guidelines for Using Shell Properties. To learn more about shell properties, see Shell Thickness. You can define three types of shell properties—homogeneous, laminate layup, and laminate stiffness. Shell Property Library Library Lists for Beam Sections, Shell Properties, and Spring Properties You can save beam section definitions, shell properties, and spring stiffness properties in property-specific libraries. These libraries are a convenient way to use the same property definition for more than one model. There is no limit to the number of property definitions you can have in a model or in your library. You can use the library lists on the Beam Sections, Shell Properties, and Spring Properties dialog boxes to add property definitions to these libraries, or to move property definitions from a library to your model. For information on how Mechanica saves the libraries, see Managing Library Files. • Adding to the libraries — After you create a property definition, use the left arrow button on the appropriate dialog box to move the definition from the 270 Structural and Thermal Simulation Entity in Model list to the Entity in Library list. This places the current property definition in your library. Be aware that Mechanica creates and saves the property-specific library file as soon as you move the first property from the Entity in Model list to the Entity in Library list. If the property definition you are adding has the same name as a definition already in the library, Mechanica tells you that the name already exists and asks if you want to overwrite it. If you select No, Mechanica does not add the current definition to the library. You cannot, overwrite a property definition in the Entity in Model list with a property definition with the same name from the Entity in Library list. If you create a new property definition with the same name as a definition already in the library, the left arrow button becomes inactive. • Editing library definitions — To edit a property definition from the library, use the right arrow button to move the property definition from the Entity in Library list to the Entity in Model list and select Edit to open the dialog box that you used to create the property definition. When you are finished editing, use the left arrow button to move it back to the Entity in Library list. Managing Library Files Mechanica handles the libraries for beam sections differently from the libraries for shell and spring properties. • Beam sections — beam_sections directory The beam_sections directory contains one file for every beam section definition in your library. The files have the same name as the beam section definition, with the extension .bsf. In addition, for sketched sections, Mechanica saves a .sec file with the sketch information. To delete a property definition from the beam section library, delete the appropriate .bsf file. Note that if you have a beam section library file (mbmsct.lib) from an earlier release present in one of the directories where Mechanica searches for the libraries and you save a new beam section into that library, the software creates a beam_sections directory that includes a .bsf file for each of the previous beam section definitions. Mechanica retains the original beam section library file so you can archive it or use it with older Mechanica releases that support .lib files for beam sections. • • Shell properties — mshlprp.lib. Spring stiffness properties — mspstf.lib The default location for all library files is your home directory, but you can move it to a different directory. You can use the environment variable $HOMEDRIVE to set your home directory on Windows platforms. 271 Structural and Thermal Simulation - Help Topic Collection When you access the library, Mechanica looks for the library file in the following directories in this order: 1. the directory from which you started Mechanica 2. your home directory 3. the lib subdirectory of the Mechanica home directory You can move or copy the library files into any of the above directories. Note: For the beam section library, you can specify another location for the beam_sections directory with the config.pro option sim_beamsec_path. You must use a full path for this option. Shell Property Types There are two basic kinds of shells: Homogeneous • • Used for 2D and 3D shells Consists of a single material whose properties do not vary through the thickness of the shell Used for 3D shells Consists of one or more materials whose properties may vary through the thickness of the shell Laminate • • There are three types of shell properties: • • • Homogeneous — Assigned to homogeneous shells. Laminate Stiffness — Assigned to laminate shells to specify their degree of stiffness. Laminate Layup — Assigned to laminate shells to define them as layers of shells. For more information about defining these property types, see the description of Property Type. Guidelines for Using Shell Properties The following are guidelines for using shell properties: • • If you assign a shell definition to a surface that will be compressed, Mechanica associates the shell property with the resulting midsurface. A shell definition assigned to a surface will overwrite the calculated shell thickness of the paired model. A shell definition assigned to the red side will overwrite the property assigned to the yellow side of a paired model. 272 Structural and Thermal Simulation • If you define a shell of variable thickness, be aware that Mechanica takes the value of the thickness from the shell, rather than from the actual thickness of the part. Shell Properties Dialog Box When you select Properties>Shell Properties, the Shell Properties dialog box appears. You can also access this dialog box by clicking More on the Shell Definition dialog box after you have selected Type Advanced. You use this dialog box to do the following: • • • Create new shell properties in your model. Edit, copy, or delete existing shell properties. Move shell properties into or out of the library using the right and left arrows. When you click New to create a new shell property, the Shell Property Definition dialog box appears. Shell Property Definition Dialog Box Use this dialog box to define properties for shells on your model. The properties you define for your shells depend upon whether you are working with a 2D or 3D model, and upon the type of shell you want to simulate. Homogeneous • • Used for 2D and 3D shells Consists of a single material whose properties do not vary through the thickness of the shell. Laminate • • Used for 3D shells Consists of one or more materials whose properties may vary through the thickness of the shell. When you click New on the Shell Properties dialog box, the Shell Property Definition dialog box appears with these items: • • • Name — Enter a name or accept the default name. Description — Enter an optional description. Property Type — Select Homogeneous, Laminate Layup, or Laminate Stiffness. The items on the dialog box change depending upon your selection. Homogeneous Stiffness To define a homogeneous shell property type, you must specify a value in the Thickness field. You enter a positive value to define shell thickness for shells, 2D shells, 2D plates, surfaces, or curves you selected. When Mechanica creates the shell 273 Structural and Thermal Simulation - Help Topic Collection elements for the surface, it applies the thickness you specify for the shell property equally on both sides of the selected surface. For example, if you specify a shell thickness of 1, Mechanica places 0.5 on the top side of the surface and 0.5 on the bottom side. The Thickness field is a parameter-capable edit field. You can create or select a Pro/ENGINEER parameter for the thickness by clicking the p button. Laminate Stiffness To define a laminate stiffness shell property type, you must specify several values for Mechanica using the Shell Property Definition dialog box. Use the Stiffness tab and the Mass and Additional Calc tab to move from one portion of the dialog box to another. For each component there is a non-editable text field that displays the units. If you are working in the FEM mode, Mechanica does not support laminate stiffness. The components of the following stiffnesses are relative to the material orientation you have assigned to the shell. Entries in the fields on this dialog box are optional unless stated otherwise. You define them using the equations described in Shell Property Equations: • • • • Extensional Stiffness — You must enter positive real numbers for A11, A22, and A66. Coupling Stiffness — Entries in these fields are optional. Bending Stiffness — You must enter positive real numbers for D11, D22, and D66. Transverse Shear Stiffness — You must enter positive real numbers for A44 and A55. The thermal resultant coefficients reflect the additional load applied to the laminate shell as a result of a difference in thermal properties in the ply materials. Mechanica assumes that the temperature distribution is uniform through the thickness of the shell. Keep this in mind when entering values in the Thermal Resultant Coefficients area for: • • Force Moment If you want to perform a modal analysis of your model, or if this shell property set is to contribute to the total mass of the model, you must enter values for: • • Mass Per Unit Area Rotary Inertia Per Unit Area If you click the Calculate Stresses and Strains button, more items appear. For ease of use when modeling composites and the ability to compute ply stresses in the postprocessor, use Laminate Layup rather than Laminate Stiffness. 274 Structural and Thermal Simulation Laminate Layup A laminate consists of a number of layers, or plies, stacked on each other. When you define your 3D shell property as a laminate layup, you can: • • • specify the properties for each ply obtain ply-by-ply stress results (native mode) parameterize ply thickness and orientation You can review the properties for each ply in the results. For a picture of what a laminate layup shell looks like, see Laminate Layup Illustration. When you select Laminate Layup on the Shell Property Definition dialog box, additional items appear on the dialog box: • Layup For each ply, you must specify the following information: • • • • Material or Sub-laminate Thickness Orientation Number Use the buttons to the right of the dialog box to control your laminate layup table. For ease of use when modeling composites and the ability to compute ply stresses in the postprocessor, use Laminate Layup rather than Laminate Stiffness. Note: In the FEM mode, Mechanica supports laminate layup shell properties and material orientations assigned to surfaces for NASTRAN only. If you are running an analysis with another solver, Mechanica informs you that you cannot run the analysis with the solver you have chosen. To Define Shell Properties 1. Select Properties>Shell Properties, or click More on the Shell Definition dialog box. The Shell Properties dialog box appears. 2. 3. 4. 5. Click New. The Shell Property Definition dialog box appears. Enter a name, or accept the default name. Optionally, enter a description. Select one of the following property types. The items on the dialog box change depending upon your selection. o Homogeneous 275 Structural and Thermal Simulation - Help Topic Collection o Laminate Layup o Laminate Stiffness 6. If you select Homogeneous, enter a real-number value for the thickness, or click p to select or create a Pro/ENGINEER parameter. Mechanica displays the units for the thickness. 7. If you select Laminate Stiffness or Laminate Layup, fill out the information on the dialog box. 8. Click OK to accept your definition, or Cancel to discard your changes and close the dialog box. Spring Properties About Spring Properties You can define spring properties in one of the following ways, depending on the situation. • • Use the Properties>Spring Properties command. If you are defining and advanced or to-ground spring, you can also use the More button in the Properties area of the Spring Definition dialog box to create a spring property. In either case, Mechanica opens the Spring Properties dialog box, which you can use to manage spring properties for an Advanced or To Ground spring. This dialog box lists any stiffness properties already created for your model and lets you create new ones. The dialog box contains the following items: • Spring Properties in Library — Displays a list of the spring properties you saved in your library. You can select one of these definitions and click the right arrow to move it to the Spring Properties in Model list. The spring properties library file is called mspstf.lib. Spring Properties in Model — Displays a scrollable list of the spring properties that can be assigned to one or more springs in your model. You can select one of these spring property names to assign to the current spring definition. To add a spring property to your library, select it and use the left arrow to add it to the Spring Properties in Library List. Description — This non-editable field displays the (optional) description you entered for the spring property currently selected in the Spring Properties in Library or Spring Properties in Model list. New — Opens the Spring Properties Definition dialog box opens to allow you to create a new spring property. Copy — Copies the selected spring property to a new name and adds it to the Spring Properties in Model list. A new spring property appears in the list with the default name SpringPropx, where x is one more than the number of items created for the model. To change the name, select it and click Edit. Edit — Opens the Spring Properties Definition dialog box with the values of the selected spring property. Delete — Removes the selected spring property from the Spring Properties in Model list. • • • • • • 276 Structural and Thermal Simulation If you accessed the Spring Properties dialog box from the Spring Definition dialog box, when you close the Spring Properties dialog box, the software uses the property you selected from the Spring Properties in Model list for the current spring definition, and displays the property name in the Spring Definition dialog box. If you did not select a property, the first property in the Spring Properties in Model list is selected by default. Spring Property Library Library Lists for Beam Sections, Shell Properties, and Spring Properties You can save beam section definitions, shell properties, and spring stiffness properties in property-specific libraries. These libraries are a convenient way to use the same property definition for more than one model. There is no limit to the number of property definitions you can have in a model or in your library. You can use the library lists on the Beam Sections, Shell Properties, and Spring Properties dialog boxes to add property definitions to these libraries, or to move property definitions from a library to your model. For information on how Mechanica saves the libraries, see Managing Library Files. • Adding to the libraries — After you create a property definition, use the left arrow button on the appropriate dialog box to move the definition from the Entity in Model list to the Entity in Library list. This places the current property definition in your library. Be aware that Mechanica creates and saves the property-specific library file as soon as you move the first property from the Entity in Model list to the Entity in Library list. If the property definition you are adding has the same name as a definition already in the library, Mechanica tells you that the name already exists and asks if you want to overwrite it. If you select No, Mechanica does not add the current definition to the library. You cannot, overwrite a property definition in the Entity in Model list with a property definition with the same name from the Entity in Library list. If you create a new property definition with the same name as a definition already in the library, the left arrow button becomes inactive. • Editing library definitions — To edit a property definition from the library, use the right arrow button to move the property definition from the Entity in Library list to the Entity in Model list and select Edit to open the dialog box that you used to create the property definition. When you are finished editing, use the left arrow button to move it back to the Entity in Library list. 277 Structural and Thermal Simulation - Help Topic Collection Managing Library Files Mechanica handles the libraries for beam sections differently from the libraries for shell and spring properties. • Beam sections — beam_sections directory The beam_sections directory contains one file for every beam section definition in your library. The files have the same name as the beam section definition, with the extension .bsf. In addition, for sketched sections, Mechanica saves a .sec file with the sketch information. To delete a property definition from the beam section library, delete the appropriate .bsf file. Note that if you have a beam section library file (mbmsct.lib) from an earlier release present in one of the directories where Mechanica searches for the libraries and you save a new beam section into that library, the software creates a beam_sections directory that includes a .bsf file for each of the previous beam section definitions. Mechanica retains the original beam section library file so you can archive it or use it with older Mechanica releases that support .lib files for beam sections. • • Shell properties — mshlprp.lib. Spring stiffness properties — mspstf.lib The default location for all library files is your home directory, but you can move it to a different directory. You can use the environment variable $HOMEDRIVE to set your home directory on Windows platforms. When you access the library, Mechanica looks for the library file in the following directories in this order: 1. the directory from which you started Mechanica 2. your home directory 3. the lib subdirectory of the Mechanica home directory You can move or copy the library files into any of the above directories. Note: For the beam section library, you can specify another location for the beam_sections directory with the config.pro option sim_beamsec_path. You must use a full path for this option. 278 Structural and Thermal Simulation Defining Spring Stiffness and Damping Properties When defining spring properties for an Advanced or To Ground spring, click New or Edit on the Spring Properties dialog box. Mechanica displays the Spring Properties Definition dialog box on which you can enter the following information: • • • Name — The name for the spring property. Enter a name or accept the default name . Description — An optional description of the spring property. Stiffness tab — These components represent the extensional and torsional characteristics of the spring. You should enter a non-zero value for at least one of these items. Enter non-negative values for the following: o o o o o o Kxx — Specifies the xx component of extensional stiffness relative to the spring's coordinate system. Kyy — Specifies the yy component of extensional stiffness relative to the spring's coordinate system. Kzz — Specifies the zz component of extensional stiffness relative to the spring's coordinate system. Txx — Specifies the xx component of torsional stiffness relative to the spring's coordinate system. Tyy — Specifies the yy component of torsional stiffness relative to the spring's coordinate system. Tzz — Specifies the zz component of torsional stiffness relative to the spring's coordinate system. • Damping tab (FEM mode only) — Specify non-negative values for the following properties of the spring: o o o Cxx — Specifies the xx component of the damping coefficient relative to the spring's coordinate system. Cyy — Specifies the yy component of the damping coefficient relative to the spring's coordinate system. Czz — Specifies the zz component of the damping coefficient relative to the spring's coordinate system. For information on defining extensional and torsional stiffness for 2D and 3D models, see Defining Spring Properties for 2D and 3D Models. Note that Mechanica labels the stiffness components using Cartesian component directions. To review the equivalent component directions for cylindrical and spherical components, see Axis and Component Equivalents in Different Coordinate Systems. 279 Structural and Thermal Simulation - Help Topic Collection Defining Spring Properties for 2D and 3D Models There are a few differences you should be aware of when you define extensional and torsional stiffness properties for springs on the Spring Properties Definition dialog box: Extensional stiffness • • For 3D models, you specify extensional stiffness for Kxx, Kyy, and Kzz. For 2D models, you specify extensional stiffness only for Kxx and Kyy. Torsional stiffness • • For 3D models, you specify torsional stiffness in Txx, Tyy, and Tzz. For 2D plane strain and 2D axisymmetric models, you specify torsional stiffness only in Tzz. For 2D plane stress models, you do not specify torsional stiffness. A spring in a 2D plane stress model does not contribute to rotations when the engine calculates results. To Define Spring Properties 1. Select Properties>Spring Properties, or click More on the Spring Definition dialog box. The Spring Properties dialog box appears. Note: You can also access this dialog box from the Spring Definition dialog box by clicking the More button in the Orientation area. 2. 3. 4. 5. Click New. The Spring Properties Definition dialog box appears. Enter a name or accept the default name. Optionally, enter a description. On the Stiffness tab, enter a non-negative real number for at least one of the extensional and torsional components: • Kxx • Kyy • Kzz • Txx • Tyy • Txx 6. In FEM mode only, on the Damping tab, enter a non-negative real number for any of the damping coefficients: • Cxx • Cyy • Czz 7. Click OK to accept your definition or Cancel to discard your changes and close the dialog box. 280 Structural and Thermal Simulation Mass Properties About Mass Properties You can define mass properties in one of the following ways, depending on the situation. • • Use the Properties>Mass Properties command. If you are defining an advanced mass, you can also use the More button in the Properties area of the Mass Definition dialog box to create a mass property. In either case, Mechanica displays the Mass Properties dialog box, which you can use to create a mass property. From this dialog box, you can also edit, copy, or delete an existing property. To create a new property, click New. The Mass Property Definition dialog box appears. You use this dialog box to define the property. This dialog box includes the following items: • • • • Name — Enter a name for the mass property, or use the default name provided. Description — Enter an optional description. Mass — Specify the value of the mass in units consistent with the other units you have used in this model. You must enter a positive value. Moments of Inertia — Specify the moments of inertia about each mass element's center of gravity with respect to the axes and principal planes of the WCS. For 3D models, you can specify values for Ixx, Iyy, Izz, Ixy, Ixz, and Iyz. For plane strain and 2D axisymmetric models, you can specify a value for only Izz. For plane stress models, you cannot specify any moments of inertia. The default value for all moments is 0. Depending on the situation, you may not need to specify all of the diagonal terms when you specify moments of inertia. Note that Mechanica labels the moments of inertia using Cartesian component directions. To review the equivalent component directions for cylindrical and spherical components, see Axis and Component Equivalents in Different Coordinate Systems. Specifying the Off-diagonal Moments of Inertia The moment of inertia of a mass element depends on the coordinate system you use to define the property. It consists of six independent components: Ixx, Iyy, Izz, Ixy, Ixz, and Iyz, where the subscripts refer to the axes of the reference coordinate system. 281 Structural and Thermal Simulation - Help Topic Collection In most cases, the moment of inertia definition requires only three diagonal terms— Ixx, Iyy, and Izz—with zero values for the off-diagonal terms. This depends on the principal coordinate system you use to define the moment of inertia and is always true if any two of the three coordinate system planes are planes of reflection symmetry for the mass element. Materials About Materials Use the Properties>Materials command to specify materials for geometry and idealizations in your part or assembly and to save materials in a library. You can assign materials to parts, surfaces, and curves. When doing so, be aware of the following: • • If you are assigning materials to surfaces or, for 2D models, assigning materials to curves, Mechanica uses the material you assign only if the surface or curve is part of a shell. In the case of curves for 3D models, you perform the material assignment when you create the beam idealization rather than through the Properties>Materials command. However, the dialog boxes you use are the same. In FEM mode, you can assign materials to parts, solid portions of a model, and shell pairs. • If you select this command in native mode, the Materials dialog box appears. If you select the Materials command in the FEM mode, the FEM MATERIAL menu appears. To learn more about materials, see: • • • • • Guidelines for Using Materials Material Types Material Property Requirements Material Basics Material Definition for Native and FEM Mode Guidelines and Background Guidelines for Using Materials Be aware of the following when using materials: • • • • 282 You can use the same material properties in Structure and Thermal. If you assign a material to a part, it is not automatically assigned to all volumes, surfaces, and curves. If you are working in the assembly mode, you can individually assign materials to the parts in your assembly. In Structure, you cannot assign materials to springs or masses. Structural and Thermal Simulation • • If you assign materials to a curve in a solid or shell model, the curve's materials are independent of the materials you assign to the part. Mechanica maintains consistency between Pro/ENGINEER and Mechanica data for all materials for the following material properties: name, density, and specific heat. For Young's modulus, Poisson's ratio, shear modulus, coefficient of thermal expansion, and thermal conductivity, consistency is maintained between the databases only for isotropic materials. Orthotropic materials defined in Mechanica will not be defined in the Pro/ENGINEER database. • • • • • You can assign the value of Pro/ENGINEER parameters as you create materials. In Structure, you can create isotropic materials that are temperaturedependent by specifying that Young's modulus, Poisson's ratio, or the coefficient of thermal expansion is a function of temperature. You can also save materials in a library and use them across models. You cannot define material orientation for curves—or, by implication, beams. If you assign a material orientation to a part and that part gets compressed to a surface, the definition of the material orientation changes from one defined over a part to one defined over a surface. The material orientation applies to all the surfaces that are created when Mechanica compresses the part. Material Types You can define properties for three types of material symmetry: • • • Isotropic — a material with an infinite number of planes of material symmetry, making the properties equal in all directions. You enter a single value for each property. Orthotropic — a material with symmetry relative to three mutually perpendicular planes. You enter three values for each property. Transversely isotropic — a material with rotational symmetry about an axis. The properties are equal for all directions in one plane, the plane of isotropy. You enter two values for each property—one for the plane of isotropy, and one for the remaining principal material direction. These types are independent for Structure and Thermal. Thus, a material may have isotropic structural properties and orthotropic thermal properties. You can assign isotropic materials to any entity that requires materials. 283 Structural and Thermal Simulation - Help Topic Collection You can assign orthotropic and transversely isotropic materials to the following entities according to model type: 3D Plane Stress/2D Plate All Other 2D Model Types face/surface Part face/surface shell shell Material Property Requirements Assign these material properties as appropriate: Property mass density Type Structural and Thermal Structural and Thermal Required only for modal analyses cost per unit mass no, but useful if you want Mechanica to calculate model cost Young's modulus Structural yes Poisson's ratio Structural yes shear modulus Structural yes (Mechanica calculates this automatically for isotropic materials) only for models with thermal loads coefficient of thermal expansion failure criterion Structural Structural only to calculate failure indices 284 Structural and Thermal Simulation Property specific heat Type Thermal Required only for transient thermal analyses thermal conductivity ultimate tensile strength material type fatigue strength reduction factor surface finish Thermal Structural yes only for fatigue analysis Structural Structural only for fatigue analysis only for fatigue analysis Structural only for fatigue analysis Note: You can create isotropic material properties that are temperaturedependent by specifying Young's modulus, Poisson's ratio, or coefficient of thermal expansion as a function of temperature. Material Basics You can save materials in a library and use them across models. Both Mechanica products—Structure and Thermal—can use the properties from a single material set. You can use materials in the following ways: • • • You can assign a material to one or more geometric entities in a model. You can place a material in a material library. You can create a new material. There is no limit to the number of materials you can have in a model or in your library. For more information, see Materials Dialog Box or, for FEM mode, FEM MATERIAL menu. Material Definition for Native and FEM Mode You can define materials for your model in Structure or Thermal. If you plan to work with your model in both Structure and Thermal, Mechanica assigns the same material for both products. For example, if you assign the material for your Structure model as Aluminum 2014, Mechanica assumes Aluminum 2014 for Thermal as well. 285 Structural and Thermal Simulation - Help Topic Collection However, several of the material properties available in Structure are different from those available in Thermal. For instance, Structure enables you to define such properties as Young's modulus and Poisson's ratio, whereas Thermal enables you to define conductivity and specific heat. Mechanica retains mass density across products. In other words, Mechanica assumes the mass density you define in Structure is the mass density in Thermal, and the reverse. When you create a material in the native mode, the material will also be created automatically in the FEM database, and the reverse is also true. However, the synchronization of property data and assignments between the native mode and the FEM mode depends on the situation. Be aware of the following factors in regard to synchronization: • • • Property data for isotropic materials without parameters or functions is synchronized. Material assignments to beams and shells are synchronized. Material assignments to parts are not synchronized. Material Library The material library is a convenient way to use the same material in more than one model. When you install Mechanica, the material library consists of a set of standard materials known as the default material library. If you do not find the material you want in the default material library, you can create your own material and add it to the library. When you save a material to the library, Mechanica creates a library file named mmatl.lib in your working directory. This new file contains all the materials in the Materials in Library list—both the Mechanica default materials and any materials you added. There is no limit to the number of materials you can have in your material library. You can edit any material in the library, whether the material is part of Mechanica's default material set or you created the material yourself. However, you cannot delete materials from the material library. Thus, if you create a new material and save it to the library, it will always be there. When you access the material library, Mechanica looks for the mmatl.lib file in the following directories in this order: 1. the directory from which you started Mechanica (working directory) 2. your home directory 3. the lib subdirectory of the directory in which Mechanica was installed You can move or copy the mmatl.lib file into any of these three directories. 286 Structural and Thermal Simulation Default Material Library Mechanica has a default material library, located in the lib subdirectory of the Mechanica installation directory, containing a few selected materials. This library is intended, primarily, as a template for you to follow when creating your own material library. The properties in the library included with Mechanica are taken from standard references and textbooks and may not match exactly the properties of the material you intend to use. You should review all material properties to ensure that their values are accurate for your material and that their units are consistent with those of the model. Also, the property values given are those for materials at room temperature. Actual material properties change with temperature. The Mechanica library contains isotropic materials only. Units for Materials Pro/ENGINEER and Mechanica store the material data for your model in terms of a principal system of units. Mechanica displays only materials with units in the material library. You can define materials by entering data with units that are different from the principal system of units. Mechanica automatically converts the data you enter to the principal system of units when you run a design study. If you plan to export your model to independent mode of Mechanica, make a note of your system of units. Mechanica does not display your system of units in the independent mode. Mechanica displays only materials with units in the material library. The values for density, Young's modulus, and the thermal expansion coefficient are given in the indicated system of units. The units used for conductivity follow a slightly different system of units: • • For the meter-newton-second and millimeter-newton-second systems of units, the conductivity value is in the indicated system of units—Watts/meterKelvin and milli-Watts/millimeter-Kelvin, respectively. For the foot-pound-second and inch-pound-second systems of units, the conductivity value is in Btu/hour-foot-degree-Fahrenheit and Btu/hour-inchdegree-Fahrenheit (not in pound/second-degree-Fahrenheit). For transient thermal analysis, all of these measuring systems measure conductivity in seconds. 287 Structural and Thermal Simulation - Help Topic Collection Materials in Native Mode Materials Dialog Box When you select Properties>Materials in the native mode or Properties>Materials>Assign in the FEM mode, Mechanica displays the Materials dialog box. Mechanica also opens this dialog box as you define certain connections, such as spot welds, or when you create certain idealizations, such as beams and shells. Use the Materials dialog box to: • • • create, edit, copy, and delete materials from your model database assign materials to or delete materials from your model add a material to the library The following lists appear on the dialog box: • • Materials In Library Materials In Model Use the arrow keys to do the following: • • Right arrow — to add a material to the model from the library. This places the material in the model database. Note that the material must still be explicitly assigned to have an effect on an analysis. Left arrow — to add a material to the library from the model The following buttons on the dialog box enable you to perform various actions: • Assign — This option is not available when creating a beam definition or shell definition. This option is inactive in the FEM mode because you perform FEM mode material assignment from the FEM MATERIAL menu and not from this dialog box. New Edit Copy Delete — This option is not available for a material associated with an idealization, such as a beam definition or shell definition. • • • • Materials In Library List This is a list of the materials saved in your library. You can select one of these materials to assign to your model. If you do not have your own library, this column displays the materials from the default Mechanica material library. 288 Structural and Thermal Simulation If you add a new material to the material library, the software places the new material library in your home directory. Materials In Model List This is a list of the materials in the model database. You can select one or more materials to assign to entities. Mechanica selects the first set on this list by default. Assign a Material On the Materials dialog box, click Assign to assign a material from the Materials In Library list or the Materials In Model list to one or more geometric entities. To add a material from either list to your model, select a material on the list, and click Assign. You can assign materials to parts, faces/surfaces, edges/curves. Note: The Assign button is inactive in FEM mode because you assign materials through the FEM MATERIAL menu rather than from the Materials dialog box. If you select a material from the Materials In Model list and click Assign, a dropdown list of entity types appears. If you select an entity type, you should use the normal selection methods to select one or more entities on the model. To change the properties of a material, click Edit to open the Material Definition dialog box where you can alter any property. You can verify an assignment by selecting a material on the Materials In Model list and reviewing the highlighted part or geometry. After you assign materials to your model, Mechanica lists those materials on the Model Tree. If you select the material in the Model Tree, Mechanica highlights the part or surface to which it is assigned. For example, if you select bronze on the Model Tree, Mechanica will highlight every part or surface that is bronze. When assigning materials, be aware of these factors: • When you assign a material to a part, Mechanica does not automatically assign the material to curves and surfaces of that part. To assign a material to curves or surfaces, you must specifically select the Edge/Curve or Face/Surface command on the Assign drop-down menu. You cannot change the name of a material. However, you can copy the material using a different name, thus achieving a similar effect. There is no need to assign a material to a curve for a 3D model. To assign materials to beams, use the Beam Definition dialog box instead of the Material Definition dialog box. If a surface has a material that is different from the material assigned to the volume it makes, reviewing the material assigned to the surface highlights just the surface, while reviewing the material assigned to the volume highlights the entire volume. You can assign a material to a shell pair surface that is different from the material that you assign to the part. 289 • • • • Structural and Thermal Simulation - Help Topic Collection • Mechanica handles material assignment differently depending on whether you are working in part mode or assembly mode. To Assign a Material 1. Select Properties>Materials or click The Materials dialog box appears. 2. Select a material using one of the following methods: o Highlight a material on the Materials In Model list. o Highlight a material on the Materials In Library list. 3. Click Assign. A drop-down list of entities appears. 4. Select an entity type and use the normal selection methods to select one or more entities on your model. The material you selected appears on the Model Tree. 5. If you are working with an assembly and you select Part from the Assign drop-down list, you can use either the Model Tree, or the normal selection methods, to select a subassembly or the entire assembly. In this case, Mechanica implicitly assigns the material to all parts, datum, geometry, edges, and surfaces in the selected assembly or subassembly. 6. When you confirm your selection, the material is assigned to the entity, unless a material is already assigned to it. 7. If the entity you select is associated with a material other than the one you are trying to assign, Mechanica asks if you want to change the material. o o Click Yes to replace the current material with the selected material and be returned to the Materials dialog box. Click No to return to the Materials dialog box without changing the material. . This message does not appear if you assigned the same material in a product other than the one you are currently using—for example, if you previously assigned a material in Thermal but are now in Structure. 290 Structural and Thermal Simulation Create a Material Click New on the Materials dialog box to create a material. A blank Material Definition dialog box appears on which to define the material. After you complete the definition and click OK, the new material name appears on the Materials In Model list. Note that you can add a material to the Materials In Model list in the following ways: • • select a material from the library, and click the right arrow create a new material by using the New button on the Materials dialog box Either method adds the new material to the database, but the material is not associated with any geometry until you assign it in either native Mode or FEM mode. If you add a new material to the material library, the software places the new material library in your home directory. Material Definition Dialog Box Use the Material Definition dialog box to: • • enter material properties for a new material review and change properties for an existing material On this dialog box, you enter the material name and an optional description, as well as determine definitions for: • • Cost Density The principal system of units previously set for the model determines the units that appear by default on this dialog box. You can specify the system of units and also create individual units for your model. Choose one of the following tabs: • • Structural — to define structural material properties for a model Thermal — to define thermal material properties for a model Different options appear on the Structural and Thermal tabs, depending on the material symmetry you select: • • • Isotropic (in FEM mode, only isotropic materials are available) Orthotropic Transversely Isotropic 291 Structural and Thermal Simulation - Help Topic Collection These symmetries are independent for Structure and Thermal. A material may have isotopic structural properties and orthotropic thermal properties. The Mechanica library contains isotropic materials only. You define an isotropic material for materials such as steel. For wood or fiberreinforced composite, you define an orthotropic or transversely isotropic material. To Create a Material 1. Select Properties>Materials. In FEM mode, also select Whole Part on the FEM MATERIAL menu. The Materials dialog box appears. 2. Click New. The Material Definition dialog box appears. 3. Enter the appropriate material properties on the Material Definition dialog box. 4. Click OK on the Material Definition dialog box. The material you created appears in the Materials In Model list on the Materials dialog box. Edit a Material Click Edit in the Materials dialog box to edit an assigned or unassigned material in the Materials in Model list. You can also edit a material in the Materials in Library list, but you must first move the material to the Materials in Model list. You can then move the edited material to the Materials in Library list, thus overwriting the original library material. When you click Edit, the Material Definition dialog box appears. Change the fields in the dialog box to the values you want for your material properties. By editing a material, you change the material on all of the geometric entities to which it was assigned. To Edit a Material By editing a material, you change the material on all the geometric entities to which it was assigned. 1. Select Properties>Materials or click . In the FEM mode, also select Whole Part on the FEM MATERIAL menu. The Materials dialog box appears. 292 Structural and Thermal Simulation 2. Select a material from the Materials in Model list. The material you select must be a user-created material rather than one of the standard materials in Mechanica's material library. 3. Click Edit. The Material Definition dialog box appears. 4. Change the fields in the dialog box to the values you want. As a quick alternative to this procedure, you can select the material you want to edit from the model tree. Right-click on the material or, for FEM mode solid chunks, the material assignment, and select the Edit Definition command from the object action menu. Copy a Material Click Copy on the Materials dialog box to duplicate a material on the Materials In Model list. You can also copy a material in the Materials in Library list, but you must first move the material to the Materials in Model list. Note that you cannot make an exact copy of a material because no two materials can have the same name. The materials may be identical in every way except their name. The copy will exist in the model file but not be assigned until you assign the material to a geometric entity. To Copy a Material 1. Select Properties>Materials or click Part on the FEM MATERIAL menu. The Materials dialog box appears. 2. Select a material from the Materials in Model list. 3. Click Copy. The Copy dialog box appears. 4. Enter a new material name xxx in the To text box. Mechanica duplicates a copy of the material xxx and places it in the Materials In Model list with the name of xxx. If the name is too long, the software issues a warning. The copy will exist in the model file but not be assigned until you assign the material to a geometric entity. . In FEM mode, also select Whole 293 Structural and Thermal Simulation - Help Topic Collection Delete a Material Click Delete on the Materials dialog box to delete an assigned or unassigned material from the Materials in Model list, provided that material is not assigned to a shell or beam. You cannot delete any of the materials in the Materials in Library list. If you did not previously assign the material to an entity, Mechanica deletes the material from the model database. If you assigned the material to an entity, the software first asks whether you want to delete the material. Click one of the following buttons: • • No — to retain the material Yes — to delete the material. Mechanica deletes the material from your model and the model database. To Delete a Material 1. Select Properties>Materials or click . In the FEM mode, also select Whole Part on the FEM MATERIAL menu. The Materials dialog box appears. 2. Select a material from the Materials in Model list. The material you select must be a user-created material rather than one of the standard materials in Mechanica's material library. 3. Click Delete. If you did not previously assign the material to an entity, the material is deleted from the model database. 4. When you assign the material to an entity, the software asks whether you want to delete it. Click one of the following buttons: o No — to retain the material o Yes — to delete the material. The material is deleted from the model. As a quick alternative to this procedure, you can select the material you want to delete from the model tree. Right-click on the material and select the Delete command from the object action menu. Materials in FEM Mode FEM MATERIAL Menu When you select Properties>Materials in FEM mode, Mechanica displays the FEM MATERIAL menu. Use this menu to: • 294 assign materials to or unassign materials from your model Structural and Thermal Simulation • review information about a material in your model The following commands enable you to select an object type to which to apply a material: • • Whole Part — Select the whole part. Solid Chunk — Select a surface associated with a solid. The Solid Chunk option enables you to propagate the material throughout the tetrahedral elements in the solid area defined by the surface you select. For Solid Chunk, you must select a surface belonging fully to a solid portion of your model. You cannot select a surface that is only partially associated with a solid. If you use the Solid Chunk option, you create a simulation object known as a Material Assignment. This object appears in the Model Tree with the default name of MaterialAssignX, where X is a unique number. You can rename the material assignment to make its associations more obvious. You can also use the button as a quick alternative to using the FEM MATERIAL menu for assigning a material to a solid chunk. • Shell Pair — Select a shell pair. The following commands on the FEM MATERIAL menu enable you to review information about a material, in addition to assigning materials to and unassigning materials from entities in your model: • Info — Review information about a material. Mechanica displays an information window that shows the material definition. Using commands in the information window, you can edit the material definition if you want to change values for specific properties such as Young's Modulus. Assign — Assign a material to one or more entities of the object type you select on the upper section of the FEM MATERIAL menu. For Solid Chunk and Shell Pair, Mechanica prompts you to select an entity of the chosen object type. After you select an entity on your model, the Materials dialog box appears. Unassign — Unassign a material from one or more entities of the object type you select on the upper section of the FEM MATERIAL menu. For Solid Chunk and Shell Pair, Mechanica prompts you to select an entity of the chosen object type. • • Information About a FEM Material Click Properties>Materials. When the FEM MATERIAL menu appears, select Info to review information about the materials in your model. When you select Info, the SEL MATERIAL menu appears. This menu lists all the materials in your model, whether or not you have assigned them to your part. This list reflects the contents of the Materials in Model area of the Materials dialog 295 Structural and Thermal Simulation - Help Topic Collection box. After you select a material, the Information window appears, which enables you to review and edit material properties. Materials Dialog Box When you select Properties>Materials in the native mode or Properties>Materials>Assign in the FEM mode, Mechanica displays the Materials dialog box. Mechanica also opens this dialog box as you define certain connections, such as spot welds, or when you create certain idealizations, such as beams and shells. Use the Materials dialog box to: • • • create, edit, copy, and delete materials from your model database assign materials to or delete materials from your model add a material to the library The following lists appear on the dialog box: • • Materials In Library Materials In Model Use the arrow keys to do the following: • • Right arrow — to add a material to the model from the library. This places the material in the model database. Note that the material must still be explicitly assigned to have an effect on an analysis. Left arrow — to add a material to the library from the model The following buttons on the dialog box enable you to perform various actions: • Assign — This option is not available when creating a beam definition or shell definition. This option is inactive in the FEM mode because you perform FEM mode material assignment from the FEM MATERIAL menu and not from this dialog box. New Edit Copy Delete — This option is not available for a material associated with an idealization, such as a beam definition or shell definition. • • • • Materials In Library List This is a list of the materials saved in your library. You can select one of these materials to assign to your model. If you do not have your own library, this column displays the materials from the default Mechanica material library. 296 Structural and Thermal Simulation If you add a new material to the material library, the software places the new material library in your home directory. Materials In Model List This is a list of the materials in the model database. You can select one or more materials to assign to entities. Mechanica selects the first set on this list by default. Assign a Material Assign a Material in FEM Mode Click Properties>Materials. When the FEM MATERIAL menu appears with Assign highlighted, select one of the following object types: • • • Whole Part — Enables you to assign a material to the whole part. Solid Chunk — Enables you to propagate a material throughout the tetrahedral elements in the solid area defined by the surface you select. Shell Pair — Enables you to assign a material to a shell pair. If you select Solid Chunk or Shell Pair, Mechanica prompts you to select an entity to which to assign a material. After you select an entity on your model, the Materials dialog box appears. Select a material from the Materials In Library list or from the Materials In Model list, or create a new material. After you click OK, the material is assigned to the selected entity. Repeat this procedure for each entity to which you are assigning a material. To Assign a Material in FEM Mode This procedure assumes that your model does not have assigned materials. 1. Select Properties>Materials or click . The FEM MATERIAL menu opens and software prompts you to select an object type to which to assign the material. 2. Select an object type on the FEM MATERIAL menu. The software prompts you to select an entity on the model. 3. Use the normal selection methods to select an entity or entities on your model. The Materials dialog box opens. 297 Structural and Thermal Simulation - Help Topic Collection 4. Select a material from the Materials In Model list. 5. If you want to use a material from the library, use the right arrow to move the material from the Materials in Library list to the Materials in Model list. The material you selected appears on the Model Tree. 6. Click OK. The material is assigned to the selected entity. Create a Material Click New on the Materials dialog box to create a material. A blank Material Definition dialog box appears on which to define the material. After you complete the definition and click OK, the new material name appears on the Materials In Model list. Note that you can add a material to the Materials In Model list in the following ways: • • select a material from the library, and click the right arrow create a new material by using the New button on the Materials dialog box Either method adds the new material to the database, but the material is not associated with any geometry until you assign it in either native Mode or FEM mode. If you add a new material to the material library, the software places the new material library in your home directory. Material Definition Dialog Box Use the Material Definition dialog box to: • • enter material properties for a new material review and change properties for an existing material On this dialog box, you enter the material name and an optional description, as well as determine definitions for: • • Cost Density The principal system of units previously set for the model determines the units that appear by default on this dialog box. You can specify the system of units and also create individual units for your model. 298 Structural and Thermal Simulation Choose one of the following tabs: • • Structural — to define structural material properties for a model Thermal — to define thermal material properties for a model Different options appear on the Structural and Thermal tabs, depending on the material symmetry you select: • • • Isotropic (in FEM mode, only isotropic materials are available) Orthotropic Transversely Isotropic These symmetries are independent for Structure and Thermal. A material may have isotopic structural properties and orthotropic thermal properties. The Mechanica library contains isotropic materials only. You define an isotropic material for materials such as steel. For wood or fiberreinforced composite, you define an orthotropic or transversely isotropic material. To Create a Material 1. Select Properties>Materials. In FEM mode, also select Whole Part on the FEM MATERIAL menu. The Materials dialog box appears. 2. Click New. The Material Definition dialog box appears. 3. Enter the appropriate material properties on the Material Definition dialog box. 4. Click OK on the Material Definition dialog box. The material you created appears in the Materials In Model list on the Materials dialog box. Edit a Material Click Edit in the Materials dialog box to edit an assigned or unassigned material in the Materials in Model list. You can also edit a material in the Materials in Library list, but you must first move the material to the Materials in Model list. You can then move the edited material to the Materials in Library list, thus overwriting the original library material. When you click Edit, the Material Definition dialog box appears. Change the fields in the dialog box to the values you want for your material properties. By editing a material, you change the material on all of the geometric entities to which it was assigned. 299 Structural and Thermal Simulation - Help Topic Collection To Edit a Material By editing a material, you change the material on all the geometric entities to which it was assigned. 1. Select Properties>Materials or click . In the FEM mode, also select Whole Part on the FEM MATERIAL menu. The Materials dialog box appears. 2. Select a material from the Materials in Model list. The material you select must be a user-created material rather than one of the standard materials in Mechanica's material library. 3. Click Edit. The Material Definition dialog box appears. 4. Change the fields in the dialog box to the values you want. As a quick alternative to this procedure, you can select the material you want to edit from the model tree. Right-click on the material or, for FEM mode solid chunks, the material assignment, and select the Edit Definition command from the object action menu. Copy a Material Click Copy on the Materials dialog box to duplicate a material on the Materials In Model list. You can also copy a material in the Materials in Library list, but you must first move the material to the Materials in Model list. Note that you cannot make an exact copy of a material because no two materials can have the same name. The materials may be identical in every way except their name. The copy will exist in the model file but not be assigned until you assign the material to a geometric entity. To Copy a Material 1. Select Properties>Materials or click Part on the FEM MATERIAL menu. The Materials dialog box appears. 2. Select a material from the Materials in Model list. 3. Click Copy. The Copy dialog box appears. . In FEM mode, also select Whole 300 Structural and Thermal Simulation 4. Enter a new material name xxx in the To text box. Mechanica duplicates a copy of the material xxx and places it in the Materials In Model list with the name of xxx. If the name is too long, the software issues a warning. The copy will exist in the model file but not be assigned until you assign the material to a geometric entity. Delete a Material Click Delete on the Materials dialog box to delete an assigned or unassigned material from the Materials in Model list, provided that material is not assigned to a shell or beam. You cannot delete any of the materials in the Materials in Library list. If you did not previously assign the material to an entity, Mechanica deletes the material from the model database. If you assigned the material to an entity, the software first asks whether you want to delete the material. Click one of the following buttons: • • No — to retain the material Yes — to delete the material. Mechanica deletes the material from your model and the model database. To Delete a Material 1. Select Properties>Materials or click . In the FEM mode, also select Whole Part on the FEM MATERIAL menu. The Materials dialog box appears. 2. Select a material from the Materials in Model list. The material you select must be a user-created material rather than one of the standard materials in Mechanica's material library. 3. Click Delete. If you did not previously assign the material to an entity, the material is deleted from the model database. 4. When you assign the material to an entity, the software asks whether you want to delete it. Click one of the following buttons: o No — to retain the material o Yes — to delete the material. The material is deleted from the model. As a quick alternative to this procedure, you can select the material you want to delete from the model tree. Right-click on the material and select the Delete command from the object action menu. 301 Structural and Thermal Simulation - Help Topic Collection Unassign a Material To Unassign a Material in FEM Mode 1. Select Properties>Materials or click The FEM MATERIAL menu appears. 2. Select Unassign. The software prompts you to select an object type from which to unassign a material. 3. Select an object type from the FEM MATERIAL menu. 4. Select an entity or entities from which to delete an assigned material. The software asks if you want to remove the reference to the material. 5. Click Yes to remove the reference to the material or No to retain the reference to the material in your model. If you want to unassign a material from a solid chunk, there is a quick alternative to this procedure. Select the material assignment you want to remove from the model tree. Right-click on the material assignment and select the Delete command from the object action menu. . Unassign a Material in FEM Mode Click Properties>Materials. When the FEM MATERIAL menu appears, select Unassign and select the object type from which you want to unassign the material, as follows: • • • Whole Part — Enables you to unassign a material from the whole part. Solid Chunk — Enables you to unassign a material from the solid area defined by the surface you select. Shell Pair — Enables you to unassign a material from a shell pair. After you select an object type, select an entity from which to delete a material. After you select an entity, the software asks if you want to remove the reference to the material. Click Yes to remove the reference to the material or No to retain the reference to the material in your model. 302 Structural and Thermal Simulation To Assign a Mechanica Material in Pro/ENGINEER This procedure assumes you have a part file open in Mechanica. 1. Select Properties>Materials. The Materials dialog box appears. 2. Highlight one of the material names in the Materials in Library or Materials in Model list. 3. Click Assign and select Part from the menu. 4. Use the normal selection methods to select a part on your model. The material name appears in the Materials in Model list. 5. Select Close. 6. Select Applications>Standard to return to Pro/ENGINEER. 7. Select Edit>Setup>Material>Assign. 8. Select From Part, and highlight the material you assigned in Mechanica. 9. Select Accept to assign the material to the part. To Create an Orientation for Parts, Solids, Volumes Follow the steps below to complete defining a material orientation for a part, solid, or volume. 1. Enter a name for the material orientation or use the default name provided. 2. Optionally, enter a description. 3. Accept the default WCS or use the selector arrow to specify a coordinate system to which the principal material directions are relative. 4. For Material Directions 1, 2, and 3, you specify any of these values: o the axes of the current coordinate system o one of the solid directions 5. If you want to apply an additional rotation about one or more material directions, select Additional Rotation About. 6. If you want to see what your model looks like with this material orientation even though it is not assigned, perform the following steps: o Click Preview. o Mechanica prompts you to select an entity of the type you selected above. o Select one or more entities. The software highlights the selected entity. Note: The new orientation is not assigned to your model until you explicitly assign it to a geometric entity. 7. Click OK. The new material orientation appears on the Material Orientations list. 303 Structural and Thermal Simulation - Help Topic Collection To Create an Orientation for Surfaces Follow the steps below to complete defining a material orientation for a surfaces. In creating material orientations for a surface, you may, in effect, be creating the material orientation for a shell, 2D plate, or 2D solid, depending on how you have idealized your model. 1. Enter a name for the material orientation, or use the default name provided. 2. Optionally, enter a description. 3. Specify what the material orientation is to be relative to: o Referenced Coordinate System — Use the selector arrow to specify a coordinate system to which the principal material directions are relative. Mechanica displays the Material Direction 1 menu, which lets you select either Projected x axis or Projected "closest" axis. Projected x axis is the default value. In the FEM mode, to specify what the material orientation is relative to, you can select Referenced Coordinate System and Projected x axis only. The other options are unavailable. First Parametric Direction — Specifies that the orientation is relative to the first parametric direction. o Second Parametric Direction — Specifies that the orientation is relative to the second parametric direction. o Projected Vector — Select either Vector Components or Two Points. If you select Vector Components, you need to specify the WCS components of the projected vector. If you select Two Points, you need to select two points on the model that determine the vector. 4. If you want to apply an additional rotation about one or more material directions, select Additional Rotation About. Additional rotations are not available in the FEM mode. 5. If you want to see what your model looks like with this material orientation even though it is not yet assigned, perform the following steps: o Click Preview. o Mechanica prompts you to select an entity of the type you selected above. o Select one or more entities. The software highlights the selected entity. Note: The new orientation is not assigned to your model until you explicitly assign it to a geometric entity. 6. Click OK. The new material orientation appears on the Material Orientations list. o 304 Structural and Thermal Simulation To Assign Fatigue Properties to Materials 1. Select Properties>Materials or click The Materials dialog box appears. 2. Click New. The Material Definition dialog box appears. 3. Select the Structural tab. 4. Verify that Isotropic is selected for the material type. You can use only isotropic materials for fatigue analysis. 5. Select the Fatigue tab. 6. Enter a value for Ultimate Tensile Strength (UTS). 7. If you want to change the units for UTS, select the units from the list to the right. 8. Select a Material Type. 9. Select a Surface Finish. 10. Enter a value for Fatigue Strength Reduction Factor (Kf). . Material Orientation About Material Orientation Use the Properties>Material Orientations command to specify material orientation for surfaces and volumes of 2D or 3D models. Mechanica uses these properties to determine the material directions of orthotropic or transversely isotropic material properties you assign to these entities. You may also view certain results, such as stress, displacement, flux, and others, relative to the material orientation of the elements associated with these entities. If you are working with a single part, Mechanica defines the material orientation for that part. If your model is an assembly, Mechanica enables you to define material orientation for each of the parts that make up the assembly. When you select Properties>Material Orientations, the Material Orientations dialog box appears. To learn more about using material orientation, see: • • Guidelines for Material Orientation Default Material Orientation 305 Structural and Thermal Simulation - Help Topic Collection Default Material Orientation If you do not specify a material orientation, Mechanica assumes the following: • • For all entities, except for surfaces of 3D models and shells, the principal material directions are aligned with the WCS axes. For surfaces of 3D models and shells, the principal material directions are defined by the parameterization of the surface, and that: o Material direction 1 is parallel to the first parametric curve of the surface. o Material direction 2 is set perpendicular to directions 1 and 3. o Material direction 3 is perpendicular to the surface and aligned with the surface normal. For information about surface normals, see Surface Normals. Guidelines for Material Orientation Be aware of the points discussed here when assigning material orientation. • • • • • • • • • The two types of material orientation are: o 2D — use for surfaces and shells o 3D — use for parts, volumes, and solids Material orientation is associated with an entity, not with a material. The material directions 1, 2, and 3 defined by the material orientation correspond to the directions listed on the Material Definition dialog box when you enter orthotropic or transversely isotropic material properties. If you assign a transversely isotropic or an orthotropic material to your model, you must specify the material's orientation or be aware of the default behavior. If you do not specify material orientation, Mechanica assumes the default material orientation. If you delete an orientation, you set the entity back to its default. You cannot assign material orientation properties to curves, beams, or 2D shells. In the FEM mode, you cannot define material orientations that reference cylindrical or spherical coordinate systems. In the native mode, if you define a material orientation with a cylindrical or spherical coordinate system as a reference, the origin of that coordinate system must not lie on the entity to which you assign the material orientation. Material orientation is defined in 3D for both 2D and 3D model types. If you assign a material orientation to a part and that part gets compressed to a surface, the definition of the material orientation changes from one defined over a part to one defined over a surface. The material orientation applies to all the surfaces that Mechanica creates when it compresses the part. You cannot assign a material orientation to a surface that has a shell associated with it. You can define any number of material orientations for a model without assigning them. • • • • 306 Structural and Thermal Simulation Material Orientations Dialog Box Use this dialog box to: • • • assign material orientations to your model create, copy, or edit material orientations for your model delete material orientations from your model The Material Orientations dialog box lists all material orientations that you have defined. You can define as many material orientations as you want without assigning them. When you select one of the listed material orientations, the entities to which that orientation is assigned are highlighted and a material orientation icon appears for each of those entities. The icon has 3 axes and is labeled for the material directions 1, 2, and 3. The type of entities to which you can assign a material orientation depends on: • • the current model type the type of material orientation that you selected The following commands appear on the Material Orientations dialog box: • • • • • Assign New py Edit Delete If a description was entered for a selected material orientation, it appears below the list of material orientations. Assign a Material Orientation Click Assign on the Material Orientations dialog box to assign a material orientation to one or more entities. The type of entity you can select on your model depends on the mode, model type, and the type of material orientation selected. Select a material orientation from the list on the Material Orientations dialog box. The software highlights all the entities to which that material orientation is assigned and displays the material direction icons for that material orientation. Click Assign and use the normal selection methods to select one or more entities. The software highlights any entity you select. After you confirm your choice, the Material Orientations dialog box reappears. The software adds all the material orientation icons for the type of entity you selected to the model. 307 Structural and Thermal Simulation - Help Topic Collection If you have previously assigned a material orientation to any of the selected entities, Mechanica gives you the opportunity to retain the existing orientation or to change it. Click Yes to change the orientation or No to retain the existing one. To Assign a Material Orientation 1. Select Properties>Material Orientations. The Material Orientations dialog box appears. 2. Select a material orientation from displayed list. 3. Click Assign. Mechanica prompts you to select an entity. 4. Use the normal selection methods to select one or more entities on your model. If you are working with an assembly and you select a 3D-type material orientation, you can select a specific subassembly or the entire assembly on the Model Tree or on the model. In this case, Mechanica assigns the material orientation to all parts, datum, geometry, edges, and surfaces in the selected assembly or subassembly. 5. The software highlights the entity you select. (If you have previously assigned a material orientation to any of the entities you select, Mechanica gives you the opportunity to retain the existing orientation or to change it.) 6. Confirm your selection. The Material Orientations dialog box reappears. Create a Material Orientation Click New on the Material Orientations dialog box to define a material orientation. You select an entity type to which you will later assign the material orientation. In the case of 2D model types or in FEM mode, no option menu appears because using surfaces is the only option. The type of entities that you can select on the option menu depends on: • • the mode (native or FEM) the model type You can select the following types of entity: Mode Native Model Type 3D Entity Type Part Surface Surface Surface Native FEM 2D 3D 308 Structural and Thermal Simulation When you select an entity type, the Material Orientation Definition dialog box appears. Enter values in the dialog box fields to define a new material orientation. After you click OK, the new material orientation appears on the Material Orientations dialog box. The new orientation is not assigned to your model until you assign it to a geometric entity. Material Orientation Definition Dialog Box Use this dialog box to define values for a material orientation. The items on the dialog box vary depending on the model type and the type of entity. Enter the material orientation name and an optional description, as well as other information. The information you enter depends on the entity involved. • • Parts and volumes Surfaces Be aware that when you create material orientations for a surface, you may, in effect, be creating the material orientation for a shell, 2D plate, or 2D solid, depending on how you have idealized your model. If a material orientation is not assigned, the Preview button enables you to select a surface or solid to view the material orientation icon as if the orientation were assigned. Part When you select Part or Volume, Mechanica asks you to select the part or volume you want, and then displays a dialog box. On this dialog box, you can specify: • • Relative To — Specifies the reference coordinate system for the principal material directions. Material Direction — Specifies the material direction. This area includes: o Material Direction grid — Use the buttons in this grid to select the alignment axis for material directions 1, 2, and 3. o Rotate About — Specifies additional rotations about one or more material directions. Material Orientation Definition for Surfaces To define the material orientation for surfaces, specify the following items. Note that, in creating material orientations for a surface, you may, in effect, be creating the material orientation for a shell, 2D plate, or 2D solid, depending on how you have idealized your model. 309 Structural and Thermal Simulation - Help Topic Collection • • Relative To — Specifies the references for the principal material directions. You can specify: o Referenced Coordinate System — Mechanica uses the selected coordinate system to determine the material directions. This option is available in both native mode and FEM mode. o First Parametric Direction — When you select this option, you are defining material direction 1 to be the same as the first parametric direction of the surface, which can vary from point to point on the surface. Material direction 3 is always normal to the surface, and material direction 2 is defined to be normal to material directions 1 and 3. Mechanica does not support this option in FEM mode. o Second Parametric Direction — When you select this option, you are defining material direction 1 to be the same as the second parametric direction of the surface, which can vary from point to point on the surface. Material direction 3 is always normal to the surface, and material direction 2 is defined to be normal to material directions 1 and 3. Mechanica does not support this option in FEM mode. o Projected Vector — Mechanica requires the vector's start and end points or the vector's components, and performs a normal projection. Mechanica does not support this option in FEM mode. Rotate About — Specifies additional rotations about the normal to the surface, or the material direction normal to the surface. Mechanica does not support this option in FEM mode. For examples of material orientation on surfaces, see: • • • • Example: Example: Example: Example: Curved Surface Directions 2D Surface Directions Variable Material Orientation Rotation for Shells and Surfaces To Create a Material Orientation 1. Select Properties>Material Orientations. The Material Orientations dialog box appears. 2. Click New. In the native mode, a drop-down menu appears. In the FEM mode, the Material Orientation Definition dialog box appears. 3. In the native mode, select Part or Surface, depending on whether the orientation is for the whole part or for an individual surface. The Material Orientation Definition dialog box appears. The next steps depend on whether you are creating an orientation for a part, solid, or volume, or for a surface, shell, 2D plate, or 2D solid. 310 Structural and Thermal Simulation Edit a Material Orientation Click Edit on the Material Orientations dialog box to edit a material orientation. The Material Orientation Definition dialog box appears. Change the fields on the dialog box to the values you want for your material orientation. By editing a material orientation, you change the orientation on all of the geometric entities to which it was assigned. To Edit a Material Orientation The changes you make affect all the entities to which the material orientation was assigned. 1. Select Properties>Material Orientations. The Material Orientations dialog box appears. 2. Click Edit. The Material Orientation Definition dialog box appears. 3. Change the fields on the dialog box to the values you want for your material orientation. Copy a Material Orientation Click Copy on the Material Orientations dialog box to duplicate a selected material orientation from the Material Orientations list. Note that the copy is not assigned to an entity until you explicitly assign it. To Copy a Material Orientation 1. Select Properties>Material Orientations. The Material Orientations dialog box appears. 2. Select a material orientation from displayed list. 3. Click Copy. 4. If desired, edit the copy to differentiate it from the original material orientation. Mechanica does not assign the copy to a geometric entity until you explicitly assign it. 311 Structural and Thermal Simulation - Help Topic Collection Delete a Material Orientation Click Delete on the Material Orientations dialog box to delete a selected material orientation from those listed on the Material Orientations dialog box. If you have assigned the orientation to one or more entities, the software asks whether you want to delete it. Click No to retain the previously assigned orientation. Click Yes to delete the orientation from all of the entities to which it is assigned. To Delete a Material Orientation 1. Select Properties>Material Orientations. The Material Orientations dialog box appears. 2. Click Delete. If you have assigned the orientation to one or more entities, the software asks whether you want to delete it. 3. Click No to retain the previously assigned orientation. Click Yes to delete the orientation from all of the entities to which it is assigned. Reentrant Corners This option enables AutoGEM to detect reentrant (for example, inside) corners on an individual surface in your model and place a transitional set of small elements around them. A reentrant corner can be an area of high stress or flux concentration. Placing small elements around reentrant corners helps prevent these stress or flux concentrations near the local feature from degrading the efficiency of the analysis process in larger neighboring elements. For an example of how this AutoGEM feature works, see Example: Reentrant Corners. AutoGEM does not detect reentrant corners that span more than one surface. AutoGEM also does not detect reentrant corners on volumes. This item appears on both the Structure and Thermal versions of the dialog box, and works the same way in either mode. Display AutoGEM Messages Select this option on the Settings tab if you want AutoGEM to display the messages and dialog boxes that it generates during an AutoGEM session. You should deselect Display AutoGEM Messages if you cannot be at your computer to monitor the AutoGEM process. However, the suppressed messages and message boxes are recorded in the AutoGEM log file. 312 Structural and Thermal Simulation If you deselect this item, AutoGEM does not display messages and message boxes. Instead, it automatically selects the default response for each one and continues creating elements. If it encounters a problem, AutoGEM first displays a message directing you to the AutoGEM log file and then displays the AutoGEM Summary dialog box. Creating You can override the default limits for creating elements when your model contains angles constrained by geometry to less than the angles allowed on the dialog box. Online help uses the term geometry-constrained to refer to such elements. For example, the angle in the following geometry-constrained element is smaller than the limit of 5 on the dialog box: Example: Brick A brick (or hexahedron) has six quadrilateral faces, twelve edges, and eight points: Boundary Processing Takes Too Long If the boundary processing stage seems to be taking too long (it can take over 10 minutes for very complex parts), you can do try the following techniques: • • • • Deselect all the items under Feature Isolation area on the AutoGEM Settings dialog box. This disables any mesh refinement that AutoGEM would normally use to isolate problem features. Use AutoGEM on all surfaces that form the volume boundary. Use box selection to select all of the boundary surfaces at the same time. Let AutoGEM run at least a few minutes after seeing the Creating <element type> elements status message. Interrupt AutoGEM when it reaches the maximum percentage completion or when the element count starts to increase rapidly. After you interrupt, use the Boundary Edges option on the AutoGEM Info menu to find incomplete 313 Structural and Thermal Simulation - Help Topic Collection • areas. Additionally, look for areas with too many points. This should help you find the problem areas on the volume boundary. Modify the geometry in the problems area. For example, if the problem occurs near a round, try altering the radius of the round. Automatic Interrupt Select this option on the Settings tab if you want AutoGEM to automatically stop when it has created a specified percentage of elements. If you select this item, Mechanica displays an additional line on the AutoGEM Settings dialog box where you enter the percentage of completion at which you want Mechanica to stop AutoGEM. Automatic Interrupt is useful when you know from previously using AutoGEM on your model that you will encounter swap space or AutoGEM problems if you allow AutoGEM to continue. You can use the AutoGEM log file to determine the point at which you should interrupt the AutoGEM process. Max Aspect Ratio This option enables you to enter the maximum aspect ratio that you want AutoGEM to allow when it creates or edits elements. We recommend that you keep the default value for this field and address your element count through the Allowable Angles field instead. If you lower the Max Aspect Ratio setting, you may experience slower performance and AutoGEM may create inappropriate element concentrations. The Mechanica guideline is that the aspect ratio of a solid face's length to its width and a shell's length to its width should be no greater than 30 to 1. The guideline for 2D plates and 2D solids is the same as for shells. The default aspect ratio for creating is 30; the minimum value is 2. You should not use an aspect ratio higher than 30 for areas of your model that have high stress or flux gradients, or for areas of your model where you are especially interested in the results. The default aspect ratio for editing is 100. 314 Structural and Thermal Simulation Allowable Edge and Face Angles The following diagram illustrates edge and face angles: The following table shows the valid minimum angles and the defaults for edges and faces during creation and editing (all angles are in degrees): Minimum Angles Defaults Entity Edge Face Valid Range 0 to 30 0 to 30 Creating 5 5 Editing 1 1 The following table shows the valid maximum angles and the defaults for edges and faces during creation and editing (all angles are in degrees): Maximum Angles Defaults Entity Edge Face Valid Range 150 to 179 150 to 179 Creating 175 175 Editing 179 179 These settings control the minimum and maximum angles that AutoGEM uses. 315 Structural and Thermal Simulation - Help Topic Collection AutoGEM Overconstrained We recommend that you run AutoGEM against all of the surfaces and volumes in your model at the same time. This approach assures a cohesive mesh. However, if you mesh your model in stages, selecting volumes one or two at a time, examine the volume interfaces before you start. Be sure to use AutoGEM on the volume that includes the smallest features near the interface before you use it on the volumes with larger features. This is because, after you use AutoGEM on one of the volumes in a model, the element faces on that volume become constraints that AutoGEM must respect while processing other adjacent volumes. If you start with volumes that have larger features near the interface, the existing large elements at the volume interface may overconstrain AutoGEM when you then try to mesh adjacent volumes with smaller features. You can correct this situation through the AutoGEM Settings dialog box. In this case, you select Modify Or Delete Existing Elements and select the volume filled with elements as well as the unfilled volume. AutoGEM then completes the unfilled volume and modifies the existing elements in the filled volume as required. Required Modeling Entities If you plan to mesh your model with AutoGEM before running an analysis or design study, you should follow a few common sense practices to ensure that all modeling entities are correctly accounted for in the mesh. In some cases, you must add the modeling entity before you mesh, while, in others, you can add the entity later. Here are the guidelines you should follow: • Entities you must add before using AutoGEM — You must add idealizations, connections, and simulation features that you want to use as a basis for another modeling entity—for example, a datum point that will be used to apply a measure—before running AutoGEM. Additionally, if your model includes point loads, constraints, or boundary conditions, you must add them as well. All of these modeling entities influence the mesh. If you do not add them before using AutoGEM, the mesh will not correctly account for these entities. While it may not be absolutely necessary in all cases, we strongly recommend that you also define all properties before running AutoGEM. Defining properties before you run AutoGEM enables you to use the All With Properties option in the AutoGEM References area of the AutoGEM dialog box. • Entities you can add before or after using AutoGEM — Provided all reference simulation features and geometry are in place before you run AutoGEM, you can add loads, constraints, and boundary conditions before or after using AutoGEM. These entities must use curves, surfaces, or 316 Structural and Thermal Simulation components as references; they should not use points. Also, you can add measures before or after you run AutoGEM. While Mechanica correctly accounts for modeling entities that you add to geometry after you run AutoGEM, it is a good practice to add all modeling entities prior to meshing the model. Create Links Where Needed Select this option on the Settings tab if you want AutoGEM to create links where needed to continue creating elements on volumes. If you select Create Links Where Needed, AutoGEM links tetrahedrons to existing wedge and brick quad faces. Mechanica does not create links to existing quad shell elements. In general, you should select Create Links Where Needed if you have existing wedge or brick elements in your model. Adding links may increase run time. AutoGEM Interruption Guidelines In determining whether to interrupt AutoGEM, you should evaluate changes in the completion percentage. If the completion percentage in the status messages fluctuates by less than 10%, you should try to avoid interrupting. But if the completion percentage drops by 10% to 15% or more, that may be a sign that AutoGEM has encountered problems and will not be able to complete. You should then interrupt and investigate areas of your model where AutoGEM did not create elements. Suppressing unnecessary geometry features or modifying model dimensions can sometimes result in cleaner geometry with a better mesh success rate. Detailed Fillet Modeling Select this option on the Settings tab if you want AutoGEM to create a greater number of elements near fillets. In many cases, selecting Detailed Fillet Modeling yields smoother fringe plots for fillets. If you want even smoother fringe plots, you can add extra points to your fillets before using AutoGEM. For this type of modeling, be sure to deselect Move Or Delete Existing Points. Otherwise, AutoGEM removes all points that it considers unnecessary. Depending on the situation, the points AutoGEM removes may include the points you added. 317 Structural and Thermal Simulation - Help Topic Collection Minimum and Maximum Angles The angle between any two adjacent element edges or faces must be equal to or greater than 0 and less than 179 , unless they are geometry-constrained angles. When AutoGEM is creating elements, edge and face angles should be between 5 and 175 . Angles less than 5 or greater than 175 can affect run time and results. For some models, angles less than 5 and greater than 175 may be useful for the following purposes: • • • creating elements in a difficult area decreasing the total number of elements helping AutoGEM to finish creating elements When you first switch from creating to editing mode, Mechanica checks that the creation edge and face angles are between 5 and 175 and warns you if the angles are not in this range. Select Accept to keep the values you selected for the angles. Select Cancel to change the creation limits back to the previous limits. Create a Full Set of Elements Try one or more of the following steps: • • • • Use the Boundary Faces command on the AutoGEM Info menu to find and examine unfinished areas of the model. If AutoGEM creates an incomplete set of elements, you can try adding points along curves and surfaces. Then, delete the existing mesh and run AutoGEM again. If the volume contains a small feature close to a large feature, you can try adding points to the large feature. Reduce the minimum edge and face angles, increase the maximum edge and face angles, or increase the aspect ratio on the Limits tab on the AutoGEM Settings dialog box. Try this strategy only when other strategies have failed or when your model has some very thin surfaces. Review the AutoGEM log file to determine what percentage of elements AutoGEM completed. Select the Automatic Interrupt option on the AutoGEM Settings dialog box, and enter the completion percentage at which you want to interrupt AutoGEM. After AutoGEM interrupts itself, add points in the incomplete region. After you have taken one or more of these steps, you can run AutoGEM again. You can do either of the following: o o Keep the elements AutoGEM created the first time Delete some or all of the elements before using AutoGEM a second time • 318 Structural and Thermal Simulation If you restart AutoGEM on a volume that is partially filled with tetrahedral elements, it is usually best to select Modify Or Delete Existing Elements on the AutoGEM Settings dialog box. Shell , 2D Plate Element Type, 2D Solid Element Type The name of this option varies according to your model type. Select one of the following items from this option menu: • • Quad and Tri — AutoGEM creates a combination of quadrilateral and triangular elements when you create elements using the Surface menu option. For most models, this is the best choice. Tri — AutoGEM creates only triangular elements when you create elements using the Surface menu option. Select this option if you want shells that are compatible with the tetrahedral solids that the Volume menu option creates. Solids This option enables AutoGEM to create different types of solids after you select one of the following options: • • Tetra — Creates a purely tetrahedral mesh. This option is ideal for irregular, chunky models where none of the other solid element types would be appropriate. Wedge, Tetra — Creates a mesh that may include tetrahedra, wedges, or both, based on model geometry. Use this option for models that are at least partially composed of thin sections (2.5D) with opposing surfaces. AutoGEM selects the element type that works best in each area of your model, and finds the most efficient mesh for the geometry. The result will be that the thin areas of the model will contain wedges and the thick areas will contain tetrahedra. If you use this option instead of the Tetra option, your element count may be significantly lower and your solution times, faster. Brick, Wedge, Tetra — Creates a mesh that may include tetrahedra, wedges, bricks, or any combination of these element types, based on model geometry. Use this option for models that are at least partially composed of thin sections (2.5D) with opposing surfaces. AutoGEM selects the element type that works best in each area of your model, and finds the most efficient mesh for the geometry. The result will be that the thin areas of the model will contain wedges or bricks and the thick areas will contain tetrahedra. If you use this option instead of the Tetra or Wedge, Tetra options, you may be able to minimize the number of elements in your model and achieve faster solution times. • 319 Structural and Thermal Simulation - Help Topic Collection Invalid Curves for 2D Axisymmetric Models When you model shells for 2D axisymmetric models, Mechanica assumes that you intend the curves you select to be treated as though they revolve about the Y axis of your reference coordinate system. For this type of modeling to be valid, the curves must satisfy certain criteria. For example, no curve can cross or lie on the Y axis. To ensure this, Mechanica enforces a rule that all model geometry must lie in the positive X direction relative to your reference coordinate system. The following illustration shows curve selections that are invalid for 2D axisymmetric models: When you define your model as a 2D axisymmetric model, Mechanica checks for curves that break the first two rules. If it finds any problems of this sort, Mechanica displays a warning box indicating that it cannot change the model type because the geometry does not lie in the positive X direction relative to the reference coordinate system. If it encounters a curve that breaks the third rule—coincidence with the Y axis— Mechanica allows the model, but any analyses you attempt to run may fail. 320 Structural and Thermal Simulation Example: Wedge A wedge (or pentahedron) has two triangular faces, three quadrilateral faces, nine edges, and six points: Example: Point Loads The Structure model shown below has one surface and a load at one corner: 321 Structural and Thermal Simulation - Help Topic Collection If you deselect the Point Loads option on the AutoGEM Settings dialog box, AutoGEM creates eight shells. The display of surfaces is turned off so you can clearly see the shells: If you select the Point Loads option, AutoGEM creates an additional small element to isolate that point. Again, the display of surfaces is turned off: 322 Structural and Thermal Simulation Max Edge Turn (Degrees) This option enables you to enter the maximum subtended edge angle that you want AutoGEM to use when it creates or edits elements. During element creation, the value of this item cannot exceed 100 . The default for creating elements is 95 . The default limit for editing is 100 . You cannot exceed the editing limit. If you enter a value for the edge angle that is not within the range allowed for that mode, Mechanica prompts you to reenter a value within the proper range. Validate Click this button on the Limits tab if you want AutoGEM to verify that all elements meet the limits. If all elements satisfy the limits, a message box states that all elements satisfy the limits for creating or editing. If there are elements that do not satisfy the limits on this dialog box, Mechanica highlights all the elements that do not satisfy the currently displayed limits. A message box asks if you want to create a new group and add the highlighted entities to this group. Example: Tetra A tetra (or tetrahedron) has four triangular faces, six edges, and four points: Invalid Surfaces for 2D Axisymmetric Models When you model solids for 2D axisymmetric models, Mechanica assumes that you intend the surfaces you select to be treated as though they revolve about the Y axis of your reference coordinate system. For this type of modeling to be valid, the surfaces must satisfy certain criteria. For example, no surface can cross or lie on the 323 Structural and Thermal Simulation - Help Topic Collection Y axis. To ensure this, Mechanica enforces a rule that all model geometry must lie in the positive X direction relative to your reference coordinate system. The following illustration shows surface selections that are invalid for 2D axisymmetric models: When you define your model as a 2D axisymmetric model, Mechanica checks for surfaces that break these rules. If it finds any problems of this sort, Mechanica displays a warning box indicating that it cannot change the model type because the geometry does not lie in the positive X direction relative to the reference coordinate system. Modify or Delete Existing Elements Select this option on the Settings tab if you want AutoGEM to modify or delete existing elements as required. AutoGEM does not modify or delete existing wedge or brick solids. AutoGEM sometimes cannot create a full set of elements on a surface or volume having complex features. If you select Modify Or Delete Existing Elements, AutoGEM is more likely to fully cover each surface or volume with elements. In general, you should select Modify Or Delete Existing Elements. If you want to keep any existing elements, you should deselect this check button. Point Loads, Point Constraints, Point Heat Loads, Point Prescribed Temperatures, Point Convection Conditions Selecting these options enables AutoGEM to place small transitional elements around: • • point loads or constraints in your Structure model heat loads, prescribed temperatures, or convection conditions in your Thermal model 324 Structural and Thermal Simulation Any of these point-based modeling entities could distort the results in elements adjacent to the point by introducing singularities—areas of theoretically infinite stress for Structure or infinite flux for Thermal. Thus, whenever possible, you should apply loads and constraints to curves and surfaces, not points. If you must apply the load, constraint, or boundary condition to a point instead of a curve or surface, you can use the check boxes in the Feature Isolation area on the AutoGEM Settings dialog box to mitigate the effects of the singularity on your results. This enables AutoGEM to create small transitional elements around the singularity, lessening the stress or flux concentration. To take advantage of feature isolation for point loads, constraints, and boundary conditions, you should create these entities on your geometry before using AutoGEM to mesh the model. As a general rule, you should keep these items selected for all models. For an example of how this feature works, see Example: Point Loads Move or Delete Existing Points Select this option on the Settings tab if you want AutoGEM to move or delete existing points as required. AutoGEM sometimes cannot create a full set of elements on a surface or volume having complex features. If you select Move Or Delete Existing Points, AutoGEM is more likely to fully cover the surface or volume with elements. In general, you should select Move Or Delete Existing Points. AutoGEM moves or deletes a point only if the point meets the following conditions: • • • The point is associated with a single curve, a single surface, or both a curve and surface associated with each other. The point is not associated with model entities such as loads, measures, or material properties. The point is not a user-created datum point. 325 Structural and Thermal Simulation - Help Topic Collection Example: Insert Points The model contains one surface and several small features, which complicates element creation. The model is shown before creating any elements: If you turn off Insert Points, AutoGEM is unable to create a full set of elements on the surface. The display of surfaces is turned off so you can clearly see the shells: 326 Structural and Thermal Simulation If you turn on Insert Points, AutoGEM adds the points it needs to finish creating elements, as shown below. Again, the display of surfaces is turned off: Insert Points Select this option on the Settings tab if you want AutoGEM to add extra points when needed to help create elements in complex areas of your model. If you select Insert Points, AutoGEM may add the following types of points: • • Boundary points — points on surface boundary curves in addition to those it adds to create valid element edges. Interior points — points on surfaces and inside volumes. These points are in addition to those points that AutoGEM adds to create valid element edges between existing points. AutoGEM sometimes cannot create a full set of elements on a surface or volume having complex features. If Insert Points is selected, AutoGEM is more likely to fully cover each surface or volume with elements. Note: You can also choose to add points manually to guide AutoGEM through complex areas of your model. For an example of a model for which Insert Points enables AutoGEM to create a full set of elements, see Example: Insert Points. 327 Structural and Thermal Simulation - Help Topic Collection Example: Reentrant Corners A model with a single surface and two reentrant corners is shown below: If you turn off Reentrant Corners, AutoGEM creates four shell elements. The display of surfaces is turned off so you can clearly see the shells: 328 Structural and Thermal Simulation If you turn on Reentrant Corners, AutoGEM creates 11 elements, including several small elements around the reentrant corners, as shown below. Again, the display of surfaces is turned off: The reentrant corners have a total of seven small elements. The reentrant corner shown below has three: Fatigue Properties The following options for material properties appear on the Fatigue tab on the Material Definition dialog box: • • • Ultimate Tensile Strength — Enter a value between 50 MPa and 4000 MPa. Material Type — Select an option for the type of material you are using: Unalloyed steels, Low Alloy steels, Aluminum alloys, Titanium alloys, or None. Surface Finish — Select an option for the surface finish of your model: o Polished o Ground o Good Machined o Average Machined o Poor Machined o Hot Rolled 329 Structural and Thermal Simulation - Help Topic Collection o Forged o Cast o Water Corroded o Seawater Corroded o Nitrided o Shot Peened o Cold Rolled Fatigue Strength Reduction Factor — Enter a fatigue strength reduction factor (Kf) greater than 1. This factor is used to reduce the endurance limit to account for unmodeled stress concentrations, such as those found in welds. • Thermal Values for Orthotropic Properties In Thermal, enter values for the following orthotropic properties. • • Specific Heat — Enter a positive value for the material's specific heat. Thermal Conductivity — Enter positive values for the following aspects of the material's conductivity: o k1 o k2 o k3 These values represent the conductivity in each of the three principal material directions of the model. To specify thermal conductivity, you can type in a value or click the P button to assign a parameter name. Shear Modulus Enter positive values for the shear moduli of the material. You can define this property or you can assign a parameter to the property. Type in a value or click the P button as appropriate. For orthotropic material properties, enter values for: • • • G12 G13 G23 These values represent the shear modulus in each of the three material directions. For transversely isotropic material properties, enter a value for the shear modulus of the material in two of the three principal planes of the material for the model. The dialog box shows the following shear modulus values: • • G12 = G13 G23 = E2/(2 X (1 + Nu32)) 330 Structural and Thermal Simulation Enter a single positive value for the 21 and 31 planes. Structure automatically calculates the value for the 32 plane, using the equation shown on the dialog box. Note: For both orthotropic and transversely isotropic, G21 is also denoted as G12, G31 as G13, and G32 as G23. Projected Vector When you select Projected Vector from the Relative To option menu, Mechanica displays a second option menu with the following items: • • Vector Components — Enter the values for the WCS X, Y, and Z components to define the vector to which the material orientation will be relative. Two Points — Click the following buttons to define the vector to which the material orientation will be relative: o o From — specifies the start point of the vector To — specifies the end point of the vector For more information on how Mechanica projects a vector onto a surface, see Example: Project a Vector onto a Surface. Poisson's Ratio Enter values for Poisson's Ratio, the ratio of lateral contraction to longitudinal extension for a bar in tension. You can define this property or you can assign a parameter to the property. Type in a value or click the P button as appropriate. For orthotropic material properties, enter values for: • • • Nu21 Nu31 Nu32 For transversely isotropic material properties, enter values for: • • Nu21 = Nu31 Nu32 There are two widely used, but conflicting, definitions of Poisson's ratios for anisotropic materials. Mechanica uses the definition described by Tsai in Composite Design. For more information, see Tsai Definition for Poisson's Ratios. You can change the labels for Poisson's ratios on the orthotropic and transversely isotropic tabs of the Material Definitions dialog box. In the config.pro file, if the default for the sim_mat_poissons_notation is set to the default value, TSAI, the labels are Nu21, Nu31, and Nu32. When it is set to JONES, the labels are Nu12, Nu13, and Nu23, respectively. 331 Structural and Thermal Simulation - Help Topic Collection Parameter-Capable Edit Fields You can use Pro/ENGINEER parameters in arithmetic expressions that define thickness and orientation for your laminate-layup shell properties. When you move your cursor into one of the rows under Thickness or Orientation on the laminate-layup version of the Shell Property Definition dialog box, the cursor changes to this form: When you right-click, a menu appears with the following items: • Parameter — Display the Select Pro/ENGINEER Parameter dialog box with a list of existing parameters. You can use this dialog box for the following actions: o Select a parameter from the list and click Accept. The parameter appears in the edit field. You can add text to form an expression. o Click Create. Enter a name and value for the parameter on the Create a Pro/ENGINEER Parameter dialog box. Undo — Reverse the last action. Cut — Remove the highlighted text from the edit field and copy it to the system buffer. Copy — Add text from the edit field to the system buffer to be pasted into another area. Paste — Add text to the edit field from the system buffer. Delete — Remove the selected text from the edit field. Select All — Highlight all the text in the edit field. • • • • • • Order of Rotation Mechanica rotates the material coordinate system in this order: 1. Rotates the material coordinate system about Material Direction 1. 2. Rotates the material coordinate system about the new Material Direction 2 created by the first rotation. 3. Rotates the material coordinate system about the new Material Direction 3 created by the first two rotations. Mechanica uses the right-hand rule to determine the direction of each rotation. 332 Structural and Thermal Simulation Example: Material Directions If you want material direction 1 in the WCS Y direction and material direction 3 essentially unchanged, select the second button in the first row (Material Direction 1). The material directions now appear as they do in the following figure: Material Directions 1, 2, and 3 For material directions 1, 2, and 3, you observe or specify any of these values, depending on the model type and material orientation: • • the axes of the referenced coordinate system one of the solid directions For 3D material orientations, you select one of the following six combinations of the current coordinate system directions for the three principal material directions: Material Direction: Coordinate System Direction or Solid Direction: 1 X 2 Y 3 Z Z Y X Y –Z X Z –Z X Y Y X Y –Z X 333 Structural and Thermal Simulation - Help Topic Collection Mechanica automatically changes the label above the third column of check buttons from Z to –Z when necessary to reflect the fact that the material orientation is righthanded. Note: The material directions 1, 2, and 3 correspond to the directions understood on the Material Properties dialog box when you enter orthotropic or transversely isotropic properties. When you click a Material Direction option button: • • Mechanica redraws the material orientations. The displayed material directions differ depending on the option you select on the Relative To menu. For an example of material directions, see Example: Material Directions. Transversely Isotropic Properties The following items appear on the Properties tab: • • • • Poisson's Ratio Young's Modulus Shear Modulus Coeff. of Thermal Expansion Thermal Values for Transversely Isotropic Properties In Thermal, enter these values for transversely isotropic properties: • • Specific Heat — Enter a positive value for the material's specific heat. Thermal Conductivity — Enter positive values for these two aspects of the material's conductivity: o k1 o k2=k3 These values represent the conductivity in each of the three principal material directions of the model. To specify thermal conductivity, you can type in a value or click the P button to assign a parameter name. 334 Structural and Thermal Simulation Review Stiffness Opens the Laminate Stiffness Review dialog box. You can save the information on the Laminate Stiffness Review dialog box in a text file. Select the File>Save command at the top of the dialog box. In the Save As dialog box, select a directory to save the file. The default is the current working directory. Accept the default name, shellpropname_stiffness.inf, or enter another name. You cannot change the information in any of the fields on the Laminate Stiffness Review dialog box. However, you can select the text in a field and copy it to a clipboard to paste into another application. For example, you can copy the text from one of the fields on this dialog box and then close the box. Create a new laminate stiffness shell property, then click in the field where you want to add the copied information. Right-click and select Paste to add the information from the Laminate Stiffness Review dialog box. For more information about the terms on this dialog box, see Laminate Stiffness. Review Layup Opens the Laminate Layup Review dialog box, which displays all the individual plies of the laminate, with the sub-laminates expanded into individual plies. Mechanica substitutes all the current parameter values and provides the total thickness at the bottom. You can save the information on the Laminate Layup Review dialog box in a text file. Select the File>Save command at the top of the dialog box. In the Save As dialog box, select a directory to save the file. The default is the current working directory. Accept the default name, shellpropname_layup.inf, or enter another name. 335 Structural and Thermal Simulation - Help Topic Collection Material Property Requirements — Failure Criterion The properties below appear depending on which failure criterion you select. Assign these material properties as appropriate: Property tensile yield stress Product Structure Required only for models with a von Mises or Tresca failure criterion only for isotropic materials with a Modified Mohr failure criterion and for transversely isotropic materials with a failure criterion ultimate tensile strength (UTS) Structure ultimate compressive strength Structure only for isotropic materials with a Modified Mohr failure criterion and for transversely isotropic materials with a failure criterion only for transversely isotropic materials with a failure criterion only for transversely isotropic materials with a Tsai-Wu failure criterion shear strength Structure normalized Tsai-Wu interaction term Structure 336 Structural and Thermal Simulation Example: Project a Vector onto a Surface This figure illustrates how Mechanica determines material orientation by projecting a vector onto a surface: Material orientation 3 is defined to be normal to the surface. Material direction 1 is defined to be parallel to the projection of the vector onto the plane tangent to the surface at the point of interest. Material direction 2 is set orthogonal to material directions 1 and 3. Note that the directions of the material orientation vary with position on the surface. Warp & Mass Tab Use the Warp & Mass tab on the Beam Section Definition dialog box to define additional beam values for NASTRAN. This tab is active only in FEM mode, and contains the following items: • Warp Coefficient — Enter the warp coefficient, which is expressed as: units of length6 Use this field for tapered beams only. NASTRAN normally calculates beam sections using equations that assume a beam section is uniform. If you enter a warp coefficient, NASTRAN applies that coefficient as a corrective factor for torsion so that the equations accurately interpret the beam section. • Non-Structural Mass per Unit Length — Enter the non-structural mass per unit length. A non-structural mass is a mass that responds to gravity, but does not strengthen the structure—for example, fluid running in a pipe that you have modeled as a beam. Non-structural masses can have different moments of inertia and gravitational centers than the beam you are creating. Non-Structural Mass Moment per Unit Length — Enter the non-structural mass moment of inertia per unit length. Y Coordinates of Non-Structural Mass C.G. — Enter the Y coordinates of the non-structural mass center of gravity. 337 • • Structural and Thermal Simulation - Help Topic Collection • Z Coordinates of Non-Structural Mass C.G. — Enter the Z coordinates of the non-structural mass center of gravity. Square The icon for a square beam section type looks like this: When you select Square as the beam type on the Beam Section Definition dialog box, you must enter a positive value in the a text-entry box for its cross-section dimension. The figures below illustrate stress recovery points for square beam section types. The figure on the left shows the points for the native mode, and the figure on the right shows the points for the FEM mode. Rotate About This button lets you specify additional rotations about one or more material directions, depending on the model type. These rotation angles enable you to modify the orientation of the material directions from those you specified higher on the dialog box. When you select this check box, additional items appear on your dialog box, depending on the model type and the type of material orientation you have selected: • Surfaces, Shells, 2D Plates, and 2D Solids — Enter an angle from –360º to +360º in the Material Direction Normal To Surface text box or the defined normal material direction. Mechanica rotates the material orientation about the orientation normal to the surface or shell. For an example of this kind of rotation, see Example: Rotation for Shells and Surfaces. 338 Structural and Thermal Simulation • Parts, Volumes, Solids — Enter angles from –360º to +360º in the Material Direction text boxes for one or more of the material directions. Rotations are understood in order about the 1, 2, then 3 material directions. FEM mode does not allow you to have additional rotations. For information about how Mechanica rotates the material coordinate system, see Order of Rotation. Property Type Use these items in the Shell Property Definition dialog box to select the type of shell properties you want to define: • Homogeneous, Laminate Stiffness, Laminate Layup — Select whether you want to define a homogeneous, laminate stiffness, or laminate layup shell property. In the Thermal mode, Laminate Stiffness is unavailable. If your model is 2D, this menu does not appear. You can use either laminate stiffness or laminate layup if you want to model a shell that is comprised of layers, or plies. The laminate stiffness version of the dialog box depends on matrix terms that describe stiffness and bending components for the laminate. The laminate layup version of the dialog box requires material properties, thickness, and orientation for each ply of a laminate, and allows you to review the stiffness components calculated from the ply specification. The items on the remainder of the dialog box are different depending on which property you select. Click the following links for more information: • • • Homogeneous Laminate Stiffness Laminate Layup 339 Structural and Thermal Simulation - Help Topic Collection Example: Applying a Material to a Solid Portion of Your Model In FEM mode, you can use the Solid Chunk option on the FEM MATERIAL menu to assign a material to select solid areas of your model. For example, you can use Solid Chunk to assign a material to a volume region, creating a solid that has two materials, one for the parent solid and one for the solid defined by the volume region, as shown below: In addition, you can use Solid Chunk to apply different materials to solid areas of mixed models provided that the solid areas are isolated through the use of interleaved idealizations, as shown below: When you assign bronze to this model using the Whole Part option, the entire model receives bronze as its material. However, you can override bronze for the solid area on the right side of the model by assigning a different material—in this case, brass—to the surface on the far right side of the model using the Solid Chunk 340 Structural and Thermal Simulation option. The midsurface shell acts a barrier, in effect isolating the solid chunk on the right side of the model. Mechanica applies brass to the right side solid, propagating that material through the tetrahedral mesh until it reaches the bounding midsurface. Note that you could achieve the same effect using the Solid Chunk option for the top, bottom, or left surface (upper or lower) of the right side solid. However, had you selected the front or back surface for the Solid Chunk option, brass would have propagated through both the right and left side solid, leaving the midsurface bronze. Also, had you wanted to assign the midsurface a different material, you could have done so with the Shell Pair option. Tsai Definition for Poisson's Ratios The relation between strains, ( like) is written as follows: , and so forth) and stresses ( , and the Note: The Material Properties dialog box represents as Nu. In the above expression, 1, 2, and 3 denote the three principal material directions. In a uniaxial tension test pulling in the 1 direction, the ratios of transverse normal strains, and , to longitudinal normal strain, , is given by: and 341 Structural and Thermal Simulation - Help Topic Collection Also, since the elasticity matrix is symmetric, the following relation between Poisson's ratios and Young's moduli holds: where i and j take on the values 1, 2, and 3. Therefore, if , then , and . The values you enter for Poisson's ratios must satisfy the requirement that the determinant of the 6 X 6 constitutive equation matrix above is positive. Example: Orienting the BSCS to the BACS After you define the orientation of the BACS relative to the WCS, you can also change the orientation of the BSCS relative to the BACS by using the options on the Beam Orientation Definition dialog box. The figures show the effect of changing the orientation angle, DY and DZ offsets on the Y and Z axes of the BSCS for a square beam section. The X axis, which is along the beam length, extends out of the plane of the image towards the viewer. You can choose to apply DY and DZ offsets while keeping the orientation angle at zero, as shown below. In this case the beam's X axis is shifted away from the X axis of the BACS. You can choose to change only the orientation angle is changed, as shown below, causing the BSCS to rotate around the X axis. 342 Structural and Thermal Simulation Lastly, you can specify non-zero values for both the orientation angle and the DY, DZ offsets. The software performs the rotation first, then translates the BSCS along the rotated BSCS axes to satisfy the DY and DZ offset values, as shown below. Example: Orienting the BSCS Shear Center You can choose to shift either the beam shape origin or shear center with the options on the Beam Orientation Definition dialog box. The figures here illustrate the difference in changing the orientation of the shape origin or the shear center with a channel beam section, in which the shear center falls below the shape origin. In each case below, the left figure shows the change in orientation of the shape origin, and the right figure shows the change in orientation of the shear center. The first figure shows the effect of applying DY and DZ offsets while keeping the orientation angle at zero. 343 Structural and Thermal Simulation - Help Topic Collection In the next figure, only the orientation angle is changed, causing the BSCS to rotate around the X axis. In the last figure, both the orientation angle and the DY, DZ offsets have non-zero values. The software performs the rotation first, then translates the BSCS along the rotated BSCS axes to satisfy the DY and DZ offset values. Review Beam Section Properties When you click the Review button on the Beam Section Definition dialog box, the embedded browser opens with a summary of the computed section properties based 344 Structural and Thermal Simulation on the information you entered for the beam section definition. You can use the embedded browser buttons to print or save the information. The specific entries included in the summary depend upon your beam section definition and upon the product you are running. All products: • Beam Section "Name" — The summary displays the name you specified when you defined the beam section. If you have assigned the beam section to a beam on your model, when you click this link the beam highlights in the model window. Description — The summary displays the optional description you included with the section definition. Type — The summary displays the beam section type, such as square, channel, or sketched. In addition, for standard section types, the summary displays a figure that illustrates the section dimensions. Feature Type — For sketched sections, this entry is either thick or thin. Orientation — For sketched sections, the summary explains how the coordinate axes in the sketch relate to those in the beam shape coordinate system. Dimension(s) — The summary displays the dimensions you entered when defining a standard section. Area — The summary displays the area computed for the beam section based upon the specified dimensions. For general sections this is the entered value. Iyy, Izz, Iyz — The summary displays the values for Iyy and Izz about the centroid with respect to both the beam centroidal principal (BCPCS) and beam shape (BSCS) coordinate systems. It also includes Iyz in terms of the BSCS. J — The summary displays the effective second polar moment of area about the centroid for the beam section. Shear Area Factor — The summary displays the values you specified for Fy and Fz with respect to the BCPCS. For channel, L, and sketched sections, it also lists the values with respect to the BSCS. Shear Center — The summary displays values for Dy and Dz with respect to the BCPCS. For those sections in which the BSCS is not coincident with the BCPCS, the summary also lists values for Dy and Dz with respect to the BSCS. Centroid — The summary displays the computed Y and Z coordinates specifying the location of the origin of the BCPCS system relative to the BSCS. Rotation of Principal Axis — The summary displays the computed value for the rotation of the BCPCS around the beam X axis relative to the BSCS. The value is typically non-zero only for sketched sections and L-beams. Stress Computation Offsets — The summary displays the maximum positive values of the Y and Z offsets for the beam stress recovery points. Grid Points — For all sections, the summary displays the Y and Z coordinates of the stress recovery points with respect to the BCPCS. In addition, for standard section types, the summary displays a figure that relates the labels for the stress recovery points to the beam section shape. Note that in FEM mode there is a maximum of four stress recovery points. • • • • • • • • • • • • • • 345 Structural and Thermal Simulation - Help Topic Collection FEM mode Structure or Thermal: • • • • Warp Coefficient Non-Structural Mass per Unit Length Non-Structural Mass Moment per Unit Length Coordinates of Non-Structural Mass Center of Gravity — The summary displays the Y and Z coordinates with respect to the beam shape coordinate system. Coefficient of Thermal Expansion — Isotropic Enter a value or the name of a thermal expansion coefficient function. You can type in the value, click the f(x) function button to define the coefficient of thermal expansion as a function of temperature, or click the P button to assign a parameter. This property is optional, but you should enter a value if you plan to place a thermal load on the model. Each field that has dimension can have its own units and Mechanica scales the values you enter when the units change. Tsai-Wu Failure Criterion When you select Tsai-Wu, the Tensile Strength, Compressive Strength, Shear Strength, and Normalized Tsai-Wu Interaction Term entry boxes appear. For information about the Tsai-Wu failure criterion for a plane stress state, see Jones, Robert M., Mechanics of Composite Materials. Washington, DC: Taylor and Francis Book Company, 1975. Calculate Stresses and Strains Calculating stresses and strains can take a great deal of time. The resulting files can also be quite large, depending on the size of your model. If you do not select this check box, Mechanica does not provide an output or compute stresses and strains (for measures and full results) for the shells that are assigned this property. If you want Mechanica to calculate these values for measures, select the Calculate Stresses and Strains check box on the Shell Property Definition dialog box. The dialog box expands to display an area for the shell "Top" location and the shell "Bottom" location. Mechanica uses the values that you enter in these areas to calculate the stresses and strains for the corresponding areas for results. 346 Structural and Thermal Simulation Enter values for the following items: • CZ — The distance from the midsurface of the shell at which Mechanica calculates stresses and strains. The software defines CZ relative to material direction 3 of the material orientation assigned to the shell, as shown below: • • Ply Orientation (Degrees) — The orientation of the ply material relative to the material orientation that Mechanica assigns to the element. The software measures the ply orientation angle, (theta), as a counter-clockwise rotation from material direction 1 about material direction 3. The value of this item must be from –360 to +360 . Material — The material at the CZ location. When you click the More button, the Materials dialog box appears. After you select a material, Mechanica displays the material name. Structural Options for Material Definition You define an isotropic material for materials such as steel. For wood or fiberreinforced composite, you define an orthotropic or transversely isotropic material. Different options appear on the Structural tab, depending on the material symmetry you select: • • • Isotropic Orthotropic Transversely Isotropic These symmetries are independent for Structure and Thermal. A material may have isotopic structural properties and orthotropic thermal properties. The Mechanica library contains isotropic materials only. Also, if you selected Edge/Curve as a geometry type, the Orthotropic and Transversely Isotropic options are inactive. 347 Structural and Thermal Simulation - Help Topic Collection Thermal Options for Material Definition Different options appear on the Thermal tab, depending on the material type you choose: • • • Isotropic Orthotropic Transversely Isotropic The Mechanica library contains isotropic materials only. Also, if you selected Edge/Curve as a geometry type, the Orthotropic and Transversely Isotropic options are inactive. Thickness Enter the thickness of the ply for the material you are defining. The thickness may be zero, in which case Mechanica ignores the layer. Note: The sub-laminate thickness may depend on the current values of parameters. The entry box for thickness is parameter-capable. Right-click in the Thickness field of the Shell Property Definition dialog box and select Parameter from the menu. When Mechanica creates the shell elements for the plies, it calculates the total, combined thickness of all the plies and applies the plies so that the total thickness is distributed equally on both sides of the selected surface. For example, let us say you specify three plies with thicknesses as follows: Ply 1 thickness = 2 Ply 2 thickness = 7 Ply 3 thickness = 4 In this case, the total thickness of all three plies is 13 so Mechanica places 6.5 of the thickness on the top of the surface and 6.5 on the bottom. Thus, 4.5 of ply 2's thickness lies atop the surface and 2.5 of ply 2's thickness lies below. Working with the Laminate Layup Dialog Box Use these buttons on the laminate layup version of the Shell Properties dialog box to manipulate the table containing the laminates' specification. 348 Structural and Thermal Simulation To select a row, click one of the fields in the table. • — Add a row to the layup table above the selected row. If none of the rows are selected, when you click this button Mechanica adds a row to the top of the table. — Delete the selected row. — Clear all of the values from the table, but leave the rows. — Remove empty rows and compact the remaining rows. Mechanica leaves at least one empty row, if none of the rows contain entries. Preview Layup — Display a non-editable dialog box with the values entered for the laminate layup definition. Preview Stiffness — Display a non-editable dialog box with the values entered for the stiffness components. • • • • • Layup When you define shell properties for laminate layup-type shells, you can specify the layer repetition pattern. Use the drop-down list under Layup Symmetry on the Shell Property Definition dialog box. You can select one of these options: • • • No Symmetry — The layers are not repeated. Symmetrical — The layers are repeated in reverse order. Antisymmetrical — The layers are repeated in reverse order, and the orientation is also changed. For example, a three-layer laminate would change as follows: No Symmetry Symmetrical Antisymmetrical a b c a b c c b a a b c -c -b -a The dialog boxes require that you complete a table that defines the layers in your laminate. Each line in the table represents either a ply or sub-laminate of the shell property being defined. Note that the row numbers decrease as you go down the list since plies are traditionally numbered from the bottom up. 349 Structural and Thermal Simulation - Help Topic Collection Example: Material Coordinate System for a Cylindrical UCS This illustration shows the material directions you define relative to a cylindrical UCS. Note that the orientation varies at different locations on the surface: Young's Modulus — Isotropic Enter a value for the Young's modulus, the modulus of elasticity of the material. You can type in the value, click the f(x) function button to define Young's modulus as a function of temperature, or click the P button to assign a parameter. You must enter a positive value or, if Young's modulus varies with temperature, the name of a Young's modulus function for this property. Each field that has dimension can have its own units and Mechanica scales the values you enter when the units change. Poisson's Ratio — Isotropic Enter a value for Poisson's ratio, the ratio of lateral contraction to longitudinal extension for a bar in tension. You can type in the value, click the f(x) function button to define Poisson's ratio as a function of temperature, or click the P button to assign a parameter. You must enter the name of a Poisson's ratio function or a value between –0.9999 and 0.4999. The default is 0.3. Each field that has dimension can have its own units and Mechanica scales the values you enter when the units change. 350 Structural and Thermal Simulation Isotropic Properties Select the Properties tab to enter values for the following properties. You can define any of these properties as a function of temperature or you can assign a parameter value to define a property. You can either type in a value or click the ƒ(x) button to define a function or P button to assign a parameter as appropriate. Each field that has dimension can have its own units, and Mechanica scales the values you enter when the units change. • • • Poisson's Ratio — You must enter the name of a Poisson's ratio function or a value between –0.9999 and 0.4999. The default is 0.3. Young's Modulus — You must enter a positive value or, if Young's modulus varies with temperature, the name of a Young's modulus function for this property. Coeff. of Thermal Expansion — This property is optional, but you should enter a value if you plan to place a thermal load on the model. Isotropic If you select Isotropic material symmetry on the Structural tab on the Material Definition dialog box, the following tabs appear: • • • Properties Failure Criterion Fatigue If you select the Thermal tab, the following properties appear: • • Specific Heat Thermal Conductivity Each field that has dimension can have its own units and Mechanica scales the values you enter when the units change. Maximum Strain Failure Criterion When you select Maximum Strain, the Tensile Strength, Compressive Strength, and Shear Strength entry boxes appear. For information about the in-plane strains in the principal strain directions, see Jones, Robert M., Mechanics of Composite Materials. Washington, D.C: Taylor and Francis Book Company, 1975. 351 Structural and Thermal Simulation - Help Topic Collection Example: Curved Surface Directions This figure shows the material orientation relative to the first surface and second surface directions on a curved surface. The dashed lines indicate surface directions. (These lines are the parametric curves of the surface.) Failure Criterion Specify strength properties for isotropic and transversely isotropic materials to determine whether a material has failed under given loading conditions. These properties are stored in the material library. Select None if no failure criterion is required. To view the results, display a fringe plot. If the failure index is equal to or greater than 1, the material has failed. Failure index measures and results are not available if you do not request stress quantities. For Isotropic Properties — Select one of the following stress quantities from the Failure Criterion tab: • • • • None — This is the default. Distortion Energy (von Mises) Maximum Shear Stress (Tresca) Modified Mohr For Transversely Isotropic Properties — Select one of the following from the Failure Criterion tab: • • 352 None — This is the default. Tsai-Wu Structural and Thermal Simulation • • Maximum Stress Maximum Strain These failure criteria are valid only for 3D shells. The 1 and 2 on the dialog box quantities denote the 1 and 2 directions of the material. Coefficient of Thermal Expansion Enter values for the coefficients of thermal expansion. You can define this property or you can assign a parameter to the property. Type in a value or click the P button as appropriate. For orthotropic material properties, enter values for: • • • a1 a2 a3 These values represent the thermal expansion coefficient in each of the three principal material directions of the model. For transversely isotropic material properties, enter the following two values for coefficients of thermal expansion: • • a1 a2 = a3 These values represent the thermal expansion coefficient in each of the three principal material directions of the model, with equal values in directions 2 and 3. You should enter values for this property if you plan to place a thermal load on the model. Ultimate Compressive Strength Each field that has dimension can have its own units and Mechanica scales the values you enter when the units change. For Isotropic Properties — If you enter a value for this quantity: • • The value must be negative. You must also enter a value for ultimate tensile strength. For Transversely Isotropic Properties — For all failure criteria, if you enter values for this quantity: • Sc1 and Sc2 must be negative. 353 Structural and Thermal Simulation - Help Topic Collection Note: Sc1 is compressive failure stress in the material 1 direction and Sc2 is compressive failure stress in the material 2 direction. • You must also enter values for ultimate tensile strength and shear strength. Example: Laminate Layup A laminate layup is a number of shells layered together. Each shell has its own midsurface. You calculate the stress for each ply when you analyze the model. For a shell with laminates, the face of the shell is at the midsurface of the laminated layers: When you create a laminate stiffness shell property set, you can realign the default material orientation. Example: Variable Material Orientation Even though Mechanica draws only one material orientation icon for the entity, the material orientation is defined everywhere on that entity and may vary from one position to the next: 354 Structural and Thermal Simulation Example: Rotation for Shells and Surfaces In the following example, the principal material directions from the example in 2D Surface Directions are rotated about material direction 3 by –30º: Mechanica uses the right-hand rule to determine the direction of each rotation. If you had entered a positive angle, the material directions would have rotated in the other direction. Modified Mohr Failure Criterion When you select Modified Mohr, the Ultimate Tensile Strength (UTS) and Ultimate Compressive Strength entry boxes appear. For more information about how the Modified Mohr failure criterion is calculated, see Shigley, Joseph Edward, Mechanical Engineering Design, First Metric Edition. New York: McGraw-Hill Book Company, 1986. Each field that has dimension can have its own units and Mechanica scales the values you enter when the units change. Maximum Shear Stress (Tresca) Failure Criterion When you select Maximum Shear Stress (Tresca), the Tensile Yield Stress entry box appears. Enter a positive value for yield stress. If you leave the field blank, Mechanica does not compute failure indexes for this material. 355 Structural and Thermal Simulation - Help Topic Collection The software calculates Tresca failure index as follows: failure_index = 2 x Maximum Shear Stress/Tensile Yield Stress Each field that has dimension can have its own units and Mechanica scales the values you enter when the units change. Density Enter a positive value for the mass density associated with this material. This property is optional, unless you plan to define a modal, prestress modal, or any dynamic analyses for the model in Structure. To specify mass density, you can type in a value or click the P button to assign a parameter. Example: Laminate Orientation You define the orientation of your laminate layup with respect to the material orientation specified for the surface. The figures below illustrate the sign convention for the ply orientation relative to the material orientation. The 1' and 2' axes for the material orientation define a right-hand coordinate system with the 3' axis extending out of the plane of the illustration. For a 0 laminate, the 1 direction of the ply is aligned with the 1' direction of the material. For a 90 laminate, the 1 direction of the ply is aligned with the 2' direction of the laminate. 356 Structural and Thermal Simulation Orientation Enter the orientation for the ply or sub-laminate. For a single ply, the orientation is the amount the material is rotated about the material direction perpendicular to the shell or surface (the material orientation 3 direction). See the illustration for more information. For sub-laminates, the orientation is the amount by which the entire sub-laminate is rotated. Enter positive or negative real number values for the orientation. If you have more than one ply, you can specify multiple orientations by entering the values separated by a slash. For example, enter 0/90/45/–45 for a 4-ply laminate. To enter a negative orientation, insert a minus sign before the number in the entry box. For example, the negative orientation of a ply can be entered as –45. The entry box for orientation is parameter-capable. Right-click in the Orientation field of the Shell Property Definition dialog box and select Parameter from the menu. Note: If you enter multiple values for the orientation, you cannot use expressions based on parameters, and you cannot mix parameter names and real numbers. For example, you cannot use an expression such as 90/45/ANGLE. Young's Modulus Enter values for the Young's Modulus (the modulus of elasticity) of the material. You can define this property or you can assign a parameter to the property. Type in a value or click the P button as appropriate. For orthotropic material properties, enter positive values for: • • • E1 E2 E3 These values represent the Young's modulus along each of the three principal material directions of the model. For transversely isotropic material properties, enter positive values for the following two Young's modulus values: • • E1 E2 = E3 These values represent the Young's modulus along each of the three principal material directions of the model, with equal values in directions 2 and 3. 357 Structural and Thermal Simulation - Help Topic Collection Number Enter the number of times the ply definition listed in the table is repeated for this laminate. You can also use a counter to increment the number from 1 to 100. Mechanica does not accept negative values in this field. If the value is zero, Mechanica ignores the ply. The Number field for at least one of the plies in the laminate must contain a non-zero, positive number. Example: 2D Surface Directions This figure shows the material orientation relative to the first and second surface directions on a 2D diamond-shaped surface. Note that the first and second surface directions are not necessarily orthogonal, but the three material orientation directions are mutually orthogonal. Normalized Tsai-Wu Interaction Term Enter a value for the Tsai-Wu normalized interaction term. This quantity appears only if you select Tsai-Wu as the failure criterion. The quantity F12* is dimensionless. Thermal Values for Isotropic Properties In Thermal, enter values for these isotropic properties: • • Specific Heat — Enter a positive value for the material's specific heat. Thermal Conductivity — Enter a positive value for the material's conductivity. To specify thermal conductivity, you can type in a value or click the P button to assign a parameter name. 358 Structural and Thermal Simulation Material or Sub-laminate Enter the name of a previously defined material for your shell definition. You can also use a previously defined laminate as one of the plies when you define a laminate layup-type shell. To specify a material or sub-laminate as part of your shell definition, use one of these methods on the laminate layup version of the Shell Property Definition dialog box: • You can right-click in the Material/Sub-laminate field and select Material. The Materials and Shell Properties in the Model dialog box appears. Select a laminate layup-type shell property from the list, or click More to transfer one from the library to the model. You can type in the name of an existing material or laminate-layup shell property. Be careful while entering a name for a shell property or a material. If you have assigned the same name to a material and a shell property, Mechanica searches for saved materials and shell properties in the following order in trying to match the entered name: o o o materials in the model materials in the material library shell properties in the model • Keep the following points in mind when specifying sub-laminates: • • • Mechanica displays only those shell properties whose structural properties are those of a laminate layup. The dialog box does not allow recursive definitions. A shell property cannot reference itself as a sub-laminate. You cannot select shell properties defined for a 3D model if the active model is 2D. If you select a previously defined laminate, you cannot edit the value in the Thickness entry box. Shell Thickness The properties of a shell are determined by thickness, material, and shape. The following points are true for shell thickness: • • • Your model must have either a constant or multiconstant thickness. In FEM mode, it can also have a variable thickness. The thickness of a body you model with one or more entities should be significantly smaller than the length of any of the body's other dimensions and radii of curvature. As a guideline, the ratio of the body's thickness to its other dimensions should not be greater than 1 to 10 and no less than 1 to 1000. 359 Structural and Thermal Simulation - Help Topic Collection • For shells, the thickness times the maximum curvature cannot be more than 1.5. In this illustration, the face of the entity that appears in the work area is the midsurface of the entity. For example, if you assign a thickness of 1 to a shell, the element actually has a thickness of 0.5 in each direction. Solid Circle The icon for a solid circle beam section type looks like this: When you select Solid Circle as the beam type on the Beam Section Definition dialog box, you must enter the radius of the circular beam cross section in the R text-entry box. The value you enter must be a positive number. The figures below illustrate stress recovery points for solid circle beam section types. The figure on the left shows the points for native mode, and the figure on the right shows the points for FEM mode. 360 Structural and Thermal Simulation Stress Grids When you click the arrow beside Stress Grids on the Beam Section Definition dialog box for general beam sections, the dialog box expands to display a table of text-entry boxes. Enter the Y Offset and Z Offset values for stress recovery points for your section. You can define y and z values for up to nine points for the native mode, and four in the FEM mode. You must specify values in the stress grid in order to view results for beam recovery points. Example: Cylindrical Coordinate System This example shows a material coordinate system you define relative to a cylindrical coordinate system. Notice that the orientation varies at different locations on the cylinder: Mechanica projects a Cartesian coordinate system onto a surface or shell in the same manner as Mechanica projects a vector. Maximum Stress Failure Criterion When you select Maximum Stress, the Tensile Strength, Compressive Strength, and Shear Strength entry boxes appear. For information about the in-plane stresses in the principal stress directions, see Jones, Robert M., Mechanics of Composite Materials. Washington, D.C: Taylor and Francis Book Company, 1975. 361 Structural and Thermal Simulation - Help Topic Collection Distortion Energy (von Mises) Failure Criterion When you select Distortion Energy (von Mises), the Tensile Yield Stress entry box appears. Enter a positive value for yield stress. If you leave the field blank, Mechanica does not compute failure indexes for this material. The von Mises failure index is calculated as follows: failure_index = von Mises Stress/Tensile Yield Stress Each field that has dimension can have its own units and Mechanica scales the values you enter when the units change. Function — Material Properties Click the ƒ(x) button to select or create a temperature-dependent material property: • • If you defined one or more functions for your model, the Functions dialog box appears. Select a function from the dialog box. If no function name exists for your model, the Function Definition dialog box appears on which you can define one or more functions. After you select or define a function and click OK, the function name appears in the text box next to the ƒ(x) button on the Material Definition dialog box. Rectangle The icon for a rectangular beam section type looks like this: When you select Rectangle as the beam type on the Beam Section Definition dialog box, you must enter positive values for the following cross-section dimensions: • • 362 b d Structural and Thermal Simulation The figures below illustrate stress recovery points for rectangular beam section types. The figure on the left shows the points in native mode, and the figure on the right shows the points in FEM mode. L-Section The icon for an L-section beam section type looks like this: When you select L-Section as the beam type on the Beam Section Definition dialog box, you must enter positive values for the following cross-section dimensions: • • • • b t di tw If you are interested in examining the exact effects of shear on a beam, enter positive values for Shear Factor FY and Shear Factor FZ. These factors represent the ratio of a beam's effective "shear area" to its true cross-sectional area for shear in the principal Y and Z directions. The default value is 0.833333, which is accurate for rectangular cross sections. Note: An L-section beam type has fewer than two planes of symmetry. Therefore, make sure the beam is loaded or braced to prevent twist under shear loading. The figures below illustrate stress recovery points for L-section beam section types. The figure on the left shows the points for native mode, and the figure on the right shows the points for FEM mode. 363 Structural and Thermal Simulation - Help Topic Collection Beam Sections Dialog Box Use the items on the Beam Sections dialog box to manage your beam section definitions. When you select the Properties>Beam Sections command, or click the More button in the Section area of the Beam Definition dialog box, this dialog box appears. This dialog box enables you to assign a previously defined beam section to your beam, or to create a new beam section. The dialog box contains the following items: • Beam Sections in Library — Displays a scrollable list of the beam sections saved in your library. You can select one of these definitions and click the right arrow to move it to the Beam Sections in Model list. This assigns it to the current beam definition. Beam Sections in Model — Displays a scrollable list of the beam sections assigned to one or more beams in the current model. You can select one of these section names to assign to the current beam definition. To add a beam section to the library, select it and use the left arrow to add it to the Beam Sections in Library list. Description — This non-editable field displays the description you entered, if any, for the beam section currently selected in the Beam Sections in Library or Beam Sections in Model list. New — Opens the Beam Section Definition dialog box to allow you to create a new beam section. Copy — Copies the selected beam section to a new name and adds it to the Beam Sections in Model list. Mechanica gives the copy the default name BeamSectionx, where x is one more than the number of items created for the model. Note that you cannot copy sketched beam sections. Edit — Opens the Beam Section Definition dialog box with the values of the selected beam section. Delete — Removes the selected beam section from the Beam Sections in Model list. • • • • • • If you accessed the Beam Sections dialog box from the Beam Definition dialog box, when you close the Beam Sections dialog box, Mechanica uses the section you selected from the Beam Sections in Model list for the current beam definition, and displays the beam section name in the Beam Definition dialog box. 364 Structural and Thermal Simulation General There is no predefined shape for a General beam section type. When you create a beam with a general section, the beam icon on your model includes only the Y and Z axes. For General beam section types, you must define values for the following on the Beam Section Definition dialog box: • • • • • Area Iyy, Izz, Iyz J Shear Fy, Shear Fz Shear Dy, Shear Dz You can optionally perform the following tasks: • • Use the Stress Grid option to enter Y and Z offset values for each stress recovery point. You must specify stress grid values in order to view results for beam stress recovery points for general beam sections. Use the Review button to display the section properties of a beam section. The default graphic for a general beam section type is illustrated below for native mode. Note that this graphic appears regardless of the stress recovery point locations that you define using the Stress Grid. That is, the software does not display a graphic with the entered locations when you define your results window. In FEM mode, the software uses the first four points that you define for the section. Factors Determining the Selection of Entities The type of entity you can select on your model depends on the model type and the type of material orientation. Model Type 3D Material Orientation Type 3D Selectable Entities Part (part mode) Parts (assembly mode) Surfaces Surfaces 3D 2D (Any) 2D 2D 365 Structural and Thermal Simulation - Help Topic Collection Hollow Rect The icon for a hollow rectangle beam section type looks like this: When you select Hollow Rect as the beam type on the Beam Section Definition dialog box, you must enter positive values for the following cross-section dimensions: • • • • b d bi di The figures below illustrate stress recovery points for hollow rectangle beam section types. The figure on the left shows the points for native mode, and the figure on the right shows the points for FEM mode. Material Assignment in Part Mode and Assembly Mode In the part mode, you can assign material properties to the volume defined by the part and to curves and surfaces in the part. However, Mechanica uses these curve and surface properties only if you assign a beam section to the curve or assign a shell property to the surface. Otherwise, Mechanica disregards curve and surface assignments. In the assembly mode, you assign material properties to each of the parts that make up the assembly. As in the part mode, you can also assign material properties to individual curves and surfaces. However, Mechanica uses the material properties assigned to curves only if you also assign a beam section property to the curve. Similarly, Mechanica uses the material properties assigned to the surface only if you also assign a shell property to the surface. 366 Structural and Thermal Simulation Be aware that if you assign material properties to a part, curve, or surface in part mode, those material properties are not available in assembly mode, and the reverse. For example, if you assigned AL2014—an aluminum from Mechanica's material library—to body1 in part mode, the software does not automatically assign AL2014 to body1 in assembly mode. Therefore, if you ultimately plan to work with your parts as an assembly, you should strongly consider assigning material properties in assembly mode. Mechanica treats each material you assign to a part or curve as a material set. Each material set consists of a set of material property values that you specify on the Material Definition dialog box. You can assign three types of material properties to the model: isotropic, orthotropic, and transversely isotropic. Most engineering materials are isotropic. If you are working with a curve instead of a part, you can assign isotropic material properties only. J Enter the effective second polar moment of area for each beam section. This property describes stiffness in torsion. You must enter a positive value. For more information on J, see Todhunter and Pearson's History of the Theory of Elasticity, Dover, 1960. Coordinate System Types Mechanica labels the direction buttons according to the type of coordinate system that is current (the WCS is a Cartesian system): Cartesian X Y Z Cylindrical R T Z Spherical R T P You select one axis for each material direction. Since you must select a different coordinate system direction for each material direction, Mechanica automatically selects the remaining axis for the third direction after you select axes for the first two directions. 367 Structural and Thermal Simulation - Help Topic Collection Cost This property is optional. Enter a value for cost per unit mass if you want: • • Mechanica to calculate the model's cost to use cost as a goal or limit in an optimization design study for this model To specify cost per unit mass, you can type in a value or click the P button to assign a parameter. Orthotropic If you select Orthotropic material symmetry, additional items appear on the Material Definition dialog box. For these items, enter values in terms of material directions 1, 2, and 3. If you select the Structural tab, the following properties appear: • • • • Poisson's Ratio Young's Modulus Shear Modulus Coefficient of Thermal Expansion If you select the Thermal tab, the following properties appear: • • Specific Heat Thermal Conductivity Parameter Button Click the P button to define a parameter-specified property. The Select Pro/ENGINEER Parameter dialog box enables you to select or create a Pro/ENGINEER parameter. After you click Accept and return to the Material Definition dialog box, you can convert the parameter into a Mechanica design parameter. Select a parameter from the dialog box. After you click Accept, the parameter name appears in the text box next to the P button on the Material Definition dialog box. Mechanica does not write parameters to the library but evaluates the parameters and writes their current value to the library. 368 Structural and Thermal Simulation Referenced Coordinate System When you select Referenced Coordinate System, Mechanica determines the material orientation by projecting the UCS directions onto the surface or shell, or into a solid. Material Direction 3 remains perpendicular to the surface or shell. Depending on the entity you select: • • • For surfaces and shells, Mechanica displays the current coordinate system (the WCS is selected by default). You can select another coordinate system if you wish. For parts, solids, volumes, 2D plates, and 2D solids, Mechanica displays Material Directions 1, 2, and 3, which you can change on the dialog box if you like. A menu appears that lets you define the following items: o Projected X axis — This option is the default value, and the only available choice in FEM mode. It defines Material Direction 1 to be the direction of the X axis of the referenced coordinate system projected onto the surface. o Projected closest axis — This option defines Material Direction 1 through a series of calculations. To calculate this value, the software first determines which of the three coordinate system directions—(X, Y, Z) or (R, T, Z) or (R, T, P)— is closest to the surface normal. Next, the software picks the coordinate system direction that follows the previously selected direction. For example, if the X direction is closest to the surface normal, the software selects the Y direction. Or, if the Z direction is closest to the surface normal, the software picks the X direction. The projection of this direction onto the surface is defined as Material Direction 1. To learn about more aspects of the Referenced Coordinate System, see: • • • Coordinate System Types Example: Material Coordinate System for a Cylindrical UCS Example: Cylindrical Coordinate System Shear Strength For all transversely isotropic failure criteria, if you enter a value for this quantity keep the following in mind: • • Ss must be positive. You must also enter values for ultimate tensile strength and ultimate compressive strength. Each field that has dimension can have its own units and Mechanica scales the values entered when you change the units. 369 Structural and Thermal Simulation - Help Topic Collection Ultimate Tensile Strength (UTS) Each field that has dimension can have its own units and Mechanica scales the values you enter when the units changed. For Isotropic Properties — If you enter a value for this quantity: • • The value must be positive. You must also enter a value for ultimate compressive strength. For Transversely Isotropic Properties — For all failure criteria, if you enter values for this quantity: • St1 and St2 must be positive. Note: St1 is tensile failure stress in the material 1 direction, and St2 is ultimate tensile failure strength in the material 2 direction. • You must also enter values for ultimate compressive strength and shear strength. Transversely Isotropic If you select this type of material symmetry on the Structural tab on the Material Definition dialog box, the following tabs appear: • • Properties Failure Criterion If you select the Thermal tab, these properties appear: • • Specific Heat Thermal Conductivity Solid Ellipse The icon for a solid ellipse beam section type looks like this: 370 Structural and Thermal Simulation When you select Solid Ellipse as the beam type on the Beam Section Definition dialog box, you must enter positive values for the following cross-section dimensions: • • a b The figures below illustrate stress recovery points for solid ellipse section types. The figure on the left shows the points for the native mode, and the figure on the right shows the points for the FEM mode. Iyy, Iyz, Izz Enter the second moments of area for each beam section. Mechanica interprets the entered values with respect to the BSCS. The software also displays the values with respect to the BCPCS when you review beam section properties. These properties describe stiffness in bending about a beam's principal Y and Z axes. You must enter a positive value for Iyy and Izz. Iyz can be either positive or negative and must obey the rule: (Iyz)2 < Iyy Izz Note that Iyz is zero for beam sections for which the BSCS is the same as the BCPCS. Hollow Ellipse The icon for a hollow ellipse beam section type looks like this: 371 Structural and Thermal Simulation - Help Topic Collection When you select Hollow Ellipse as the beam type on the Beam Section Definition dialog box, you must enter positive values for the following cross-section dimensions: • • • a — the length of the major (longer) cross section of the outer ellipse b — the length of the minor (shorter) cross section of the outer ellipse ai — the length of the major (longer) cross section of the inner ellipse Mechanica calculates the inside minor axis by making its ratio to the inside major axis the same as the ratio of the outside minor axis to the outside major axis, as shown in this equation: Inside Minor = (Outside Minor/Outside Major) Inside Major If you want to examine the exact effects of shear on a beam, enter positive values for Shear Factor FY and Shear Factor FZ. These factors represent the ratio of a beam's effective "shear area" to its true cross-sectional area for shear in the principal Y and Z directions. The default is 0.833333, which is accurate for rectangular cross sections. The figures below illustrate the stress recovery points for hollow ellipse section types. The figure on the left shows the points in native mode, and the figure on the right shows the points in FEM mode. Hollow Circle The icon for a hollow circle beam section type looks like this: When you select Hollow Circle as the beam type on the Beam Section Definition dialog box, you must enter positive values for the following cross-section dimensions: • • 372 R Ri Structural and Thermal Simulation The figures below illustrate stress recovery points for hollow circle section types. The figure on the left shows the points for native mode, and the figure on the right shows the points for FEM mode. Diamond The icon for a diamond beam section type looks like this: When you select Diamond as the beam type on the Beam Section Definition dialog box, you must enter positive values for these cross-section dimensions: • • b d Stress recovery points for diamond beam section types are illustrated below. The figure on the left shows the points in native mode, and the figure on the right shows the points in FEM mode. Area Enter the cross-sectional area for each beam section. You must enter a positive value. Because General beam section types lack geometry, for the purpose of calculating torsional stress, Mechanica assumes that the cross section is circular. 373 Structural and Thermal Simulation - Help Topic Collection Channel The icon for a channel beam section type looks like this: When you select Channel as the beam type on the Beam Section Definition dialog box, you must enter positive values for the following beam cross-section dimensions: • • • • b t di tw If you are interested in examining the exact effects of shear on a beam, enter values for Shear FY and Shear FZ. These factors represent the ratio of a beam's effective "shear area" to its true cross-sectional area for shear in the principal Y and Z directions. You must enter a positive value for each of these properties. The default is 0.833333, which is accurate for rectangular cross sections. When you click Accept, if your section type has fewer than two planes of symmetry, Mechanica informs you that the beams should be loaded or braced to prevent twist under shear loading. Stress recovery points for channel beam section types are illustrated below. The figure on the left shows the points for native mode, and the figure on the right shows the points for FEM mode. 374 Structural and Thermal Simulation I-Beam The icon for an I-beam beam section type looks like this: When you select I-Beam as the beam type on the Beam Section Definition dialog box, you must enter positive values for the following cross-section dimensions: • • • • b t di tw The figures below illustrate stress recovery points for I-beam beam section types. The figure on the left shows the points for native mode, and the figure on the right shows the points for FEM mode. Shear FY, Shear FZ Enter these values on the Beam Section Definition dialog box for general sections if you are interested in examining the exact effects of shear on a beam. These factors represent the ratio of a beam's effective "shear area" to its true crosssectional area for shear in the principal Y and Z directions. You must enter a positive value for each of these properties. If you leave this value blank: • • Native mode assigns the default value of 0.833333, which is accurate for rectangular cross sections. FEM mode interprets the value as undefined. For L and channel sections, the default value is section-specific. 375 Structural and Thermal Simulation - Help Topic Collection Shear DY, Shear DZ Enter these values on the Beam Section Definition dialog box to specify the distance between shear center (the point on a beam section about which the section rotates under deflection) and the centroid of the beam section, with respect to the principal axes. The values for these properties are relevant for non-doubly-symmetric beam sections (those that are not symmetrical about two normal axes). For many standard beam sections types such as square and rectangle, the shear center and the beam centroid are the same. For channel, thin sketched, and L-sections, Mechanica calculates these values automatically. For general and solid sketched beam sections, you need to calculate the values yourself and specify them on the dialog box. You can load a beam directly through its shear center, eliminating torsion from the element's behavior, by aligning the section to the assigning curve. To do this, you can use the Beam Orientation functionality to apply beam offsets. You can view the offset distances to enter for beam orientation when you review beam section properties. Note that the values given on this review for Shear Center are reported with respect to the BCPCS. Alternatively, you can select the Shear Center option on the Beam Orientation Definition dialog box and leave the offset values set to zero. Structural Constraints About Structure Constraints In Structure and FEM mode Structure, use the Insert>Displacement Constraint or Insert>Along Surface Constraint command to constrain entities in your model or use relations functions. In defining constraints for a Structure model, your goal is to fix portions of the model geometry so that the model cannot move, or can move only in a predetermined way. Your model's constraints, along with its loads, provide the software with the real-world conditions that it uses as the basis for analysis. In native mode you can also use the Insert>Symmetry Constraint command to apply constraints that allow you to take advantage of your model's geometric symmetry. In constraining a Structure model, you are defining the extent to which your model can move in reference to a coordinate system. Thus, when you add constraints, you specify translational or rotational part movement. The software assumes that any unconstrained portion of your Structure model is free to move in all directions. Before applying constraints, see Guidelines for Structure Constraints. Every constraint is created as part of a constraint set. In Structure, you can use only one constraint set per analysis. 376 Structural and Thermal Simulation You can choose from the following constraint types: • • • Displacement constraint — Create various entity-based constraint types. Symmetry constraint — Create cyclic or mirror symmetry constraints. This command is not available in FEM mode. Along Surface constraint — In FEM mode only, create a displacement constraint along a surface. For each of these three constraint types, you need to consider different factors and use different creation methods. To review information that is common to all three constraint types, see: • • Adding Constraints Constraints, Loads, and Analysis Types Mechanica applies the constraints you specify to all the entities that you select and places a constraint icon at each location. For compressed solid parts in assemblies, Mechanica automatically adds a constraint between intersecting midsurfaces whenever possible. When Mechanica adds such a constraint, the constrained midsurfaces are forced to deform together during a run. If you are working in Thermal, see About Thermal Boundary Conditions for information on applying convection conditions, prescribed temperatures, cyclic symmetry, or in FEM mode, radiation. After you create a constraint, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a constraint, Mechanica asks you for confirmation first. You can also troubleshoot constraints, control constraint icon visibility, and place constraints on layers. To create, edit, or delete constraint sets, select Properties>Constraint Sets to open the Constraint Sets dialog box. Adding Constraints For Mechanica to perform most types of analyses, you must constrain at least one area of your model. When you apply constraints, Mechanica associates the constraints with model geometry. For structural analysis, a constraint is an external limit on the movement of a portion of your model. For thermal analysis, a constraint is an external limit on the temperature of a portion of your model. You can apply a constraint to a single geometric entity or to multiple entities. When you apply a constraint to multiple entities, Mechanica does not allow you to mix entity types, except for points and vertices, and edges and curves. For example, if you specify a point as the first entity, all remaining entities, to which constraint applies, must also be points or vertices. 377 Structural and Thermal Simulation - Help Topic Collection Note: Constraints applied to vertices and to multiple datum points in Mechanica FEM mode are suppressed in Mechanica. In general, you should plan the placement of your constraints according to the model type. For example, if you are working with a solid model, you should try to place your constraints on surfaces or surface regions rather than points or curves. With shell models, you should try to place your constraints on curves, surfaces, or surface regions, depending on the load type. Although you can place constraints on other entity types, this placement can adversely affect convergence. When constraining a structural assembly, be aware that you must constrain all independent bodies in the assembly. If the constraint set does not constrain all bodies in the model, Mechanica is unable to run the associated analyses. You can place some types of constraints on a surface that will be compressed to a midsurface edge. When possible, Mechanica automatically transfers the constraint from the original surface to the compressed midsurface. When not possible, Mechanica deletes the constraints. Constraints, Loads, and Analysis Types Some Mechanica analysis types require loads and constraints. To help you determine which of these modeling entities your analysis plan calls for, the following tables provide an overview of the load and constraint requirements for the various analysis types. FEM Mode Analyses Analysis Type Constraint or Boundary Condition Load Mechanica Structure structural modal Mechanica Thermal thermal yes optional yes yes optional no 378 Structural and Thermal Simulation All Other Mechanica Analyses Analysis Type Constraint or Boundary Condition Load Mechanica Structure static modal buckling large deformation static prestress static prestress modal contact dynamic time dynamic frequency dynamic random dynamic shock fatigue Mechanica Thermal steady-state thermal transient thermal yes yes optional optional yesa yesb yesc yesa yesa yes yesa yes yes yes yes no optional no yes optional yes no optional yes yes yes yes yesd a. If your model includes point-to-ground springs, you do not need to specify a constraint. b. If you plan a constrained modal analysis, you need to add at least one constraint. However, for unconstrained modal analyses with rigid mode search, you need no constraints. c. Buckling analysis uses the loads and constraints defined for the static analysis you select as a basis for the buckling analysis. d. Fatigue analysis uses the results from a static analysis as the basis for calculating loading. 379 Structural and Thermal Simulation - Help Topic Collection Constraints on Entities You can place displacement constraints on a variety of geometric entities including points, vertices, edges, curves,and surfaces. You define a displacement constraint by selecting the appropriate geometric reference before or after opening the Constraint dialog box to indicate how Mechanica should apply the constraint. The geometric entities you can constrain differ according to the model type and operating mode, as shown below: Model Types 3D 2D plane stress 2D plane strain 2D axisymmetric Constrainable Entities point (FEM only: vertex), edge/curve, surface point, edge/curve, surface point, edge/curve, surface Guidelines for Structure Constraint Sets If you need more information on what a constraint set is, see Understanding Constraint Sets. When you create constraint sets, use the following guidelines: • • • • • • • Use names that are 32 characters or fewer. You can use alphanumeric characters and underbars. Names must start with alphabetic characters. The software does not permit you to use a name already used for another load, constraint, or boundary condition. Use names that uniquely and clearly identify the objective, placement, or other key characteristic of the set. If you use the default names, you or other users may have trouble distinguishing the sets later. You can include as many different types of constraints as you want within a single constraint set. There is no limit to the number of constraint sets you can create or the number of constraints you can include in a constraint set. You can edit and delete the individual constraints that make up a set. You can also edit and delete a constraint set. With constraint sets, you can change the set description or the name. You can remove a given constraint from its set by editing the constraint and changing the selected set. Use the name of a set that already exists, or click New. The software adds the constraint to that set. 380 Structural and Thermal Simulation See Constraint and Load Sets in Structural Analyses for guidelines on how to use constraint sets in your analysis. Understanding Structure Constraint Sets Every constraint you add in the software is part of a constraint set. A constraint set is a collection of constraints that act together, and at the same time, on your model. Constraint sets cannot contain loads. For more information, see Guidelines for Structure Constraint Sets. You can manage your constraint sets with the Constraint Sets dialog box in Structure and FEM mode Structure. When you select the Properties>Constraint Sets command, this dialog box appears with the following buttons: • New — Opens the Constraint Set Definition dialog box. Enter a name and optional description for the new constraint set. Note: You can also access the Constraint Set Definition dialog box by clicking the New button in the Member of Set area on the Constraint and Symmetry Constraint dialog boxes. • Copy — Opens the Copy Constraint Set dialog box to enable you to enter a name for the copy, or accept the default name. When you click OK, the copy is added to the list in the Constraint Sets dialog box. The new constraint set includes copies of the same constraints as the original constraint set. Edit — Opens the Constraint Set Definition dialog box to enable you to modify the information that you used to specify the highlighted constraint set. Delete — Removes the highlighted constraint set. Description — Displays the optional description you entered when you created the constraint set. • • • If you want the flexibility of treating each of your constraints separately, use a unique name and unique set name for each constraint. Remember, however, that an analysis can only access one constraint set. Load and constraint sets provide a logical means of organizing your modeling entities so that you can define analyses effectively and clearly. A carefully considered approach to load and constraint set creation simplifies load and constraint selection when defining your analyses. Although the software permits you to create each load and constraint as a separate load set or constraint set, you can greatly reduce the number of selections you need to make for analysis definition by grouping your loads and constraints into sets. Guidelines for Structure Constraints Mechanica assumes that any part of your model that you do not constrain is free to move in all degrees of freedom available for that model type. For analysis to succeed, all degrees of freedom should be constrained somewhere in your model. 381 Structural and Thermal Simulation - Help Topic Collection Before you add constraints to your model, be sure you have the geometry and references you need already in place. Pay particular attention to the following items: • • • • • Geometry Coordinate Systems Datum Points Regions Points — If you attempt to delete a point associated with a load or constraint, the software informs you of the association by displaying a message with the information that the geometry you want to delete is referenced by a simulation feature. You can delete the point, but Mechanica also deletes the associated load or constraint. Surfaces — If you apply a displacement constraint to a surface by selecting the surface with Box Select or Part Boundary, and Mechanica later creates a new surface due to a parameter change, the software does not automatically apply the existing constraint to the new surface. Shell Models — If you plan to constrain a shell model surface, edge, region, curve, or point that Mechanica may compress during analysis, see Model Entities and Idealizations to learn about how the software processes constraints placed on these geometry types. Cyclic Symmetry Models — If you plan on assigning a cyclic symmetry constraint to a portion of a symmetric model, you must first create the model section in Pro/ENGINEER, using the Cut feature on the original model. Mirror Symmetry Models — If you apply a mirror symmetry constraint to a surface that is collapsed to a curve due to midsurface compression during analysis, the software ignores the mirror symmetry constraint. • • • • Displacement Constraints When you select the Insert>Displacement Constraint command, the following version of the Constraint dialog box appears. Use the following items on the dialog box to define a displacement constraint in Structure: • • • Name — The name of the constraint. Member of Set — The name of the constraint set. You can select an existing constraint set from the drop-down list, or create a new constraint set by clicking the New button to display the Constraint Sets dialog box. References — The drop-down list includes the following geometric entities. You can select the geometry for these references before you enter the dialog box, or use the selector arrow and the normal selection methods to choose the desired geometry. Surface(s) (default) — You can select individual surfaces, several surfaces, quilts, or part boundaries. o Edge(s)/Curve(s) — You can select edges, curves, or composite curves. o Point(s) — You can select single points, vertices, features of points, or patterns of points. Coordinate System — The selection button allows you to change the reference coordinate system. The default is the WCS. o • 382 Structural and Thermal Simulation • Constraint type — The translation and rotation constraints that you can apply differ depending upon your model type and coordinate system. You must specify the setting for each component of these constraint types. o Translation — The extent to which you allow your model to move along a principal axis of the referenced Cartesian, cylindrical, or spherical coordinate system. Rotation — The extent to which you allow your model to rotate in reference to an axis of the referenced Cartesian, cylindrical, or spherical coordinate system. o If you are working with symmetry constraints in native mode or Along Surface constraints in FEM mode, Mechanica provides a different version of the dialog box. Constraint Settings You can select one of the following settings for each constraint option: • • • Free — Allows freedom of movement in the specified direction. Fixed — Constrains the entity, preventing movement in the specified direction. Prescribed — Prescribes a specific displacement or rotation in the specified direction. Prescribed has an effect on the entity similar to a load. When you select Prescribed, an input field appears to the right of the column. You can enter a value, mathematical expression, or parameter name in this field. When entering a value: o For translation options, enter an enforced displacement value in length units. For native mode, if you define the constraint referencing a cylindrical or spherical coordinate system, enter theta and phi in radians rather than length units. In this case, the effective prescribed translation is the product of the radians you enter and the radial distance of the entity from the origin of the reference coordinate system. For rotation options, enter an enforced rotation in radians. o In defining prescribed displacement constraints, you should consider various guidelines and behaviors. • Function of coordinates (FEM mode) — Enables you to define a constraint as a function of coordinates. When you click the Function Of Coordinates button, the f (x) button and option menu appear to the right. Select a function from the option menu or click the f (x) button to use the Functions dialog box to define a new function or edit an existing one. The software uses only the translational degrees of freedom for solid models because solids have only three degrees of freedom. The software disregards any setting you 383 Structural and Thermal Simulation - Help Topic Collection select for the rotational degrees of freedom. If you apply the constraint to shell or beam models, the software uses both translational and rotational settings because the shell formulation has all six degrees of freedom. Constraint Options The following table shows which constraint options are available for each model type in a Cartesian coordinate system: Model Type 3D Constraint Options Trans X, Trans Y, Trans Z, Rot X, Rot Y, Rot Z plane strain and 2D axisymmetric plane stress Trans X, Trans Y, Rot Z Trans X, Trans Y Note: The software ignores any rotational degrees of freedom for 2D solids or solids in 3D models. If you specify constraints on Rot X, Rot Y, or Rot Z for these elements, the software ignores the constraints. The software labels the coordinate directions differently if a cylindrical or spherical coordinate system is active. The following table shows the constraint options for each coordinate system (R=radial, T=theta, and P=phi): Cartesian Trans X Trans Y Trans Z Rot X Rot Y Rot Z Cylindrical Trans R Trans T Trans Z Rot R Rot T Rot Z Spherical Trans R Trans T Trans P Rot R Rot T Rot P 384 Structural and Thermal Simulation For more information about coordinate systems, see Coordinate Systems. Structure Constraint Icons The constraint icon shows which degrees of freedom you constrained. Two rows of boxes appear at the base of the triangle, with each box representing a degree of freedom. The degree of freedom represented by each box varies depending on the type of coordinate system, as shown below: Cartesian: Trans X Rot X Cylindrical: Trans R Rot R Spherical: Trans R Rot R Trans T Rot T Trans P Rot P Trans T Rot T Trans Z Rot Z Trans Y Rot Y Trans Z Rot Z Filled boxes correspond to constrained degrees of freedom or enforced displacements. Empty boxes correspond to degrees of freedom designated as free. In this example, the current coordinate system is Cartesian and the constraint is fixed in Trans X, Trans Y, and Rot Z: 385 Structural and Thermal Simulation - Help Topic Collection This icon indicates cyclic symmetry constraints. The icon appears on your design at the axis of symmetry: This icon indicates mirror symmetry constraints: This icon indicates Along Surface constraints in FEM mode. The icon appears on your design at the reference surface: To Define Displacement Constraints 1. Select Insert>Displacement Constraint or click . The Constraint dialog box opens. 2. Enter a descriptive name or accept the default name. 3. Select the desired constraint set from the Member of Set drop-down list. If you want to create a new constraint set, click the New button to display the Constraint Set Definition dialog box. Enter a name and optional description for a new constraint set. 4. If you dialog now: o o o 5. Click did not select geometric entities as references before you opened the box, select one of the following References from the drop-down list Surface(s) Edge(s) Point(s) and use the normal selection methods to select a reference. and select a 6. If you want to change the reference coordinate system, click coordinate system. The default is the WCS. 386 Structural and Thermal Simulation 7. Click one of these settings buttons for each translational and rotational degree of freedom to define how you want to constrain the geometry: Translation Free Fixed Prescribed Function (FEM mode only) If you select a prescribed setting, enter a value in the field to the right. You can enter a value, mathematical expression, or parameter name in this field. The value should be in length units for translation constraints, and in radians for rotation constraints. 8. Click OK to accept the definition and exit the dialog box. Rotation Troubleshooting Your Constraints Verifying a Constraint If you think that a constraint is not behaving as you expect, you can review the constraint using either of the following methods: • • Select the associated icon on the model and use Edit>Definition. Mechanica displays the appropriate constraint definition dialog box. To change any of your entries, simply edit the dialog box. For Structure models only, if you want to troubleshoot or review your constraints, you can spot-check the constraint icons to generally determine whether you applied the constraint correctly. To learn how to spot-check a constraint icon, you need to understand the icon layout. The constraint icon shows which degrees of freedom you constrained. Two rows of boxes appear at the base of the triangle, with each box indicating the state of the displacement. Following is an example of a constraint icon: Filled boxes correspond to fixed displacements or enforced displacements. Empty boxes correspond to displacements designated as free. In the above example, the constraint fixes the translation in the X and Y directions and fixes the rotation about the Z axis. 387 Structural and Thermal Simulation - Help Topic Collection Performing a Body Check for Assemblies If you are working with an assembly, you can check the number of bodies in your assembly by requesting error detection when you start your Mechanica analysis. During the error detection cycle, Mechanica informs you of how many bodies it finds in your assembly. If this count does not agree with the number you expect, review the assembly in Pro/ENGINEER and correct any mating problems. Then, return to Mechanica and add loads or constraints to any bodies that require them. For more information, see Assembly Considerations. • • These problems can lead to poor accuracy for analysis results. Curve constraints can introduce theoretically infinite stresses or fluxes in solid models. You may want to define a small surface region and apply the constraint to the region instead of to a point. This approach distributes the stresses and fluxes over a slightly wider portion of the model, avoiding concentration problems. Symmetry Constraints Use the Insert>Symmetry Constraint command in Structure or Thermal to create a cyclic or mirror symmetry constraint. This command is not available in FEM mode. When you select this command, the Symmetry Constraint dialog box appears with these items: • • Name — The name of the constraint. Member of Set — The name of the constraint set (in Structure) or boundary condition set (in Thermal). You can select an existing set from the drop-down list, or create a new set by clicking the New button to display the Constraint Sets dialog box. Type — Select one of the following constraint types. The dialog box changes depending upon your selection: o Cyclic o Mirror (Structure only) References — For mirror constraints, you can select points, curves, edges, or surfaces to define the plane of symmetry. For cyclic constraints, you must make the following selections: o o o First Side — Define the first side of the cut section. Second Side — Define the second side of the cut section. Axis — Select the axis of symmetry. Axis is inactive if the software automatically determines the axis of symmetry. • • 388 Structural and Thermal Simulation Your model can include both cyclic and mirror symmetry constraints, with these limitations: • • Your model can include only one cyclic symmetry constraint. The plane defining a mirror symmetry constraint must be orthogonal to the symmetry axis for a cyclic symmetry constraint. Working with Symmetric Models If the model you create is symmetric, you have the option of subdividing the model and working with a symmetric section instead of the entire model. By modeling only a portion of the part, you can greatly reduce the number of elements in your model, thus saving significant analysis time and system resources. Depending on the model, you can also save yourself the overhead spent defining repeated versions of a load or constraint or selecting multiple surfaces, edges, or points during load or constraint definition. For example, if you were trying to determine how a disk reacted to a uniform load applied to the top surface, you might decide that you only wanted to analyze a portion of the disk. Because the part and modeling conditions are symmetrical, the analysis results for a section of the disk would provide information accurate enough to give you an idea of how the model will behave as a whole. For a model to be symmetric for Mechanica's purposes, it must exhibit the following characteristics: • • The geometry must be symmetric. The loads, constraints, and idealizations must be symmetric. There are two types of symmetry you can model in Mechanica—mirror symmetry and cyclic symmetry. Mirror symmetry relies on the principle that one segment of a model is the mirror image of other segments. An example of this type of model would be a rectangular plate with a hole at its center. In native mode you can use the mirror symmetry constraint to take advantage of your model's symmetry. To use mirror symmetry in FEM mode you must apply a displacement constraint to fix translation normal to the plane of symmetry and fix rotations in opposition to the plane of symmetry. Cyclic symmetry relies on the principle that a segment of the geometry is repeated in a cyclic manner throughout the model, but the segment is not a mirror image, either in its geometry or its load scheme. An example of this type of geometry would be a fan blade or turbine. You can only use cyclic symmetry in native mode. FEM mode does not support this type of modeling. The methods you use to develop these two types of symmetry differ, as does the application of constraints and certain loads. Both types of symmetry can prove efficient for a 3D solid or shell model. The choice of which symmetry type you use depends on the model and the problem you wish to solve. Note that, in some situations, you can use 2D axisymmetric modeling in place of symmetry. While not strictly a form of symmetry, 2D axisymmetric modeling 389 Structural and Thermal Simulation - Help Topic Collection provides an extremely efficient alternative to treating your model as a symmetric solid. This form of modeling relies on the principle that a 2D slice of your solid model, if rotated around an axis, can accurately depict the whole of your model's geometry, loads, and constraints. For an example of this type of model, see Setting up a Solid Model for a 2D Analysis on an Internal Surface. Cyclic Symmetry Constraints A cyclic symmetry constraint allows you to analyze a section of a cyclically symmetric model that simulates the behavior of the whole part or assembly. This relational constraint reduces meshing and analysis time. Cyclic symmetry constraints are not available in FEM mode. The original model (part or assembly), from which you take a section, must exhibit cyclic symmetry. That is, copying the cut section about a common axis a specified number of times reproduces the whole model. The number of times must be an integer. The model must exhibit cyclic symmetry in all of the following: • • • • geometry loads other constraints material type and orientation In Structure, a cyclic symmetry constraint prescribes rotation and displacement on two boundaries to be the same. In Thermal, a cyclic symmetry constraint prescribes the temperature distribution on two boundaries to be the same. Note: All results are cyclically symmetric because the model is cyclically symmetric. To solve a cyclic symmetry problem, you need to complete three steps—cutting your model to isolate a cyclically symmetric segment, defining the constraint with the Cyclic Constraint dialog box, and running an analysis that includes the constraint. For more information on cyclic symmetry, see Guidelines for Cyclic Symmetry. Guidelines for Cyclic Symmetry Cyclic symmetry constraints are typically applied to surfaces. When you are making a cyclic symmetry model, you should be careful about applying modeling entities, loads, or constraints to the curves bordering a cyclically constrained curve. Cyclic symmetry boundary geometry should only be associated with surfaces of volumes, curves of surfaces, and points of curves. Geometry not specifically associated with a cyclic symmetry constraint is still available for the assignment of modeling entities. 390 Structural and Thermal Simulation If you choose to apply loads, constraints, and so on to the perimeter of a cyclically constrained model, you need to be aware of how cyclic symmetry affects their behavior. • Loads applied to a boundary curve or to the end point of a curve behave as though divided equally between the applied geometry and the corresponding geometry on the other boundary. This means that a load of 100 lb applied to a curve on one boundary will behave as though a 50 lb load has been applied to each boundary. Heat loads behave in the same way. • Structure constraints applied to a curve behave as though applied to both the applied geometry and the corresponding boundary geometry, through the rotational transformation defined by the cyclic symmetry constraint. That is, a constraint restricting X axis displacement for a boundary curve parallel to the X axis of the current coordinate system effectively restricts radial displacement from the cyclic symmetry axis. The corresponding geometry on the other boundary is not constrained with respect to the X axis of the current coordinate system, as might be expected, but it is effectively restricted with respect to radial displacement. This behavior is true for conflicting constraints applied to corresponding geometry from both boundaries, as well as to enforced displacements. Thermal boundary conditions behave in the same way. • Enforced displacements that effectively displace both boundaries of a cyclic symmetry constraint are not permitted, since they may force violation of cyclic symmetry. For example, a surface that shares common border curves with both cyclic symmetry boundary surfaces cannot have an enforced displacement assigned to it. Enforced displacements are generally permitted, provided they do not violate this condition. All constraints that touch the cyclic symmetry boundary must be associated with a cylindrical or spherical coordinate system whose axis coincides with the cyclic symmetry axis. The stiffness characteristics of your model should be very carefully considered when you use beams, shells, springs, or masses on the cyclic symmetry perimeter. This type of modeling is not recommended. • • To Add a Cyclic Symmetry Constraint 1. Modify a part or an assembly in Pro/ENGINEER by cutting away the portions of the model that are not part of the cyclically symmetric model. 2. In Mechanica, apply a cyclic symmetry constraint, which compensates for the rest of the model not being there, to the boundaries created by the cut feature. 3. Run the desired analyses, making sure that the cyclic symmetry constraint set is included. 391 Structural and Thermal Simulation - Help Topic Collection To Create a Cyclic Symmetry Model Section 1. Open the part or assembly in Pro/ENGINEER. 2. Make a cut feature in your model, leaving the cyclically symmetric portion. For more information on cuts, search the Part Modeling functional area of the Pro/ENGINEER Help Center. 3. You can optionally save the cyclically symmetric portion of the model as a separate model. The cut boundaries need not be planar. If you save the section as a separate model, any analyses or design study that you run will affect the cut section only, not the entire model. When you apply a cyclic symmetry constraint to the cut section, any displacement that occurs will mimic the behavior of the entire, uncut model. To Define a Cyclic Symmetry Constraint After you have created the portion of your model on which you want to place a cyclic symmetry constraint in Mechanica, complete the following steps in Structure or Thermal: 1. Select Insert>Symmetry Constraint or click The Symmetry Constraint dialog box appears. 2. Enter a new name or accept the default name. 3. Select the desired constraint set from the Member of Set drop-down list. 4. If you want to create a new constraint set, click the New button to display the Constraint Set dialog box. Enter a name for the new constraint set. 5. In Structure, select Cyclic from the Type drop-down list. (This is the only choice in Thermal.) 6. Use the selector arrows in the References area and the normal selection methods to select two sets of surfaces, curves, and/or points to define the boundaries of the cyclic symmetry constraint. Depending on the geometry you selected, the software determines the axis of symmetry automatically. If it cannot, the software prompts you to specify the axis of symmetry. Datum axes/curves and solid edges/curves are all available for selection. For planar cuts, the axis of symmetry generally occurs at the intersection of the two cuts at the virtual center of the original model. For non-planar cuts, this is not the case and the location of the axis of symmetry will vary. . 392 Structural and Thermal Simulation Mirror Symmetry Constraints A mirror symmetry constraint fixes the translational degrees of freedom normal to the symmetry plane, and frees the rotational degrees of freedom around the axis normal to the symmetry plane. Note that for solid models, the software disregards the rotational settings, because solids have only three degrees of freedom. However, the software uses the rotational settings for shell and beam models. You can use mirror symmetry constraints in Structure when you want to analyze a segment of a model and project the results to the entire model. Using mirror symmetry allows you to take advantage of your model's symmetry to reduce meshing and analysis time. Mirror symmetry constraints are not available in FEM mode. To use mirror symmetry successfully to analyze your model, your part or assembly must exhibit reflective symmetry through a plane. In other words, the geometry and modeling entities on one side of the plane must be matched in size and location by the geometry and modeling entities on the other side. If your model has mirror symmetry you should be able to visualize folding it along the mirror plane and obtaining two identical geometries with loads and other displacement constraints exhibiting the same placement and orientation. If you run a modal analysis on a model with mirror symmetry constraints or a representative segment of that model, the results will not include any nonsymmetric modes. To determine whether there are nonsymmetric modes, run the modal analysis with the entire model without mirror symmetry constraints. To define a mirror symmetry constraint, you must select sufficient geometric references on your model to define a plane. Keep the following in mind when selecting references: • • • • • The references must be coplanar. You can use combinations of points, curves, edges, or surfaces that lie on the plane of symmetry. You cannot use reference combinations that are collinear. You can define more than one mirror symmetry constraint for your model, but if you do, you cannot reference the same geometric entities for two different mirror symmetry constraints. The symmetry planes for multiple mirror constraints in the same model must be either parallel or orthogonal to each other. To Define a Mirror Symmetry Constraint 1. Select Insert>Symmetry Constraint or click The Symmetry Constraint dialog box appears. 2. Enter a descriptive name or accept the default name. 3. Select the desired constraint set from the Member of Set drop-down list. 393 . Structural and Thermal Simulation - Help Topic Collection 4. If you want to create a new constraint set, click the New button to display the Constraint Set Definition dialog box. Enter a name and optional description for the new constraint set. 5. If it is not already selected, select Mirror from the Type drop-down list. in the References area and use the normal selection methods to 6. Click select sufficient points, curves, edges, or surfaces on your model to specify a symmetry plane. 7. Click OK to accept your definition and exit the dialog box. Along Surface Constraints Constraints Along Surface (FEM mode) You can use the Along Surface Constraint command to create a surface constraint that fixes a planar or cylindrical surface in a particular direction while allowing free movement in other directions. Along Surface constraints are particularly useful for models where you need the surface to move in one or more directions, but be held in place in the remaining directions—for example, a piston that slides within a cylinder, but stays tight to the inner cylinder wall and does not rotate. You define a constraint along a surface by selecting the Along Surface Constraint command and using a special version of the Constraint dialog box to indicate how Mechanica should apply the constraint. Along Surface Constraints (FEM mode) When you select the Insert>Along Surface Constraint command, Mechanica opens a special version of the Constraint dialog box allowing you to create an Along Surface constraint. This dialog box contains the following items: • • • Name — The name of the constraint. Member of Set — The name of the constraint set. You can select an existing constraint set from the drop-down list, or create a new constraint set by clicking the New button to display the Constraint Sets dialog box. Type — Select the type of Along Surface constraint you want to create from the following options: o Planar — Allow full planar movement, but constrain any off-plane displacement. For this type of constraint, you can only select planar surfaces as reference surfaces. o Cylindrical — Allow rotation and translation of a cylindrical surface relative to its axis, but constrain all radial displacement. For this type of constraint, you can only select cylindrical surfaces as reference surfaces. o Cylindrical Fixed Angular — Allow translation of a cylindrical surface along its axis, but constrain all radial and angular displacement. For this type of constraint, you can only select cylindrical surfaces as reference surfaces. o Cylindrical Fixed Axial — Allow rotation of a cylindrical surface about its axis, but constrain all radial displacement and axial translation. For 394 Structural and Thermal Simulation • this type of constraint, you can only select cylindrical surfaces as the reference surfaces. References — Select planar or cylindrical surfaces to constrain, as appropriate to the constraint type. If you want to constrain a plane, you can select the geometry before you enter the dialog box. Otherwise use the selector arrow and the normal selection methods to choose the desired geometry. To Define Constraints Along Surfaces (FEM mode) 1. Select Insert>Along Surface Constraint or click . The Constraint dialog box appears. 2. Select the desired constraint set from the Member of Set drop-down list. 3. If you want to create a new constraint set, click the New button to display the Constraint Set Definition dialog box. Enter a name and optional description for a new constraint set. 4. Select one of the following options from the Type drop-down list: o Planar o Cylindrical o Cylindrical Fixed Angular o Cylindrical Fixed Axial 5. If you did not select geometry before opening the dialog box, click and use the normal selection methods to select the surface or surfaces you want to constrain. Note that, if you selected Planar from the Type option menu, you must select one or more planar surfaces. If you selected one of the cylindrical options, you must select one or more cylindrical surfaces. 6. Click OK to accept the definition and close the dialog box Structure Constraints on Geometry When you define structure constraints for geometry, keep the following points in mind: • Any point, curve, or surface you constrain must be associated with at least one element. To check associations with geometry that will be meshed, click the constraint icon on the model or select the constraint in the Model Tree. Mechanica highlights the constraint icon and associated geometry. A structure boundary condition defined at a point or on a curve can result in theoretically infinite stresses. See Handling Stress Concentrations for information on working around this problem. Any constrained curve constrains the edges, beams, or 2D shells that lie on that curve. Any constrained surface constrains the shells, solid faces, 2D solids, or 2D plates that lie on that surface. Any constrained edge constrains the beams and 2D shells that lie on that edge. • • • • 395 Structural and Thermal Simulation - Help Topic Collection About Thermal Boundary Conditions Use the Insert>Prescribed Temperature or Insert>Convection Condition command to apply thermal boundary conditions to your model or use relations functions. In defining boundary conditions for a Thermal model, your goal is to limit the temperature of your model (prescribed temperature), or to limit the heat through your model (convection condition). You can use the Insert>Symmetry Constraint command to apply a cyclic symmetry boundary condition, which ensures that the temperatures on the edges of the cut are the same. In FEM mode, you can also limit the heat from a model (radiation) by applying a radiation boundary condition with the Insert>Radiation command. Your model's heat loads and boundary conditions, along with its loads, provide the software with the real-world conditions that it uses as the basis for analysis. You can choose from the following types of boundary conditions in Thermal: • • • • Prescribed Temperatures — Specify prescribed temperatures for various geometric entities. Convection Conditions — Create convection conditions that reference geometric entities. Symmetry Constraint (native mode only) — Create cyclic symmetry constraints. Radiation (FEM mode only) — Specify radiation properties for a surface or part boundary. Before applying thermal constraints, see Guidelines for Thermal Boundary Conditions or Guidelines for Thermal Boundary Condition Sets. 396 Structural and Thermal Simulation Example: Axis of Symmetry Constraints on Compressed Midsurfaces For compressed solid parts in an assembly, Mechanica automatically adds, whenever possible, a rigid structural constraint that links compressed curves or surfaces so they are meshed compatibly and will deform together during a run. Mechanica can add this type of constraint when the solid parts are relatively thin—for example, two plates overlapped and mated—and will attempt to add it whenever you run an analysis, or transfer from integrated to independent mode. This drawing shows two relatively thin solids with intersecting surfaces. When these solids are compressed to their midsurfaces, there is a physical gap between the intersecting portion of the midsurfaces, and they no longer touch. The constraints that Mechanica adds bridge this gap, and link the overlapping portions of the two compressed surfaces. If your assembly contains two solids that intersect in a "T" formation, it might look like the drawing below. When these solids are compressed to their midsurfaces, Mechanica attempts to add a constraint between the edge of one midsurface and the corresponding area on the other. 397 Structural and Thermal Simulation - Help Topic Collection Troubleshooting Constraints To help ensure a successful run, you may want to verify your constraints and, if you are working with an assembly, perform a pre-run error detection pass. To learn about constraint verification and other technical tips, read the following: • • • • • Verifying a Constraint Performing a Body Check for Assemblies Handling Stress Concentrations Checking Your Model Insufficiently Constrained Models Example: Cut for Cyclic Symmetry Cut along the dotted lines to create B from A: A 398 Structural and Thermal Simulation B Guidelines for Prescribed Displacement Constraints In defining prescribed displacement constraints, be aware of the following: • • Do not set a prescribed displacement on a model that conflicts with another constraint in the same constraint set. If the Z axis of a reference cylindrical or spherical coordinate system touches an entity that you want to constrain, you may not be able to successfully specify a prescribed displacement value for one or more of the directional components. Mechanica may display a message informing you of the problem. For FEM mode, you will see the message at run time. To work around this problem, you can change the coordinate system to a Cartesian coordinate system or re-orient the coordinate system so that the Z axis no longer touches the entity you want to constrain. • • • When you define a large displacement analysis, do not include constraint sets containing prescribed displacement constraints that reference cylindrical or spherical coordinate systems. Although you can specify prescribed displacements in contact analyses, you should take care not to place these on geometry that is part of the contact region. The software assumes the displacement values you enter are consistent with your principal system of units. Structure Constraints on Regions If you plan to constrain a specific surface region, your model needs to include the contour that defines the region. Before you attempt this type of constraint, see Surface Regions, which describes how to create a region from a datum curve. 399 Structural and Thermal Simulation - Help Topic Collection For assemblies, you cannot constrain geometry that Mechanica merges during a run, such as mated surfaces. You also cannot constrain geometry associated with merged geometry, such as points associated with mated surfaces. If you cannot avoid placing constraints on these geometric entities, you need to work with regions. For more information, see Assembly Considerations. Structure Constraints on Datum Points If you plan to constrain a specific point on an exterior curve or surface in native mode, your part needs to include a datum point at that location. In FEM mode, you can use vertices or datum points. Be aware that point or curve constraints can introduce theoretically infinite stress or thermal fluxes in your model. For more information, see Troubleshooting Your Constraints. Note: Constraints applied to vertices in Mechanica FEM mode are suppressed in Mechanica. You can add datum points within Mechanica as you define your constraints. These datum points are available for your Mechanica sessions only. They are not visible on your part or assembly while you are working at the Pro/ENGINEER level. As an alternative, you can add datum points to your model in Pro/ENGINEER before entering Mechanica. In the latter case, the datum points are available for all your Pro/ENGINEER sessions as well. Structure Constraints and Coordinate Systems The software applies constraints in reference to a coordinate system. When you enter Structure, the current coordinate system is the WCS. You can change the current coordinate system. When you create a constraint, the current coordinate system is the reference coordinate system for the constraint. You can change reference coordinate systems on the Constraint dialog box as part of creating or editing constraints. For more information, see Coordinate Systems. Within the context of Mechanica, you will probably use a Cartesian coordinate system most frequently. Cylindrical and spherical coordinate systems can be useful for symmetrical parts. For example, you could use a cylindrical coordinate system to constrain a slider to a rod (R, T fixed, Z free) without the presence of the rod. Radial enforced displacements simplify the modeling of shrink fits and similar processes. You should not constrain geometry that touches the Z (phi=0) axis of the associated cylindrical or spherical coordinate system. Instead, you can change the coordinate system to Cartesian or change the orientation of the coordinate system so that it does not touch the geometry you want to constrain. If you have a 2D plane strain, 2D plane stress, or 2D axisymmetric model, and you want to associate constraints to a UCS, the UCS must meet the following criteria: • The UCS Z axis must be parallel to the WCS Z axis. (In Pro/ENGINEER, the UCS Z axis must be parallel to the reference UCS Z axis.) 400 Structural and Thermal Simulation • The UCS origin must lie in the WCS Z=0 plane. Mechanica does not report reaction force data at constrained points and edges when the constraint is associated to a UCS. In FEM mode, there may be a conflict between your constraint coordinate systems and coordinate systems associated with connections and mesh controls. Improperly Constrained Springs, Beams, or Shells Springs, beams, or shells that are connected to solids without properly constrained degrees of freedom can cause some problems. Solids have only translational degrees of freedom. Because solids have no rotational degrees of freedom, adjacent idealizations with unconstrained rotational degrees of freedom can cause an error. When springs, beams, or shells are connected to solids, they are really only connected at the translational degrees of freedom. The rotational degrees of freedom remain loose. Make sure that the rotational degrees of freedom are either supported or constrained. • For example, you can attach a network of beams or shells to a set of solids such that the connection has structural integrity without need for further constraints. If you attach only one end of a beam or only one edge of a surface to a solid, you may need to use links to weld the rotational degrees of freedom to the solid. If you attach a single spring directly to a solid, you must constrain the rotational degrees of freedom of the spring, as shown in the following illustration. • 401 Structural and Thermal Simulation - Help Topic Collection Improperly Connected Idealizations These problems are often caused by idealizations that are not connected to the rest of the model or not connected to adjacent idealizations. • Beams are connected when they share common endpoints. Shells are connected when they share a common edge and the endpoints of that edge. Solids are connected when they share a common face and the edges and endpoints of that face. Beams are best connected to shells when the beam and shell share a common edge and the endpoints of that edge. Shells are best connected to solids when the shell and solid share a common face and the edges and endpoints of that face. Two adjacent shells that share two points but no common edge can cause an error. • • Problems with Elements Listed here are some problems with elements that you may encounter in your Mechanica models. • • • Improperly connected idealizations Improperly constrained springs, beams, or shells Elements with links — If a model contains too many links or contains links in areas of high stress concentration, errors can occur during a run. When running AutoGEM, eliminate links where possible by deselecting Create Links Where Needed on the AutoGEM Settings dialog box. Poorly shaped elements — Elements that have sharp angles, excessive curvature, excessive spanned angles, or high aspect ratios—or that are excessively slender or thin—may cause your model to be poorly constrained, may cause delayed convergence, or may yield poor results. Reshape the existing elements or create additional elements in the region. This is particularly true for shell elements. Sharp corners, reentrant corners, and/or notches — These features can exist along the load flow path, on the surface of the structure, or on the boundary between elements with different material types. You should replace them with filleted joints. Excessively small numerical dimensions — The overall dimensions of your model should not be excessively small numerically. For example, it is best to create a model with all dimensions in millimeters or micrometers, rather than with all dimensions in small fractions of meters. Springs without mass — In a modal analysis, each degree of freedom at the endpoint of a spring must be connected to a beam, shell, solid element that has mass, or an element that is connected to a concentrated mass element. Otherwise, the endpoint must be constrained. For example, the rotational degrees of freedom of a spring attached to a solid element should either be constrained or have a concentrated mass with rotational inertia. • • • • 402 Structural and Thermal Simulation Insufficiently Constrained Models If a run ends in an error and the summary or log file informs you that your model is insufficiently constrained for analysis, you should examine your model and attempt to locate the problem. In some cases, you may want to look at the AutoGEM mesh to determine whether the problem arises from the element configuration and quality. Insufficiently constrained models can be the result of: • • • Problems with Elements Problems with Properties Problems with Loads and Constraints Unless you are doing a modal analysis of a free body with rigid mode search on, your model must satisfy the following rules: • • Attach the structure to ground such that you can apply loads to the structure from any direction without causing rigid body motion. Connect all parts of the structure to each other such that you can apply loads to any part of the structure without causing unopposed motion of any part of the structure. The structure must be capable of resisting loads from any direction by transmitting the loads to ground at the constraints. If the structure or any part of the structure is capable of undeformed motion—rigid-body translation or rotation—under some type of loading, you must add appropriate constraints to resist that rigid-body motion. Problems with Loads and Constraints Listed here are some problems with loads and constraints that you may encounter in your Mechanica models. • Concentrated loads or constraints — This includes point loads or constraints applied to plate, shell, or solid elements, and line loads or constraints applied to solid elements. Use distributed loads or the total load at point instead. Improperly applied moments — Errors are sometimes caused by moment application with the axis of twist aligned—or nearly aligned—with the surface normal of a plate or shell element. Apply the moment using the total load at point. Prestress load is too high or exceeds the buckling load — Decrease the prestress load and rerun the model. • • 403 Structural and Thermal Simulation - Help Topic Collection Singularities and Loads The following table shows combinations of loads and different types of entities that can result in infinite stresses or displacements: Load Point disp stress Line, Edge disp stress Surface, Face disp stress Beam ok ok ok ok n/a n/a disp stress disp stress disp stress ok ok ok ok Shell ok disp stress disp stress disp stress ok ok Solid 1 1 2 2 1. Timoshenko and Goodier, Theory of Elasticity, 3rd ed., McGraw-Hill Book Co. Section 36: Concentrated Force at a Point of a Straight Boundary. 2. Timoshenko and Goodier, Theory of Elasticity, 3rd ed., McGraw-Hill Book Co. Section 138: Force on Boundary of a Semi-infinite Body. This information also applies to temperatures and fluxes that result from heat loads, convection conditions, and prescribed temperatures in Thermal. Singularities and Constraints The following table shows which combinations of constraints and different types of entities can possibly result in infinite stresses or displacements: Constraint Point disp stress Line, Edge disp stress Surface, Face disp stress 404 Beam ok ok ok ok n/a n/a disp stress disp stress disp stress ok ok Shell ok disp stress disp stress disp stress ok 1 Solid ok ok Structural and Thermal Simulation Constraint Beam Shell 1 Solid 1. Stress is infinite along the boundary of the surface/face. This information also applies to temperatures and fluxes that result from heat loads, convection conditions, and prescribed temperatures in Thermal. Strategy: Minimizing Singularities To minimize singularities, consider the following: • Use distributed loads and constraints whenever possible to avoid singular stress or displacement concentrations that could distort your results. Use the Total Load At Point option to distribute a point load over a surface or curve in a statically equivalent manner. If you cannot avoid singularities, use the Feature Isolation area of the AutoGEM Settings dialog box to create a set of small, transitional elements at the singular point, edge, or corner. • Sometimes, when trying to avoid element singularities, you impose too few constraints. In these cases, a run may end with an error message in the summary file indicating that your model is insufficiently constrained. For more information on how to address this condition, see Insufficiently Constrained Models. Singularities Mechanica Structure is based on the theory of linear elasticity, which is a useful approximation of physical reality. Linear elasticity allows solutions that have infinite values of displacement or stress. These solutions with infinite values are called singular elastic states and the locations where they occur are called singularities. At the location of a singularity and in the small area around the singularity, the theoretical elasticity solution is not a valid representation of physical reality because displacement and stress cannot be infinite. Outside the area of the singularity, the theoretical elasticity solution is valid. Structure attempts to represent the singular representation as accurately as possible using polynomial functions. Singularities cause edges in a model to require a high p-level for convergence, thus resulting in a longer solution time. Some of the most common locations where element singularities can occur include: • • • • at reentrant corners at point loads and constraints along line loads and constraints on solids at the interface between elements of different properties, materials, or element types 405 Structural and Thermal Simulation - Help Topic Collection To understand the causes of singularities, see Singularities and Loads or Singularities and Constraints. Problems with Properties Listed here are some problems with properties that you may find in Mechanica models. • Improper material properties — Sections of the model with material properties that are not physically realistic, or adjoining sections that have a difference in material properties that is too great may cause problems. There may be typographical errors in material properties. If you estimate any physical properties, then be sure to check how the estimates compare to the properties for other materials. One possible source of errors is an element with very flexible material properties in a model containing elements with much stiffer material. Improper spring stiffness, beam section, or shell thickness properties — If one shell is far thinner than other shells in the model, an error can occur. Check for omissions or typographical errors in these types of properties. Mass density properties of 0 for a modal analysis — Mass density must not be zero for modal analyses. Beam releases — If there are too many beam releases in the model, they may allow the model or parts of the model to move without resistance to some arbitrary load. You must specify beam releases such that the model is structurally stable. • • • Constraints and Loads on Compressed Geometry You can place a constraint or a load on a surface that will be compressed to a midsurface edge. Mechanica automatically transfers such a constraint or load from the original surface to the compressed midsurface edge. This transfer will occur for the following types of loads and constraints when you compress a solid to a midsurface: Original Surface Constrained Components Tx, Ty, Tz, Rx, Ry, Rz Tx, Ty, Tz Original Surface Load Total Load at Point Total Load Compressed Edge Constrained Components Tx, Ty, Tz, Rx, Ry, Rz Tx, Ty, Tz, Rx, Ry, Rz Compressed Edge Load Total Load at Point Total Load 406 Structural and Thermal Simulation Note: If your model has an interpolated surface load, Mechanica cannot automatically transfer the load to an edge. Therefore, if you attempt to compress a solid containing such a load, the attempt will fail, and Mechanica will delete the load. Thermal Boundary Conditions Guidelines for Thermal Boundary Conditions When defining thermal boundary conditions, be aware of the following: • • • The software considers locations at which you have not created prescribed temperatures, convection conditions, radiation loads, or heat loads to be insulated. The software determines the temperature at every location of your model for which you have not prescribed a temperature. You do not have to select a boundary condition set to run a transient thermal analysis. However, if no set is selected, you must select at least one load set for the analysis to be valid. Guidelines for Thermal Boundary Conditions for Geometry When you define thermal boundary conditions for geometry, keep the following points in mind: • Any point, vertex, curve, or surface to which you apply a boundary condition must be associated with at least one element. To check associations with geometry that will be meshed, click the appropriate icon on the model or select the boundary condition in the model tree. Mechanica highlights the icon and associated geometry. Note: If you create a convection conditions in FEM mode using a vertex as the point of application, Mechanica supresses that convection conditions when you switch from FEM mode to native mode. If you are working with prescribed temperatures applied to vertices, Mechanica does not suppress the prescribed temperature for mode switches. • • • • A thermal boundary condition defined at a point or on a curve can result in theoretically infinite stresses. See Handling Stress Concentrations for information on working around this problem. Any constrained curve constrains the edges, beams, or 2D shells that lie on that curve. Any constrained surface constrains the shells, solid faces, 2D solids, or 2D plates that lie on that surface. Any constrained edge constrains the beams and 2D shells that lie on that edge. 407 Structural and Thermal Simulation - Help Topic Collection • You should not create two different prescribed temperatures on two different curves that touch within the same constraint set. Doing so will result in a conflict between the two temperature constraints. Boundary Condition Sets Boundary Condition and Load Sets in Thermal Analyses When you are defining thermal analyses, keep in mind the following: • • • • • For both steady and transient thermal analyses, you do not have to select a load set. For a transient thermal analysis, you do not have to select a boundary condition set. If you do not select a boundary condition set, however, you must select one or more load sets for the analysis to be valid. For steady thermal analyses, you must select one boundary condition set. If you delete a boundary condition set or load set after you include it in an analysis, you are also deleting that set from the analysis. Even if you create a new set with the same name as the set you deleted, you must edit the analysis and reselect the set name. Otherwise, you can invalidate the analysis and any design studies in which you included the analysis. Guidelines for Thermal Boundary Condition Sets When defining thermal boundary condition sets, use the following guidelines: • • • • There is no limit to the number of boundary condition sets you can specify for your model. As you can specify only one boundary condition set for an analysis, make sure the set contains all the required boundary conditions for that analysis. See Boundary Condition and Load Sets in Thermal Analyses for more information. You are not required to select a boundary condition set to run a transient thermal analysis. However, if you do not select a boundary condition set, you must select at least one load set for the analysis to be valid. A thermal boundary condition set can include prescribed temperatures and/or convection conditions. When you define a boundary condition, you can: • • add the boundary condition to an existing boundary condition set create a new boundary condition set and enter a description If you click Cancel, you exit without creating either the thermal boundary condition or the boundary condition set. 408 Structural and Thermal Simulation If a boundary condition for one or more of the entities you selected already belongs to the boundary condition set, Mechanica prompts you to do one of the following: • • Click Yes to replace the existing boundary condition with a new one in the same set. Click No to retain the old boundary condition and cancel the new one. If you click No and want to create the new boundary condition without losing the old one, define the constraint again and select a different boundary condition set. Convection Conditions Use the convection boundary conditions to define a linear convective heat exchange condition for one or more geometric entities in Thermal. If you are working in the FEM mode, see Convection Conditions (FEM Mode). You can assign convection conditions to points, edges, curves, and surfaces. When you select Insert>Convection Condition, Mechanica displays the CONV COND menu. You use this menu to select the type of entity—point, edge/curve, or surface—you want to apply the convection condition to. After you select the entity type, the Convection Condition dialog box appears. This dialog box has the following fields: • • • Name — The name of the boundary condition. Member of Set — The name of the boundary condition set. You can select an existing boundary condition set from the drop-down list, or create a new set by clicking the New button to display the BC Set Definition dialog box. Entity — The name of the type of entity you chose. You can select appropriate geometry using the selector arrow and the normal selection methods. Once you complete the selection process, the software displays the name of the entity. Spatial Variation — Specifies whether the convection condition will be applied uniformly over the entity or whether it will vary spatially over the entity. External Data (not available for uniform spatial variation) — Provides needed information about the FNF file that you want to import. Convection Coefficient, h — Provides a value for the convection coefficient. You can obtain this value from empirical data or you can enter your own data. This area becomes inactive when you select External Conv Coefficient or External Conv Coef & Bulk Temp from the Spatial Variation drop-down menu. Bulk Temperature, Tb — Assigns a temperature for the fluid. This area becomes inactive when you select Ext Bulk Temperature or External Conv Coef & Bulk Temp from the Spatial Variation drop-down menu. Temporal Variation — Applies the convection condition as a function of time. This option includes a Time Dependent check box and an f(x) button, which opens either the Functions dialog box or the Function Definition dialog box. If you specify a temporal variation for the convection condition, Mechanica multiplies the bulk temperature you enter by the function you define—creating, in effect, a time-varying bulk temperature. 409 • • • • • Structural and Thermal Simulation - Help Topic Collection If you want to preview the convection coefficient or bulk temperature in an FNF file selected for import, click the Preview h or Preview Tb button. These buttons become active only when you are importing external data from an FNF file. When you accept the dialog box, Mechanica places a convection condition icon at each location you selected. After you create a convection condition, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a convection condition, Mechanica asks you for confirmation first. Background How Mechanica Calculates the Convective Heat Transfer Rate Mechanica calculates the convective heat transfer rate as follows: Q = h (Te – Tb) where Q is the convective heat transfer rate. h is the convection coefficient. Te is the entity temperature (the temperature of an entity such as a node or surface). Tb is the bulk temperature (the temperature of the fluid in contact with the entity). Ramping of Heat Loads and Convection Conditions In transient thermal analysis, Mechanica turns on any heat load or convection condition that is not equal to zero at the start of the analysis. Because its algorithm is adaptive, Mechanica sets the p-order to its maximum possible value to capture the instantaneous change in heat load or convection condition. The algorithm is more efficient if all heat loads and convection conditions are ramped from zero to their final value over some short period of time. You can use the mesh parameters and the material properties discussed below to estimate the time. The finite element method is only able to capture time scales of the order of 410 Structural and Thermal Simulation is the density, c is the specific heat, k is the conductivity, L is the largest where length scale of an element, and p is the p-order. Any time scale that is smaller than this causes errors. For example, if you enter a time-dependent heat load or bulk temperature that is a sine wave with a period much smaller than this value, the solution would have a large error. Therefore any ramp function must use a period at least as large as the local value of computed for the elements adjacent to the heat load or convection condition. A convection condition having a large Biot number can create a thin layer with large temperature gradients that is smaller than Mechanica can represent accurately. Mechanica defines the Biot number by where h is the convective heat transfer coefficient (also called film coefficient in Mechanica), k is the conductivity, and L is the largest length scale of an element. If the Biot number is much greater than 1, the solution can have a large error. You can reduce the error in the solution by ramping the bulk temperature from the initial condition of the model to its final value over a period of time larger than . You can use the local value of for the elements adjacent to the convection condition and in many cases get accurate results, as mentioned above. To model a time-dependent prescribed temperature, you can enter a convection condition with a large value of h and set the bulk temperature as a function of time equal to the desired prescribed temperature. A Biot number of 100 should be sufficient. The bulk temperature should not vary more rapidly than in order to avoid errors in the solution. Convection Conditions in Native Mode Convection Coefficient, h The convective heat transfer coefficient, h, relates the amount of heat transferred between a moving bulk fluid—liquid or gas—and a bounding surface. It is the constant of proportionality and is equal to the heat rate per unit area per temperature difference. Use only real numbers and be sure the system of units you are working in is consistent with the rest of the model. If you do not import an externally computed convection coefficient, you must specify a convection coefficient for the software to use. Using either empirical data or data of your own, enter a positive real number for the convection coefficient of the convection condition you are defining. 411 Structural and Thermal Simulation - Help Topic Collection Convection coefficient units depend on the entity you select and the model type, as noted in the following table: Model Type/Entity 3D: Point Curve, Edge, Beam Surface, Face, Shell 2D Axisymmetric: Point Curve, Edge, 2D Shell Surface, 2D Solid 2D Plane Strain: Point Curve, Edge, 2D Shell Surface, 2D Solid 2D Plane Stress Point Curve, Edge Surface, 2D Plate Heat/Time Per Degree Heat/Time Per Degree Per Unit Length Heat/Time Per Degree Per Unit Area Heat/Time Per Degree Per Unit Length Heat/Time Per Degree Per Unit Area Heat/Time Per Degree Per Unit Volume Heat/Time Per Degree Per Unit Length Heat/Time Per Degree Per Unit Area Heat/Time Per Degree Per Unit Volume Heat/Time Per Degree Heat/Time Per Degree Per Unit Length Heat/Time Per Degree Per Unit Area Units 412 Structural and Thermal Simulation Bulk Temperature, Tb If you do not import an externally computed bulk temperature, you must specify a bulk temperature for the software to use. Enter a real number for the bulk temperature of the convection condition you are defining. Time-dependent bulk temperatures (and time-dependent heat loads) are only relevant for transient thermal analysis. For steady-state thermal analysis, be aware of the following: • • Mechanica ignores time-dependent bulk temperatures. If all bulk temperatures are time-dependent and there are no prescribed temperatures, a steady-state thermal analysis cannot run because the model has no valid constraints. Using External Data External Data for Convection Conditions Use the External Data area of the Convection Condition dialog box to provide information about the external FNF file that contains information for import. This area of the dialog box is available for only the external options in the Spatial Variation pull-down menu. The External Data area contains the following options: • Reference Coordinate System — The data in the FNF file is interpreted with respect to the WCS by default. Use the selector arrow if you need to change the reference coordinate system from the WCS to a local Cartesian system so that the data in the FNF file maps correctly to your model. This reference is valid only for Cartesian coordinate systems. File — Use the selection button to browse for and select the name of the FNF file you want to import. • When you click OK, the software checks for problems with either the file name or the content of the FNF file. Guidelines for Importing External Temperature Fields • Before you import an external temperature, you must create a FEM Neutral Format file, which Mechanica uses to import your temperature load. The FEM Neutral Format file enables you to store an externally created temperature field and import it into Structure. For more information, see FEM Neutral Format File and Sample FNF File for External Temperature. Mechanica automatically copies the FEM Neutral Format file you create into a study directory. If you do not want this file in the study directory, you must set a config.pro option. For more information, see Configuration File Options. Mechanica extracts temperature data from the h-mesh Mechanica FEM Neutral Format file by finding the h-element that encompasses the point 413 • • Structural and Thermal Simulation - Help Topic Collection where the p-element temperature is desired, and performing a linear interpolation of the temperature at the h-element's corner nodes. If the pelement point is not inside any of the h-elements—for example, when the curved boundary of a p-element lies outside the h-mesh—Mechanica projects the point to an h-element face, edge, or node and performs a three, two, or one-point interpolation. When entire elements of the p-mesh lie outside the h-mesh, Mechanica still projects the points onto the outer faces of the h-mesh. As the distance increases, Mechanica may not project the point onto the closest face, but instead onto the first orthogonal projection it finds. • • • • Your imported temperature load must contain the connectivity of a linear solid element mesh, node locations, and temperature values at the nodes. If the temperature load mesh is not consistent, Mechanica displays an error message. If you defined the temperature load for part of your model, Mechanica displays an error message indicating that it will calculate temperature through extrapolation for parts of the model. If you performed a design study for your model that included size or shape changes, you must make sure the temperature field is consistent for all the design variations included in the study. When you import an external temperature load, you also import the model's orientation. Creating FNF Files for External Loads and Constraints FEM Neutral Format (FNF) files, with the extension .fnf, are organized into sections. When you are creating an FNF file that will be used to import an external load or constraint, you need only five of these sections. Each section describes its own class of objects. The order of sections in the FNF file is critical, since information from the earlier defined sections may be required in subsequent sections. Note: FNF files are backward-compatible. Create the following sections in an FNF file to import an external load or constraint: • HEADER — general information about the file and the model. This section can contain the following instructions: o TITLE — describes the name of your model o STATISTICS — provides information about the number of element types, coordinate systems, materials, element properties, nodes, and elements in your model ELEM_TYPES — definition of element types MESH — definition of the model's nodes and elements • • 414 Structural and Thermal Simulation • LOADS — description of applied constraint cases, loads, and boundary conditions The following table lists instructions required for importing external loads and constraints, their standard abbreviations, and the sections in which they may appear: Instruction Names STATISTICS ELEM_TYPE NODE ELEM CON_CASE LOAD_TYPE LOAD Abbreviation STT ETP ND EL CC LTP LD Section Name HEADER ELEM_TYPE MESH MESH LOADS LOADS LOADS Each section must start with the following text string: %START_SECT : SECTION_NAME Each section must end with the following text string: %END_SECT For more information about FNF files, see FEM Neutral Format File. 415 Structural and Thermal Simulation - Help Topic Collection Sample FNF File for External Convection Conditions Following is a sample FNF file for external convection conditions. #PTC_FEM_NEUT 3 #DATE 18-Sep-01 09:58:38 %START_SECT : HEADER %TITLE : B2 %STATISTICS : 1 0 1 1 26 24 %END_SECT %START_SECT : ELEM_TYPES %ELEM_TYPE 1 DEF : SHELL QUAD LINEAR 4 4 2 %ELEM_TYPE 1 EDGE : 1 1 2 %ELEM_TYPE 1 EDGE : 2 2 3 %ELEM_TYPE 1 EDGE : 3 3 4 %ELEM_TYPE 1 EDGE : 4 1 4 %ELEM_TYPE 1 FACE : 1 1 2 3 4 %ELEM_TYPE 1 FACE : 2 1 4 3 2 %END_SECT %START_SECT : MESH %NODE 1 DEF : -0.5 0.5 -0.5 %NODE 2 DEF : -0.5 -0.5 -0.5 %NODE 3 DEF : 0.5 0.5 -0.5 %NODE 4 DEF : 0.5 -0.5 -0.5 %NODE 5 DEF : -0.5 0 -0.5 %NODE 6 DEF : 0 -0.5 -0.5 %NODE 7 DEF : 0.5 0 -0.5 %NODE 8 DEF : 0 0.5 -0.5 %NODE 9 DEF : 0 0 -0.5 %NODE 10 DEF : -0.5 0.5 0.5 %NODE 11 DEF : -0.5 -0.5 0.5 %NODE 12 DEF : 0.5 0.5 0.5 %NODE 13 DEF : 0.5 -0.5 0.5 %NODE 14 DEF : -0.5 0 0.5 %NODE 15 DEF : 0 0.5 0.5 %NODE 16 DEF : 0.5 0 0.5 %NODE 17 DEF : 0 -0.5 0.5 %NODE 18 DEF : 0 0 0.5 %NODE 19 DEF : -0.5 0.5 0 %NODE 20 DEF : -0.5 -0.5 0 %NODE 21 DEF : -0.5 0 0 %NODE 22 DEF : 0.5 -0.5 0 %NODE 23 DEF : 0 -0.5 0 %NODE 24 DEF : 0.5 0.5 0 %NODE 25 DEF : 0.5 0 0 %NODE 26 DEF : 0 0.5 0 %ELEM 1 DEF : 1 1 1 9 6 2 5 %ELEM 2 DEF : 1 1 1 7 4 6 9 %ELEM 3 DEF : 1 1 1 8 9 5 1 %ELEM 4 DEF : 1 1 1 3 7 9 8 416 Structural and Thermal Simulation %ELEM 5 DEF : 1 1 1 18 16 12 15 %ELEM 6 DEF : 1 1 1 14 18 15 10 %ELEM 7 DEF : 1 1 1 17 13 16 18 %ELEM 8 DEF : 1 1 1 11 17 18 14 %ELEM 9 DEF : 1 1 1 21 14 10 19 %ELEM 10 DEF : 1 1 1 5 21 19 1 %ELEM 11 DEF : 1 1 1 20 11 14 21 %ELEM 12 DEF : 1 1 1 2 20 21 5 %ELEM 13 DEF : 1 1 1 23 17 11 20 %ELEM 14 DEF : 1 1 1 6 23 20 2 %ELEM 15 DEF : 1 1 1 22 13 17 23 %ELEM 16 DEF : 1 1 1 4 22 23 6 %ELEM 17 DEF : 1 1 1 25 16 13 22 %ELEM 18 DEF : 1 1 1 7 25 22 4 %ELEM 19 DEF : 1 1 1 24 12 16 25 %ELEM 20 DEF : 1 1 1 3 24 25 7 %ELEM 21 DEF : 1 1 1 26 15 12 24 %ELEM 22 DEF : 1 1 1 8 26 24 3 %ELEM 23 DEF : 1 1 1 19 10 15 26 %ELEM 24 DEF : 1 1 1 1 19 26 8 %END_SECT %START_SECT : LOADS %LOAD_TYPE 1 DEF : CONVECTION NODE VECTOR_2 %CON_CASE 1 DEF : TestData1 %LOAD 1 DEF : 1 1 %LOAD 1 VAL : 1 0.6 0.23 %LOAD 1 VAL : 2 0 0 %LOAD 1 VAL : 3 0.85 0.68 %LOAD 1 VAL : 4 0.25 0.45 %LOAD 1 VAL : 5 0.3 0.115 %LOAD 1 VAL : 6 0.125 0.225 %LOAD 1 VAL : 7 0.55 0.565 %LOAD 1 VAL : 8 0.725 0.455 %LOAD 1 VAL : 9 0.425 0.34 %LOAD 1 VAL : 10 0.75 0.55 %LOAD 1 VAL : 11 0.15 0.32 %LOAD 1 VAL : 12 1 1 %LOAD 1 VAL : 13 0.4 0.77 %LOAD 1 VAL : 14 0.45 0.435 %LOAD 1 VAL : 15 0.875 0.775 %LOAD 1 VAL : 16 0.7 0.885 %LOAD 1 VAL : 17 0.275 0.545 %LOAD 1 VAL : 18 0.575 0.66 %LOAD 1 VAL : 19 0.675 0.39 %LOAD 1 VAL : 20 0.075 0.16 %LOAD 1 VAL : 21 0.375 0.275 %LOAD 1 VAL : 22 0.325 0.61 %LOAD 1 VAL : 23 0.2 0.385 %LOAD 1 VAL : 24 0.925 0.84 %LOAD 1 VAL : 25 0.625 0.725 %LOAD 1 VAL : 26 0.8 0.615 %END_SECT %START_SECT : ANALYSIS %SOLUTION 1 DEF : THERMAL 417 Structural and Thermal Simulation - Help Topic Collection %SOLUTION 1 CON_CASES : 1 %END_SECT %END Spatial Variation for Convection Conditions The Spatial Variation pull-down menu on the Convection Condition dialog box allows you to choose whether to apply the convection condition uniformly or as a condition that varies across the selected geometry. The menu offers you the following options: • Uniform — Use this option to apply a convection coefficient and bulk temperature that are uniform over the entity. Additionally, the following options are available for shell and solid surfaces in 3D models: • • • External Conv Coefficient — Imports a convection condition FNF file that contains an externally calculated or measured convection coefficient that can vary spatially over the selected surface(s). External Bulk Temperature — Imports a convection condition FNF file that contains an externally calculated or measured bulk temperature that can vary spatially over the selected surface(s). External Conv Coef & Bulk Temp — Imports a convection condition FNF file that contains an externally calculated or measured convection coefficient and bulk temperature, both of which can vary spatially over the selected single or multiple surfaces. For additional information, see the following: • • Creating FNF Files for External Loads and Constraints Sample FNF File for External Convection Conditions To Define Convection Conditions for Points, Edges, and Curves You can use the following steps to define convection conditions for points, edges, and curves. FEM mode supports placement of convection conditions only on 3D surfaces. 1. Select Insert>Convection Condition. 2. Select Point or Edge/Curve from the CONV COND menu. The Convection Condition dialog box appears. 3. Click model. under the geometric reference to define the references on your 418 Structural and Thermal Simulation If you select Point as your geometric type, the SIM SELECT menu appears, enabling you to select single points, vertices, features of points, or patterns of points. o If you select Edge/Curve, use Pro/ENGINEER selection methods to select one or more edges or curves. 4. Type a value for the convection coefficient, h. o Use real numbers only and ensure that the system of units you are working in is consistent with the rest of the model. 5. Type a value for the bulk temperature, Tb. If you do not specify a temperature, the software assumes a default of 0. 6. If you want the bulk temperature to be time-dependent, select the Time Dependent check box under Temporal Variation. 7. If you want to define more convection conditions, repeat applicable preceding steps until you have defined all convection conditions. 8. Click OK to accept the definition of the convection condition(s). To Define Convection Conditions for 3D Surfaces Use the following steps to define convection conditions for surfaces in Mechanica. If you are in FEM mode, see To Define Convection Conditions in FEM Mode. 1. Select Insert>Convection Condition. 2. Select Surface from the CONV COND menu. The Convection Condition dialog box appears. 3. Click to select the 3D surfaces to which you will apply the convection condition. 4. Select one of the following options from the Spatial Variation pull-down menu: o Uniform o External Conv Coefficient o External Bulk Temperature o External Conv Coef & Bulk Temp To Create a Time-Dependent Convection Condition 1. If you want bulk temperature to be time-dependent, select the Time Dependent check box under Temporal Variation. This displays the f(x) button and input field. 419 Structural and Thermal Simulation - Help Topic Collection 2. Click the f(x) button. This displays the Functions dialog box or the Function Definition dialog box. Convection Conditions in FEM Mode Convection Conditions (FEM Mode) Use the convection boundary conditions in the Thermal FEM mode to define a linear convective heat exchange condition for one or more surfaces. After you select Insert>Convection Condition, the Convection Condition dialog box appears with the following items: • • • Name — The name of the boundary condition. Member of Set — The name of the boundary condition set. You can select an existing boundary condition set from the drop-down list, or create a new set by clicking the New button to display the BC Set Definition dialog box. References — The single or multiple surfaces that you want to constrain. If you selected the surfaces before you entered the dialog box, your selections appear next to the selector arrow. Otherwise, click the selector arrow and use the normal selection methods to select single or multiple surfaces. Convection Coefficient — Specifies whether the convection coefficient will be applied uniformly over the entity or whether it will vary spatially as a function of coordinates. Also contains an entry box for a value for the convection coefficient. You can obtain this value from empirical data or you can enter your own data. Bulk Temperature — Specifies whether the bulk temperature will be applied uniformly over the entity or whether it will vary spatially as a function of coordinates. Also contains an entry box for a value for the bulk temperature. You can obtain this value from empirical data or you can enter your own data. • • When you accept the dialog box, Mechanica places a convection condition icon at each location you selected. After you create a convection condition, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a convection condition, Mechanica asks you for confirmation first. To Define Convection Conditions in FEM Mode 1. Select Insert>Convection Condition. The Convection Condition dialog box appears. 2. If you did not select geometry before entering the dialog box, click References to specify the 3D surface(s) to which you will apply the convection condition. 3. Choose a variation for the convection coefficient. 420 under Structural and Thermal Simulation 4. If you chose Function Of Coordinates in the preceding step, use the f(x) button to define how you want the convection coefficient to vary spatially across the selected surface(s). 5. Type a value for the convection coefficient. Use real numbers only and ensure that the system of units you are working in is consistent with the rest of the model. 6. Choose a variation for the bulk temperature. 7. If you chose Function Of Coordinates in the preceding step, use the f(x) button to define how you want the bulk temperature to vary spatially across the selected surface(s). 8. Type a value for the bulk temperature. If you do not specify a temperature, the software assumes a default of 0. Prescribed Temperatures Prescribed Temperature Conditions Use the Insert>Prescribed Temperature command in Thermal and FEM mode Thermal to define a temperature boundary condition for one or more geometric or model entities. A prescribed temperature is a thermal boundary condition that limits the temperature of your model. See Guidelines for Thermal Boundary Conditions and Guidelines for Thermal Boundary Conditions for Geometry. When you select Insert>Prescribed Temperature, the Prescribed Temperature dialog box appears. The dialog box has the following fields: • • • Name — The name of the boundary condition. Member of Set — The name of the boundary condition set. You can select an existing boundary condition set from the drop-down list, or create a new set by clicking the New button to display the BC Set Definition dialog box. References — The drop-down list includes the following geometric entities. You can select the geometry for these references before you enter the dialog box, or use the selector arrow and the normal selection methods to choose the desired geometry. o Surface(s) — You can select individual surfaces, several surfaces, quilts, or part boundaries. o Edge(s)/Curve(s) — You can select edges, curves, or composite curves. o Point(s) — You can select single points, vertices, point features, or patterns of points. Temperature — Specify values for a prescribed temperature as follows: o Value — Enter any real number for the prescribed temperature, arithmetic expression, or Pro/ENGINEER parameter. For points and vertices, you can assign only a uniform temperature. o Advanced — Expands the dialog box to display the Spatial Variation drop-down list. For edges, curves, surfaces, 2D plates, and 2D solids, you can assign a spatially varying prescribed temperature. 421 • Structural and Thermal Simulation - Help Topic Collection • Preview — Adds a series of arrows to your model showing the location and distribution of the prescribed temperature condition. After you accept the values in dialog box, the software places a prescribed temperature icon at each location you selected. After you create a prescribed temperature, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a prescribed temperature, the software asks you for confirmation first. Spatially Varying Temperatures You can specify how you want to spatially vary the prescribed temperature you are creating. See Guidelines for Spatially Varying Temperatures. You can select one of three options for spatial variation on the Prescribed Temperature dialog box: • Uniform — Use this option to apply a uniform prescribed temperature over the selected entities. The prescribed temperature has no spatial variation. You can enter any real number for the prescribed temperature for the entities you selected. Interpolated Over Entity — Not available in FEM mode. Function of Coordinates — Use the Functions dialog box to define a mathematical expression for the spatial variation. • • Guidelines for Spatially Varying Temperatures You can apply spatially varying temperatures only in the following cases: • • You are running a steady-state thermal analysis. You are running a transient thermal analysis when the initial condition of that analysis is a steady-state analysis containing the same spatially varying prescribed temperature. When you are applying spatially varying temperatures, remember that changes in temperature throughout an entity must be smooth. Across adjacent entities, temperatures must be equal and continuous where the entities meet. In addition, temperature compatibility is needed in the following situations: • • • If you have a spatially varying temperature on a curve, the end points of that curve cannot have independent temperatures. If you have a spatially varying temperature on a surface, the curves on the boundary of that surface cannot have independent temperatures. You must define a continuous temperature on the interior of adjacent entities. 422 Structural and Thermal Simulation Keep in mind the following points when defining functions: • • For table functions, Mechanica interprets angles as degrees. Domain bounds for the theta value must be between –180 and 180 degrees. Domain bounds for the phi value must be between zero and 180 degrees. For symbolic functions, Mechanica interprets angles as radians. Make sure that the domain bounds for these angles are in the following ranges: the theta value must be between – and and the phi value must be between zero and . For more information about functions, see Functions Dialog Box. Interpolated Over Entity Use this option to vary a prescribed temperature linearly, quadratically, or cubically along the entity you selected. You can use this option only if you selected a single entity for this prescribed temperature. Note: You cannot define an interpolation for a 3D solid. When you select Interpolated Over Entity, the Define button appears on the dialog box. When you select this button, the Interpolation Over Entity dialog box appears, which enables you to: • • add a new interpolation review or remove an existing interpolation The interpolation you create is associated with the prescribed temperature and the entity. Interpolation Over Entity Use the Interpolation Over Entity dialog box to add, preview, or remove interpolation points, and to enter and edit a value for each point. You can use from two to four points to define an interpolation. The number of points you select depends on whether you are selecting a curve or edge (usually two points) or a surface or face (usually four points). 423 Structural and Thermal Simulation - Help Topic Collection Mechanica selects default interpolation points for some entities as follows: Entity Default Interpolation Points endpoints open curves, edges, beams, 2D shells shells, 2D plates, 2D solids, faces surfaces corners none If you want interpolation points that are different from the default points, you can delete the default points and create new ones. When planning interpolated prescribed temperatures, be aware that: • Each value is a scale factor. Mechanica multiplies the Temperature value you specify on the Prescribed Temperature dialog box by the interpolation value at a given location to determine the prescribed temperature vector at that location. At least one of the points should have a value other than zero. If you enter interpolation point values before entering the prescribed temperature value on the Prescribed Temperature dialog box, Mechanica enters a default value of 1 for Temperature. The number of interpolation points you select determines the functional form of the interpolation. • • • Function of Coordinates Use this option to apply a prescribed temperature that is a function of the current coordinate system (WCS or UCS). Alternatively, you can create a coordinate system whose X axis is aligned with the entity over which you are placing the spatially varying temperature. You can select one or more entities on which to apply this prescribed temperature. When you select Function Of Coordinates, the f(x) button and option menu appear on the dialog box. Click the f(x) button and the Functions dialog box (native mode) or Functions dialog box (FEM mode) appears. You can use this form to create, copy, edit, or delete a function. To Define a Prescribed Temperature 1. Select Insert>Prescribed Temperature or click . The Prescribed Temperature dialog box appears. 2. Enter a descriptive name, or accept the default name. 424 Structural and Thermal Simulation 3. Select the desired boundary condition set from the Member of Set dropdown list. 4. If you want to create a new boundary condition set, click the New button to display the BC Set Definition dialog box. Enter a name and optional description for a new constraint set. 5. If you did not select geometric entities as references before you opened the dialog box, select one of these References from the drop-down list: • Surface(s) • Edge(s)/Curve(s) • Point(s) 6. Click and use the normal methods to select a reference. 7. If you want to define how the temperature varies across the geometry, click the Advanced button and select one of the options from the Spatial Variation drop-down list. 8. Enter the prescribed temperature in the Value entry box. You can enter real numbers, use an expression, or enter a parameter name. Be sure the system of units you are working in is consistent with the one that you used to define the current model. 9. Click the Preview button to see a graphical representation of the prescribed temperature on your mode. 10. Click OK to accept your definition and close the dialog box. Radiation Conditions (FEM Mode) Use radiation boundary conditions in Thermal FEM mode to define the emission of heat from a model. You apply these boundary conditions to surfaces. When you select Insert>Radiation Condition, the Radiation Condition dialog box appears with the following items: • • • • Name — Enter a descriptive name or accept the default name. Member Of Set — The name of the boundary condition set. You can select an existing boundary condition set from the drop-down list, or create a new set by clicking the New button to display the BC Set Definition dialog box. References — You can select one or more surfaces or a part boundary before you enter the dialog box, or use the selector arrow and the normal selection methods to choose the desired geometry. Emissivity — Use this area to specify one of these types of Spatial Variation for the selected surface: o Uniform — Enter a real-number value between 0 and 1. The software applies this value uniformly across the selected surface. o Function Of Coordinates — Open the Functions dialog box to define a mathematical expression. You must also enter a real number in the Value entry box. The software uses the function as a scale factor for the value. Ambient Temperature — Use this area to specify one of these types of Spatial Variation for the local environment: o Uniform — Enter a real-number value for the ambient temperature of the surroundings. • 425 Structural and Thermal Simulation - Help Topic Collection o Function Of Coordinates — Open the Functions dialog box to define a mathematical expression. You must also enter a real number in the Value entry box. The software uses the function as a scale factor for the value. The software places a radiation icon at each location you selected. Note: If you plan to analyze your model using the ANSYS solver, be aware that the radiation boundary condition will not be included. Mechanica does not output radiation to ANSYS. After you create a radiation condition, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a radiation condition, the software asks you for confirmation first. To Define a Radiation Condition 1. Select Insert>Radiation Condition, or click The Radiation Condition dialog box appears. 2. Enter a descriptive name or accept the default name. 3. Select the desired boundary condition set from the Member of Set dropdown list. 4. If you want to create a new boundary condition set, click the New button to display the BC Set Definition dialog box. Enter a name and optional description for a new constraint set. 5. If you did not select surfaces before entering the dialog box, click under References and use the normal selection methods to select one or more surfaces on your model. 6. Select one of the following to specify the Spatial Variation for the Emissivity: • • Uniform Function of Coordinates — Click f (x) to open the Functions dialog box. . 7. Enter a real number in the Value entry box. 8. Select one of the following to specify the Spatial Variation for the Ambient Temperature: • Uniform • Function of Coordinates — Click f (x) to open the Functions dialog box. 9. Enter a real number in the Value entry box. 10. Click OK to accept your definition and close the dialog box. 426 Structural and Thermal Simulation To Use External Conv Coefficient Spatial Variation for 3D Models This procedure assumes that you are in the Convection Condition dialog box, that you selected Surface as the entity type, and that you selected External Conv Coefficient for Spatial Variation. 1. If you want your reference coordinate system to be a local Cartesian system rather than the default WCS of the FNF file, do the following: o o Under Reference Coordinate System, click . Select the local Cartesian coordinate system that you want to be the reference coordinate system for the data in the FNF file. This reference is valid only for Cartesian coordinate systems. 2. Click . Locate and select the name of the file you want to import. 3. If you want to preview the convection coefficient, click the Preview h button. If the preview does not produce the expected results, check to make sure that the reference coordinate system is correct. 4. Type a value for the bulk temperature, Tb. 5. If you want the bulk temperature to be time-dependent, select the Time Dependent check box under Temporal Variation. 6. Click OK to accept the definition of the convection condition. The software performs a simple test on the FNF file to check that it has a mesh and the required load. To Use External Conv Coef & Bulk Temp Spatial Variation for 3D Models This procedure assumes that you are in the Convection Condition dialog box, that you selected Surface as the entity type, and that you selected External Conv Coef & Bulk Temp for Spatial Variation. 1. If you want your reference coordinate system to be a local Cartesian system rather than the WCS, do the following: o o Under Reference Coordinate System, click . Select the local Cartesian coordinate system that you want to be the reference coordinate system for the data in the FNF file. This reference is valid only for Cartesian coordinate systems. 2. Click . Locate and select the name of the file you want to import. 3. If you want to preview the convection coefficient, click the Preview h button. 4. If you want to preview the bulk temperature, click the Preview Tb button. If either preview does not produce the expected results, check to make sure that the reference coordinate system is correct. 5. If you want bulk temperature to be time-dependent, select the Time Dependent check box under Temporal Variation. 6. Click OK to accept the definition of the convection condition. 427 Structural and Thermal Simulation - Help Topic Collection The software performs a simple test on the FNF file to check that it has a mesh and the required load. To Use Uniform Spatial Variation for 3D Models This procedure assumes that you are in the Convection Condition dialog box and that you selected Uniform for Spatial Variation. If you are working in FEM mode, see To Define Convection Conditions in FEM Mode. 1. Type a value for the convection coefficient, h. Use real numbers only and ensure that the system of units you are working in is consistent with the rest of the model. 2. Type a value for the bulk temperature, Tb. If you do not specify a temperature, the software assumes a default of 0. 3. If you want the bulk temperature to be time-dependent, select the Time Dependent check box under Temporal Variation. 4. If you want to define more convection conditions, repeat applicable preceding steps until you have defined all constraints. 5. Click OK to accept the definition of the convection condition(s). To Use External Bulk Temperature Spatial Variation for 3D Models This procedure assumes that you are in the Convection Condition dialog box, that you selected Surface as the entity type, and that you selected External Bulk Temperature for Spatial Variation. 1. If you want your reference coordinate system to be a local Cartesian system rather than the WCS, do the following: o o Under Reference Coordinate System, click . Select the local Cartesian coordinate system that you want to be the reference coordinate system for the data in the FNF file. This reference is valid only for Cartesian coordinate systems. 2. Click . Locate and select the name of the file you want to import. 3. If you want to preview the bulk temperature, click the Preview Tb button. If the preview does not produce the expected results, check to make sure that the reference coordinate system is correct. 4. Type a value for the convection coefficient, h. 5. If you want bulk temperature to be time-dependent, select the Time Dependent check box under Temporal Variation. 6. Click OK to accept the definition of the convection condition. 428 Structural and Thermal Simulation The software performs a simple test on the FNF file to check that it has a mesh and the required load. Variations for Convection Conditions in FEM Mode The following variations are available for Convection Coefficient and Bulk Temperature on the Convection Condition dialog box in FEM mode. • • Uniform — Applies a convection coefficient and bulk temperature that are uniform over the entity. Function of Coordinates — Use this option if you want the convection condition to vary spatially over the selected single or multiple surfaces. When you choose this option, the f(x) button appears, which opens either the Functions dialog box or the Function Definition dialog box. Understanding Thermal Boundary Condition Sets When you create a boundary condition in Thermal, the software adds it to a boundary condition set (BC set). A BC set is a collection of boundary conditions that act together, and at the same time, on your model. For more information, see Guidelines for Thermal Boundary Condition Sets. You can manage your BC sets with the BC Sets dialog box. When you select the Properties>Boundary Condition Sets command, this dialog box appears with the following buttons: • New — Opens the BC Set Definition dialog box. Enter a name and optional description for the new boundary condition set. Note: You can also access the BC Set Definition dialog box by clicking the New button in the Member of Set area on the Prescribed Temperature, Convection Condition, and Radiation Condition dialog boxes. • • • • Copy — Creates a copy of the highlighted boundary condition set and adds it to the list. Edit — Opens the BC Set Definition dialog box with the information you used to specify the highlighted boundary condition set. Delete — Removes the highlighted boundary condition set. Description — Displays the optional description you entered when you created the boundary condition set. If you want the flexibility of treating each of your boundary conditions separately, use a unique name and set name for each boundary condition. However, remember that a thermal analysis can only use one boundary condition set. 429 Structural and Thermal Simulation - Help Topic Collection Heat load and BC sets provide a logical means of organizing your modeling entities so you can define analyses effectively and clearly. A carefully considered approach to heat load and BC set creation simplifies heat load and boundary condition selection when defining your analyses. Although the software permits you to create each heat load and boundary condition as a separate heat load set or BC set, you can reduce the number of selections you need to make for analysis definition by grouping your heat loads and boundary conditions into sets. Structure Loads About Loads Constraints and loads define the real-world environment you expect your model to encounter. Mechanica simulates the behavior of your model under loads you define when performing standard analyses and sensitivity studies for your model. Your model's optimal shape and mass can also depend on the loads you define. You can define loads on your model through the menu structure, the Model Tree, or through relations functions. For structural analysis, a load is a force, moment, pressure, acceleration, velocity, or temperature that you apply to a portion of your model. For thermal analysis, a load is a heat condition applied to a portion of your model. About Structure Loads You can choose from several different distribution and spatial variation methods when applying the structure loads. You can tailor the load to accurately simulate the true load conditions. For example, the spatial variation options enable you to specify linear variations or variations that are a function of an equation you define. The way you load your model depends on whether you are working in Structure or Thermal. For Mechanica to perform most types of analysis, you must load at least one area of your model. You can group the loads into load sets. See Guidelines for Structure Loads or Guidelines for Load Sets for more information. Although each Mechanica load type requires a slightly different definition method, there are several factors that govern all loads. You can create the following types of Structure loads, depending on your model type: • • • • • • force and moment loads bearing loads — not available in FEM mode centrifugal loads gravity loads pressure loads temperature loads 430 Structural and Thermal Simulation You can apply temperature results from a Thermal analysis as a temperature load. If you have a 2D model, and you want to associate loads with a UCS, the UCS must meet the following criteria: • • The UCS Z axis must be parallel to the WCS Z axis. The UCS origin must lie in the WCS XY plane. If you have run an analysis in Mechanism Design, you can also transfer loads to Structure. You can create loads by selecting the appropriate command on the Insert menu, or by using object action or toolbar buttons. After you create a load, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a load, Mechanica asks you for confirmation first. You can also troubleshoot loads, control load icon visibility, place loads on layers, and review resultant loads. Relations Functions for Loads and Constraints Use the Pro/ENGINEER Relations command to use functions in Mechanica and FEM mode. You can use either of these functions on the left or right side of a relation: • • sim_load_value() — for access to load and constraint values sim_mc_value() — for access to mesh control values On the left side of a relation, use the function to set a value. On the right side, use it to get a value. For example, if you define a point load, Load1, with FX=100, and if you want another load, Load2, which may have been defined with different values, to have the same value for X as Load1, you can define a relation as follows: sim_load_value("Load2","X") = sim_load_value("Load1","X") If you edit Load2, you can see that X is now defined as 100. Any change to Load1 will affect Load2 equally. 431 Structural and Thermal Simulation - Help Topic Collection The sim_load_value function has an optional second argument that defines the load component for vector or force and moment loads. When this command is used for constraints, it only works for enforced displacements on both sides of the relation. This argument can have the following case-insensitive values: Loads Cartesian X Y Z MX MY MZ Constraints Cartesian Cylindrical Spherical Convection Conditions CONVCOEFF AMBTEMP Radiation Cylindrical R THETA Z MR MTHETA MZ Spherical R THETA PHI MR MTHETA MPHI Magnitude MAGNITUDE DX DY DZ RX RY RZ DR DTHETA DZ RR RTHETA RZ DR DTHETA DPHI RR RTHETA RPHI EMISSIVITY AMBTEMP Load Basics Although each Mechanica load type requires a slightly different definition method, there are several factors that govern all loads. As you prepare to add loads to your model, bear the following points in mind: • When you apply loads, Mechanica associates the loads with part geometry. In the case of compressed geometry, Mechanica can automatically transfer some loads from an original surface to a compressed edge. However, it is preferable 432 Structural and Thermal Simulation • to assign loads directly to curves if you know that you will compress the geometry. Mechanica supports a variety of loads. In terms of how you apply these loads to your model, there are two basic load categories—entity loads and body loads. An entity load is a load that you define for specific geometric entities in your model, such as curves or surfaces. Forces and moments are examples of entity loads. A body load is a load that you apply to your model as a whole. Gravity is an example of a body load. Typically, you can only use one body load per load set. For assemblies, you may have several independent bodies in your model. When applying a body load to an assembly, Mechanica places the load on all bodies in the model. When loading an assembly, be aware that you must load all independent bodies in the assembly if the analysis you plan to run requires loads. If you do not add loads for all bodies in the model, Mechanica is unable to run the analysis. • You can apply a load to a single geometric entity or to multiple entities. When you apply a load to multiple entities, Mechanica does not allow you to mix entity types. For example, if you specify a point as the first entity, all remaining entities in the load must also be points. In the case of multiple entities, Mechanica associates the entities by virtue of the fact that they share a load. Thus, you cannot modify or delete the load for each entity individually. Further, deleting any of the entities associated with the load eliminates the load for the other associated entities. • • • In general, you should plan the placement of your loads according to the model type. For example, if you are working with a solid model, you should try to place your loads on surfaces or surface regions rather than points or curves. With shell models, you should try to place your loads on curves, surfaces, or surface regions, depending on the load type. Although you can place loads on other entity types, this placement is not always optimal. Mechanica assumes the load values you enter are consistent with your principal system of units. Mechanica places many loads using coordinate locations. The way Mechanica expresses coordinate directions depends on the current coordinate system's type, whether that coordinate system is the WCS or one you selected during load definition. The following is a chart that defines the coordinate nomenclature for each coordinate system type: Cartesian X Y Z Cylindrical R T Z Spherical R T P • When entering load values in Mechanica, use real numbers. You use the sign of the value to express directionality relative to the coordinate axis for which 433 Structural and Thermal Simulation - Help Topic Collection you are defining a load component. For heat loads, you use the sign to indicate whether a loaded entity is a heat source or heat sink. If you do not enter a value for a load component, magnitude, or direction, Mechanica assumes a default of 0 for that aspect of the load. For example, if you leave the Force X field blank for a force load, Mechanica assumes the load has no X component. You can also use expressions as load values. Your expression can include real numbers, arithmetic operators, and Pro/ENGINEER parameter names. • If you apply a load to a surface by selecting the surface with Box Select or Part Boundary, and Mechanica later creates a new surface due to a parameter change, the software does not automatically apply the existing load to the new surface. Guidelines for Structure Loads Before you add loads to your model, be sure you have the geometry and references you need already in place. Pay particular attention to the following items: • • • Names — Use names that uniquely and clearly identify the objective, placement, or other key characteristics of the load. If you use the default names, you or other users may have trouble distinguishing the loads later. Geometry Coordinate systems — If you plan to make a structural load relative to any coordinate system other than the WCS, you need to have that coordinate system in place or you can create it as you work. You also need to make that coordinate system current. For more information, see About Coordinate Systems. Datum points Regions Shell models — If you plan to load a shell model surface, region, curve, or point that Mechanica may compress during analysis, see Modeling Entities and Idealizations to learn about how Mechanica processes loads placed on these geometry types. Placing loads on a cylindrical surface — When you apply a load on a cylindrical surface, such as a hole, the load is placed on both surfaces that form the cylinder. • • • • Guidelines for Load Sets Understanding Load Sets Every load that you add in the software is part of a load set. A load set is a collection of loads that act together on your model. Load sets cannot contain constraints. 434 Structural and Thermal Simulation You can manage your load sets with the Properties>Load Sets command. When you select this command, the Load Sets dialog box appears with the following items: • New — Opens the Load Set Definition dialog box. Enter a name and optional description for the new load set. Note: You can also access the Load Set Definition dialog box by clicking the New button in the Member of Set area of the Force/Moment Load, Pressure Load, Gravity Load, Centrifugal Load, Global Temperature Load, or Structural Temperature Load dialog boxes. • • • • Copy — Copies the selected load set and adds to the list in the Load Sets dialog box. The new load set includes copies of the same loads as the original load set. Edit — Opens the Load Set Definition dialog box to enable you to modify any information you used to specify the highlighted load set. Delete — Removes the highlighted load set. Description — Displays the optional description that you entered when you created the load set. If you want the flexibility of treating each of your loads or constraints separately, use a unique load and load set name for each load or constraint. Load and constraint sets provide a logical means of organizing your modeling entities so that you can define analyses effectively and clearly. A carefully-considered approach to load and constraint set creation simplifies load and constraint selection when defining your analyses. Although you are free to create a separate load or constraint set for each of your modeling entities, you can greatly reduce the number of selections you need to make when defining your analyses by grouping your loads and constraints into sets. For more information, see Guidelines for Load Sets. Guidelines for Load Sets If you need more information on what a load set is and why you should group your loads, see Understanding Load Sets. When you create structural or heat load sets, use the following guidelines: • • • • Use names that are 32 characters or fewer. You can use alphanumeric characters and underbars. Names must start with alphabetic characters. The software will not permit you to use a name already used for another load, constraint, or property set. Use names that uniquely and clearly identify the objective, placement, or other key characteristic of the set. If you use the default names, you or other users may have trouble distinguishing the sets later. You can include as many different entities and types of loads as you want within a single load set, with the exception of loads that affect the entire 435 Structural and Thermal Simulation - Help Topic Collection • • • • model. You can only include one centrifugal load, gravity load, MEC/T temperature load, or global temperature load per load set. There is no limit to the number of load sets you can create or the number of loads you can include in a load set. If you attempt to delete a point associated with a load or constraint, the software informs you of the association by pointing out that the geometry is referenced by a simulation feature. You can delete the point, but the software also deletes any associated load or constraint. You can edit and delete the individual loads or constraints that make up a set. You can also edit and delete a constraint set or load set. With constraint and load set editing, the only aspects of the set you can change are the name or the set description. You can remove a given load or constraint from its set by editing the name of the load set or constraint set. Force and Moment Loads Use the Insert>Force/Moment Load command to create loads in Structure and FEM mode Structure. You can create a load on one or more geometric entities, depending on your model type. These loads are the most widely used Mechanica loads. See Guidelines for Force and Moment Loads. When you select Insert>Force/Moment Load, the Force/Moment Load dialog box appears. This dialog box contains the following items: • • • Name — The name of the load. Member of Set — The name of the load set. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. References — The drop-down list includes the following geometric entities. You can select the geometry for these references before you enter the dialog box, or use the selector arrow and the normal selection methods to choose the desired geometry. o Surface(s) — You can select individual surfaces, several surfaces, quilts, or part boundaries. o Edge(s) — You can select edges, curves, or composite curves. o Point(s) — You can select single points, vertices, point features, or patterns of points. If you select multiple entities, Mechanica creates a single load that applies to the entities, and not one load for each entity. • Coordinate System — Change the coordinate system. The default is the WCS. The software calculates the coordinate location of the component or vector you use to specify force or moment with respect to this coordinate system. Advanced — Expand the dialog box to display these fields: o Distribution o Spatial Variation — Does not appear if you selected Total Load At Point from the load distribution options. Force — Specify the magnitude and direction of the force for your load. • • 436 Structural and Thermal Simulation • • Moment — Specify the magnitude and direction of the moment for your load. Preview — Adds a series of arrows to your model showing the location and distribution of the load. After you accept the dialog box, Mechanica places a load icon at each location you selected. Guidelines for Force and Moment Loads In working with force or moment loads, bear the following in mind: • For solid models, you can apply force loads to points, vertices, curves, edges, or surfaces. However, other than TLAP moments, you should not apply moments to edges on solid models, or to edges or surfaces of 2D plates or 2D solids. Bear in mind that applying forces or moments to points can also result in stress concentrations. For shell models, you can apply forces and moments to points, vertices, curves, or surfaces. You should avoid defining a moment that is normal to the midsurface. Also, bear in mind that applying forces or moments to points can result in stress concentrations. Do not apply a moment load to a point on a solid, 2D solid, or 2D plate. You can combine forces and moments in one load. You define forces and moments relative to the current coordinate system. If you do not designate a current coordinate system, the load is relative to the WCS. If the Z axis of a reference cylindrical or spherical coordinate system touches an entity that you want to load, you may not be able to successfully specify a force or load value for one or more of the directional components. Mechanica may display a message informing you of the problem. For FEM mode, you will see the message at run time. To work around this problem, you can change the coordinate system to a Cartesian coordinate system or re-orient the coordinate system so the Z axis no longer touches the entity you want to load. • When you apply a force or moment, Mechanica displays a load icon on the appropriate entities. The icon includes a vector that indicates the direction of the load. If the vector direction does not agree with what you specified, review the load. • • • • • Specifying Magnitude and Direction for Loads Select one of these items to specify the magnitude and direction for force, moment, velocity, or acceleration for a load. Note that, for most loads, you can enter any of the values discussed below as a real number, an arithmetic expression, or a parameter name. However, for bearing loads, you can only use real numbers. • Components — Enter the components of the force or moment for each coordinate direction. Mechanica determines the direction and magnitude of the force or moment from the components you enter. 437 Structural and Thermal Simulation - Help Topic Collection Note: If you have a 2D plane strain, 2D plane stress, or 2D axisymmetric model, you can specify only X and Y for a force load. If you have a 2D plane strain or 2D axisymmetric model, you can specify only Z for a moment load. Specify Z only for 2D shells, not for 2D solids. For 2D plane stress models, you cannot specify moment loads. • Dir Vector & Mag — Define the direction of the force or moment by entering the values for the unit vectors of the selected coordinate system, and enter the magnitude of the force in the Mag entry box. If you enter a positive magnitude, the software applies the force or moment in the same direction as the vector. If you use a negative value, the direction opposes the vector. Dir Points & Mag — Enter the direction of the force or moment by selecting two points and then entering the magnitude of the force in the Mag entry box. If you enter a positive magnitude, the software applies the force or moment in the same direction as the vector. If you use a negative value, the direction opposes the vector. • Note that, if you select Components or Dir Vector & Mag for centrifugal loads, the origin of the coordinate system you select determines the location of the angular velocity axis and angular acceleration axis. If you select Dir Points & Mag for centrifugal loads, the angular velocity axis and angular acceleration axis pass through the points you select. If you are using a UCS for force or moment loads, the references to the WCS X, Y, and Z axes on the dialog box are replaced as follows: UCS Type Cartesian Cylindrical Spherical X R R Y Theta Theta Axes Z Z Phi Distribution for Load For edges and surfaces, you can select one of the following options on the Force/Moment Load dialog box for specifying how you want Mechanica to distribute the load you are creating: • • • Total Load Force Per Unit Type — Type is either Length, Area, or Volume. Total Load At Point 438 Structural and Thermal Simulation For points, you can select one of the following options on the Force/Moment Load dialog box: • Total Load — Distribute the load across all the points you select. In this case, Mechanica divides the load you specify by the number of points to determine the load that each point will bear. For example, if you specify a load of 100 pounds and select 4 points, each point will bear a 25 pound load. Load Per Point — Apply the load you specify to each of the points you select. In other words, if you specify a load of 100 pounds and select 4 points, each point will bear a 100 pound load. • Spatial Variation The spatial variation options supported in Mechanica enable you to simulate both simple and complex load variations over the entities for which you are defining the load. These options are useful for models that have localized load concentrations, such as tapering loads and load reversals. You can use Mechanica's spatial variation options to define nonuniform loads applied to the geometry of your model. The complexity of the variation depends on the option you select. Spatial variation options are available for Thermal heat loads and all Structure entity loads except for bearing loads. You can select one of the following options for specifying how you want Mechanica to spatially vary the load you are creating: • • • Uniform — Use this option to apply a uniform load. The values entered are multiplied by 1 over the selected entities. The load has no spatial variation. Interpolated Over Entity Function of Coordinates Preview When you click Preview, Mechanica checks the load for errors. • • If there are no errors, Mechanica displays the load vectors in magenta. The load vectors are replaced with yellow load distribution arrows when you click OK. If errors appear, correct the load definition before proceeding. To Define Force and Moment Loads 1. Select Insert>Force/Moment Load or click The Force/Moment Load dialog box appears. 2. Enter a name for the load, or use the default name. 439 . Structural and Thermal Simulation - Help Topic Collection 3. Select an existing load set from the Member Of Set area or use the New button to display the Load Set dialog box and create a new load set. 4. If you did not select geometric entities as references before you opened the dialog box, select one of these References from the drop-down list: o Surface(s) o Edge(s) o Point(s) 5. Click and use the normal methods to select a reference. 6. If you want to change the reference coordinate system, click the selector arrow and select a UCS. The default is the WCS. 7. If you want to specify the distribution and spatial variation for the load click the Advanced button to display these fields: o Distribution o Spatial Variation 8. Select one of these options from the drop-down list under Force to specify magnitude and direction, and enter the appropriate values: o Components o Dir Vector & Mag o Dir Points & Mag In the directional component fields, you can enter a value, mathematical expression, or parameter name. 9. If desired, repeat step 8 for the Moment area. 10. If you want to display the load you just defined, click the Preview button. The software displays the load distribution and direction using arrows. 11. Click OK to accept the dialog box. If the software identifies any problems with the way you defined the load, it displays a message box informing you of the situation. If the software does not encounter any definition problems, it applies the loads that you specified to all the entities you selected. The software also adds a load icon to the geometry you are loading. Bearing Loads Use the Insert>Bearing Load command in Structure to create a bearing load on the surface or curve of a hole. Bearing loads are special-purpose loads that approximate the distribution of a force in a particular direction, for example, on a bolt through a hole. You can expect a tapering effect with this type of load. Bearing loads approximate the pressure applied to a 3D surface (hole) or a 2D circle (ring) by a rigid pin or axle passing through the center of a hole or ring. For more information on bearing loads, see Guidelines for Bearing Loads. 440 Structural and Thermal Simulation When you select Insert>Bearing Load , the Bearing Load dialog box appears with the following items: • • • • • Name — The name of the load. Member of Set — The name of the load set. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. Bearing Hole — Allows you to select the hole surfaces on which you want to place the bearing load. Use the selector arrow and the regular selection methods to choose the desired geometry. Coordinate System — Allows you to select the coordinate system that the bearing load will reference. You must select a Cartesian coordinate system. The default is the WCS. Force — Allows you to specify the direction and magnitude of the bearing load vector. The load vector cannot be parallel to the axis of one or more selected holes. The software ignores any portion of the load vector that is parallel to the hole axis. Preview — Adds a series of arrows to your model showing the location and distribution of the bearing load. • Guidelines for Bearing Loads When working with bearing loads, keep the following guidelines in mind: • • • • • • Bearing loads are not available in FEM mode. You can apply this type of load to a non-right cylindrical surface with spline or elliptical surface curves on the surface edge. The cylindrical surface must have a straight centerline and a constant radius. You can apply this type of load to open surfaces. However, surfaces must be connected to form a portion of a cylinder. The software displays the bearing load distribution toward the inside of the surface region. The vector you specify must have at least one component that is not parallel to the axis of any hole you select. If you specify a vector that is fully parallel to the axis, the software does not accept the load. The software defines a bearing load distribution as a cosine distribution that does not vary down the length of the centerline. This distribution enables you to quickly apply compression-only bearing loads to cylinders and rings. Preview When you click Preview, Mechanica checks the load for errors. • • If there are no errors, Mechanica displays the load vectors in magenta. The load vectors are replaced with yellow load distribution arrows when you click OK. If errors appear, correct the load definition before proceeding. 441 Structural and Thermal Simulation - Help Topic Collection To Define Bearing Loads 1. Select Insert>Bearing Load or click The Bearing Load dialog box appears. 2. Enter a name for the load, or use the default name. 3. Select an existing load set from the Member Of Set area or use the New button to create a new load set. 4. Select the circular curve or surface on which you want to place the bearing load now. Your selections appear under Bearing Hole. 5. To choose another Cartesian coordinate system, click the selector arrow. 6. Select one of the following to specify the magnitude and direction of the load: o o o Components Dir Points & Mag Dir Vector & Mag . 7. If you want to display the load that you just defined, click the Preview button. The software displays the load distribution and direction as a series of magenta arrows. 8. Click OK to accept the dialog box. If the software identifies any problems with the way you defined the load, it displays a message box informing you of the situation. If the software does not encounter any definition problems, it applies the loads that you specified to all the entities you selected. The software also adds a load icon to the geometry you are loading. Centrifugal Loads Use the Insert>Centrifugal Load command in Structure and FEM mode Structure to create a centrifugal load on the entire model resulting from rigid body rotation of the model. You can specify the angular velocity and/or angular acceleration, which can have different vector directions. See Guidelines for Centrifugal Loads for more information. When you define a centrifugal load, you specify to which load set it belongs. Note that you can have only one centrifugal load per load set. When you select Insert>Centrifugal Load , the Centrifugal Load dialog box appears with the following items: • • Name — The name of the load. Member of Set — The name of the load set. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. 442 Structural and Thermal Simulation • • Coordinate System — Allows you to select the coordinate system that the centrifugal load will reference. You must select a Cartesian coordinate system. Angular Velocity — Allows you to specify the direction and magnitude of the vector. The velocity can be positive or negative. For 2D axisymmetric models, you can only specify the magnitude of the angular velocity. If you select the Dir Points & Mag option, see From and To Fields for Centrifugal Loads for more information. • Angular Acceleration — Allows you to specify the direction and magnitude of the vector. The angular acceleration vector is the rate of change of the angular velocity vector. If you select the Dir Points & Mag option, see From and To Fields for Centrifugal Loads for more information. • Preview — Adds arrows to your model showing the vector direction of the centrifugal load. One of the arrows reflects the angular velocity and the other, the angular acceleration. If you specify angular velocity as 0, Mechanica only displays the angular acceleration arrow, and the reverse. After you complete the Centrifugal Load dialog box, the software places an angular velocity and/or angular acceleration load icon on the model. The icons represent vectors. The angular velocity icon has one arrowhead, and the angular acceleration icon has two arrowheads, one on top of the other. Guidelines for Centrifugal Loads • Centrifugal loads are body loads available in native mode and FEM mode Structure. These loads simulate rigid body rotation for your model. When you define a centrifugal load, you can specify angular velocity, angular acceleration, or both. For each of these load quantities, you need to define either the components, two directional points and magnitude, or the direction vector and magnitude. For angular velocity, enter the velocity or rotation in radians per second. You can enter a positive or negative value. You also need to define the magnitude and direction of the load vector. For angular acceleration, enter the acceleration or rotation in radians per second2. As with angular velocity, you can enter either a positive or negative value. You also need to define the magnitude and direction of angular acceleration. For 3D models, centrifugal load axis definitions are always relative to the WCS, regardless of the current coordinate system. For 2D models, the axis definitions are relative to the reference coordinate system for the 2D model. For 2D axisymmetric models, you do not specify the direction for angular velocity because the axis of rotation is always the Y axis of the referenced coordinate system of the axisymmetric model. Only the magnitude of angular velocity is required. Angular acceleration is not available in 2D axisymmetric models. 443 • • • • Structural and Thermal Simulation - Help Topic Collection • • • • • • • For 2D plane strain and 2D plane stress models, only the Dir Points & Mag option is available. You specify From and Magnitude. The axis of rotation and angular acceleration vector pass through that axis location and are perpendicular to the WCS XY plane. The software uses the right-hand rule to determine the direction of rotation about the axis and acceleration direction. To determine the direction of rotation, the software applies the right-hand rule to the velocity's sign. You can define only one centrifugal load per load set. You cannot review a resultant centrifugal load. (Each load set is calculated separately.) If you are running a prestress modal analysis on a model with a centrifugal load, Mechanica will compute modified vibrational modes to take into account the effect of relative circumferential motions, an effect known as spin softening. If you select multiple load sets for an analysis, at least one load set contains a centrifugal load, and you specify load set scaling when you view the analysis results, you can scale the load set, but the resulting omega term (such as rpm or rps) does not have a linear relationship with the centrifugal load. If you need to scale velocity or acceleration, you can isolate the centrifugal load and adjust the scale separately. For large deformation analyses that use centrifugal loads, the results will scale the body force, but not the velocity or acceleration. You can see the effect of this when you compare results of an analysis that uses one centrifugal load against the results of an analysis that uses a scaled version of the same load. The results will scale correctly in the linear range but, scaling may no longer provide accurate results when you enter the nonlinear range. From and To Fields for Centrifugal Loads Use these input fields for the Dir Points & Mag option to define the axis of rotation for angular velocity and the direction of the angular acceleration vector, as follows: • • The direction of the load vector is from the point specified in the From field to the point specified in the To field. You fill in these fields by using the selector arrows to choose datum points. If you need to create datum points at a particular location, use the Insert>Model Datum>Point>Point command. When you use the selector arrow to specify datum points for these fields, the software translates the datum point location into the WCS coordinates of the point you picked, even if a UCS was active when you picked the datum point. In using the datum point as a reference location, the software disassociates the vector from the defining datum points. This means that if the datum points move during a sensitivity or optimization study, the vector remains unchanged. • • For 2D axisymmetric models, you do not fill in these fields, because the axis of rotation is always the WCS Y axis and the angular acceleration vector is always parallel to the WCS Y axis. For 2D plane strain and 2D plane stress models, you only use the To field. The axis of rotation and angular acceleration vector pass through that axis 444 Structural and Thermal Simulation location and are perpendicular to the WCS XY plane. The software uses the right-hand rule to determine the direction of rotation about the axis and acceleration direction. Preview When you click Preview, Mechanica checks the load for errors. • • If there are no errors, Mechanica displays the load vectors in magenta. The load vectors are replaced with yellow load distribution arrows when you click OK. If errors appear, correct the load definition before proceeding. To Define Centrifugal Loads 1. Select Insert>Centrifugal Load or click The Centrifugal Load dialog box appears. 2. Enter a name for the load, or use the default name. 3. Select an existing load set from the Member Of Set area or use the New button to create a new load set. 4. If you want to change the reference coordinate system, click the selector arrow. 5. Select one of the following from the Angular Velocity and Angular Acceleration drop-down lists to specify magnitude and direction: • Components • Dir Points & Mag • Dir Vector & Mag 6. Specify the directional values. You can enter a value, mathematical expression, or parameter name in these fields. 7. If you want to display the load that you just defined, click the Preview button. The software displays the angular velocity and angular acceleration direction using arrows. 8. Click OK to accept the dialog box. If the software identifies any problems with the way you defined the load, it displays a message box informing you of the situation. If the software does not encounter any definition problems, it applies the loads that you specified. The software also adds a load icon to the geometry you are loading. . Gravity Loads Use the Insert>Gravity Load command in Structure or FEM mode Structure to create an accelerational load on your entire model. See Guidelines for Gravity Loads for more information. 445 Structural and Thermal Simulation - Help Topic Collection When you define a gravity load, you specify to which load set it belongs. Note that you can have only one gravity load per load set. When you select Insert>Gravity Load, the Gravity Load dialog box appears with the following items: • • • • • Name — The name of the load. Member of Set — The name of the load set. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. Properties — Change the coordinate system. Use the selector arrow if you want to select a Cartesian coordinate system to reference the acceleration vector. The default is the WCS. Acceleration — Specify the magnitude and direction of the gravitational acceleration. The units of the value you enter should be length/time2. Preview — Adds an arrow to your model showing the direction of the gravity load. After you complete the dialog box, Mechanica places a gravity load icon at the origin of the WCS, with a vector pointing in the direction of the load and the letter G at the endpoint of the vector. The gravity load acts at the center of gravity of the part or assembly. Guidelines for Gravity Loads • • • You can define only one gravity load per load set. You cannot review a resultant gravity load. (Each load set is calculated separately.) Gravity loads are body loads available only in Structure. These loads simulate the force of gravity as it affects your model. When you define a gravity load, you specify the gravitational components of the load in each coordinate direction. In specifying gravity, you enter values that define gravitational acceleration, expressed as distance/time2. You can enter a positive or negative value. The sign you enter defines the direction of gravity relative to the WCS or to another Cartesian coordinate system. When choosing a sign, understand that a negative value opposes the coordinate direction. For example, if you want to simulate a downward gravitational force of 1G (386.4 in/sec2) in the Y direction, and you are working in in/sec2, you enter –386.4 in the Y entry box. If you simply enter 386.4, the gravitational force would be upward. For 3D models, gravity is relative to the WCS or to another Cartesian coordinate system you choose as the reference. For 2D models, gravity is relative to the reference coordinate system for the 2D model or to another Cartesian coordinate system you choose as the reference. When you apply a gravity load, the software displays a gravity icon at the origin of the WCS. The icon includes a vector that indicates the direction of the load. If the vector direction does not agree with what you thought you specified, review the load. • • • • 446 Structural and Thermal Simulation Preview When you click Preview, Mechanica checks the load for errors. • • If there are no errors, Mechanica displays the load vectors in magenta. The load vectors are replaced with yellow load distribution arrows when you click OK. If errors appear, correct the load definition before proceeding. To Define Gravity Loads 1. Select Insert>Gravity Load or click The Gravity Load dialog box appears. 2. Enter a name for the load, or use the default name. 3. Select an existing load set from the Member Of Set area or use the New button to create a new load set. 4. If you do not want to use the WCS as the reference coordinate system, click the selector arrow to select a different Cartesian coordinate system as the reference. 5. Select one of the following from the drop-down list to specify the magnitude and direction for the Acceleration: o Components o Dir Vector & Mag o Dir Points & Mag 6. Specify the directional values. You can enter a value, mathematical expression, or parameter name in these fields. 7. To display the load, click Preview. The software displays an arrow representing the gravity direction on your model. 8. Click OK to accept the dialog box and save the load. If the software does not encounter any definition problems, it applies the load that you specified. The software also adds an icon at the origin of the WCS. . Pressure Loads You can use the Insert>Pressure Load command in a Structure or FEM mode Structure model to create a pressure load on 3D model surfaces or 2D model curves. For 2D models, you can only select a curve that bounds one and only one surface. You cannot pick datum curves, free-floating curves, or curves shared by more than one surface. A positive pressure load always acts in opposition to the normal direction of an entity at every location, even if the entity is curved. Mechanica sets the normal direction automatically for entities as you create them. 447 Structural and Thermal Simulation - Help Topic Collection When you select Insert>Pressure Load , the Pressure Load dialog box appears with the following items: • • • Name — The name of the load. Member of Set — The name of the load set. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. References — Select geometric entities—edges or curves for 2D models, and surfaces for 3D models. If you selected the geometric entity before entering the dialog box, your selections appear next to the selector arrow when you open the dialog box. Otherwise, use the selector arrow and the regular selection methods to choose the entities you want to load. If you select a quilt surface, Mechanica displays the surface normal using a purple arrow at the time you select the surface, and gives you the option of flipping the normal direction. If you selected the surface before entering the dialog box, you can use the selector arrow to reselect the surface and determine the normal direction. • Advanced — Expand the dialog box to define the spatial variation by indicating how you want Mechanica to vary the load across the geometric entity. You can choose a uniform load—one that remains the same across the selected geometry. As an alternative, you can vary the load either through interpolation or as a function of coordinates. Value — Enter a real number, an arithmetic expression, or a parameter name for the magnitude of the pressure load. If you enter a negative magnitude, the pressure direction is coincident with the normal direction. Preview — Adds a series of arrows to your model showing the location and distribution of the pressure load. • • The software determines the pressure load direction by the sign that you use to specify the magnitude. Be aware of the following behaviors when determining the sign of a pressure load: • • Solid Faces — If the pressure value is positive, the load pushes toward the surface because the normal for solids is always outward from the solid face. If the pressure value is negative, the load pulls away from the surface. Quilts — If the pressure value is positive, the load pulls in the direction opposite of the normal direction that Mechanica displayed when you selected the pressure load surface. If the pressure value is negative, it pulls in the same direction as the normal direction. Be aware that, if you switch to Pro/ENGINEER and change the surface normal of a quilt to which you have applied a pressure load, the load direction in Mechanica changes. See Guidelines for Pressure Loads for more information. See Example: Pressure Load for an example of pressure load distribution. 448 Structural and Thermal Simulation Guidelines for Pressure Loads • • • • • In 3D models, you can apply pressure loads only to surfaces. In 2D models, you can apply pressure loads to an edge or to a curve that is the boundary of one and only one surface. You cannot apply pressure loads to points. Pressure loads are independent of a coordinate system, so you do not need to select a coordinate system. When you apply a pressure load, Mechanica displays a load icon on the appropriate entities. The icon includes a vector that indicates the direction of the load. If the vector direction does not agree with what you thought you specified, review the dialog box and check the sign of the load value. Pressure Load Direction The following table shows the pressure load direction for each entity type: Entity Type Quilt Surface Pressure Load Direction A positive pressure load acts opposite the direction of the surface's normal. The normals for adjacent surfaces may be in opposite directions, although Mechanica attempts to align them where possible. When you create a pressure load, use the Preview button on the Pressure Load dialog box to check the application direction. To reverse the direction, change the sign of the pressure load. Solid Face A positive pressure load always points into the solid, unless there is a shell on the face. A positive pressure load points into the 2D solid or 2D plate. 2D Solid Edge, 2D Plate Edge, 2D shell Preview When you click Preview, Mechanica checks the load for errors. • • If there are no errors, Mechanica displays the load vectors in magenta. The load vectors are replaced with yellow load distribution arrows when you click OK. If errors appear, correct the load definition before proceeding. 449 Structural and Thermal Simulation - Help Topic Collection To Define Pressure Loads 1. Select Insert>Pressure Load or click The Pressure Load dialog box appears. 2. Enter a name for the load, or use the default name. 3. Select an existing load set from the Member Of Set area or use the New button to create a new load set. 4. If you did not select a geometric reference before you opened the dialog box, select the entity to which you want to apply your pressure load now. 5. If you selected a quilt surface, check the normal direction of the surface by noting the direction of the purple arrow. If necessary, use the Flip Normals command to change the normal direction. 6. If you want to specify how the load is distributed across the selected geometry, click the Advanced button and select one of the following from the Spatial Variation drop-down list: o Uniform o Function Of Coordinates o Interpolated Over Entity (not supported in FEM mode) 7. Enter a real number, arithmetic expression, or parameter name for the pressure in the Value entry box. 8. If you want to display the load that you just defined, click the Preview button. The software displays a series of arrows representing the load distribution and direction. 9. Click OK to accept the dialog box. If the software identifies any problems with the way you defined the load, it displays a message box informing you of the situation. If the software does not encounter any definition problems, it applies the loads that you specified to all the entities you selected. The software also adds a load icon to the geometry you are loading. . Temperature Loads Temperature loads enable you to simulate a temperature change over your model. Temperature loads provide valuable information on how the structure of your model deforms due to a particular temperature change. Depending on how you specify the load, the temperature change is either uniform across the model or variable according to a temperature distribution from a Mechanica Thermal analysis. In FEM mode, function of coordinates is also a temperature distribution option. See Guidelines for Temperature Loads. Use the Insert>Temperature Load in Structure to: • create global and MEC/T temperature loads that result from temperature changes over the model 450 Structural and Thermal Simulation You can include only one global or MEC/T temperature load in a load set. MEC/T temperature loads are not available in FEM mode. • create structural temperature loads that result from temperature changes on a specified entity (FEM mode) You can include more than one structural load in a load set, but each load must be on a different entity. If you have a global temperature load and a structural temperature load, the global load applies everywhere except on the entities with the structural load. • import external temperature loads into Structure. This option is not available in FEM mode. When you create a temperature load, Mechanica places a load icon near the origin of the WCS. After you create a temperature load, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a temperature load, Mechanica asks you for confirmation first. Guidelines for Temperature Loads For all temperature loads, keep the following guidelines in mind: • • Temperature loads are body loads available in Structure only. Use these loads to simulate a temperature applied to the body of the model. In Mechanica, you can define only one temperature load per load set. In other words, you cannot place both a global and a MEC/T temperature load in the same load set. In Mechanica FEM mode, you can define multiple temperature loads per load set. You can define a load set that has a global temperature load and a structural temperature load. If you have a global temperature load and a structural temperature load, the global load applies everywhere except on the entities with the structural load. You can include more than one structural load in a load set, but each load must be on a different entity. • For global temperature loads, Mechanica assumes a default of 0 if you do not enter a value. Global Temperatures Global Temperature Loads Use the Insert>Temperature Load>Global command in Structure or FEM mode Structure to create a thermal load resulting from a temperature change over the entire model. 451 Structural and Thermal Simulation - Help Topic Collection When you select Insert>Temperature Load>Global ,the Global Temperature (or Global Temperature Load in FEM mode) dialog box appears with the following fields: • • • Name — The name of the load. Member of Set — The name of the load set. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. Model Temperature — The temperature to which you wish to bring your model. The model temperature is the temperature you want to apply to the model. In FEM mode, you can also define how you want Mechanica to distribute the temperature load. To do so, select Uniform or Function Of Coordinates from the Spatial Variation drop-down list. If you select Uniform, the software applies the thermal load equally over the model. If you select Function Of Coordinates, Mechanica displays the f(x) button, enabling you to enter an existing function or create a new function. • Reference Temperature — The zero stress temperature of your model. The reference temperature is the stress-free temperature of the model—whether that temperature is room temperature or some other temperature that is normal for the model. The difference between the model temperature and the reference temperature is the amount of temperature change over the model. After you complete the dialog box, the software places a temperature load icon on your model. To Define Global Temperature Loads 1. Select Insert>Temperature Load>Global or click . The Global Temperature dialog box (or Global Temperature Load in FEM mode) appears. 2. Enter a name for the load, or use the default name. 3. Select an existing load set from the Member Of Set area or use the New button to create a new load set. 4. Use the Model Temperature entry box to enter the temperature you want the software to apply to the model during analysis. In FEM mode, you also select Uniform or Function of Coordinates from the Spatial Variation area to tell the software how to distribute the temperature load. 5. Use the Reference Temperature entry box to enter the stress-free temperature of the model. 6. Click OK. 452 Structural and Thermal Simulation If Mechanica identifies any problems with the way you defined the load, it displays a message box informing you of the situation. If Mechanica does not encounter any definition problems, it applies the load that you specified. Mechanica also adds a temperature load icon to the geometry you are loading. MEC/T Temperatures MEC/T Temperature Loads Use the Insert>Temperature Load>MEC/T command in Structure to apply a thermal load across the entire model based on a temperature field developed from the results of a steady-state or transient thermal analysis. The thermal load is based on a temperature field from a load set in either a steady-state thermal analysis or a transient thermal analysis. This option enables you to use the temperatures from a previously defined thermal analysis as a thermal load in Structure. MEC/T temperature loads prove valuable if you want to apply a non-uniform temperature change to your model. This option is not available in FEM mode. For more information, see Guidelines for MEC/T Temperature Loads. When you select Insert>Temperature Load>MEC/T , the MEC/T Temperature dialog box appears with the following items: • • • • Name — The name of the load. Member of Set — The name of the Structure load set. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. Use Previous Design Study — Appears and is selected if you previously defined a standard design study that includes a thermal analysis. Design Study — Appears only if the Use Previous Design Study check box is selected. If multiple standard design studies exist that include thermal analyses, you can select a design study other than the first standard design study for the model with a thermal analysis. Analysis — If multiple thermal analyses exist, you can select a thermal analysis other than the first one defined for the design study (if you selected a design study) or the first one defined for the model. Load Set — Appears only if the MEC/T temperature load is coming from a steady-state thermal analysis. If multiple load sets exist in the analysis you selected, you can select a load set other than the default (the first one defined for the thermal analysis). If the thermal analysis contains no load sets (for instance, prescribed temperatures only), this option does not appear. Step — Appears only if the MEC/T temperature load is coming from a transient thermal analysis. Reference Temperature — Enter the nominal zero strain temperature for the model. The temperature change for the thermal load at a given location on the model is the difference between the Thermal temperature result at the location and the reference temperature. • • • • 453 Structural and Thermal Simulation - Help Topic Collection Guidelines for MEC/T Temperature Loads For MEC/T temperature loads, keep the following guidelines in mind: • • You must have defined at least one steady-state thermal or transient thermal analysis to apply a MEC/T temperature load. If you are importing a thermal load from a transient thermal analysis, the transient thermal analysis must have at least one master interval with Temp Load selected. Use the Output tab of the Transient Thermal Analysis Definition dialog box to make this selection. A MEC/T temperature load enables you to use the temperatures from a previously-defined thermal analysis as a thermal load in a structural analysis. You can run the thermal analysis in the same design study as the structural analysis or you can run the thermal analysis before you run the structural analysis. However, if you choose the latter approach and you have defined dimension parameters for your model, the parameter settings you use in the Structure design study must match those of the Thermal study. As with the global option, you supply a reference temperature for MEC/T temperature loads. Mechanica calculates the temperature change at a given model location as the difference between that location's temperature as determined in the thermal analysis and the reference temperature. The mesh must be identical for the thermal and structural models. Thermal ignores springs and masses. • • • Use Previous Design Study If you select this check box on the MEC/T Temperature dialog box, Mechanica takes the temperatures for the load you are creating from a thermal analysis that has been or will be run as part of a standard design study you previously defined. If you deselect this item, Mechanica automatically runs the thermal analysis before running any structural analysis that includes the load. If you include the structural analysis that uses the MEC/T temperature load in a sensitivity or optimization design study, Mechanica ignores this item, as well as any design study specified. In this case, Mechanica automatically runs the thermal analysis for whatever parameter settings are required in the sensitivity or optimization design study. Step Mechanica sums all load sets for transient thermal analyses, but computes separate solutions corresponding to different times. Use the Step drop-down list on the MEC/T Temperature dialog box to display the time steps that are defined for the transient thermal analysis associated with the MEC/T temperature load. 454 Structural and Thermal Simulation To Define MEC/T Temperature Loads This procedure assumes that you are in Structure, and have defined a steady-state or transient thermal analysis in Thermal. 1. Select Insert>Temperature Load>MEC/T. The MEC/T Temperature dialog box appears. 2. Enter a name for the load or use the default name. 3. Select an existing load set from the Member Of Set area or use the New button to create a new load set. 4. If you have defined a standard design study that includes a thermal analysis the Use Previous Design Study check box is available and checked. Clear this check box if you do not want to use the design study for the MEC/T load. 5. If you checked the Use Previous Design Study check box select a Design Study from the drop-down list. 6. Select a thermal analysis from the Analysis drop-down list. 7. If you selected a steady-state thermal analysis, select a Load Set from the drop-down list. 8. If you selected a transient thermal analysis, select a Step from the dropdown list. 9. Enter a real number or expression for the Reference Temperature. 10. Click OK to accept the dialog box. If the software identifies any problems with the way you defined the load, it displays a message box informing you of the situation. If the software does not encounter any definition problems, it applies the load that you specified. The software also adds a MEC/T load icon to the geometry you are loading. External Temperatures External Temperature Loads Use the Insert>Temperature Load>External command in Structure to import an externally calculated or measured temperature field as a temperature load. The external temperature field must contain connectivity of a linear solid element mesh, node locations, and temperature values at the nodes. This command is not available in FEM mode. Before using this command, be sure to read Guidelines for Importing External Temperature Fields. When you select Insert>Temperature Load>External the External Temperature dialog box appears with the following fields: • Name — The name of the load. 455 Structural and Thermal Simulation - Help Topic Collection • • • • Member of Set — The name of the load set. You can select an existing load from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. Reference — Use this area to select the reference coordinate system that will serve as the basis for the load. You can select a Cartesian, cylindrical, or spherical coordinate system. Mechanica uses the WCS as the default. File — Use this area to enter the name of your external temperature file. Alternatively, click the selection button and Mechanica displays a dialog box where you can select an external temperature file through the FEM Neutral Format file. Mechanica adds a .fnf extension to your external temperature field file. Reference Temperature — Enter the nominal zero strain temperature for the model. The temperature change for the thermal load at a given location on the model is the difference between the Thermal temperature result at the location and the reference temperature. Guidelines for Importing External Temperature Fields • Before you import an external temperature, you must create a FEM Neutral Format file, which Mechanica uses to import your temperature load. The FEM Neutral Format file enables you to store an externally created temperature field and import it into Structure. For more information, see FEM Neutral Format File and Sample FNF File for External Temperature. Mechanica automatically copies the FEM Neutral Format file you create into a study directory. If you do not want this file in the study directory, you must set a config.pro option. For more information, see Configuration File Options. Mechanica extracts temperature data from the h-mesh Mechanica FEM Neutral Format file by finding the h-element that encompasses the point where the p-element temperature is desired, and performing a linear interpolation of the temperature at the h-element's corner nodes. If the pelement point is not inside any of the h-elements—for example, when the curved boundary of a p-element lies outside the h-mesh—Mechanica projects the point to an h-element face, edge, or node and performs a three, two, or one-point interpolation. When entire elements of the p-mesh lie outside the h-mesh, Mechanica still projects the points onto the outer faces of the h-mesh. As the distance increases, Mechanica may not project the point onto the closest face, but instead onto the first orthogonal projection it finds. • • • • Your imported temperature load must contain the connectivity of a linear solid element mesh, node locations, and temperature values at the nodes. If the temperature load mesh is not consistent, Mechanica displays an error message. If you defined the temperature load for part of your model, Mechanica displays an error message indicating that it will calculate temperature through extrapolation for parts of the model. If you performed a design study for your model that included size or shape changes, you must make sure the temperature field is consistent for all the design variations included in the study. • • 456 Structural and Thermal Simulation When you import an external temperature load, you also import the model's orientation. To Define External Temperature Loads 1. Select Insert>Temperature Load>External. The External Temperature dialog box appears. 2. Enter a name for the load, or use the default name. 3. Select an existing load set from the Member Of Set area or use the New button to create a new load set. 4. If you do not want to use the WCS as the reference coordinate system, click the selector arrow in the Reference area to select a different reference coordinate system. 5. In the File area, enter an external temperature field file name or click to display an additional dialog box. Use this dialog box to select a .fnf file. The default is your current directory. Select a file name from the current directory or from another directory. 6. Enter the reference temperature you want Mechanica to apply during the analysis. You can enter a real number or an expression. 7. Click OK. If Mechanica identifies any problems with the way you defined the load, it displays a message box informing you of the situation. If Mechanica does not encounter any definition problems, it applies the loads that you specified to all the entities you selected. Mechanica also adds a temperature load icon to the geometry you are loading. Mechanism Loads Use the Insert>Mechanism Load command to import a load set from Mechanism Design Extension into Structure. Before using this command, you must use the Use In Structure command in Mechanism Design to create the load set based on the results of a dynamic analysis. This option is not available in FEM mode. For more information on the Use in Structure command, see About Load Transfer to Structure in the Mechanism Design module in the Pro/ENGINEER Help Center (Simulation functional area). The load set that you create in Mechanism Design includes inertial and reaction forces and gravity, as well as any applied external forces and torques. When you create the load set, you associate the load set with a part, subassembly, or top-level assembly file. To import the Mechanism Design load set and use the loads in Structure, you must complete two steps: • • Open the component file in Structure and import the load set. Associate the loads that you want to use with geometric references. 457 Structural and Thermal Simulation - Help Topic Collection It is important that you carry out both steps. If you do not associate the loads before you exit Structure, Mechanica will not save them with the model. To associate a load, highlight the load icon on your model, select Edit>Definition to open the appropriate dialog box, and select a geometric reference for the load. When you select Insert>Mechanism Load , the Mechanism Load Import dialog box appears. Use this dialog box to specify which Mechanism Design loads you want to include in a Structure load set. For information on the various types of imported loads, see How Structure Imports Loads from Mechanism Design. Note: You can import the same Mechanism Design load set several times in a given Structure session by making sure the Clear Load Info After Import check box on the Mechanism Load Import dialog box is not selected. This gives you the option of associating the loads from the Mechanism Design load set with different entities in the same model. To Import Mechanism Loads This procedure assumes that you are working in Structure. You must have run an analysis in Mechanism Design and created a Mechanism Design load set. 1. Select File>Open and open the component file that contains the Mechanism Design load set. 2. Select Insert>Mechanism Load or click . The Mechanism Load Import dialog box appears with a list of the loads you exported from Mechanism Design for the component. 3. Accept the default load set from the Member Of Set area, select another existing load set, or use the New button to display the Load Set dialog box and create a new load set. 4. Clear the check box beside any load that you do not want to include in the load set. 5. Check the Clear Load Info After Import box if you do not want to import the load set more than once in the current session. 6. Click OK to create the load set. 7. Highlight each imported load icon and select Edit>Definition to associate the load with a geometric entity, or to change the referenced coordinate system. The various load types take you to different dialog boxes. • For reaction loads on connections, servo motors, force motors, springs, dampers, or external forces or torques, see Force and Moment Loads. • For centrifugal loads, see Centrifugal Loads. • For gravity loads, see Gravity Loads. 458 Structural and Thermal Simulation Troubleshooting Your Loads Troubleshooting Loads To help ensure a successful run, you may want to verify your loads, and, if you are working with an assembly, perform a pre-run error detection pass. To learn about load verification and other technical tips, read the following: • • • • • • Verifying a Load Reviewing Resultant Loads Reviewing Total Heat Loads Performing a Body Check for Assemblies Handling Stress Concentrations Check Model Verifying a Load You can review the load for entry errors by highlighting the load icon on your model and selecting Edit>Definition. The software will display the load definition dialog box for that load. To change any of the values you entered, simply type in new information. Reviewing Resultant Loads Use the Info>Review Total Load command in Structure to review the resultant load at predefined points on your model. Before running an analysis on your model, you may want to perform a check to see if the load values at particular model locations are what you expect them to be. Note: For information on reviewing heat loads in Thermal, see Reviewing Total Heat Loads. You can review resultant loads for the following load types: • • • • force loads moment loads bearing loads (native mode only) pressure loads If you want to review a resultant load at a particular location, you first need to add datum points. These datum points act as references from which the software evaluates the resultant load for the model, so place the points at locations that will provide significant data. In considering resultant loads, be aware of the following points: • The software calculates the resultant force. It also calculates the resultant moments about the selected datum point. The software displays the components of the resultant force and moment with respect to the unit vectors of the current coordinate system. 459 Structural and Thermal Simulation - Help Topic Collection • • You can view the resultant force and moments with respect to the WCS, or you may select another Cartesian coordinate system in the model. You can examine the effect of one or more loads. Selecting a single load is helpful when you are trying to troubleshoot the values for a particular load. Looking at a combination of loads can be helpful if you are concerned about the actual load that a particular portion of the model will see during a multiload analysis. To Review Resultant Loads 1. Select Info>Review Total Load. The Load Resultant dialog box appears. 2. Click in the Select Loads area and select the load icon for each load that you want to review. If you want to review the resultant load for several loads, use the normal selection methods to select all the desired load icons. 3. Click in the Select Coordinate System area and select a Cartesian coordinate system, or accept the default, the WCS. 4. Click in the Select Evaluation Point area and select a datum point. 5. Click the Compute Load Resultant button to review the forces and moments for the total load about the selected datum point. 6. If you want to save the review as a text file, select File>Save As and enter a filename and directory, or accept the defaults. 7. Click OK to exit the dialog box. Performing a Body Check for Assemblies If you are working with an assembly, you can check the number of bodies in your assembly by requesting error detection when you start your Mechanica analysis. During the error detection cycle, Mechanica informs you of how many bodies it finds in your assembly. If this count does not agree with the number you expect, review the assembly in Pro/ENGINEER and correct any mating problems. Then, return to Mechanica and add loads or constraints to any bodies that require them. For more information, see Assembly Considerations. • • These problems can lead to poor accuracy for analysis results. Curve loads can introduce theoretically infinite stresses or fluxes in solid models. You may want to define a small surface region and apply the load to the region instead of to a point. This approach distributes the stresses and fluxes over a slightly wider portion of the model, avoiding concentration problems. 460 Structural and Thermal Simulation To Define Structural Temperature Loads 1. Select Insert>Temperature Load>Structural and select Point, Curve, or Surface from the STRUCT TEMP menu. The Structural Temperature Load dialog box appears. 2. Enter a name for the load, or use the default name. 3. Select an existing load set from the Member Of Set area or use the New button to create a new load set. 4. If you did not select geometric entities as references before you opened the dialog box, select one or more geometrical entities now to receive the load. 5. Use the Entity Temperature area to select a variation and enter the temperature that you want the software to apply to the model during analysis. 6. Use the Reference Temperature area to enter the stress-free temperature of the model. 7. Click OK. If it identifies any problems with the way you defined the load, Mechanica displays a message box informing you of the situation. If it does not encounter any definition problems, Mechanica applies the loads that you specified to all the entities you selected. Mechanica also adds a temperature load icon to the geometry you are loading. Function of Coordinates Use this option to apply a structure constraint (FEM mode), thermal boundary condition, or load that is a function of the current coordinate system. You can select one or more entities on which to apply the constraint or load. You define this variation by specifying a function that Mechanica uses as a scale factor. If you are using Function of Coordinates for loads or thermal boundary conditions, Mechanica typically multiplies the load value by the scale factor to approximate the load behavior. For force/moment loads and heat loads, Mechanica makes an exception if you defined the load distribution as Total Load. In this case, Mechanica applies the function, respecting its shape, but does not multiply the function by the load value. Thus, the software maintains the original total load value. When you select this option, the f(x) button and entry box appear on the dialog box. Click the button and the Functions dialog box (native mode) or Functions dialog box (FEM mode) appears under one of the following conditions: • • If a user-defined function has not been defined for your model If an internal function has been defined for your model You can use this dialog box to create, copy, review, or delete a function. For an example, see Example: Function of Coordinates. 461 Structural and Thermal Simulation - Help Topic Collection Example: Function of Coordinates Function loads provide a means of simulating loads that have a complex magnitude distribution. For example, you can use the function of coordinates method to define sinusoidal loads, as shown below: In working with function loads, be aware that the resultant load depends on a number of factors, such as the orientation of the coordinate system, the dimensioning scheme you used for your part, and so forth. As a result of these dependencies, you may need to work through the function dialog box more than once to achieve the exact load conditions you want. Because function loads are complex, you may find it particularly useful to verify the load by clicking the Preview button on the Load Definition dialog box. The preview function shows the relative load magnitude at different points on the entity. You might also find it useful to verify the load. To review loads, select Info>Review Total Load after you define the load. The method you use varies depending on whether you are performing the review for a force, moment, bearing, or pressure load in Structure or a heat load in Thermal. Functional Form of Interpolation The number of interpolation points you select determines the functional form of interpolation, as shown below: Number of Points 1D Entities: 2 points 3 points linear variation in 1D parameter space quadratic variation in 1D parameter space Functional Form of Interpolation 462 Structural and Thermal Simulation 4 points 2D Entities: 2 points cubic variation in 1D parameter space linear variation in 2D parameter space, with no variation perpendicular to the line that connects the two points in parameter space 3 points 4 non-colinear points 4 collinear points linear variation in 2D parameter space bilinear variation in 2D parameter space cubic variation in 2D parameter space, with no variation perpendicular to the line that connects the four points in parameter space 4 points, with 3 collinear quadratic variation in 2D parameter space and linear variation perpendicular to the line that passes through the three collinear points Mechanica uses representative space to calculate interpolation and may not apply the interpolated load, heat load, or prescribed temperature in exactly the way you expect. Click the Preview button on the Interpolation Over Entity dialog box to see a display of vector arrows that show the relative magnitude of the load, heat load, or prescribed temperature at different points on the entity. Structural Temperature Loads Use the Insert>Temperature Load>Structural command in FEM mode to create a thermal load resulting from a temperature change over a geometric entity or set of geometric entities. You can apply the load uniformly across the selection geometry or use a function of coordinates to define the spatial variation. The load can be applied to points, vertices, datum curves, or surfaces. If your model is an assembly, you also have the option of applying the structural load to specific assembly components. Note: To apply the temperature load to an entire assembly, use global temperature loads. 463 Structural and Thermal Simulation - Help Topic Collection When you select Insert>Temperature Load>Structural, and choose Point, Curve, or Surface from the STRUCT TEMP menu, the Structural Temperature Load dialog box appears with the following fields: • • • Name — The name of the load. Member of Set — The name of the load set. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. References — In this area appears the name of the type of entity—point, curve, or surface—you chose. If you already selected valid geometric references before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. Otherwise, use the selector arrow and the regular selection methods to choose the desired geometry. Entity Temperature — Use this area to enter the temperature to which you wish to bring the geometric entity as well as the spatial variation you want Mechanica to use. o Spatial Variation — Define how you want Mechanica to distribute the load by selecting Uniform or Function Of Coordinates from the option menu. If you select Function Of Coordinates, Mechanica displays the f(x) button, enabling you to enter an existing function or create a new function. o Value — Enter the temperature you want to apply to the entity. You can enter a real number or an expression incorporating Pro/ENGINEER parameters. Reference Temperature — Enter the zero stress temperature of your model. The reference temperature is the stress-free temperature of the model—whether that temperature is room temperature or some other temperature that is normal for the model. • • The difference between the entity temperature value and the reference temperature is the amount of temperature change over the model. Structure Loads on Regions If you plan to load a specific surface region, your model needs to include the contour that defines the region. For assemblies, you cannot load geometry that Mechanica merges during a run, such as mated surfaces. You also cannot load geometry associated with merged geometry, such as points associated with mated surfaces. If you cannot avoid placing loads on these geometric entities, you need to work with regions. 464 Structural and Thermal Simulation Example: Bearing Load In a bearing load, the load will be greatest along the vector that defines load direction and will taper toward the edges, as shown below: Example: Bearing Load on an Open Curve In the following illustration, Mechanica distributes the load on an open curve: Sample FNF File for External Temperature The following is a sample FNF file for external temperature. #PTC_FEM_NEUT 3 #DATE 18-Sep-01 10:10:09 %START_SECT : HEADER %TITLE : B2 465 Structural and Thermal Simulation - Help Topic Collection %STATISTICS : 1 0 1 0 8 6 %END_SECT %START_SECT : ELEM_TYPES %ELEM_TYPE 1 DEF : SOLID TETRA LINEAR 4 6 4 %ELEM_TYPE 1 EDGE : 1 1 2 %ELEM_TYPE 1 EDGE : 2 2 3 %ELEM_TYPE 1 EDGE : 3 1 3 %ELEM_TYPE 1 EDGE : 4 1 4 %ELEM_TYPE 1 EDGE : 5 2 4 %ELEM_TYPE 1 EDGE : 6 3 4 %ELEM_TYPE 1 FACE : 1 2 6 5 %ELEM_TYPE 1 FACE : 2 3 6 4 %ELEM_TYPE 1 FACE : 3 1 5 4 %ELEM_TYPE 1 FACE : 4 1 2 3 %END_SECT %START_SECT %NODE 1 DEF %NODE 2 DEF %NODE 3 DEF %NODE 4 DEF %NODE 5 DEF %NODE 6 DEF %NODE 7 DEF %NODE 8 DEF %ELEM 1 DEF %ELEM 2 DEF %ELEM 3 DEF %ELEM 4 DEF %ELEM 5 DEF %ELEM 6 DEF %END_SECT : : : : : : : : : : : : : : : MESH -0.5 -0.5 -0.5 -0.5 -0.5 0.5 -0.5 0.5 0.5 0.5 -0.5 0.5 0.5 0.5 0.5 -0.5 0.5 -0.5 0.5 0.5 -0.5 0.5 -0.5 -0.5 1 1 * 1 4 7 5 1 1 * 2 5 6 3 1 1 * 2 5 1 6 1 1 * 6 1 7 5 1 1 * 2 4 1 5 1 1 * 1 8 7 4 %START_SECT : LOADS %LOAD_TYPE 1 DEF : TEMPERATURE NODE SCALAR %CON_CASE 1 DEF : TestData1 %LOAD 1 DEF : 1 1 %LOAD 1 VAL : 1 0 %LOAD 1 VAL : 2 0.15 %LOAD 1 VAL : 3 0.75 %LOAD 1 VAL : 4 0.4 %LOAD 1 VAL : 5 1 %LOAD 1 VAL : 6 0.6 %LOAD 1 VAL : 7 0.85 %LOAD 1 VAL : 8 0.25 %END_SECT %START_SECT : ANALYSIS %SOLUTION 1 DEF : THERMAL %SOLUTION 1 CON_CASES : 1 %END_SECT %END 466 Structural and Thermal Simulation Example: Bearing Load on a Surface In the following illustration, Mechanica distributes the load on a surface: Strategy: Scaling Results for Centrifugal Loads in a Combined Load Set The omega term in the force calculation that Mechanica uses for centrifugal loads is not linear, due to the following relationship: F(centrifugal) = mass radius omega2 You can correct for this by creating a load set that contains only the centrifugal load and rerunning the analysis with this load set. Then, determine the total load resulting from the centrifugal load set. Using this information, you can determine the true scale factor you need to enter to achieve the desired load scaling. To determine the scale factor, apply the following formula: scale value = (WN/WE)2 Where WN is the acceleration or velocity specified in the load definition and WE is the acceleration or velocity you want to achieve through scaling. Add for Interpolation Use this button to add a new interpolation point. As you select each point, Mechanica: • allows you to select up to four points 467 Structural and Thermal Simulation - Help Topic Collection • • • marks each location you select with an X sequentially numbers the interpolation points displays an entry box on the dialog box in which you can enter a value for the point Structure Loads on Points If you plan to define certain types of loads, you may need to add datum points to your model. Keep the following in mind when applying loads to points: • Forces and moments applied to points — You can select single points, vertices, point features, or patterns of points. Be aware that force and moment loads applied to points can introduce high stress concentrations in your model. Interpolated loads — If you want to apply an interpolated load, you may need to add datum points for the software to use when calculating load variations. Interpolated surface loads require between two and four datum points. You do not need to add datum points for interpolated curve loads because the software uses the end points of the curve as default interpolation points. If you do not want to use the end points, you can add up to four datum points to the curve. • • Total load at point (TLAP) — If you want to apply a total load to a single point, use this option. This creates a distributed load that is statically equivalent to a resultant load at a point. Vector-based or axis-based loads — If you want to apply a load that requires a vector, such as a bearing load, you can define the vector using coordinates or by picking datum points. If you choose the datum point method, you must define two datum points to indicate vector direction. Axis-based loads, such as centrifugal loads, also require two datum points if you want to define the axis using datum points instead of coordinates. • Resultant loads — If you want to review a resultant load, you need to add datum points at the locations for which you want the software to calculate a resultant load. • For most loads, you can add datum points within Mechanica as you define the load. These datum points will be available for your Mechanica sessions only. They are not visible on your part or assembly while you are working at the Pro/ENGINEER level. As an alternative, you can add datum points to your model in Pro/ENGINEER before entering Mechanica. In the latter case, the datum points will be available for all your Pro/ENGINEER sessions as well. 468 Structural and Thermal Simulation Force Per Unit Type Use this option to apply a load to each unit that makes up the entity you selected, where type is either length, area, or volume depending on the model type and type of entity selected for the load. See Force Per Unit Type Guidelines for more information. The units used for force loads are as follows: Model Type/Entity 3D: Curve, Edge, Beam Surface, Face, Shell 2D Axisymmetric: Curve, Edge, 2D Shell Surface, 2D Solid 2D Plane Strain: Curve, Edge, 2D Shell Surface, 2D Solid 2D Plane Stress: Curve, Edge Surface, 2D Plate Force Per Unit Length Force Per Unit Area Force Per Unit Area Force Per Unit Volume Force Per Unit Area Force Per Unit Volume Force Per Unit Length Force Per Unit Area Units The units for moment loads are the units for the force loads multiplied by length. 469 Structural and Thermal Simulation - Help Topic Collection Load Interpolation Use the Load Interpolation dialog box to add, preview, or remove interpolation points, and to enter or edit a value for each point. You can use from two to four interpolation points on the geometry and assign a scale factor to each point. Mechanica selects default interpolation points for some entities, as follows: Entity open curves, edges, beams, 2D shells shells, 2D plates, 2D solids, faces surfaces Default Interpolation Points endpoints corners none If you want different interpolation points than the defaults, you can delete the defaults and create new ones. When planning interpolated loads, be aware of the following: • At least one of the points should have a value other than zero. For interpolated loads, you normally use scale factors that lie between 0 and 1. However, you can use larger values if you want to increase the value or vector of the original load through multiplication. Each value is a scale factor. Mechanica multiplies the force and moment values (for structural loads) or the heat transfer rate value (for heat loads) by the interpolation value at a given location to determine the load vector at that location. You can define the scale factor as either a positive or negative value. If you use a negative value, you reverse the load direction. Additionally, if you express the load value as a negative number and you use a negative scale value, the signs cancel each other and the load value becomes positive. If you enter interpolation points and add scale factors before entering load values, Mechanica enters a default value of 1 for FY. The number of interpolation points you select determines the functional form of the interpolation. • • • • Total Load Use this option to distribute a load along the length or area of the entity such that the integral of the load over the selected entity equals the total prescribed value. For curves (and edges in FEM mode), Mechanica distributes the load as load per arc length. For surfaces, Mechanica distributes the load as load per surface area. 470 Structural and Thermal Simulation Follow these guidelines: • • If you select more than one entity, Mechanica distributes the load equally across all selected entities. For 3D models, Mechanica distributes the total load you enter on the selected entities in the following ways: Entity edges, beams curves Total Load Distributed As load/entity's arc length load/sum of the lengths of the edges that lie on the curve load/area of entity load/sum of the areas of the shells, faces, or 2D plates on the surface shells, faces, 2D plates surfaces Note: You cannot select the Total Load option for a 3D solid. • • • • Because all modeling data for 2D plane strain models is in terms of per unit depth, you enter the total load on a curve, edge, or 2D shell in terms of the total load applied per unit depth. For 2D axisymmetric models, a load on a curve, edge, or 2D shell defines what is physically an area load. You enter the amount of such a load on the surface that the curve, edge, or 2D shell represents. A load on a 2D solid defines what is physically a volume load. You enter this type of load on the body that the 2D solid represents. The total load remains the same even if the length or area changes, either through changes you make to the model or through changes that Mechanica makes during a sensitivity or optimization design study. For example, if you define a load of 100 pounds for a 25x25 inch surface, each 1x1 inch area of the surface sees 0.16 pounds of the load. Should Mechanica optimize the surface such that it shrinks to a 1x1 inch area, the remaining area would see the entire 100 pounds. Thus, although the overall 100-pound load remains steady for the model, a much smaller surface area bears the load. Total Load At Point Use this option on the Force/Moment Load dialog box to apply a total load to a single point. This creates a distributed load that is statically equivalent to a resultant load at a point. The point can either be a predefined datum point on the model or a vertex. Note: You cannot select this option for a 2D axisymmetric model. Use the selector arrow to select a location where you want the total load applied. 471 Structural and Thermal Simulation - Help Topic Collection Remove for Interpolation Use this button to remove interpolation points. When you select one or more interpolation points to remove, Mechanica: • • • removes the interpolation points you selected on the interpolation dialog box, removes the entry boxes that contain the values for the deleted interpolation points renumbers any remaining interpolation points in sequential order How Loads Transfer to Structure This table describes the forms taken by the various loads available in Mechanism Design when you use the Load Export dialog box to create a load set for export to Structure. Exported Mechanism Load Joint Connections Joint reaction force Unassociated TLAPa force at joint point location Unassociated TLAP moment at joint point location Imported Structure Load Joint reaction moment Springs and Dampers Point-to-point spring or damper reaction force Spring or damper reaction force on translational joint axis Spring or damper reaction force on rotational joint axis Damper on Slot-follower Connection Combined normal and tangential reaction forces on slot damper Servo Motors and Force Motors Servo or force motor reaction force and moment on translational joint axis Unassociated TLAP force at intersection of zero reference plane and translation axis Unassociated TLAP force at slot point location Unassociated TLAP force at attachment point Unassociated TLAP force at center of joint axis Unassociated TLAP moment at center of joint axis 472 Structural and Thermal Simulation Servo or force motor reaction moment on rotational joint axis Cam-follower Connections Combined normal and tangential reaction forces at cam contact point Slot-follower Connections Reaction force on slot connection Unassociated TLAP moment at center of joint axis Unassociated TLAP force at cam contact point Unassociated TLAP force at center of slot Gear Pairs Reaction moment for standard gear pair on rotational joint axis Reaction force for rack and pinion gear pair on translational joint axis Force/Torque Forces applied to points Point-to-point forces Unassociated TLAP force at point Unassociated TLAP force at starting point Unassociated TLAP moment at body center of gravity Unassociated TLAP moment at center of joint axis Unassociated TLAP force at center of joint axis Torques applied to bodies Gravity Combined gravitational force and translational component of inertial acceleration Inertial Forces Angular velocity (as Centrifugal1_Vel) and Angular acceleration (as Centrifugal1_Acc) a. TLAP = Total Load at Point Single combined centrifugal load with velocity and acceleration components Gravity acceleration at body center of gravity and the translational component of inertial acceleration 473 Structural and Thermal Simulation - Help Topic Collection Force Per Unit Type Guidelines • If the entity's length or area changes, either through changes you make to the model or through changes Mechanica makes during a sensitivity or optimization design study, the total load on the entity changes accordingly. For example, if you wanted to apply a load of 100 pounds to a 25x25 inch surface using the force per unit method, you would define a load with each 1x1 inch area of the surface seeing 0.16 pound. The cumulative effect of the load is 100 pounds. In this case, if the surface shrank to 1x1 inch during optimization, the remaining area would still see 0.16 pounds. Thus, although the load on the individual unit of area does not change, the original 100-pound surface load drops to 0.16 pounds. • • Because all modeling data for 2D plane strain models is in terms of per unit depth, you enter the total load on a curve, edge, or 2D shell in terms of the total applied per unit depth. For 2D axisymmetric models, a load on a curve, edge, or 2D shell defines what is physically an area load. You enter the amount of such a load as a force per unit area on the surface that the curve, edge, or 2D shell represents. A load on a 2D solid defines what is physically a volume load. You enter this type of load as a force per unit volume on the body that the 2D solid represents. You can apply a force-per-unit load to multiple surfaces. In this case, Mechanica places the same load on each surface unit regardless of the area of the surface. • • From and To Fields for Dir Points & Mag Use these input fields for the Dir Points & Mag option to define the direction of the angular acceleration vector as follows: • • The direction of the load vector is from the point specified in the From field to the point specified in the To field. You fill in these fields by using the selector arrows to choose points or vertices. When you use the selector arrow to specify points for these fields, the software translates the point location into the WCS coordinates of the point you picked, even if a UCS was active when you picked the point. In using the point as a reference location, the software disassociates the vector from the defining points. This means that if the points move during a sensitivity or optimization study, the vector remains unchanged. 474 Structural and Thermal Simulation • • For 2D axisymmetric models, you do not fill in these fields because the angular acceleration vector is always parallel to the WCS Y axis. For 2D plane strain and 2D plane stress models, you use only the To field. The angular acceleration vector passes through that axis location and is perpendicular to the WCS XY plane. The software uses the right-hand rule to determine acceleration direction. Structure Loads on Geometry When you apply loads to geometry, keep the following points in mind: • • • If you place a load on a curve, the load applies to any edges associated with that curve. If you place a load on a surface, the load applies to any elements associated with that surface. A point load can create theoretically infinite stresses (for structural loads) or fluxes (for heat loads) on a shell, solid, 2D solid, or 2D plate. A curve or edge load on a solid element can create theoretically infinite stresses (for structural loads) or fluxes (for heat loads). For a 2D plane strain model a point represents a line. You can apply a load to a point as either a total load or as a load per unit length using the Total Load or Load Per Unit Length options, respectively. Because the depth of the model is considered to be unity, these two options are equivalent. For a 2D axisymmetric model, a point represents a circle. You can apply a load to a point as either a total load or as a load per unit length using the Total Load or Load Per Unit Length options, respectively. For example, if you specify a load of 100 pounds per unit length, the total load on the entire circle will be 100 r pounds, where r is the radius of the circle. But if you specify a load of 100 pounds as the total load, then the total load remains 100 pounds. • • How Structure Imports Loads from Mechanism Design The loads listed in the Mechanism Load Import dialog box in Structure have the same names as in Mechanism Design unless the Mechanism Design name contains too many characters or characters that are invalid in Structure. There are a few points you should keep in mind when using these loads in Structure. • Structure imports the loads, with the exception of the gravity and centrifugal loads, as unassociated Total Load At Point (TLAP) loads. You must associate each load with a geometric reference in order for it to be retained with the model when you complete your session of Structure. When Structure imports loads from Mechanism Design, it creates a datum point for the unassociated TLAP, unless one exists. In the case of loads based on reaction forces on translational joint axes in Mechanism Design, the location of the datum point is at the intersection of the zero reference plane for the selected body and the translational axis. You can change the location of this zero reference plane by using the Joint Axis Settings dialog box in Mechanism Design. 475 • Structural and Thermal Simulation - Help Topic Collection For reaction forces on rotational joint axes, the location of the datum point is at the center of the rotational joint axis. This location is determined by Mechanism Design and not easily modified. • • • Mechanism Design defines loads with respect to the body's LCS. When you import these loads into Structure, the loads are defined with respect to the model's WCS. When you display the direction for a gravity load by highlighting the name in the Mechanism Load Import dialog box, the shaded arrow appears at the center of gravity of the component, but its icon is shown at the model's WCS. Structure combines the angular inertial velocity and acceleration components, called Centrifugal1_Vel and Centrifugal1_Acc, respectively, that are imported from Mechanism Design into a single centrifugal load. When you edit the centrifugal load in Structure, the Centrifugal Load dialog box includes the magnitudes of the velocity and acceleration components. For information on how specific forces and moments transfer from Mechanism Design to Structure loads, see How Loads Transfer to Structure. Interpolated Over Entity Use this option to vary a load linearly, quadratically, or cubically along the entity you selected. You can use this option only if you selected a single entity—edge, curve, or surface—for this load. You cannot define an interpolation in FEM mode. When you select Interpolated Over Entity, the Define button appears on the dialog box. When you click this button, a Load Interpolation dialog box appears, which enables you to: • • • add a new interpolation point remove interpolation points preview an interpolation The interpolation you create is associated with the load and the entity. Load Resultant Dialog Box for Structure Loads Use the Load Resultant dialog box to review the total load for your model. This dialog box appears when you select the Info>Review Total Load command. The dialog box includes the following items: • File — This menu contains the following commands: o Save As — Use this command to save the data on the Load Resultant dialog box in a text file. The information includes the loads list, coordinate system, evaluation point, and resultant forces and moments. The Save As dialog box appears, allowing you to select a filename and directory. The default filename is total_load.inf, and the default directory is the current working directory. o Close — Use this command to exit the dialog box. 476 Structural and Thermal Simulation • • • • • • Select Loads — Use the normal selection methods to select one or more loads that you want to evaluate. You cannot select gravity, centrifugal, or structural temperature loads. After you select the loads, the software displays a list of the load names. Select Coordinate System — Use the normal selection methods to select a Cartesian coordinate system. The software expresses the resultant load in the selected coordinate system. The default is the WCS. Select Evaluation Point — Use the normal selection methods to select a datum point. The software displays the name of the point. The software evaluates the resultant of the selected loads about that datum point. The default is the origin of the selected coordinate system. Compute Load Resultant — When you click this button, the software evaluates the resultant load derived from the selected loads about the selected datum point. Reference Point Location — Displays the X, Y, and Z coordinates of the evaluation point in the selected coordinate system. Load Resultant — Displays the X, Y and Z components of the force (FX, FY, and FZ) and moment (MX, MY, and MZ) of the resultant load. The software does not retain any information on the dialog box when you click OK to exit the dialog box. Mechanism Load Import Dialog Box Use the Insert>Mechanism Loads command to open the Mechanism Load Import dialog box. Use the items on this dialog box to specify which of the loads you imported from Mechanism Design you will include in a load set, and to choose the load set name. When you open the dialog box, force/load and gravity icons corresponding to the imported loads appear on your model. Use the Simulation Display dialog box to control the visibility of these icons. The dialog box includes these items: • Member of Set—The name of the load set. The default name for load sets imported from Mechanism Design is MechanismLoadSetx, where x is a number incremented with each succeeding load set. Place the pointer over the load set name to view the name of the Mechanism Design result set used to generate the loads. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. • Load Info—List of all loads available for import, with the magnitude for each load under Value. Select the check boxes for those loads that you want to include in the selected load set. The units are given in the current unit system. To review the direction of the load, highlight the load name. The software displays a shaded magenta arrow showing the direction of action. For information on how the software imports loads, see How Structure Imports Loads from Mechanism Design. Clear Load Info After Import—Controls whether the imported load information remains in the current session. If you check this box, you can 477 • Structural and Thermal Simulation - Help Topic Collection only carry out one load import in a given session. If you do not check this box, you can import the same load set several times. • • — Selects all the loads in the list. — Deselects all the loads in the list. Guidelines for Spatially Varying Loads • • You can select only one geometric entity when applying an interpolated load. You need a minimum of two datum points to define an interpolated surface load. For interpolated curve loads, Mechanica also requires a minimum of two points, but it uses the curve end points as a default. If you do not want to use the end points, you need to add two datum points to the curve. When calculating function-based loads, Mechanica uses radians as the system of units. To calculate load application, you may need to convert the entity dimensions to radians. For interpolated loads, you normally use scale factors that lie between 0 and 1. However, you can use larger values if you want to increase the value or vector of the original load through multiplication. You can define the scale factor as either a positive or negative value. If you use a negative value, you reverse the load direction. Additionally, if you express the load value as a negative number and you use a negative scale value, the signs cancel each other and the load value becomes positive. For curves, Mechanica assumes the end points of the curve as the first two interpolation points. If you do not want to use these points, you can select other points on the curve. For surfaces, Mechanica does not assume any interpolation points and you need to select each of the points you want to use. If you define interpolation points and add scale factors before you specify a load value, Mechanica assumes a default value of 1. In the case of forces and moments, the software defines this default as an FY = 1 force. • • • • • 478 Structural and Thermal Simulation Example: Pressure Load Mechanica distributes pressure over the entire surface, adjusting the direction of the load to maintain perpendicularity despite orientation changes in the surface, as shown below: Example: Spatially Varying Loads Mechanica distributes the load by multiplying the scale factor by the load magnitude to obtain the load value, or vector, for that point. The software tapers the load from point to point according to the difference between the calculated load value at each interpolation point. 479 Structural and Thermal Simulation - Help Topic Collection For example, the bounding edge of the following model includes an interpolated force load of 100 pounds in the negative Y direction: In this case, the scale values are staggered such that point 3 sees 100% of the load and point 0 sees no load. The points in between see a load that is proportional with their specific scale factors, as calculated in relation to the interpolation point scale factors. The load above has a Force Per Unit Length spatial distribution. If you apply a total load instead, Mechanica normalizes the load throughout the curve such that the total load applied to the curve equals the load value on the dialog box. When applying interpolated loads, Mechanica works in parameter space. Parameter space is representative space, internal to Mechanica's code, in which Mechanica represents model geometry. Mechanica calculates the interpolation in parameter space and then maps the interpolation back to the entity over which the interpolation is defined. This means that Mechanica may not apply the interpolated load in exactly the way you expect. Thus, with interpolated loads, be sure to use the Review button on the Load Interpolation dialog box to verify that Mechanica applied the load as desired. The review function shows the relative load magnitude at different points on the entity. The above example is one of the simplest forms of an interpolated load. Depending on how you use the scale factor in relation to interpolation point location, you can shape interpolated loads in a more complex manner. 480 Structural and Thermal Simulation Preview for Interpolation Use this button on the Interpolation Over Entity dialog box to review an existing interpolation. Mechanica displays an array of vector arrows over the entity showing the relative magnitude of the interpolated load, heat load, or prescribed temperature at different points on the entity. Thermal Loads About Loads Constraints and loads define the real-world environment you expect your model to encounter. Mechanica simulates the behavior of your model under loads you define when performing standard analyses and sensitivity studies for your model. Your model's optimal shape and mass can also depend on the loads you define. You can define loads on your model through the menu structure, the Model Tree, or through relations functions. For structural analysis, a load is a force, moment, pressure, acceleration, velocity, or temperature that you apply to a portion of your model. For thermal analysis, a load is a heat condition applied to a portion of your model. About Heat Loads Heat loads are entity loads available in Thermal only. Use the Insert>Heat Load command to place heat loads on one or more points, edges/curves, surfaces or components and group these loads into sets. Heat loads provide local heat sources and sinks for your model. You can use heat loads to model internal heat generation or flux. If you are working in FEM mode, see Defining Heat Loads (FEM mode) for information. For information on using heat loads with various model types and geometry, see Guidelines for Heat Loads. After you select Insert>Heat Load and select an entity type, the Heat Load dialog box appears. The dialog box contains the following fields: • • • Name — The name of the load. Member of Set — The name of the load set. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. References — Use the selector arrow and the regular selection methods to select the geometric entity to which Mechanica will apply the load. If you selected the geometric entity before entering the dialog box, your selections appear next to the selector arrow when you open the dialog box. 481 Structural and Thermal Simulation - Help Topic Collection You can apply heat loads to the following entities: Point — You can apply a heat load to a single point, or a feature or pattern of points. o Edge/Curve o Surface — If you want to apply a heat load to an internal surface, see Heat Loads on Internal Surfaces. o Component Distribution — Select Total Load or Heat/Time Per Unit Type to specify how Mechanica distributes the heat load across the geometric entity. Total Load is not available if you chose Point. Spatial Variation — Select the spatial variation you want Mechanica to use to distribute the load. This option menu is not available if you chose Point(s). Q — Enter any real number for the total or distributed heat transfer rate. Time Dependent — Select this check box to make your load a function of time. Preview — Use this button to check the load for errors before you leave the dialog box. After you complete the heat load definition by accepting the dialog box, Mechanica places a heat load icon at each location you selected for the heat load. o • • • • • After you create a heat load, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a heat load, Mechanica asks you for confirmation first. Guidelines for Heat Loads If you define a heat load on a point, keep the following points in mind: • • • A point heat load can create theoretically infinite fluxes on a shell, solid, 2D solid, or 2D plate. A curve or edge load on a solid element can create theoretically infinite fluxes. For a 2D plane strain model, a point represents a line, so a point heat load is actually heat/time per unit length along that line. For a 2D axisymmetric model, a point represents a circle, so a point heat load is heat/time per unit length along that circle. Guidelines for Load Sets Understanding Load Sets Every load that you add in the software is part of a load set. A load set is a collection of loads that act together on your model. Load sets cannot contain constraints. You can manage your load sets with the Properties>Load Sets command. When you select this command, the Load Sets dialog box appears with the following items: • 482 New — Opens the Load Set Definition dialog box. Enter a name and optional description for the new load set. Structural and Thermal Simulation Note: You can also access the Load Set Definition dialog box by clicking the New button in the Member of Set area of the Force/Moment Load, Pressure Load, Gravity Load, Centrifugal Load, Global Temperature Load, or Structural Temperature Load dialog boxes. • • • • Copy — Copies the selected load set and adds to the list in the Load Sets dialog box. The new load set includes copies of the same loads as the original load set. Edit — Opens the Load Set Definition dialog box to enable you to modify any information you used to specify the highlighted load set. Delete — Removes the highlighted load set. Description — Displays the optional description that you entered when you created the load set. If you want the flexibility of treating each of your loads or constraints separately, use a unique load and load set name for each load or constraint. Load and constraint sets provide a logical means of organizing your modeling entities so that you can define analyses effectively and clearly. A carefully-considered approach to load and constraint set creation simplifies load and constraint selection when defining your analyses. Although you are free to create a separate load or constraint set for each of your modeling entities, you can greatly reduce the number of selections you need to make when defining your analyses by grouping your loads and constraints into sets. Guidelines for Load Sets If you need more information on what a load set is and why you should group your loads, see Understanding Load Sets. When you create structural or heat load sets, use the following guidelines: • • • • Use names that are 32 characters or fewer. You can use alphanumeric characters and underbars. Names must start with alphabetic characters. The software will not permit you to use a name already used for another load, constraint, or property set. Use names that uniquely and clearly identify the objective, placement, or other key characteristic of the set. If you use the default names, you or other users may have trouble distinguishing the sets later. You can include as many different entities and types of loads as you want within a single load set, with the exception of loads that affect the entire model. You can only include one centrifugal load, gravity load, MEC/T temperature load, or global temperature load per load set. There is no limit to the number of load sets you can create or the number of loads you can include in a load set. If you attempt to delete a point associated with a load or constraint, the software informs you of the association by pointing out that the geometry is referenced by a simulation feature. You can delete the point, but the software also deletes any associated load or constraint. • • 483 Structural and Thermal Simulation - Help Topic Collection • • You can edit and delete the individual loads or constraints that make up a set. You can also edit and delete a constraint set or load set. With constraint and load set editing, the only aspects of the set you can change are the name or the set description. You can remove a given load or constraint from its set by editing the name of the load set or constraint set. Example: Load Set Your goal in creating a given load set or constraint set is to simulate a particular real-world condition. For example, if you were modeling a screw, you might want to create a load set that simulates turning the screw with a screwdriver. In this case, the load set includes the following two loads: To facilitate the application of the load, you add regions on either side of the screw slot. These regions simulate contact sites for the screwdriver as it presses against the slot when you apply torque. You then define two 25-pound loads in opposite directions relative to the Y axis of the coordinate system shown above. The opposition of these loads simulates torque applied to the screw as you twist it. You ensure that both loads are part of a load set called torque by giving them the Member Of Set name torque. Defining Heat Loads Heat/Time Per Unit Type Select this option on the Heat Load dialog box to have Mechanica apply the heat load to each unit of type, where type is either length, area, or volume, depending on model type and type of entity selected for the load. The table lists the units for the heat load by model type and type of entity selected for the load. With this distribution method, the total heat load changes with any change in the entity's length or area. The geometric change may result from changes you make to 484 Structural and Thermal Simulation the model or changes Mechanica makes during a sensitivity or optimization design study. For 2D plane strain and 2D axisymmetric models, a heat load on a curve, edge, or 2D shell defines what is physically an area load. You enter the amount of such a heat load as heat/time per unit area on the surface that the curve, edge, or 2D shell represents. Similarly, a heat load on a 2D solid defines what is physically a volume load. You enter this type of load as heat/time per unit volume on the body that the 2D solid represents. Total Load Use this option on the Heat Load dialog box to distribute a load along the length or area of the entity such that the integral of the load over the selected entity equals the total prescribed value. For curves (and edges in FEM mode), Mechanica distributes the load as load per arc length. For surfaces, Mechanica distributes the load as load per surface area. Follow these guidelines: • With this distribution method, the total heat load remains the same even if the entity's length or area changes. The geometric change may result from changes you make to the model or changes Mechanica makes during a sensitivity or optimization design study. If you select more than one entity, Mechanica places the load you create on each entity. You can apply a heat load to multiple surfaces. In this case, Mechanica distributes the load in such a way that all surfaces carry the heat load proportional to the surface area. Note: You cannot select the Total Load option for a 3D solid. • Mechanica calculates the total load on different entities in the following ways (where Q = heat transfer rate): Entity edges, beams curves Total Load Calculation Q/arc length of entity Q/sum of the lengths of the edges that lie on the curve Q/area of entity • shells, faces, 2D plates 485 Structural and Thermal Simulation - Help Topic Collection Entity surfaces Total Load Calculation Q/sum of the areas of the shells, faces, or 2D plates on the surface For 2D plane strain and 2D axisymmetric models, a load on a curve, edge, or 2D shell defines what is physically an area load. You enter the amount of such a load on the surface that the curve, edge, or 2D shell represents. Similarly, a load on a 2D solid defines what is physically internal heat generation. You enter this type of load on the body that the 2D solid represents. Heat Transfer Rate (Q) Keep the following points in mind when you specify the heat transfer rate on the Heat Load dialog box. For a curve, surface, beam, shell, solid, 2D plate, 2D shell, 2D solid, edge, or face: • • The heat transfer rate is a total or distributed heat transfer rate, depending on the distribution option you selected. You can enter any real number. If you define interpolation points and add scale factors before you specify a load value, Mechanica assumes a default value of 1. The number of interpolation points you select determines the functional form of the interpolation. For all entities, when you are specifying the heat transfer rate: • • To make the loaded entity a heat source for the model, enter a positive value for Q, which adds heat to the model. To make the loaded entity a heat sink for the model, enter a negative Q value, which removes heat from the model. The sign on the heat load icon indicates whether the load is a heat source (+) or heat sink (–). Time Dependent Select the Time Dependent check box on the Heat Load dialog box if your applied load is a function of time. You must then specify that function over the time range that the analysis will run. When you select the Time Dependent check box, the Heat Load dialog box expands to display the f(x) button and entry box in the Temporal Variation area. 486 Structural and Thermal Simulation The dialog box that appears for selecting functions differs depending on the entity you chose: • • If you chose Point, Edge/Curve, or Surface, the Function Definition dialog box appears when you select the f(x) button. On this dialog box, you name and define the time function for your heat load. If you chose Component, the Functions dialog box appears when you select the f(x) button. Note: The functions you access if you select Component are the same as the FEM mode functions. Time dependence functions for heat load (Q) values are multipliers. When you make a heat load time dependent, its computed value is Q times the time dependence function. If you have also specified a spatial interpolation, the heat load's computed value is Q times the time dependence function times the spatial interpolation. There is no default value for the time dependence function. To Define Heat Loads This procedure is for defining heat loads for points, edges/curves, or surfaces. If you want to define a heat load for a component, see To Define Heat Loads for Components. 1. Select Insert>Heat Load or click . 2. Select Point, Edge/Curve, Surface, or Component, as appropriate. After you select the type of entity you want to load, the Heat Load dialog box appears. 3. Enter a name for the load, or use the default name. 4. Select an existing load set from the Member Of Set area or use the New button to create a new load set. 5. Click and use the normal selection methods to select the particular entity that this load will be associated with. If the desired entity is an internal surface, see Heat Loads on Internal Surfaces. 6. Depending on the type of entity you selected, you will provide information for one or both of the following: o Distribution o Spatial Variation 7. Enter the heat transfer rate in the Q entry box. 8. To specify a time-dependent heat load, select the Time Dependent check box. Then click the f(x) button. Mechanica displays the Functions dialog box. 487 Structural and Thermal Simulation - Help Topic Collection 9. Select an existing function or click New or Edit to display the Function Definition dialog box on which you can define or edit the time function for your heat load. Click OK. 10. If you want to display the load you just defined, click the Preview button. Mechanica displays the load distribution and direction using arrows. 11. Click OK to accept the dialog box. If Mechanica identifies any problems with the way you defined the load, it displays a message box informing you of the situation. If Mechanica does not encounter any definition problems, it applies the loads you specified to all the entities you selected. Mechanica also adds a heat load icon to the geometry you are loading. Defining Component Heat Loads Defining Heat Loads for Components Use the Heat Loads menu to place heat loads on one or more components of a 3D model and group these loads into sets. Heat loads provide local heat sources and sinks for your model. You can use heat loads to model internal heat generation or flux. If you are working in FEM mode, see Defining Heat Loads (FEM mode) for information. Mechanica does not support component heat loads for 2D models. When you choose Component on the Heat Loads menu, the Volume Heat Load dialog box appears. The dialog box includes the following: • • • Name — The name of the load. Member of Set — The name of the load set. References — Use this area to select the component to which Mechanica will apply the load. This area is available only if your model is an assembly. If your model is not an assembly and you chose component, Mechanica applies the load to the entire component. If you selected the component before entering the dialog box, the component name appears next to the selector arrow when you open the dialog box. Heat (Q) — Use this area to specify the value of the heat load. Enter any real number for the total or distributed heat transfer rate. Time Dependent — Select this check box to make your load a function of time. • • After you create a heat load, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a heat load, the software asks you for confirmation first. You can also review the total heat load. 488 Structural and Thermal Simulation Heat Transfer Rate (Q) Keep the following points in mind when you specify the heat transfer rate on the Heat Load dialog box. For a curve, surface, beam, shell, solid, 2D plate, 2D shell, 2D solid, edge, or face: • • The heat transfer rate is a total or distributed heat transfer rate, depending on the distribution option you selected. You can enter any real number. If you define interpolation points and add scale factors before you specify a load value, Mechanica assumes a default value of 1. The number of interpolation points you select determines the functional form of the interpolation. For all entities, when you are specifying the heat transfer rate: • • To make the loaded entity a heat source for the model, enter a positive value for Q, which adds heat to the model. To make the loaded entity a heat sink for the model, enter a negative Q value, which removes heat from the model. The sign on the heat load icon indicates whether the load is a heat source (+) or heat sink (–). Time Dependent Select the Time Dependent check box on the Heat Load dialog box if your applied load is a function of time. You must then specify that function over the time range that the analysis will run. When you select the Time Dependent check box, the Heat Load dialog box expands to display the f(x) button and entry box in the Temporal Variation area. The dialog box that appears for selecting functions differs depending on the entity you chose: • • If you chose Point, Edge/Curve, or Surface, the Function Definition dialog box appears when you select the f(x) button. On this dialog box, you name and define the time function for your heat load. If you chose Component, the Functions dialog box appears when you select the f(x) button. Note: The functions you access if you select Component are the same as the FEM mode functions. Time dependence functions for heat load (Q) values are multipliers. When you make a heat load time dependent, its computed value is Q times the time dependence function. If you have also specified a spatial interpolation, the heat load's computed value is Q times the time dependence function times the spatial interpolation. 489 Structural and Thermal Simulation - Help Topic Collection There is no default value for the time dependence function. To Define Heat Loads for Components This procedure is for applying a heat load to a component in native mode Thermal. For the FEM mode procedure, see To Define Heat Loads (FEM mode). 1. Select Insert>Heat Load or click 2. Select Component. . After you select Component, the Volume Heat Load dialog box appears. 3. Enter a name for the heat load, or use the default name. 4. Select an existing load set from the Member Of Load Set area or use the New button to create a new load set. 5. Click and select the component on which you want to place the load. 6. Enter a value. 7. To specify a time-dependent heat load, select the Time Dependent check box, and then click the f(x) button. Select or modify an existing function or create a new function using the Functions dialog box. Click Close when you are finished with functions. 8. When you have finished defining the heat load, click OK to accept the dialog box. If Mechanica identifies any problems with the way you define the load, it displays a message box informing you of the situation. If Mechanica does not encounter any definition problems, it applies the load you specified. Mechanica also adds a heat load icon to the component. FEM Heat Loads Defining Heat Loads (FEM mode) Heat loads are entity loads available in Thermal only. Use the Insert>Heat Load command to place heat loads on one or more points, edges/curves, surfaces, or components and group these loads into sets. Heat loads provide local heat sources and sinks for your model. You can use heat loads to model internal heat generation or flux. After you select Insert>Heat Load and select an entity type in FEM mode Thermal, the Heat Load dialog box appears with the following items: • • Name — The name of the load. Member of Set — The name of the load set. You can select an existing load set from the drop-down list, or create a new set by clicking the New button to display the Load Set Definition dialog box. 490 Structural and Thermal Simulation • • References — Use this area to select the entities to which Mechanica will apply the load. You can also select the entities before you open the dialog box. This area is not available if you select Component and your model is a part. Use the selector arrow and the normal selection methods to select one or more of these entities: o Point(s) — You can select single points, feature of points, or point patterns. o Edge(s)/Curve(s) o Surface(s) o Component Heat (Q) — Use this area to specify the following: o Distribution — Select Total Load or Heat/Time Per Unit Type to specify how Mechanica distributes the heat load across the geometric entity. You cannot select a distribution if you chose Point or Component. o Spatial Variation — Select the spatial variation you want Mechanica to use to distribute the load. This area is not available if you chose Edge/Curve. o Value — Enter any real number for the total or distributed heat transfer rate. After you create a heat load, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a heat load, the software asks you for confirmation first. You also review the total heat load. To Define Heat Loads (FEM mode) 1. Select Insert>Heat Load. or click . 2. Select Point, Edge/Curve, Surface, or Component as appropriate. After you select the entity you want to load, the Heat Loads dialog box appears. 3. Enter a name for the load, or use the default name. 4. Select an existing load set from the Member Of Set area or use the New button to create a new load set. 5. If you did not select geometric entities as references before you opened the dialog box, click in the References area and use the normal selection methods to select the particular entity that this load is to be associated with. 6. Depending on the selected type of entity, provide information for some or all of the following: o Distribution o Spatial Variation o Value 7. Click OK to accept the dialog box. If Mechanica identifies any problems with the way you defined the load, it displays a message box informing you of the situation. 491 Structural and Thermal Simulation - Help Topic Collection If Mechanica does not encounter any definition problems, it applies the loads you specified to all the entities you selected. Mechanica also adds a heat load icon to the geometry you are loading. Reviewing Total Heat Loads Use the Info>Review Total Load command in Thermal to verify that the combination of heat loads is what you expect it to be. It may be helpful to look at a combination of loads before analyzing your model if you are concerned about the actual load the model will see during a multiload analysis. The total heat load review function is available for Thermal heat loads only. You cannot use this function to review a global or MEC/T temperature load in Structure. Note: For information on reviewing load resultants in Structure, see Reviewing Resultant Loads. To Review Total Heat Loads 1. Select Info>Review Total Load. The Load Resultant dialog box appears. 2. Click in the Select Loads area and select the load icon for each load you want to review. If you want to review the total heat load that results from several loads, use the normal selection methods to select all desired load icons. 3. Click the Compute Load Resultant button. The software displays the resultant value in the Load Resultant area. 4. If you want to save the review as a text file, select File>Save As and enter a filename and directory, or accept the defaults. 5. Click OK to close the dialog box. Load Resultant Dialog Box for Heat Loads Use the Load Resultant dialog box in Thermal to review the total combined heat loads for your model. This dialog box appears when you select the Info>Review Total Load command. The dialog box includes the following items: • File — This menu includes the following items: o Save As — Use this command to save the data on the Load Resultant dialog box in a text file. The information includes the load list and total value of the combined heat loads. The Save As dialog box appears, allowing you to select a filename and directory. The default filename is total_load.inf, and the default directory is the current working directory. o Close — Use this command to exit the dialog box. Select Loads — Use the normal selection methods to select the heat loads that you want to evaluate. After you select the loads, the software displays a list of the load names. Compute Load Resultant — When you click this button, the software calculates the total of the selected heat loads. • • 492 Structural and Thermal Simulation • Load Resultant — Displays the value of the combined heat loads. The software does not retain any information on the dialog box when you click OK to exit the dialog box. Heat Loads on Internal Surfaces In Mechanica you can apply heat loads to internal as well as external surfaces. The following illustration shows two kinds of internal surfaces to which you can apply heat loads: • • A surface that is mated to another surface—surface region bc or the internal portion of mated surface ab. An internal surface of a volume region—the bottom surface of volume region d. To define a heat load for surface a, which would also include the mated portion of the surface, you would select surface a as the reference. To define a heat load for mated surface bc, you would first create a surface region for the portion of surface c that is mated to surface b. To define a heat load for the bottom surface of volume region d, you would first create the volume region. 493 Structural and Thermal Simulation - Help Topic Collection Units According to Model Type and Entity Model Type and Entity 3D: Curve, Edge, Beam Surface, Face, Shell Solid 2D Axisymmetric: Curve, Edge, 2D Shell Surface, 2D Solid 2D Plane Strain: Curve, Edge, 2D Shell Surface, 2D Solid 2D Plane Stress: Curve, Edge Surface, 2D Plate Heat/Time Per Unit Length Heat/Time Per Unit Area Heat/Time Per Unit Area Heat/Time Per Unit Volume Heat/Time Per Unit Area Heat/Time Per Unit Volume Heat/Time Per Unit Length Heat/Time Per Unit Area Heat/Time Per Unit Volume Units Measures About Simulation Measures Use the Insert>Simulation Measure command to create and assign native mode measures. Used properly, measures serve as a powerful tool for analyzing your model's behavior. A measure is a scalar quantity of interest that Mechanica calculates during analyses and design studies. During analysis, you can use measures to monitor your model's performance in terms of particular engineering criteria. For example, if you were interested in studying the ability of an aluminum connector to withstand pull, you might use maximum von Mises stress as a measure. This measure would provide information on whether the aluminum yielded under the conditions simulated during the analysis. 494 Structural and Thermal Simulation See Uses of Measures for more information on the wide range of functions for which you can use measures. See these topics for information on creating measures: • • Measure Basics — fundamentals you should know before you start Measures Dialog Box — the dialog box that appears when you select Insert>Simulation Measure. You use it to create, edit, delete, and copy measures. This dialog box also appears when you are defining analyses, design studies, or a result window. Use it to review and select measures. For additional information on measures, see the topic: Results Available for Measures — the types of measure results you can access for different types of design studies Uses of Measures With measures, you can perform specific evaluations of aspects such as tensile, compressive, and shear strength, rotational flexibility, mass changes, refractive behavior, and so forth. You can use measures to do the following: • • • • Set up measures to monitor specific aspects of your model's performance. For instance, you might want to know the stress tangent to a fillet's radius for the later calculation of fatigue. Use measures as convergence criteria for an analysis, or as a goal or a limit in a design study. You also use measures to measure sensitivity to parameter changes in a local or global sensitivity design study. Use measures to determine how much a shape change affects a particular quantity in your model. As an example, you can see how much changing the radius of a fillet increases or decreases von Mises stress at the fillet. You can also use measures to monitor your model's performance in dynamic situations. For instance, you can set up a measure at a particular point on the model to act as an accelerometer, gauging the rate of acceleration at that point during a dynamic analysis. You can also use dynamic measures to determine model velocity or position. Measure Basics As analysis packages, Structure and Thermal have different goals. Understanding the implications of this difference will help you understand the types of measures you can apply as well as how to use those measures to obtain the information you are interested in. • Structure — Mechanica focuses on structural stresses. Although you can apply temperature loads to your model, you can only obtain information on how the structure of the model behaves at a particular temperature—not on 495 Structural and Thermal Simulation - Help Topic Collection • how heat flows through your model. Therefore, while you can measure structural stresses in your model, you cannot measure model temperature. Thermal — Mechanica focuses on thermal behavior. Even though you can obtain information on how your model reacts to temperature, you cannot use Thermal to examine structural stresses resulting from the thermal conditions you applied to your model. In other words, you can measure thermal data, but not structural data. Regardless of the Mechanica product you are working with, there are several aspects of measures you should be aware of when deciding which measures to use or define for your model. To learn about these aspects, see the following: • • • • • • Guidelines for Measures Predefined, User-Defined, and Automatically-Defined Measures Global and Local Measures Parameter-Based Measures Coordinate Systems and Measures Measures and Output Guidelines for Measures • • • • You cannot use the same name for both a measure and a parameter. You cannot create a new measure that is identical to a predefined measure, unless you associate the measure with a UCS. If you delete any entity associated with a local measure, Mechanica automatically deletes the measure even if other entities are still associated. You cannot delete a predefined measure or use the name of a predefined measure for a custom measure. Predefined, User-Defined, and AutomaticallyDefined Measures Mechanica uses three types of measures—predefined, user-defined, and automatically-defined: • Predefined — For each product, Mechanica provides a set of predefined measures appropriate for the goal of the product. For example, among its various predefined measures: o Structure — provides von Mises stress, maximum principal stress, and maximum displacement magnitude measures o Thermal — provides such measures as maximum heat flux magnitude, maximum and minimum temperatures, and so forth Predefined measures cover a wide variety of the quantities you might want to evaluate or use as criteria for your model. All predefined measures apply to the entire model and, thus, are not location-specific. When it analyzes your model, Mechanica automatically calculates any predefined measure appropriate for the analysis type. 496 Structural and Thermal Simulation • User-Defined — You can also create user-defined measures for your model. These measures are often called custom measures. User-defined measures look at many of the same quantities as the predefined measures, but provide additional flexibility and functionality. For instance, user-defined measures provide a means of observing a location-specific, time-specific, or frequencyspecific quantity. As with predefined measures, Mechanica automatically calculates all relevant user-defined measures during analysis. For information on when to create user-defined measures, see Reasons to Create User-Defined Measures. • Automatically Defined — In addition, Mechanica automatically defines a limited set of measures that are specific to particular modeling entities. Mechanica creates automatically-defined measures only when you add a modeling entity—such as contact regions or fasteners—that requires the measure. If you delete the modeling entity, Mechanica removes the automatically-defined measure from the model. Although Mechanica creates these entity-dependent measures automatically, it treats some of these measures—those for contact regions—as a form of userdefined measure, placing these measures in the User-Defined area of any measure selection lists. Other automatically defined measures, such as those for fasteners, appear in the Predefined area instead. Predefined Measures When using predefined measures, note that: • • • • Each model contains a set of predefined measures associated with the WCS. All predefined measures apply to the entire model. Mechanica automatically calculates predefined measures of the appropriate type for each analysis and design study. You cannot delete a predefined measure. For lists of predefined measures, see: • • Predefined Measures in Structure Predefined Measures in Thermal 497 Structural and Thermal Simulation - Help Topic Collection Predefined Measures in Structure This table lists predefined measures used in Structure. Name buck_load_factor Description load factor for buckling mode com_x WCS X coordinate of center of mass com_y WCS Y coordinate of center of mass com_z WCS Z coordinate of center of mass contact_area total contact area over all contact regions in the model maximum pressure over all contact regions in the model WCS XX component of moment of inertia contact_max_pres inertia_xx inertia_xy WCS XY component of moment of inertia inertia_xz WCS XZ component of moment of inertia inertia_yy WCS YY component of moment of inertia inertia_yz WCS YZ component of moment of inertia inertia_zz WCS ZZ component of moment of inertia max_beam_bending maximum beam bending stress over model max_beam_tensile maximum beam tensile stress over model 498 Structural and Thermal Simulation Name max_beam_torsiona Description maximum beam torsion stress over model max_beam_totala maximum beam tensile plus bending stress over model maximum displacement over model max_disp_magb max_disp_x maximum WCS X displacement over model max_disp_y maximum WCS Y displacement over model max_disp_z maximum WCS Z displacement over model max_prin_magb maximum magnitude principal stress over model max_rot_magb maximum rotation magnitude over model max_rot_x maximum over model of rotations about WCS X axis maximum over model of rotations about WCS Y axis maximum over model of rotations about WCS Z axis most positive principal stress over model max_rot_y max_rot_z max_stress_prinb max_stress_vmb maximum von Mises stress over model max_stress_xx maximum WCS XX stress component over model max_stress_xy maximum WCS XY stress component over model 499 Structural and Thermal Simulation - Help Topic Collection Name max_stress_xz Description maximum WCS XZ stress component over model max_stress_yy maximum WCS YY stress component over model max_stress_yz maximum WCS YZ stress component over model max_stress_zz maximum WCS ZZ stress component over model min_stress_prinb least positive principal stress over model modal_frequency frequency of vibration mode strain_energy total strain energy of model total_cost total_mass total model cost total model mass a. Mechanica does not calculate these measures for any dynamic analyses. b. Mechanica does not calculate these measures for dynamic random analyses. 500 Structural and Thermal Simulation Predefined Measures in Thermal This table lists the predefined measures used in Thermal. Name energy_norm Description max_dyn_flux_mag maximum heat flux magnitude over model at each time step maximum temperature over model at each time step minimum temperature over model at each time step maximum heat flux magnitude over model max_dyn_temperature min_dyn_temperature max_flux_mag max_flux_x maximum heat flux over model in WCS X direction max_flux_y maximum heat flux over model in WCS Y direction max_flux_z maximum heat flux over model in WCS Z direction max_grad_mag maximum temperature gradient magnitude over model maximum temperature gradient over model in WCS X direction maximum temperature gradient over model in WCS Y direction maximum temperature gradient over model in WCS Z direction maximum temperature over model max_grad_x max_grad_y max_grad_z max_temperature min_temperature minimum temperature over model 501 Structural and Thermal Simulation - Help Topic Collection Name total_cost Description total model cost total_mass total model mass User-Defined Measures To define measures that are a function of time, frequency, local measures, or measures relative to a coordinate system other than the WCS, you need to create a user-defined measure. You cannot use the name of a predefined measure for a new measure, or create a new measure that is identical to a predefined measure, unless you associate the measure with a UCS. Measures you define may apply to the entire model, to an entity or entities you select (the type and number of entities you can select depend on how you define the measure), or to an area near a point. Keep in mind the following, when you begin working with the user-defined measures: • • • If you plan to make a measure relative to a coordinate system other than the WCS, you need to have that coordinate system in place. If you plan to place a measure at a specific point on an exterior surface, your part needs to include a datum point at that location unless the location is a vertex. If you plan to place a point measure on a shell model surface that Mechanica may compress during analysis, see Model Entities and Idealizations to learn about how Mechanica processes loads placed on compressed surfaces. For more information about creating user-defined measures for different types of analyses, read the following: • • • User-Defined Measures for Basic Analyses User-Defined Measures for Dynamic Analyses User-Defined Measures for Thermal Analyses. For information on how to create measures, see Measures Dialog Box. Reasons to Create User-Defined Measures For most purposes, predefined measures are sufficient. In the following cases, however, you should consider creating a user-defined measure: • • When you cannot achieve convergence using predefined measures When you cannot get any results for certain types of analyses, such as dynamic analyses 502 Structural and Thermal Simulation • • • • • • When you want to make global and local sensitivity graphs When you would like to monitor a model quantity over time or as a function of frequency. For more information, see Quantity — Dynamic Analyses. When you plan to perform transient thermal analyses and would like to monitor a model quantity over time. For more information, see Quantity — Thermal Analyses. When you want to define a Pro/ENGINEER parameter as a measure. For more information, see Parameter-Based Measures. When you want to measure a quantity at a location of interest, such as a point that may experience high stress. For more information, see Global and Local Measures. When you want to define the components of a measure quantity, such as stress, relative to a coordinate system other than the WCS. For more information, see Coordinate Systems and Measures. If you plan to add user-defined measures to your model rather than use Mechanica's predefined measures, refer to User-Defined Measures. Note that you cannot use the name of a predefined measure for a user-defined measure. Automatically-Defined Measures This table lists automatically-defined measures. Items in italics are variables— typically an entity name or internal identifier. Automatically-defined measures are currently available for Structure only. Name cntRgn_xxxcntArea Description contact area for contact region xxx cntRgn_xxxmaxPres max pressure for contact region xxx fastener_tensile_force a tensile force for the named fastener fastener_tensile_stress a tensile stress for the named fastener fastener_shear_force a shear force for the named fastener fastener_shear_stress a shear stress for the named fastener fastener_separation_stress a separation stress for the named fastener 503 Structural and Thermal Simulation - Help Topic Collection a. This table shows the static form of these measures. Mechanica computes the static form of these measures for static, prestress static, contact, and dynamic shock analyses. If "_d" appears as a measure name suffix, the measure is the dynamic form. Mechanica computes the dynamic form of these measures for dynamic random, dynamic frequency, and dynamic time analyses. Mechanica tracks three of the fastener measures—fastener_tensile_force, fastener_tensile_stress, and fastener_separation_stress—only for advanced fasteners that include a preload. The fastener_separation_stress measure tracks normal stresses on the inside surfaces of the fastened components. This measure determines whether the model maintains component separation properly as the preloaded fastener compresses the components. For proper separation, the normal stresses must remain less than zero during analysis. Values of zero or greater mean that there is no compression between the components and the components are separating. To learn more about how Mechanica creates this measure, see Fastener Preloads. Note: Mechanica does not calculate the fastener_separation_stress measure for dynamic random or dynamic shock analyses. Global and Local Measures Mechanica treats all predefined measures as though they apply to the entire model. You can think of this type of measure as a global measure. If you add datum points to your model's surface, you can create user-defined measures at any of those points. Think of this type of measure as a local measure. Mechanica provides the following types of local measures that you can apply at or near selected points: • • Point measures Near Point measures You can also create other types of local measures that reference your model's idealizations, layers, or geometry. With any type of local measures, Mechanica evaluates the measure quantity relative to a particular location on the model. Point Measures Mechanica evaluates the measure quantity at the application point only. Thus, the quantity that Mechanica reports for the measure is specific to the point and contains no direct information on the area immediately surrounding the point. However, you can make inferences about the surrounding area by looking at a fringe plot for the desired measure quantity and performing a dynamic query. For information about fringe plots, see Fringe Display Type. 504 Structural and Thermal Simulation Near Point Measures Mechanica evaluates the measure quantity at sampling points within a user-specified radius of the application point. In this case, the quantity that Mechanica reports for the measure yields information on the area surrounding the point. For Near Point measures, Mechanica develops the radius you specify as a threedimensional sphere. Thus, the portion of the model this measure considers depends on the type, as well as the contour, of your model. For solid models, a Near Point measure samples the interior of your model as well as its surfaces. For shell and beam models, sampling is one- or two-dimensional, as determined by model geometry. If you specify a large radius that intersects more than one portion of the model, Mechanica samples only the portion of the model that contains the application point. Mechanica determines the sampling points from the plotting grid you specify for your analysis. The higher the number you specify for your plotting grid, the greater the number of sampling points and the greater the refinement of the analysis results. For more information on plotting grids, see Output Options for Structural Analyses. The Near Point option is available for stress, strain, heat flux, and temperature gradient measure quantities. You can only use Near Point if you select a Maximum, Minimum, or Maximum Abs spatial evaluation method for one of these quantities. For more information on spatial evaluation methods, see User-Defined Measures for Basic Analyses. Mechanica reports a single value for the quantity you select. This value reflects the maximum, minimum, or absolute maximum found among the sampled points. Mechanica does not provide the location of the point where the value occurred. Parameter-Based Measures To enhance product versatility, Mechanica enables you to use dependent Pro/ENGINEER parameters as measures. Parameter-based measures provide you with a greater degree of flexibility in how you define measures and the types of measure quantities you can ask Mechanica to evaluate. You can use parameter-based measures for the following functions: • • • • • Obtaining analysis and study results specific to a Pro/ENGINEER parameter Obtaining analysis and study results for a specialized Pro/ENGINEER quantity Setting up optimization goals Setting up optimization limits Setting up parameters for use with regeneration analyses For information you should know before defining parameter-based measures, see Parameter-Based Measure Basics. 505 Structural and Thermal Simulation - Help Topic Collection Parameter-Based Measure Basics When defining parameter-based measures, keep the following points in mind: • Parameter-based measures can only reference dependent Pro/ENGINEER parameters. Thus, when defining this type of measure, be sure to select only those Pro/ENGINEER parameters that you created as relations. Selecting any other type of Pro/ENGINEER parameter will result in problems during your design studies. Parameter-based measures do not provide any time or frequency evaluation capabilities. Mechanica calculates parameter-based measures for all analysis types. As with other Mechanica measures, parameter-based measures are scalar— they do not provide explicit vector data. Mechanica limits measure names to 16 characters. You can use alphanumeric characters and underbars only. Names must always start with alphabetic characters. Because Mechanica uses the Pro/ENGINEER parameter name as the measure name, always observe these naming conventions when creating Pro/ENGINEER parameters that you plan to use as measures. If your Pro/ENGINEER parameter name is too long, Mechanica will truncate it. • • • • Results Specific to a Pro/ENGINEER-Based Parameter You can use a parameter-based measure to obtain analysis and study results specific to a Pro/ENGINEER parameter. For example, if you want to examine how a change in Young's modulus affects model displacement, you can define Young's modulus as a Pro/ENGINEER parameter and also create a measure for that parameter. You can then run a global sensitivity study. When the study is complete, you can ask Mechanica to graph von Mises stress against Young's modulus. If you had not defined the Young's modulus parameter as a measure, you would not have been able to obtain any specific results for Young's modulus. Any conclusions that you reached concerning the effect of a Young's modulus change would have been through inference rather than direct knowledge. 506 Structural and Thermal Simulation Results for a Specialized Pro/ENGINEER Quantity You can use a parameter-based measure to obtain analysis and study results for a specialized Pro/ENGINEER quantity. Pro/ENGINEER computes certain values that fall outside the realm of Mechanica. For example, Pro/ENGINEER can measure the following quantities: • • • • • curve length area angle distance diameter If you are interested in evaluating one of these quantities, you can define the quantity as a Pro/ENGINEER parameter, create an associated Mechanica measure, and run an analysis or study on your model. You can then study how the quantity behaved during the analysis, or how it changed during the study. Setting Up Optimization Goals You can use a parameter-based measure as the goal of an optimization study. This functionality proves handy if you want to run an optimization study based on a regeneration analysis or define a goal not normally available through Mechanica. For example, although you cannot directly define geometry as a measure in Mechanica, you can define certain types of geometry—such as curve length, surface area, and distance measures—as measures in Pro/ENGINEER. Thus, if you want to set up an optimization study that maximizes the length of a rod while maintaining certain frequency limits, you can start by defining a Pro/ENGINEER parameter to control the curve length of the rod. You can then create a Mechanica measure based on this parameter. After you create the curve length measure, you can define an optimization study that uses the curve length measure as a goal and the frequency range as a limit. For more information on defining goals for optimization studies, see Goal. Setting Up Optimization Limits You can use a parameter-based measure as the limit for an optimization study. You use this functionality when you want to run an optimization based on a regeneration analysis or want to define a limit not normally available through Mechanica, such as a dimensional limit. For example, if you want to reduce the mass of a part while ensuring that one of the model's dimensions does not become too small, you can create a Pro/ENGINEER parameter for the dimension. You can then create a Mechanica measure based on this parameter. 507 Structural and Thermal Simulation - Help Topic Collection After you create the dimension measure, you can define an optimization study that uses the dimension measure as a limit, and prevents the measure from dropping below the value you specify. For more information on defining limits for optimization studies, see Limits on Measures. Setting Up Parameters for Regeneration Analyses You can set up parameter-based measures for use with regeneration analyses. A regeneration analysis is a predefined analysis that regenerates your Pro/ENGINEER part. Regeneration analyses do not utilize several of Mechanica's more resourceintensive functions, so this type of analysis provides very rapid results. You can select regeneration analyses as the basis for the following design studies: • • • local sensitivity studies global sensitivity studies optimization studies If you plan to run a design study that relies on a regeneration analysis, note that the only result quantities available are measures and, for optimization studies, shape histories. In other words, the results you will view most typically are graphs of measures relative to design parameters. Further, regeneration analysis does not engage the engine to calculate typical Mechanica measures such as von Mises stress. The only measures it calculates are parameter-based measures. Thus, you should be sure to define parameter-based measures for the model. If you do not, you will be unable to review the results of the study. In addition, if you want to run an optimization study based on a regeneration analysis, you must define your goals and limits as parameter-based measures. If you choose to run a regeneration analysis in your current Pro/ENGINEER session and not in a separate session, the shape change is performed directly on the model in Pro/ENGINEER's memory. Using this method enables you to complete a study faster than running regeneration in a separate session. When defining parameter-based measures, you should be familiar with basic points. Example: Using Parameter-Based Measures To give you a better idea of how you might use parameter-based measures in a design study, assume you are designing a fan and want to quickly find a blade design that uses the minimum amount of material without altering blade thickness or reducing the blade's top surface area below the 25 square inches you need to ensure the proper air flow rate. 508 Structural and Thermal Simulation The fan is as follows: In this case, you might define an optimization design study using the following: • • • Goal — Use a parameter-based measure for part mass. Limit — Use a parameter-based measure for surface area. Parameters — Create three Pro/ENGINEER parameters for the model—one each for d0, d1, and d2. Parameter-Based Measures — Parameters Create three Pro/ENGINEER parameters for the model—one each for d0, d1, and d2. You name these parameters radius, width, and length. Notice that you do not create a parameter for the thickness of the blade, d3. After you define these parameters, you create design parameters in Mechanica for each of the three Pro/ENGINEER parameters. For more information on creating design parameters, see Types of Design Parameters and Pro/ENGINEER Parameters. Now, you create an optimization study whose goal is to minimize the mass measure while observing a limit on the bladesurf measure to keep it above 25 square inches. During the study, you allow Mechanica to vary the radius, width, and length design parameters in an effort to reduce the blade mass, and therefore, material cost. Because this study relies exclusively on parameter-based measures, Mechanica runs a regeneration analysis for the optimization. As a result, your study will run very quickly and give you a good idea of your best initial design from a geometric perspective. You can then work with other types of measures, analyses, and studies 509 Structural and Thermal Simulation - Help Topic Collection to determine how your model behaves under the loads, constraints, and other conditions you define. Parameter-Based Measures — Goal Use a parameter-based measure for part mass. To set up this parameter, you define the Pro/ENGINEER parameter as the following relation: mass=mp_mass("") Here, you define the mass parameter as equal to the mp_mass Pro/ENGINEER system parameter. You use the ("") portion of the equation to indicate that you want Mechanica to measure the mass for the current part. After you define the Pro/ENGINEER parameter, you create a measure in Mechanica that calls the Pro/ENGINEER parameter mass. Parameter-Based Measures — Limit Use a parameter-based measure for surface area. To set up this parameter, you create a Pro/ENGINEER driven parameter that measures the area of the top surface of your fan blade. Do this by creating a feature from an analysis measure that evaluates the surface area, and then create a relation based on the feature. The relation can be accessed in Mechanica as a Pro/ENGINEER driven parameter. To create a feature, select the Pro/ENGINEER command Analysis>Measure. On the Measure dialog box select Area under Type and Surface under Definition, and select a surface on your model. Pro/ENGINEER displays the value of the area. Define the measure as a feature by clicking the Add Feature button, and name this feature topsurf. For more information on analysis measures, search the Fundamentals functional area in the Pro/ENGINEER Help system. To create a relation, select the Tools>Relations command. On the Relations dialog box, select Feature from the Look in pull-down list and select topsurf from the Model Tree. Select the Insert>From Screen command and, from the resulting dialog box, select Feature from the Look in pull-down menu. Choose topsurf and click the Insert Selected button. Pro/ENGINEER adds the parameter to the text entry area of the Relations dialog box. Add the name bladesurf to yield the following relation: bladesurf=AREA:FID_TOPSURF After you define this relation, you create a measure in Mechanica that references the Pro/ENGINEER parameter bladesurf. By default, Mechanica names this measure bladesurf. 510 Structural and Thermal Simulation Coordinate Systems and Measures In Mechanica, most measures bear an implicit or explicit relationship to a coordinate system, whether that coordinate system is the WCS or a coordinate system you defined as current. When considering measures and their relationship to coordinate systems, be aware that all predefined measures that involve component directions use the WCS as their reference. If you want a measure relative to a coordinate system other than the WCS, you must define a custom measure. Before defining the measure, you need to define the desired coordinate system. If you are using a cylindrical or spherical coordinate system to define a custom measure, Mechanica expresses measure components differently, depending on the coordinate system's type. The following is a chart that defines the component nomenclature for all coordinate system types: Cartesian X Y Z Cylindrical R T Z Spherical R T P Mechanica expresses displacement measures associated with the following directions: • • cylindrical coordinates in the T direction spherical coordinates in the T or P direction Note that Mechanica expresses displacement measures in units of length, not angle. To simplify discussion, Mechanica help refers to a Cartesian coordinate system. If you are working with a cylindrical or spherical coordinate system instead, make the appropriate substitutions. Measures and Output Typically, measure data is available in the summary file. However, the summary file does not include values for measures that Mechanica calculates at each step of a dynamic analysis. 511 Structural and Thermal Simulation - Help Topic Collection In addition, Mechanica provides specialized forms of measure output for the various design study types. The following table summarizes the various outputs available for each study type: Design Study Type standard design study that runs an analysis using the multi-pass convergence method Output for Measures convergence graph of a measure's value at each polynomial pass for a static, buckling, prestress, modal, or steadystate thermal analysis graph of a measure's value at each time or frequency interval for dynamic time, frequency, transient thermal, and random analyses graph of each measure's value at each load interval standard design study that runs one of the Vibration analyses or a transient thermal analysis standard design study that runs a large deformation analysis or a contact analysis optimization design study local or global sensitivity study graph of a measure's value at each step graph of a measure's value at different settings of a parameter a value for each valid measure for each analysis standard or optimization design study The types of results listed above are not available for result quantities other than measures. For other result quantities, you can query values at specific locations or view fringe, contour, and vector displays. Measures Dialog Box This dialog box appears when you select Insert>Simulation Measure. The Measures dialog box displays the following information: • • All measures you have defined for the current model Predefined measures if you select the Show Predefined Measures check box Any description you may have entered when you defined the measure • Use these buttons to work with measures: • • • New — Create a new measure. Edit — Review and edit an existing measure. Copy — Copy an existing measure. Copying measures proves handy if you want to apply the same type of measure to several different datum points. In 512 Structural and Thermal Simulation • this case, be sure to edit each copy of the measure to select the appropriate point. You can copy more than one measure at a time. To do so, simply select more than one measure from the User-Defined list and click Copy. Delete — Delete an existing measure. You can delete more than one measure at a time. To do so, simply select more than one measure from the User-Defined list and click Delete. Note that if you delete a measure that you have selected as a convergence quantity for an analysis, or as a goal or limit in an optimization design study, you should redefine the analysis or design study to ensure that it is still valid. Additionally, if you delete a measure upon which another measure depends, Mechanica deletes the dependent measure as well. For example, if you delete a measure referenced by a computed measure, Mechanica deletes both the measure you select and the computed measure. To Define Measures for Structural Analyses You define measures as a means of tracking particular Mechanica results associated with your structure model. 1. Select Insert>Simulation Measure. The Measures dialog box appears. 2. Select New. The Measure Definition dialog box appears. 3. Enter a name (optional). Do not use the same name for a measure and a design parameter. 4. Enter a description (optional). 5. Select a quantity. Depending on which quantity you select, other items appear. Click each quantity type below for other items to select to complete measure definition. For Basic and Dynamic Analyses Stress, Strain Failure Index Displacement Rotation Force Moment Computed Measure For Basic Analyses Only Fatigue Contact Center of Mass Moment of Inertia Driven Pro Parameter For Dynamic Analyses Only Velocity Acceleration Rot Velocity Rot Acceleration Phase Time 513 Structural and Thermal Simulation - Help Topic Collection To Define Measures for Thermal Analyses You define measures as a means of tracking particular Mechanica results associated with your thermal model. 1. Select Insert>Simulation Measure. The Measures dialog box appears. 2. Select New. The Measure Definition dialog box appears. 3. Enter a name. Do not use the same name for a measure and a design parameter. The description is optional. 4. Select a quantity. Depending on which quantity you select, other items appear. Click on each measure type below for a description and for other items to select to complete measure definition. • • • • • Temperature Heat Flux Temp Gradient Driven Pro Parameter Time Measures Definition Dialog Box The Measure Definition dialog box appears when you click the New or Edit buttons on the Measures dialog box. Use the Measure Definition dialog box to create or edit measures. The Measure Definition dialog box provides a top-down approach to defining your measure. Depending on whether you are running Structure or Thermal, different quantities are available for your selection at the top of the dialog box. Selecting a quantity type and making other selections at the top determines what additional options and areas become active or inactive. The dialog box lets you select only valid combinations. The Measure Definition dialog box contains the following main areas: • • Name — Enter a name for the measure. Details — Click this button to display the Description and allowables entry boxes. In the Description box, you can enter any valid information about your measure. Use the allowables boxes to specify the minimum and maximum allowables for your measure. When running an analysis or study, Mechanica outputs the allowables to the .rpt file. Quantity — Select the quantity for which you define your measure. This option menu displays only the quantities that are valid for the specific mode you are using. The quantity you select determines what other items appear on the dialog box. Valid for Analysis Types — This non editable field lists analyses for which Mechanica calculates the measure you define. Visible at Higher Level — Select this check box if you are working on the part level and want Mechanica to display and calculate the measure you are • • • 514 Structural and Thermal Simulation creating during any work you do on the assembly level. If you do not select this check box, Mechanica ignores this part level measure when you switch to the assembly. Define Measures in Structure Measures for Basic Analyses User-Defined Measures for Basic Analyses Structure provides the following basic analyses: • • • • • • static modal prestress static prestress modal buckling contact The method you use to add user-defined measures for these analyses differs slightly from the one you use for most of the dynamic analyses. The single exception is the dynamic shock analysis. You define measures for dynamic shock just as you would if you were defining a stress, strain, displacement, or rotation measure for a basic analysis. When you create user-defined measures for basic analyses, you specify a measure that does not require a time- or frequency-based calculation. In defining this type of measure, you indicate the quantity, component, and spatial evaluation method, with some exceptions. Mechanica provides several options for each of these aspects of the measure. The basic options are as follows: • • • Quantity Component Spatial Evaluation Method Depending on the quantity you select, other options may be available. For a graphical overview of measures used in basic analyses, see Basic Analyses Measure Selections. 515 Structural and Thermal Simulation - Help Topic Collection Basic Analysis Measure Selections This illustration shows the measure selections for static, modal, prestress, buckling, and contact analysis, and how they relate to each other. 1 Availability of the global spatial evaluation methods depends on the component you choose. For stress and strain quantities, Mechanica provides an additional option 516 Structural and Thermal Simulation menu that enables you to specify whether the measure will be calculated over the model or at a particular model location. 2 Available only for contact forces and center of mass. Measures for Dynamic Analyses For dynamic analyses, you want to study the model's behavior over time, at a point in time, or as a function of frequency. User-defined measures are the only measures that apply to dynamic random analyses. With dynamic time analysis, you use user-defined measures to define the quantities you want to look at through a series of time intervals, or time steps. For dynamic frequency and dynamic random analyses, you use user-defined measures to define a quantity you want to study at given frequency intervals, or frequency steps. The fourth kind of dynamic analysis, dynamic shock, is time- and frequencyindependent. The methods you use to define measures for a dynamic shock analysis are the same as those you use to define a stress, displacement, or rotation measure for a basic analysis. For more information on dynamic analyses, see: • • • • Dynamic Analysis Measure Selections Global Spatial Evaluation Methods Time/Frequency Evaluation Options Measures Not Calculated for Dynamic Random User-Defined Measures for Dynamic Analyses Structure provides the following dynamic analyses: • • • • dynamic dynamic dynamic dynamic time response frequency response random response shock User-defined measures are especially important for dynamic analyses, where you want to study the model's behavior over a time range, at a point in time, or as a function of frequency. In fact, user-defined measures are the only measures that apply to dynamic random analyses. With dynamic time analysis, you use userdefined measures to define the quantities you want to look at through a series of time intervals (or time steps), over a range of time, or at a point in time. For dynamic frequency and dynamic random analyses, you use user-defined measures to define a quantity you want to study at given frequency intervals, or frequency steps. The method you use to add user-defined measures for dynamic analyses differs slightly from the one you use for the basic analyses. The main difference is that the measures for most dynamic analyses require you to define the measure in terms of time or frequency. 517 Structural and Thermal Simulation - Help Topic Collection The exception is the measures for dynamic shock analyses, which are time- and frequency-independent. The methods you use to define measures for a dynamic shock analysis are the same as those you use to define a stress, displacement, or rotation measure for a basic analysis. Thus, to learn about dynamic shock, see Dynamic Shock Analysis. When you define a user-defined measure for dynamic analyses, you specify a measure that involves a time- or frequency-based calculation. In defining this type of measure, you indicate the quantity, component, spatial evaluation method, and time or frequency evaluation method. Mechanica provides several options for each of these aspects of the measure, as follows: • • • • • Quantity Component Spatial Evaluation Method Time or Frequency Evaluation Method Time Stamp For a graphical overview of measures used in dynamic analyses, see Dynamic Analyses Measure Selections. 518 Structural and Thermal Simulation Dynamic Analysis Measure Selections This illustration shows the dynamic measure selections and how they relate to each other. 519 Structural and Thermal Simulation - Help Topic Collection 1 Availability of the global spatial evaluation methods depends on the component you choose. For stress and strain quantities, Mechanica provides an additional option menu that enables you to specify whether the measure will be calculated over the model or at a particular location. To determine the time at which a maximum, minimum, or maximum absolute value occurs, select the Time Stamp check box. 2 3 Availability of each time/frequency evaluation method depends on the component and spatial evaluation method you choose. At Each Step is always available. Available only for the spring force or moment. 4 Measure Quantities Stress, Strain Use stress and strain measures to measure stress and strain types in your model. Specify information for the following items that appear on the Measure Definition dialog box after you select Stress or Strain as the quantity: • • • Component Spatial Evaluation Time/Frequency Eval Failure Index Use a failure index measure to determine whether a material has failed because of excessive stress levels, which might be caused by an applied load or an enforced displacement constraint. Specify information for the following items that appear on the Measure Definition dialog box after you select Failure Index as the quantity: • • Spatial Evaluation — Select a spatial evaluation method for your quantity from this option menu. Time/Frequency Eval — Activate the optional Dynamic Evaluation menu, which you use to select a time or frequency evaluation method. 520 Structural and Thermal Simulation Displacement Use a displacement measure to measure displacement for your model in terms of either magnitude or component direction. Specify information for the following items that appear on the Measure Definition dialog box after you select Displacement as the quantity: • Component — Select one of the following: o Magnitude o X o Y o Z For the options X, Y, or Z, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select an LCS or UCS. • • Spatial Evaluation — Select a spatial evaluation method for your quantity from this option menu. Time/Frequency Eval — Activate the optional Dynamic Evaluation menu, which you use to select a time or frequency evaluation method. Rotation Use a rotation measure to measure model rotations in terms of magnitude or component direction. Use this quantity for shell and beam elements only. Rotation measures are not relevant for solid elements. Specify information for the following items that appear on the Measure Definition dialog box after you select Rotation as the quantity: • Component — Select one of the following: o Magnitude o X o Y o Z For the options X, Y, or Z, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select a UCS. • • Spatial Evaluation — Select a spatial evaluation method for your quantity from this option menu. Time/Frequency Eval — Activate the optional Dynamic Evaluation menu, which you use to select a time or frequency evaluation method. 521 Structural and Thermal Simulation - Help Topic Collection Force Use a force measure to measure the spring force or the force acting on the structure through the constraints. When you select Force, the Quantity area of the Measure Definition dialog box expands displaying the following options: • • Reaction At Constraint Spring The following items also appear on the dialog box: • Component — Select one of the following: o Magnitude o X o Y o Z For the options X, Y, or Z, select a coordinate system relative to which you define the measure. If you are defining the force measure as Reaction At Constraint and you select a cylindrical or spherical coordinate system, you will also need to select a reference point. • Spatial Evaluation: o Constraint — This option appears if you selected Reaction At Constraint as a quantity. Click the arrow button to select a constraint. o Spring — This option appears if you selected Spring as a quantity. Click the arrow button to select a spring. You can only select a pointpoint or to ground spring. Time/Frequency Eval — This check box appears only if you selected Spring as a quantity. Select the check box if you want to define a dynamic evaluation method for your measure. The only available method is At Each Time Step, which directs Mechanica to calculate the value of the measure at each time or frequency step. • Moment Use a moment measure to measure the spring moment or the moment acting on the structure through the constraints. When you select Moment, the Quantity area of the Measure Definition dialog box expands displaying the following options: • • Reaction At Constraint Spring 522 Structural and Thermal Simulation The following items also appear on the dialog box: • Component — Select one of the following: o Magnitude o X o Y o Z For the options X, Y, or Z, select a coordinate system relative to which you define the measure. If you are defining the moment measure as Reaction At Constraint and you select a cylindrical or spherical coordinate system, you will also need to select a reference point. • Spatial Evaluation: o Constraint — This option appears if you selected Reaction At Constraint as a quantity. Click the arrow button to select a constraint. You also need to select point(s) for this quantity. o Spring — This option appears if you selected Spring as a quantity. Click the arrow button to select a spring. You can only select a pointpoint or to ground spring. Time/Frequency Eval — This check box appears only if you select Spring. Select the check box if you want to define a dynamic evaluation method for your measure. The only available method is At Each Time Step, which directs Mechanica to calculate the value of the measure at each time or frequency step. • Computed Measure Use a computed measure to measure values that cannot be calculated through other user-defined measures. You can define this measure as a function that references any other user-defined, noncomputed measure or measures already present in the model. After you select Computed Measure, you can enter an algebraic expression directly in the Expression entry box on the Measure Definition dialog box. You can also click the Available Function Components button to access the Symbolic Options dialog box, which you use to build your expression. The Symbolic Options dialog box contains the following: • Variables — Display all previously defined measures. Use these measures as independent variables for the function you are defining. Note that any independent variable measures you select for the expression should be of the same evaluation type. For example, if one measure is At Each Step, all other measures you select should also be At Each Step measures. Additionally, if you later delete a measure that you are using as a variable, Mechanica will also delete the computed measure without warning you. • Constants, Operators, Functions — Display various types of symbols you can use in the expression. If you are creating a computed measure for use in 523 Structural and Thermal Simulation - Help Topic Collection a dynamic analysis, you should be sure that you combine the functions in a linear fashion. If you click the independent variable in the Variables box and any symbols in their respective boxes, Mechanica places them in the Expression entry box. When creating computed measures, always be sure that the expression you create makes sense from a functional point of view. Mechanica does not check the validity of the expression you create if you, therefore, create an expression that does not make sense—von Mises stress + displacement magnitude, for example—your results for the computed measure will be meaningless. Velocity Use a velocity measure to measure velocity in terms of magnitude or component direction. Specify information for the following items that appear on the Measure Definition dialog box after you select Velocity as the quantity: • Component — Select one of the following: o Magnitude o X o Y o Z For the options X, Y, or Z, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select a UCS. • • Spatial Evaluation — Select a spatial evaluation method for your quantity from this option menu. Dynamic Evaluation — Select a time or frequency evaluation method. Acceleration Use an acceleration measure to measure acceleration in terms of magnitude or component direction. Specify information for the following items that appear on the Measure Definition dialog box after you select Acceleration as the quantity: • Component — Select one of the following: o Magnitude o X o Y o Z 524 Structural and Thermal Simulation For the options X, Y, or Z, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select a UCS. • • Spatial Evaluation — Select a spatial evaluation method for your quantity from this option menu. Dynamic Evaluation — Select a time or frequency evaluation method. Rotational Velocity Use a rotational velocity measure to measure rotational velocity in terms of magnitude or component direction. Specify information for the following items that appear on the Measure Definition dialog box after you select Rotational Velocity as the quantity: • Component — Select one of the following: o Magnitude o X o Y o Z For the options X, Y, or Z, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select a UCS. • • Spatial Evaluation — Select a spatial evaluation method for your quantity from this option menu. Dynamic Evaluation — Select a time or frequency evaluation method. Rotational Acceleration Use a rotational acceleration measure to measure rotational acceleration in terms of magnitude or component direction. Specify information for the following items that appear on the Measure Definition dialog box after you select Rotational Acceleration as the quantity: • Component — Select one of the following: o Magnitude o X o Y o Z For the options X, Y, or Z, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select a UCS. • Spatial Evaluation — Select a spatial evaluation method for your quantity from this option menu. 525 Structural and Thermal Simulation - Help Topic Collection • Dynamic Evaluation — Select a time or frequency evaluation method. Phase Use a phase measure to measure the phase for several quantities. Phase measures can be used in dynamic frequency analyses only. When you select Phase, a second option menu appears in the Quantity area of the Measure Definition dialog box. The following items also appear if you select Phase: • Component — Select one of the following: o Magnitude o X o Y o Z For the options X, Y, or Z, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select a UCS. • • Spatial Evaluation — Select a spatial evaluation method for your quantity from this option menu. Dynamic Evaluation — Select a time or frequency evaluation method. Time Use time measures to determine the time of first or last occurrence of a measure's value being greater or less than a specified value during an analysis. Specify information for the following items that appear on the Measure Definition dialog box after you select Time as the quantity: • • • • Measure Name — Use the arrow button to choose a measure from the Measures dialog box. First Occurrence or Last Occurrence Greater Than or Less Than Measure Value This measure applies to transient thermal or dynamic time analyses only. If the condition is never true, Mechanica returns a value of zero and also provides a warning in the .rpt file. 526 Structural and Thermal Simulation Fatigue Measures Use fatigue measures to specify the types of values Mechanica calculates in determining the life of your model and the level of damage. You can use fatigue measures, for example, to calculate fatigue damage at a specific point on your model. When you define fatigue measures, you must specify the following on the Measures Definition dialog box: • Component — Select one of these options: o Fatigue Life o Fatigue Damage o Safety Factor Spatial Evaluation — Select a spatial evaluation method for the quantity you are measuring. • Contact Use contact measures to measure various aspects and behaviors of contact regions during a contact analysis. This option appears only for models that contain contact regions. When you select Contact, a second option menu appears in the Quantity area of the Measure Definition dialog box. Select an option from this menu to determine the type of contact measure: • • • • • Force — calculates the stress over a single contact region Area — calculates the total area of all the selected contact regions Maximum Pressure — reports the maximum pressure over the selected contact regions Average Pressure — reports the average pressure over the selected contact regions Load — reports the contact pressure integrated over one or more contact regions The following items also appear on the dialog box: • Component — This item appears if you select Force. Select a component for Force from this option menu: o Magnitude o X o Y o Z For the options X, Y, or Z, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select a UCS. 527 Structural and Thermal Simulation - Help Topic Collection • • Contact Regions — Use the arrow to select one or more contact regions. If you are defining a force contact measure, you can only select one contact region. For all other contact measure types, you can select multiple contact regions. Surface(s) — This option appears if you selected Force. Use the arrow to select a surface for the contact force measure. Center of Mass Use Center Of Mass to measure the location of the model's center of mass in relation to the current coordinate system. When you select Center Of Mass, the Component option menu appears on the Measure Definition Dialog Box. Use the Component option menu to select a component of your quantity from this option menu: • • • • Magnitude X Y Z Note that Mechanica does not report Magnitude in the summary file for analysis. For the options X, Y, or Z, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select a UCS. Moment of Inertia Use Moment Of Inertia to measure the moment of inertia relative to either the current coordinate system or the principal inertial axes of the model. When you select Moment Of Inertia, the Quantity area of the Measure Definition dialog box expands displaying the following options: • • Center of Mass Origin 528 Structural and Thermal Simulation The Component option menu also appears when you select Moment Of Inertia. Use the Component option menu to select a component of your quantity from this option menu: • • • • • Max Principal Mid Principal Min Principal XX YY • • • • ZZ XY XZ YZ Note that Mechanica does not report Max Principal, Mid Principal, and Min Principal in the summary file for analysis. For the options XX, YY, ZZ, XY, XZ, or YZ, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select a UCS. Driven Pro Parameter Use Driven Pro Parameter to tie a measure to a Pro/ENGINEER parameter. The parameters you use for Mechanica measures must be dependent parameters. Defining parameter-based measures enables you to use Pro/ENGINEER parameters as goals or limits for optimization studies and to obtain study results for a parameter. You can use parameter-based measures to: • • • Obtain analysis and study results specific to a Pro/ENGINEER parameter — You can use parameter-based measures to obtain analysis and study results specific to a given parameter. Obtain analysis and study results for a specialized Pro/ENGINEER quantity — Pro/ENGINEER computes certain values that fall outside the realm of Mechanica. Set up optimization limits — You can use a parameter-based measure as the limit for an optimization study. You use this functionality when you want to run an optimization based on a regeneration analysis or want to define a limit not normally available through Mechanica, such as a dimensional limit. Set up parameters for use with regeneration analyses — A regeneration analysis is a predefined analysis that regenerates your Pro/ENGINEER part. Regeneration analyses do not utilize several of Mechanica's more resourceintensive functions. This type of analysis, therefore provides very rapid results. • For more information on parameter-based measures, see Example: Using ParameterBased Measures. 529 Structural and Thermal Simulation - Help Topic Collection Define Measures in Thermal User-Defined Measures for Thermal Analyses When you create user-defined measures for thermal analyses, you indicate the quantity, component, spatial evaluation method, and time evaluation method for the measure. Mechanica provides several options for each of these aspects of the measure. The options are as follows: • • • • • Quantity Component Spatial Evaluation Method Time Evaluation Method Time Stamp For a graphical overview of measures used in dynamic analyses, see Thermal Analyses Measure Selections. 530 Structural and Thermal Simulation Thermal Analysis Measure Selections This illustration shows the thermal measure selections and how they relate to each other. 1 Availability of the global spatial evaluation methods depends on the component you choose. For temperature gradient and heat flux quantities, Mechanica provides an additional option menu that enables you to specify whether the measure will be calculated over the model or at a particular model location. To determine the time at which a maximum, minimum, or maximum absolute value occurs, select the Time Stamp check box. 2 3 Availability of each time evaluation method depends on the component and spatial evaluation method you choose. At Each Step is always available. 531 Structural and Thermal Simulation - Help Topic Collection Temperature Use a temperature measure to measure temperature in your model. Specify information for the following items that appear on the Measure Definition dialog box after you select Temperature as the quantity: • • Spatial Evalulation — Select a spatial evaluation method for your quantity from this option menu. Your selection determines the type of value Mechanica calculates for your quantity. Time Eval — Activate the optional Dynamic Evaluation menu, which you use to specify a time evaluation method. If you select the Time Eval check box, Mechanica calculates the measure for transient thermal analyses. If you do not select Time Eval, Mechanica calculates the measure for steady-state thermal analyses. Heat Flux, Temperature Gradient Use heat flux or temperature gradient measures to measure heat flux or temperature gradient in terms of magnitude or component direction. Specify information for the following items that appear on the Measure Definition dialog box after you select Heat Flux or Temperature Gradient as the quantity: • Component — Select a component from this option menu. This menu contains the following items: o Magnitude o X o Y o Z For the options X, Y, or Z, select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can use the arrow button to select a UCS. • • Spatial Evaluation — Select a spatial evaluation method for your quantity from this option menu. Your selection determines the type of value Mechanica calculates for your quantity. Time Eval — Activate the optional Dynamic Evaluation menu, which you use to specify the time evaluation method. If you select Time Eval, Mechanica calculates the measure for transient thermal analyses. If you do not select Time Eval, Mechanica calculates the measure for steady-state thermal analyses. 532 Structural and Thermal Simulation Results Available for Measures Mechanica calculates results for a particular measure for certain analysis types only, and gives you the output for the following design study types: Design Study Type standard design study that runs an analysis using the multi-pass convergence method Output for Measures convergence graph of a measure's value at each polynomial pass of a static, buckling, contact, prestress, modal, or steady-state thermal analysis graph of a measure's value at each time or frequency interval for dynamic time, frequency, transient thermal, and random analyses graph of each measure's value at each load interval standard design study that runs on of the vibration analyses or a transient thermal analysis standard design study that runs a large deformation analysis or a contact analysis optimization design study graph of a measure's value at each step local or global sensitivity study graph of a measure's value at different settings of a parameter a value for each valid measure for each analysis standard or optimization design study This data is available in the summary file, which you can view online through the Run command or print through your operating system. The summary file does not include values for measures that Mechanica calculates at each step of a dynamic analysis. The types of results listed above are not available for results quantities other than measures. For other results quantities, you can query values at specific locations, view fringe, contour, and vector displays, and graph the value along element edges. Selecting One or More Measures Use the Measures dialog box to select measures for your analysis, design study, or a results window. You can also review measures from the same dialog box, but you cannot edit them. 533 Structural and Thermal Simulation - Help Topic Collection The Measures dialog box appears when you are defining the following: • Analyses — This dialog box appears if you select Measures for convergence in an analysis and then use the Measure button on the Analysis Definition dialog box. See Convergence Quantity for Static, Prestress Static, Large Deformation, and Contact Analyses for more information. Design Studies — This dialog box appears when you select a goal and limits for an optimization study. Results Window — This dialog box appears when you select Measure as the quantity when defining a result window. See Measure Results Quantity for more information. • • The two columns of the dialog box list the predefined measures relevant for the current analysis type and all user-defined measures valid for the current product. Select one or more measures or, if you are defining a result window, select one measure. Click the Review button if you want to evaluate the selected measure. After you select measures from either or both columns, click OK to close the dialog box. To Define a Failure Index Measure This procedure assumes you selected the Failure Index quantity on the Measure Definition dialog box. 1. Select a spatial evaluation. 2. With the arrow button, select a point and appropriate reference entities as required by your selection for spatial evaluation. 3. If you selected Near Point for step 1, enter a radius value. 4. If you want to define a dynamic analysis, select a time or frequency evaluation. 5. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 6. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Center of Mass Measure This procedure assumes you selected the Center of Mass quantity on the Measure Definition dialog box. 1. Select one of the following components: Magnitude, X, Y, Z. 2. For the components X, Y, and Z, select a coordinate system. 3. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 4. Click OK. Each of the custom measures shows up on the Measures dialog box. 534 Structural and Thermal Simulation To Define a Displacement Measure This procedure assumes you selected the Displacement quantity on the Measure Definition dialog box. 1. 2. 3. 4. Select one of the following components: Magnitude, X, Y, Z. For the components X, Y, and Z, select a coordinate system. Select a spatial evaluation. With the arrow button, select a point and appropriate reference entities as required by your selection for spatial evaluation. 5. If you want to define a dynamic analysis, select a time or frequency evaluation. 6. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 7. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Velocity Measure This procedure assumes you selected the Velocity quantity on the Measure Definition dialog box. 1. 2. 3. 4. 5. 6. 7. 8. Select one of the following components: Magnitude, X, Y, Z. For the components X, Y, and Z, select a coordinate system. Select a spatial evaluation. With the arrow button, select a point or appropriate reference entities as required by your selection for spatial evaluation. Select a dynamic evaluation method. If you want to know the time at which a minimum, maximum, or maximum absolute condition occurs, select the Time Stamp checkbox. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Fatigue Measure This procedure assumes you selected the Fatigue quantity on the Measure Definition dialog box. 1. Select a component option: Fatigue Life, Fatigue Damage, or Safety Factor. 2. Select a spatial evaluation method. 3. With the arrow button, select a point and appropriate reference entities as required by your selection for spatial evaluation. 4. If you selected Near Point for the location, enter a value for Radius. 5. Click OK. Each of the custom measures shows up on the Measures dialog box. 535 Structural and Thermal Simulation - Help Topic Collection To Define a Force Measure This procedure assumes you selected the Force quantity on the Measure Definition dialog box. 1. Select Reaction At Constraint or Spring. 2. Select one of the following components: Magnitude, X, Y, Z. 3. For the components X, Y, or Z, select a coordinate system. Note: For Reaction At Constraint force measures that reference a cylindrical or spherical coordinate system, you must also select a reference point. 4. If Reaction At Constraint is the quantity, select constraints. 5. If Spring is the quantity, select a spring. 6. If you want to define a dynamic analysis, check the Time/Frequency Eval check box. 7. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 8. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Moment of Inertia Measure This procedure assumes you selected the Moment Of Inertia quantity on the Measure Definition dialog box. 1. Select Center of Mass or Origin. 2. Select one of the following component values: o Max Principal o Mid Principal o Min Principal o XX o YY o ZZ o XY o XZ o YZ 3. For the components XX, YY, ZZ, XY, YZ, and XZ, select a coordinate system. 4. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 5. Click OK. Each of the custom measures shows up on the Measures dialog box. 536 Structural and Thermal Simulation To Define a Moment Measure This procedure assumes you selected the Moment quantity on the Measure Definition dialog box. 1. 2. 3. 4. 5. 6. 7. Select Reaction At Constraint or Spring. Select one of the following components: Magnitude, X, Y, Z. For the components X, Y, or Z, select a coordinate system. If Reaction At Constraint is the quantity, select constraints. If Spring is the quantity, select a spring. Select a reference point. If you want to define a dynamic analysis, check the Time/Frequency Eval check box. 8. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 9. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Rotation Measure This procedure assumes you selected the Rotation quantity on the Measure Definition dialog box. 1. 2. 3. 4. Select one of the following components: Magnitude, X, Y, Z. For the components X, Y, and Z, select a coordinate system. Select a spatial evaluation. With the arrow button, select a point or appropriate reference entities as required by your selection for spatial evaluation. 5. If you want to define a dynamic analysis, select a time or frequency evaluation. 6. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 7. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Contact Measure This procedure assumes you selected the Contact quantity on the Measure Definition dialog box. 1. Select a contact measure type from the second option menu. 2. If you selected Force in step 1, select one of the following components: Magnitude, X, Y, Z. 3. For the components X, Y, and Z, select a coordinate system. 4. Select one or more contact regions. 5. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 6. Click OK. Each of the custom measures shows up on the Measures dialog box. 537 Structural and Thermal Simulation - Help Topic Collection To Define a Driven Pro Parameter Measure This procedure assumes you selected the Driven Pro Parameter quantity on the Measure Definition dialog box and have already created a Pro/ENGINEER parameter. Perform these steps to tie a measure to a dependent pro parameter. 1. Click the arrow button. The Select Pro/ENGINEER Parameter dialog box appears. 2. Select a parameter from the list. Be sure the parameter meets the following criteria: o o The parameter value can vary. The parameter is not currently being used as a Mechanica design parameter. Mechanica does not check Pro/ENGINEER parameters to determine which ones are dependent. Rather, the software displays all Pro/ENGINEER parameters defined as relations or defined with Real Number as the Type. 3. Click Accept to close the Select Pro/ENGINEER Parameter dialog box. Mechanica returns you to the Measure Definition dialog box. Mechanica changes the measure name so that it is identical to the Pro/ENGINEER parameter name. 4. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 5. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Heat Flux or Temperature Gradient Measure This procedure assumes you selected the Temperature Gradient or Heat Flux quantity on the Measure Definition dialog box. 1. 2. 3. 4. Select one of the following components: Magnitude, X, Y, Z. For the components X, Y, and Z, select a coordinate system. Select a spatial evaluation. With the arrow button, select a point and appropriate reference entities as required by your selection for spatial evaluation. 5. Enter a radius value if you selected Near Point in step 3. 6. If you want to define a transient thermal analysis, select the Time Eval check box and specify a time evaluation method. 7. If you want to know the time at which a minimum, maximum, or max abs condition occurs, select the Time Stamp checkbox. 538 Structural and Thermal Simulation 8. Review the list box at the bottom of the dialog box to determine which type of analysis is valid for the measure. 9. Click OK. Each custom measure shows up on the Measures dialog box. To Define a Phase Measure This procedure assumes you selected the Phase quantity on the Measure Definition dialog box. 1. 2. 3. 4. 5. 6. 7. 8. 9. Select an item from the second option menu to complete the phase type. Select one of the following components: Magnitude, X, Y, Z. For the components X, Y, and Z, select a coordinate system. Select a spatial evaluation. With the arrow button, select a point or appropriate reference entities as required by your selection for spatial evaluation. Select a dynamic evaluation method. If you want to know the time at which a minimum, maximum, or maximum absolute condition occurs, select the Time Stamp checkbox. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Rotational Acceleration Measure This procedure assumes you selected the Rotational Acceleration quantity on the Measure Definition dialog box. 1. 2. 3. 4. Select one of the following components: Magnitude, X, Y, Z. For the components X, Y, and Z, select a coordinate system. Select a spatial evaluation. With the arrow button, select a point or appropriate reference entities as required by your selection for spatial evaluation. 5. If you want to know the time at which a minimum, maximum, or maximum absolute condition occurs, select the Time Stamp checkbox. 6. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 7. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Rotational Velocity Measure This procedure assumes you selected the Rotational Velocity quantity on the Measure Definition dialog box. 1. 2. 3. 4. Select one of the following components: Magnitude, X, Y, Z. For the components X, Y, and Z, select a coordinate system. Select a spatial evaluation. With the arrow button, select a point or appropriate reference entities as required by your selection for spatial evaluation. 539 Structural and Thermal Simulation - Help Topic Collection 5. Select a dynamic evaluation method. 6. If you want to know the time at which a minimum, maximum, or maximum absolute condition occurs, select the Time Stamp checkbox. 7. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 8. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Temperature Measure This procedure assumes you selected the Temperature quantity on the Measure Definition dialog box. 1. Select a spatial evaluation. 2. With the arrow button, select a point or appropriate reference entities as required by your selection for spatial evaluation. 3. If you want to define a transient thermal analysis, select the Time Eval check box and specify a time evaluation method. 4. If you want to know the time at which a minimum, maximum, or maximum absolute condition occurs, select the Time Stamp checkbox. 5. Review the list box at the bottom of the dialog box to determine which type of analysis is valid for the measure. 6. Click OK. Each custom measure shows up on the Measures dialog box. To Define a Time Measure This procedure assumes you selected the Time quantity on the Measure Definition dialog box. 1. 2. 3. 4. 5. Click the arrow button to select a measure from the Measures dialog box. Select First Occurrence or Last Occurrence. Select Greater Than or Less Than. Enter a value for the measure in the text box. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 6. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define a Stress or Strain Measure This procedure assumes you selected the Stress or Strain quantity on the Measure Definition dialog box. 1. 2. 3. 4. Select a component. For the components XX, YY, ZZ, XY, YZ, and XZ, select a coordinate system. Select a spatial evaluation. With the arrow button, select points and appropriate reference entities as required by your selection for spatial evaluation. 5. If you selected Near Point for spatial evaluation, enter a radius value. 540 Structural and Thermal Simulation 6. If you want to define a dynamic analysis, select a time or frequency evaluation. 7. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. 8. Click OK. Each of the custom measures shows up on the Measures dialog box. To Define an Acceleration Measure This procedure assumes you selected the Acceleration quantity on the Measure Definition dialog box. 1. 2. 3. 4. 5. 6. 7. 8. Select one of the following components: Magnitude, X, Y, Z. For the components X, Y, and Z, select a coordinate system. Select a spatial evaluation. With the arrow button, select a point or appropriate reference entities as required by your selection for spatial evaluation. Select a dynamic evaluation method. If you want to know the time at which a minimum, maximum, or maximum absolute condition occurs, select the Time Stamp checkbox. Review the list box at the bottom of the dialog box to determine which types of analyses are valid for the measure. Click OK. Each of the custom measures shows up on the Measures dialog box. Time/Frequency Eval Activate the optional Dynamic Evaluation menu, which you use to select a time or frequency evaluation method. If you select the Time/Frequency Eval check box, Mechanica calculates the measure for dynamic time and dynamic frequency analyses. Mechanica also calculates the measure for dynamic random analyses provided you base the measure on a directional component and take the measure at a point. Note that if you select Failure Index as the quantity, Mechanica calculates the measure for dynamic time analyses only. For most quantities, if you do not select Time/Frequency Eval, Mechanica calculates the measure for dynamic shock, static, prestress static, and contact analyses. RMS Mechanica calculates the RMS (root mean square) value of the measure over the frequency range. This option is available for certain quantities if you selected At Point for Spatial Evaluation and base the measure on one of the directional components. Mechanica 541 Structural and Thermal Simulation - Help Topic Collection only calculates measures that use the RMS dynamic evaluation method for dynamic random analyses. Maximum For a dynamic time, frequency, or random response analysis, Mechanica calculates the maximum value over: • • • all the time steps of the analysis all the frequency steps of the analysis a specified time range If you select the Time Stamp check box, Mechanica creates a time stamp measure that saves the time at which a maximum condition occurs. Mechanica reports this value in the summary file. This option is not available if the Spatial Evaluation method is Minimum or Max Abs. Max Absolute For a dynamic time, frequency, or random response analysis, Mechanica calculates the maximum magnitude value over: • • • all the time steps of the analysis all the frequency steps of the analysis a specified time range If you select the Time Stamp check box, Mechanica creates a time stamp measure that saves the time at which a maximum absolute condition occurs. Mechanica reports this value in the summary file. This option is not available if the Spatial Evaluation method is Maximum or Minimum, or if the Component is Magnitude, von Mises, Max Principal, or Min Principal. Minimum For a dynamic time, frequency, or random response analysis, Mechanica calculates the minimum value over: • • • all the time steps of the analysis all the frequency steps of the analysis a specified time range 542 Structural and Thermal Simulation If you select the Time Stamp check box, Mechanica creates a time stamp measure that saves the time at which a minimum condition occurs. Mechanica reports this value in the summary file. This option is not available if the Spatial Evaluation method is Maximum or Max Abs. Example: Near Point Measures and Model Types For near point measures, Mechanica creates a three-dimensional sphere about the application point you select. Depending on the type of model you are working with and its contours near the application point, Mechanica develops an application area that may be one-, two-, or three-dimensional, as shown below: Component — Dynamic Analyses In defining a measure component, you specify the nature of or references for the quantity you want to measure. The components that you can select depend on the quantity you choose, as follows: • For stress and strain quantities — If you choose Stress or Strain as the measure quantity, you can select from a variety of components. These components fall into three categories—derived, normal/shear, and beam. 543 Structural and Thermal Simulation - Help Topic Collection Mechanica provides the following derived stresses and strains: von Mises, Tresca, maximum principal, minimum principal, and maximum absolute principal. Note that for dynamic random response analyses, Mechanica does not calculate stress or strain measures with von Mises, Max Shear (Tresca), Max Principal, Min Principal, or Max Abs Principal as components. For normal/shear stresses and strains, Mechanica provides the three normal stress/ strain directions as well as the three shear stress/strain directions. These directions are relative to the current coordinate system. Mechanica provides the following beam measures: beam bending, beam tensile, beam torsion, and beam total. Beam total is a combined measure that reports both beam bending and beam tensile stress/strain. • For all other valid quantities — If you choose any of the other quantities valid for dynamic analyses—except for Time—you can select either a magnitude component or one of the X, Y, Z component directions. For magnitude, Mechanica calculates the measure using all three component directions. For component directions, calculations are axis-specific relative to the current coordinate system. For dynamic random response analyses, Mechanica does not calculate measures with a Magnitude component. Component — Thermal Analyses In defining a measure component, you specify the nature of or references for the quantity you want to measure. For heat flux and temperature gradient quantities, you can select either magnitude or one of the X, Y, Z component directions. For magnitude, Mechanica calculates the measure using all three component directions. For component directions, calculations are axis-specific relative to the current coordinate system. If you select temperature as a quantity, Mechanica does not provide any component options. At Each Step — Time or Frequency Evaluation Method Mechanica calculates the value of the measure at each time step or frequency step. The software does not report the measure values in the summary file, but you can plot these measures as a function of time or frequency when you create your analysis results. 544 Structural and Thermal Simulation Minimum — Time or Frequency Evaluation Method Mechanica calculates the measure using one of several methods, depending on whether you selected At Point or Minimum as the spatial evaluation method and which time span you selected from the Dynamic Evaluation option menu. If you selected At Point as the spatial evaluation method, Mechanica calculates the quantity minimum at a selected point over all the time or frequency steps. Depending on which time span you select from the Dynamic Evaluation option menu, Mechanica calculates the quantity minimum over the entire analysis or over a specified time range. If you selected Minimum as the spatial evaluation method, Mechanica calculates the quantity minimum over the model at each step. The software then compares these values and reports the lowest value it finds among the steps. Depending on which time span you select, Mechanica calculates the minimum over the entire analysis or over a specified time range. You can find the measure value in the summary file. If you select a spatial evaluation of Maximum or Max Abs, this option is not available. Quantity — Basic Analyses In defining the quantity of the measure, you indicate the type of information you want Mechanica to measure. Although Mechanica provides a substantial number of quantities for you to choose from, you should limit your selection to the following quantities for basic analysis: • • • • • • • • • • Stress — enables you to measure a variety of stress types in your model. Strain — enables you to measure a variety of strain types in your model. Failure Index — enables you to determine whether a material has failed because of an applied load. Displacement — enables you to measure displacement for your model in terms of either magnitude or component direction. Rotation — enables you to measure model rotation either in terms of magnitude or component direction. Use this quantity for shell and beam models only. Rotation measures are not relevant for solid models. Force — enables you to measure the spring force or force reactions at a constrained surface or curve. Moment — enables you to measure the spring moment or moment reactions at a constrained surface or curve. Contact — enables you to measure various aspects of the contact regions during a contact analysis, such as contact area, maximum pressure, average pressure, contact load, and contact force. Center of Mass — enables you to measure the location of the model's center of mass in relation to the current coordinate system. Moment of Inertia — enables you to measure the moment of inertia relative to either the current coordinate system or the principal inertial axes of the model. 545 Structural and Thermal Simulation - Help Topic Collection • • Driven Pro Parameter — enables you to tie a measure to a dependent Pro/ENGINEER parameter. For information on this quantity, see ParameterBased Measures. Computed Measure — enables you to define your own algebraic expression for the measure. For basic analyses, do not select velocity, acceleration, rotational velocity, rotational acceleration, phase, or time. These quantities apply to dynamic analyses only. At Each Step Mechanica calculates the value of the measure at each time step for a dynamic time response analysis or at each frequency step for a dynamic frequency or random response analysis. If you selected At Each Step as the time or frequency evaluation method, you can obtain a cumulative measure value for all steps by selecting the Cumulative check box. Mechanica does not report the measure values in the summary file, but you can plot these values as a function of time or frequency through the Results command. Example: Near Point Measures and Geometric Intersection For near point measures, be aware that Mechanica samples only the geometric area immediately surrounding the application point. If there is geometry that intersects the near point measure radius but is separated from the application point by air space, Mechanica does not sample the separated geometry, as shown below: 546 Structural and Thermal Simulation Maximum — Time or Frequency Evaluation Method Mechanica calculates the measure using one of several methods, depending on whether you selected At Point or Maximum as the spatial evaluation method and which time span you selected from the Dynamic Evaluation option menu. If you selected At Point as the spatial evaluation method, Mechanica calculates the quantity maximum at a selected point over all the time or frequency steps. Depending on which time span you select from the Dynamic Evaluation option menu, Mechanica calculates the quantity maximum over the entire analysis or over a specified time range. If you selected Maximum as the spatial evaluation method, Mechanica calculates the quantity maximum over the model at each step. The software then compares these values and reports the highest value it finds among the steps. Depending on which time span you select, Mechanica calculates the quantity maximum over the entire analysis or over a specified time range. You can find the measure value in the summary file. If you select a spatial evaluation of Minimum or Max Abs, this option is not available. Component — Stress and Strain Quantities If you choose Stress or Strain as the measure quantity, you can select from a variety of components. These components fall into three categories—derived, normal/shear, and beam. Mechanica provides the following derived stresses and strains: von Mises, max shear (Tresca), maximum principal, minimum principal, and maximum absolute principal. For normal/shear stresses and strains, Mechanica provides the three normal stress / strain directions as well as the three shear stress or strain directions. These directions are relative to the current coordinate system. Mechanica provides the following beam measures: beam bending, beam tensile, beam torsion, and beam total. Beam total is a combined measure that reports both beam bending and beam tensile stress or strain. Component — Basic Analyses In defining a measure component, you specify the nature of, or references for, the quantity you want to measure. The components you can select depend on the quantity you choose, as follows: • • • stress and strain quantities displacement, rotation, and reaction quantities the contact force quantity 547 Structural and Thermal Simulation - Help Topic Collection • • center of mass quantities moment of inertia quantities Global Spatial Evaluation Methods In working with the global spatial evaluation methods, consider the following points: • Because Mechanica must recover data for each plotting grid point at every time step or frequency step, choosing any of the global spatial evaluation methods may result in a time-consuming dynamic analysis run. For example, if you select Maximum for a displacement measure in a dynamic time analysis, Mechanica calculates the maximum displacement at every plotting grid point. The software repeats this process for each time step. However, bear in mind that once you define a global measure using one type of spatial evaluation, Mechanica requires an insignificant amount of additional time to calculate a different measure that uses the same type of spatial evaluation. In other words, if you specified Maximum as a spatial evaluation method for a von Mises stress measure as well as a maximum principal stress measure, there would be no appreciable time difference between running a dynamic analysis that used only one of the measures and running an analysis that used both measures. • If you select stress or strain as the quantity, Mechanica provides you with an additional option menu that enables you to determine whether the software considers the entire model or samples various points within a specified radius of a model location. The latter type of measure is called a Near Point measure. For more information on Near Point measures, see Global and Local Measures. Measures Not Calculated for Dynamic Random For dynamic random response analyses, Mechanica does not calculate the following types of measures: • • • Failure index Stress measures with the components von Mises, Tresca, Max Principal, Min Principal, or Max Abs Principal Other measures with the component Magnitude Datum Points for User-Defined Measures If you plan to place a measure at a specific point on an exterior surface, your part needs to include a datum point at that location unless the location is a vertex. Provided you are working with an assembly, you can place measures on the interior 548 Structural and Thermal Simulation of your model by adding a datum point to a part surface that will merge with a mated part during a run. Note that for reaction measures, you can use datum points that do not lie on the part geometry. These points can lie buried within the part or lie outside the part. You can add datum points within Mechanica as you define your measures. These datum points are: • • only available for your Mechanica sessions unless you promote them not visible on your part or assembly while you are working at the Pro/ENGINEER level unless you promote them As an alternative, you can add datum points to your model in Pro/ENGINEER before entering Mechanica. In this case, the datum points are available for all your Pro/ENGINEER sessions as well. Time/Frequency Eval Options When you click the Time/Frequency Eval button, you can specify the time or frequency for your measure from the following choices: At Each Step Provides the value of the measure at each time or frequency step of the analysis. You can create a graph for this type of measure against time or frequency. Provides the maximum, minimum, or maximum magnitude value over all time or frequency steps, or over a specified time range for a dynamic time analysis. Also, Mechanica can create a measure that saves the time at which a maximum, minimum, or maximum absolute condition occurs. You can find this value in the summary report. Provides the RMS value or apparent frequency of a quantity. You can find this value in the summary report. Provides the value of a measure at a time you specify. Maximum, Minimum, Maximum Abs RMS, Apparent Frequency At Time The selection you make on the Time/Frequency Eval option menu determines in what type of analysis you can use the measure. 549 Structural and Thermal Simulation - Help Topic Collection Analysis Type dynamic time response Time/Freq Eval Option At Each Step Maximum, Minimum At Time dynamic frequency response At Each Step Maximum, Minimum dynamic random response At Each Step RMS Apparent Frequency Component — Center of Mass Quantities If you choose Center Of Mass as the measure quantity, your selections are the same as those for rotations and displacements. However, the software calculates the measure in terms of overall distance or distance in a particular coordinate direction. For magnitude, Mechanica calculates the distance from the current coordinate system to the center of mass. If you select one of the coordinate directions instead, Mechanica calculates the distance from the origin of the current coordinate system to the center of mass for the selected direction only. For example, if you select X as the component, the software calculates the distance between the coordinate system and center of mass in the X direction. Component — Stress, Strain When you select Stress or Strain from the Quantity option menu, the Component option menu displays the components specific to these quantities. Select a component of stress or strain from the options on this menu. • von Mises • XY* • Max Shear • XZ* 550 Structural and Thermal Simulation • Max Principal • YZ* • Min Principal • Beam Bending • Max Abs Principal • Beam Tensile • XX* • Beam Total • YY* • Beam Torsional • ZZ* *If you select any of these options, use the arrow button to select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can also select a UCS. Note: Mechanica derives von Mises strain in the same way as von Mises stress, and maximum shear strain in the same way as maximum shear stress. For more information, see option information for Strain Results Quantity or Stress Results Quantity. Structure expresses stress values and directions somewhat differently than they are sometimes described in textbooks. To learn more about how Structure stresses relate to textbook examples, see How Stress Components Relate to Textbook Examples. Quantity — Dynamic Analyses In defining the quantity of the measure, you indicate the type of information you want Mechanica to measure. Although Mechanica provides a full list of quantities for you to choose from, you should limit your selection to the following quantities for dynamic analyses: • • • • • • • Stress — enables you to measure a variety of stress types in your model. Strain — enables you to measure a variety of strain types in your model. Displacement — enables you to measure displacement for your model in terms of magnitude or component direction. Failure Index — enables you to determine whether a material has failed because of an applied load. Force — enables you to measure the spring force. Moment — enables you to measure the spring moment. Velocity — enables you to measure velocity in terms of magnitude or component direction. 551 Structural and Thermal Simulation - Help Topic Collection • • • • • • • • Acceleration — enables you to measure acceleration in terms of magnitude or component direction. Rotation — enables you to measure model rotation in terms of magnitude or component direction. Rotational Velocity — enables you to measure rotational velocity in terms of magnitude or component direction. Rotational Acceleration — enables you to measure rotational acceleration in terms of magnitude or component direction. Phase — enables you to measure the phase for any of the following quantities: displacement, velocity, acceleration, rotation, rotational velocity, or rotational acceleration. Only dynamic frequency analyses calculate phase measures. Driven Pro Parameter — enables you to tie a measure to a dependent Pro/ENGINEER parameter. For information on this quantity, see ParameterBased Measures. Time — enables you to determine the time of first or last occurrence of a measure's value being greater or less than a specified value during a dynamic time analysis. Computed Measure — enables you to define your own algebraic expression for the measure. For dynamic analyses, do not select Reaction, Center of Mass, or Moment of Inertia. These quantities apply to basic analyses only. For information on how to use these quantities in basic analyses, see Quantity — Basic Analyses. Quantity — Thermal Analyses In defining the quantity of the measure, you indicate the type of information you want Mechanica to measure, as follows: • • • • • • Temperature — enables you to measure the temperature of your model. Heat Flux — enables you to measure the transfer of heat for your model in terms of either magnitude or component direction. Temperature Gradient — enables you to measure the change in temperature over your model in terms of either magnitude or component direction. Driven Pro Parameter — enables you to tie a measure to a dependent Pro/ENGINEER parameter. For information on this quantity,see ParameterBased Measures. Time — enables you to determine the time of first or last occurrence of a measure's value being greater or less than a specified value during a dynamic time analysis. Computed Measure — enables you to define your own algebraic expression for the measure. Spatial Evaluation Method — Basic and Dynamic Analyses In defining a spatial evaluation method, you specify the type of value you want Mechanica to calculate for the measure, and indicate whether you want a global or a 552 Structural and Thermal Simulation local measure. For most quantities you select, Mechanica provides two option menus for spatial evaluation. The first menu enables you to select a spatial evaluation method. The second determines whether the software considers the entire model or selected areas of the model, or samples various points within a specified radius. You can select from the following spatial evaluation methods, depending on which measure component you choose: • At Point — Mechanica treats the measure as a local measure, calculating the value at a datum point or points you select. If you click the Advanced button and select an option from the second menu, Mechanica calculates the value over a selected group of entities touching the point. Maximum — Depending on your selection in the second menu, Mechanica can treat the measure as a global or as a local measure, searching the entire model or its selected area for the quantity's maximum value. This value is the most positive value, regardless of the magnitude of the value. For example, if the model stress ranged from –10 to –25 ksi, the maximum would be –10 ksi. This option is inactive if you select Min Principal or Max Abs Principal for a Stress or Strain quantity. • Minimum — Depending on your selection in the second menu, Mechanica can treat the measure as a global or local measure, searching the entire model or its selected area for the quantity's minimum value. This value is the least positive value, regardless of the magnitude of the value. This option is inactive if you select Max Principal or Max Abs Principal for a Stress or Strain quantity. • Maximum Abs — Depending on your selection in the second menu, Mechanica can treat the measure as a global or local measure, searching the entire model or its selected area for the quantity's maximum absolute value. This value is the largest value, regardless of the sign of the value. For example, if the model stress ranged from –10 to –25 ksi, the value would be –25 ksi. This option is inactive if you select Max Principal or Min Principal as the component for a Stress or Strain quantity. This option is also inactive if you select Magnitude as the component for one of the other quantities. • Spatial Evaluation Method — Thermal Analyses In defining a spatial evaluation method, you specify the type of value you want Mechanica to calculate for the measure, and indicate whether you want a global or a local measure. If you select Temperature, Temperature Gradient, or Heat Flux quantities, Mechanica provides you with two option menus for spatial evaluation. The first menu enables you to select a spatial evaluation method. The second, determines whether the software considers the entire model or selected areas of the model, or samples various points within a specified radius. 553 Structural and Thermal Simulation - Help Topic Collection You can select from the following spatial evaluation methods, depending on which measure component you choose: • At Point — Mechanica treats the measure as a local measure, calculating the value at a datum point or points you select. If you click the Advanced button and select an option from the second menu, Mechanica calculates the value over a selected group of entities touching the point. If you use this spatial evaluation method for heat flux or temperature gradient, you may want to define a measure for more than one point so that you can get a better idea of overall heat transfer and temperature change. • Maximum — Mechanica searches the entire model or the specified area of the model for the quantity's maximum value. This value is the most positive value, regardless of the magnitude of the value. For example, if the model temperature ranged from –10 to –25 , the maximum would be –10 . Minimum — Mechanica searches the entire model or the specified area of the model for the quantity's minimum value. This value is the least positive value, regardless of the magnitude of the value. Maximum Abs — Mechanica searches the entire model or the specified area of the model for the quantity's maximum absolute value. This value is the largest value, regardless of the sign of the value. For example, if the model temperature ranged from –10 to –25 , the maximum absolute value would be –25 . This option appears only if you select Temperature as the quantity. Range — Mechanica calculates the difference between the maximum and the minimum temperatures in the model or the specified area of the model. This option appears only if you select Temperature as the quantity. • • • Time or Frequency Evaluation Method — Dynamic Analyses In defining the time or frequency evaluation method, you indicate the way you want Mechanica to treat the measure as calculated at various time steps or frequency steps. For example, you can use one of the time or frequency evaluation methods to instruct Mechanica to report the maximum value encountered among the steps as a whole. If, instead, you wanted to review the maximum value for each step individually, you could select a different time or frequency evaluation method. You can select from the following time or frequency evaluation methods, depending on which measure component and spatial evaluation method you choose: • • • • • At Each Step Maximum Minimum Maximum Absolute RMS — Mechanica calculates the RMS (root mean square) value of the measure over the frequency range and reports this value in the summary file. 554 Structural and Thermal Simulation • This option is only available if you selected At Point as the spatial evaluation method. Apparent Frequency — Mechanica determines the effective frequency of a PSD output by integrating over the frequency range and reports this value in the summary file. Mechanica calculates apparent frequency by averaging the number of zerocrossings for the PSD output. The apparent frequency is equivalent to the frequency of a sine wave that crosses zero the same number of times. This option is only available if you select At Point as the spatial evaluation method. • At Time — Mechanica calculates the value of a measure at a time you specify. The measure is calculated for dynamic time analyses. Component — Moment of Inertia Quantities If you choose Moment Of Inertia as the measure quantity, you can select from a variety of components. These components fall into two categories—part-based component directions and coordinate-system-based component directions. Mechanica provides the following part-based component directions: maximum principal, mid principal, and minimum principal. These component directions are relative to the principal inertial axes of the model. Specify Max Principal to define the measure relative to the direction with the greatest inertia. Use Min Principal to define the measure relative to the axis of least inertia. The orientation of the principal inertial axes of your part lies where all products of inertia are zero simultaneously. If you select one of the component directions instead, Mechanica determines the moment of inertia relative to the current coordinate system in the direction you selected. Component — Displacement, Rotation, and Reaction Quantities If you choose Displacement, Rotation, or Reaction as the measure quantity, you can select either the magnitude or one of the X, Y, Z component directions. For magnitude, Mechanica calculates the measure using all three component directions. For component directions, calculations are axis-specific relative to the current coordinate system. 555 Structural and Thermal Simulation - Help Topic Collection Apparent Frequency Mechanica calculates the effective frequency of a PSD output by integrating over the frequency range. This option is available for certain quantities if you selected At Point for Spatial Evaluation and base the measure on one of the directional components. Mechanica only calculates measures that use the Apparent Frequency dynamic evaluation method for dynamic random analyses. Component — Contact Force Quantity If you choose Contact Force as the measure quantity, you can select either the magnitude or one of the X, Y, Z component directions. To create a contact force measure, select a contact region, then select one of the two surfaces (or curves in 2D). The contact forces on the two surfaces (or curves in 2D) of a contact region are equal in magnitude but opposite in direction to each other. This measure can be associated with only one contact region. For pre-Release 2000i models, a contact load measure will be converted into a contact force magnitude measure if it is associated with a single contact region. If a pre-Release 2000i contact load measure is associated with multiple contact regions, the measure will be deleted after a warning message appears. Time Evaluation Method — Thermal Analyses In defining the time evaluation method, you indicate the way you want Mechanica to treat the measure as calculated at various time steps. For example, you can use one of the time evaluation methods to instruct Mechanica to report the maximum value encountered among the steps as a whole. If, instead, you wanted to review the maximum value for each step individually, you could select a different time evaluation method. You can select from the following time evaluation methods, depending on which measure component and spatial evaluation method you choose: • • • • • At Each Step Maximum Minimum Maximum Absolute At Time — Mechanica calculates the value of a measure at a time you specify. The measure is calculated for transient thermal analyses. 556 Structural and Thermal Simulation Maximum Absolute — Time Evaluation (Thermal Analysis) Mechanica calculates the measure using one of several methods, depending on whether you selected At Point or Maximum Abs as the spatial evaluation method. If you selected At Point as the spatial evaluation method, Mechanica calculates the maximum absolute value at the selected point over all the time steps. Depending on which time span you select from the ancillary menu, Mechanica calculates the maximum quantity absolute value over the entire analysis or over a specified time range. If you selected Maximum Abs as the spatial evaluation method, Mechanica calculates the quantity maximum absolute value over the model at each step. The software then compares these values and reports the largest magnitude it finds among the steps. Depending on which time span you select from the ancillary menu, Mechanica calculates the quantity maximum absolute value over the entire analysis or over a specified time range. You can find the measure value in the summary file. If you select a spatial evaluation of Maximum or Minimum, this option is not available. Also, this option is not available if you select Magnitude as a measure component. Minimum — Time Evaluation (Thermal Analysis) Mechanica calculates the measure using one of several methods, depending on whether you selected At Point or Minimum as the spatial evaluation method. If you selected At Point as the spatial evaluation method, Mechanica calculates the quantity minimum at the selected point over all the time steps. Depending on which time span you select from the ancillary menu, Mechanica calculates the quantity minimum over the entire analysis or over a specified time range. If you selected Minimum as the spatial evaluation method, Mechanica calculates the quantity minimum over the model at each step. The software then compares these values and reports the lowest value it finds among the steps. Depending on which time span you select from the ancillary menu, Mechanica calculates the quantity minimum over the entire analysis or over a specified time range. You can find the measure value in the summary file. If you select a spatial evaluation of Maximum or Maximum Abs, this option is not available. 557 Structural and Thermal Simulation - Help Topic Collection Maximum Absolute — Time or Frequency Evaluation Method Mechanica calculates the measure using one of several methods, depending on whether you select At Point or Maximum Abs as the spatial evaluation method and which time span you selected from the Dynamic Evaluation option menu. If you selected At Point as the spatial evaluation method, Mechanica calculates the maximum absolute value at a selected point over all the time or frequency steps. Depending on which time span you select from the Dynamic Evaluation option menu, Mechanica calculates the maximum absolute value over the entire analysis or over a specified time range. If you selected Maximum Abs as the spatial evaluation method, Mechanica calculates the maximum absolute value over the model at each step. The software then compares these values and reports the largest magnitude it finds among the steps. Depending on which time span you select, Mechanica calculates the largest magnitude over the entire analysis or over a specified time range. You can find the measure value in the summary file. If you select a spatial evaluation of Maximum or Minimum, this option is not available. Also, this option is not available if you select Magnitude or Von Mises as a measure component. Maximum — Time Evaluation (Thermal Analysis) Mechanica calculates the measure using one of several methods, depending on whether you selected At Point or Maximum as the spatial evaluation method. If you selected At Point as the spatial evaluation method, Mechanica calculates the quantity maximum at the selected point over all the time steps. Depending on which time span you select from the ancillary menu, Mechanica calculates the maximum over the entire analysis or over a specified time range. If you selected Maximum as the spatial evaluation method, Mechanica calculates the quantity maximum over the model at each step. The software then compares these values and reports the highest value it finds among the steps. Depending on which time span you select from the ancillary menu, Mechanica calculates the maximum over the entire analysis or over a specified time range. You can find the measure value in the summary file. If you select a spatial evaluation of Minimum or Maximum Abs, this option is not available. 558 Structural and Thermal Simulation At Each Step — Time Evaluation (Thermal Analysis) Mechanica calculates the value of the measure at each time step. The time step may vary by many orders of magnitude during the course of an analysis, depending on the loads and constraints. At the beginning of an analysis, the time step can be especially small. As the energy norm in the model is zero at the start of an analysis, the errors in energy norm are normalized by a small value. The software does not report the measure values in the summary file, but you can plot these measures as a function of time when you create your analysis results. Radius When you choose Near Point, Mechanica displays an entry box showing a default value of 5% of the model size. Use this entry box to type in another radius value if desired. The radius you specify is three-dimensional rather than planar. Thus, the portion of the model considered depends on the model's contours. For more information, see Near Point Measures. You use the Point(s) selector arrow to select the application area for the measure. Spatial Evaluation — Thermal Select a spatial evaluation method from this option menu on the Measure Definition dialog box. The menu displays only those options that are valid for the quantity and component combination you selected and does not appear for all combinations. After you select the spatial evaluation type from the first option menu, you may see additional option menus or buttons. Some of the spatial evaluation options require that you select a point or several points and appropriate reference entities. You can select them using the arrow button. Your selection from the following menu determines the type of value Mechanica calculates: • • • • • At Point — Mechanica calculates the value at the point or points you select. Maximum — Mechanica calculates the maximum value. Minimum — Mechanica calculates the minimum value. Maximum Abs — Mechanica calculates the value with the greatest absolute value. This option is not available if you selected Magnitude as the component for your quantity. Range — Mechanica calculates the temperature range. This option is only available if you selected Temperature as the quantity. For the options Maximum, Minimum, and Maximum Abs, a second option menu appears. For the At Point option, this menu appears as an advanced option only if you selected Temperature Gradient or Heat Flux as your quantity. 559 Structural and Thermal Simulation - Help Topic Collection The menu contains the following items: • • Over Model — Specifies that Mechanica evaluates the quantity's maximum, minimum, or maximum absolute value over the entire model. Near Point — Specifies that Mechanica evaluates the quantity's maximum, minimum, or maximum absolute value over the plotting grid points you select within the specified radius. This option is not available if you selected At Point. Over Selected Idealizations — Specifies that Mechanica evaluates the quantity's maximum, minimum, maximum absolute, or at point value over the idealizations you select. Over Selected Components — Specifies that Mechanica evaluates the quantity's maximum, minimum, maximum absolute, or at point value over the assembly's component you select. Over Selected Layers — Specifies that Mechanica evaluates the quantity's maximum, minimum, maximum absolute, or at point value over the layers you select. Over Selected Geometry — Specifies that Mechanica evaluates the quantity's maximum, minimum, maximum absolute, or at point value over the geometric entities you select. • • • • Dynamic Evaluation in Thermal This drop-down menu appears when you click the Time Eval check box on the Measure Definition dialog box. Use this menu to select a time evaluation method. The menu contains all or some of the following items: • At Each Step — Mechanica calculates the value of the measure at each time step for a transient thermal analysis. Mechanica does not report the measure values in the summary file, but you can plot these measures as a function of time through the Results command. Maximum — Mechanica calculates the maximum value for a transient thermal analysis. This option is not active if the Spatial Evaluation method is Minimum or Maximum Abs. Mechanica reports this value in the summary file. Minimum — Mechanica calculates the minimum value for a transient thermal analysis. This option is not active if the Spatial Evaluation method is Maximum or Maximum Abs. Mechanica reports this value in the summary file. Maximum Abs — Mechanica calculates the maximum absolute value for a transient thermal analysis. This option is not active if the Spatial Evaluation method is Maximum or Minimum, or if the Component is Magnitude. Mechanica reports this value in the summary file. At Time — Mechanica calculates the value of a measure at a time you specify. The measure is calculated only for a transient thermal analysis. • • • • 560 Structural and Thermal Simulation If you select Maximum, Minimum, or Maximum Abs as an evaluation method, the second drop-down menu appears: • • Over Analysis — Mechanica calculates the value over all the time steps of the transient thermal analysis. Over Time Range — Mechanica calculates the value over a specified time range of the transient thermal analysis. If you select the Time Stamp check box, Mechanica creates a time stamp measure that saves the time at which a maximum, minimum, or max abs condition occurs. Phase Type The following options appear on the second option menu if you select the Phase quantity: • • • • • • of of of of of of Displacement Velocity Acceleration Rotation Rotational Velocity Rotational Acceleration Quantity for Measure Definition Use the Quantity option menu on the Measure Definition dialog box to select the quantity for which you define your measure. The list of available quantities varies depending on whether you are running Structure or Thermal. These are the possible choices for your selection: Structure • • • • • • • • • • Stress Strain Displacement Rotation Velocity Acceleration Rotational Velocity Rotational Acceleration Phase Failure Index • • • • • • • • • Fatigue Force Moment Moment of Inertia Center of Mass Time Driven Pro Parameter Contact Computed Measure • • • • • • Thermal Temperature Temperature Gradient Heat Flux Time Driven Pro Parameter Computed Measure 561 Structural and Thermal Simulation - Help Topic Collection UCS-Based Measures If you want to use a UCS in creating a measure, you must define the UCS before you define the measure. If you are using a UCS, the references to the WCS X, Y, and Z axes on the dialog boxes are replaced as follows: Cartesian UCS X Y Z Cylindrical UCS R T Z Spherical UCS R T P Note that displacement measures associated with cylindrical coordinates in the T direction, or spherical coordinates in the T or P directions, are in units of length, not angle. If you select any of the options on the Measure Definition dialog box that require a coordinate system selection, use the arrow button to select a coordinate system relative to which you define the measure. The default coordinate system is the WCS. You can also select a UCS. For more information, see About Coordinate Systems. Spatial Evaluation — Structure Select a spatial evaluation method from this option menu on the Measure Definition dialog box. The menu displays only those options that are valid for the quantity and component combination you selected and does not appear for all combinations. After you select the spatial evaluation type from the first option menu, you may see additional option menus or buttons. Some of the spatial evaluation options require that you select a point or several points and appropriate reference entities. You can select them using the arrow button. Your selection from the following menu determines the type of value Mechanica calculates: • • • • At Point — Mechanica calculates the value at the point or points you select. Maximum — Mechanica calculates the maximum value. This option is not available for Min Principal or Max Abs Principal components. Minimum — Mechanica calculates the minimum value. This option is not available for Max Principal or Max Abs Principal components. Maximum Abs — Mechanica calculates the value with the greatest absolute value. This option is not available if you selected Max Principal, Min Principal, or any of the components for the Fatigue quantity, or if you selected Magnitude as the component for another quantity. 562 Structural and Thermal Simulation For the options Maximum, Minimum, and Maximum Abs, a second option menu appears. For the At Point option, this menu appears as an advanced option only if you selected Stress, Strain, Failure Index, or Fatigue as your quantity. The menu contains the following items: • • Over Model — Specifies that Mechanica evaluates the quantity's maximum, minimum, or maximum absolute value over the entire model. This option is not available if you selected At Point. Near Point — Specifies that Mechanica evaluates the quantity's maximum, minimum, or maximum absolute value over the plotting grid points you select within the specified radius. This option is not available if you selected At Point. Over Selected Idealizations — Specifies that Mechanica evaluates the quantity's maximum, minimum, maximum absolute, or at point value over the idealizations you select. Over Selected Components — Specifies that Mechanica evaluates the quantity's maximum, minimum, maximum absolute, or at point value over the assembly components you select. Over Selected Layers — Specifies that Mechanica evaluates the quantity's maximum, minimum, maximum absolute, or at point value over the entities in the selected layers. Over Selected Geometry — Specifies that Mechanica evaluates the quantity's maximum, minimum, maximum absolute, or at point value over the geometric entities you select. • • • • Time Stamp This item is available only if you select Maximum, Minimum, or Maximum Absolute as a time evaluation option. If you select Time Stamp, Mechanica automatically creates a measure that saves the time at which a minimum, maximum, or maximum absolute condition occurs. For dynamic analyses, if you do not create any time- or frequency-based measures, be sure not to select Automatic Intervals within Range for the results output when you define your analysis. Otherwise, some dynamic analyses will not produce any results. Dynamic Evaluation in Structure This drop-down menu appears when you select a dynamic quantity on the Measure Definition dialog box. The quantities include Velocity, Acceleration, Rotational Acceleration, and so forth. For most other quantities, such as Stress, Displacement, Failure Index, and so forth, the Dynamic Evaluation menu is optional and does not appear unless you select the Time/Frequency Eval check box. 563 Structural and Thermal Simulation - Help Topic Collection The menu may contain all or some of the following items: • • • • • • • At Each Step — Mechanica calculates the value of the measure at each time or frequency step. Maximum — Mechanica calculates the maximum value over all time or frequency steps, or over a specified time range. Minimum — Mechanica calculates the minimum value over all time or frequency steps, or over a specified time range. Max Absolute — Mechanica calculates the maximum magnitude value over all time or frequency steps, or over a specified time range. RMS — Mechanica calculates the root mean square value of the measure over the frequency range. Apparent Frequency — Mechanica calculates the effective frequency of a PSD output by integrating over the frequency range. At Time — Mechanica calculates the value of a measure at a specified time. The measure is calculated only for dynamic time analyses. The Dynamic Evaluation area also includes a Time Stamp check box that you can use to obtain information on the time at which Mechanica satisfies your measure quantity and component. Meshes Native Mode Meshes About AutoGEM Use commands on the AutoGEM menu to create and work with AutoGEM meshes in native mode. AutoGEM is the Mechanica Automatic Geometric Element Mesher. Because the finite elements that Mechanica's AutoGEM mesher creates are very accurate to underlying model geometry, these elements are sometimes called geometric elements. The commands on the AutoGEM menu help you verify whether Mechanica can successfully mesh your model prior to analysis and enable you to indicate how you want your model treated during meshing. Reviewing the mesh prior to analysis can help you determine whether the mesh will be successful and, if not, which geometry problems caused AutoGEM to fail. You can then use several techniques to fix mesh problems and ensure that the engine uses the corrected mesh. The AutoGEM menu includes the following commands: • Control — Create AutoGEM mesh controls for your model. When you select the Control command, the AutoGEM Control dialog box appears. Use the dialog box to impose mesh controls on your model, thus improving the mesh in problem areas. Create — Create an AutoGEM mesh for your model. When you select the Create command, the AutoGEM dialog box appears. Use the dialog box to create, review, and save the mesh. If a mesh file is already present, the Create command automatically loads the mesh elements. • 564 Structural and Thermal Simulation • • • • Settings — Review and alter AutoGEM's basic settings and limits. When you select the Settings command, the AutoGEM Settings dialog box appears. Use the dialog box to control the types of activities AutoGEM performs when generating elements and to modify element shape parameters such as aspect ratio and maximum edge turn. Adjustments to the AutoGEM Settings dialog box are a possible method of correcting mesh problems. Geometry Tolerance — Refine geometry tolerance settings for your model to improve the geometry prior to meshing. When you select the Geometry Tolerance command, the Geometry Tolerance Settings dialog box appears. Use the dialog box to ensure that Mechanica resolve slivers, cusps, and other geometry problems in your model. Mesh treatment options — There are three model treatment options— Solid, Midsurface, and Solid/Midsurface. You use these options for models that include midsurfaces. These options enable you to specify whether Mechanica will treat your model as a solid, midsurface shell, or a mixture of both during meshing and analysis. Datum usage options — There are two datum usage options—Use Datum Curves and Use Datum Surfaces. These options let you refine your mesh, place certain idealizations on datum geometry, mesh datum geometry without having to add properties, and control transfer of datum geometry to independent mode. While meshing your model using commands on the AutoGEM menu, AutoGEM creates mesh elements that you can later use when calculating displacements, reactions, stresses, thermal fluxes, and temperatures. If you want Mechanica to use these elements when running an analysis or design study, you need to select the Use Elements From Existing Mesh File option on the Run Settings dialog box. If you do not want to use the AutoGEM elements, you can direct Mechanica to create new elements by selecting the Create Elements During Run option on the Run Settings dialog box. When it meshes your model, AutoGEM uses the default element type for the model type unless you specify otherwise. For example, in 3D models, solid tetrahedra are the default element type. However, before you create the AutoGEM mesh, you can manually create idealizations or connections—for example, shells, springs, masses, welds, and so forth—to alter or enhance the default AutoGEM mesh by incorporating additional element types that better reflect aspects or behaviors of your model. Controlling an AutoGEM Mesh Use the AutoGEM>Control command to control mesh distribution in your model. With the Control command you can: • Control the size and refinement of elements in a mesh by specifying the number of nodes that you want Mechanica to create along the selected edges and by indicating the node placement interval. During mesh creation, Mechanica creates elements that comply with the number and interval you specify. Insert more nodes on specified edges than AutoGEM might normally create. • 565 Structural and Thermal Simulation - Help Topic Collection • Control creation of elements in a mesh by ignoring edges or datum curves with lengths smaller than or equal to the length you specify. You can also choose to retain such edges or curves during mesh creation. When you select the AutoGEM>Control command, Mechanica opens the AutoGEM Control dialog box. The AutoGEM Control dialog box includes these fields: • • Name — Specify the name for the AutoGEM control. Type — Select one of these control types for mesh creation: • Edge Distribution — Select the surface edges or curves and specify the number of nodes associated with these edges. • Minimum Edge Length — Specify the edge length. Normally, AutoGEM meshes all edges in your model. However, if you apply this mesh control, AutoGEM ignores edges with lengths smaller than or equal to the length you have specified. You can also choose to retain such edges or curves during mesh creation. Depending on the mesh control type you specify in the Type field, the active fields in the lower area of the dialog box change. For information on this area, use the links in the list above to learn more about the dialog box version for each mesh control type. After you have created AutoGEM mesh controls for your model, you can edit or delete it by selecting the associated icon on your model and using Edit>Definition or Edit>Delete, as appropriate. If you are deleting a mesh control, Mechanica asks for confirmation first. Edge Distribution Use Edge Distribution on the AutoGEM Control dialog box to specify the number of nodes and their placement intervals along curves or surface edges. Mechanica uses the specified number of nodes when creating elements in a mesh. By specifying the number of nodes on curves or surface edges, you control the number of nodes for a beam, shell, and solid element. Note: The edge distribution you define at the part or assembly component level remains active and visible at the assembly level. If you select Edge Distribution, you specify the following: • References — Select one or more curves or edges for AutoGEM control. Mechanica displays an arrow on the specified edge to indicate the direction of node distribution. To reverse the direction of node distribution, select the same edge or curve again. Number of Nodes — Specify the number of nodes along the selected edge or curve. If you specify an insufficient number of nodes, Mechanica may increase the number of nodes based on the requirement and complexity of the model geometry. The value that you specify in the Number of Nodes field overrides the Insert Points setting on the AutoGEM Settings dialog box's Settings Tab. • 566 Structural and Thermal Simulation • • First/Last Nodal Interval Ratio — Select this option to specify the ratio of the first interval on the edge or curve to the last interval on the edge or curve. For example, if you enter 3 as the ratio, the last interval is 3 times the length of the first interval. Mechanica places the intermediate nodes at graduating intervals proportional to the ratio. If you enter a ratio of 1, all the intervals are equidistant. Prevent Additional Nodes — Ensure that the number of nodes that AutoGEM creates is exactly the same as specified in AutoGEM control. If you have not specified a sufficient number of nodes, Mechanica displays a warning and may insert additional nodes based on meshing requirements. Note: Selecting this option can cause AutoGEM to fail, thus you should select this option only if it is absolutely necessary. To Control Edge Distribution in an AutoGEM Mesh 1. Select AutoGEM>Control or click appears. . The AutoGEM Control dialog box 2. Enter a name for the AutoGEM control. 3. Select Edge Distribution as the type of control. 4. Select the edges or datum curves to which you want to apply the edge distribution control. 5. Enter the number of nodes along the selected edge or curve. 6. Enter the ratio of the first interval on the edge or curve to the last interval on the edge or curve. 7. If you want to ensure that the number of nodes that AutoGEM creates is exactly the same as you specified in the Number of Nodes field, select Prevent Additional Nodes. 8. Click OK. Minimum Edge Length Use the Minimum Edge Length option on the AutoGEM Control dialog box to ensure that AutoGEM ignores the edges and datum curves with lengths smaller than or equal to the length you specify. If you are working with an assembly, you must define the minimum edge length control at the top assembly level. The edge length you specify is globally valid for the model. When it meshes your assembly, Mechanica disregards any Minimum Edge Length controls that you assigned at the part or component level. If you select Minimum Edge Length, you specify the following: • Edge Length — Specify the edge length. AutoGEM ignores edges and datum curves with lengths smaller than or equal to the length you specify. You can specify the value for Edge Length as an absolute value by entering a number and making sure the % check box is off. Alternatively, you can use the % 567 Structural and Thermal Simulation - Help Topic Collection check box to specify the minimum edge length as a percent of the longest edge of a bounding box that surrounds the model. For example, if you specify 10% as the minimum edge length and the longest edge in the model bounding box is 5, Mechanica ignores all the edges with length less than 0.5. Note: Mechanica does not ignore the edges or curves with lengths less than the specified Minimum Edge Length if the edges or curves are referenced by a load, constraint, or a beam. • Select Edges/Curves to Keep — Retain selected edges or curves in the model even if edges orcurves are shorter than the edge length you have specified. After you define the Minimum Edge Length control, you can use the Preview button to verify that you have correctly selected the edges/curves you want AutoGEM to retain and to see which edges or curves it will ignore during meshing. Mechanica indicates this by highlighting the edges or curves you have chosen to retain and marking the edges or curves that are less than or equal to the Edge Length value with purple circles. To Control Minimum Edge Length in an AutoGEM Mesh 1. Select AutoGEM>Control or click appears. . The AutoGEM Control dialog box 2. Enter a name for the AutoGEM control. 3. Select Minimum Edge Length as the type of control. 4. Enter the minimum length of the edges or datum curves that you want AutoGEM to retain when it meshes the model. AutoGEM ignores all edges equal to or less than this length. 5. Optionally, select the % checkbox to specify the Edge Length field as a percentage. 6. Click Preview to display a preview of the edges or datum curves that AutoGEM will ignore. 7. If you want to retain some of the ignored edges or datum curves regardless of length, click Select Edges/Curves to Keep and use the selector arrow to select the edges. 8. If you want to verify that you have selected the correct edges, click Preview again to highlight the edges selected to be retained regardless of length. 9. Click OK. 568 Structural and Thermal Simulation Creating and AutoGEM Mesh Preparing Your Model Before using AutoGEM, you should take the following steps to ensure that AutoGEM creates the best set of elements for your model: • • If you know in advance that you want more solid or shell elements near a specific location, add geometry or simulation features that AutoGEM can use to refine the mesh, such as datum points, curves, surfaces, or regions. Before using AutoGEM on a curve for 3D models, you need to assign a beam idealization. AutoGEM automatically creates beam end points, as required, so you do not need to add datum points. Note: When you select a curve for AutoGEM and the curve does not have a beam idealization, AutoGEM will mesh the curve, but you will encounter problems at analysis time if you have not fully defined the beam. To prevent problems of this sort, we recommend always adding the beam idealization before you run AutoGEM. • • • Before using AutoGEM on a curve for 2D models, you need to assign a simple or advanced shell idealization. Before using AutoGEM on a surface for 2D plane stress models, you need to assign a simple or advanced shell idealization. When you use AutoGEM on a surface or volume, make sure that the Insert Points and Move Or Delete Existing Points options on the Settings tab of the AutoGEM Settings dialog box are selected. For most cases, these options enable AutoGEM to generate the best set of elements. When you use AutoGEM on a surface, make sure all the options under Isolate Features are active. These options direct AutoGEM to isolate: o reentrant corners on individual surfaces o points with loads or constraints in Structure or with heat loads, prescribed temperatures, or convection conditions in Thermal • AutoGEM Dialog Box When you select the AutoGEM>Create command, the AutoGEM dialog box appears. The options and menus on the dialog box enable you to perform the following functions: • • • Create solid, shell, and beam element meshes on geometry that you specify using the AutoGEM References area. After you create the mesh elements, you can remove them from any selected geometric entity. Review and evaluate information about geometry and elements in your model using the Info menu. You can identify any missing elements in your model or determine whether geometry problems exist. Manage your mesh files through the File menu. After completing an AutoGEM session, you can save your mesh. To avoid re-meshing your model later, you can retrieve and display a previously created mesh. 569 Structural and Thermal Simulation - Help Topic Collection Creating AutoGEM Mesh Elements Use the AutoGEM References area of the AutoGEM dialog box to add mesh elements to your model. The type of elements AutoGEM creates depends on the geometry you select. Use the following option menu to specify geometry that you want to mesh: • All With Properties — Instructs AutoGEM to automatically mesh all curves, surfaces, and volumes that have properties assigned to them. As AutoGEM automatically chooses the geometry for you, you cannot select specific geometry with this option. If there are no properties in the model, the Create button is inactive. Component Volumes — Enables you to select component volumes, for which you want AutoGEM to create solid elements. This option is only available when you work with assemblies. Volume — Enables you to select specific volumes, for which you want AutoGEM to create solid elements. Surface — Enables you to select surfaces, for which you want AutoGEM to create shell elements for 3D models, 2D plate elements for 2D plane stress models, and 2D solids for all other 2D models. Curves — Enables you to select curves, for which you want AutoGEM to create beams or, for 2D models, 2D shells. • • • • After you make your selection, use one of these buttons: • Create — Click this button when you are ready to mesh the selected geometry. AutoGEM begins the meshing process, regularly displaying messages that indicate its progress. You can interrupt the meshing process at any time by clicking the Pro/ENGINEER Stop sign in the lower right corner of the screen. For more information, see Interrupting AutoGEM. Usually AutoGEM completes its session successfully and opens the AutoGEM Summary dialog box at the end. Occasionally, your model may fail to mesh, especially if you are working with complicated geometry, such as irregular surfaces or volumes, or you are working with assemblies where the accuracy values for the components are not close enough. For a more detailed overview of AutoGEM meshing for these geometry types, and the strategies you can use to remedy AutoGEM failure, see Volume or Surface. • Delete — Click this button if you want to remove a created mesh from the selected geometry. You can use the Mesh tab on the Simulation Display dialog box to control the appearance of meshes that AutoGEM generates. 570 Structural and Thermal Simulation AutoGEM File Menu The File menu on the AutoGEM dialog box contains these commands: • • • Load Mesh — Load the elements. This command is accessible when your model's mesh file is present in the current directory. Copy Mesh from Study — Copy a mesh from an existing design study directory. When you select this option, a Design Study Selection dialog box opens, from which you can select a study that you want to use. Save Mesh — Save your mesh. Mechanica assigns a name of model.mmp to a mesh file of a part and model.mma to an assembly mesh file. The files reside in the current directory. If you are working with family tables or have simplified representations of your model, see the guidelines that Mechanica follows when naming your mesh files. Close — Close the dialog box. If you have not saved the mesh with the Save Mesh command, the software asks whether you want to save your mesh now. • AutoGEM Info Menu Use this menu on the AutoGEM dialog box to review information about geometry and elements in your model. The menu contains these items: • • Model Summary — Display a report of all elements present in your model. This report appears in the Model Summary dialog box. Boundary Edges — Highlight all boundary edges. A boundary edge is an edge associated with only one shell and not associated with any solids. You can use this information to identify missing elements. If there are no boundary edges in your model, Mechanica informs you of this. Boundary Faces — Highlight all boundary faces—faces that belong to only one solid and are not associated with a surface. You can use this information to identify missing elements. If there are no boundary faces in your model, Mechanica informs you of this. Approximated Elements — Highlight the elements with approximated linear edges that AutoGEM has created to complete the mesh in the areas of your model where geometry problems exist. Because these elements can affect the accuracy of your analysis, you should review the areas of your model that contain approximated elements. AutoGEM Log — Open an AutoGEM log file, which contains information about the most recent AutoGEM session. Validate Mesh — Verify that all elements in the model meet the element creation limits. • • • • 571 Structural and Thermal Simulation - Help Topic Collection Element Types Solid Elements A solid element is a three-dimensional element that: • • you use to subdivide a volume has a cross-section and thickness that can vary A solid contains triangular faces, quadrilateral faces, or a combination of both. There are three types of solid elements: • Brick — an element with two opposite quadrilateral faces and four faces between the two opposite faces. Bricks are useful in models that include volumes with two opposing faces with a similar shape—whether the volumes are curved or planar. To connect a brick to a tetrahedron, AutoGEM must create links so that triangular faces of two tetrahedrons can interface with a single quadrilateral brick face. Wedge — an element with two opposite triangular faces and three quadrilateral faces between the two opposite faces. Wedges are useful in models that include volumes with two opposing faces with a similar shape— whether the volumes are curved or planar. They are more versatile than bricks because AutoGEM can connect wedges to both tetrahedrons and bricks without needing to create links. Tetrahedron — an element with one triangular face and an opposite point. The element has three triangular faces between the triangular face and the opposing point. Tetrahedrons are the most widely used of the solid element types. Tetrahedrons function dependably for models with regular geometry, but also provide an excellent solution for models with irregular shapes and features. • • Shell Elements A shell element is a two-dimensional element that: • • you use to subdivide a structure that is relatively thin compared to its length and width has a constant cross-section and thickness When creating shell elements, AutoGEM subdivides the shell surface into the following element shapes, depending on what you specify on the Settings tab: • • Quadrilaterals — AutoGEM creates four-sided elements. Triangles — AutoGEM creates three-sided elements. For most model types, AutoGEM adds shells to your model if you have defined shell idealizations. In assigning thickness for a simple or advanced shell idealization, be aware that the thickness of resulting shell elements should be significantly smaller than the length of any of the body's other dimensions and radii of curvature. 572 Structural and Thermal Simulation Note: If the shell element is too thin, Mechanica may have difficulty analyzing it. As a guideline, the ratio of the shell element's thickness to its other dimensions should be no greater than 1 to 10 and no less than 1 to 1000. Beam Elements A beam is a one-dimensional element that: • represents a structure whose length is much greater than its other two dimensions. The cross-sectional dimensions of geometry you model with one or more beams should be small compared to the overall length and radii of curvature. As a guideline, the ratio of the length to the other dimensions should be no less than 10 to 1. has a constant cross-section and thickness in native mode • Beams are only available for 3D models. AutoGEM adds beams to your model if you have defined beam idealizations either on a curve or between a set of points, as follows: • If you define a beam idealization on a curve, AutoGEM adds beams over the length of the curve to reflect the curve's geometry. For example, if the curve is linear, AutoGEM adds one beam. However, if the curve is a spline, AutoGEM adds as many individual beams as needed to follow the profile of the curve. If you define a beam idealization from a point or vertex to another entity type (point, surface, curve, and so forth), AutoGEM projects a single linear beam from the point or vertex to the entity. • AutoGEM also adds beams if you have defined spot weld connections. Mass and Spring Elements In Structure, you can add two special-purpose elements to your model—masses and springs. These elements provide you with the ability to idealize the behavior of your model more exactly. Here is a brief discussion of these two element types: • Mass — A mass element is a one-point element that you use to represent a concentrated mass without a specified shape. The mass of an object determines how that object resists translation and rotation. Mass elements: o have no effect on a static analysis unless the analysis includes a gravity load or a centrifugal load o do have an effect on a modal or dynamic analysis You indicate that you want Mechanica to add masses to your model by creating mass idealizations. • Spring — A spring element represents a linear elastic spring connection that you can define from one point to another or from a point to ground. Springs: o provide stiffness at the locations where you place them 573 Structural and Thermal Simulation - Help Topic Collection o act as constraints in your model and, in some instances, may be all the constraint that you need. However, while a spring can remove degrees of freedom in one direction, it can allow freedom of movement in other directions. If you are using a point-to-ground spring, your model is fully constrained at the point where the spring connects to ground. You indicate that you want Mechanica to add springs to your model by creating spring idealizations. 2D Elements Mechanica creates three types of 2D elements. Of these three types, Mechanica uses only those that are applicable to the type of 2D model you are working with. For example, Mechanica uses 2D solid elements and 2D shell elements for 2D axisymmetric models, but does not use 2D plate elements for this model type. The three element types are: • 2D shell — A 2D shell is a one-dimensional element that has constant thickness and represents a shell in one of the following models: o 2D plane strain o 2D axisymmetric 2D shell elements are linear but can be curved or straight, much as a beam element would be in a 3D model. • 2D solid — A 2D solid is a two-dimensional element that represents a slice of a solid in one of the following models: o 2D plane strain o 2D axisymmetric Because 2D solid elements represent a slice, they have no actual thickness. 2D solid elements are quadrilateral or triangular, much as a shell element would be in a 3D model. • 2D plate — A 2D plate is a two-dimensional element that represents a solid in a 2D plane stress model. It is very thin in the Z direction, but does have an associated thickness. 2D plate elements are quadrilateral or triangular, much as a shell element would be in a 3D model. All 2D elements must lie in: • • the XY plane of a Cartesian coordinate system for all 2D models the positive X half of the XY plane for 2D axisymmetric models As mentioned, 2D shell and 2D plate elements have a constant thickness. You determine this thickness when you create the simple or advanced shell idealization upon which the 2D shell or 2D plate element will be based. In assigning thickness for the shell idealization, be aware that the thickness of 2D shell and 2D plate elements 574 Structural and Thermal Simulation should be significantly smaller than the length of any of the body's other dimensions and radii of curvature. Note: If the 2D shell or 2D plate element is too thin, Mechanica may have difficulty analyzing it. As a guideline, the ratio of the 2D shell or 2D plate element's thickness to its other dimensions should be no greater than 1 to 10 and no less than 1 to 1000. Element Type and Geometric Entity The type of elements AutoGEM generates depends on the geometry you select and the model type: Geometric Entity Element Type for Solid Models beams springs (S) masses (S) beams shells solids Element Type for 2D Plane Strain and 2D Axisymmetric Models springs (S) masses (S) Element Type for 2D Plane Stress springs (S) masses (S) points curves surfaces volumes 2D shells 2D solids 2D plates Note: In the above table, S indicates that the element is available for Structure only. AutoGEM generates a full set of elements on the geometry you select in most cases. The amount of time AutoGEM needs to create elements varies with: • • • the type of geometry that you are using the number of geometric entities that you select the number of complex features in the selected geometry Although there is no limit to the number of elements it can create, you should strive for AutoGEM to use the minimum possible number of elements to take full advantage of geometric element analysis, and reduce analysis time. Tip: You may want to add mesh controls, create points, or use other techniques to subdivide any element for which you need especially detailed data. 575 Structural and Thermal Simulation - Help Topic Collection For 3D model types, remember that the more complex the element you use, the more computation time Mechanica requires. Here are the 3D element types listed from least computation time to most: 1. 2. 3. 4. Beams Flat shells Curved shells Solids If you can build the model using one of the 2D model types, the solution takes much less time. Where appropriate, you can also create symmetry constraints that will further reduce element counts. For example, you can greatly simplify some axisymmetric models by using cyclic symmetry. Types of Elements in Structure The types of elements that Mechanica creates vary according to the model type you selected. The elements Mechanica creates for each Structure model type are: 3D 2D Plane Strain and 2D Axisymmetric mass spring 2D shell 2D solid 2D Plane Stress mass spring beam shell (quadrilateral or triangular) solid (tetrahedra, bricks, and wedges) mass spring 2D plate Types of Elements in Thermal The types of elements that Mechanica creates vary according to the model type you selected. The elements Mechanica creates for each Thermal model type are: 3D 2D Plane Strain and 2D Axisymmetric 2D shell 2D solid 2D Plane Stress beam shell (quadrilateral or 2D plate 576 Structural and Thermal Simulation 3D 2D Plane Strain and 2D Axisymmetric 2D Plane Stress triangular) solid (tetrahedra, bricks, and wedges) How AutoGEM Uses Existing Geometry AutoGEM uses existing geometry as follows: • • For 3D models,the Curve option creates beam endpoints on all points associated with curves. The Surface option creates element edges on: o o • surface boundary curves interior curves associated with surfaces The Surface option creates element endpoints on: o o points associated with those curves points directly associated with surfaces • The Volume option creates element edges on all curves associated with boundary surfaces. Boundary surfaces are surfaces along the outer or inner boundary of a volume. The Volume option creates element endpoints on: o o all points associated with curves on boundary surfaces all points directly associated with boundary surfaces AutoGEM creates, moves, deletes, or ignores geometry as follows: • • • AutoGEM creates multiple edges on a single curve if needed to make the element valid. For example, if a curve spans an arc angle of more than 95 , AutoGEM creates more than one edge on that curve. AutoGEM adds extra points to surface interior and boundary curves if needed to generate a complete set of elements. AutoGEM moves points or deletes unnecessary points created during meshing unless you deselect the Move or Delete Existing Points option on the Settings tab. It does not, however, move or delete user-created datum points. AutoGEM ignores points and curves that are not associated with the curves, surfaces, or volumes you select. AutoGEM ignores geometry fully encased inside volumes. It does not, however, ignore volume regions or geometry that is associated with the volume boundary. • • 577 Structural and Thermal Simulation - Help Topic Collection How AutoGEM Uses Existing Elements You can use AutoGEM commands on curves and surfaces that are already partially covered with elements. AutoGEM recognizes the existing elements and incorporates them as part of the final set of elements it creates. However, existing elements can overconstrain AutoGEM, resulting in an incomplete set of elements. If you select Modify or Delete Existing Elements on the Settings tab, AutoGEM deletes existing tetrahedral solid and shell elements as required to complete the set of elements. You can also use AutoGEM on volumes with existing elements. With a volume, AutoGEM recognizes solid elements whose faces are directly or indirectly associated with boundary surfaces. A solid is indirectly associated with a boundary surface when a series of adjacent solids extends from the interior of a volume to its boundary. It is sometimes useful to know the number of solid elements in a volume so that you can compare this number with the number AutoGEM reports. By default, AutoGEM links the tetrahedral solid faces it creates to existing brick and wedge quad faces. Note: If you do not want AutoGEM to use existing elements, you must delete the elements before carrying out an AutoGEM command. Surface Select the Surface option in the AutoGEM References area of the AutoGEM dialog box to create shell elements, 2D plate elements, or 2D shell elements on one or more surfaces that you select. AutoGEM creates the type of element appropriate for your model type. The description of the Surface command is divided into the following sections: • • Using Surface Strategies for Using the Surface Option Using Surface When you select the Surface option, Mechanica asks you to select one or more surfaces. It then begins to preprocess your model. Preprocessing evaluates your model to determine if the surfaces and topology of your model are meshable, and prepares your model to be meshed. AutoGEM displays messages if it determines, during this phase, that it will not be able to mesh the model given the element limits or other conditions. After preprocessing is complete, AutoGEM creates a set of shell elements for the model. AutoGEM attempts to optimize elements by trying different element combinations until it finds a set that best meets its criteria. 578 Structural and Thermal Simulation Note: Element optimization for shells is typically very fast. If you think that it is taking too long, you can interrupt the process. Provided you selected the Quad and Tri option on the Settings tab of the AutoGEM Settings dialog box, AutoGEM tries to reduce the number of elements where possible after it creates a complete set of elements. It reduces elements by combining triangular elements into quadrilateral elements. While you can interrupt AutoGEM, allowing it to complete this stage can result in a noticeable reduction in elements, often by 50% or so. If your model includes idealizations such as beams, springs, or masses, AutoGEM first meshes the surfaces, adding shell elements. It then adds the beams, springs, and so forth. If AutoGEM completes successfully, the AutoGEM Summary dialog box appears. If AutoGEM does not complete successfully, it displays messages or message boxes explaining the problem and adds this information to the log file. Strategies for Using the Surface Option If AutoGEM has not created a full set of elements on the surfaces you selected, or if you want a different set of elements than what AutoGEM created, you can try one or more of the following steps: • • • Use the Boundary Edges option on the AutoGEM Info menu to find and examine unfinished areas of the model. Inspect the geometry, for problems. If you deselect the Insert Points and Move Or Delete Existing Points options, AutoGEM creates the best set of elements possible without inserting or moving points. Deselecting these options gives you more control over the elements AutoGEM creates. In rare cases, reduce the minimum edge angle, increase the maximum edge angle, or increase the aspect ratio on the Limits tab. If you are working with an assembly that fails to mesh, use Info>Tolerance Report to check the component tolerances to make sure that they are close enough. If not, return to Pro/ENGINEER and use Edit>Setup>Accuracy to change the accuracy values of any component whose tolerance appears to be too high. • • lume Select the Volume option in the AutoGEM References area of the AutoGEM dialog box to create solid elements in one or more volumes that you select. The description of Volume is divided into the following sections: • • Using Volume Strategies for Using the Volume Option 579 Structural and Thermal Simulation - Help Topic Collection Using Volume When you select the Volume option, Mechanica asks you to select one or more volumes. It then begins to preprocess your model. Preprocessing searches your model for existing elements, evaluates your model to determine if the surfaces and topology of your model are meshable, and prepares your model to be meshed. If any preprocessing step requires more than 30 seconds, AutoGEM displays messages in the command area indicating its progress. AutoGEM also displays messages if it determines, during this phase, that it will not be able to mesh the model given the element limits or other conditions. After preprocessing is complete, AutoGEM searches for existing elements, and creates a mesh as follows: • • If it finds existing elements, AutoGEM retains these elements and begins to build a mesh using the existing elements as a starting point. If it does not find existing elements, AutoGEM creates an entirely new set of elements. In either case, AutoGEM attempts to optimize elements by trying different element combinations until it finds a set that best meets its criteria. Mechanica regularly updates the status messages concerning how many elements AutoGEM has created. This gives you a general idea of how AutoGEM is progressing. If you think that it is taking too long, you can interrupt the process. See Interrupting AutoGEM for information on using completion status to determine if you should interrupt AutoGEM. After AutoGEM creates a complete set of elements, it tries to reduce the number of elements where possible. While you can interrupt AutoGEM, allowing it to complete this stage usually results in a 30–70% reduction in elements. If your model includes idealizations such as shells, beams, springs, or masses, AutoGEM first meshes any volumes, adding solid elements. It then creates the shell mesh and, finally, adds the beams, springs, and so forth. If necessary, AutoGEM shifts between solid and shell meshing to meet the mesh quality criteria. If AutoGEM completes successfully or you interrupt it, the AutoGEM Summary dialog box appears. If AutoGEM does not complete successfully, it displays messages or message boxes explaining the problem and adds this information to the log file. Strategies for Using the Volume Option The following are some strategies you can follow to use Volume more effectively: • • • If the boundary processing stage takes too long, interrupt AutoGEM. If AutoGEM has not created a full set of elements on the volumes you selected, you can try one or more methods listed in Create a Full Set of Elements. Volume can be very sensitive to increasing the minimum face and edge angles above 5 on the dialog box, especially for complex parts. Sometimes, 580 Structural and Thermal Simulation • • • increasing the minimum face angle a couple of degrees can result in many more tetrahedral elements and take much longer to complete. AutoGEM can handle multiple volumes that share common surface regions. When you use Volume, select all volumes at the same time. If you want to create elements for a thin region, for example, sheet metal, use the Settings tab on the AutoGEM Settings dialog box to select wedges, bricks, and tetrahedrons as the elements for AutoGEM to use. For parts that have both thick and thin regions, AutoGEM uses wedges, bricks, and tetrahedrons and automatically creates links where required. If you are working with an assembly that fails to mesh, use Info>Tolerance Report to check the component tolerances to make sure that they are close enough. If not, return to Pro/ENGINEER and use Edit>Setup>Accuracy to change the accuracy values of any component whose tolerance appears to be too high. Status Messages While meshing your model, Mechanica displays and regularly updates status messages that give you a general idea of how AutoGEM is progressing. The following are some tips on how to interpret these messages: • The completion percentage is based on a simple estimate of how many total elements Mechanica will need for the selected volume. The actual number of elements Mechanica creates may vary significantly from these interim estimates. The completion percentage estimate can increase even as the number of elements created decreases. This only indicates that AutoGEM is changing its estimate of how many elements will be needed to complete the selected volumes as it tries different combinations of elements. The completion percentage sometimes decreases at least a few times during element creation. Even if AutoGEM appears to stall at a particular completion percentage, it will usually complete successfully. • • If AutoGEM Completes Successfully If AutoGEM completes successfully, the AutoGEM Summary dialog box appears, displaying: • • • • • Entity Count — number of elements, edges, faces, and links created Criteria Satisfied — minimum and maximum edge angles used Max Aspect Ratio — aspect ratio of a solid face's length to its width and a shell's length to its width. You can control the maximum allowable aspect ratio through the Limits tab on the AutoGEM Settings dialog box. Elapsed Time — elapsed time that the command used CPU Time — CPU time that the command used 581 Structural and Thermal Simulation - Help Topic Collection Interrupting AutoGEM You can interrupt AutoGEM at any time by clicking the Pro/ENGINEER stop sign in the lower right corner of the screen. You may want to interrupt for one of the following reasons: • • AutoGEM has been running for an unexpectedly long time. The command line messages indicate that AutoGEM is not making progress in creating new elements. Consult the guidelines for deciding when to interrupt AutoGEM to learn more about the factors you should weigh. If you interrupt the meshing session: • • before you see the Creating element type elements status message, AutoGEM will not create any elements after you see the status message, AutoGEM will usually create only a partial set of elements AutoGEM usually responds to your interrupt request rapidly. If AutoGEM has already begun to create elements, it displays a message box indicating the current element completion percentage, how many elements AutoGEM has created, or what meshing process AutoGEM is currently performing. The message box prompts you to decide whether you really want to stop the mesh. If you click Yes, the software opens the AutoGEM Summary dialog box. If you click No, AutoGEM resumes creating the mesh. When you interrupt AutoGEM during element creation, Mechanica displays the mesh in its current, incomplete state. You can study the mesh and determine where the problems might lie. After you correct any problems by adding datum geometry to refine the mesh in the problem areas, relaxing the element limits, or a variety of other methods, you can run AutoGEM against the existing mesh to complete the element creation process. Diagnosing AutoGEM Problems Mechanica writes AutoGEM status and error messages to the log file. The file also contains a summary of the AutoGEM portion of the run, including the number of elements AutoGEM created. If AutoGEM is unable to create a complete set of elements for your model, Mechanica writes an error message to the log file. You can inspect the mesh and the log file to determine where the problem might lie and which areas of the geometry might be suspect. Pay particular attention if your model demonstrates an unexpectedly high element count given the geometry, shows unusual element concentrations often indicated by dense point clouds. You can also determine modeling errors after performing an analysis by selecting the Info>Diagnose menu option on the Analyses and Design Studies dialog box. 582 Structural and Thermal Simulation After you identify the problem, the best way to fix the geometry may be to modify the part dimensions. For example, if a hole that you intended to go through your part does not extend far enough, the part may have an extremely thin region that is not practical to mesh. Another example of geometry that can cause meshing problems is a cosmetic round with a very small radius. You can suppress these features before you analyze the part. See Strategies for Using the Surface Option and Strategies for Using the Volume Option for more information on actions you can take to fix AutoGEM problems. Using the AutoGEM Log File Log You can access the AutoGEM log file by selecting Info>AutoGEM Log on the AutoGEM dialog box. The AutoGEM log file provides information about the most recent AutoGEM operation you executed for the current model. You can access the AutoGEM log file regardless of whether AutoGEM completed successfully or unsuccessfully, or whether you interrupted it. Mechanica saves: • • the AutoGEM log file as model_name.agm (where model_name is the name of your model) the previous AutoGEM log file, if one exists, as model_name.agb These files are overwritten with each successive AutoGEM session. If you want to save a particular AutoGEM log file, you can rename it through the operating system. AutoGEM Log File Information The log file provides the following information: • • • A brief introduction about the AutoGEM session A summary of the AutoGEM settings you specified for your model A history of the command line messages, status messages, error messages, and informational messages AutoGEM issued during the session. This includes feedback normally issued through message boxes as well as command and status area messages. A summary of the elements, edges, faces, and links created during the run and the criteria, such as aspect ratio and edge and face angles, satisfied by the run • You can access the AutoGEM log file regardless of whether AutoGEM completed successfully or unsuccessfully, or whether you interrupted it. 583 Structural and Thermal Simulation - Help Topic Collection Example: Reducing the Element Count If you run an analysis or design study and find out that your model has too many elements, you can change certain values on the Limits tab—typically the value in the Allowable Angles field. Even slight changes in this field can result in a substantial lowering of the element count. For example, if you determine that AutoGEM created 10,000 elements for a fairly simple model, you can consider changing the Allowable Angles value. In this case, you might reduce the minimum edge and face angles from 5 to 2. You might also increase the maximum edge and face angles from 175 to 178. Although these appear to be minor changes, they can reduce the number of elements by 20-30%. Note that you do not increase the allowable edge turn. Although increasing the edge turn reduces the number of elements, the reduction is not appreciable. Consequently, setting a value higher than the default generally does not produce dramatic changes in element count. Reduce the Number of Solid Elements If AutoGEM creates more solid elements than you can successfully analyze on your machine, you may need to modify your model in one or more of the following ways: • • • Suppress part features that you know have little or no effect on your results. If your model has an extremely high number of local measures, consider deleting some of these measures. Relax the element quality criteria on the Limits tab. For example, you can use this dialog box to change the minimum and maximum edge and face angles. Changing these angles can significantly lower the number of elements for some parts. However, because the resulting elements are less robust, your model may experience slower analysis convergence. Applying AutoGEM Settings AutoGEM Settings Dialog Box When you select the AutoGEM>Settings command, the AutoGEM Settings dialog box appears. The default settings that Mechanica displays when you first open the AutoGEM Settings dialog box, are optimized to give a superior mesh in most cases. However, AutoGEM may not be able to mesh all models using these defaults. If your model fails to mesh, one approach to remedying the problem is to change the AutoGEM settings or simply alter the values on the Limits tab. For more information about diagnosing element problems, see Diagnose AutoGEM Problems. 584 Structural and Thermal Simulation The dialog box displays these areas and tabs: • • • Feature Isolation — Determines the list of entities that AutoGEM can detect and isolate using mesh refinement. Settings tab — Enables you to control various characteristics of element creation, such as element type and aspect ratio. Limits tab — Enables you to set limits on AutoGEM when it is creating and editing elements. When you save your model, Mechanica saves the AutoGEM settings with the model. These settings then become the current settings when you reopen the model. Feature Isolation This area appears in both Structure and Thermal, and enables you to refine the mesh near certain geometric features or modeling entities. You use this area if your model includes geometry, loads, constraints, or boundary conditions that would result in mathematical singularities. Singularities are areas of theoretically infinite stress or temperature flux and are undesirable because they can skew analysis results. For example, point loads in shell or solid models create singularities, or stress concentrations. In this case, your analysis solution may primarily reflect these stress concentrations, hampering your ability to focus on overall stress behaviors that you may be more interested in. You use feature isolation to surround certain types of singularities in your model with a more refined mesh. When feature isolation is active, Mechanica populates the area around each singularity with small elements. Working outward from the singularity, the element size increases so that it blends compatibly with the overall model mesh. This meshing approach partially compensates for the impact of singularities on the solution by spreading the behavior over a greater number of elements—in effect, isolating the singularities. For the Feature Isolation area, you can select one of two menu options— Structural or Thermal. Below this menu, the dialog box displays a list of entities that commonly cause singularities, and that AutoGEM can detect and isolate when it generates elements. The list is different depending on whether you select Structural or Thermal: Structural Reentrant Corners Point Loads Point Constraints Thermal Reentrant Corners Point Heat Loads Point Prescribed Temperatures Point Convection Conditions 585 Structural and Thermal Simulation - Help Topic Collection AutoGEM detects both structural and thermal entities regardless of whether you are working in either Structure or Thermal. Your model uses the same elements for the structural and thermal versions, so you should check your settings for both the modes before you use AutoGEM. For example, if you are currently in Structure, but the thermal version of your model contains a point heat load, AutoGEM detects only the point heat load if you select that item on the thermal version of this dialog box. If Point Heat Loads is not selected, AutoGEM creates elements that may work well only for the structural version of your model. Settings Tab The tab displays these options: • • • • • • • • • Insert Points — Add extra points when needed to complete a valid mesh. Move or Delete Existing Points — Move or delete existing points when needed to optimize the element configuration for your model. Modify or Delete Existing Elements — Modify or delete existing elements to improve or complete element creation. Automatic Interrupt — Stop AutoGEM automatically after it creates a specified percentage of elements. Create Links Where Needed — Create links when needed to connect shell elements to solid elements or solid quadrilateral faces to solid triangular faces. Detailed Fillet Modeling — Create a greater number of elements near fillets to produce smoother fringe plots. Display AutoGEM Messages — Display the messages and message boxes that AutoGEM generates during its session. Even if you deselect this option, the software writes the messages to the AutoGEM log file. Delete Mesh Points When Deleting Elements — When deleting mesh elements, remove points inserted during an AutoGEM session. Element Types — Create different types of elements: o Shells o Solids Limits Tab The options on this tab enable you to set limits on AutoGEM when it is creating and editing elements. In general, you should use the defaults on the tab. They provide acceptable elements for the greatest number of models. If AutoGEM encounters any problems when generating elements, you can then change some of the settings on the tab to finetune the elements that AutoGEM creates. 586 Structural and Thermal Simulation The tab contains the following items: • Limits For — Enables you to specify what kind of limits you are setting. Select one of the following items from this list: o Creating — AutoGEM limits the angles on elements that it creates either during initial modeling or as the result of a geometry change. o Editing — Editing limits are for element validity after smoothing or editing. A geometry shape change caused by a design parameter change may cause an element to violate the creation limit. If an element violates the editing limit, you must delete the element and allow AutoGEM to create new elements. The limits on angles during AutoGEM element creation are set so that the elements converge well during the analysis. To retain the same element set during editing, the default editing limits are relaxed to reduce the element regeneration that is required. These relaxed editing limits enable AutoGEM to move points, which makes it easier to maintain the original set of elements. When AutoGEM can edit elements by repositioning points, elements are less likely to become invalid and the model is less likely to require element regeneration. • Allowable Angles (Degrees) — Enables you to set minimum and maximum edge and face angles. By widening the spread of the default values, you can reduce the number of elements AutoGEM creates. For an example, see Reducing the Element Count. Max Edge Turn (Degrees) — Enables you to set the maximum subtended edge angle. The lower the number you use in this entry box, the greater the number of elements AutoGEM creates. Max Aspect Ratio — Enables you to set the maximum aspect ratio. Validate — Enables AutoGEM to highlight elements that do not meet the limits. Default — Resets all the displayed values to the default values. • • • • Specifying Mesh Treatment for Models with Midsurfaces The Solid, Midsurface, and Solid/Midsurface options on the AutoGEM menu let you specify whether Mechanica will treat models that include midsurfaces as solid models, midsurface shell models, or a mixture of both during meshing and analysis. These toggle keys are only available in the native mode. In the FEM mode, you indicate model treatment at the time you create the FEM mesh. In models that have no midsurfaces, the Solid option is turned on and the Midsurface and Solid/Midsurface options are deactivated. However, when you define shell pairs for your model, the software automatically activates these two options and turns on the Midsurface option. Provided that you keep the option on, Mechanica meshes and analyzes the model as a shell model. If any potion of the model is a solid, Mechanica omits that portion from the mesh and, consequently the 587 Structural and Thermal Simulation - Help Topic Collection analysis. If you want to include the solid portions of the model, turn on the Solid/Midsurface option instead. For models with midsurfaces, the Midsurface option stays on by default unless you select one of the other two options and then save your model in that state. If you delete all the shell pairs in your model, Mechanica automatically turns off and deactivates the Midsurface and Solid/Midsurface options, reverting to the Solid option. Using the Datum Options The Use Datum Curves and Use Datum Surfaces options on the AutoGEM menu give you the ability to refine your mesh, include idealizations with references on datum geometry, mesh datum geometry without having to add properties, and control whether datum geometry will be available in the independent mode. Here is an overview of how you can use these options: • Use Datum Curves — This option enables you to use datum curves as a form of mesh control. For example, you can seed your mesh by closely surrounding a problem area with datum curves to force a more granular mesh in that area. Note: As an alternative to seeding the mesh with datum curves, you can surround a problem area with a surface region. AutoGEM respects surface regions regardless of whether you set the Use Datum Curves option. • Use Datum Surfaces — This option enables you to mesh datum surfaces that have no associated properties—for example, quilts that have no shell idealizations. Additionally, if you want datum curves and surfaces that have no associated modeling entities to transfer to independent mode, you need to be sure these toggle keys are on before you use the File>Independent Mechanica command. Working with Geometry Tolerances About Geometry Tolerance If your model fails to mesh when you run AutoGEM or an analysis, you may be able to fix the problem by working with the geometry tolerance settings for your model. Adjusting the geometry tolerance settings can help you eliminate such problems as small geometry, sharp angles, and negative angles that can hamper the creation of a precise mesh. Working with geometry tolerances is particularly useful for simplifying the geometry of models with large differences in scale. In addition, geometry tolerances determine whether Mechanica merges overlapping parts in a midsurface assembly or uses automatic midsurface connections. 588 Structural and Thermal Simulation Use the AutoGEM>Geometry Tolerance command to specify the geometry tolerances that you want Mechanica to apply to your model. When you select this command, the Geometry Tolerance Settings dialog box appears, enabling you to specify several tolerance values such as Minimum Edge Length, Minimum Surface Dimension, Minimum cusp Angle, and Merge tolerance. Mechanica merges or removes geometry based on the tolerance values you specify, but the definition of the surrounding geometric entities remains unchanged. In deciding new tolerance values, you should consider the effect you want to achieve. For example, if you find that a mesh fails because some of the edges in the model are too small for AutoGEM to correctly resolve, you might increase the minimum edge length tolerance value to ensure that AutoGEM could resolve the problem edges. However, if you find that AutoGEM merges away a surface sliver that you want to see results for, you might instead reduce the minimum surface dimension, forcing AutoGEM to acknowledge the surface. When adjusting tolerance values, bear the following in mind: • • You should not enter extremely large values that may prevent the model from meshing or running an analysis. Any changes you make to the tolerance values should not diverge significantly from the defaults in place when you open the Geometry Tolerance Settings dialog box. As a general rule, you should keep such changes within 10% of the defaults displayed in the dialog box. If you enter erroneous values in any of the fields, you can reset the dialog box to the default values. • Geometry Tolerance Settings Dialog Box When you select AutoGEM>Geometry Tolerance, the Geometry Tolerance Settings dialog box appears. This dialog box includes the following items: • Minimum Edge Length — Specify the minimum length for the edges in your model. Mechanica retains all the edges whose length exceeds the minimum and merges the end points of any edge whose length is less than the minimum into a single node. The size of the node corresponds to the length of the original edge. You can specify the minimum length of an edge as an absolute or relative value. Minimum Surface Dimension — Specify the dimensions of the surfaces in your model. Mechanica retains all the surfaces whose dimensions exceed the minimum and merges each of the surfaces whose dimensions are less than the minimum into an edge whose length represents the original surface. If the resulting edge is shorter than the value that appears in the Minimum Edge Length field, Mechanica merges the surface into a vertex instead. You can specify the minimum surface dimension as an absolute or relative value. Minimum Cusp Angle — Specify the minimum angle of the cusp formed where two arcs meet or an arc meets an edge or surface. Mechanica eliminates any angle less than this value by moving the node at the end of the surfaces or edges to the nearest location that forms an acceptable angle. 589 • • Structural and Thermal Simulation - Help Topic Collection • • In effect, Mechanica shortens the surfaces or edges. You specify the minimum angle value in degrees. While Mechanica accepts negative values in this field, negative values typically result in poor geometry and meshing failures. You can eliminate the negative angles by specifying a value of zero in the Minimum Cusp Angle field. Merge Tolerance — Specify the distance below which Mechanica will merge mated or overlapping surfaces in midsurface assemblies. When determining how to treat mated or overlapping surfaces in a midsurface assembly, Mechanica uses this value as a guideline. If the mated or overlapping surface is closer than the specified distance, Mechanica merges the surfaces. If the surfaces are further apart, Mechanica creates automatic midsurface connections instead. You can specify the merge tolerance as an absolute or relative value. Default Absolute and Relative Tolerance Settings When specifying geometry tolerance settings on the Geometry Tolerance Settings dialog box, you can specify absolute values or values relative to the model, part or feature using the following options: • Relative to model — Specify the tolerance as a ratio of the geometric entity in question—edge, surface, or merge distance—to the size of the model. Mechanica determines the size of the model by measuring the diagonal length of a bounding box that surrounds the model in Cartesian space. The software measures the diagonal from the smallest XY bounding box vertex to the largest, using the WCS as the basis for the coordinate directions. In using Relative to model, take special note of how your model is oriented relative to the WCS. While you can use Relative to model for part models, this option is primarily useful for capturing an entire assembly. • Relative to part — Specify the tolerance as a ratio of the geometric entity in question—edge, surface, or merge distance—to the size of the part. As with Relative to model, Mechanica determines the size of the part by measuring the diagonal length of a bounding box, and you need to pay special attention to how the part is oriented relative to the WCS. If you use Relative to part for an assembly, Mechanica calculates the bounding box and diagonal for each part whose geometry does not meet the tolerance you specify. The software adjusts the geometry for each part relative to the diagonal for that part. In the case of Merge Tolerance, Mechanica places a single bounding box around both members of part pairs that have mated or overlapping surfaces. • Absolute — Specify the tolerance setting as an absolute value. Note: To ensure that Mechanica will produce usable geometry with the tolerance settings you specify, you should keep all tolerance settings within 10% of the default values for the dialog box. 590 Structural and Thermal Simulation FEM Meshes About FEM Meshes After you define a model in the FEM mode, you can generate a finite element mesh for it. You can mesh solids, midsurfaces, and shells separately or in any combination. You can also mesh bars and mass idealizations. Depending on how you configure your session, Mechanica treats the mesh as either a transient or retained modeling object. There are special modeling implications for both approaches, particularly if you are working with assemblies. To control, generate, and check a FEM mesh, use the Mesh menu. Before you create a mesh, this menu contains three commands: • Controls — Opens the Mesh Control dialog box. Use this dialog box to create mesh controls. Mesh controls determine the size of the elements, numbering of nodes and elements, and so on. For submodels in an assembly, you can suppress a particular mesh control type, or all mesh control types. Create — Opens the Create FEM Mesh dialog box. Use this dialog box to specify the element type and generate the mesh. Operations — Opens the MESH OPER menu if the config.pro option fem_mesh_operations is set to yes. Use this menu to import NASTRAN files. See the configuration file documentation for more information. • • After Mechanica successfully generates a mesh, the following commands also become active: • Improve — Attempts to improve the mesh. When you select Improve, the software asks you to enter the number of additional passes you want for mesh shape improvement. After you enter the number of passes, the software tries to improve the shape of solid and shell elements and redraws the model. Erase — Erases an existing mesh from memory. You can erase an individual mesh or remove all meshes in the current assembly. This command is particularly helpful if you are working with hierarchical assembly meshing, but can sometimes prove useful for other meshes as well. Note: This command only erases the mesh from memory. The Erase command does not erase saved mesh files from disk. • • Review — Opens the REVIEW MESH menu so you can review meshes, nodes, or elements. Check Elements — Opens the Element Quality Checks dialog box so you can check element quality. • You can save the mesh data to a database file for later retrieval. 591 Structural and Thermal Simulation - Help Topic Collection Transient and Retained FEM Meshes Transient and Retained Meshes Transient meshes are meshes that are present during certain modeling phases but not others. Retained meshes, once created, are present for all steps of the modeling process unless you define a modeling entity that invalidates the mesh. Transient meshes are convenient in situations where you want to experiment freely with meshing or where you plan to define all modeling entities and analyses before creating a mesh. However, if you want to re-use existing meshes or expect to work with modeling entities and analyses after you mesh, you should consider setting your session to use retained meshes. By default, Mechanica uses transient meshes for FEM mode. If you want to use retained meshing, you need to set the fem_mesh_preserve configuration option in your config.pro file before you start your session. Be aware that this also affects whether Mechanica automatically saves and retrieves your mesh. Your decision on whether to set your session for transient or retained meshing affects the simulation modeling process, determines the assembly meshing methods you can use, and involves distinct usage guidelines. You may find that you want to work with transient meshes for certain model types or during certain modeling phases, but switch to retained meshes for other model types or modeling phases. Switching between the two forms of meshing can make modeling more efficient in some situations, particularly if you determine how you want to handle your model meshes in advance. To learn more about these mesh types, their workflow, and the guidelines you should observe, see If You Use Transient Meshes and If You Use Retained Meshes. If You Use Transient Meshes If you configure your session for transient meshing, be aware that: • Mechanica assumes that, even if you stored a mesh for the model in the past, you do not necessarily want to reuse that mesh in the current session. Therefore, the software does not automatically import any existing meshes when it brings your model into FEM mode. If you decide you want to use an existing mesh, you can manually retrieve it. Mechanica only retains the mesh while you are in the Mesh menu or the Run FEM Analysis dialog box. If you leave this menu to perform modeling or analysis definition tasks before you run your analysis, the software deletes the mesh. In other words, for transient meshes, the software expects you to start a run immediately after creating a satisfactory mesh. Thus, you should define your model using the following sequence: 1. Create all modeling entities, idealizations, and properties. 2. Define all analyses. 3. Mesh the model. • 592 Structural and Thermal Simulation • • 4. Run the analysis. For assembly models, you can only perform flat meshing. Because transient mesh sessions do not call existing meshes, you cannot create a hierarchy of existing meshes within the assembly model. If you want to save a mesh in transient mesh sessions, you must use the File>Save FEM Mesh command. If you decide to configure your session for transient meshes, be sure to observe the guidelines for working with transient meshes. If You Use Retained Meshes If you configure your session for retained meshing, be aware that: • Mechanica assumes that, if you created a mesh for the model during past sessions, you want to reuse it in the current session. Therefore, the software automatically imports the mesh from the associated .fmp(a) file when it brings your model into FEM mode. Mechanica retains the model mesh throughout your session provided that you do not add modeling entities that invalidate the mesh. Thus, you are free to perform most activities in the order you please. This flexibility is handy in situations where you know you may need to update your modeling entities at various intervals. After you create the mesh, Mechanica displays the mesh model with the geometry model even if you leave the Mesh menu to perform such activities as defining modeling entities, properties, and idealizations, defining analyses, and so forth. You can control how Mechanica displays the mesh model through the View>Simulation Display command. For assembly models, you can create both flat meshes and hierarchical meshes. Mechanica saves your mesh automatically to an .fmp(a) file. • • • • If you decide to configure your session for retained meshes, be sure to observe the guidelines for working with retained meshes. Meshing Guidelines Guidelines for Transient Meshes If you configured your session for transient meshing, make sure that you have completed the following tasks prior to meshing a part or an assembly: • • • • • Simplified the part or assembly to remove features unnecessary for finite element analysis Suppressed any geometry whose only purpose is to serve as a vehicle for meshing a particular element type—for example, a solid used for placement of bar elements Assigned a material to the part or assembly Added all required loads and boundary conditions to the part or assembly Defined any idealizations 593 Structural and Thermal Simulation - Help Topic Collection • • • • • For shell-meshed features: o created the appropriate shell model by defining all surface pairs o assigned material to shell pairs and solid portions of the model o defined idealizations to represent bars, connections, weld elements, and gaps For assembly components that need to transmit loads, established connections between surfaces or edges that do not overlap or touch Defined analyses Applied the appropriate mesh controls to control the characteristics of the mesh Optionally set up any predefined criteria in the configuration file (config.pro) against which to evaluate the quality of the mesh See Troubleshooting FEM Mesh Generation for help with mesh-generation problems. Guidelines for Retained Meshes If you configured your session to use retained meshing, make sure that you have completed the following tasks prior to meshing a part or an assembly: • • • • • • • • • Simplified the part or assembly to remove features unnecessary for finite element analysis Suppressed any geometry whose only purpose is to serve as a vehicle for meshing a particular element type—for example, a solid used for placement of bar elements Added surface and volume regions Added any loads and boundary conditions that reference datum points Added any idealizations that could affect the mesh For shell-meshed features: o created the appropriate shell model by defining all surface pairs o defined idealizations to represent bars, weld elements, and gaps Suppressed all geometry features modeled as bar elements—for example, a bar element that serves as a strut Established connections between any load-transmitting surfaces or edges that do not touch or overlap For hierarchical meshing: o created all hard points required to properly connect pre-meshed assembly components o established connections between all load-transmitting surfaces or edges on pre-meshed components, whether or not the surfaces or edges touch o applied mesh controls to resolve any node and element numbering conflicts Applied the appropriate mesh controls to control the characteristics of the mesh Optionally set up any predefined criteria in the configuration file (config.pro) against which to evaluate the quality of the mesh • • See Troubleshooting FEM Mesh Generation for help with mesh-generation problems. 594 Structural and Thermal Simulation Invalidating a Mesh If you set your session to use retained meshes, Mechanica attempts to preserve the model mesh throughout the session, enabling you to define modeling entities and analyses without perturbing the mesh. However, adding or modifying certain types of modeling entities can invalidate the mesh. For example, Mechanica treats any point that has an applied load or boundary condition as a mesh node. Therefore, if you add a point load to a datum point in your model, the original mesh is no longer valid because it does not account for the newly added node. While a variety of actions can invalidate a mesh, here is a list of the main causes of mesh invalidation: • In Pro/ENGINEER: o changing model geometry o changing the way assembly components connect o removing assembly components Modifying or deleting datum features Creating, modifying, or deleting surface regions or volume regions Creating or modifying a load, boundary condition, beam, spring, gap, mass, rigid link, or weighted link such that it references a datum point or vertex that you have not already declared as a hard point mesh control. You can, however, change characteristics such as the value of a load, degrees of freedom for a constraint, and so forth without invalidating the mesh. Creating, modifying, or deleting connections—for example, end welds, perimeter welds, interfaces, and so forth Creating or deleting idealizations that affect the way the mesh generator meshes the part or assembly. You encounter cases such as this when: o creating a beam idealization on a curve or deleting one from a curve o creating or deleting a shell idealization on a quilt or surface Mechanica only includes bars and quilts in the mesh if you define them as idealizations. Therefore, adding or deleting these idealizations changes the way the mesh generator would treat the part or assembly, thus invalidating the mesh. • Adding, modifying, or deleting a mesh control other than Mesh ID Offset • • • • • If you invalidate a mesh, Mechanica informs you of the problem during modeling or meshing. If you introduce the invalidating factor at modeling time, Mechanica takes one of two actions, depending on whether the factor affects the top-level mesh or a lower-level component mesh: • • Top-level Mesh — Mechanica warns you of the problem and gives you the option of correcting the invalidating factor. If you do not correct the factor, the software immediately removes the mesh. Lower-level Component Mesh — Mechanica warns you of the problem, but leaves the mesh intact until you next mesh the component. At that time, Mechanica respects the mesh, but silently ignores the invalidating factor. 595 Structural and Thermal Simulation - Help Topic Collection Troubleshooting FEM Mesh Generation The following may prevent mesh generation in part mode: • Imperfections in model geometry — Use Analysis>ModelCHECK>GeomIntegrityCHECK to investigate the features flagged by the software. Resolve any errors or warnings before meshing the model. Insufficient data — When the software is unable to mesh, the mesh generator may prompt you to apply more mesh controls to specified geometry. If the error message appears again after applying the appropriate mesh controls, you should evaluate the model for the presence of invalid geometry. Inappropriate mesh controls — If the software is unable to generate a mesh, your model may include mesh controls that are inappropriate to the geometry. You can experiment with adding, changing, or removing mesh controls to determine which mesh control causes the problem. You may also be able to isolate problem geometry by suppressing some features. • • When you attempt to generate a mesh in assembly mode and the system gives you an error message, also consider the following: • • Interference — The mesh generator cannot mesh assemblies that have interference. Use the Analysis>Model Analysis command and resulting Model Analysis dialog box to check for global interference in your model. Minimum element size — A Minimum Element Size mesh control set for one part may not be appropriate for the entire assembly. If this is the case, remove all Minimum Element Size mesh controls assigned to the parts and try to mesh the assembly again. If you are still unsuccessful, remove all Maximum Element Size mesh controls as well. Note: If you are working at the assembly level, you can often use Ignored Mesh Control on the Mesh Control dialog box instead of actually removing the mesh controls from lower-level components. • Design flaws — Design flaws in model geometry—such as misalignment, overlapping geometry, and other imperfections in part geometry—can often prevent the mesh generator from meshing assemblies even if it could successfully mesh constituent parts in part mode. You may need to temporarily suppress some components and attempt to mesh the assembly so you can determine which parts cause the problem. After you find the problem parts, try to eliminate imperfections. Curved surfaces — Some assemblies contain curved surfaces on the components that are close but not touching—for example, two concentric cylinders of similar but not equal diameters. In this case, place a local maximum, equal to the clearance, on the two opposing curved surfaces. Accuracy values — Accuracy values of the parts in the assembly must be compatible. It is better for large models to have accuracy values comparable to smaller models. If you have problems generating a mesh for an assembly, you can run a report to check the accuracy values of each assembly • • 596 Structural and Thermal Simulation component. This report shows you which components have tolerance values that are too high so you can adjust them. When the software fails to generate a solid mesh, check the available memory. If you receive a memory error message, you can increase the amount of memory that Pro/ENGINEER uses by modifying the sim_max_memory_usage configuration file preference. Assembly Meshing Assembly Meshing Methods To ensure that the meshing paradigm most closely meets your engineering needs and design process, Mechanica provides two methods for meshing assemblies—flat meshing and hierarchical meshing. These methods have distinct modeling assumptions, have different implications for the overall modeling flow, and address different product development requirements. Here is an overview of the two methods: • Flat Meshing — In flat meshing, Mechanica approaches an assembly as though its components have no individual mesh history. The mesh generator creates a single, cohesive mesh model for the entire assembly, developing consistent meshes across all mated surfaces, all mated edges, and all subcomponents that you explicitly connected. Due to its relative ease of use, flat meshing is the preferred meshing method for most assemblies. Consider flat meshing when: o o individual component meshes created in the past are unimportant to the current assembly mesh you want to minimize the number of explicit component connections in the assembly For details on flat meshing and its implications for your model, see Flat Meshing. • Hierarchical Meshing — In hierarchical meshing, Mechanica assumes that some or all of the assembly components have meshes important to the model as a whole. The mesh generator creates a top-level mesh model for the assembly that uses component meshes wherever possible. It does this by: o preserving all complete and valid pre-existing component meshes o adding its own consistent top-level mesh to any unmeshed components, partially meshed components, and load path connections Hierarchical meshing is a specialized form of meshing primarily suited for large, complex assemblies. Consider hierarchical meshing if: o you want to leverage the meshes already completed for individual components 597 Structural and Thermal Simulation - Help Topic Collection o o your design process uses separate teams to mesh individual assembly components and the teams update these meshes at different times. In this case, hierarchical meshing gives you the ability to choose which mesh updates you want to incorporate, and which ones you want to ignore. you want to maintain one mesh type for some components while establishing a different mesh type for the rest of the assembly—for example, if you want a triangular shell mesh for a set of aircraft flaps and a quadrilateral shell mesh for the wing For details on hierarchical meshing, guidelines for its use, and implications for your model, see Hierarchical Meshing. After you decide which type of meshing you want to use, you are likely to develop a workflow that matches the steps required for the mesh. However, even if you begin your work using one type of meshing, you can switch to the other type freely. You simply need to make sure that you have fulfilled any mesh prerequisites. Be aware that, while you can create flat meshes regardless of whether you use retained or transient meshes, you can create hierarchical meshes only if you configure your session to use retained meshes. Flat Meshing For flat meshing, Mechanica assumes your design goal is a one-level, unified mesh for your model. This means that the session model should include no individual component meshes. The easiest way to assure this is to work with transient meshes. However, if you configured your session to use retained meshes instead, you can still create a flat mesh by erasing component meshes on your screen before you create your top-level assembly mesh. How realistically you define your model determines the nature of your mesh and, consequently, your solution quality. For example, if you do not establish which components of an assembly transmit a load, your solution will not mirror the behavior of the assembly. Therefore, you should be sure your assembly includes connections for any load paths occurring between components that do not have mated surfaces or overlapping edges. Note: If your default connection type is not Bonded, you must usually establish explicit connections for all mated components in the load path. When you mesh your model, the mesh generator approaches your model as a single unit, creating coincident meshes across mated surfaces and overlapping edges. The mesh includes any nodes established by hard points, loads, boundary conditions, idealizations, connections, or mesh controls. The mesh generator also observes the mesh type you select. After you create a flat mesh, you can perform analyses using any supported solver. You can run the analysis online or offline. You can also view the results of your analysis within Mechanica. 598 Structural and Thermal Simulation Hierarchical Meshing For hierarchical meshing, Mechanica assumes your design goal is a mesh model that contains both the top-level assembly mesh and pre-existing component meshes for one or more individual components. For convenience, this discussion refers to components with pre-existing meshes as pre-meshed components. A pre-meshed component can be an individual part or a subassembly. Development of a hierarchical mesh may involve gathering meshes from multiple designers, deciding which meshes to use or omit, and so forth. To ensure that you complete all the required modeling phases, you may want to use a specific workflow when developing a hierarchical mesh. Because you can only use hierarchical meshing if you configure your session to use retained meshes, be sure to set the fem_mesh_preserve config.pro option before starting Pro/ENGINEER. With this option set, Mechanica checks the current directory when you open your model in FEM mode. If it finds any existing component meshes, it brings those meshes into the session. Thus, as your model opens, you see meshes on pre-meshed components. Components that have no pre-existing meshes display geometry only. As with flat meshing, you should add connections to ensure that loads transmit between unmeshed components that have no mated surfaces or overlapping edges. You must also explicitly connect any pre-meshed component to the rest of the assembly. As a prerequisite for this, the component must have hard points where you want the connections before you generate the component-level mesh. If you do not use hard points, Mechanica disregards the connection when you create the toplevel assembly mesh. The way the mesh generator combines individual meshes to form a hierarchical mesh can be complex. To learn how Mechanica builds hierarchical meshes and handles premeshed components, see Understanding Hierarchical Meshes. After you create a hierarchical mesh, you can run your model online or output your model for analysis with your solver. If you choose the latter method, the output is such that it will allow the solver to handle the assembly mesh hierarchically. However, the exact arrangement of the output file is slightly different for NASTRAN than it is for the other solvers. After your run is complete, you can view the results of your analysis within Mechanica. Hierarchical Meshing Workflow There are several ways to approach working with hierarchical meshes, some more efficient than others. The workflow you develop depends on the design process used by your company, the nature of the assembly, and other factors beyond the scope of this discussion. However, to give you a general idea of one method, here is a sample workflow appropriate for large assemblies. As you review this, bear in mind that you do not 599 Structural and Thermal Simulation - Help Topic Collection necessarily need to perform the steps in this order. You can get the same results using a different sequence, and some steps may not be required for all situations. For example, in this workflow, the designers complete all work on the individual components before the system integrator starts working on the top-level assembly. However, you could easily use a workflow where the system integrator sets up all connections for the top-level assembly before the designers work on the component meshes. The latter workflow is especially efficient for complex component-level meshes because the hard point locations are identified very early in the process. • Determine which components in the top-level assembly will be premeshed at the part or subassembly level. At the part or subassembly level, place hard points on these components so you can create loadtransmitting connections in the toplevel assembly. Use the Mesh Numbering mesh controls to allocate node, element, and local mesh ID ranges to each component so you can avoid potential conflicts when you later bring the components into the toplevel assembly. • Prepare the individual components • • Mesh the individual components At the part or subassembly level, create meshes for any component that will appear as pre-meshed in the top-level assembly. • Prepare the top-level assembly • Add connections to the top-level assembly: o Connect pre-meshed components to the rest of the assembly using beams, springs, gaps, rigid links, or weighted links. o Where necessary, connect unmeshed top-level assembly components with beams, springs, or connections. Turn off any component-level mesh controls that you do not want the mesh generator to use. 600 Structural and Thermal Simulation • Add assembly-level mesh controls where needed. Use the Mesh Numbering and Mesh ID Offset mesh controls to resolve any ID conflicts in the top-level assembly. • Mesh the top-level assembly • Generate the assembly mesh. The resulting mesh includes both the toplevel mesh and the individual meshes of any pre-meshed components. If the mesh generator notifies you of any problems, correct them and remesh the assembly. Understanding Hierarchical Meshes A hierarchical mesh is a composite of the top-level mesh (the mesh of the current assembly) and any component-level meshes (the pre-existing component meshes in that assembly). When it creates a hierarchical mesh, Mechanica traverses the assembly hierarchy from top to bottom looking for pre-meshed components. Each time it finds one, it evaluates the component-level mesh and determines whether the mesh is: • • Complete — A component has its own mesh in which all subcomponents have a mesh. Partial — A subassembly has its own mesh, but not all its subcomponents have meshes. This can occur if you mesh a subassembly, add a new unmeshed component to that subassembly, and then do not remesh the subassembly as a whole. Inherited — A component mesh is part of a larger component mesh. For example, assume that pre-meshed part a is included in pre-meshed subassembly b, which, in turn, is part of top-level assembly c. In this case, subassembly b and part a both contribute inherited meshes to assembly c. Part a also contributes an inherited mesh to subassembly b. • Here is how the mesh generator treats each situation: Component Mesh State Unmeshed Action Includes the component in the list of components to be meshed. Excludes the component from the list of components to be meshed. Displays a message asking if you want to remove the current mesh. If so, the mesh generator adds 601 Complete mesh Partial mesh Structural and Thermal Simulation - Help Topic Collection Component Mesh State Action the component to the list of components to be meshed. Inherited mesh Excludes the component from the list of components to be meshed. After it has prepared the list of components that it needs to mesh, the mesh generator creates the top-level mesh. The resulting mesh model contains the toplevel mesh, which includes meshes for all connections and unmeshed components. The mesh model also contains any complete or inherited component-level meshes. In creating the mesh, the software respects all properly established connections between subcomponents, ensuring that the solver will be able to correctly recognize the assembly load paths. Here is how the mesh generator treats connections: • • Creates consistent meshes for connected components. These components can transmit loads. Does not create consistent meshes for components that it considers disconnected. These components remain in place and are part of the overall mesh, but cannot participate in the load path. As it proceeds, the mesh generator checks for any situations that invalidate the mesh or cause unacceptable mesh inconsistencies. The mesh generator either ignores the factor causing the problem or removes the mesh. The mesh generator also checks for any node, element, or local mesh entity ID conflicts. If it finds any, it warns you of the situation, providing a list of nodes, elements, and local mesh entities that have numbering conflicts. To resolve this conflict, use the Mesh Numbering or Mesh ID Offset mesh control, as appropriate. When you output the model for use with the NASTRAN solver, Mechanica creates a single file for the assembly. This file lists all the meshes in the model, starting with the lowest level and working upward. It places the properties, materials, and coordinate system records in the lower mesh structures, enabling you to separate individual meshes from the whole and run these separately. For other solvers, the file lists all model meshes, but does not arrange them hierarchically. In this case, Mechanica arranges the file so that all nodes in the assembly are in one section of the file, all elements are in another, all materials in another, and so on. When it works with the file, the solver recreates the hierarchy using information from each of these sections. To see an example of how the mesh generator processes a hierarchical mesh, see Example: Hierarchical Mesh Generation. 602 Structural and Thermal Simulation Example: Hierarchical Mesh Generation Here is an example of a top-level assembly containing three pre-meshed subassemblies and a pre-meshed part. In this example, different colors represent different individual component meshes. Here, part f is a pre-meshed part, subassembly a has a complete mesh, and subassembly d has a partial mesh. Subassembly b has a complete mesh that contains an inherited mesh—the second instance of part f. Subassembly b and subassembly c both include parts d and e. These parts have no part-level mesh, but subassembly b's mesh incorporates both parts. When it meshes the top-level assembly, the mesh generator preserves the existing meshes for part f, subassembly a, and subassembly b. However, as subassembly d has a partial mesh, the mesh generator asks whether you want to remove subassembly d's mesh. 603 Structural and Thermal Simulation - Help Topic Collection If you do, the mesh generator creates the top-level mesh. Here is the result: Connections in Assembly Meshing Creating Load Paths for FEM Meshing Before generating an assembly mesh model, you need to define where loads and displacements transmit through the various assembly components. You accomplish this by setting up load paths—assembly-level idealizations that establish a loadtransmitting connection between two components. When the mesh generator encounters these idealizations, it creates nodes where the idealizations contact each of the components. Thus, at the location of the load paths, the component meshes are said to be consistent about the nodes. This consistency, along with the idealizations themselves, enables loads to pass through the assembly. The way you establish load paths varies depending on whether you are working with flat meshes or hierarchical meshes. However, the underlying issue in both cases is whether Mechanica recognizes a mesh connection between components. In some cases, the mesh generator recognizes the connection automatically and, in others, you must establish the connection yourself. To learn about establishing load paths for the two mesh types, see Load Paths for Flat Meshes and Load Paths for Hierarchical Meshes. 604 Structural and Thermal Simulation Load Paths for Flat Meshes Mechanica establishes or recognizes a load path for flat meshes under two conditions: • Components with Mated Surfaces or Edges — In this case, the software recognizes that the geometries are fully connected at the surfaces or edges. When the mesh generator finds this type of geometric connection, it determines the default connection type for the assembly. It then automatically assigns that connection type to the geometrically connected area. Note: Use the Properties>Default Interface Type command to define the default connection type. The default type is normally Bonded, but you can reset it to Free. As the mesh generator meshes the assembly, it creates matching nodes on the contacting geometries. For Bonded default connections, these actions automatically establish load paths at each of the nodes. • Unmated Geometry — In this case, the software does not recognize any geometric connection and you must establish the load paths manually by creating assembly-level beam, spring, or connection idealizations to link the opposing surfaces, edges, or points of the components. When you create a connection of this kind, the mesh generator treats the datum points associated with the idealizations as nodes that enable it to generate a consistent mesh. Because these connections serve as load paths, you should determine the connection type and distribution based on the nature of the load and its distribution. Load Paths for Hierarchical Meshes The way that you establish load paths in hierarchical meshes depends on whether you are working with unmeshed components or pre-meshed components: • • Unmeshed Components — Between a group of unmeshed components, Mechanica recognizes load paths just as it would for a flat mesh. Pre-meshed Components — Between a group of components where at least one component has a pre-existing mesh, Mechanica recognizes load paths only if you create assembly-level beam, spring, or gap idealizations or place rigid or weighted links to connect the components. As a prerequisite for placing the beam, spring, gap, rigid link, or weighted link, the pre-meshed component must contain hard points on any meshed pieces of model geometry you want to connect. You can create the assemblylevel beam, spring, rigid link, or weighted link at any time using datum points on your model. But, before you generate the component-level mesh, you must assign a hard point mesh control to the datum point. Otherwise, 605 Structural and Thermal Simulation - Help Topic Collection Mechanica does not respect the beam or spring when you mesh the top-level assembly. To understand how you create this type of connection more fully, you can review an example. Controlling a FEM Mesh Use the Mesh>Control command to define the characteristics of a mesh. When you select the Control command, the Mesh Control dialog box appears. This dialog box enables you to define mesh characteristics by setting mesh controls. Mesh controls specify the minimum or maximum size of the elements, the distribution of nodes along edges, hard points and hard curves, mesh ID numbering, mesh ID offsets, and the displacement coordinate system. For assembly models, you can suppress a single mesh control type, or all types, on selected parts or subassemblies by selecting Ignored Mesh Control on the Mesh Control dialog box. This gives you the flexibility to use the same part or subassembly in different assemblies using different mesh control settings. If two parts or subassemblies in an assembly have conflicting numbering of nodes, elements, local mesh entities, or hard points, you can correct the problem by assigning the Mesh ID Offset mesh control. These items appear on the Mesh Control dialog box: • Type — You can specify one of the following mesh control types: o Maximum Element Size o Minimum Element Size o Edge Distribution o Hard Point o Hard Curve o Mesh Numbering o Displacement Coordinate System o Ignored Mesh Control (available only for assemblies) o Mesh ID Offset (available only for assemblies) o Shell Element Direction References area — Depending on the mesh control type you specify in the Type field, the active fields in the References area change. For information on this area, use the links in the list above to learn about the References area for each mesh control type. • When you create a mesh control, the software adds the appropriate icon(s) to your model. For more information, see Mesh Control Icons. After a mesh control exists on your model, you can redefine or delete it by rightclicking the mesh control icon in the Model Tree. You can also redefine a mesh control by double-clicking the icon on your model. 606 Structural and Thermal Simulation Maximum and Minimum Element Size (FEM mode) Use the Maximum Element Size and Minimum Element Size options on the Mesh Control dialog box to control the size of the elements that the mesh generator creates. If you select Maximum Element Size or Minimum Element Size, specify the following information: • References — Specify the reference type and select the appropriate geometry. If you already selected the valid geometric references before entering the dialog box, your selections appear next to the selector arrow when the dialog box opens. Otherwise, use the selector arrow and the regular selection methods to choose one of the following: o points (maximum only) o edges (maximum only)/curves o surfaces o components Maximum Element Size or Minimum Element Size — Specify the maximum or minimum element size. • If you enter an unusually small value for the maximum element size, the software might create an extremely large number of elements. To warn you of this situation, the mesh generator compares the specified size of the element with the volume of the meshed part. If the specified element size is very small, the software displays a message. If it cannot generate a mesh with elements that small, the software overrides the value specified in the mesh control with the smallest value it considers acceptable and displays a warning message. The mesh generator only respects the Maximum Element Size and Minimum Element Size mesh controls if you apply them to unmeshed components. If a component has a mesh, the mesh generator silently ignores these mesh controls. Hard Points and Curves (FEM mode) Use the Hard Point or Hard Curve option on the Mesh Control dialog box to define a datum point or curve as a hard point or curve. If you define a point or curve this way, the mesh generator treats it as part of the mesh, creating nodes and defining elements accordingly. If you select either of these options, specify the following information: • References — Use the selector arrow to specify the datum point or curve for the mesh generator to use to place an element node or nodes. If you already selected the valid geometry before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. Node ID — Specify the node ID (Hard Point only). This option is available only when you select a single point. When the mesh is complete, the number 607 • Structural and Thermal Simulation - Help Topic Collection replaces the node ID for the selected hard point. You can define a hard point without specifying a node ID. For hierarchical meshes, make sure your model includes part-level hard points wherever you want to create connections for pre-meshed assembly components. The mesh generator only respects the Hard Point and Hard Curve mesh controls if you apply them to unmeshed components. If a component has a mesh, the mesh generator silently ignores these mesh controls. You can create notes associated with specific hard points. The notes you create transfer to the NASTRAN or ANSYS output deck as comments. Edge Distribution (FEM mode) Use the Edge Distribution option on the Mesh Control dialog box to specify the number of nodes you want the mesh generator to create on one or more edges or curves in your model. This type of mesh control affects shells, bars, and solid meshes. If you select Edge Distribution, you can specify the following: • References — Use the selector arrow to specify the appropriate curve or edge. If you already selected the valid geometry before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. To flip the direction of node distribution on the specified edge or curve, select the edge or curve again. The arrow on the specified edge displays the direction. Mechanica indicates that the distribution direction is flipped by adding the word reversed to the References field. • • Number of Nodes — Specify the minimum number of nodes you want distributed along the selected edge or curve. Mechanica may create additional nodes if the nearby geometry is complex. First/Last Nodal Interval Ratio — Specify the ratio of the first interval on the edge or curve to the last interval on the edge or curve. For example, if you enter 3 as the ratio, the last interval will be 3 times the length of the first interval. The intermediate nodes will be spaced in graduating intervals proportionate to the ratio. If you enter a ratio of 1, all intervals will be equal. Prevent Additional Nodes — Check this option if you want the number in the Number Of Nodes text box to be a precise number. Mechanica will stop the mesh creation if it requires more nodes than the number you set. When the meshing fails, Mechanica highlights the edges requiring additional nodes. • The mesh generator only respects the Edge Distribution mesh control if you apply it to unmeshed components. If a component has a mesh, the mesh generator silently ignores the mesh control. 608 Structural and Thermal Simulation Displacement Coordinate System (FEM mode) Use the Displacement Coordinate System option on the Mesh Control dialog box to specify the coordinate system that the software uses when displaying results for nodes associated with points, edges, curves, or surfaces. When Mechanica displays analysis results, the results for the nodes that have this type of mesh control are relative to the coordinate system you specify. If you select Displacement Coordinate System, specify the following: • References — Specify the reference type and select the appropriate geometry. If you already selected the valid geometric references before entering the dialog box, your selections appear next to the selector arrow when the dialog box opens. Otherwise, use the selector arrow and the regular selection methods to choose one of the following: o points o edges/curves o surfaces Coordinate System — Select a coordinate system. If you want to apply loads and constraints to these nodes, make sure that you associate the loads and constraints with the same coordinate system. • The geometric reference that you select for a displacement coordinate system may also be part of the definition for other Mechanica entities, such as constraints, rigid links, and weighted links. If you defined the constraint, rigid link, or weighted link with a coordinate system that is not identical to the displacement coordinate system, a conflict may arise. In most cases where there are conflicting coordinate systems, the software uses the most recent coordinate system. However, if you output to the NASTRAN solver, the software tries to resolve the conflict using geometric and modeling precedence rules. If the software cannot resolve the conflicts, a message box appears when you run the analysis with an error message about the coordinate system conflict, and the output process stops. The mesh generator only respects the Displacement Coordinate System mesh control if you apply it to unmeshed components. If a component has a mesh, the mesh generator silently ignores the mesh control. Mesh Numbering (FEM mode) Use the Mesh Numbering options on the Mesh Control dialog box to set a different node and element ID range for a component. In addition, this mesh control sets a different ID range for entities local to the mesh. Examples of such entities include shell properties, beam properties, gap properties, loads, constraints, coordinate systems, materials, and so forth. 609 Structural and Thermal Simulation - Help Topic Collection These mesh controls are useful in two situations: • To resolve conflicts between top-level assembly mesh IDs and component mesh IDs. When Mechanica numbers nodes, elements, and local mesh entities for top-level assembly components, it always starts with 1 regardless of the numbering of any pre-meshed components. You can use Mesh Numbering mesh controls to set the top-level assembly mesh ID range to a number higher than that of any of the pre-meshed components. To resolve conflicts that occur if two pre-meshed components have node, element, and local mesh entity IDs that partially or wholly overlap. However, you cannot use this technique to resolve ID conflicts between two instances of a pre-meshed component within the same assembly. In this case, you need to use the Mesh ID Offset mesh control applied from the top-level assembly. • If you select Mesh Numbering, specify the following: • • • First ID — Specify the first ID for the nodes, elements, and local mesh entities. Increment — Specify the ID increment for the nodes, elements, and local mesh entities. Last ID — Specify the last ID for the nodes, elements, and local mesh entities. You can leave this item blank. If meshing generates a mesh ID that is higher than the value you specify for Last ID, the software displays a message warning that there are conflicts in the mesh and stops the mesh. You can resolve this problem by increasing the Last ID value. For assemblies, the software defines these IDs for the top-level model only. If you switch to part mode to resolve an ID conflict within the assembly, be sure the new range for the part does not conflict with the range of another assembly component not previously in conflict. The mesh generator only respects Mesh Number mesh controls if you apply them to unmeshed components. If a component has a mesh, the mesh generator silently ignores these mesh controls. Mesh ID Offset (FEM mode) Use the Mesh ID Offset option on the Mesh Control dialog box to add an offset to the node IDs and element IDs for a component. In addition, this mesh control adds an offset to the IDs of entities local to the mesh. Examples of such entities include shell properties, beam properties, gap properties, loads, constraints, coordinate systems, materials, and so forth. By adding an offset, you can avoid ID conflicts between two instances of the same component in an assembly. This mesh control is available only if you are working in assembly mode, and you should apply Mesh ID Offset only to pre-meshed components. 610 Structural and Thermal Simulation As mentioned, this mesh control is primarily useful if you use a component more than once in a hierarchical mesh. In this case, both instances of the component would normally have the same node IDs, element IDs, and local mesh entity IDs, which would cause a conflict when you mesh the top-level assembly. Applying an offset to the mesh IDs when you work in the top-level assembly eliminates this problem. You can also use this technique when two individual component-level meshes have mesh IDs that partially or wholly overlap, but you may find the Mesh Numbering mesh controls easier to use in this situation. If you select Mesh ID Offset, specify the following: • References — Use the selector arrow and the regular selection methods to specify the appropriate geometry. If you already selected the valid geometric references before entering the dialog box, your selections appear next to the selector arrow when the dialog box appears. ID Offset Value — Specify a positive integer value to be added to the IDs of each node, element, and local mesh entity. • Before choosing offset values, be sure to check that the offset does not move the new mesh ID range into the range of a component not previously in conflict. Shell Element Direction (FEM mode) Use the Shell Element Direction option on the Mesh Control dialog box to specify a coordinate system and directional component that you want the mesh generator to use when determining the node order for shell elements. This type of mesh control affects only shell meshes, not solid meshes. 611 Structural and Thermal Simulation - Help Topic Collection Without this mesh control, the mesh generator determines the coordinate direction of each element based on how it distributes the node numbers for each element. If you create a Shell Element Direction mesh control, the mesh generator arranges the node numbers in the order that makes the shell elements X direction align as closely as possible with the coordinate system direction you select. The result is a consistent node numbering scheme and a shell mesh whose elements share a common direction, as shown in the following example using quadrilateral elements: If you select the Shell Element Direction option, you can specify the following: • Surfaces — Use the selector arrow to specify the appropriate surface. If you select a surface that, at mesh time, does not have a shell idealization or is not part of a shell pair, Mechanica will ignore the Shell Element Direction mesh control. Coordinate System Direction area — Use the selector arrow to specify the reference coordinate system. After you select the coordinate system that you want Mechanica to use as the basis for node numbering, you can select the axis that you want the software to use to determine shell element direction. For Cartesian coordinate systems, you can select X, Y, or Z. For cylindrical coordinate systems, you can select R, , or Z, while you can select R, , or for spherical coordinate systems. If you select a coordinate direction that is perpendicular to any shell elements or within approximately 5 of perpendicular, Mechanica warns you at mesh time, highlights the problem elements, and does not reorder these element nodes. In most cases, you should apply the Shell Element Direction mesh control before meshing the model. For hierarchical meshes, the mesh generator only respects this mesh control if you apply it to unmeshed components. If a component has a mesh, the mesh generator silently ignores any Shell Element Direction mesh control you place on a previously meshed component. Note that you can also create a shell mesh with aligned element directions by assigning material orientations as part of defining an advanced shell idealization. • 612 Structural and Thermal Simulation Ignored Mesh Control (FEM mode) Use the Ignored Mesh Control option on the Mesh Control dialog box to indicate a component-level mesh control that you want the mesh generator to ignore when you mesh the top-level assembly. This control is particularly handy for parts and subassemblies shared by multiple higher-level assemblies that use different meshing paradigms. Ignored Mesh Control is available only if you are working in assembly mode. You can apply this mesh control to assemblies even if you have not defined any mesh controls at the component level. This ensures that mesh controls added later to individual assembly components will not affect how the mesh generator handles the top-level assembly. However, for hierarchical meshes, if you apply Ignored Mesh Control to a premeshed component, you should ensure that the component mesh control you want to ignore is not one that governs the component mesh as it currently exists. If you apply Ignored Mesh Control to a mesh control that governs the component mesh, the mesh generator respects the original component mesh, including the mesh control you want it to ignore. If you select Ignored Mesh Control, specify the following: • • References — Use the selector arrow to specify the appropriate part or subassembly. You cannot select the top-level assembly. Type of Mesh Control to Ignore — Select one of the following mesh control types to ignore: o Maximum Element Size o Minimum Element Size o Edge Distribution o Hard Point o Hard Curve o Displacement Coordinate System o All Types of Mesh Control o Shell Element Direction o Minimum Edge Length You cannot ignore Mesh Numbering or Mesh ID Offset. Mesh Control Icons (FEM mode) When you create a mesh control constraint, the software places the appropriate icons on your model and displays a short description. You can control the visibility of these icons on the Settings tab on the Simulation Display dialog box. 613 Structural and Thermal Simulation - Help Topic Collection The following table summarizes these icons and descriptions: Constraint Maximum Element Size Icon A circle Text Description MaxSize:n.n where n.n is the size of the element Minimum Element Size A circle MinSize:n.n where n.n is the size of the element Edge Distribution Filled-in circles to represent node locations nnn N; rrr R where nnn is the number of nodes and rrr is the L1/L2 ratio Hard Pt Hard Curve Mesh IDs: n1 n2 n3 where n1 is the first ID, n2 is the increment, and n3 is the last ID Displacement Coordinate System Ignored Mesh Control Mesh ID Offset No icon DisplCS coordinate system name Hard Point Hard Curve Mesh Numbering x xxx No icon No icon None No icon ID Off: n where n is the mesh ID offset Shell Element Direction A two-axis coordinate system to represent X and Y directions ShellCSnnn where nnn is the coordinate system you selected when you created the mesh control If you do not see the text description for the mesh control, select View>Simulation Display and make sure that Display Names is selected on the Settings tab. Creating a FEM Mesh Use the Mesh>Create command to generate a mesh for your model. When you select this command, the Create FEM Mesh dialog box appears. This dialog box enables you to indicate the element types Mechanica will use to generate the mesh. 614 Structural and Thermal Simulation The Create FEM Mesh dialog box includes two areas—the Mesh Type area and the Shell Element Type area. The Shell Element Type area is present depending on the mesh type you select and the idealizations present in the model. The Mesh Type area provides a option list with the following items: • Solid — Generates a solid mesh for your model. The meshing process creates an optimal model of the solid volume of the meshed model with a network of three-dimensional tetrahedral elements. The resulting mesh includes: o tetrahedral solid elements for all solid chunks in your model o shell elements for any simple or advanced shell idealizations that you created for quilt surfaces o elements for any beam, spring, gap, mass, rigid link, or weighted link idealizations When you select the Solid option, the Shell Element Type area is unavailable unless your model contains appropriately defined shell idealizations. • Midsurface — Generates a shell mesh of triangular or quadrilateral elements for shell idealizations defined through shell pairs. The resulting mesh includes: o shell elements at the midsurface of your model o shell elements for any simple or advanced shell idealizations that you created for quilt surfaces o elements for any beam, spring, gap, mass, rigid link, or weighted link idealizations Solid/Midsurface — Generates a mixed mesh of solid and shell elements on your model. The resulting mesh includes: o tetrahedral solid elements for all solid chunks in your model o shell elements at the midsurface of your model o shell elements for any simple or advanced shell idealizations that you created for quilt surfaces o elements for any beam, spring, gap, mass, rigid link, or weighted link idealizations Shell — Generates a shell mesh of triangular or quadrilateral elements on a model's quilt surfaces if you defined simple or advanced shell idealizations on those surfaces. The resulting mesh includes: o shell elements for any simple or advanced shell idealizations that you created for quilt surfaces o elements for any beam, spring, gap, mass, rigid link, or weighted link idealizations Boundary — Generates a shell mesh of triangular or quadrilateral elements on your model's exterior surfaces. The resulting mesh includes: o shell elements for any simple or advanced shell idealizations that you created for quilt surfaces o elements for any beam, spring, gap, mass, rigid link, or weighted link idealizations Bar — Generates a mesh on one-dimensional idealizations such as beams, springs, gaps, masses, rigid links, or weighted links. • • • • 615 Structural and Thermal Simulation - Help Topic Collection If the mesh type you select provides for shell elements, the Create FEM Mesh dialog box includes the Shell Element Type area that you use to specify how Mechanica constructs the shell mesh portion of your model. The Shell Element Type area provides a option list with the following items: • • Triangles — Specifies that the shell mesh consists of triangular elements. Quads — Specifies that the shell mesh consists of quadrilateral elements. If you select this method, Mechanica applies quadrilateral elements to as much of the model as it can. In areas where it cannot use quadrilateral elements due to the model geometry, Mechanica uses triangular elements as fillers. After selecting any of these options, click Start. The mesh generator then creates and optimizes the mesh. To terminate mesh generation, click the stop sign displayed in the lower right corner of the Pro/ENGINEER window. When the mesh is complete, Mechanica displays the meshed model and the Element Quality Checks dialog box. What the model looks like depends on the display style. The mesh generator automatically produces a mesh that satisfies all applied mesh controls and ensures that each constrained or loaded datum point becomes a node in the resulting mesh. To Create a FEM Mesh Before starting this procedure, you may want to set various mesh controls for your model to more closely define the characteristics of your mesh. 1. Select Mesh>Create or click . The Create FEM Mesh dialog box appears. 2. Select one of the following from the Mesh Type option list, as available for your model: o Solid o Midsurface o Solid/Midsurface o Shell o Boundary o Bar 3. If you selected Midsurface, Mixed, Shell, or Boundary as the mesh type, select one of these element types from the Shell Element Type option list: o Triangles o Quads Note that you can also select these element types if you choose Solid as the mesh type for a model that contains both solid portions and simple or advanced shell idealizations. 4. Click Start. 616 Structural and Thermal Simulation Mechanica meshes your model, displays the mesh, and opens the Element Quality Checks dialog box. You can use this dialog box to check the quality of your mesh. If Mechanica displays any error messages before it meshes your model, see Troubleshooting FEM Mesh Generation. 5. When you finish your initial review of your model, click Close. 6. If you do not have the fem_mesh_preserve config.pro option set and want to save your mesh, click File>Save FEM Mesh and enter the name of the file in which you want the software to store the meshed model. Shell Mesh Shell Mesh (FEM mode) The software can mesh shell or quilt surfaces by using two-dimensional triangular or quadrilateral elements. There are three methods of shell meshing: • • Midsurface — Sandwiches features between previously defined surface pairs. The software then creates a shell model by compressing the surfaces to a specified surface, and applies the shell mesh to this compressed surface. Shell — Applies a triangular or quadrilateral shell mesh to quilt surfaces previously defined as simple or advanced shell idealizations. You can use this method on its own or with solid models to form a mixed mesh, provided the solid model has quilts defined as shell idealizations. Boundary — Applies the shell mesh directly to the part surfaces. The interior of the part has no mesh. • The Shell Element Type option list includes two element types you can use to shellmesh models—triangles and quadrilaterals. • • Triangles — Meshes the surfaces with triangles. Quads — Meshes the surfaces with quadrilaterals. In this case, triangles appear only in areas where the mesh generator could not use quadrilaterals. Note that, for models that contain simple or advanced shell idealizations as well as midsurface or boundary shells, you can define only one element type. Mechanica applies this element type throughout the model. An example of shell meshing shows the results of meshing the model with different types of elements. You can also create a partial shell mesh, where the software meshes all paired surfaces, but ignores the unpaired ones. 617 Structural and Thermal Simulation - Help Topic Collection Example: Shell Mesh Using Triangles and Quadrilaterals Creating a Partial Shell Mesh You can partially shell-mesh a FEM model. This enables you to generate the mesh on the portion of the model where surface pairs are properly defined, ignoring unpaired surfaces. See Strategy: Working with Partial Shell Meshes. The software distinguishes two types of problem surfaces: • • Unpaired surfaces — Surfaces omitted in the process of defining shell pairs. Unopposed surfaces — Surfaces that can occur when geometries of paired surfaces are not exactly the same. As a result, leftover surfaces may appear in the shell model. When you create a partial shell mesh, you can either use the unopposed surfaces in the shell model or ignore them, depending on how you set the UseUnopposed option. To eliminate unopposed surfaces to generate a full mesh, use one of the methods recommended for pairing unopposed surfaces. When you attempt to compress the model and the system detects unpaired surfaces, the following events occur: • The system highlights the unpaired surfaces and asks you if you want to mesh only paired surfaces. o To halt the process, click the stop sign displayed in the lower right corner of the Pro/ENGINEER window. o To continue, proceed to the next step. 618 Structural and Thermal Simulation • • You can visually investigate the shell model using options in the COMPRES MDL Menu. To mesh only the paired surfaces, select Midsurface from the Mesh Type option list on the Create FEM Mesh dialog box, click Start and, when the CONT MESH menu appears, select the Paired Only command. Strategy: Working with Partial Shell Meshes Use these strategies to help you create a partial shell mesh. • • To select the Paired Only option automatically, set the fem_ignore_unpaired config.pro option to yes. To have the system remove the unopposed surfaces by default, set the fem_remove_unopposed config.pro option to yes. If you set this configuration option, the software turns off the UseUnopposed option and removes the unopposed surfaces during shell mesh creation. When Mechanica shell-meshes the model, it places the mesh on the midsurface, using the shape of the red side to determine the shape of the midsurface. When you work with a partially compressed model, flipping pairs might produce a different shell mesh if geometries of paired surfaces are not equivalent. • Mixed Mesh (FEM mode) Use mixed meshing with parts or assemblies that have both solid and thin portions. If you selected mixed meshing, Mechanica meshes the solid portion of the model with tetrahedral elements. In addition, it meshes the thin portions of the model with triangular or quadrilateral elements, provided you have defined shell pairs for those areas. Mixed meshing helps avoid the creation of many small tetrahedral elements in thin part features. Where shell and solid meshed components are in contact along an edge, the software matches up nodes and assigns the default contact type, Bonded. If you want a different contact type, you need to select this before you mesh. When the mesh generation is complete, shell element nodes align with tetrahedral element nodes at any point on the model where a thin feature attaches to a solid feature. When Mechanica generates a mixed meshed model for a structural analysis and the fem_solid_shell_auto_constraint configuration option is set to YES, Mechanica automatically assigns a no-rotation condition to the nodes of solid elements that are connected to adjacent shell elements. Each node has only three degrees of freedom. Note: Mechanica does not set the no-rotation condition for solid element nodes by default, you can use the fem_solid_shell_auto_constraint configuration option to turn this function on or to have the software prompt you. 619 Structural and Thermal Simulation - Help Topic Collection Quilts A quilt represents a patchwork of connected nonsolid surfaces, and can consist of a single surface or a collection of surfaces. A quilt contains information describing the geometries of all the surfaces that compose a quilt, and information on how quilt surfaces join or intersect. A part or assembly can contain several quilts. In Pro/ENGINEER, you can assign a name to an entire quilt or to an individual surface by selecting Edit>Set Up>Name>Other. For more information about quilts, search the Surface functional area of the Pro/ENGINEER Help Center. Performing FEM Mode Mesh Operations Performing FEM Mesh Operations Use the Mesh>Operations command to import NASTRAN files and to create specialized mesh attributes for models processed in NASTRAN. When you select this command, the MESH OPER menu appears. Use this menu to perform any of the following operations: • • Import — Opens the MESH IMPORT menu. HPs on Nodes — Creates datum points on selected nodes and declares them as hard points. Importing NASTRAN Files Use the Import command on the MESH OPER menu to import NASTRAN files for use with FEM meshes. When you select this command, Mechanica displays the MESH IMPORT menu. The MESH IMPORT menu includes the following: • NASTRAN Deck — You can select a NASTRAN bulk data deck file to import. Node and element information is included as read-only in the bulk data deck file. The bulk data deck is the part of the .nas file between the lines BEGIN BULK and ENDDATA. Mechanica imports the mesh with respect to the current model WCS. After the deck is imported, you can define and apply hard point mesh controls to current geometry. You cannot use a mesh imported from a NASTRAN data deck later in an FEA solver or store the mesh in a file. See Guidelines for NASTRAN Deck Import for information on limitations for the file to be imported. • NASTRAN xdb — You can select a NASTRAN results file (.xdb) to import. 620 Structural and Thermal Simulation Selecting either of these two commands displays the Pro/ENGINEER Open dialog box, which you can use to select the desired files. Improving a FEM Mesh After the mesh generator creates a mesh, it attempts to improve the quality of the elements by performing two element optimization passes. During these passes, Mechanica examines the aspect ratio of each element to determine whether the element is well shaped so that it can be easily handled by the solver. The software also checks the elements to ensure that they comply with all element quality measures. If Mechanica determines that some of the elements are poorly shaped, it attempts to improve the elements by: • Smoothing — Mechanica adjusts the position of the nodes to improve element shape. During this process, the software does not introduce new nodes or elements, move nodes at hard points or vertices, or move nodes on edges, surfaces, or hard curves away from the edge, surface, or hard curve. Reconfiguring edges — For triangular elements, Mechanica reconfigures element edges shared by a pair of elements if it determines that a different edge configuration produces a better shape for the two elements. This form of optimization primarily improves triangular shell meshes. However, it can also improve solid tetrahedral meshes because Mechanica develops these meshes by first applying a triangular shell mesh to the model boundary surfaces and then working inward from this initial triangular mesh to create the tetrahedra. • The greatest improvement to the mesh occurs during these two element optimization passes, and, in most cases, you will not need to refine the mesh further. However, if you examine a mesh and think that the mesh still requires adjustment, you can use the Mesh>Improve command to perform additional optimization passes. As an alternative, you may want to add mesh controls to your model in areas that concern you, and then remesh the model. When you select the Mesh>Improve command, Mechanica performs the number of passes that you indicate, and displays a message in the message area indicating the number of passes it has completed. The pass count is cumulative. In other words, if you specify four additional passes, Mechanica will report six passes altogether—two passes that occurred as part of mesh creation plus the four passes you specified. The pass count persists from session to session—incrementing for each optimization pass—until you erase the mesh or create a new mesh. Be aware that the higher the pass count, the longer the mesher will need to perform the optimization. With each pass, the amount of improvement is also less. Reviewing a FEM Mesh Use the Mesh>Review command to review aspects of your mesh. You can also review a mesh if you select Display Only from the Solver option menu on the Run FEM Analysis dialog box or use Output to File to output a solver deck. 621 Structural and Thermal Simulation - Help Topic Collection When you select the Review command or use one of the Run FEM Analysis dialog box methods, the REVIEW MESH menu appears. This menu allows you to review the mesh after it is created or after an analysis is run. The menu includes: • Meshes — Review a mesh after you create it. You can review a list of components by path within the top-level assembly hierarchy, the number of elements and nodes, and the range of element and node ID numbers. You can also review the range of element, node, and local mesh entity IDs with the Mesh ID Offset mesh control applied. This type of review can help you identify and resolve any numbering conflicts. Nodes — Review nodes by selecting: o Coord Systems — Select this option to display a coordinate system icon at each selected node that will be oriented for nodal displacement. If the coordinate system is not Cartesian, then Mechanica calculates and displays the R, , and Z or direction instead. o All — Highlight all element nodes and display their node IDs. o Boundary — Highlight only boundary nodes and display their node IDs. This option only appears if the mesh includes solid elements. o Node ID — Highlight an individual node and display its ID. If you select this option, you enter the integer ID for the node you are interested in. o Select — Highlight an individual node and display its ID. In this case, you use your mouse to select the node on your model. o List Unused — Generate a list of unused node IDs. You use this option to help detect node ID conflicts in hierarchical meshes. You can correct these conflicts by applying mesh ID offset mesh controls to the conflicting nodes. Elements — Review elements by selecting: o Coord Systems — Display the coordinate system for the elements that you review. o Shell Normals — Display the shell normals for the elements that you review. This check box only appears if the mesh includes shell elements. o All — Highlight all elements and display their element IDs. o Boundary — Highlight only boundary elements and display their element IDs. This option only appears if the mesh includes solid elements. o Element ID — Highlight an individual element and display its ID as well as its node IDs. If you select this option, you enter the integer ID for the element you are interested in. o Select — Highlight an individual element and display its ID as well as its node IDs. In this case, you use your mouse to select the element on your model. o List Unused — Generate a list of unused element IDs. You use this option to help detect element ID conflicts in hierarchical meshes. You can correct these conflicts by applying mesh ID offset mesh controls to the conflicting elements. Connectivity — Highlight edges that are only included in one shell surface. You can also use this command to highlight a free node on a one-dimensional element such as a beam or spring. • • • 622 Structural and Thermal Simulation If you review the mesh at run time, Mechanica adds these options to the REVIEW MESH menu: • • • Materials — Highlight elements made of selected materials by selecting: o All — Highlight all elements with specified materials o Material ID — Highlight elements by specific material. Analyses — Highlight nodes or elements from a selected analysis and examine how the loads and constraints defined for the analysis apply to the mesh. Hard Points — Display an information window listing nodes that were created at hard points on the model. Checking Elements Checking a FEM Mesh Use the Mesh>Check Elements command to check the element quality of your mesh. When you select Check Elements, the Element Quality Checks dialog box appears. Note: The Element Quality Checks dialog box also appears immediately after you create a mesh, enabling you to check your mesh at that time. Use the Quality Measures part of the dialog box to indicate which element characteristics you want Mechanica to check. To streamline your selection process, this area of the dialog box provides a Select All Checks button and an Unselect All Checks button that you can use to quickly select and deselect the entire list of quality measures. Each Quality Measures check box represents one of seven tests performed on all elements in the mesh: • • • • • • • Aspect Ratio — Performed on all shell and solid elements. Warp Angle — Performed on shell quadrilaterals only. Skew — Performed on shell quadrilaterals only. Taper — Performed on shell quadrilaterals only. Edge Angle — Performed on shell quadrilaterals only. Distortion — Performed on parabolic tetrahedrons only. Mid Ratio — Performed on all solid and shell elements. The value initially displayed in each check box represents a basic setting for a wellformed element. If you want your mesh to meet looser or more stringent element limits, you can increase or decrease the individual values to customize your mesh check. Use the Check button to perform the mesh check. When the check is complete, Mechanica highlights any elements that do not meet the criteria in the Quality Measures area. 623 Structural and Thermal Simulation - Help Topic Collection If you want a more exact or permanent record of measurements for elements that fail the check, use the Screen and File options in the Output Element Statistics area of the dialog box. These options let you show the mesh check output in a text file displayed on your screen, write the output to a file so you can review it later, or both. The mesh check record lists failed element IDs, sorted by element types, along with their quality measures. You can use the Mesh>Review command to determine the location of the element associated with each element ID. If you find that you consistently reset one or more of the values on the Element Quality Checks dialog box, you can use config.pro options to set the defaults for this dialog box to values appropriate for your designs. Aspect Ratio (FEM mode) Aspect ratio is the measure of a mesh element's deviation from having all sides of equal length. A high aspect ratio occurs with long, thin elements. Entering an overly large value for the Minimum Element Size mesh control may cause the mesh generator to create solid elements with high aspect ratios. Mechanica calculates aspect ratio, R, according to this formula: R = E/h where E is the longest edge and h is the shortest height—the distance between a vertex and the opposite surface or edge. Warp Angle (FEM mode) Warp angle occurs when a quadrilateral shell element is so distorted that it turns back on itself. When you check your mesh, Mechanica uses the Warp Angle quality measures to highlight elements exceeding the maximum warp angle. Mechanica calculates warp angle, W, according to the following formula: W = arc sin (h/e) where h is the distance between the nodes and the reference plane, and e is the shortest edge. 624 Structural and Thermal Simulation Skew (FEM mode) Skew occurs when the angular distortion of a quadrilateral shell element approaches 0 . When you check your mesh, Mechanica uses the Skew quality measures to highlight elements having angles between included edges that exceed the maximum skew angle. Mechanica defines skew, S, as the difference between a right angle and the angle at the intersection of the mid-lines. 625 Structural and Thermal Simulation - Help Topic Collection Taper (FEM mode) Taper occurs when the angular distortion of a quadrilateral shell element approaches 180 . When you check your mesh, Mechanica uses the Taper quality measures to highlight elements having angles between included edges that exceed the minimum taper angle. Mechanica divides the quadrilateral element into four triangles by connecting the origin—the intersection of the mid-lines—with the corner nodes. The resulting triangles have areas A1, A2, A3, and A4. Mechanica calculates taper, T, according to this formula: T = 4a/A where a = min (Ai) is the smallest triangle area and A = sum (Ai) is the quadrilateral area. 626 Structural and Thermal Simulation Edge Angle (FEM mode) Edge angle is the measure of the acuteness of the angle formed by two edges of a quadrilateral element. A small edge angle typically occurs with long, thin elements. When the edge angle becomes too acute, the quality of the element is lower and the solver you use may have difficulty. Mechanica considers an ideal edge angle to be 90 . However, because this ideal is too stringent for most models, the software uses an edge angle of 30 as a default for this quality measure. Distortion (FEM mode) Distortion occurs when 10-node tetrahedral elements have too much curvature. The software uses a Jacobian distortion index as a measure of how distorted an element is. Distortion highlights elements which, if output as 10-node tetrahedrons, have a Jacobian distortion index less than the preset bound. Mechanica calculates the distortion as the ratio between the maximal Jacobian and the minimal Jacobian derived at the four Gaussian integration points. The software performs this test on solid elements only. 627 Structural and Thermal Simulation - Help Topic Collection Mid Ratio (FEM mode) Mid ratio is the relationship between the height and length of parabolic elements. A large mid ratio indicates that an element may have too much curvature. When you check your mesh, Mechanica uses the Mid Ratio quality measures to highlight element edges which, if output as parabolic elements, have mid ratios higher than the preset bound. The Mid Ratio quality measure is used primarily by the ANSYS FEA solver. Most other solvers disregard this mid ratio value. Mechanica calculates the mid ratio, M, according to this formula: M = h/L where h is the distance between the midnode and the connecting line of the corner nodes, and L is the distance between two adjacent corner nodes. The software performs this test on parabolic mesh only. Saving a FEM Mesh There are two ways to save a FEM mesh: • You can configure Mechanica to automatically save a mesh immediately after you create it. To implement this function, set the fem_mesh_preserve configuration option in your config.pro file. Note that, for automatic saves, the software always assigns a name of model.fmp for the mesh file of a part and a name of model.fma for the mesh file of an assembly. Be aware that setting the fem_mesh_preserve option means that your session will use retained meshes. You can manually save the mesh by clicking Save FEM Mesh on the File menu. Mechanica automatically assigns the default name of model.fmp(a) to the mesh file. If you want to assign a file name other than the default, set the fem_allow_named_mesh_files config.pro option in the config.pro file. The saving command on the File menu changes to Save Named FEM Mesh, and Mechanica prompts you to enter the file name each time you click the 628 • Structural and Thermal Simulation command. You can assign any file name that fits the established guidelines. With the fem_allow_named_mesh_files option set, Mechanica does not automatically retrieve the mesh when it opens the FEM model, but prompts you to select the named mesh file you want to load. Regardless of which approach you use, be aware that the .fmp(a) file stores the mesh model only. It does not store model properties such as loads, boundary conditions, or idealizations. Mechanica considers these properties to be part of the geometry model and stores them whenever you use File>Save to save your model. See these rules for naming your mesh files if you are working with family tables or have simplified representations of your model. Retrieving a FEM Mesh After you have saved a FEM mesh, you may want to retrieve it. While retrieving a mesh, Mechanica first checks for an .fmp(a) file saved for a current model in session. If the file exists, Mechanica imports a mesh from it. There are two ways to retrieve a mesh: • • If you set the fem_mesh_preserve config.pro option in your config.pro file, Mechanica automatically retrieves the saved mesh when you open the model in FEM mode. You can click Open FEM Mesh on the File menu, and Mechanica automatically retrieves a mesh saved under the default model.fmp(a) name. If you have set the fem_allow_named_mesh_files config.pro option in your config.pro file and assigned a different name to your mesh file, the File menu displays the Open Named FEM Mesh command. When you click this command, Mechanica opens a dialog box that enables you to select a named mesh file to load. You can retrieve the mesh only if you have not made changes to the geometry. The Open FEM Mesh command is not available if you are currently displaying a compressed model or results. Be aware that meshes created in one product are not usable in other products. For example, if you create a mesh in Structure, you cannot retrieve it in Thermal. Conflicting Coordinate Systems You can specify displacement coordinate systems for mesh controls on points, edges, curves, and surfaces in FEM mode. Because these geometric entities are part of the definition for modeling entities such as constraints, rigid links, and weighted links, a conflict may arise between the various coordinate systems when you output to the NASTRAN solver. There are several situations that may cause conflicts: • A conflict may occur if you use the same or adjacent geometry to define two modeling entities. For example, if you define constraint a using a surface, and 629 Structural and Thermal Simulation - Help Topic Collection • • • constraint b using an edge of that surface, a conflict could occur. In this case, the geometric precedence rules would respect constraint b over constraint a. A conflict may occur when coordinate systems are associated with two parts in an assembly. In this case, the assembly hierarchy of the part determines the precedence. You can view the assembly hierarchy in the Model Tree. A conflict may occur when coordinate systems are associated with a part or subassembly as well as a top-level assembly. In this case, you can suppress the part or subassembly coordinate system by using the Ignored Mesh Control option on the Mesh Control dialog box. A conflict may occur when coordinate systems associated with different entities, such as constraints and mesh controls, share a geometric entity or a node. For example, suppose you define a constraint on a surface with a Cartesian coordinate system (coordinate system A), and you also define a displacement coordinate system (coordinate system B) for a mesh control on the same surface. If the axes for both coordinate systems are parallel, but coordinate system B is rotated with respect to coordinate system A so that the X and Y axes are interchanged, a conflict will occur. Of course, non-parallel axes will also cause a conflict. Mechanica checks your displacement coordinate systems and attempts to resolve conflicts by using geometric and model-hierarchy precedence rules. If the software cannot resolve the conflicts, an error message appears and the output stops. You must resolve the conflict before the run can continue. When the software sets the displacement coordinate system for each node, it checks for conflicts in this order: • Mesh controls — The software checks for conflicts between displacement coordinate systems used to define mesh controls and tries to resolve them using geometric and assembly precedence rules. An example of a nonresolvable conflict is a different displacement coordinate system assigned to surfaces that belong to the red and yellow sides of a shell pair. The geometric precedence rules are: o A mesh control applied to a point overrides a mesh control applied to an edge or surface that contains that point. o A mesh control applied to an edge overrides a mesh control applied to a surface that contains that edge. Rigid or weighted links — The software checks for conflicts between the coordinate systems associated with rigid or weighted links and tries to resolve them using geometric and assembly precedence rules. • 630 Structural and Thermal Simulation • • • Mesh controls and rigid or weighted links — The software checks for conflicts between coordinate systems associated with links and displacement coordinate systems for mesh controls. Constraints — The software checks for conflicts between the coordinate systems associated with constraints and tries to resolve them using geometric and assembly precedence rules. If you apply a free and a fixed degree of freedom to the same node, the fixed constraint takes precedence over the free constraint. The presence of a fixed constraint also overrides the geometric precedence rules, so that a fixed constraint on a surface takes precedence over a free constraint on a point. A non-resolvable conflict may occur between partially fixed or partially free constraints on adjacent objects. Mesh controls, rigid or weighted links, and constraints — The software checks for conflicts between constraints and mesh controls, and between constraints and links. Reviewing Analyses When you select Analyses from the REVIEW MESH menu, Mechanica displays a sequence of menus that let you specify the analysis, load and constraint names, and load and constraint locations for the mesh information you want to see. The first menu Mechanica displays is the SEL ANALYSN menu. This menu includes a list of the analyses that you defined for the mesh. After you select an analysis, Mechanica displays the LOADS BC menu. This menu lists all of the load and constraint types you defined for the load sets and constraint sets in the analysis you selected. You use this menu to select a single load or constraint type or select all of them. Be aware that a given load type may include multiple loads of a similar category, and the same holds true for constraint types. After you select a load or constraint type, Mechanica displays the CONS PLACE menu, which enables you to select the entity you want to examine. The selections on this menu vary depending on whether you applied the load or constraint to elements or nodes. Here is a list of the possible selections: • • • • • • All — Display all nodes and elements associated with the loads and constraints. This item only appears if you select Display All on the LOADS BC menu. All Elements — Display all elements associated with the load or constraint type. This item only appears if you select a load or constraint type applied to surfaces. Element Id — Display the associated load and constraint on the specified element Id. All Nodes — Display all elements associated with the load or constraint. This item only appears if you select a load or constraint applied to points or curves. Node Id — Display the associated load and constraint on the specified node Id. Select — Display the associated load or constraint on the selected elements or nodes. 631 Structural and Thermal Simulation - Help Topic Collection Reviewing Connectivity Use the Review>Connectivity command to find: • • places where shell surfaces that should attach to one another are not connected. places where one or more nodes on a one-dimensional element do not correctly connect with the mesh. This type of review proves very useful for complex models with numerous connections. For example, if you were working with a beam model with a large number of interconnected beams or multiple beams connecting at a single point, a connectivity review would show you beams that are not fully connected to adjoining beams. When you select the Connectivity command, Mechanica displays the CONNECTIVITY menu, from which you select: • • Boundary Edges — Highlight edges that are only associated with one shell surface. Boundary Nodes — Highlight nodes at the boundary ends of beams, springs, gaps, and other one-dimensional elements. A boundary end of a onedimensional element is a node associated only with the one-dimensional element, itself, and not with any other mesh component. Guidelines for NASTRAN Deck Import The following are content guidelines for the NASTRAN file to be imported into Mechanica: • • • • • • • • CORD1* commands should come after referenced grid point (node) commands. A GRID command for a point not in the default coordinate system should follow the command for the referenced coordinate system. Two grid points (nodes) that have the same ID but different coordinates are not allowed in the same file or included files. Two elements with the same ID are allowed only if they reference exactly the same grid points (nodes). This guideline also applies to different files read with an INCLUDE statement. Elements referencing scalar points—points without coordinates—cannot be created. Mechanica does not display the center node for CQUAD elements. The continuation of a command should follow on the next line. Mechanica does not import the Replication command. 632 Structural and Thermal Simulation Example: Creating Load Paths for Pre-meshed Components The easiest way to learn about creating load-transmitting connections for premeshed components within a hierarchical mesh is by reviewing the steps involved. The following sample outlines this process. While you do not need to follow the exact order of these steps when you work with your own assemblies, be sure you understand the impact of each one and can reproduce its effect within your own process. For example you can create top-level assembly connections before or after you create hard points on pre-meshed components. You just need to make sure that the hard points are in place before you mesh the individual component. This sample process begins in part mode if the pre-meshed component is a part or is in assembly mode if the pre-meshed component is a subassembly. 1. Open the part or subassembly. At this point the part or subassembly should not yet have a mesh. If it does, erase the mesh. 2. Create datum points wherever you want to form connections with the toplevel assembly. As Mechanica uses these datum points to determine the load path, consider the distribution and placement carefully. 3. Define each datum point as a hard point mesh control, and then mesh the model. The resulting mesh establishes a node at every hard point. 4. In assembly mode, open the top-level assembly. The component meshed in step 3 should appear with its mesh. 5. Connect all pre-meshed components in the load path to the top-level assembly by creating a beam, spring, gap, rigid link, or weighted link. For the pre-meshed components, be sure to use one of the hard points established in step 3. For the top-level components, use any applicable geometry as the end of the idealization or link, as shown in this example: Here, there is a spring idealization that connects hard point 3 on the meshed part to datum point 10 on the unmeshed part. 633 Structural and Thermal Simulation - Help Topic Collection 6. Mesh the top-level assembly. When the mesh generator encounters connections with pre-existing meshes, it uses the hard points as element nodes and routes the beam, spring, gap, or rigid or weighted link to the meshed nodes, as shown below: Note that the mesh of the left part has nodes at all the hard points along the edge, but the elements of the left and right parts only have a coincident node where the spring is. These two nodes are where the load transmits. The mesh on the left is an inherited mesh—a pre-existing mesh that the toplevel assembly mesh inherits—while the mesh on the right and the spring element are both part of the top-level assembly mesh. This process varies slightly if you are connecting two pre-meshed components together. In this case, you need to create the connection hard points for both components before generating the respective component meshes. After both components have meshes that account for the hard points, you mesh the connections in the top-level assembly. In this case, the assembly mesh consists of only those elements that represent connection idealizations. Once you understand the steps just described and their implications, you may want to review some techniques that will help you create desired effects and handle special situations. Strategy: Establishing GeometricallyConsistent Node Locations You can use this approach to establish geometrically-consistent node locations for pre-meshed components in hierarchical meshes. 1. In assembly mode, create a datum point on a surface that opposes the two surfaces that will be in full contact. If there is no opposing surface, create a datum surface. 2. Project the datum point onto the two contacting surfaces. This should yield two datum points that are geometrically aligned. 634 Structural and Thermal Simulation 3. For the pre-meshed component, enter part mode and create a part-level datum point at the same location as the assembly-level datum point. You can position the part-level datum point by using the assembly level datum point as a reference and entering an offset of 0, 0, 0. 4. Define the part-level datum point as a hard point and mesh the component. Note: The zero-length spring must be an advanced spring, and you must define its orientation using a coordinate system. If both components are pre-meshed, you create the zero-length spring using the geometrically-aligned hard points on each component. When you mesh the top-level assembly, Mechanica creates matching nodes wherever you placed the geometrically-aligned points. However, be aware that, while this process assures that the surfaces will have geometrically-consistent nodes, the surfaces may have different overall meshes. Techniques for Establishing Consistent Hierarchical Meshes You may find these techniques and guidelines useful if you are working with premeshed components in a hierarchical mesh: • Create hard point mesh controls for all pre-meshed components as soon as is practical. If you create hard points early in the design process, you may be able to avoid remeshing individual components solely to make the mesh account for the hard points. Create beam, spring, and gap idealizations, as well as rigid and weighted links for the top-level assembly before meshing the component. If you create the idealizations first, you may find placement of the hard points easier because you have already established where the connections will lie. If you want to connect two pre-meshed components to each other, be sure you have hard points on both components. If you want to establish geometrically-consistent node locations for two touching components, you can create exactly matched points on the premeshed component and the component you want to connect it to. You then use zero-length advanced springs to connect the points. This technique works best if you follow a specific process. Be sure that the connections you create do not conflict with the physical design of the assembly. For example, if you have two pre-meshed components that share a surface region, you should make sure the connections line up properly for the shared region. • • • • Pairing Unopposed Surfaces If you want to create shell elements but have a surface with no opposing surface, you have three options. The option you choose depends on your particular modeling needs. 635 Structural and Thermal Simulation - Help Topic Collection Use one of the following methods to resolve unopposed surfaces: • • • Suppress the feature — Suppress the feature that causes the problem. This saves both modeling and calculation time, but also sacrifices the most in model accuracy. Create an opposing surface — Create a small feature to give the unopposed surface a pairing mate. Note, however, that this method has a dimensional impact on the finished mesh. Split the surface — Split the surface and distribute it among its neighboring surface pairs. This procedure, while sometimes difficult, does the best job of retaining model accuracy. FEM Mesh File Names When you are working with family tables, or have simplified representations of your model, Mechanica uses the following names for your FEM mesh files: • Part o o o o • model.fmp — master representation, or generic instance of a part model#rep1.fmp — simplified representation of a part model#inst1.fmp — family table instance of a part model#inst1#rep1.fmp — simplified representation of a family table instance Assembly o model.fma — any representation of assembly For more information on simplified representations and family tables, search the Fundamentals functional area and the Assembly and Welding functional area of the Pro/ENGINEER Help Center. Elements with Approximated Linear Edges While adding elements to your model, AutoGEM keeps track of elements that are invalid because of geometry problems. After adding all the good elements, AutoGEM attempts to complete the mesh by creating elements with approximated linear edges in areas where invalid elements occur. Mechanica adds the approximated elements to a new group named approx_elements. This group is only visible if you transfer the model to independent mode. Because approximated elements can affect the accuracy of your analysis, you should review the areas of your model that require approximated elements. In some cases, AutoGEM might not generate a full set of elements on surfaces and volumes. See Strategies for Using the Surface Option and Strategies for Using the Volume Option for information on actions you can take to enable AutoGEM to create additional elements. 636 Structural and Thermal Simulation Example: Orientation and Tolerance Settings Your model's orientation relative to the WCS can make a substantial difference in the size of the bounding box and resulting diagonal that Mechanica uses for relative tolerance settings, as shown below: Here, the extruded length of the model is substantially greater than its circular profile. Note that the diagonal measurement taken when the extruded length lies in the WCS XY plane is about 2.5 times longer than the diagonal measurement taken when the circular profile lies in the XY plane. Further, Mechanica determines the bounding box based on the nodal placement. If the model had included nodes only at the top and bottom, the bounding box and the resulting diagonal for the circular profile version would both have been a vertical line. Thus, when you develop a ratio for Relative to Model and Relative to Part, you need to be sure you have a reasonable estimate of what the bounding box will look like and how long the diagonal will be. If you do not keep this in mind, you may enter a ratio value too large with respect to the diagonal, and Mechanica will be unable to apply the tolerance. AutoGEM File Names When you are working with family tables, or have simplified representations of your model, Mechanica uses the following names for your AutoGEM mesh files: • Part o o o o model.mmp — master representation, or generic instance of a part model#rep1.mmp — simplified representation of a part model#inst1.mmp — family table instance of a part model#inst1#rep1.mmp — simplified representation of a family table instance 637 Structural and Thermal Simulation - Help Topic Collection • Assembly o model.mma — any representation of an assembly For more information on simplified representations and family tables, search the Assembly and Welding functional area and the Fundamentals functional area of the Pro/ENGINEER Help Center. Design Controls About Design Controls Use the Analysis>Mechanica Design Controls command to add design parameters to your model in order to define the way you want your model to change during sensitivity and optimization studies. Design parameters enable Mechanica to modify the model shape to achieve a design that meets your goals. For information about the process of adding and verifying design parameters, see: • • Overview of Design Parameters Types of Design Parameters When you select Analysis>Mechanica Design Controls, Mechanica displays the DSGN CONTROLS menu, which includes these commands: • • Design Params — Use to add design parameters to your model. Switch Dim — Use to review the dimension names or values for a feature before defining a design parameter. Select Switch Dim and then a feature to display the feature's dimension names. Select Switch Dim again to switch to a dimension value display. Shape Review — Show how design parameters change your model's shape at a specific value. Shape Animate — Show how design parameters change your model's shape in steps. Optimize Hist — Use to review the shape change history of your model during an optimization study and to overwrite your Pro/ENGINEER part with the optimized shape that Mechanica developed. • • • Design Parameters Overview of Design Parameters Based on the stresses or thermal conditions revealed during analysis, you can add design parameters to your model. Design parameters are entities that can change the shape of the model within a specified range during a sensitivity or optimization design study. The design parameters you create affect only the shape of the model. For example, you can add a design parameter to a radius, setting a range within which Mechanica translates the radius until it finds a new location that minimizes the stress of the model. See Example: Design Parameter. 638 Structural and Thermal Simulation Here is an overview of the steps you should follow to assign and verify design parameters in Mechanica. You should complete all the steps before creating and running a design study. 1. Prepare your model for design parameters by renaming dimensions, defining Pro/ENGINEER parameters, adding relationships, and examining the effect of dynamic feature suppression. This step is optional. 2. Define design parameters using any independent Pro/ENGINEER dimension or parameter. You can also create a new Pro/ENGINEER design parameter; however, these new design parameters reference the quantities of existing Pro/ENGINEER design parameters. 3. Review or animate the shape change. 4. Troubleshoot any shape change problems. 5. Modify or delete design parameters if necessary. Example: Design Parameter In the following example, you can place a design parameter on the outer radius of the end fin, as shown in the first view of the model. You define a range within which Mechanica can change the radius to find the location where the stress on the model is minimized. The second and third views show the model with the radius changed to the minimum and maximum range values. 639 Structural and Thermal Simulation - Help Topic Collection Prepare Your Model for Design Parameters Before you add design parameters to your model, you may want to perform the following preliminary procedures: • Assign more meaningful names to any dimensions for which you plan to create design parameters. You can assign dimension names either when you create design parameters or when you work with your part in Pro/ENGINEER. For information on naming dimensions, see Strategy: Changing Dimension Names. Create Pro/ENGINEER relations that tie dimensions together to produce the desired dimension relationship. In Mechanica, you use relations to make several dimensions move together. See Example: Relations and Guidelines for Using Relations. If you plan to create a design parameter using a Pro/ENGINEER parameter, be sure the Pro/ENGINEER parameter is independent. Although you can create a design parameter based on any numeric Pro/ENGINEER parameter, this type of application will not result in a model change unless the Pro/ENGINEER parameter is fully independent. If the Pro/ENGINEER parameter ever appears on the left—or dependent—side of any relation, Mechanica will be unable to alter the parameter value. For more information on independent Pro/ENGINEER parameters and how to create them, see Pro/ENGINEER Parameters. • Observe Mechanica conventions when naming Pro/ENGINEER parameters that you plan to use as design parameters. Mechanica limits design parameter names to 16 characters. You can use alphanumeric characters and underbars only. Names must always start with alphabetic characters. Because Mechanica uses the Pro/ENGINEER parameter name as the design parameter name, always observe these naming conventions when creating the Pro/ENGINEER parameters you plan to use as design parameters. If your Pro/ENGINEER parameter name is too long, the software will truncate it. • Check the Pro/PROGRAM file for dynamically suppressed or added features. You can add conditional statements to the Pro/PROGRAM file that dynamically suppress or add features. If your Pro/PROGRAM file contains conditional statements that affect features associated with design parameters, the Structure engine may be unable to optimize your part effectively due to large stress discontinuities inherent in adding or suppressing features on the fly. For more information on Pro/PROGRAM, see the Part Modeling area of the Pro/ENGINEER Help Center. • • 640 Structural and Thermal Simulation If you are simply running a regeneration analysis, dynamically adding or suppressing features should not cause a problem. For more information on using regeneration analyses, see Regeneration Analysis. If you want to keep the conditional statements in place and still use Mechanica to determine the effects of the design parameter, you can run a global sensitivity study. As you look at the resulting graphs, you typically will see a sudden change in the curve at the point where the feature was added or suppressed. Therefore, be sure to review the file before creating design parameters to determine whether you should remove any conditional statements. Types of Design Parameters You can create design parameters for any of the following entities: • • Independent dimensions — You can create design parameters using any Pro/ENGINEER dimension, provided that dimension is not defined as the dependent member of a relation. Independent, numeric Pro/ENGINEER parameters — You can create design parameters using any independent, numeric Pro/ENGINEER parameter. For information on the methods you should use to create Pro/ENGINEER parameters for use as design parameters, see Pro/ENGINEER Parameters. You can create a new Pro/ENGINEER design parameter or select from a list of valid parameters. The contents of the list depends on whether you are working in part or assembly mode. For part mode, Mechanica displays only the Pro/ENGINEER parameters created in part mode. For assembly mode, Mechanica displays only the parameters created in assembly mode. In other words, if you are working in assembly mode, you cannot access the part-level Pro/ENGINEER parameters. • Beam sections — You can create design parameters using any sketched solid or thin beam section. Design Parameters Use the Analysis>Mechanica Design Controls>Design Params command to create, edit, review, or delete design parameters in your model. A design parameter is a model feature on which you can instruct Mechanica to perform one of the following actions: • • vary within a specified range in a sensitivity or optimization design study change to a specified setting in a standard design study 641 Structural and Thermal Simulation - Help Topic Collection You can create design parameters for: • • • • • dimensions Pro/ENGINEER parameters beam sections material properties laminate layup shell properties for shell models When you select the Design Params command, the Design Parameters dialog box appears. The dialog box lists all design parameters you have defined for the current model and displays a description of the selected design parameter. The following buttons are available on the dialog box: • • • Create — Click to create a new design parameter. Review — Click to review or edit the current values of the selected design parameter. Delete — Click to delete the selected design parameter. For more information on using design parameters when creating laminate layup shell properties for shell models, see Design Parameters with Laminate Layup. Create Design Parameters When you click Create on the Design Parameters dialog box, the Design Parameters Definition dialog box appears. Use this dialog box to create or edit a design parameter. You can specify the range across which you want Mechanica to vary the value of the design parameter when analyzing your model. The Design Parameters Definition dialog box contains the following items: • • • • Name — Enter or edit the design parameter name. Description — Enter or edit the description of the design parameter. This item is optional. Type — Select the type of design parameter you want to create— Dimension, Pro/ENGINEER Parameter, or Section Dimension. Select — Click to select the dimension or parameter for which you want to create a design parameter. If you select one of the listed parameters, be sure it is an independent parameter, the parameter value is constant, and the parameter is not currently being used as a measure. Minimum — Enter the minimum desired value for the design parameter. Current — Enter the value you want Mechanica to use as the current value for the design parameter. Maximum — Enter the maximum desired value for the design parameter. Note: Although you can specify negative values, be sure that a negative value is valid for the dimension type in Pro/ENGINEER. For • • • 642 Structural and Thermal Simulation example, you would not specify a length as a negative number, but you could specify an angle as a negative number. If you specify a negative value where you should not, the software will be unable to regenerate the part during design studies, shape animation, or shape review. To Define a Design Parameter You have to define design parameters before running a design study. 1. Select Analysis>Mechanica Design Controls. 2. If you want to review the dimension names or values for a feature before defining a design parameter, select Switch Dim. 3. Select Design Params. The Design Parameters dialog box appears with a list of previously defined parameters. 4. Click Create. The Design Parameter Definition dialog box appears. 5. Select the type of design parameter you want to define. Continue with the procedure for defining each type of design parameter by clicking one of the following: o o o Dimension Pro/ENGINEER Parameter Section Dimension To Define a Dimension Design Parameter This procedure assumes that you are in the Design Parameter Definition dialog box and that you selected Dimension for Type. 1. Click Select. Mechanica closes the dialog box. 2. Select a feature on your model for which you want to create design parameters. Mechanica displays the feature dimensions. 3. Select a dimension. 643 Structural and Thermal Simulation - Help Topic Collection The Design Parameter Definition dialog box appears with the name and current value of the design parameter. Mechanica also inserts reasonable minimum and maximum values. 4. Enter a name for the dimension design parameter in the Name entry box. Choose a name that has not been assigned to another design parameter. 5. Review the minimum and maximum values and change them if necessary. Be sure that the values are physically appropriate. For example, a negative value is valid for an angle but not for a length. 6. Click Accept. The Design Parameters dialog box appears and displays the design parameter you just created. To Define a Pro/ENGINEER Design Parameter This procedure assumes that you have selected type Pro/ENGINEER on the Design Parameter Definition dialog box. You can base the design parameter on a Pro/ENGINEER parameter, or create a new parameter. 1. Click Select. The Select Pro/ENGINEER Parameter dialog box appears with previously defined parameters in the list box. 2. If you want to use one of the listed parameters, select the parameter name. The Design Parameter Definition dialog box appears with the name and current value of the design parameter. Mechanica also inserts reasonable minimum and maximum values. 3. If you want to create a new Pro/ENGINEER parameter, see To Create a Pro/ENGINEER Parameter. 4. Review the minimum and maximum values and change them if necessary. Be sure that the values are physically appropriate. For example, a negative value is valid for an angle but not for a length. 5. Click Accept. The Design Parameters dialog box appears. The dialog box now shows the design parameter you just created. 644 Structural and Thermal Simulation To Define a Section Dimension Design Parameter This procedure assumes that you have selected type Section Dimension on the Design Parameter Definition dialog box. 1. Click Select. The Select Pro/ENGINEER Beam Section dialog box appears. 2. Select one of the beam sections listed. Mechanica closes the dialog box and displays the beam section dimensions on your model. 3. Select a dimension. The Design Parameter Definition dialog box appears with the name and current value of the design parameter. Mechanica also inserts reasonable minimum and maximum values. 4. Enter a name for the dimension design parameter in the Name entry box. Choose a name that has not been assigned to another design parameter. 5. Review the minimum and maximum values and change them if necessary. Be sure that the values are physically appropriate. For example, a negative value is legal for an angle but not for a length. 6. Click Accept. The Design Parameters dialog box appears. The dialog box now shows the design parameter you just created. Shape Review Use the Analysis>Mechanica Design Controls>Shape Review command to show a model's shape changes in response to one or more design parameters set at values you specify. This review shows you shape changes similar to those that will occur during a design study and helps you spot potential problems before executing a time-consuming study. For example, you may find conflicts between design parameters. The Shape Review dialog box contains the following items: • • Parameters — Select the design parameters to include in the shape review. Settings — Enter a value for each parameter in the Settings box. 645 Structural and Thermal Simulation - Help Topic Collection When you click the Review button to start the shape review, Mechanica displays the model with the dimensions set to the specified values. After displaying the shape change, Mechanica gives you the option to restore the model to its original state before the shape review or to replace your original model with the new shape. To see how a shape review changes a model's shape, see Example: Shape Review. For information on problems that may occur when design parameters change your model's shape, see: • • Design Parameter Errors Troubleshoot Shape Change Problems Example: Shape Review In this example, a design parameter applied to the end fin's outer radius has a range of 0.8 to 1.5. The current value of the design parameter is 1.125, as shown in the first view of the model. If you perform a shape review and specify the new value as 0.8, you would see the shape change illustrated in the second view of the model: 646 Structural and Thermal Simulation To Perform a Shape Review 1. Select Analysis>Mechanica Design Controls>Shape Review. The Shape Review dialog box appears with a parameter list of all design parameters you created for the part or assembly. 2. Select each design parameter you want to include in the shape review. 3. Enter or select a number in the Settings entry box. You can define values that lie outside the minimum and maximum range you defined when you created the parameter. 4. Click Review to start the shape review. Design Parameter Errors When a model's shape changes during a design study, shape review, or shape animation, Mechanica may encounter topological changes or other changes that it cannot process. If this occurs, Mechanica places an error message in the engine log file. The following changes can produce error messages: • Dimensioning Conflicts — When a design parameter changes, it can create dimensioning conflicts that prevent Pro/ENGINEER from regenerating the model. In this case, the software displays a warning indicating that it cannot regenerate the model. Topology Changes — As a design parameter changes, it can alter your model's topology. Topology is the association and connectivity between the model's geometric entities. Topological changes can create new surfaces and curves or delete existing surfaces and curves. Keep in mind the following when determining whether to accept a design parameter that changes topology: o If your model undergoes a topology change, the optimizer may encounter discontinuities that cause it to stop prematurely due to a stress peak when new geometry appears or old geometry disappears. If the design parameter change deletes a surface, curve, point, or region associated with a load, constraint, or measure, Mechanica cannot update the model. If the design parameter change causes surface regions to intersect, Mechanica retains the first region as is but removes the section of the second region where the overlap occurred. The software redistributes any loads applied to the second region over what remains of that region. Consequently, your model may experience stress concentrations as the second region becomes smaller. • o o • Dependent Dimensions — If you are applying a design parameter to a dimension, you can only work with independent dimensions. If you create a 647 Structural and Thermal Simulation - Help Topic Collection design parameter and add a Pro/ENGINEER relation that makes the design parameter's dimension dependent, Mechanica will not recognize that design parameter. Troubleshoot Shape Change Problems When you review or animate your model, you may find that the design parameters change the model's shape in ways you did not anticipate. If you encounter this situation and cannot determine why the shape is changing unexpectedly, look for conflicts or problems with the following: • Relations — Problems with relations are a common source of unexpected shape changes. If you use relations to make dimensions move relative to one another, review the relations or look at the Pro/PROGRAM file. Try to locate errors in the relations or conflicts between relations. For more information on Pro/PROGRAM, see the Part Modeling area of the Pro/ENGINEER Help Center. Pro/ENGINEER parameters in multiple relations — Pro/ENGINEER parameters that appear in multiple relations can cause unexpected shape changes. If you define a design parameter based on a Pro/ENGINEER parameter, review all the relations associated with the parameter to make sure you understand their implications. Try to locate relations that you may have forgotten about. Parent/child relationships — Child dimensions can move in unexpected ways or freeze depending on the changes in the parent dimension. Thus, in moving a parent feature, you may see a child change shape or position. If you suspect this problem, review the parent/child relationships for your part and redimension the part if necessary. Dimensions based on datum planes or center lines — You can use datum planes or center lines to position features in your part. Positioning dimensions of this sort may freeze feature movement. Among other things, this can result in size changes that translate feature position rather than maintain feature centering. If you suspect this problem, consider adding a design parameter to move the positioning dimensions as well as the sizing dimensions. As an alternative, you may want to redimension your part or redefine the relations. • Sketcher assumptions — When you dimension a part, Pro/ENGINEER's sketcher makes certain assumptions about undimensioned areas of your part. These assumptions can result in unwanted part movement. For example, if you are designing an L-bracket and dimension the width of only one leg, the sketcher assumes an identical width for both legs. Should you create a design parameter for this dimension, Mechanica will move the width of both legs instead of just the leg with the design parameter. If you suspect that the problem is the result of sketcher assumptions, add extra dimensions to counteract the sketcher assumptions. • • • 648 Structural and Thermal Simulation Shape Animate Use the Analysis>Mechanica Design Controls>Shape Animate command to show the effects of one or more design parameters on your model. Shape Animate allows you to view the shape changes in steps, not just at a specific value. You should use Shape Animate as well as Shape Review to preview shape changes and prevent problems with your design parameters before running a design study. The Shape Animate dialog box contains the following items: • • • Parameters — Select the design parameters you want to include in the shape animation. Settings — Enter starting and ending values in the entry boxes for each parameter. Number of Intervals — Select the number of steps for the shape animation. When you click the Animate button to start the shape animation, Mechanica initially displays the model with the dimensions set to the start values. Mechanica then asks if you want to move on to the next step in the animation. You have the option of continuing or stopping the animation at each step. At the end of the animation, you have the option to restore the model to its original shape before the animation or replace the original model with the new shape. To see how shape animation changes a model's shape, see Example: Shape Animation. For information on problems that may occur when design parameters change your model's shape, see: • • Design Parameter Errors Troubleshoot Shape Change Problems 649 Structural and Thermal Simulation - Help Topic Collection Example: Shape Animation This example shows a model's shape animation in four steps using the default start and end values of 0.8 and 1.5: 650 Structural and Thermal Simulation To Perform a Shape Animation Use this procedure to view in steps the changes made by a design parameter. 1. Select Analysis>Mechanica Design Controls>Shape Animate. The Shape Animate dialog box appears with a list of the design parameters you created for the part or assembly. 2. Select the design parameters you want to include in the shape animation. 3. Enter or select a number for the starting value for each design parameter in the left entry box under Settings. 4. Enter or select a number for the ending value for each design parameter in the right entry box under Settings. 5. Select the number of steps for the animation in the Number Of Intervals box. 6. Click Animate to start the shape animation. Guidelines for Using Relations When using relations with Mechanica, bear the following factors in mind: • You cannot assign design parameters to dependent dimensions. Dependent dimensions are dimensions that appear on the left side of a relation. If your model contains dependent dimensions, Mechanica does not display them during design parameter creation. If you need to assign a design parameter to a dependent dimension, consider redefining your relations to make the dimension independent. For more on dependent relations, see Design Parameter Errors and Pro/ENGINEER Parameters. • • You can use the Tools>Parameters command or Pro/PROGRAM to add relations. You can use nested relations in design parameters. If you do so, be aware that Pro/ENGINEER maintains all relations in a chronological list. When it refers to the list, Pro/ENGINEER tries to satisfy the relations sequentially, starting with the first relation. Therefore, for nested relations, be sure to define the highest level relation first and work downward from there. If you do not work downward through the nest, the order in which you assigned the relations may prevent Pro/ENGINEER from satisfying all the relations. • If you want to change the thickness of a shell model using a design parameter, you need to make sure both surfaces that make up the shell pair move an equal distance in opposite directions. This type of movement maintains the correct positioning of the midsurface during the thickness change. 651 Structural and Thermal Simulation - Help Topic Collection If you dimensioned the paired surfaces in relation to a datum plane or an entity in the part, the easiest way to create this effect is by setting up a relation between the two paired surfaces. In this case, you could create a datum plane at the midsurface and write the relation in terms of that plane. As an alternative, you could treat the distance from the midsurface to the dimensioning entity as an absolute value and write the relation in terms of that value. Example: Relations With properly defined relations, you can create complex shape changes with fewer design parameters. For example, you can use relations to decrease the size of the following rectangular slot while maintaining its proportions and centering. As you look at the figure, note that the slot is dimensioned to default datum planes for orientation purposes. In this case, the width of the slot (slt_width) is 3/4 the length of the slot (slt_length). To maintain this proportionality and ensure that the slot remains in the center of the model, you would assign the following relations: • Relation 1 — ties the positioning width (dtm_wid) to the positioning length (dtm_len) so that the slot expands and contracts while maintaining its center position. This relation is: dtm_wid = (3*dtm_len)/4 • Relation 2 — ties slt_width to slt_length, so that any change made in the slot length would result in a proportional change to the width. This relation is: slt_width = (3*slt_length)/4 652 Structural and Thermal Simulation Because relations control dtm_wid and slt_width, you would only need to create design parameters for dtm_len and slt_length. Without these relations, you would need to define four design parameters to simulate the movement—one for each dimension. Design Parameters with Laminate Layup When you create laminate layup shell properties, design parameters enable you to control such aspects of the laminate as layer thickness and orientation. For example, you can designate the thickness of a laminate layer as a design parameter, and then define an optimization study that asks Mechanica to find the minimum thickness that will preserve laminate strength. If you delete a design parameter associated with a laminate layer thickness or orientation, Mechanica converts the value shown on the Shell Properties dialog box to the current value of the design parameter. At this point, you can no longer vary or control the value for a design study. In this case, you may want to review the design study to ensure that it still meets your needs. For more information on the laminate layup version of the Shell Properties dialog box, see Laminate Layup. Strategy: Using Design Parameters In Mechanica, you can use design parameters to define the design space you want to explore during sensitivity and optimization studies. When you define design parameters, identify aspects of the model you can vary within manufacturing constraints and tolerances. Define individual design parameters, which you can vary from 0% to 100%, for those aspects. If you want to vary more than one aspect at a time—in other words, as a unit—you can build a relation that moves the aspects together and use that relation as the design parameter. Use the Analysis>Mechanica Design Controls>Shape Animate and Analysis>Mechanica Design Controls>Shape Review commands to make sure that the model geometry and mesh remain valid throughout the design space you plan to use for a particular study. You may find that you need to change some of the design parameter limits or add additional design parameters to achieve the desired modification. Use the following strategies for reviewing the effect of your design parameters on the model: • • • Before running a local sensitivity study, use Shape Review. Set the value for each parameter to the starting position you plan to use. Then use the Review menu to check the shape of the model at those settings. Before running a global sensitivity study, use Shape Animate and set the values for each parameter to the range you plan to use for the study. Then review an animation of the model's changes across each of those ranges. Before running an optimization study, use Shape Review to review all parameters at their starting positions. You can also use Shape Review to 653 Structural and Thermal Simulation - Help Topic Collection look at combinations of parameters you think could create possible shape change conflicts. For example, if setting the radius of a curve to 100% of its range while setting the translation of that curve to 0% of its range could cause the geometry to significantly change its shape, review the shape using that combination. Then use Shape Animate to vary your parameters across different ranges and in different combinations to find any problems the engine might encounter while optimizing the model. At a minimum, animate your model across the entire range of each parameter you plan to include in the optimization study. You can also use the results of local and global sensitivity studies to predict how the engine might change particular design parameters to achieve your goal. Use this information to set the parameter ranges for your optimization study. Verifying Models Checking Your Model It is a good idea to check your model before you start your run to detect errors in your model that can cause: • • the results of a design study to be inaccurate the design study to terminate abnormally You can check your model to make sure that the work you did passes Mechanica's validity checking. To do so, select the Info>Check Model menu option on the Analyses and Design Studies dialog box before running your analysis or design study. As an alternative, you can start the run and click OK to use error detection during the run. You might want to check your model more than once before starting a run to: • • Check for errors that are specific to the analyses and design studies you create. Make sure that any edits you made to your model did not create any new errors. 654 Structural and Thermal Simulation Validity Checking Mechanica performs error checks when you select the Info>Check Model menu option on the Analyses and Design Studies dialog box. For each error it finds, Mechanica: • • highlights any entities involved displays a message box with an error message Unless otherwise indicated, these errors prevent you from starting a design study run. Mechanica's error checks fall into three categories: • • • Structure and Thermal Structure Thermal The error checking process does not include model repair. Mechanica reports only corruption errors related to modeling entities. If it encounters topological or geometric errors, Mechanica exits and returns you to Pro/ENGINEER. Structure and Thermal Errors In both Structure and Thermal, Mechanica searches for the following errors: • • Missing properties Invalid analysis definitions Missing Properties Mechanica highlights any components to which you have not assigned material properties or other properties. Use the Properties menu to assign any missing properties. Invalid Analysis Definitions Mechanica makes sure that you have defined all analyses correctly. For example, Mechanica detects analyses that have no constraint sets or that have neither load sets nor prescribed displacements. These errors can occur if you delete a constraint set or load set after including it in an analysis. Use the Analysis>Mechanica Analyses/Studies command to open the Analyses and Design Studies dialog box, which you can use to edit the analysis definition. For more information, see About Analyses. 655 Structural and Thermal Simulation - Help Topic Collection Mechanica also warns you if your model contains dynamic time, frequency, or random response analyses, and you have not defined any measures of the types calculated for those analyses. You can define new measures with the Insert>Simulation Measure command. Structure Errors In Structure only, Mechanica searches for the following errors: • • Missing constraints Constraint–constraint conflicts Constraint–Constraint Conflicts If you place constraints on associated entities that are incompatible, and include those constraints in the same set, Mechanica highlights the constraint icons. For example, if you constrained a shell in the X direction, but also placed an enforced displacement on one of the shell's edges in the same direction, the constraints will conflict if they are in the same set. As a general rule, you should not constrain any associated entities of an entity that you have already constrained if you plan to include the constraints in the same set. Missing Constraints Mechanica makes sure that there are constraints in your model. Note that a point-toground spring is a constraint. You cannot define an analysis for a model with no constraints, unless you select one of the following: • • For a modal or prestress modal analysis select Unconstrained on the dialog boxes for modal analyses. For a dynamic time, dynamic frequency, or dynamic random analysis select Use Modes From Previous Design Study on the Previous Analysis tabs of the dialog boxes for dynamic analyses. Thermal Errors In Thermal only, Mechanica searches for the following errors: • • Missing prescribed temperatures or convection conditions Conflicting prescribed temperatures 656 Structural and Thermal Simulation Missing Prescribed Temperatures or Convection Conditions Mechanica makes sure that your model has one of the following: • • prescribed temperatures convection conditions You cannot define an analysis for a model without at least one constraint set containing one of these two conditions. Conflicting Prescribed Temperatures If you have placed prescribed temperatures of different values on associated entities, and included those prescribed temperatures in the same constraint set, Mechanica highlights the prescribed temperature icons. As a general rule, you cannot include prescribed temperatures of different values in the same constraint set if they are on associated entities. To Promote Simulation Features to Pro/ENGINEER 1. In the work area, select the simulation feature you want to promote. 2. Select Edit>Promote. The software promotes the highlighted feature to Pro/ENGINEER. When you view the model in Pro/ENGINEER, an icon representing the promoted feature appears on the model. To Create a Pro/ENGINEER Parameter This procedure assumes that you have selected type Pro/ENGINEER on the Design Parameter Definition dialog box, and you are in the Select Pro/ENGINEER Parameter dialog box. 1. Click Create. The Create a Pro/ENGINEER Parameter dialog box appears. 2. Enter a name for the new Pro/ENGINEER parameter. 3. Enter a numerical value for the parameter. Mechanica highlights the new parameter and returns you to the Select Pro/ENGINEER Parameter dialog box. 657 Structural and Thermal Simulation - Help Topic Collection Creating Analyses About Analyses Use the Mechanica Analyses/Studies command to create and manage analyses. For FEM mode analyses, see About FEM Analysis and About Running FEM Analyses and Generating Output Decks. In an analysis: • • You specify some combination of constraints and loads for your model that Mechanica uses to calculate the model's response. You enter information that determines how Mechanica calculates and reports results for the analysis when you include the analysis in a design study and run the study. You can create many types of analyses in each Mechanica product. For general information on creating an analysis, see Creating Analyses and Design Studies. For information on creating analyses in each Mechanica product, see the following: • • • Structural Analysis — Includes static, prestress static, large deformation static, contact, modal, prestress modal, buckling, and fatigue analyses. Thermal Analysis — Includes steady thermal and transient thermal analyses. Vibration Analysis — Includes dynamic time, dynamic frequency, dynamic random, and dynamic shock analyses. Creating Analyses and Design Studies Use the Analyses and Design Studies dialog box to create analyses and design studies. The dialog box contains a list of existing analyses and design studies, if there are any. Mechanica adds to this list any new analyses or design studies that you create. The Analyses and Design Studies dialog box includes the following options on the File menu for creating new analyses and design studies: • • • • • • • 658 New Static — Create a new static analysis. New Modal — Create a new modal analysis. New Buckling — Create a new buckling analysis. New Fatigue — Create a new fatigue analysis. New Prestress — Create a new prestress static or prestress modal analysis. New Dynamic — Create a new dynamic time, frequency, shock, or random analysis. New Design Study — Create a new design study. Structural and Thermal Simulation Analyses and Design Studies Dialog Box When you select the Analysis>Mechanica Analyses/Studies command, the Analyses and Design Studies dialog box appears. Use this dialog box to manage and run your analyses and design studies. The Analyses and Design Studies dialog box includes the following: • Menu bar — Perform the following activities using the options on the menu bar: o Create new analyses and design studies using the options available on the File menu. o Modify existing analyses and design studies using the Edit>Analysis/Study menu option. You can also copy or delete analyses or design studies using the options on the Edit menu. o Set up a run using the Run>Settings menu option or selecting the Configure Run Settings button on the toolbar to display the Run Settings dialog box. o Create a batch file to run more than one analysis or design study at a time using the Run>Batch menu option. o Check your model before you start a run by using the Info>Check Model menu option. o Start, stop, or restart analyses and design studies using the options on the Run menu or the buttons on the toolbar. o Monitor the status and view a detailed summary of a run using the Info>Status menu option. o Review the error and warning messages generated during a run using the Info>Diagnose menu option. Toolbar — Use the toolbar buttons to perform many of the functions available on the menu bar. Analyses and Design Studies Table — Lists the name and type of analyses and design studies for the current model. To perform an action on a specific analysis or design study, highlight it in the list and select the action from the options on the menus or use the toolbar buttons. Description — Displays a description, if available, of the analysis or design study you select from the list. • • • Closing the dialog box does not initiate any actions. Analysis Types You can create these types of analysis within each Mechanica product. Product Structure Analysis Types • • Static o Large Deformation Static o Contact Prestress Static 659 Structural and Thermal Simulation - Help Topic Collection Product Analysis Types • • • • Buckling Modal Prestress Modal Fatigue Steady-State Thermal Transient Thermal Dynamic Dynamic Dynamic Dynamic Time Response Frequency Response Random Response Shock Response Thermal • • • • • • Vibration (part of Structure) Note: Fatigue analysis requires a separate software license. If you do not have a license, you can use Mechanica in demo mode. When you run design studies, you have the option of running an analysis type called regeneration analysis. This type of analysis simply regenerates your model and is a means of running a design study without first having to run another type of analysis. In addition to 3D analysis, Mechanica allows you to perform 2D analysis on one planar or multiple coplanar edges, curves, faces, or surfaces in your model. Before performing 2D analysis on your model, you must select a 2D model type, the geometry on which you want to perform the 2D analysis, and a reference coordinate system. To read about selecting a model type, see About Specifying a Product, Mode, and Model Type. Before defining an analysis for a 2D model type, read Guidelines for Working with Model Types. Structural Analysis About Structural Analysis Use the Analysis>Mechanica Analyses/Studies command to define a structural analysis. You can define the following types of structural analyses: • • • • • 660 Static — Calculates deformations, stresses, and strains on your model in response to specified loads and subject to specified constraints. Prestress Static — Uses results from a static analysis to calculate deformations, stresses, and strains on your model. Large Deformation Static — Calculates geometrically nonlinear deformations and stresses in a static analysis. Contact — Calculates the effects of loads on contact regions in your model. Modal — Calculates the natural frequencies and mode shapes of your model. Structural and Thermal Simulation • • • Prestress Modal — Uses results from a static analysis to calculate the natural frequencies and mode shapes of your model. Buckling — Uses results from a static analysis to determine the critical magnitudes of loads at which a structure will buckle. Fatigue — Uses results from a static analysis to calculate the effect of fatigue loading on the life of your model. For static, prestress static, large deformation, contact, and buckling analyses, Mechanica automatically calculates all measures valid for a static analysis. For modal and prestress modal analyses, Mechanica automatically calculates all measures that are valid for a modal analysis. See Sample Uses for Prestress and Buckling Analyses for an example of when you might use each of these analysis types. See Constraint and Load Sets in Structural Analyses for information on including load sets and constraint sets in your analyses. Constraint and Load Sets in Structural Analyses Your model's loading condition determines the type of analysis you should use. When you are defining structural analyses, use the following guidelines: • • • • • • For a static, prestress static, large deformation static, and contact analysis, you do not need a load set if you use a constraint set with an enforced displacement. Otherwise, you must have at least one load set. For a modal or prestress modal analysis, you do not need a constraint set if you select Unconstrained when you define the analysis. Do not select a constraint set that contains an enforced displacement constraint. For any analysis type other than dynamic shock, point-to-ground springs are equivalent to point constraints. You do not have to select a constraint set if your model is sufficiently constrained by such springs. For all dynamic analyses, you can select a load set that contains a thermal load, but it will not be used for calculations. For dynamic time, frequency, and random analyses, you can choose to have Mechanica calculate results separately for each load set you include, or sum the sets as if they are acting simultaneously. If you delete a constraint set or load set after you include it in an analysis, Mechanica automatically deletes that set from the analysis. Even if you create a new set with the same name as the set you deleted, you must edit the analysis and reselect the set. Otherwise, you may invalidate the analysis, and any design studies in which you included the analysis. Static and Prestress Static Analyses Static and prestress static analyses examine similar aspects of your model's structural behavior. You can use static analysis to calculate deformations, stresses, and strains on your model in response to specified loads and subject to specified 661 Structural and Thermal Simulation - Help Topic Collection constraints. You can use prestress static analysis to simulate how a prestiffened or prestressed structure affects your model's deformations, stresses, and strains. For a description of and requirements for each analysis type, see Static Analysis Overview and Prestress Static Analysis Overview. These items appear on the Static Analysis Definition and Prestress Static Analysis Definition dialog boxes: • • • Constraints — Select a constraint set. Loads — You can select one or more load sets. You need at least one load set or a constraint set with an enforced displacement. Nonlinear Options (appears only on the Static Analysis Definition dialog box) — You can select Compute Large Deformations or Include Contact Regions if your model is valid for these options. For models with contact regions, Include Contact Regions is selected by default. If you do not want to include contact regions in your analysis, you must deselect this option. If you want to use either of these options, see: o Large Deformation Static Analysis o Contact Analysis The following tabs appear on the Static Analysis Definition and Prestress Static Analysis Definition dialog boxes: • • • • Previous Analysis (appears only on the Prestress Static Analysis Definition dialog box) Temperature Distribution (available on the Static Analysis Definition dialog box only for models with temperature-dependent material properties) Convergence Output Static Analysis Overview Description Use to calculate deformations, stresses, and strains on your model in response to specified loads and subject to specified constraints. A static analysis can tell you if the material in your model will stand stress and if the part might break (stress analysis), where the part might break (strain analysis), how much the shape of the model changes (deformation analysis), and the effects of loads on any contact regions (contact analysis). Requirements • • 1 constraint set 1 or more load sets or enforced displacements See Constraint and Load Sets in Structural Analyses for more information. 662 Structural and Thermal Simulation To Create a Static Analysis 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Static from the File menu. The Static Analysis Definition dialog box appears. 3. Enter a name for the analysis. A description is optional. 4. Select a constraint set. 5. Select one or more load sets. If your constraint set includes an enforced displacement constraint, you do not need to select a load set. 6. If nonlinear options are available for your model, you can select one of the following: o o Calculate Large Deformations — See To Create a Large Deformation Static Analysis. Include Contact Regions — See To Create a Contact Analysis. This option is selected by default if your model includes contact regions. If you do not want to include contact regions in your analysis, you must clear this item. . 7. Click the following tabs on the dialog box to select additional options for the static analysis: o o o o Load Intervals (available only if you selected a nonlinear option in step 7) Convergence Output Temperature Distribution (available only for models with temperature-dependent material properties) 8. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. 663 Structural and Thermal Simulation - Help Topic Collection Prestress Static Analysis Overview Description Use to simulate how a prestiffened or prestressed structure affects your model's deformations, stresses, and strains. A prestress static analysis determines the strengthening or weakening of the part due to the applied loads. For example, you can run a prestress static analysis on a ski lift to determine the strengthening or weakening caused by a pretension cable. Results of a previously run static analysis are the starting point for a prestress static analysis. You run a prestress static analysis in addition to a static analysis for the following situations: • • • if you want a transverse effect for your model if you think your applied loads affect the stiffness of the model—for example, if you have a model with an existing load that projects an existing force if the specified loads in the static analysis are close in magnitude to a corresponding buckling load. In this case, the prestiffening effects are negligible from a static analysis. You should run a prestress static analysis for more specific information. Requirements • • • • 1 1 1 a constraint set or more load sets or enforced displacements or more static analyses 3D model See Constraint and Load Sets in Structural Analyses for more information. To Create a Prestress Static Analysis You must run a static analysis before you use this procedure. Mechanica uses the results from the static analysis to calculate the prestress static analysis. 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Prestress>Static from the File menu. The Prestress Static Analysis Definition dialog box appears. 3. Enter a name for the analysis. A description is optional. 664 . Structural and Thermal Simulation 4. Select a constraint set. 5. Select one or more load sets. If your constraint set includes an enforced displacement constraint, you do not need to select a load set. 6. Click the following tabs on the dialog box to select additional options for the prestress static analysis: o Previous Analysis o Output o Convergence 7. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. Large Deformation Static Analysis In a large deformation static analysis, Mechanica calculates geometrically nonlinear static results. To define a large deformation analysis, you select a static analysis as the analysis type and then select Calculate Large Deformations in the Nonlinear Options area of the Static Analysis Definition dialog box. See Large Deformation Static Analysis Overview for a description of and requirements for large deformation static analysis. For a large deformation static analysis, select the following options on the Static Analysis Definition dialog box as indicated: • • • Constraints — Select a constraint set. Loads — Select a load set, unless you are using a constraint set with an enforced displacement. Nonlinear Options — Select Calculate Large Deformations. This option is only available for certain model and load types. If your model has contact regions, you must deselect the default option Include Contact Regions and then select Calculate Large Deformations. The following tabs are available on the dialog box when you select Calculate Large Deformations: • • • • Load Intervals Temperature Distribution (appears only for models with temperaturedependent material properties) Convergence Output 665 Structural and Thermal Simulation - Help Topic Collection Large Deformation Static Analysis Overview Description Use large deformation static analysis if you want to calculate geometrically nonlinear results. You may want to perform a linear static analysis first to determine whether geometrically nonlinear results are required. You may also want to perform a linear buckling analysis. If the load factor is greater than the critical buckling load factor for your model, the large deformation static analysis may either take a long time to converge, or may not converge to a solution. If you perform a buckling analysis that indicates your model will buckle, you can reduce run time for a large deformation static analysis by using a load that is less than the linear buckling load. Be aware that, in some cases, the results of linear static analysis and buckling analysis may not accurately predict what will actually occur in a large deformation static analysis. Note: Mechanica supports only certain types of loads in large deformation static analysis. Some loads may be deformation-dependent, such as pressure loads. Mechanica interprets material properties for large deformation static analysis according to a natural generalization of linear elasticity. and are converted to the Lame constants and , using the same formulas as used in linear elasticity. Stresses are calculated using the neo-Hookean material law, which depends linearly on and . For more information on neo-Hookean material, see Nonlinear Continuum for Finite Element Analysis, Javier Bonet and Richard D. Wood (Cambridge University Press: 1997). When you run a large deformation static analysis, you can use the Single-Pass Adaptive convergence method or perform a Quick Check. After you run the analysis, with full results selected for multiple load intervals, you can view the results at the various load intervals by animating the fringe plot. Mechanica reports Almansi strains for large deformation static analysis. Resultant measures are not currently available for this analysis type. Requirements • • • • • • • 1 constraint set 0 or 1 load set a 3D, 2D plane stress, or 2D plane strain model solid and mass elements only no links isotropic, linear elastic material properties only no temperature-dependent material properties See Constraint and Load Sets in Structural Analyses for more information. 666 Structural and Thermal Simulation To Create a Large Deformation Static Analysis 1. Create a new static analysis, if you have not already created one. On the Static Analysis Definition dialog box, the following items must be filled in: Name, Constraints, Loads, Convergence, and Output. 2. Select the nonlinear option Calculate Large Deformations. The Load Intervals tab becomes available. 3. To select load interval options, see To Select Load Interval Options for Large Deformation and Contact Analyses. 4. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. Contact Analysis In a contact analysis, Mechanica examines the effect of loads on contact regions. For details, see the description of and requirements for contact analyses. You must first select a static analysis type and then use the nonlinear option Include Contact Regions. For a contact analysis, select the following options on the Static Analysis Definition dialog box as indicated: • • • Constraints — Select a constraint set. Enforced displacements in spherical and cylindrical coordinate systems are not supported for contact analysis. Loads — Select a load set, unless you are using a constraint set with an enforced displacement. Nonlinear Options — Verify that the nonlinear option Include Contact Regions is selected. This option is available and selected by default only if your model has contact regions. Note that, because Mechanica does not support large deformation nonlinearity for contact analyses, the Calculate Large Deformations check box is inactive, and can only be reactivated if you deselect Include Contact Regions. The following tabs are available on the dialog box when you select Include Contact Regions: • • • • Load Intervals Temperature Distribution (appears only for models with temperaturedependent material properties) Convergence Output 667 Structural and Thermal Simulation - Help Topic Collection Contact Analysis Description Use contact analysis to observe how displacement, stresses, contact pressures, and/or measures affect the contact regions of your model. During a contact analysis, Mechanica monitors any changes to the surfaces of your model that are defined as contact regions. Mechanica also calculates the total contact area of all contact regions in your model and the maximum contact pressure over all contact regions. In a contact analysis, the relation between the load applied to the model and the resulting deformations and stresses is not linear. The contact area changes nonlinearly as the load increases, because the contact area depends on the deformation of the model: Contact analysis takes longer to run than linear static analysis because Mechanica must calculate results several times iteratively. See Contact Analyses in Design Studies for information on including contact analyses in different types of design studies. Contact Analysis Requirements You need to include the following items in a contact analysis: • • • 1 constraint set 0 or 1 load set 1 or more contact regions In addition, you must create measures if you want to see results for specific contact regions. You can select from the following measures: average contact pressure, maximum contact pressure, contact area, and contact load. 668 Structural and Thermal Simulation Note that Mechanica does not support contact analysis for models that include shells in the contact region. Also, Mechanica does not support large deformation nonlinearity for contact analyses. This means that the outward normals for the contact surfaces should not rotate more than 5 during analysis. See Constraint and Load Sets in Structural Analyses for more information. To Create a Contact Analysis Before carrying out a contact analysis, you must create contact regions in your model. If you want to see results for specific regions, you must define measures for your model. You can then use contact analysis to find out how displacement, stresses, contact pressures, and/or measures affect the contact regions. 1. Create a new static analysis, if you have not already created one. On the Static Analysis Definition dialog box, the following items must be filled in: Name, Constraints, Loads, Convergence, and Output. 2. Make sure the nonlinear option Include Contact Regions is selected. The Load Intervals tab becomes available. 3. To select load interval options, see To Select Load Interval Options for Large Deformation and Contact Analyses. 4. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. Modal and Prestress Modal Analyses Modal and prestress modal analyses both examine the modal behavior of your model. You can use modal analysis to calculate the natural frequencies and mode shapes of your model. You can use prestress modal analyses to apply results from a static analysis and then calculate the natural frequencies and mode shapes of your model. For a description of and requirements for each analysis type, see Modal Analysis Overview and Prestress Modal Analysis Overview. These items appear on the Modal Analysis Definition and Prestress Modal Analysis Definition dialog boxes: • • Constrained — Select this option if you want to include a constraint. Then select a constraint set from the Constraints list. Unconstrained — Select this option if you do not want to include a constraint. 669 Structural and Thermal Simulation - Help Topic Collection • With Rigid Mode Search — Use this option to include a search for rigid body modes. The following tabs appear on the Modal Analysis Definition and Prestress Modal Analysis Definition dialog boxes: • • • • • Modes Previous Analysis (appears only on the Prestress Modal Analysis Definition dialog box) Temperature Distribution (available on the Modal Analysis Definition dialog box only for models with temperature-dependent material properties) Convergence Output Modal Analysis Overview Description Use modal analysis to calculate the natural frequencies and mode shapes of your model. You can also see the response to the natural frequencies of your model when it is subjected to time-dependent and/or oscillatory/vibration loads by running any dynamic analysis: dynamic time, dynamic frequency, dynamic random, or dynamic shock. See Units of Modal Frequency Results to find out how Mechanica reports frequency results. Requirements • 0 or 1 constraint set See Constraint and Load Sets in Structural Analyses for more information. To Create a Modal Analysis 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Modal from the File menu. The Modal Analysis Definition dialog box appears. 3. Enter a name for the analysis. A description is optional. 4. Select Constrained and choose a constraint, or select Unconstrained. 5. If you want to include a rigid mode search, select the check box option. 670 . Structural and Thermal Simulation 6. Click the following tabs on the dialog box to select additional options for the modal analysis: o Modes o Temperature Distribution (available only for models with temperature-dependent material properties) o Output o Convergence 7. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. Prestress Modal Analysis Overview Description Use results from a static analysis to calculate the natural frequencies and mode shapes of your model. For example, in rotating machinery, such as a turbine blade, you may want to run a prestress modal analysis after a static analysis to get more detailed information about the applied loads and the stiffening and weakening of those loads. See Units of Modal Frequency Results to find out how Mechanica reports frequency results. See Spin Softening to find out how Mechanica automatically compensates for the effect of relative motions that can occur during prestress modal analyses when a centrifugal load is present. Requirements • • • 0 or 1 constraint set 1 static analysis 3D model See Constraint and Load Sets in Structural Analyses for more information. To Create a Prestress Modal Analysis You must run a static analysis before you use this procedure. Mechanica uses the results from the modal analysis to calculate the prestress modal analysis. 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Prestress>Modal from the File menu. . 671 Structural and Thermal Simulation - Help Topic Collection The Prestress Modal Analysis Definition dialog box appears. 3. 4. 5. 6. Enter a name for the analysis. A description is optional. Select Constrained and choose a constraint, or select Unconstrained. If you want to include a rigid mode search, select the check box option. Click the following tabs on the dialog box to select additional options for the modal analysis: o Modes o Previous Analysis o Output o Convergence 7. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. Buckling Analysis You can use a buckling analysis to calculate the critical load at which a structure will buckle, as well as the model's stresses, strains, and deformations at the onset of buckling. In a buckling analysis, Mechanica calculates a buckling load factor (BLF) and mode shape. See Buckling Analysis Overview for a more detailed description of and requirements for buckling analyses. These items appear on the Buckling Analysis Definition dialog box: • • • Previous Analysis Convergence Output Buckling Analysis Overview Description In a buckling analysis, Mechanica calculates: • a buckling load factor (BLF). The BLF is the magnification factor by which the loads applied in a previously specified static analysis would have to be multiplied to produce the critical buckling load. First define a static analysis, in which Mechanica calculates the stress stiffening of your model due to the applied forces. You can then define a buckling analysis, which Mechanica uses to calculate the model's elastic stiffness due to geometry and material properties. Mechanica uses the two solutions to calculate the BLF. the mode shape for each buckling mode you request • 672 Structural and Thermal Simulation The buckling analysis uses the constraint set specified in the previous static analysis. Mechanica automatically calculates all predefined measures valid for a static analysis. Mechanica buckling analysis is a linear eigenvalue bifurcation instability analysis as described in The Finite Element Method, Third Edition, by O.C. Zienkiewicz, pages 513–514. Large displacement or non-linear buckling investigations may produce significantly different results, depending on the type of model and loads being examined. A Mechanica buckling analysis will typically overestimate the buckling load in comparison to real world tests. Look at the mode shape and BLF in results. For stress results, you should use the static analysis results. For stress results at the area of buckling, multiply the stresses from the static analysis with the buckling load factor. See Buckling Load Factor and Optimization Studies for information on using the BLF as a limit in an optimization study. Requirements • • 1 static analysis a 3D model To Create a Buckling Analysis 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Buckling on the File menu. The Buckling Analysis Definition dialog box appears. 3. Enter a name for the analysis. A description is optional. 4. Click the following tabs on the dialog box to select additional options for the buckling analysis: o Previous Analysis o Convergence o Output 5. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. . 673 Structural and Thermal Simulation - Help Topic Collection Fatigue Analysis Use fatigue analysis to establish whether your model is susceptible to fatigue damage when subjected to cyclic loading. The solver technology integrated with Mechanica fatigue analysis is provided by nCode, Inc. Fatigue analysis requires a Fatigue Advisor license from PTC. Before defining a fatigue analysis, you must first define a static analysis. You also must assign fatigue properties to the materials of your model in order to get valid fatigue results. See Fatigue Analysis Overview for a detailed description of and requirements for fatigue analysis. The following tabs appear on the Fatigue Analysis Definition dialog box: • • Load History Previous Analysis Below the tabs, the following items appear in the Output area: • • Plotting Grid Calculate factor of safety Fatigue Analysis Overview Description Fatigue analysis establishes whether your model is susceptible to fatigue damage when subjected to a varying load. You can use constant amplitude loading for situations where the stress cycles are regular, such as a rotating shaft operating at a constant speed. For situations where the stress cycles are random, you can define a variable amplitude loading pattern for your model. You must first define a static analysis before you can define a fatigue analysis. The stress results from the static analysis are multiplied by the load factors you specify for the fatigue analysis to find the loading variation for one life cycle. Fatigue analysis calculates the following: • • Log Life — the estimated number of cycles until your model breaks. Because of the exponential nature of fatigue, it is useful to express life as a logarithm. Log Damage — the ratio between accumulated fatigue cycles and the total number of cycles to failure. A value greater than unity indicates failure. A value of 0.5, for example, represents a loss of 50% in the useful life of the model. Because of the exponential nature of fatigue, it is useful to express the damage ratio as a logarithm. Factor of Safety — the permissible factor of safety on the input load. When the fatigue life calculated for your model is greater than the target design life, the software carries out a back calculation to determine a permissible factor • 674 Structural and Thermal Simulation • • of safety on the input load. This represents the extent to which the amplitude of the load can be increased without compromising the target design life. If you want the software to calculate the factor of safety, select the check box in the Output area at the bottom of the Fatigue Analysis Definition dialog box. Confidence of Life — the ratio between the calculated life and the target design life. Because of the statistical nature of fatigue, the greater the confidence the better. Values below unity indicate failure. Values greater than 3.0 usually reflect an adequate confidence of achieving the desired target life. You can display Confidence Of Life results in a tricolored fringe display to give an overall view of where the model will break first and where the model will last for a greater number of cycles. Red signifies a confidence of life from 0 cycles to the number of cycles entered for desired endurance on the analysis dialog box. Yellow signifies a confidence of life that ranges from the number of cycles for desired endurance to 3 times that number. The difference between these numbers is considered the marginal life. Green signifies any number of cycles over the marginal life. For background information on fatigue and details about the methodology used in fatigue analysis, see the online document Understanding Fatigue Analysis. Fatigue Advisor is optimized so you can obtain a rapid indication of whether a design is sensitive to fatigue without having to provide the full range of input normally required to solve this problem. The software accomplishes this by asking for input that is relatively straightforward to obtain and by internally setting very conservative defaults for input that you do not directly provide. Advanced fatigue users may want to alter these defaults to examine less conservative scenarios. Requirements • • • • 3D solid or shell model isotropic materials only 1 static analysis fatigue properties for the materials To Create a Fatigue Analysis 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Fatigue from the File menu. The Fatigue Analysis Definition dialog box appears. 3. Enter a name for the analysis. A description is optional. 4. Click the following tabs on the dialog box to select options for fatigue analysis: o Load History 675 . Structural and Thermal Simulation - Help Topic Collection o Previous Analysis 5. Select the density of the Plotting Grid. 6. Select the Calculate factor of safety check box if you want the software to make this calculation. This calculation adds significantly to the total analysis runtime. 7. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. To Use Previous Analysis Results in a Fatigue Analysis You use the results of a previously defined or previously run static analysis to calculate a fatigue analysis. This procedure assumes you are in the Fatigue Analysis Definition dialog box. 1. Click the Previous Analysis tab on the analysis dialog box. 2. If you want to use the results from a previously run static analysis, select the check box Use Static Analysis Results From Previous Design Study. If you do not select this check box, Mechanica will run a static analysis as part of running your fatigue analysis. 3. Select the following items to include in your fatigue analysis: o o o Design Study (if applicable) Static Analysis Load Set To Define the Load History for a Fatigue Analysis This procedure assumes you are in the Fatigue Analysis Definition dialog box: 1. Click the Load History tab on the Analysis dialog box. 2. Enter in the Desired Endurance field the number of life cycles you want to include in the analysis. 3. Select a loading type—Constant Amplitude or Variable Amplitude. Different options appear on the tab depending on the loading type you select. 4. If you selected Constant Amplitude, select one of the following options for Amplitude Type: o o o 676 Peak–Peak Zero–Peak User-Defined Structural and Thermal Simulation 5. If you selected User-Defined in step 4, enter values for Min Load Factor and Max Load Factor. 6. If you selected the loading type Variable Amplitude in step 3, enter a load factor for each row in the table to define the amplitude curve for one life cycle. You can use the Add Row button to add rows to the table, or the Delete and Clear All buttons to remove rows. You also can import the load factor data from a text file directly into the table. Click the Import button and then select the file from the Open File dialog box. To Select Output Options for a Structural Analysis This procedure assumes you are in the dialog box for creating one of these analysis types: static, prestress static, modal, prestress modal, buckling, contact, or large deformation static. 1. Click the Output tab on the analysis dialog box. 2. Select the quantities you want Mechanica to calculate: Stresses, Rotation, Reactions, and Ply Stresses (not available for contact analysis). 3. Select the density of the plotting grid. To Select Load Interval Options for Large Deformation and Contact Analyses This procedure assumes you are in the Static Analysis Definition or Prestress Static Analysis Definition dialog box and have selected Calculate Large Deformations or Include Contact Regions. 1. 2. 3. 4. Click the Load Intervals tab on the analysis dialog box. Select the number of intervals for your analysis. Enter a load factor for each load interval or use the default factors. If you are creating a large deformation static analysis, select the check boxes next to the load intervals for which you want to save full results. To Set Convergence for a Structural Analysis This procedure assumes you are in the dialog box for creating one of these analysis types: static, prestress static, modal, prestress modal, buckling, contact, or large deformation static. 1. Click the Convergence tab on the analysis dialog box. 2. Select the convergence method for your analysis—Multi-Pass Adaptive, Single-Pass Adaptive, or Quick Check. 677 Structural and Thermal Simulation - Help Topic Collection 3. If you are creating a contact analysis and selected Single-Pass Adaptive convergence, you have the option to select Localized Mesh Refinement. Note: If you selected Multi-Pass Adaptive, continue with the following steps. 4. Enter a minimum and maximum polynomial order. 5. Enter a convergence percentage. 6. Select the quantities you want Mechanica to use to calculate convergence. For a description of the convergence quantities, see: o o o quantities for static, prestress static, contact, and large deformation analyses quantities for modal and prestress modal analyses quantities for buckling analysis To Select Temperature Distribution for an Analysis This procedure assumes you are in the dialog box for creating one of these analysis types: static, modal, contact, or large deformation static. 1. Click the Temperature Distribution tab on the analysis dialog box. 2. Select the temperature distribution for the analysis—Uniform, MecT (MecThermal), or ExtT (External Temperatures). 3. If you selected Uniform, enter a temperature in the Temperature field. 4. If you selected MecT, select a previously defined thermal analysis. 5. If you selected a steady thermal analysis in step 4, select a load set, or if you selected a transient thermal analysis, select a time step from the analysis. 6. If you want to use the results from a previously run design study, select the Use temperatures from previous design study check box. 7. If you selected the check box, you must select the name of the design study or analysis and the load set you want to use. 8. If you selected ExtT for temperature distribution, click the Browse button to select the external temperature field file you want to use from the Open dialog box. The name of the file you selected appears in the ExtT field. To Use Previous Analysis Results in a Prestress Analysis This procedure assumes you are in the Prestress Static Analysis or Prestress Modal Analysis dialog box. 1. Click the Previous Analysis tab on the analysis dialog box. 2. If you want to use the results from a previously run static analysis, select the Use Static Analysis Results From Previous Design Study check box. 678 Structural and Thermal Simulation If you do not select this check box, Mechanica will run a static analysis as part of running your prestress analysis. 3. Select the following items to include in your prestress analysis: o o o Design Study (if applicable) Static Analysis Load Set 4. If you want to multiply the stress results from a previous static analysis, enter a Load Scale Factor. 5. If you are creating a prestress static analysis, you have the option to select the Combine Results With Results From Previous Static Analysis check box. To Use Previous Analysis Results in a Buckling Analysis You use the results of a previously defined or previously run static analysis to calculate a buckling analysis. This procedure assumes you are in the Buckling Analysis Definition dialog box. 1. Click the Previous Analysis tab on the analysis dialog box. 2. If you want to use the results from a previously run static analysis, select the check box Use Static Analysis Results From Previous Design Study. If you do not select this check box, Mechanica will run a static analysis as part of running your buckling analysis. 3. Select the following items to include in your buckling analysis: o o o Design Study (if applicable) Static Analysis Load Set 4. Enter the number of buckling modes you want Mechanica to calculate. To Select Mode Options for a Modal Analysis This procedure assumes you are in the Modal Analysis Definition or Prestress Modal Analysis Definition dialog box. 1. Click the Modes tab on the analysis dialog box. 2. Select one of these mode options: Number Of Modes or All Modes In Frequency Range. 3. If you selected the Number Of Modes option, enter the number of modes you want to use for the analysis. 4. Enter the minimum frequency of the modes. 679 Structural and Thermal Simulation - Help Topic Collection 5. If you selected All Modes In Frequency Range, enter the maximum frequency to define the top end of the frequency range. Convergence Options for Structural Analyses These items appear on the Convergence tab on the dialog boxes for static, prestress static, modal, prestress modal, large deformation static, contact, and buckling analyses: • Method — Select a method for calculating results and determining their accuracy. Different items appear on the tab, depending on the convergence method you select. For the Multi-Pass Adaptive convergence method • • • Polynomial Order — Enter a minimum and maximum polynomial order. Limits — Enter the Percent Convergence. Converge on — Select the quantities you want to use. For a description of the convergence quantities for each type of analysis see: o o o Convergence Quantity for Static, Prestress Static, Large Deformation Static, and Contact Analyses Convergence Quantity for Modal and Prestress Modal Analyses Convergence Quantity for Buckling Analyses For the Single-Pass Adaptive convergence method • Localized Mesh Refinement (contact analysis only) — Select this option to improve the accuracy of contact pressure results. For the Quick Check method, the tab displays the polynomial order of 3. Previous Analysis Options for Buckling Analysis These items appear on the Previous Analysis tab on the Buckling Analysis Definition dialog box: • Use Static Analysis Results From Previous Design Study — Select this option to use results from a previously run static analysis when you include a static analysis in a buckling analysis. If this option is not selected, Mechanica runs the static analysis as part of the buckling analysis. Design Study — Select a design study to include in the buckling analysis if you selected the option Use Static Analysis Results From Previous Design Study. Static Analysis — Select a static analysis to include in the buckling analysis. Load Set — Select a load set to include in the buckling analysis. • • • 680 Structural and Thermal Simulation • Number of Buckling Modes — Enter the number of buckling modes that you want Mechanica to calculate for this analysis. Note: When you include a buckling analysis in an optimization study, Mechanica tracks only the first mode, since that mode will cause failure first. Buckling Load Factor and Optimization Studies If you have defined an optimization study with one limit specifying that a BLF is greater than some positive value and an additional limit specifying that the same BLF is less than zero, Mechanica interprets this as BLF > N OR BLF < 0, where N is the positive value. If for any parameter values all the BLFs become less than zero, the study will continue, and the upper limit BLF > N is ignored. If for any parameter values any BLF is greater than zero, the lower limit BLF < 0 is ignored, and the optimizer will try to drive the BLF above the upper limit. Previous Analysis Options for Prestress Analyses These items appear on the Previous Analysis tab on the Prestress Static Analysis Definition and Prestress Modal Analysis Definition dialog boxes: • Use Static Analysis Results From Previous Design Study — Select this option to use results from a previously run static analysis when you include a static analysis in a prestress analysis. If this option is not selected, Mechanica runs the static analysis as part of the prestress analysis. Design Study — Select a design study to include in the prestress analysis if you selected the option Use Static Analysis Results From Previous Design Study. Static Analysis — Select a static analysis to include in the prestress analysis. Load Set — Select a load set to include in the prestress analysis. Load Scale Factor — Enter a factor to multiply stress results from the previous static analysis for a prestress analysis. Combine Results With Results From Previous Static Analysis (available for prestress static analysis only) — Select to combine results from a previous static analysis with results from a prestress static analysis. • • • • • 681 Structural and Thermal Simulation - Help Topic Collection Temperature Distribution Options These items are available on the Temperature Distribution tab on the dialog boxes for static, large deformation static, contact, or modal analyses only if the model has temperature-dependent material properties. • Temperature Distribution — Specify temperature distribution based on a uniform temperature, the results of a thermal analysis, or an external temperature field. Different items appear on the tab, depending on the temperature distribution you select. Temperature — Enter a temperature if you selected Uniform for Temperature Distribution. Use Temperatures from Previous Design Study — You can use results from a previously run thermal analysis if you selected MecT for Temperature Distribution. ExtT — Select an external temperature field file if you selected ExtT for Temperature Distribution. • • • Strategy: Using Contact Analysis Effectively If you encounter problems using contact analysis, consider the following questions: • Is the model properly constrained against motion tangential to the contact surfaces? Note that contact regions are frictionless and provide support in the normal direction only. • Is there a large displacement in the solution? Note that the tolerance for interpenetration is 5% of the maximum average normal displacement in the contact region. The maximum average normal displacement is based on the displacement in the normal direction, as measured at sample points on the two opposite surfaces in the contact region. • • Were any contact regions missed? In terms of mesh refinement, how large are the elements in the vicinity of the contact region? For accurate results in the vicinity of the contact, restrict the size of the elements adjacent to the contact zone by seeding that area with datum points. These elements should not be much larger than the zone. If Mechanica detects this size discrepancy, the following warning message will appear in the summary file: Contact area is small in comparison to size of adjacent element edges for one or more contact regions. If you need pressure results near the contact regions, use 682 Structural and Thermal Simulation single-pass adaptive convergence and select Localized Mesh Refinement. Strategy: Determining the Presence of a NonLinear Problem When using a program that is based on a linear assumption, you will find that doubling a load causes displacements and stresses to double. This technique works well for a cantilevered beam that displaces very little in comparison to its length. On the other hand, if you consider a strongly bent fishing rod, the bent rod responds to an incremental load much differently than the originally straight rod responds. So this problem exhibits geometric non-linearity. To determine whether a given problem is non-linear, follow the steps below: 1. Build the model, apply loads and constraints, and solve for displacements. 2. Build a similar model with geometry that corresponds to the deformed shape of the first model. Load and constrain the second model and solve for displacements. Note: For more complicated models, this is not a trivial operation. Whenever possible, try simplifying the model in order to perform the investigation. 3. If the two sets of displacements are in good agreement, then the problem was linear. If however, the two sets of displacements are not reasonable ratios of each other, then the problem is non-linear. As an example, consider a circular aluminum plate, 1 mm thick, 200 mm in diameter, pinned at its circumference and subject to a uniform pressure load. Pressure Load 0.005 MPa Maximum Displacement of Initially Flat Plate 4.58 mm Maximum Displacement of Initially Curved Plate 0.026 mm 0.0001 MPa 0.0916 mm 0.0888 mm For the plate subject to a pressure load of 0.005 MPa, results are non-linear. To make physical sense, the displacement of the initially curved plate should not be 200 times less than that of the initially flat plate. 683 Structural and Thermal Simulation - Help Topic Collection Results for the plate subject to a pressure load of 0.0001 MPa show displacement results for the initially curved plate just 3% less than for the initially flat plate. Thus, at this very small pressure, linear analysis is a fairly good approximation. For the response to be linear, the general rule for plates and shells is that the deflection should be less than the thickness. Contact Analyses in Design Studies You can run a standard, global sensitivity, or optimization design study with a contact analysis. Be aware, however, that you should not use contact measures for the goal or limits of your optimization. To obtain accurate contact measures when running an optimization study, you should probably run a standard study with the parameters set to the optimized values. Plotting Grid When you define an analysis, you specify the refinement of the plotting grid over which Mechanica reports displacement and stress results for static and modal analyses and temperature gradient, and flux results for steady-state thermal analyses. The value you specify determines the number of intervals along each edge of each element that Mechanica uses to create plotting grids. Mechanica calculates quantity values at the intersections of grid lines. Use the following strategies for specifying the plotting grid refinement: • Enter a number from 2 to 10 to determine the level of detail Mechanica uses to report results of the analysis. The default plotting grid refinement of 4 is often adequate. But when you find from a previous run that stresses or fluxes vary rapidly over a single element, specify a higher refinement to more accurately capture the peak results. • For a higher plotting grid refinement, the engine requires a greater amount of computation time and a significantly greater amount of disk space for its output files. In addition, viewing results is more time-consuming. Note: If you enter a higher number, the grid will be finer, and Mechanica reports values from more locations on each element. At lower numbers, Mechanica takes less time to calculate results, and the data takes up significantly less space. The default is 4. • For models consisting primarily of beams, set the plotting grid refinement to 10 for the highest possible resolution. For these problems, the overhead of the finer plotting grid is negligible. Mechanica reports precise results for each grid intersection point and interpolates these values to show results elsewhere. 684 Structural and Thermal Simulation Calculate Quantities for Analysis You can direct Mechanica to calculate any or all of the following: • Stresses — Directs Mechanica to calculate stresses. If you do not need stress results, especially for modal and dynamic analyses, you can save disk space by deselecting this item. This also results in dramatically reduced analysis time. Rotations — Directs Mechanica to calculate the rotation about each WCS axis over the entire model. Mechanica never calculates rotations if your model consists only of solid elements, even if this item is selected. Rotations are always zero for these element types. Reactions — Directs Mechanica to calculate the reaction forces and moments present at constrained points and edges. Mechanica does not report reaction data at constraints associated with a UCS. Ply Stresses — Directs Mechanica to calculate the stress on each ply of a laminate. This option only appears if your model has laminate shell properties and becomes available when you select Stresses. The Ply Stresses option is not available for contact analyses. • • • You cannot access results for any quantity you deselect here. For static, prestress static, large deformation static, contact, and buckling analyses, Mechanica does calculate all stress and rotation measures even if you do not select Stresses and Rotations on the analysis dialog box. But you cannot access the same results for measures that you can when you select Stresses, Rotations, and Reactions. Number of Load Intervals You can specify the load intervals at which Mechanica calculates results, enabling you to see how measure values vary with the load. If Mechanica allowed loads on design parameters, this would be equivalent to performing a global sensitivity study with a design parameter on the load. Enter or select a number from 1 to 99. The recommended range is between 1 and 20. To reduce run time, enter a smaller number of load intervals. If you are concerned only with the stress and deformation of your model with the load fully applied, you should use the default of 1. This setting does not affect convergence of the analysis. Note: For global sensitivity studies, the number of load increments is always 1, no matter what you enter here. Mechanica displays the load intervals in a table and assigns a number to each interval. 685 Structural and Thermal Simulation - Help Topic Collection Enter a load factor in the field to the right of each load interval or use the default factors. The first load factor is automatically set to 0, and the last load factor is set to 1. The load factors must be numbers that increase from 0 to 1. Mechanica evaluates measures at all load intervals and calculates full results at specified intervals. Number of Modes, All Modes in Frequency Range Select one of these items to determine which modes Mechanica takes into account when calculating results for the analysis: • Number of Modes — Select this option to specify the number of modes you want Mechanica to calculate above a specified minimum frequency. You can enter or select a number from 1 to 9999 in the Number Of Modes field. If you select Rigid Mode Search, Mechanica includes rigid modes in the number of modes it reports. this case, add the number of rigid modes to the number of non-rigid modes you want reported, so you get results for all the modes you want. For example, a 3D model with no constraints has six rigid body modes. If you want four non-rigid modes, you should enter 10 for Number Of Modes. • All Modes in Frequency Range — Select this option if you want Mechanica to report all modes within a frequency range. Use Minimum Frequency and Maximum Frequency to define the range. Min Frequency, Max Frequency Use these items to enter specific frequencies: • Minimum Frequency — Mechanica reports modes at or above the frequency you enter here. The number of modes Mechanica reports depends on whether you selected Number Of Modes or All Modes In Frequency Range. Enter a value greater than or equal to 0. • Maximum Frequency — If you selected All Modes In Frequency Range, this value determines the upper end of the frequency range. Enter a positive value greater than the Minimum Frequency. 686 Structural and Thermal Simulation Load Interval Options for Large Deformation and Contact Analyses These items are available on the Load Intervals tab on the Static Analysis Definition dialog box when you select either Calculate Large Deformations or Include Contact Regions: • • • • • • Number of Intervals — Enter or select a number of load intervals for your analysis. Full Results — For large deformation static analysis, select the check boxes next to the load intervals for which you want to save full results. For contact analysis, full results are available only for the last interval. Clear — Click this button to delete all load factor entries. Space Equally — Click this button to equally space the load factors between 0 and 1 for the intervals. (Select All) — Click this button if you want full results for all load intervals. (Deselect All) — Click this button if you do not want full results for all load intervals. Loading Types for Fatigue Analysis You can input load history data for fatigue analysis using one of the following loading types: • Constant Amplitude — Use this option for models with constant amplitude loading. This is the easiest way to input load history data and is selected by default. Constant Amplitude provides three Amplitude Type options: o o o Peak–Peak — Uses a Min Load Factor of –1.0 and a Max Load Factor of 1.0. Zero–Peak — Uses a Min Load Factor of 0 and a Max Load Factor of 1.0. User-Defined — Allows you to enter values for the Min Load Factor and Max Load Factor. • Variable Amplitude — Use this option for models with variable amplitude loading. You can define the variation of the amplitude by manually entering load factors to specify the datum points of the amplitude curve. You can enter up to 100 load factors. Use the following buttons to modify the table that defines the variation of the amplitude. o Add Row — Adds numbered rows to the table. When you click Add Row, the Enter Rows dialog box appears. In the Start At field, enter the row number where you want to begin adding rows. In the Num Rows field, enter the number of rows you want to add. When you click OK, Mechanica adds the new rows and preserves any load factors you entered in rows above or below the new rows. 687 Structural and Thermal Simulation - Help Topic Collection o o o Delete — Deletes rows from the table. When you click Delete, you can use the Enter Rows dialog box to specify a Begin Row and End Row. When you click OK, Mechanica deletes all rows numbered from the Begin Row through the End Row. Clear All — Click this button to delete all rows. Import — Click this button to import the load factor data from a text file into the table. You can import an unlimited number of cycles from a text file. Previous Analysis Options for Fatigue Analysis These items appear on the Previous Analysis tab on the Fatigue Analysis Definition dialog box: • • • • Use Static Analysis Results from Previous Design Study — Select this option to use results from a previously run static analysis. If this option is not selected, Mechanica runs the static analysis as part of the fatigue analysis. Design Study — If you selected the option Use Static Analysis Results From Previous Design Study, select the design study that includes the previously run static analysis. Static Analysis — Select the static analysis that you want to use. Load Set — Select a load set. Output Options for Structural Analyses These items appear on the Output tab on the dialog boxes for static, prestress static, modal, prestress modal, large deformation static, contact, and buckling analyses: • • Calculate — Select the quantities Mechanica will calculate. Plotting Grid — Specify the density of the grid that determines where Mechanica calculates results. Sample Uses for Prestress and Buckling Analyses You can use the following types of models for prestress or buckling analyses: Analysis Type Prestress Static Prestress Modal Type of Model pretension cable rotating machinery Example ski lift turbine blade 688 Structural and Thermal Simulation Analysis Type Buckling Type of Model thin sections under compression Example bulkheads Model Temperature Distribution Use this item to specify temperature distribution for a static, large deformation static, contact, or modal analysis if your model has temperature-dependent material properties. If you selected a load set with a temperature load for a static analysis, you do not enter anything here. The dialog box displays temperature load information instead. For other static analyses and all modal analyses, you can select one of these options: • • Uniform — Apply a uniform temperature distribution over the model. Enter the temperature in the Temperature field below this option menu. Mec/T — Apply a thermal load based on a temperature field determined by a steady or transient thermal analysis. You must already have defined a valid steady or transient thermal analysis. When defining a transient thermal analysis for this purpose, you must select the Temp Load option for various time steps in order to calculate the thermal load results you want to apply to the static or modal analysis. The dialog box displays the name of a steady thermal analysis and a load set, or a transient thermal analysis and a time step from the analysis. If you have multiple analyses, load sets, or time steps, you can select the ones you want to use. Mechanica runs the thermal analysis you select before running the static or modal analysis. You can also select Use temperatures from previous design study if you want to use the results of a previously run thermal analysis. • Ext/T — Import an externally calculated or measured temperature field as a temperature load. You must already have created a Pro/FEM Neutral File to import an external temperature load. Click the Browse button and select an external temperature field file from the Open dialog box. 689 Structural and Thermal Simulation - Help Topic Collection Use Temperatures from Previous Design Study Use this option in these cases: • • if you select MEC/T for Model Temperature Distribution if you want to use a previously run thermal analysis as the source for the thermal load If you select this item, Mechanica takes the temperatures for the load you are creating from a thermal analysis that you run before you run the static or modal analysis. The names of a design study, analysis, and load set appear on the dialog box. If you have multiple studies, analyses, or load sets, you can select the ones you want to use. Note: In a sensitivity or optimization design study, Mechanica automatically runs the thermal analysis at each parameter setting, even if you select Use Temperatures From Previous Design Study. Use Static Analysis Results From Previous Design Study For prestress, buckling, and fatigue analyses, Mechanica uses the results of a static analysis to calculate the prestress, buckling, or fatigue analysis. You can include the static analysis in one of these ways: • Use results from a previously run static analysis. Select the option Use Static Analysis Results From Previous Design Study. The dialog box displays the name of a standard design study, static analysis, and load set. If you have multiple studies, analyses, or load sets, you can select the ones you want to use. Note: For sensitivity and optimization studies, Mechanica always reruns the static analysis at each parameter setting, even if you select Use Static Analysis Results From Previous Design Study. • Have Mechanica run the static analysis as part of running the prestress, buckling, or fatigue analysis. Clear the option Use Static Analysis Results From Previous Design Study. 690 Structural and Thermal Simulation The dialog box displays the name of a static analysis and load set from that analysis. If you have multiple analyses or load sets, you can select the ones you want to use. Load Scale Factor for Prestress Analyses Enter the value by which Mechanica multiplies the stress results from the previous static analysis before using them in the prestress analysis. You can use this option to rerun the prestress analysis with an amplified or decreased prestress without forcing Mechanica to rerun the included static analysis. Combine Results with Results from Previous Static Analysis Use this option to combine results from the included static analysis with the results of a prestress static analysis. The engine adds the stresses and displacements from the previously run static analysis to those from the current prestress static analysis when it calculates results for the prestress analysis. The engine multiplies the previous static results by the Load Scale Factor before adding them to the prestress analysis results. Use caution when interpreting combined results since there are no restrictions on loading and constraint sets used for the prestress and previous static analysis. Units of Modal Frequency Results Units of modal frequency shown in results are always cycles per unit of time. The units of time are affected by the force/length/time units you used to define the model. Mechanica never reports modal frequency in terms of radians per unit of time. Load History Options for Fatigue Analysis These items appear on the Load History tab on the Fatigue Analysis Definition dialog box: • • Life — In the Desired Endurance field, enter the number of life cycles for which you want your part to last. Loading — Select Constant Amplitude or Variable Amplitude for the loading type. Different options appear on the tab depending on which loading type you select. 691 Structural and Thermal Simulation - Help Topic Collection Spin Softening For prestress modal analyses, Mechanica automatically compensates for the effect of relative motions when a centrifugal load is present on a model. The software adjusts the stiffness matrix to account for this effect, which is referred to as spin softening. The spin softening modification term includes only derivatives of centrifugal loads that are due to angular velocity, and those with displacements. It does not include derivatives of centrifugal loads that are due to angular acceleration, nor does it affect moment terms for beams or shells, or derivatives due to rotations. Note: Springs are allowed in prestress analysis, but Mechanica does not compute stress-stiffness effects for springs. For a prestress modal analysis on a model with centrifugal loads, a spring, and a mass, the system stiffness decreases due to spin softening, and there is no stress-stiffening for the spring. Mode Options for Modal and Prestress Modal Analyses These items appear on the Modes tab on the Modal Analysis Definition and Prestress Modal Analysis Definition dialog boxes: • • • • • Number of Modes (option button) — Use to calculate a specific number of modes above the minimum frequency. All Modes in Frequency Range — Use to calculate all modes within a frequency range. Number of Modes (field) — Enter the number of modes you want to calculate. Minimum Frequency — Set the minimum frequency. Maximum Frequency — Set the maximum frequency to define a frequency range. Strain Measures in Large Deformation Static Analysis For large deformation static analysis, Mechanica reports Almansi engineering strain. In the limit where deformations are small, this is equivalent to strain reported for linear static analysis. Strain measures for uniaxial strain are defined as follows, where l is the final length and L is the initial length. Note that all are equivalent in the limit where the change in length is small. Linear strain 692 Structural and Thermal Simulation Almansi strain Green strain The Almansi strain tensor e can be defined using the deformation gradient tensor F and the left Cauchy-Green tensor b, as follows: The components of strain reported by Mechanica are the engineering strains gij, defined as follows: gij = eij , where i = j gij = 2eij , where i j Load Types in Large Deformation Static Analysis This table shows which load types you can use in a large deformation static analysis: Load Type Point Curve/Edge Surface/Face Supported Yes Yes Yes Details Deformation-independent load Distribution must be Total Load or Total Load at Point. For Total Load distribution, the variation must be Uniform or Interpolated Over Entity. Beam idealizations are not supported. Shell idealizations are not supported. Spring idealizations are not supported. Beam No Shell No Spring No Bearing No 693 Structural and Thermal Simulation - Help Topic Collection Centrifugal Gravity Pressure Yes Yes Yes Deformation-independent load Variation must be Uniform or Interpolated Over Entity. Magnitude will remain constant but direction may change. Direction will always be parallel to the deformed normal. Temperature No Adjusting Cyclic Material Properties for Fatigue By default, Fatigue Advisor estimates cyclic material properties from the type of material you specified and its ultimate tensile strength. However, this is purely an approximation. If you want to increase the accuracy of your analysis, you can use an ASCII file to enter specific cyclic material properties. To do so, use the sim_fatigue_external_matdata config.pro option. If you set the above option, you need to create and assign a material to your model in Mechanica. You then assign your ASCII file the same name as the material you created and give the file a .mat extension. You place this file in the same directory as your .prt or .asm file. Mechanica will use this file to obtain the model material during analysis. For additional information, visit Technical Support at www.ptc.com. Adjusting the Mean Stress Parameter for Fatigue Fatigue Advisor allows you to indicate whether you want to apply mean stress correction during analysis through the use of configuration options. By default, Fatigue Advisor calculates mean stress correction on a node-by-node basis using three correction methods—Smith-Topper-Watson, Morrow, or no mean stress correction. The software determines which of these methods generates the worst case and reports those results. You can change these defaults using two configuration options: • • SIM_FATIGUE_MEAN_STRESS config.pro option — Use this option to indicate whether you want Fatigue Advisor to apply mean stress correction. The default state for this option is YES. SIM_FATIGUE_MEAN_STRESS_METHOD config.pro option — Use this option to indicate the method Fatigue Advisor should apply—Smith-WatsonTopper, Morrow, or Worst. As mentioned, the default state for this option is 694 Structural and Thermal Simulation WORST. Note that the software only checks the setting for this option if sim_fatigue_mean_stress is set to YES. If you decide to set either of these options to a state other than the default, you should do so based on correlation with test data. Adjusting the Material Confidence Level for Fatigue By default, Fatigue Advisor sets the material confidence level to 90%. This default is more conservative than the confidence levels used in other fatigue modeling tools. Thus, if you want to correlate Fatigue Advisor test results with a test sample obtained using other software, you should reset the Fatigue Advisor default to 50%. To do so, use the sim_fatigue_confidence_level config.pro option. Advanced Tuning for Fatigue Advisor Mechanica Fatigue Advisor is a tool that lets you determine the fatigue life of your model. Fatigue Advisor is designed so novice fatigue users can get quick feedback on whether a design is sensitive to fatigue without having to provide all the input normally required. Fatigue Advisor does this by asking for input that is fairly easy to obtain and by internally setting very conservative defaults for input that you do not directly provide—cyclic material properties, for example. If you are an advanced fatigue user, you may want to alter these defaults to examine less conservative scenarios. In its default state, Fatigue Advisor is an excellent tool for quickly identifying whether fatigue is an issue for your model, comparing design iterations, and identifying potential failure locations. Because the results that Fatigue Advisor provides are conservative, you can be confident that the tool will find any areas of concern in your model. For example, Fatigue Advisor uses a default value of 90% for material confidence level, meaning that 90% of the test results under the modeling conditions you set would have longer lives than the software predicts. If you are a fatigue expert, you may not want to use Fatigue Advisor's internal defaults for some applications, specifically because these defaults are highly conservative. For instance, if you are primarily interested in comparing Fatigue Advisor's life predictions to specific test results or results provided by alternative fatigue simulation software, the conservative defaults may not provide good results correlation. In this case, you should consider adjusting the internal parameter defaults to ensure that you are comparing similar paradigms and to improve results correlation. You change Fatigue Advisor parameter default settings through a variety of config.pro options. Be aware that improper default settings can result in questionable analysis results. Thus, you should consider a thorough knowledge of fatigue theory to be a prerequisite for changing the defaults. 695 Structural and Thermal Simulation - Help Topic Collection Here is a list of parameters whose defaults you can alter: • • • • cyclic material properties material confidence level mean stress parameter biaxiality parameter Another parameter that you may want to adjust is variable amplitude load history. Fatigue Advisor enables you to specify either a constant or variable amplitude load history when you define your fatigue analysis. If you decide to use a variable amplitude load history, you can either enter the data or import an ASCII file defining the load history. Importing a variable load history file can allow you to better correlate test results. Note that you do not need to change any config.pro default settings to utilize an ASCII file as the variable amplitude load history. Adjusting the Biaxiality Parameter for Fatigue Fatigue Advisor allows you to indicate whether you want to apply biaxiality correction during analysis through the use of configuration options. By default, Fatigue Advisor calculates biaxiality correction on a node-by-node basis using three correction methods—Klann-Tipton-Cordes, Hoffman-Seeger, or no biaxiality correction. The software determines which of these methods generates the worst case and reports those results. You can change these defaults using two configuration options: • • SIM_FATIGUE_BIAXIALITY_CORRECTION config.pro option — Use this option to indicate whether you want Fatigue Advisor to apply biaxiality correction. The default state for this option is YES. SIM_FATIGUE_BIAXIALITY_METHOD config.pro option — Use this option to indicate the method Fatigue Advisor should apply—Klann-TiptonCordes, Hoffman-Seeger, or WORST. As mentioned, the default state for this option is Worst. Note that the software only checks the setting for this option if SIM_FATIGUE_BIAXIALITY_CORRECTION is set to YES. If you decide to set either of these options to a state other than the default, you should do so based on correlation with test data. Guidelines for Entering Polynomial Order When entering values for the polynomial order, consider the following points: • • • • The calculation time at each polynomial order increases significantly over the previous order. A low convergence percentage may require a high polynomial order. If an element did not converge during a run until a polynomial order of 7 or higher, you may want to divide that element. You may save time by using a maximum polynomial order of 5 for a preliminary run and then checking the results to see how close the results are to the convergence you want. 696 Structural and Thermal Simulation Strategy: Specifying Polynomial Order for a Multi-Pass Adaptive Analysis When you define a multi-pass adaptive analysis, you can specify the minimum and maximum polynomial order that the Mechanica engine uses for each edge. The default is a minimum of 1 and a maximum of 6. In general, use the default values. If the analysis does not converge on the first run, review the results to understand why it did not converge. See Reviewing the Results for information on reviewing convergence graphs, stress and flux fringe plots, and p-level results. A run usually fails to converge for one of two reasons: • • A singularity is present and the engine is trying to capture a high stress or flux gradient. A highly distorted element is trying to capture a smooth stress or flux field. In either case, the best solution is to refine the mesh through the AutoGEM Settings dialog box, recreate the mesh, and rerun the analysis. You can use items on the AutoGEM Settings dialog box to divide the elements near the local effects, such as concentrated loads, cracks, reentrant corners, and thickness discontinuities between shells. If this proves difficult, increasing the maximum polynomial order is an alternative. (But if you require high polynomial levels in areas of interest, you should consider refining your mesh). With smaller elements, convergence is more likely to occur and thus will ensure better results in the areas of interest. For transient thermal analyses, if you suddenly switch on heat loads and convection conditions, your changes will adversely affect analysis convergence. If all heat loads and convection conditions are smooth functions that are zero at the start of the analysis, the engine will generally select smaller values for the p-orders. For more information on how to smooth these functions, see Ramping of Heat Loads and Convection Conditions. Temperature Load Information for Static Analyses If your static analysis has a temperature load, the dialog box shows the following information, which determines temperature distribution for the analysis: Temperature Load Type global temperature load Dialog Box Displays the distribution method and temperature for the temperature load 697 Structural and Thermal Simulation - Help Topic Collection Temperature Load Type Mec/T temperature load Dialog Box Displays the source design study, analysis, and load set for the temperature load external temperature field file name Ext/T temperature load Single-Pass Adaptive Convergence Method Single-pass adaptive convergence applies to static, modal, buckling, and contact analyses of all element types. Models may consist of isotropic and/or orthotropic materials. While the single-pass adaptive option is available for contact analysis, we do not normally recommend its use because it can increase run time. Mechanica runs a first pass at p=3 and determines a local estimate of stress error. Using this error estimate, Mechanica determines a new p-order distribution and performs a final pass. If you use the iterative solver, Mechanica runs a first pass using the block solver at p=2, followed by a second pass (p=3) using the iterative solver. Using the stress error estimate from pass 2, Mechanica performs a third and final pass. Mechanica displays an RMS error estimate for stress in the summary file, so you can check the solution quality. In general, use single-pass adaptive convergence when it is available. Larger models run with single-pass adaptive convergence typically require less disk space. Also, single-pass adaptive convergence yields comparable results to multi-pass adaptive convergence of 10% with generally shorter run times. With single-pass adaptive analysis, you do not control the convergence tolerance, but you do need to examine the stress error estimates reported in the run summary. If these error estimates are acceptable, then continue to use single-pass adaptive convergence for efficiency. If the error estimates from the single-pass adaptive convergence tolerance are not acceptable—for example, the stress error estimates are too large—then switch to the multi-pass adaptive convergence strategy for subsequent design studies. For information about using the quick-check convergence method, see Strategy: Identifying and Resolving Potential Trouble Spots in a Model. 698 Structural and Thermal Simulation Multi-Pass Adaptive Convergence Method When you run a design study, the Structure engine performs calculations and increases the polynomial order for each element edge until the convergence criteria are satisfied. (The polynomial level for edges on which beams and 2D shells lie begins with either the third order or the order you enter on the analysis definition dialog box, whichever is higher). An analysis converges when the difference in the results of the current pass and the previous pass is within the percentage you specify under Convergence. Convergence Quantity for Static, Prestress Static, Large Deformation, and Contact Analyses If you select Multi-Pass Adaptive under Convergence Method, you select the quantities Mechanica uses to calculate convergence. See Percent Convergence for information on how Mechanica measures convergence for the multi-pass adaptive method. For static, prestress static, large deformation, and contact analyses, you can select one of these options: • • Local Displacement and Local Strain Energy — Mechanica calculates convergence of the displacements along each element edge and of the total strain energy of each element. Local Displacement, Local Strain Energy and Global RMS Stress — Mechanica uses RMS (Root Mean Square) stress in addition to displacement and strain energy to calculate convergence. Mechanica checks convergence for RMS stress by extrapolating the total strain energy of three successive calculations. As a result, RMS stress is sensitive to the rate of convergence. This option provides high accuracy, but can also mean greater computation time. • Measures — Mechanica uses one or more measures to determine convergence. When you select this option, the Measures button becomes available. Click the Measures button to select measures from the Measures dialog box. Use Measures for convergence if you are interested either in results for one or more specific quantities, such as maximum principal stress or displacement magnitude, or in results at a particular location, such as a boundary condition or local stress concentration. Using Measures can help improve accuracy for the quantities or locations of interest, and may also lower the computation time for your design study. 699 Structural and Thermal Simulation - Help Topic Collection When you select Measures, the Structure engine samples over the plotting grid to get a measure's maximum value during a run and uses that value to determine convergence. Your plotting grid setting may have a slight effect on convergence values. Percent Convergence If you selected Multi-Pass Adaptive for the convergence method, you enter a percentage to determine the accuracy level. The percentage applies to the convergence quantities you select. • During the analysis, Mechanica performs calculations at increasingly higher polynomial orders for each element edge. An analysis converges when the difference in the results of the last two calculations is within the percentage you specify here. You should enter a value between 1% and 25%. Lower convergence percentages yield more accurate results, but Mechanica may take longer to reach convergence. You should balance the level of accuracy you need with the amount of time the analysis will take to run. If an analysis does not reach convergence during a design study, the results may not have the desired accuracy. In this case, you need to change something in your model to get better results. • • • Convergence Method Convergence gives you an idea of how accurate your results are. If your analysis does not reach convergence during a design study, the results may not have the desired accuracy. In this case, you need to modify your model. Select one of these convergence methods for Mechanica to use when it runs your analysis: • • • Multi-Pass Adaptive — Mechanica calculates results at increasing polynomial orders until convergence criteria are satisfied. Single-Pass Adaptive — Mechanica runs a first pass at a polynomial order of 3 and determines a local estimate of stress error. Using this error estimate, Mechanica determines a new p-order distribution and performs a final pass. Quick Check (No Convergence) — Mechanica performs a single pass at a uniform polynomial order of 3. You can use this method to verify that you have defined your analysis correctly. 700 Structural and Thermal Simulation This table summarizes which methods are available for different analysis and model types: Analysis Types Multi-Pass Adaptive available Single-Pass Adaptive available only for 3D models or models with 2D solids available only for 3D models not available available Quick Check static, modal, contact available prestress modal, buckling prestress static large deformation static available available available not available available available Polynomial Order The values you specify for minimum and maximum polynomial orders determine the polynomial order Mechanica uses when analyzing your model. For each value, you can enter a number from 1 to 9. The default minimum is 1. The default maximum is 6. The engine begins with all element edges at the minimum polynomial order and repeats its calculations at increasingly higher polynomial orders for each edge until it reaches one of the following values: • • the maximum polynomial order that you specify here the convergence percentage. This happens when the results of the last two calculations are within the value you specified for Percent Convergence. For more information on polynomial order, see: • • Guidelines for Entering Polynomial Order Strategy: Specifying Polynomial Order for a Multi-Pass Adaptive Analysis Convergence Quantity for Modal and Prestress Modal Analyses If you select Multi-Pass Adaptive for the convergence method, you can select the quantities Mechanica uses to calculate convergence. See Percent Convergence for information on how Mechanica measures convergence for the multi-pass adaptive method. 701 Structural and Thermal Simulation - Help Topic Collection For modal and prestress modal analyses, you can select one of these options: • • Frequency — Mechanica calculates the convergence for the frequency of each mode. Frequency, Local Displacement, and Local Strain Energy — Mechanica calculates convergence of the frequency of each mode, of the displacements along each element edge, and of the total strain energy of each element. Use this option if you are interested in details of mode shapes. However, Mechanica is likely to have to go to a higher polynomial order to reach convergence for this option, and takes longer to compute results. • Frequency, Local Displacement, Local Strain Energy, and RMS Stress — Mechanica uses RMS (Root Mean Square) stress in addition to frequency, displacement, and strain energy to calculate convergence. The RMS stress error measure is a single scalar value that is proportional to the square root of the estimated error in total strain energy. Mechanica checks convergence for RMS stress by extrapolating the total strain energy for three successive calculations. As a result, RMS stress is sensitive to the rate of convergence. Use this option if you are interested in details of mode shapes and modal stresses. This option provides high accuracy, but can also mean greater computation time. Localized Mesh Refinement For a contact analysis, if you select Single-Pass Adaptive for the convergence method, you can use this option to improve the accuracy of contact pressure results. You should select this item only if accurate contact pressures are an important objective for the analysis. Mechanica automatically refines the element mesh to improve contact pressure results during the analysis if: • • The contact area covers only a small portion of one or more element faces involved in the contact, a situation that can cause inaccurate contact pressure results. You select Localized Mesh Refinement. If the mesh refinement fails during the first pass, Mechanica continues with a second pass using the original mesh. During the second pass, you can view the results of the first pass. If you decide not to continue with the second pass, you can stop the analysis. 702 Structural and Thermal Simulation Convergence Quantity for Buckling Analyses If you select Multi-Pass Adaptive under Convergence Method, you select the quantities Mechanica uses to calculate convergence. See Percent Convergence for information on how Mechanica measures convergence for the multi-pass adaptive method. For buckling analyses, you can select one of these options: • • Buckling Load Factor (BLF) — Mechanica calculates convergence of the buckling load factor for each buckling mode requested. BLF, Local Displacement and Local Strain Energy — For each buckling mode, Mechanica calculates convergence of the BLF of each mode, of the displacements along each element edge, and of the total strain energy of each element. Use this option if you are interested in details of mode shapes. However, Mechanica is likely to have to go to a higher polynomial order to reach convergence for this option, and takes longer to compute results. • BLF, Local Displacement, Local Strain Energy, and RMS Stress — Mechanica uses RMS (Root Mean Square) stress for each buckling mode in addition to BLF, displacement, and strain energy to calculate convergence. The RMS stress error measure is a single scalar value which is proportional to the square root of the estimated error in total strain energy. Mechanica checks convergence for RMS stress by extrapolating the total strain energy for three successive calculations. As a result, RMS stress is sensitive to the rate of convergence. Use this option if you are interested in details of mode shapes and modal stresses. This option provides high accuracy, but can also mean greater computation time. Unconstrained If you select this item, Mechanica automatically selects With Rigid Mode Search and looks for and reports rigid body modes for an unconstrained analysis. You might select this option if you want to examine rigid body vibrations. If your model contains point-to-ground springs, you can select Unconstrained separately from With Rigid Mode Search. Point-to-ground springs are the equivalent of constraints. You still have the option of selecting With Rigid Mode Search, but you do not have to select it as long as the springs sufficiently constrain your model. 703 Structural and Thermal Simulation - Help Topic Collection Constrained, With Rigid Mode Search Use these items if you want to include a constraint in the analysis: • Constrained — Select this item to include a constraint in the analysis. Then select one constraint set from the list. With Rigid Mode Search — Use this item if you want Mechanica to look for and report rigid body modes when it runs a design study containing this analysis. You should select this item if your model is not fully constrained or if you are not sure. Otherwise, you will get a fatal error when you try to run a design study containing this analysis. If your model is fully constrained, selecting With Rigid Mode Search does not cause any problems, but does add to the run time. Note: If you select Unconstrained, Mechanica automatically selects With Rigid Mode Search for most models. For details, see Unconstrained. • Thermal Analysis About Thermal Analysis Use the Analysis>Mechanica Analyses/Studies command to define a thermal analysis. A thermal analysis measures the effect of thermal loading on your model. In Thermal, you can define two types of analyses: • • Steady Thermal — Calculates steady-state thermal response to a constraint set and one or more optional heat loads. The constraint set is comprised of one or more prescribed temperatures and/or convection conditions. Transient Thermal — Calculates temperatures and heat fluxes in your model at different times in response to one or more optional heat loads and subject to one or more optional prescribed temperatures and/or convection conditions. You must specify at least one load set or one constraint set. For guidelines on thermal analysis, see Boundary Condition and Load Sets in Thermal Analyses. 704 Structural and Thermal Simulation Boundary Condition and Load Sets in Thermal Analyses When you are defining thermal analyses, keep in mind the following: • • • • • For both steady and transient thermal analyses, you do not have to select a load set. For a transient thermal analysis, you do not have to select a boundary condition set. If you do not select a boundary condition set, however, you must select one or more load sets for the analysis to be valid. For steady thermal analyses, you must select one boundary condition set. If you delete a boundary condition set or load set after you include it in an analysis, you are also deleting that set from the analysis. Even if you create a new set with the same name as the set you deleted, you must edit the analysis and reselect the set name. Otherwise, you can invalidate the analysis and any design studies in which you included the analysis. Steady Thermal Analysis You can use steady thermal analyses to calculate thermal response to heat loads subject to prescribed temperatures and/or convection conditions. Steady thermal analyses assume a steady state for all thermal loads and boundary conditions. This form of analysis does not evaluate changes over time. For a description of and requirements for steady thermal analysis, see Steady Thermal Analysis Overview. These items appear on the Steady Thermal Analysis Definition dialog box: • • Constraints — Select a constraint set. Loads — Select one or more load sets. This is optional. Mechanica calculates results separately for each load set you include in the analysis. The following tabs appear on the Steady Thermal Analysis Definition dialog box: • • Convergence Output Steady Thermal Analysis Overview Description A steady thermal analysis calculates a thermal response to specified heat loads subject to specified prescribed temperatures and/or convection conditions. For example, you could define a steady thermal analysis for a model with a cooling fin, as on a lawn mower engine. In defining the analysis, you would subject the 705 Structural and Thermal Simulation - Help Topic Collection cooling fin to a constant heat load (piston heat output) and a forced convection (moving air). Mechanica automatically calculates all generic, mass property, and thermal measures. Requirements • 1 constraint set To Create a Steady Thermal Analysis 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Steady Thermal from the File menu. The Steady Thermal Analysis Definition dialog box appears. 3. Enter a name for the analysis. A description is optional. 4. Select a boundary condition set. 5. If you defined heat loads for your model, you have the option to select one or more heat load sets you want to include in the analysis. 6. Click the following tabs on the dialog box to select additional options for the steady thermal analysis: o Convergence o Output 7. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. . Transient Thermal Analysis You can use transient thermal analyses to calculate thermal responses in your model over a period of time. For a description of, and requirements for, transient thermal analysis, see Transient Thermal Analysis Overview. These items appear on the Transient Thermal Analysis Definition dialog box: • • Constraint — Select a constraint set (optional). You are not required to select a constraint set to run a transient thermal analysis. However, if you do not select a constraint set, you must select at least one heat load set. Loads (Summed) — Select one or more load sets (optional). This is optional if you select a constraint set. Mechanica applies all the load sets that are 706 Structural and Thermal Simulation selected and computes just one time-dependent solution, the same as if all the heat loads were in one load set. The following tabs appear on the Transient Thermal Analysis Definition dialog box: • • • Temperatures Convergence Output Transient Thermal Analysis Overview Description A transient thermal analysis calculates temperatures and fluxes in your model over a particular time range. If you are not interested in the variation of temperature over time, you should use steady thermal analysis instead. Mechanica also calculates measures that you defined for your model. Use custom measures to determine: • • • the time at which a given condition is true the value of a measure at a point in time the max, min, or max abs for a measure over the entire analysis or over a specified time range You can direct Mechanica to report full results or temperature loads at specified time intervals. After you run a transient thermal analysis, with full results selected for multiple intervals, you can view the results at the various intervals by animating the fringe plot. Use transient thermal analysis to find out the following types of information: • • • the time your model takes to heat up or cool down the way your model might respond to a time-dependent heat load or bulk temperature the thermal stresses that develop as a result of temperature changes in your model Requirements • • • • • a 3D solid model isotropic material properties only no shell or beam elements no links 1 constraint set or 1 load set 707 Structural and Thermal Simulation - Help Topic Collection To Create a Transient Thermal Analysis 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Transient Thermal from the File menu. The Transient Thermal Analysis Definition dialog box appears. 3. Enter a name for the analysis. A description is optional. 4. If you want to include boundary conditions in your thermal analysis, you have the option to select a boundary condition set. If you do not select a boundary condition set, you must select at least one heat load set. 5. If you want to include heat loads in your analysis, you have the option to select one or more heat load sets. At least one heat load set is required if you did not select a boundary condition set. Mechanica sums the load sets and computes one time-dependent solution. 6. Click the following tabs on the dialog box to select additional options for a transient thermal analysis. o Temperatures o Convergence o Output 7. Click OK when you complete the dialog box. The dialog box reappears with the name, type, and description of the new analysis displayed. . To Select Output Options for a Thermal Analysis This procedure assumes you are in the dialog box for creating a steady thermal analysis or a transient thermal analysis. 1. Click the Output tab on the analysis dialog box. 2. If you do not want Heat Flux calculated, clear the check box. Heat Flux is selected by default. 3. Select the density of the plotting grid. Note: If you are creating a steady thermal analysis, skip the following steps. 4. Select an option for specifying the Output Intervals for which you want results—Automatic Intervals Within Range or User-defined Output Intervals. 708 Structural and Thermal Simulation If you select User-defined Output Intervals, different items appear on the tab. Continue with steps 7 through 10. 5. If you selected Automatic Intervals Within Range, enter a minimum time for the lower end of the time range for which you want Mechanica to report results for your analysis. 6. Enter a maximum time for the upper end of the time range or select the Auto check box. Note: If you selected Automatic Intervals Within Range, skip the remaining steps. 7. Enter the Number Of Master Intervals for your analysis. The table displays numbered rows representing the number of intervals you selected. 8. Use the default values for each interval to specify the spacing between intervals or click the User-defined Steps button to enter values. If you click User-defined Steps, you can use the Space Equally button to evenly space the steps. 9. Select the Full Results check boxes next to the intervals for which you want to save full temperature and flux results. 10. Select the Temp Load check boxes next to the intervals for which you want to save temperature load data for importing a thermal load or a temperature field into Structure. You can also click intervals or click to save full results and temperature load data at all to deselect the check boxes for all intervals. To Select Temperature Options for a Transient Thermal Analysis This procedure assumes you are in the Transient Thermal Analysis Definition dialog box. 1. Click the Temperatures tab on the analysis dialog box. 2. Select an option for Initial Temperature Distribution—Uniform or MecT. 3. If you selected Uniform, enter the temperature in the Temperature field. If there are any prescribed temperatures in the constraint set, you must enter the same value as the prescribed temperature. 4. If you selected MecT and want to use temperature results from a previously run steady thermal analysis, you can select the check box Use Temperatures From Previous Design Study. 709 Structural and Thermal Simulation - Help Topic Collection If you do not select this check box, Mechanica will run a steady thermal analysis as part of running the transient thermal analysis. 5. If you selected Use Temperatures From Previous Design Study, select the following items to include in your transient thermal analysis: o o o Design Study (if applicable) Thermal Analysis Load Set 6. Enter a value for Accuracy. 7. Enter a value for Estimated Variation of the temperature or select the Auto check box. 8. Use the default selection Automatically Smooth Convections so that convection conditions will be turned on gradually, or you can deselect this item. To Set Convergence for a Thermal Analysis This procedure assumes you are in the dialog box for creating a steady thermal analysis or a transient thermal analysis. 1. Click the Convergence tab on the analysis dialog box. 2. Select a convergence method for your steady thermal analysis or transient thermal analysis: o Multi-Pass Adaptive (available only for steady thermal analysis) o Single-Pass Adaptive o Quick Check Note: If you are creating a steady thermal analysis and selected Multi-Pass Adaptive, continue with the following steps. 3. Enter a minimum and maximum polynomial order. 4. Enter a convergence percentage. 5. Select the quantities you want Mechanica to use to calculate convergence. Estimated Variation You use Estimated Variation to indicate the expected difference between the maximum and minimum temperature in the model during the analysis. You can enter a value or select Auto. If you select Auto, the engine estimates a value from the applied heat loads and convection conditions. If you enter a value, it must correspond to the temperature variation that you expect your model to experience during the analysis. This value, which must be a positive number, works with the value you set in the Accuracy field to control the accuracy of the time integration. The estimated temperature variation you enter need only be the correct order of magnitude to ensure that Mechanica controls time integration errors properly and 710 Structural and Thermal Simulation efficiently. If you enter a value for estimated temperature variation that is too small, the engine may warn that it took too many time steps. However, if at any point in the analysis the actual temperature variation exceeds your specified value, or the value estimated by the engine from the applied heat loads, the engine proceeds with the larger value, computed as a result of the time integration. If the engine warns that the estimated temperature variation was too large, the solution may still be sufficiently accurate because of the control of errors in energy norm. You can verify this by re-running the analysis a second time with the Estimated Variation equal to the value of temperature variation reported by the engine in the original analysis. Alternatively, you can use the quick check analysis to compute the temperature variation in the model and enter that value for Estimated Variation before running a transient thermal analysis with single-pass adaptive convergence. Initial Temperature Distribution Select the initial temperature for your model at the start of the transient thermal analysis. You can select one of two options: • Uniform — Apply a uniform temperature distribution over the model. Enter the initial temperature in the Temperature field below this item. The temperature value must be the same as any prescribed temperatures in the constraint set. If there are no prescribed temperatures, you can specify any value for uniform initial temperature. MecT — Use the temperature results from a steady thermal analysis to specify the initial temperature for your transient thermal analysis. Before you select this option, you must first define a steady thermal analysis. When you select MecT, the dialog box displays the name of a steady thermal analysis and a load set from that analysis. If you have multiple analyses or load sets, you can select the ones you want to use. Mechanica runs the steady thermal analysis you select before running the transient thermal analysis. You can also select Use Temperatures From Previous Design Study if you want to use the results of a previously run analysis. • Transient Thermal Convergence Method You can select one of the following convergence methods for Mechanica to use when it runs your transient thermal analysis: • Single-Pass Adaptive — This method is the default. Mechanica runs a first pass at p=3 and determines a time-step reading of the model temperature. Each subsequent time-step uses information from the previous time-step to determine a new p-level. 711 Structural and Thermal Simulation - Help Topic Collection • Quick Check (No Convergence) — Mechanica performs a single-pass analysis with uniform p=3. You can use this method to verify that you have defined your analysis correctly. Neither of the preceding convergence methods is supported for the following: • • • • 2D models models with shell or beam elements models with transversely isotropic or orthotropic materials models with links Transient thermal analyses take longer to run than steady-state thermal analyses. For some runs, you may want to use the Quick Check convergence method to get a quick reading of your model. When you do use the single-pass adaptive convergence method, allow more time for your run. Note: For transient thermal analyses, if you suddenly switch on heat loads and convection conditions, these changes can adversely affect analysis convergence. If all heat loads and convection conditions are smooth functions that are zero at the start of the analysis, the engine will generally select smaller values for the p-orders. For more information on how to smooth these functions, see Ramping of Heat Loads and Convection Conditions. Automatically Smooth Convections If the convective heat exchange rate for a model entity is rapid, increased numerical errors can occur. Select the Automatically smooth convections option to turn on the convection conditions gradually, reducing these numerical errors. This feature is selected by default. Accuracy This value represents the acceptable fractional temperature error used to determine the time step. The time step may vary by many orders of magnitude during the course of an analysis, depending on the loads and constraints. At the beginning of an analysis, the time step can be especially small. Since the energy norm in the model is zero at the start of an analysis, the errors in energy norm are normalized by a small value. This value works with the temperature variation value to control the accuracy of the time integration. For example, if you set Accuracy to a value of 0.001 and set Estimated Variation to a value of 200, the Thermal engine attempts to keep timestep errors in temperature to a value of 0.2 degrees or less. Mechanica controls the accuracy of transient thermal analyses by varying the p-order of element edges and the time step used for numerical integration. These values change as an analysis progresses. Two parameters affect the time step size on the Analysis Definition dialog box for transient thermal analysis—Accuracy and Estimated Variation. 712 Structural and Thermal Simulation Errors in temperature must be less than the product of the estimated temperature variation and the accuracy. Percent Convergence Convergence gives you an idea of how accurate the results are. If an analysis does not reach convergence during a design study, the results may not have the desired accuracy. In this case, you need to make modifications to your model to get better results. Enter the percentage you want Mechanica to use to determine convergence for this analysis. This option is available only with the multi-pass adaptive convergence method. The default convergence value is 10%. For most analyses, you should enter a value from 1% to 25%. If you enter a convergence value outside this range, Mechanica asks you to confirm the value you entered. Convergence Quantities for Steady Thermal Analysis If you select the multi-pass adaptive convergence method for a steady thermal analysis, you can select one of three options for the quantities Mechanica uses to calculate convergence: • • • Local Temperatures and Local Energy Norms — Mechanica calculates convergence of the temperatures along each element edge and of the energy norms in each element. This option is the default convergence option. Local Temperatures and Local and Global Energy Norms — Mechanica uses global norms in addition to temperatures and local energy norms to calculate convergence. Measures — Mechanica uses one or more thermal measures to determine convergence. Steady Thermal Convergence Method You can select one of the following convergence methods for Mechanica to use when it runs your steady thermal analysis: • Multi-Pass Adaptive — This method is available for all model types. When you run a design study, the Mechanica Thermal engine performs calculations and increases the polynomial order for each element edge until the convergence criteria is satisfied. An analysis converges when the difference in the results of the current pass and the previous pass is within the percentage you specify for Percent Convergence. • Single-Pass Adaptive — This method is available for all 3D models. 713 Structural and Thermal Simulation - Help Topic Collection Mechanica runs a first pass at p=3 and determines a local estimate of heat flux error. Using this error estimate, Mechanica determines a new p-order distribution and performs a final pass. If you use the iterative solver, Mechanica runs a first pass using the block solver at p=2, followed by a second pass using the iterative solver at p=3. Using the heat flux error estimate from the second pass, Mechanica performs a third and final pass. The polynomial order for beams is 9 for the final pass. • Quick Check (No Convergence) — This method is available for all models. It does not check convergence. Mechanica performs a single pass analysis with uniform p=3. You can use this method to verify that you have defined your analysis correctly. Understanding Accuracy Accuracy is a dimensionless number that is used to control local time integration errors. A local time integration error indicates that the error is estimated for each time step in the analysis, independent from the results of previous time steps, whereas a global time integration error depends on the entire time integration. The engine selects the size of the time step to keep local time integration errors in temperature smaller than the product of accuracy and estimated temperature variation, and errors in energy norm smaller than the product of accuracy and energy norm. Specifying an accuracy value of 0.001 does not guarantee that all results are within one-tenth of one percent of the exact solution. This is mostly because the accuracy of the solution is affected strongly by the spatial discretization, but also because the global time error is not controlled. To improve the spatial discretization, the engine increases or decreases the p-orders as needed to keep the flux jumps at element boundaries below a target value. Some models require more elements to capture thin layers with sharp temperature gradients that result from fast convection conditions or rapidly-varying heat loads. Time Range Specification To specify the time range, enter: • • Minimum — Enter a number greater than or equal to zero. Maximum — Enter a number greater than zero or select Auto. If you select Auto, the engine determines the total time for the duration of the analysis. Note: Selecting Auto for the maximum time can cause your analysis to run longer than necessary to produce the results you need. If you use the Auto selection, therefore, be sure to allow for the extra time required. 714 Structural and Thermal Simulation Time Range Specify a minimum and a maximum time for the time range that defines the start and finish time for the analysis. In Mechanica, all of the predefined systems of units measure conductivity in seconds. The units you use to measure time must be consistent with your system of units and the units for measuring conductivity. For example, if you want to measure conductivity in BTUs per hour, you may need to change your system of units. User-defined Steps for Transient Thermal Analysis Use this button to specify the spacing between steps in the time range. You can enter different values for each step. The values you enter must be in increasing order from step to step. When you click the User-defined Steps button, you can also use the Space Equally button to evenly space the steps. You cannot enter any values for the steps if you selected Auto for the maximum of the time range. The dialog box shows Auto for each step in the table. Output Intervals for Transient Thermal Analysis Use this item to specify a time range, master intervals, and the results you want Mechanica to report at selected intervals. Master intervals serve two purposes: • • to save output data to force the time integrator to notice important events, such as times when a heat load jumps suddenly If you use the default option, Automatic Intervals Within Range, Mechanica selects appropriate intervals at which to report results. You specify a time range by entering a minimum time and a maximum time. You have the option to select Auto to automatically enter the maximum time. If you select User-defined Output Intervals, the following items become available: • Number of Master Intervals — Enter the number of master intervals at which you want Mechanica to report results. Mechanica displays the intervals in a table with numbered rows. You can specify up to 999 master intervals. In general, computation time increases with the number of intervals. Full Results — Select the check boxes next to the intervals for which you want to save full temperature and flux results. 715 • Structural and Thermal Simulation - Help Topic Collection • • • • • Temp Load — Select the check boxes next to the intervals for which you want to save data for importing a thermal load or temperature field into Structure. User-defined Steps — Click this button to enter values for spacing the time steps. Space Equally — Enters evenly spaced values for the steps. This button is only available when you click User-defined Steps. (Select All) — Click this button if you want to save full results and temperature load data for all intervals. (Deselect All) — Click this button if you do not want to save full results and temperature load data for any intervals. Temperature Options for Transient Thermal Analysis These items appear on the Temperatures tab on the Transient Thermal Analysis Definition dialog box: • • Distribution — Specify initial temperature distribution—Uniform or MecT. Temperature — Enter an initial temperature if you selected Uniform for Distribution. This temperature value must be the same as any prescribed temperatures in the constraint set. These additional items appear on the tab only if you select MecT for Distribution: • Use Temperatures From Previous Design Study — You can select this check box option if you want to use temperature results from a previously run steady thermal analysis for the initial temperature in your transient thermal analysis. If this option is not selected, Mechanica runs the steady thermal analysis as part of running the transient thermal analysis. Design Study —If you selected the option Use Temperatures From Previous Design Study, select a design study to include in the transient thermal analysis. Thermal Analysis — Select a steady thermal analysis. Load Set — Select a load set. • • • These options are available for all transient thermal analyses: • • • Accuracy — Enter a value for the acceptable fractional temperature error. Estimated Variation — Enter a value for temperature variation or select Auto. Automatically Smooth Convections — Select this option to turn on convection conditions gradually. Thermal Measures Mechanica uses one or more measures to determine convergence. Select Measures for convergence if you are interested either in results for one or more specific 716 Structural and Thermal Simulation quantities, such as maximum flux magnitude, or in results at a particular location, such as a boundary condition or local flux concentration. Using Measures can help improve accuracy for the quantities in which you are interested, and may also lower the computation time for your design study. When you select Measures as the convergence option, the Measures button becomes available. Click this button to select thermal measures from the Measures dialog box. You can select any global or local thermal measures. Plotting Grid The value you specify determines the number of intervals along each edge or across each face that Mechanica uses to create plotting grids. Mechanica calculates quantity values at the intersections of grid lines. Enter a number from 2 to 10 to determine the level of detail Mechanica uses to report results of the analysis. If you enter a higher number, the grid will be finer, and Mechanica reports values from more locations on each element. At lower numbers, Mechanica takes less time to calculate results, and the data takes up significantly less space. The default is 4. Mechanica reports precise results for each grid intersection point and interpolates these values to show results elsewhere. Local Temperatures and Local Energy Norms Mechanica calculates convergence of the temperatures along each element edge and of the energy norms in each element. The energy norm of an element is a scalar quantity that is proportional to the integral over the element of the flux squared. It is analogous to element strain energy in a static structural analysis. Local Temperatures And Local Energy Norms is the default convergence option. Local Temperatures and Local and Global Energy Norms Mechanica uses global norms in addition to temperatures and local energy norms to calculate convergence. The global energy norm is the sum of the energy norms of all elements in the model. The global energy norm error measure is a single scalar value that is proportional to the square root of the estimated error in the global energy norm. 717 Structural and Thermal Simulation - Help Topic Collection Mechanica checks convergence for the global energy norm by extrapolating the global norm of three successive calculations. As a result, global norm convergence considers the rate of convergence. This option provides high accuracy, but can also mean greater computation time. Heat Flux This check box enables you to have heat flux calculated as part of your analysis. This option is selected by default and works as a toggle. If you do not want heat flux calculated, deselect this option. Be aware that if you do not select Heat Flux, you cannot access results for heat flux when you look at results for your analysis. Convergence Percentage Calculation Mechanica calculates the convergence percentage in the following ways: • When you run a design study, the engine performs calculations at increasingly higher polynomial orders for each element edge. An analysis converges when the difference in the results of the last two calculations is within the percentage you specify here. The engine finishes calculating results when the analysis converges, or when it has reached the maximum polynomial order that you specified. Lower convergence percentages yield more accurate results, but Mechanica may take longer to reach convergence. You should balance the level of accuracy you need with the amount of time it will take to run a design study containing this analysis. • • Output Options for Thermal Analyses These items appear on the Output tab on the dialog boxes for steady thermal and transient thermal analyses: • • • Heat Flux — This option is selected by default. You must deselect this option if you do not want to calculate heat flux. Plotting Grid — Specify the density of the plotting grid that determines where Mechanica calculates results. Output Intervals — Appears only for transient thermal analysis. Select this option to specify the number of intervals in the time range at which you want Mechanica to report results. 718 Structural and Thermal Simulation Convergence Options for Thermal Analyses These items appear on the Convergence tab on the dialog boxes for steady thermal and transient thermal analyses: • Method — Select a convergence method for calculating results and determining the accuracy of steady thermal analysis results or transient thermal analysis. The following items appear on the tab only for steady thermal analysis with the Multi-Pass Adaptive convergence method selected: • • • Polynomial Order — Enter a minimum and maximum polynomial order. Limits — Enter the Percent Convergence. Converge on — Select the convergence quantities you want to use. Vibration Analysis About Vibration Analysis Use the Analysis>Mechanica Analyses/Studies command in Structure to define a vibration analysis. The following four types of vibration analysis are available to Structure users: • • • • Dynamic Time — Calculates displacements, velocities, accelerations, and stresses in your model at different times in response to a time-varying load. Dynamic Frequency — Calculates the amplitude and phase of displacements, velocities, accelerations, and stresses in your model in response to a load oscillating at different frequencies. Dynamic Random — Calculates the power spectral densities and RMS values of displacements, velocities, accelerations, and stresses in your model in response to a load of specified power spectral density. Dynamic Shock — Calculates maximum values of displacements and stresses in your model in response to a base excitation with specified response spectrum. Dynamic Time, Dynamic Frequency, and Dynamic Random Analyses Mechanica dynamic analyses measure a system response to a number of time-driven loads. You can use dynamic time analysis to examine system response to a nonperiodic, or impulsive, time-dependent load. You can use dynamic frequency analyses to evaluate system response to a periodic, or cyclical, frequency-dependent load. You can use dynamic random analysis to measure the system response to a power spectral density function. 719 Structural and Thermal Simulation - Help Topic Collection For a description of, and requirements for, each analysis type, see Dynamic Time Analysis Overview, Dynamic Frequency Analysis Overview, and Dynamic Random Analysis Overview. The dialog boxes for dynamic time, dynamic frequency, and dynamic random analyses include the following: • Loading — Select Load Functions or Base Excitation. To use Load Functions, you must have loads defined on your model. You can use Base Excitation only if you select a constrained modal analysis to include in your dynamic analysis. If you select Load Functions, these items appear under Loading: o o Sum Load Sets — Select this check box if you want to combine the results from all selected load sets. Load Sets list — Select the check boxes next to the load sets you want to use. Click ƒ(x) to select load set functions for each one or use the default functions. If you select Base Excitation, these items appear under Loading: o o o Time (or Frequency) Dependence — Select a function for time or frequency dependence. Direction — Select WCS coordinates for the direction of base excitation. Relative to — Select whether you want results calculated relative to Ground or to Supports. For both Load Functions or Base Excitation, you can use the Include Frequency Steps From Table check box to ensure that the solution includes all steps in a table input function, not just those that Mechanica selects automatically. The following tabs appear on the dialog boxes for dynamic time, dynamic frequency, and dynamic random analyses: • • • Modes Previous Analysis Output Dynamic Time Analysis Overview Description Dynamic time analysis measures the response of a system to a non-periodic or impulsive, time-dependent load. The load input takes the form of a time history. In a dynamic time analysis, Mechanica calculates displacements, velocities, accelerations, and stresses in your model at different times in response to a time 720 Structural and Thermal Simulation varying load. Use dynamic time analyses if you are interested in transient or nonsteady forced response. For base excitation only, you can direct Mechanica to calculate the modal mass participation factors to enable you to better assess the accuracy of your results. Mechanica also calculates all valid measures for dynamic time analyses that you have defined for the model. You can direct Mechanica to report full results at specified time intervals. For dynamic time analysis with full results, you can animate results of a fringed display for each time interval of your analysis. Tip: You can define the equivalent of a base excitation case by placing a gravity load on the model. Requirements • • 1 modal analysis 1 or more load sets To Create a Dynamic Time Analysis 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Dynamic>Time from the File menu. The Dynamic Time Analysis dialog box appears. 3. Enter a name for the analysis. A description is optional. 4. Select one of the following options: o Load Functions o Base Excitation 5. Click the following tabs on the dialog box to select additional options for the dynamic time analysis: o Modes o Previous Analysis o Output 6. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. . 721 Structural and Thermal Simulation - Help Topic Collection Dynamic Frequency Analysis Overview Description Dynamic frequency analysis measures the response of a system to a periodic or cyclical, frequency-dependent load. The load input takes the form of a driving frequency with corresponding amplitudes. In a dynamic frequency analysis, Mechanica calculates the amplitude and phase of displacements, velocities, accelerations, and stresses in your model in response to a load oscillating at different frequencies. Use dynamic frequency analyses if you are interested in a steady-force response, for example, cyclic loading. For base excitation only, you can direct Mechanica to calculate the modal mass participation factors to enable you to better assess the accuracy of your results. Mechanica also calculates all valid measures for dynamic frequency analyses that you have defined for the model. You can direct Mechanica to report full results at specified frequency intervals. Tip: You can define the equivalent of a base excitation case by placing a gravity load on the model. Requirements • • 1 modal analysis 1 or more load sets To Create a Dynamic Frequency Analysis 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Dynamic>Frequency from the File menu. The Dynamic Frequency Analysis dialog box appears. 3. Enter a name for the analysis. A description is optional. 4. Select one of the following options: o Load Functions o Base Excitation 5. Select the Include frequency steps from table function check box if you want to ensure that the solution includes all steps in a table input function, not just those that Mechanica selects automatically. 6. Click the following tabs on the dialog box to select additional options for the dynamic frequency analysis: o Modes o Previous Analysis 722 . Structural and Thermal Simulation o Output 7. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. Dynamic Random Analysis Overview Description Dynamic random analysis measures the response of a system to a power spectral density function (PSD). The load input is force or acceleration PSD over a range of frequencies. Because the spectral density curves are obtained by sampling over a period of time, the longer the sampling time, the more accurate the curve. Results are reported in terms of a response PSD. In a dynamic random analysis, Mechanica calculates these power spectral densities and RMS values of displacements, velocities, accelerations, and stresses at points in your model in response to a load of specified PSD. Use a dynamic random analysis if: • • the loading of your model can be described statistically by a random process you are interested in evaluating RMS responses or power spectral densities For base excitation only, you can direct Mechanica to calculate the modal mass participation factors to enable you to better assess the accuracy of your results. Mechanica also calculates all valid measures for dynamic random analyses that you have defined for the model. You can obtain results for the PSD of a quantity at a point by defining measures. You can also define measures that yield the RMS value or apparent frequency of a quantity. Tip: You can define the equivalent of a base excitation case by placing a gravity load on the model. The PSD is equal to gravity squared over frequency (PSD = G^2/F) for this case. Requirements • • 1 modal analysis 1 or more load sets To Create a Dynamic Random Analysis 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Study dialog box appears. 2. Select New Dynamic>Random from the File menu. The Dynamic Random Analysis dialog box appears. . 723 Structural and Thermal Simulation - Help Topic Collection 3. Enter a name for the analysis. A description is optional. 4. Select one of the following options: o Load Functions o Base Excitation 5. Select the Include frequency steps from table function check box if you want to ensure that the solution includes all steps in a table input function, not just those that Mechanica selects automatically. 6. Click the following tabs on the dialog box to select additional options for the dynamic random analysis: o Modes o Previous Analysis o Output 7. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. Dynamic Shock Analysis Dynamic shock analysis measures the response of a system to a response spectrum. The load input is a base excitation with a response spectrum of either displacement, velocity, or acceleration. Dynamic shock analysis is not used for impulsive loads that vary with respect to time. In a dynamic shock analysis, Mechanica calculates maximum values of displacements and stresses in your model in response to a base excitation with a specified response spectrum. Use dynamic shock analysis if you are interested in subjecting your model to earthquake-like motion. Do not use this analysis type for impulse response. Mechanica also automatically calculates all measures valid for a static analysis. You need one constrained modal analysis before defining a dynamic shock analysis. These items appear on the Shock Analysis Definition dialog box: • • • • Direction of Base Excitation Previous Analysis Response Spectrum Output To Create a Dynamic Shock Analysis 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select New Dynamic>Shock from the File menu. 724 . Structural and Thermal Simulation The Shock Analysis Definition dialog box appears. 3. Enter a name for the analysis. A description is optional. 4. Enter WCS coordinates for Direction of Base Excitation to specify the direction the constrained parts of your model move in response to the forcing function. For 2D models, enter only X and Y coordinates. 5. Click the following tabs on the dialog box to select additional options for the dynamic shock analysis: o Previous Analysis o Response Spectrum o Output 6. Click OK when you complete the dialog box. The dialog box reappears displaying the name, type, and description of the new analysis. To Use Previous Analysis Results in a Dynamic Analysis This procedure assumes you are in the dialog box for creating one of these analysis types: dynamic time, dynamic frequency, dynamic random, or dynamic shock. 1. Click the Previous Analysis tab on the dialog box. 2. If you want to use the results from a previously run modal analysis associated with a different design study, select the check box Use Modes From Previous Design Study. If you do not select this check box, Mechanica runs a modal analysis as part of running your dynamic analysis. 3. Select the following items to include in your dynamic analysis: o design study (if applicable) o analysis The name of the constraint set for the modal analysis you selected appears in the Constraint Set field. To Define the Response Spectrum for a Dynamic Shock Analysis This procedure assumes you are in the Shock Analysis Definition dialog box. 1. Click the Response Spectrum tab on the dialog box. 2. Use the default function of frequency, uniform, to define the response spectrum curve for the base excitation, or click the ƒ(x) button to select or create a different function. 3. Select a quantity for the response spectrum curve—Displacement, Velocity, or Acceleration. 725 Structural and Thermal Simulation - Help Topic Collection 4. Select a Modal Combination Method option to determine how the contributions of the modes are combined to calculate results—SRSS or Absolute Sum. To Select Output Options for a Dynamic Analysis This procedure assumes you are in the dialog box for creating one of these analysis types: dynamic time, dynamic frequency, dynamic random, or dynamic shock analysis. 1. Click the Output tab on the analysis dialog box. 2. Select the quantities and factors that you want Mechanica to calculate. o For dynamic time, frequency, or shock analysis, you can select Stresses, Rotations, Ply Stresses (for laminates), or Mass Participation Factors (available only for dynamic analyses with base excitation). o For dynamic random analysis, you can select Full RMS Results For Displacements And Stresses. Note: If you are creating a dynamic shock analysis, skip the remaining steps. 3. Select an option for specifying the Output Intervals for which you want results—Automatic Intervals Within Range or User-defined Output Intervals. If you select User-defined Output Intervals, different items appear on the tab. Continue with steps 5 through 8. 4. If you selected Automatic Intervals Within Range, you can specify a Time Range or Frequency Range over which you want Mechanica to report results for your analysis: o For dynamic time analysis, enter the minimum time for the Time Range. You can select Automatic to use the default maximum time or User-defined to enter a different maximum time. o For dynamic frequency or random analyses, enter the minimum frequency of excitation for the Frequency Range. You can select Automatic to use the default maximum frequency or User-defined to enter a different maximum frequency. Note: If you selected Automatic Intervals Within Range, skip the remaining steps. 5. Enter the Number Of Master Intervals in the time or frequency range at which you want results reported. Mechanica displays the specified number of rows in the list of master intervals. 726 Structural and Thermal Simulation 6. Use the default values for each time or frequency interval to specify the spacing between intervals or click the User-defined Steps button to enter values. If you click User-defined Steps, you can use the Space Equally button to evenly space the steps. 7. For dynamic time and frequency analyses only, select the check boxes next to the intervals for which you want to save full results. Mechanica does not report full results for dynamic random analysis. You can also click for full results at all intervals or click results for all intervals. to turn off full 8. Enter a number for Measures Output Intervals Per Master Interval. To Select Mode Options for a Dynamic Analysis This procedure assumes you are in the dialog box for creating one of these analysis types: dynamic time, dynamic frequency, or dynamic random analysis. 1. Select an option for Modes Included from the modal analysis in the dynamic analysis—All or Below specified frequency. 2. If you selected Below specified frequency, enter a frequency value. 3. Select one of these options for assigning damping coefficients to the modes in the analysis: o o o For all modes For individual modes Function of frequency 4. If you selected For all modes in step 3, enter a value without a % symbol for the damping coefficient you want to assign to all modes. 5. If you selected For individual modes in step 3, enter damping coefficient values for each mode in the list that appears for this option. You can use the Fill button to change all zero values to the percent value immediately above them. Use the Clear button to change all values to zero. 6. If you selected Function of frequency in step 3, click f(x) to select or define a damping coefficient function. 727 Structural and Thermal Simulation - Help Topic Collection To Select Load Functions for a Dynamic Analysis This procedure assumes you have selected the Load Functions option on the dialog box for creating one of these analysis types: dynamic time, dynamic frequency, or dynamic random analysis. 1. If you want Mechanica to combine the loads of all selected load sets, select Sum Load Sets. 2. Select one or more load sets. 3. Use the default time or frequency dependence function for each selected load set, or click the f(x) button next to any load set if you want to select or create a different function. To Specify Base Excitation for a Dynamic Analysis This procedure assumes you have selected the Base Excitation option on the dialog box for creating one of these analysis types: dynamic time, dynamic frequency, or dynamic random analysis. 1. Use the default function for Time Dependence or Frequency Dependence, or click the ƒ(x) button to select or create a different function. 2. Enter WCS coordinates to specify the direction in which the constrained parts of your model move in response to the forcing function. For 2D models, enter only X and Y coordinates. 3. Select an option for calculating displacement, velocity, and acceleration results relative to ground or to supports. Results Output Intervals Use this item to specify the number of intervals in the time or frequency range at which you want Mechanica to report results. If you use the default, Automatic Intervals Within Range, Mechanica selects appropriate intervals at which to report results but does not calculate full results at any step: • • For dynamic time analysis, you can specify a time range over which you want Mechanica to report results by entering a minimum time and maximum time. For dynamic frequency and dynamic random analyses, you can specify a frequency range by entering minimum and maximum frequencies. If you select User-defined Output Intervals, the following options appear: • Number of Master Intervals — Enter the number of master intervals at which you want Mechanica to report results. You can specify up to 999 728 Structural and Thermal Simulation • • • • • • intervals. A row is added to the table for each interval. In general, computation time increases with the number of intervals. Full Results — For dynamic time and dynamic frequency analyses only, select the check boxes next to the intervals for which you want to save full results. User-defined Steps — Click this button to enter values for spacing the steps. Space Equally — Enters evenly spaced values for the steps. This button is only available when you click User-defined Steps. (Select All) — Click this button if you want full results for all intervals. (Deselect All) — Click this button if you do not want full results for all intervals. Measures Output Intervals per Master Interval — Enter a positive number up to 999. In general, computation time increases with the number of measures output intervals. Response Spectrum Options for Dynamic Shock Analysis Use the following options to define the response spectrum curve for the base excitation. These items appear on the Response Spectrum tab on the Shock Analysis Definition dialog box: • Response Spectrum f(x) — Select a function of frequency to define the response spectrum curve. The default response spectrum curve function is uniform, which means the frequency dependence of the base excitation is uniform over the frequency range. To select a different function, click the f(x) button. The Functions dialog box appears. You can select an existing function or click New to define a new function. • Spectrum of — Select one of these quantities for the response spectrum curve: o o o • Displacement Velocity Acceleration Modal Combination Method — Select the method the engine uses to combine modes when calculating results: o o SRSS — the square root of the sum of the squares Absolute Sum — the sum of the absolute values of the contributions of each mode 729 Structural and Thermal Simulation - Help Topic Collection Use Modes From Previous Design Study Mechanica uses the modes from a modal analysis to calculate a dynamic analysis. You can include the modal analysis in one of these ways: • Have Mechanica run the modal analysis as part of running the dynamic analysis. The dialog box displays the name of a modal analysis and the constraint set for that analysis. If you have multiple modal analyses, you can select the analysis you want to use. Make sure Use Modes From Previous Design Study is not selected. • Use results from a previously run modal analysis. Select the option Use Modes From Previous Design Study. The dialog box displays the name of a standard design study, modal analysis, and the constraint set for the selected modal analysis. If you have multiple studies or analyses, you can select the ones you want to use. Keep these points in mind when using this option: o o You cannot place the current dynamic analysis in the same design study as the previous modal analysis you select. The design study containing the previous modal analysis must be in the same directory as the design study in which you place the current dynamic analysis. You must run the design study that contains the modal analysis prior to running the current dynamic analysis so that the modes from the previous analysis are available. o Previous Analysis Options for Dynamic Analysis These items appear on the Previous Analysis tab on the dialog boxes for dynamic analyses: • Use Modes From Previous Design Study — Select this option to use results from a previously run modal analysis in the dynamic analysis. If this option is not selected, Mechanica runs the modal analysis as part of the dynamic analysis. Design Study — Select a design study to include in the dynamic analysis if you selected the option Use Modes From Previous Design Study. Modal Analysis — Select a modal analysis to include in the dynamic analysis. • • 730 Structural and Thermal Simulation • Constraint Set — Mechanica displays the constraint set for the selected modal analysis. Modes Included Use this item to specify which modes from the modal analysis you want included in the dynamic analysis. You can specify this in two ways: • • All — Select if you want to include all modes from the modal analysis in the dynamic analysis. Below Specified Frequency — Select to limit the modes included. Enter a frequency in the entry box. Frequency Range Enter the minimum and maximum frequencies of excitation for the range over which you want Mechanica to report results for dynamic frequency and dynamic random analyses. The minimum frequency must be greater than or equal to 0. The default maximum frequency is Automatic, which is 1.5 times the highest natural frequency calculated. If you select the User-defined option, you can enter a value for the maximum frequency. For Individual Modes Use this option to assign a separate damping coefficient to each mode in the dynamic analysis. When you select For individual modes, a numbered list of modes appears on the Modes tab. The number of modes in the list is based on the modes from the previous modal analysis. Enter a value, without a % symbol, for each mode. After entering one or more values, you can click Fill to change all zero values to the percent value immediately above them. Use the Fill button to assign the last damping coefficient value in the list to the remaining modes at the end of the list. You can use the Clear button to change all the entries in the list back to zero. 731 Structural and Thermal Simulation - Help Topic Collection Function of Frequency Select this option to define damping as a function of frequency. Click the f(x) button. If you have previously defined a damping coefficient function, the Functions dialog box appears. Select an existing function or click New to define a new function. If you select New, the Function Definition dialog box appears. Use this dialog box to define a new function. To select a different function, click the f(x) button and the Functions dialog box appears. You select an existing function or click New to define a new function. Damping Coefficient (%) Use this item to assign damping coefficients to the modes in the analysis. The damping coefficient is the percentage of critical damping. A damping coefficient of 100% means the model is critically damped and does not vibrate freely. A damping coefficient of 1% means the amplitude decays by about 6% over one period of oscillation. You can select one of three methods of assigning damping coefficients: • • • For all Modes — Assigns a single damping coefficient to all modes. You enter a single value, without a % symbol, in the entry box. For Individual Modes — Assigns a separate damping coefficient to each mode in the analysis. Function of Frequency — Defines damping as a function of frequency. The normal range for damping coefficients is from 0% to 50%. If you enter values outside this range, Mechanica asks you to confirm each value. Calculate Quantities and Factors for Vibration Analysis Use this item to determine the type of results Mechanica calculates. For dynamic time, dynamic frequency, and dynamic shock analyses, select one of the following items if you want Mechanica to calculate full results: • • Stresses — Directs Mechanica to calculate stresses. If you do not need stress results, you can save disk space by clearing this item. This also results in dramatically reduced analysis time. Rotations — Directs Mechanica to calculate the rotation about each WCS axis over the entire model. 732 Structural and Thermal Simulation Mechanica never calculates rotations if your model consists only of 3D solid, 2D solid, or 2D plate elements, even if this item is selected. Rotations are always zero for these element types. • Ply Stresses — Directs Mechanica to calculate the ply-by-ply stress results. This option is only for models that have laminate shell properties defined. For dynamic random response analyses, select the following item if you want Mechanica to calculate full results: • Full RMS Results for Displacements and Stresses — Enables you to display fringe plots for RMS stress and RMS displacement results. For dynamic analyses with base excitation, select the following item if you want Mechanica to calculate factors important in determining if enough vibration modes obtained from modal analysis are included to ensure accurate results. • Mass Participation Factors — Directs Mechanica to calculate the modal mass participation factors. This may result in greatly increased computational time. You cannot access full results for quantities you deselect here. Mechanica calculates all measures valid for the analysis, regardless of your selections here. You can access results for measures through the summary report or by graphing the measure in a results window. Note: If you select Time/Frequency Eval when you define a dynamic measure, you can access results only through a results window. User-defined Steps Use this button to specify the spacing between steps in the time or frequency range. You can enter different values for each step. The values you enter must be in increasing order from step to step. When you click User-defined Steps, you can also use the Space Equally button to evenly space the steps. You cannot enter any values for the steps if you selected Auto for the maximum of the time or frequency range. The dialog box shows Auto for each step in the table. Output Options for Dynamic Analyses These items appear on the Output tab on the dialog box for dynamic analyses: • Calculate — Select the quantities and factors for which Mechanica calculates results. 733 Structural and Thermal Simulation - Help Topic Collection • Output Intervals (not available for dynamic shock analysis) — Specify the number of intervals in the time or frequency range at which you want Mechanica to report results. Mode Options for Dynamic Analyses These items appear on the Modes tab on the dialog boxes for dynamic time, dynamic frequency, and dynamic time analyses: • • Modes Included — Specify which modes from the modal analysis you want included in the dynamic analysis. Damping Coefficient (%) — Assign damping coefficients to the modes in the analysis. Mass Participation Factor Results For dynamic analyses, the engine writes some additional mass participation factor information to the summary file during a run. Immediately preceding the measure output for the analysis, the summary file contains a table with the same format as the frequency data for modal analyses. The columns of the table are: • • • • • Mode — mode number Frequency — frequency of indicated mode Mass Participation Factor — indicator of the relative participation of the mode Effective Mass — percentage indicator of participation of mode. This is the ratio of the mass participation factor divided by the total mass squared. Total Effective Mass — percentage indicator of participation of modes up to and including indicated mode. This is the sum of effective masses of modes up to and including indicated mode. Full Results Use this column to specify the intervals at which Mechanica reports full results. Mechanica always reports measure results, but only reports stresses, displacements, strains, and forces at intervals that you designate. You can also turn full results on or off for all intervals with the Select All and Deselect All buttons. This column does not appear for dynamic random analyses. Base Excitation You can use this option if the modal analysis you selected for your dynamic analysis contains at least one constrained modal analysis. Otherwise, Base Excitation is not available. 734 Structural and Thermal Simulation If no loads are defined on your model, you must define the dynamic analysis using base excitation. When you select Base Excitation, these items appear on the dialog box: • Time/Frequency Dependence — A default function to define base acceleration appears on the dialog box. Click the f(x) button if you want a different function, and the Functions dialog box appears. You select an existing function or click New to define a new function. If you click New on the Functions dialog box, the Function Definition dialog box appears. Use this dialog box to define a new function. • • Direction — Enter WCS coordinates that specify the direction in which the constrained parts of your model move in response to the forcing function. For 2D models, you only enter X and Y coordinates. Relative to — You can have displacement, velocity, and acceleration results calculated with respect to ground or to supports. Sum Load Sets You can select Sum Load Sets if you want Mechanica to merge the loads of all selected load sets. If you do not select Sum Load Sets, Mechanica calculates results separately for each load set. If you do select Sum Load Sets, Mechanica assumes that all load sets act simultaneously, and reports results for a single load set containing all loads in the selected sets. The combined results are associated with the first load set in the list. You can use the Sum Load Sets feature to mix loads with different functions in the same analysis. The exception is dynamic time simulations. You cannot mix load sets for a dynamic time simulation using the function impulse with load sets using any other function, but you can sum a series of load sets that all use the function impulse. Load Set Functions When you select a load set function, the function you select depends on the analysis type: Analysis Type dynamic time dynamic frequency Defines amplitude amplitude phasec Function of time frequency frequency Default impulsea uniformb zerod 735 Structural and Thermal Simulation - Help Topic Collection Analysis Type dynamic randome Defines load set power spectral density Function of frequency Default uniformb a. When the time function is impulse, an impulse load is applied at the minimum time. b. When the frequency function is uniform, the load is multiplied by 1 over the frequency range. c. The phase function is defined in radians. d. When the frequency phase function is zero, a zero radian phase angle over the frequency range is applied to the load. e. The frequency dependence functions you specify for a random response analysis are the PSD curves for each load set. The engine calculates the PSD response curves for local measures as a function of frequency. To select a different function, click the ƒ(x) button and the Functions dialog box appears. You can select an existing function or click New to define a new function. See Function Definition Dialog Box for information on defining new functions. Time Range Enter the minimum and maximum times for the range over which you want Mechanica to report results for a dynamic time analysis. The impulse load is applied at the minimum time. The minimum time must be greater than or equal to 0. The default maximum time is Automatic, which is three times the period of the first mode. If you use the Automatic option, the range will cover three oscillations for the first mode. If you select the User-defined option, you can enter a value for the maximum time. Direction of Base Excitation Enter WCS coordinates that specify the direction in which the constrained parts of your model move in response to the forcing function. For 2D models, you only enter X and Y coordinates. The software does not normalize the base excitation vector. It multiples the magnitude of the vector by the function you enter for Response Spectrum. 736 Structural and Thermal Simulation FEM Analysis About FEM Analysis After you define a FEM mode model, you can define an analysis that Mechanica runs using the FEA solver you select. In defining an analysis, you inform Mechanica which type of analysis you want and indicate the loads, constraints, materials, idealizations, and so forth you want considered. Defining a FEM analysis is an optional step. If you plan to run the FEA solver from within Mechanica, you need to define an analysis. However, in some cases, you may be primarily interested in generating a mesh to use with an offline solver instead. For this application, you do not need to define an analysis. The point in your design process at which you define an analysis depends on whether you are working with transient or retained meshes. If you work with transient meshes, you define a FEM analysis immediately after you define your modeling entities, and before you mesh the model. Those of you who work with retained meshes can define a FEM analysis anytime before you start a run, although you typically want to define loads and constraints first. You define a FEM analysis by selecting the Analysis>FEM Analysis command. The dialog box you use to define FEM analyses changes depending on whether you are specifying a structural or thermal analysis or a modal analysis. Using the FEM Analysis Command in FEM Mode To define a FEM analysis, use the Analysis>FEM Analysis command. After you select the FEM Analysis command, the SIM ANALYSES menu appears. This menu contains the following commands: • • New — Define a new analysis. If you select this command, the Analysis Definition dialog box appears. This dialog box changes depending on whether you are specifying a structural or thermal analysis or a modal alysis. Edit — Modify an existing analysis. If you select this command, Mechanica displays a list of analyses for you to choose from. Once you select an analysis, the Analysis Definition dialog box for that analysis appears. You use this dialog box to redefine the analysis. Copy — Copy an existing analysis under a new name. If you select this command, Mechanica displays a list of analyses for you to choose from. Once you select an analysis, you use the entry box in the message area to enter a name for the analysis copy. This function proves useful if you plan to run a number of analyses that have only minor differences. Delete — Delete an existing analysis. If you select this command, Mechanica displays a list of analyses for you to choose from. Once you select an analysis, Mechanica deletes it. • • 737 Structural and Thermal Simulation - Help Topic Collection Defining a FEM Analysis Use the FEM Analysis>New command to define a structural or thermal FEM analysis. When you select this command, the Analysis Definition dialog box appears. This dialog box lets you specify the analysis type as well as the load and constraint sets that will be active for the analysis. Note: If you want to define a modal analysis, see Defining a Modal FEM Analysis. The Analysis Definition dialog box version you use for FEM analyses includes the following: • • • Type — Specify the type of analysis you want to run, in this case Structural or Thermal. Description — Optionally, enter a description of the analysis. Constraint Sets or Boundary Condition Sets — Use this area to add and remove constraint or boundary condition sets you have defined for your model. You can also use this area to suppress constraint or boundary condition types within the set. Mechanica lists all sets you have added on a table in this area. This area includes three buttons: o Add — Add a constraint set to the table. When you click this button, Mechanica displays a list of all constraint sets in the model. You can select one or more constraint sets to add. o Remove — Remove a highlighted constraint set from the table. o Suppress Constr or Suppress BCs — Suppress one or more constraint or boundary condition types in the set. Load Sets — Use this area to add and remove load sets defined for your model. You can also use this area to suppress load types within the set. Mechanica lists all load sets you have added on a table in this area. This area includes three buttons: o Add — Add a load set to the table. o Remove — Remove a highlighted load set from the table. o Suppress Loads — Suppress one or more load types in the load set. • Defining a Modal FEM Analysis Use the FEM Analysis>New command to define a modal FEM analysis. When you select this command, the Analysis Definition dialog box appears. This dialog box lets you specify the analysis type as well as the load and constraint sets that will be active for the analysis. Note: If you want to define a structural or thermal analysis, see Defining a FEM Analysis. The Analysis Definition dialog box you use for modal analyses includes the following: • • 738 Type — Specify the type of analysis you want to run, in this case Modal. Description — Optionally, enter a description of the analysis. Structural and Thermal Simulation • Constraint Sets — Use this area to add and remove constraint sets you have defined for your model. You can also use this area to suppress constraint types within the set. Mechanica lists all constraint sets you have added on a table in this area. This area includes these buttons: o Add — Add a constraint set to the table. When you click this button, Mechanica displays a list of all constraint sets in the model. You can select one or more constraint sets to add. o Remove — Remove a highlighted constraint set from the table. o Suppress Constr — Suppress one or more constraint types in a set. Parameters — Use this area to define the parameters you want the modal analysis to observe. This area includes these fields: • • • Number of Modes — Specify the number of modes you want the NASTRAN or ANSYS solver to generate data for. The default is 4 modes. First Frequency Guess — Provide an estimate of the first mode natural frequency. NASTRAN is the only solver that uses the information you enter in this field. The default is 1.000. Frequency Range — Using the From and To fields, specify the lower and upper ends of the frequency range you want to evaluate. To Create an Output File If you plan to perform finite element analyses on your model using an offline FEA program, you must create an output file, or deck, for the model's mesh data using these steps: 1. Select Analysis>FEM Solution. The Run FEM Analysis dialog box appears. 2. Select the format of the output file from the Solver scroll list. 3. Select the analysis type from the Analysis option menu. Mechanica sets up the output deck for the type of analysis you select. 4. Use the Linear or Parabolic buttons to select the order of the finite elements. 5. Select the analyses that you want to include in the output deck from the Analyses list. This step determines the constraints, boundary conditions, and loads that Mechanica outputs. 6. If you do not want to use the WCS as the reference coordinate system, select a different coordinate system from the Coord System option menu. 7. If desired, use the Aux Coord Systems area to select one or more auxiliary coordinate systems to include in the output deck. 8. If you are outputting the deck for the NASTRAN solver and want to use a customized NASTRAN template, select a NASTRAN template. 9. Click Output To File from the lower set of buttons and enter a name for the output file in the text box. 10. Click OK. Mechanica creates the mesh output file in the working directory. The REVIEW MESH menu appears, enabling you to evaluate specific aspects of the mesh output in the work area. 739 Structural and Thermal Simulation - Help Topic Collection To Review the Mesh 1. Select Analysis>FEM Solution. The Run FEM Analysis dialog box appears. 2. Select the combination of options in the Run FEM Analysis dialog box that you wish to view. 3. Select Output to File and, if you do not want to use the default filename, specify a different filename. 4. Click OK. Mechanica creates the mesh output file in the working directory and re-displays the meshed model with internal element edges shown in gray. The REVIEW MESH menu appears. 5. Select commands from the REVIEW MESH menu to view specific aspects of the mesh output. 6. When you are finished viewing the mesh data, you can: o output a file for use with an offline FEA program o solve the model from within Mechanica using one of the supported FEA solvers To Solve a FEM Model Online or in the Background 1. 2. 3. 4. 5. Select Analysis>FEM Solution. The Run FEM Analysis dialog box appears. Select the FEA program to access. Select the analysis type from the Analysis option menu. Use the Linear or Parabolic buttons to select the order of finite elements. Select the analyses that you want to include in the solver run from the Analyses list. This step determines the constraints, boundary conditions, and loads that Mechanica outputs. 6. If you do not want to use the WCS as the reference coordinate system, select a different coordinate system from the Coord System option menu. 7. If desired, use the Aux Coord Systems area to select one or more auxiliary coordinate systems to include in the output deck. 8. If you are using the NASTRAN solver and want to use a customized NASTRAN template, select a NASTRAN template. 9. Select either Run On-Line or Run in Background to indicate how Mechanica will conduct the solving process. 10. Click OK. Mechanica creates an output file for the FEA solver to use as input for the run. This file is named partname.ext file (where .ext is the appropriate three-letter file extension for the selected FEA solver). Once the FEA solver solves the mesh model, Mechanica stores the results in an .frd file. You can then view your model in the postprocessor, displaying the results of the finite element analysis in a variety of tabular and graphical formats. Note: If there is already an .frd file that contains results, the system prompts you to overwrite the existing .frd file. 740 Structural and Thermal Simulation To Create a Modal FEM Analysis Select Analysis>FEM Analysis>New. The Analysis Definition dialog box appears. Enter a name for the analysis. Select the Modal analysis type from the Type option menu. If desired, enter a description of the analysis in the Description field. Click the Add button in the Constraint Sets area. The Sets Selection dialog box appears. 6. Select one or more constraint sets and click OK. The dialog box closes and Mechanica adds the constraint sets to the table. 7. Specify appropriate modal parameters in the Parameters area. 8. Click Ok to accept the analysis definition. 1. 2. 3. 4. 5. Suppressing Loads, Constraints, and Boundary Conditions Use the Suppress Loads, Suppress Constr, or Suppress BCs button on the Analysis Definition dialog box to suppress one or more load, constraint, or boundary condition types in the set. For example, you might want to suppress a radiation boundary condition in a Thermal set that includes both a prescribed temperature and a convection condition. If you suppress a load, constraint, or boundary condition type, Mechanica omits all entities of that type from the set, ignoring the omitted entities at run time. When you click any of these buttons, a dialog box appears, enabling you to select appropriate entity types. The dialog box includes these items: • Entity type check boxes — Use these check boxes to suppress individual load, constraint, or boundary condition types. There is a check box for each kind of entity you can suppress for the type of set you are working with. As an example, if you are working with a boundary condition set, the dialog box provides Temperature, Convection, and Radiation check boxes. — Select all entity types in the check box list. — Deselect all entity types in the check box list. • • NASTRAN Templates You control what goes into the .nas file through a NASTRAN template file that you specify in the NASTRAN Analysis Template area of the Run FEM Analysis dialog box. The NASTRAN Analysis Template area includes a file selector that you can use to browse for a NASTRAN template file. Once you select a template file, you can set that file as the default template for the model by clicking the Default button. 741 Structural and Thermal Simulation - Help Topic Collection The format of the NASTRAN template file is as follows: [optional, user supplied File Management and NASTRAN statements] [optional, user supplied Executive Control statements] @include_promesh_executive_control_section (optional) [optional Executive Control statements] CEND [optional Case Control commands] @include_promesh_case_control_section (optional) @include_promesh_case_control_section_as_comments (optional) [more optional, user supplied Case Control commands] BEGIN BULK [optional, user supplied Bulk Data instructions] @include_promesh_bulk_data_section (optional) [more optional, user supplied Bulk Data instructions] ENDDATA There are four special optional lines in this template file: @include_promesh_executive_control_section @include_promesh_case_control_section @include_promesh_case_control_section_as_comments @include_promesh_bulk_data_section If these lines are present in the template file (case-insensitive), the software replaces them with data output from Mechanica FEM mode as it processes the NASTRAN input file. Fixing Parabolic Elements If you click the Fix Elements button in the Run FEM Analysis dialog box, Mechanica slightly straightens excessively curved edges of solid and shell mesh parabolic elements. Mechanica accomplishes this by moving the mid-edge nodes off the part geometry to a setting you determine using the mid ratio mesh check. Note that using this approach improves mesh quality, but at some expense to the mesh's geometric accuracy. Alternate methods of improving mesh quality include: • • performing additional mesh improvement passes establishing tighter local mesh control in problem areas Storing and Retrieving FEA Results After an FEA program has successfully solved a FEM part or assembly, the system stores both the model's mesh data and FEA results in a single database file with the name model.frd. This occurs regardless of whether you solved the model online or in the background. To avoid re-meshing or re-solving the model, you can use the File>Open FEM Results command to retrieve the .frd file. The system retrieves the model and puts you in the system environment corresponding to the state captured in the .frd file. 742 Structural and Thermal Simulation Thus, if you retrieve the file with FEA program results, you automatically enter the postprocessor. When you store or retrieve the .frd file, keep the following in mind: • If more than one analysis is available, you can select a different analysis for your model and send it to the solver. When you click OK on the Run FEM Analysis dialog box and the system detects an .frd file that already contains solution results, the system prompts you to decide whether or not to overwrite the existing results. o If you select Yes, the system runs the analysis and stores the results in the present .frd file. o If you select No, the system prompts for the name of the file where you want to store the new results. Thus, the original .frd file remains intact. You can only retrieve an .frd file that contains results. You can only retrieve a stored mesh and results file that corresponds to the current model in session. If the system detects that you modified the model, it warns you that the model does not correspond to the stored mesh and terminates the retrieval process. Mechanica only allows changes to the model that do not cause changes in the mesh. For example, changing the value of a pressure load is acceptable, but adding or deleting a hard point or a force is not. • • Using Solver Results in the Postprocessor Your ability to view FEA solver results in the Mechanica postprocessor depends on the solver you used as well as whether you ran the solver online or output a deck. Here is an overview: • NASTRAN solver — You can view analysis results in the Mechanica postprocessor regardless of whether you run NASTRAN from within Mechanica or output a deck for external use with the NASTRAN solver. However, if you output a deck and alter it before running it with the solver, you may not be able to postprocess some or all of the results in Mechanica. ANSYS solver — You can only view analysis results in the Mechanica postprocessor if you run the FEA solver from within Mechanica. If you choose, instead, to output a deck for use outside Mechanica, you cannot import the results back into Mechanica. Unsupported solvers — You cannot view the solver results in the Mechanica postprocessor. • • Output Formats The options you select from the Output to File dialog box determine the format and element types included in the output file. The following is a summary of supported FEA programs that generate shell and solid element meshes. • • ANSYS MSC/NASTRAN 743 Structural and Thermal Simulation - Help Topic Collection • FEM Neutral Format FEM Neutral Format The FEM Neutral Format enables data exchange between Pro/ENGINEER and FEA programs, and creates model descriptions using references to existing data. A FEM Neutral Format file contains information about an entire finite element model, including the following data: • • • • • definitions of element types description of FEM topology (nodes and elements) applied loads, constraints, boundary conditions analysis definitions. Note that, for modal analysis definitions, the solver may ignore the frequency range you specified in the Analysis Definition dialog box. calculated results To output your model to the FEM Neutral Format, select the PTC FEM Neutral Format option from the Solver option menu on the Run FEM Analysis dialog box. See FEM Neutral Format File for details. MSC/NASTRAN Writing an MSC/NASTRAN output file creates an MSC/NASTRAN file in ASCII format called filename.nas. The following table lists the mesh elements written to the MSC/NASTRAN output file for the various mesh types and idealizations. Element Type Shells Triangular — Linear Triangular — Parabolic Quadrilateral — Linear Quadrilateral — Parabolic Tetrahedral Solids Beams Trusses Springs Masses 744 Linear and Parabolic MSC/NASTRAN CTRIA3 CTRIA6 CQUAD4 CQUAD8 CTETRA CBEAM CROD CBUSH CONM2 Structural and Thermal Simulation Element Type Rigid Links Weighted Links Gaps MSC/NASTRAN RBAR RBE3 CGAP (element coordinate system and orientation) PGAP (properties) Be aware that Mechanica does not support or output thermal loads and constraints. Also, for gaps, stiffness properties are specified on the PGAP card. These properties include UO, the initial gap value, KA, the normal stiffness, and KT, the slide stiffness. MSC/NASTRAN supports zero-length idealizations—idealizations that have no length, such as an idealization between a point on a surface and the surface itself—for gaps and advanced springs only. For an MSC/NASTRAN solution, you can use the fem_solver_time_limit config.pro option to interrupt the solver after the specified time limit. The default value is 60 (60 minutes). If you place simulation entities on layers and want to review a file containing layer data, you can use the sim_output_ids_for_layers config.pro option to generate an XML file that lists the layers. Mechanica outputs this file at the same time that it outputs the .nas file and places it in the same directory as the .nas file. ANSYS Writing an ANSYS output file creates a PREP7 file in ASCII format called filename.ans. Use the fem_which_ansys_solver config.pro option to specify which ANSYS solver you plan to use—Frontal, Iterative, or Powersolver. The values are: FRONTAL (default), ITERATIVE, and POWERSOLVER. The following table lists the mesh elements written to the ANSYS output file for the various mesh types and idealizations. Analysis Shells Linear Thermal Linear Structural Parabolic Structural Tetrahedral Solids Linear Thermal ANSYS SHELL57 SHELL43 SHELL93 SOLID70 745 Structural and Thermal Simulation - Help Topic Collection Analysis Parabolic Thermal Linear Structural Parabolic Structural Beams Trusses Springs Advanced Springs Masses Gaps All All All All All All ANSYS SOLID87 SOLID92 SOLID92 BEAM44 LINK8 COMBIN14 MATRIX27 MASS21 COMBIN40 Note that Mechanica does not output radiation to ANSYS. Also, for gaps, the gap value is Gap and the normal stiffness is K2. ANSYS supports zero-length idealizations—idealizations that have no length, such as an idealization between a point on a surface and the surface itself—for gaps and advanced springs only. To Create a FEM Analysis 1. Select Analysis>FEM Analysis>New. 2. The Analysis Definition dialog box appears. Enter a name for the analysis. 3. If you are working in Structure, select the Structural analysis type from the Type option menu. 4. If desired, enter a description of the analysis in the Description field. 5. Click the Add button in the Constraint Sets (Structural) or Boundary Condition Sets (Thermal) area. The Sets Selection dialog box appears. 6. Select one or more constraint or boundary condition sets and click OK. The dialog box closes and Mechanica adds the constraint sets to the table. 7. If you want to suppress one or more constraint or boundary condition types in the set, click Suppress Constr or Suppress BCs. The Constraint Types or BC Types dialog box appears. 8. Select individual constraints or boundary conditions to suppress or click to select all constraint types. Click OK to close the dialog box. 9. Perform steps 5 through 8 to complete the Load Sets area. 10. Click Ok to accept the analysis definition. 746 Structural and Thermal Simulation Analysis and Design Study Workflow This workflow shows the process of creating, modifying, and running analyses and design studies. You initiate all of these activities, as well as monitoring the progress of a run, from the Analyses and Design Studies dialog box. To access the dialog box, select the Mechanica Analyses/Studies command from the Analysis menu. • Create an Analysis or Design Study Create a new analysis or design study using the options on the File menu. • Modify an Existing Analysis or Design Study Select the analysis or design study from the list and use the Edit>Analysis/Study menu option to modify it. • Set Up an Analysis or Design Study Run • Open the Run Settings dialog box to designate the output and temporary files and their format for the run. Specify the solver and memory allocation you want Mechanica to use for the run. • Check Your Model Check your model before you start the run using the Info>Check Model menu option. • Start, Stop, and Restart a Run Use the Run menu or the buttons on the toolbar to start, stop, or restart a run. 747 Structural and Thermal Simulation - Help Topic Collection • • Monitor a Run • Use the Run Status window to monitor a run. Select Detailed Summary to see more information about the run. Select the Info>Diagnose menu option to troubleshoot run problems. Strategy: Identifying and Resolving Potential Trouble Spots in a Model To help identify potential trouble spots or modeling errors before you invest a great deal of time in a model, we recommend that you obtain a first pass of the results within a relatively short period of time. • Define and run an analysis using the quick check convergence option. With this option, the engine runs the analysis at a polynomial order of 3. You can then check stress and deformation results for structural analyses, or temperature gradient and flux results for thermal analyses. These results can reveal problems in the model, such as cracks or missing loads and constraints. Then, you might want to consider running an analysis with reduced tolerance or reduced maximum polynomial order values. For example, if the model is large and it would require several hours to achieve 10% convergence, consider first setting convergence to 20% and the maximum p-order to 6. Once the run is complete, review a fringe plot of the p-level reached by each edge. For edges that reach the maximum p-order, you may want to make the following changes: o o o Spread any loads or constraints over a larger area. Use AutoGEM's feature isolation settings to counteract singularities. Seed your model with datum points near the high p-order zones to adjust the size of elements so the elements in the high p-order zones are smaller. Add more elements. • o 748 Structural and Thermal Simulation About Creating and Running Analyses and Design Studies Mechanica uses analyses and design studies to provide information about your model's strengths and weaknesses under different conditions. When you create an analysis, you specify the loads and constraints on the model and how you want Mechanica to calculate the effects of the loads and constraints on your model. You can run several different types of analyses depending on what you want to evaluate in results. For example, if you want to study the effect of fatigue on your model, you can create a fatigue analysis. Design studies use one or more analyses to study the effects of changes to your model (standard studies), to see how sensitive your model is to changes (sensitivity studies), or to see what combination of parameters makes your model the best or strongest (optimization studies). For example, an optimization study might vary the material your model is made of to see which material is the strongest and withstands the most pressure. Use the Analysis>Mechanica Analyses/Studies command to create, modify, run, and monitor analyses and design studies. The type of model and the items you select in your analyses and design studies determine the quantities, locations, and displays that are available in results. When you select the Mechanica Analyses/Studies command, the Analyses and Design Studies dialog box appears. Use this dialog box to define, control, and run analyses and design studies. In working with this dialog box, you typically follow a step-by-step process that begins with defining an analysis or study and progresses to running and monitoring the analysis or study. Creating Design Studies About Design Studies Mechanica uses design studies to calculate results for an analysis or it uses an analysis to examine alternatives to your design. You can use design studies to determine the effect of design parameters on your model's shape and behavior. Performing various design studies provides information you can use to determine how sensitive your model is to a shape change as well as which shape changes make the most sense in terms of model behavior. To create and modify design studies, use the Analysis>Mechanica Analyses/Studies command to access the Analyses and Design Studies dialog box. Select the File>New Design Study menu option to create a new study or the Edit>Analysis/Study menu option to modify an existing study. The Design Study Definition dialog box appears in both cases. 749 Structural and Thermal Simulation - Help Topic Collection Working toward an optimized model usually involves these types of design studies: standard, global or local sensitivity, and optimization. In a design study: • • You specify one or more analyses for which you want Mechanica to calculate results. You indicate whether you want Mechanica to calculate those results for the original model or for variations on the original model. If you delete a component of a design study, you need to redefine the study. Strategies for Running a Standard Design Study There are a number of strategies to consider before running a design study. To learn more about these strategies, read the following: • • • • • Memory Allocation Restrictions When Specifying Multiple Working Directories Managing Memory and Swap Space Guidelines for Managing Disk Space Resources Managing Performance Although these topics pertain to both Structure and Thermal users, Structure runs are more computationally intensive. Therefore, these strategies are probably more helpful to Structure users. Design Study Files Mechanica creates three different types of files when you run a design study: • Engine Input Files — When you start the run, Mechanica writes engine input files. These files include the following (study is the name of the design study you selected): study.mdb—a copy of the model file—and study.lok. The study.lok file prevents you from defining result windows before sufficient data is available. Mechanica deletes the file when the run has progressed sufficiently to enable you to define result windows. For example, if a run terminates with an error, you may be able to access partial results if the study.lok file is gone. Mechanica places these files in a subdirectory with the same name as the design study you are running. It places the subdirectory within the directory for output files that you specify in the Run Settings dialog box. • Temporary Working Files — The engine creates temporary working files while the run is in progress and deletes the files when the run is finished. Mechanica creates a temporary subdirectory for these files called study.tmp 750 Structural and Thermal Simulation • (study is the name of the design study you are running). This subdirectory is located in the directory for temporary files that you specify in the Run Settings dialog box. Output Files — The engine also creates output files in which it places the results of the design study. These files contain the results of the previous run of the same design study, and may contain useful results even if the run did not complete successfully. The engine output files are placed in the same subdirectory as the engine input files for the design study. For more information on these files, see Files Created by Mechanica. Creating Design Studies Analyses and Design Studies Dialog Box When you select the Analysis>Mechanica Analyses/Studies command, the Analyses and Design Studies dialog box appears. Use this dialog box to manage and run your analyses and design studies. The Analyses and Design Studies dialog box includes the following: • Menu bar — Perform the following activities using the options on the menu bar: o Create new analyses and design studies using the options available on the File menu. o Modify existing analyses and design studies using the Edit>Analysis/Study menu option. You can also copy or delete analyses or design studies using the options on the Edit menu. o Set up a run using the Run>Settings menu option or selecting the Configure Run Settings button on the toolbar to display the Run Settings dialog box. o Create a batch file to run more than one analysis or design study at a time using the Run>Batch menu option. o Check your model before you start a run by using the Info>Check Model menu option. o Start, stop, or restart analyses and design studies using the options on the Run menu or the buttons on the toolbar. o Monitor the status and view a detailed summary of a run using the Info>Status menu option. o Review the error and warning messages generated during a run using the Info>Diagnose menu option. Toolbar — Use the toolbar buttons to perform many of the functions available on the menu bar. Analyses and Design Studies Table — Lists the name and type of analyses and design studies for the current model. To perform an action on a specific analysis or design study, highlight it in the list and select the action from the options on the menus or use the toolbar buttons. Description — Displays a description, if available, of the analysis or design study you select from the list. • • • Closing the dialog box does not initiate any actions. 751 Structural and Thermal Simulation - Help Topic Collection Design Study Definition Dialog Box Use this dialog box to create, modify, or review a design study. Depending on the type of design study you are working with, and the product you are in, the dialog box displays different items. You can create, modify, or review the following types of design studies: • Standard — Calculates results for an analysis or analyses. You can specify different parameter settings for the analysis. Mechanica creates a default standard study for each analysis you created for your model. • • • Global Sensitivity — Calculates the changes in your model's measures when you vary a parameter over a specified range. Mechanica does this by calculating measure values at regular intervals in a parameter's range. Local Sensitivity — Calculates the sensitivity of your model's measures to slight changes in one or more parameters. Optimization — Adjusts one or more parameters to best achieve a specified goal or to test feasibility of a design, while respecting specified limits. Mechanica adjusts the model's parameters in a series of iterations through which it tries to move closer to the goal while satisfying any limits. If you have no goal, Mechanica simply tries to satisfy your limits. An optimization with no goal is sometimes called a feasibility study. Standard Study for Structure and Thermal Standard Study After you select Standard as your type of design study, you then select one or more analyses from the list of all analyses you defined for the model. Mechanica calculates results separately for each analysis you specify when you run the design study. You can also view results for each analysis separately. You can examine the following results for a standard study: • • result windows for all quantities on the Result Window Definition dialog box that are valid for each analysis in the study measure values listed in the summary file for each analysis You need to define a separate standard study in the following cases: • • if you want to include multiple analyses if you want to set design parameters When you define a standard study, you can set parameters for the selected analyses for a modified version of your model. 752 Structural and Thermal Simulation Set Parameters Select this item if you want Mechanica to calculate results for a modified version of your model. You define this modified version by setting one or more parameters to different values. When you select Set Parameters, a list of the parameters you created appears in a scroll box. Select one or more parameters from the list. The computation time for the study is not affected by the number of parameters you select. For each parameter you select, enter a value from 0 to 100 in the Settings column. This value is a percentage of the range for the design parameter associated with a given parameter. Mechanica uses this value to determine the position of the design parameter. You can enter one of the following symbolic values instead of a numerical value: • • min or minimum max or maximum These symbolic values represent the parameter's minimum or maximum value. You can use lowercase or uppercase letters. Minimum is always 0 and maximum is always 100. To Create a Standard Design Study This procedure assumes that you are in the Design Study Definition dialog box and that you selected Standard as the study type. 1. Enter a description (optional). 2. Select one or more analyses from the list. 3. If you want to change your model to a specific shape other than its current shape, select Set Parameters. 4. Click Accept. You return to the dialog box and the design study appears in the list. 753 Structural and Thermal Simulation - Help Topic Collection Global Sensitivity Study for Structure and Thermal Global Sensitivity Study In a global sensitivity study, Mechanica calculates values for all measures that are valid for the analyses included in the study. The software specifically calculates the changes in your model's measures when you vary a design parameter over a specified range. Mechanica does this by calculating measure values at regular intervals in a design parameter's range. You can vary more than one parameter simultaneously. You can also examine the results for a global sensitivity study as a graph of a measure for a selected design parameter. Note: Mechanica does not calculate dynamic step measures when you use dynamic time, frequency, or random response analyses in a global sensitivity study. The Design Study Definition dialog box contains the following items: • Analyses — Select one or more analyses from this list. Mechanica calculates results separately for each analysis. You also view results separately for each analysis. Parameters, Start, End — Select one or more parameters from the alphabetical list of parameters you created for the model. Number of Intervals — Enter the number of intervals in the range of each parameter you want Mechanica to use in the study. Mechanica distributes these intervals equally across each parameter's range and calculates values for your model's measures at each interval. Increasing the number of intervals increases the computation time for the design study. You can enter from 1 to 999 intervals. The default is 10. • Repeat P-Loop Convergence — Select this item to direct Mechanica to carry out additional calculations during the study. • • Parameters, Start, End Use the Parameters area of the dialog box to specify a range across which you want Mechanica to vary each selected parameter during a global sensitivity study. You can select one or more parameters from the alphabetical list of parameters you created for the model. Selecting additional parameters has an insignificant effect on computation time for the study. 754 Structural and Thermal Simulation If you select multiple parameters, Mechanica varies the parameters in sync, calculating a single set of values for your model's measures at each interval. To get results for individual parameters, you should create a separate study for each parameter. Each value you specify is a percentage of the range for the design parameter associated with a given parameter. The End value must be greater than the Start value. You can enter one of the following symbolic values instead of a numerical value: • • min or minimum (always 0) max or maximum (always 100) Repeat P-Loop Convergence Use this option if you want to change the shape of your model considerably in the sensitivity or optimization study. At the first interval of a global sensitivity study using multi-pass adaptive convergence, Mechanica analyzes each element edge by repeating its calculations at successively higher polynomial orders until reaching either convergence or the maximum polynomial order of nine, whichever comes first. Mechanica calculates values at the remaining intervals differently depending on whether or not you select this option: • If Repeat P-Loop Convergence is off, Mechanica calculates values at each remaining interval at the polynomial order it used to reach convergence for the first interval. This method cuts down on calculation time but may not fully capture your model's changes. If Repeat P-Loop Convergence is on, Mechanica starts its calculations over again at each interval until reaching convergence or the maximum polynomial order. This is important if you want to significantly change your model's shape, since the polynomial order required to reach convergence at later intervals may change. Note: For optimization studies, the default is On. • Regeneration Analysis A regeneration analysis is a predefined analysis that regenerates your Pro/ENGINEER model. Because regeneration analysis does not import geometry or generate elements for the part, it is a quick method of running a design study without having to first set up an analysis. You can select regeneration analysis for the following design study types: • • Local Sensitivity Global Sensitivity 755 Structural and Thermal Simulation - Help Topic Collection • Optimization When you select regenerate (Model Regeneration Only) from the list of analyses, Mechanica runs a regeneration analysis and generates a summary and log report. For local and global sensitivity studies, you can run a regeneration analysis from the design study dialog box. The regenerate option appears automatically in the list of existing analyses for the model. For optimization studies, Mechanica runs a regeneration analysis automatically if any of the following are true: • • • The goal and all selected limits are Pro/ENGINEER parameter-driven measures. The goal is a Pro/ENGINEER parameter-driven measure and no limits are defined. The selected limits are all Pro/ENGINEER parameter-driven measures and no goal is defined. If a study is a candidate for regeneration analysis, you can choose either of two modes in which to run the analysis: • • Current session of Pro/ENGINEER — Enables a faster analysis which runs in the session you were working in. Separate session of Pro/ENGINEER — Enables you to continue working in the same session of Pro/ENGINEER while the study runs in a different session. To Create a Global Sensitivity Study This procedure assumes that you are in the Design Study Definition dialog box and that you selected Global Sensitivity as the study type. 1. Enter a description for the study (optional). 2. Select one or more analyses from the list. If you do not want to run a design study based on an existing analysis, you can select a predefined analysis that regenerates the Pro/ENGINEER model. 3. Select one or more parameters. 4. If you want Mechanica to use a number of intervals different from the default value of 10, select the number of intervals. 5. If you will be changing the shape of your model considerably in the sensitivity study, select Repeat P-loop Convergence. 6. Click Accept. You return to the dialog box and the design study appears in the list. 756 Structural and Thermal Simulation Local Sensitivity Study for Structure and Thermal Local Sensitivity Study A local sensitivity study calculates the effect of slight changes in one or more parameters on your model's measures. Mechanica calculates the slope of the sensitivity curve between two sample points. The result is a graph of the linear approximation of a measure over a parameter's range. The sensitivity slopes are also reported in the run Summary file. Mechanica computes local sensitivity by performing one base analysis and then a perturbation analysis for each parameter. A base analysis is the same as a standard analysis. In a perturbation analysis, Mechanica changes the parameter by an incremental amount and then performs a new analysis. Mechanica uses the results of the perturbation analysis and base analysis to compute a slope. This value is the same as the slope of the global sensitivity curve at a given value of the parameter. By comparing the rates of change caused by several parameters, you can determine which parameters affect the model the most. The larger the rate of change, the greater the effect. If you are using local sensitivity studies to facilitate future optimization runs, consider the strategies listed in Optimizing a Model when reviewing your sensitivity results. You can use a local sensitivity study to determine the most important design parameters for your model, which provides a way of reducing the number of parameters used in global and optimization studies. This, in turn, reduces run times and resource requirements. Mechanica calculates values for all measures that are valid for the analyses included in the study. But Mechanica does not calculate the value for measures using the At Each Step option when you use dynamic time, frequency, or random response analyses in a local sensitivity study. For dialog box parameters, refer to Local Sensitivity Dialog Box. Parameters, Settings Use these items to select and enter a value for one or more parameters you created for the model. Selecting additional parameters has an insignificant effect on computation time for the study. Next, enter a value in the Settings column to determine each parameter's position at the start of the local sensitivity study. 757 Structural and Thermal Simulation - Help Topic Collection If you select multiple parameters, Mechanica updates the model to reflect the settings for all parameters you selected. Mechanica then varies each parameter independently about the Settings value and calculates a single set of values for your model's measures for each parameter. This value is a percentage of the range for the design parameter associated with a given parameter. You can enter one of the following symbolic values instead of a numerical value: • • min or minimum (always 0) max or maximum (always 100) Regeneration Analysis A regeneration analysis is a predefined analysis that regenerates your Pro/ENGINEER model. Because regeneration analysis does not import geometry or generate elements for the part, it is a quick method of running a design study without having to first set up an analysis. You can select regeneration analysis for the following design study types: • • • Local Sensitivity Global Sensitivity Optimization When you select regenerate (Model Regeneration Only) from the list of analyses, Mechanica runs a regeneration analysis and generates a summary and log report. For local and global sensitivity studies, you can run a regeneration analysis from the design study dialog box. The regenerate option appears automatically in the list of existing analyses for the model. For optimization studies, Mechanica runs a regeneration analysis automatically if any of the following are true: • • • The goal and all selected limits are Pro/ENGINEER parameter-driven measures. The goal is a Pro/ENGINEER parameter-driven measure and no limits are defined. The selected limits are all Pro/ENGINEER parameter-driven measures and no goal is defined. If a study is a candidate for regeneration analysis, you can choose either of two modes in which to run the analysis: • Current session of Pro/ENGINEER — Enables a faster analysis which runs in the session you were working in. 758 Structural and Thermal Simulation • Separate session of Pro/ENGINEER — Enables you to continue working in the same session of Pro/ENGINEER while the study runs in a different session. To Create a Local Sensitivity Study This procedure assumes that you are in the Design Study Definition dialog box and that you selected Local Sensitivity as the study type. 1. Enter a description for the study (optional). 2. Select one or more analyses from the list. If you do not want to run a design study based on an existing analysis, you can select a predefined analysis that regenerates the Pro/ENGINEER model. 3. Select one or more parameters. 4. Click Accept. You return to the dialog box and the design study appears in the list. Optimization Study for Structure and Thermal Optimization Study An optimization study adjusts one or more parameters to best achieve a specified goal or to test feasibility of a design, while respecting specified limits. Mechanica adjusts the model's parameters in a series of iterations through which it tries to move closer to the goal while satisfying any limits. If you have no goal, Mechanica simply tries to satisfy your limits. An optimization study with no goal is sometimes called a feasibility study. The goal and limits are each optional, but you must have at least one goal or one limit. Before defining an optimization design study, see Preview Design Parameters. Mechanica calculates values for all measures that are valid for the analyses included in the study. Be aware of the following: • • Mechanica does not calculate the value for measures using the At Each Step option when you use dynamic time, frequency, or random response analyses in an optimization study. You cannot select the At Each Step option for measures for the optimization goal or limits. Mechanica runs a regeneration analysis automatically if the study meets certain criteria regarding goals, limits, and parameters. You can examine the following types of results for an optimization study: • graphs of a measure against the study's iterations 759 Structural and Thermal Simulation - Help Topic Collection • standard results for the final optimized model This dialog box contains the following items: • • • • • • • Goal Limits on Measures Track Parameters, Min, Init, Max Optim Convergence (%) Max Iterations Repeat P-Loop Convergence Preview Design Parameters Before defining an optimization design study, you should use the following functions to preview what effect your design parameters will have on the model: • Use the Mechanica Design Controls>Shape Review command to review your model at specific settings for each parameter. Shape Review enables you to identify conflicts within multi-dimension relations defined as a design parameter. Use the Mechanica Design Controls>Shape Animate command to vary your parameters across different ranges and in different combinations to find problems that might arise during the optimization process. • Goal Use this area of the Design Study Definition dialog box to select a measure to minimize or maximize as the goal of the optimization. For example, you might want to minimize mass or reaction forces for your model. When defining a goal, you cannot select a measure unless you have defined an analysis for which that measure is valid. However, you can select a measure associated with different analyses. Defining a goal is optional, but if you do not define a goal, you must define limits. Without a goal, Mechanica searches for the first feasible design that satisfies the limits you define. If you do not want to define a goal, deselect Goal on the Design Study Definition dialog box. The Goal area of the dialog box includes a Goal option menu that you use to indicate the goal and a Select button that enables you to select the measure you want to use as the basis for the goal. The Goal option menu provides these selections: • • Minimize — Mechanica tries to make the goal measure as small as possible. If the measure can move into the negative numbers, Mechanica will try to make the goal as negative as possible. Maximize — Mechanica tries to make the goal measure as positive as possible. 760 Structural and Thermal Simulation • • Minimize Abs Val — Mechanica tries to minimize the absolute value of the goal measure, getting it as close to zero as possible, regardless of sign. Maximize Abs Val — Mechanica tries to maximize the absolute value of the goal measure, getting it as far from zero as possible, regardless of sign. Note that the Minimize and Maximize options take into account the sign of the goal measure's value, while the two Absolute Value options do not. Clicking the Select button displays the Measures dialog box. You use the option menu in the upper right corner of this dialog box to choose the type of measure you want to select—Structural or Thermal. You cannot select a measure unless you have defined an analysis for which that measure is valid. You can select measures associated with multiple analyses. Once you select a measure and exit the Measures dialog box, Mechanica displays the name of the measure you select on the Design Study Definition dialog box. Mechanica also displays an analysis name, except for measures like total_cost and total_mass that are calculated for all analyses. If there is more than one analysis you can use the Select button beside the analysis name to indicate the analysis you want the optimization study to run. Depending on the analysis type you select, you may have the option of selecting specific load sets or modes. If you select a modal and prestress modal analysis, you also have the option of enabling mode tracking. Limits on Measures Use this area of the Design Study Definition dialog box to select one or more measures to act as limits for the optimization, and to define the mathematical limit you want Mechanica to observe for each measure. Each limit you define is a mathematical statement including the measure, an operator, and a value (for example, max_stress_prin < 100). Mechanica seeks to keep the measures you select within the limits you specify during the study. For example, you might want to ensure that an aluminum model does not exceed 20,000 psi for a von Mises stress measure. If you set this von Mises stress value as an optimization limit (max_stress_vm < 20000), Mechanica will move the model toward 20,000 psi in an attempt to find a more efficient model that still meets that limit, as well as any goal you set. Defining limits is optional, but if you do not define limits, you must define a goal. Without limits, Mechanica searches for the optimum value of your goal anywhere in the full range of the parameters you select. When defining a limit, you cannot select a measure unless you have defined an analysis for which that measure is valid. However, you can select a measure associated with different analyses. The Limits on Measures area of the dialog box includes a Create and Delete button that you use to create and delete the measure limits. Clicking the Create button displays the Measures dialog box. You use the option menu in the upper right corner of this dialog box to choose the type of measure you want to select— Structural or Thermal. You cannot select a measure unless you have defined an 761 Structural and Thermal Simulation - Help Topic Collection analysis for which that measure is valid. You can select measures associated with multiple analyses. Once you select a measure and exit the Measures dialog box, Mechanica displays the name of the measure you select on the Design Study Definition dialog box and adds fields that enable you to select an operator (<, >, or =) and value for the measure limit. When entering values, use units consistent with the units you have used previously with this model. Mechanica reports some rotation measures in radians. You must enter the limits of rotation measures in radians (1 radian = 57.29578 ). Note: You can use the same measure as a limit more than once. After you select a measure as a limit, Mechanica displays an analysis name below the limit definition area, except for measures like total_cost and total_mass that are calculated for all analyses. If there is more than one analysis you can use the Select button beside the analysis name to indicate the analysis you want the optimization study to run. Depending on the analysis type you select, you may have the option of selecting specific load sets or modes. If you select a modal and prestress modal analysis, you also have the option of enabling mode tracking. Parameters, Min, Init, Max Select one or more parameters from the alphabetical list in the scroll box of the parameters you created for the model. A parameter is associated with one design parameter. Mechanica varies the parameters associated with the parameters you select to reach the goal and meet the limits of the optimization study. The computation time increases substantially for each additional parameter you select. After you select parameters, entry boxes appear next to each parameter. Enter the minimum, initial, and maximum values for each selected parameter. The minimum and maximum values define a range across which you want Mechanica to vary each selected parameter during the study. The initial value defines the position of the design parameter at the start of the optimization study. Enter a value from 0 to 100, representing a percentage of the range for the design parameter associated with a given parameter. You can enter one of the following symbolic values instead of a numerical value: • • min or minimum (always 0) max or maximum (always 100) 762 Structural and Thermal Simulation Optim Convergence (%) Use Optim Convergence (%) to specify the percentage you want Mechanica to use to determine when an optimization has converged. In an optimization study, the Mechanica optimizer adjusts the model in a series of steps until it reaches convergence in one of these ways: • • • the change in the goal quantity from the previous optimization step relative to its initial value is within the convergence value the change in the goal quantity relative to the parameters is within the convergence value (the slope of a graph of the goal vs. the parameters is close to 0) the goal cannot be improved from the current design point without violating one or more of your specified limits Mechanica also uses the convergence value to determine if a limit is met. For example, if the convergence is 1%, Mechanica keeps to the limit value give or take 1%. If a limit value is near zero, the optimizer uses one-tenth of the specified convergence value as an absolute limit. For example, if you use the default convergence value of 1, a zero limit is considered met if its measure has a value of 0.001 (one-tenth of 1 percent) or less. Mechanica continues the optimization study until it reaches either the convergence value or the Max Iterations value you enter below. You can enter any number between 0 and 100 for convergence, but if you enter a number below 0.1 or above 25, Mechanica asks you to confirm the value you entered when you click Accept. Max Iterations Use Max Iterations to specify the maximum number of iterations you want Mechanica to carry out during the optimization study. The minimum number of iterations is 1. If you enter a number above 50, Mechanica asks you to confirm the value you entered when you click Accept. The higher the number of iterations, the longer it takes for Mechanica to reach the goal. Mechanica continues the optimization study until it reaches either the Max Iterations value or the value for Optim Convergence %. 763 Structural and Thermal Simulation - Help Topic Collection Regeneration Analysis A regeneration analysis is a predefined analysis that regenerates your Pro/ENGINEER model. Because regeneration analysis does not import geometry or generate elements for the part, it is a quick method of running a design study without having to first set up an analysis. You can select regeneration analysis for the following design study types: • • • Local Sensitivity Global Sensitivity Optimization When you select regenerate (Model Regeneration Only) from the list of analyses, Mechanica runs a regeneration analysis and generates a summary and log report. For local and global sensitivity studies, you can run a regeneration analysis from the design study dialog box. The regenerate option appears automatically in the list of existing analyses for the model. For optimization studies, Mechanica runs a regeneration analysis automatically if any of the following are true: • • • The goal and all selected limits are Pro/ENGINEER parameter-driven measures. The goal is a Pro/ENGINEER parameter-driven measure and no limits are defined. The selected limits are all Pro/ENGINEER parameter-driven measures and no goal is defined. If a study is a candidate for regeneration analysis, you can choose either of two modes in which to run the analysis: • • Current session of Pro/ENGINEER — Enables a faster analysis which runs in the session you were working in. Separate session of Pro/ENGINEER — Enables you to continue working in the same session of Pro/ENGINEER while the study runs in a different session. To Create an Optimization Study This procedure assumes that you are in the Design Study Definition dialog box and that you selected Optimization as the study type. 1. Enter a description for the optimization (optional). 2. Select a measure as the goal for the optimization. (Selecting a goal is optional, but if you do not select a goal, you must define limits.) 3. Select limits for one or more measures that Mechanica cannot violate during the optimization. (Defining limits is optional, but if you do not define limits, you must define a goal.) 764 Structural and Thermal Simulation 4. Select parameters from those listed, and define the range across which you want Mechanica to vary each selected parameter during the optimization. 5. Enter the percentage you want Mechanica to use to determine when the optimization has converged. 6. Enter the maximum number of iterations you want Mechanica to carry out during the optimization. 7. Select Repeat P-Loop Convergence if you expect the shape of your model to change considerably during the optimization. (It is selected by default.) 8. Click Accept. You return to the dialog box and the design study appears in the list. To Save an Optimized Shape 1. Select Analysis>Mechanica Design Controls>Optimize Hist. 2. Select one of the following commands: o o o Enter Study — Enables you to enter the optimization study name in the Pro/ENGINEER message window. Search Study — Enables you to select a study name from a list of defined optimization studies. Quit — Closes the OPTIMIZE HIST menu and returns you to the DSGN CONTROLS menu. 3. Select or enter a design study. Mechanica displays your optimized model, and lets you sequentially display the shape it used for each step in the optimization study. 4. Press ENTER to accept the final optimized shape. 5. Select File>Save to save the optimized model in Pro/ENGINEER. 6. Press ENTER to save the optimized model. To Create a Design Study 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select the File>New Design Study menu option. The Design Study Definition dialog box appears. 3. Enter a name at the top of the Design Study Definition dialog box. The name you enter must be different from the analysis name. . 765 Structural and Thermal Simulation - Help Topic Collection 4. Select the type of design study you want to run. For procedures defining each type of study, select one of the following: o o o o Standard Global Sensitivity Local Sensitivity Optimization 5. When you return to the dialog box, close it or continue working. To Define an Optimization Study Limit This procedure assumes that you are in the Design Study Definition dialog box and that you selected Optimization as the study type. 1. Select the Limits on Measures check box. Mechanica adds limit definition fields to the Limits on Measures area of the dialog box. 2. Click the Create button. Mechanica displays the Measures dialog box. 3. Select the measure you want to minimize or maximize and click OK. Mechanica returns you to the Design Study Definition dialog box. 4. Select a mathematical operator (<, >, or =) and enter a value for the selected measure in the same row as the measure name. Tip: You can enter a numerical value or c for the current value. 5. If you defined more than one analysis of the relevant type, use the Select button to select the analysis you want. 6. If you included more than one load set for a static, prestress static, or steadystate thermal analysis, use the Select button to select a different load set. 7. If you selected a modal and prestress modal analysis, select a mode number. 8. If you want Mechanica to track a specific mode shape, select Track. Repeat steps 2 through 9, and any subsequent steps that apply, for each measure you selected as a limit. To Define an Optimization Study Goal This procedure assumes that you are in the Design Study Definition dialog box and that you selected Optimization as the study type. 1. Select the Goal check box. Mechanica adds goal definition fields to the Goal area of the dialog box. 2. Select one of the following items from the Goal option menu: o Minimize o Maximize o Minimize Abs Val o Maximize Abs Val 3. Click the Select button to the right of the goal. Mechanica displays the Measures dialog box. 4. Select the measure you want to minimize or maximize and click Accept. 766 Structural and Thermal Simulation Mechanica returns you to the Design Study Definition dialog box and displays the analyses that include the measure. 5. If you defined more than one analysis of the relevant type, use the Select button to select the analysis you want. 6. If you included more than one load set for a static, prestress static, or steadystate thermal analysis, use the Select button to select a different load set. 7. If you selected a modal and prestress modal analysis, select a mode number. 8. If you want Mechanica to track a specific mode shape, select Track. To Run a Regeneration Analysis This procedure assumes that when you created your design study, you selected a local sensitivity or global sensitivity and that you selected regenerate (Model Regeneration Only) from the list of analyses on the Design Study Definition dialog box. 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select Start from the Run menu. Mechanica may display one or more prompts before starting the run. 3. Select one of the following options from the Run Mode Choice dialog box: o Run in Current Session of Pro/ENGINEER — Enables you to observe the effects of the parameter changes and reduces the analysis run time. While the study is running, you cannot work in this session of Pro/ENGINEER. o Run in Separate Session of Pro/ENGINEER — Enables you to continue working in the current session of Pro/ENGINEER while Mechanica runs the design study. You will not be able to observe parameter changes until either the study is complete or you interrupt it. 4. Select Run to start the analysis. 5. When the study is complete, you can choose to keep the new values or return to the original values. You can check to see if the regeneration analysis is complete by looking for a directory named regenerate in the directory from which you launched Mechanica. . 767 Structural and Thermal Simulation - Help Topic Collection Local Sensitivity Dialog Box This dialog box contains the following items: • Analyses — Click this button to select one or more analyses from this list. Mechanica calculates results separately for each analysis. You also view results separately for each analysis. Parameters, Settings — Select one or more parameters from the alphabetical list of parameters you created for the model. • Strategy: Viewing Optimization Results After the optimization is completed, examine the results by performing the following: • • Examine the changes in measures of interest from step to step by defining a graph using Optimization Pass as the location. For static and modal analyses, review deformed shape and stress results for the optimized design. For thermal analyses, review temperature and flux results for the optimized design. Compare them with the standard design study results. Strategy: Running a Global Sensitivity Study Use the following strategies for defining a global sensitivity study and reviewing the study results: • Each step of a global sensitivity study can take almost as much time as a standard run of the same model. Take this into account when you specify the number of intervals. A greater number of intervals will require longer run time. The key result you obtain from a global sensitivity study is a sensitivity graph that indicates which values of the design parameters correspond to less mass, higher stress, higher frequency, or lower flux, and so forth. This information serves as a guide to help you improve the design. By looking at sensitivity graphs for measures you plan to use for the optimization goal and limits, you can determine which parameters are likely to have the most effect on those measures. You can also determine the portion of a parameter's range that has the most effect on the measures. • • As an option, you can specify that convergence be repeated. We recommend repeating convergence if the parameters cause massive distortion of the elements. However, the run will require more time. Sometimes, by adjusting the starting and ending positions of the parameters, you can define the study such that the first step includes the most distorted elements. If the p-levels of the edges used for the worst case result in convergence, they will work for all others. 768 Structural and Thermal Simulation Varying a Single Design Parameter in a Global Sensitivity Study In the following example, the global sensitivity curve plots von Mises stress as a function of change in radius. In this case, the von Mises stress is at a maximum value of approximately 10.69 ksi for a radius of 0.45 inch. Using Global Sensitivity Studies Effectively Global sensitivity gives you a cross section of the design space—the values of measures as Mechanica varies one or more design parameters through their range of values. If the global sensitivity study were not available, you could obtain the same results by making several copies of a model and slightly modifying each one. After running a standard study on each, you could then plot the measure of interest from each run on a single graph. The global sensitivity study provides that data with one run. 769 Structural and Thermal Simulation - Help Topic Collection In the most common type of global sensitivity study, you instruct Mechanica to vary a single design parameter while keeping all other design parameters constant. You can also do a study in which Mechanica varies multiple design parameters simultaneously over specified ranges. Another option is to offset one or more design parameters while varying another. To do this, set start and end values that are very close together for the design parameters you want to offset. You cannot set identical start and end values for any two parameters. For an example of a global sensitivity curve plotting von Mises stress as a function of change in radius, see Varying a Single Design Parameter in a Global Sensitivity Study. Track In Structure only, this item appears if you select modal_frequency as the measure for the goal or a limit. Select this item to direct Mechanica to follow a particular mode through the optimization, even if that mode's frequency becomes greater or less than a neighboring mode's frequency. As Mechanica modifies a design parameter during optimization, frequencies of different modes can change, so that mode 2 at the beginning can become mode 3 at the end. For example, if you enter 2 for the Mode Number and select Track, Mechanica tracks at each step of the optimization the frequency of the mode whose shape is closest to the shape of mode 2 in the original model. Mechanica reports the mode number of the frequency in a summary file, which you can access with the Info>Status command on the Analyses and Design Studies dialog box. If you do not select Track, Mechanica optimizes whatever mode has the second lowest frequency, even if the mode shape changes. Keep the following points in mind if you select Track: • Mode tracking requires the polynomial order on each edge to remain constant during the optimization. Mechanica calculates values for the analysis connected to the modal_frequency measure at the first interval of the optimization. Mechanica then uses the polynomial order it reached to achieve convergence in the first interval at each remaining interval. Do not select Track for a rigid mode. If your analysis contains rigid modes, Mechanica ignores them when tracking a non-rigid mode. For buckling analyses, Track is not available. Since the smallest positive buckling mode is the mode that will cause failure first, Mechanica automatically tracks the lowest positive mode. • • 770 Structural and Thermal Simulation Redefine the Design Study If you delete a component of a design study, you need to redefine the study before you run it: • If you delete an analysis or parameter you selected when you defined a design study, you need to edit the study to select a new analysis or parameter. Even if you create a new analysis or parameter with the same name as the one you deleted, you must still edit the design study and reselect that analysis or parameter name. If you delete a constraint set or load set after you include it in an analysis, you may invalidate the analysis. If the analysis is part of a design study, you must edit the analysis to select a new set before running the design study. Even if you create a new set with the same name as the set you deleted, you must edit the analysis and reselect the set name. • Strategy: Optimizing a Model When you are satisfied with the results of the standard design study and have gained a feel for the design space by running one or more sensitivity studies, you can use optimization to find the optimal values of your parameters to achieve a specific design goal (for example, to minimize mass). See the suggested approaches when you want to do any of the following: • • • • Before defining an optimization study, consider which sensitivity studies to run. Define and run an optimization study. After the optimization has completed, analyze the results. After you run an optimization study, follow up with standard and local sensitivity studies. Strategy: Defining Optimization Studies When you define and run an optimization study, consider the following: • You can monitor the progress of the optimization study by selecting the Info>Status command on the Analyses and Design Studies dialog box. The summary file gives you a running account of the optimization process, with comments and warnings as the Structure engine searches the design space. 771 Structural and Thermal Simulation - Help Topic Collection Strategy: After You Run an Optimization Study You can follow up optimization studies with standard and local sensitivity studies in the following ways: • If you ran an optimization study with a high analysis convergence percentage to save time, the values for the parameters are probably valid even though the goal and limit values may not be accurate. You can then lower the convergence value in the analysis you included in that study and run a standard study with your parameters set to their optimization values. This study will give you more accurate results for the goal and other quantities. You can also run a new optimization study after lowering the convergence values. Use the final position of your parameters in the old study as their initial position in the new study. The new optimization will produce more accurate results and could further refine the optimized shape of your model. • If any design parameters in an optimization need to meet a standard size or other manufacturing requirement, you can set those design parameters to the standard size closest to the optimized value and run a standard study. You can use Mechanica Design Controls>Shape Review to determine the percentage values for each parameter that correspond to the closest manufacturing requirement. You can then check the results of the standard study to see if other quantities of interest are still close to their optimized value. • If an optimization study ends with a message in the report file that says changes in the goal quantity were insignificant relative to its initial value, you can use local sensitivity to check the goal quantity. Set the start position of each parameter to the optimized position. After the sensitivity study completes, graph the goal quantity against each parameter, and check to see whether the slope of each graph is close to zero. A slope that is not near zero indicates that the optimization study may not have reached the optimum goal value. In this case, you may want to redefine the optimization study and run it again. If you run the optimization again, use the parameter values from the final optimum model of the last optimization study as the starting point in the new study. • If an optimization study ends with insignificant changes to your parameters, Mechanica may have encountered a local optimum value for your goal measure that caused it not to explore the design space more fully. 772 Structural and Thermal Simulation If this happens, run the study again after setting the parameters to initial values far enough from the original settings to encourage Mechanica to examine more promising parameter positions. Selecting Load Sets and Modes for Optimization Studies Depending on the analysis type you select for an optimization study goal or limit, you may have the option of selecting specific load sets or modes: • For static, prestress static, or steady-state thermal analyses, the dialog box displays the name of the first load set you included in the analysis. If you included more than one load set, you can use the Select button to select a different load set. For modal and prestress modal analyses, select a mode number. The dialog box displays Mode 1. If you specified more than one mode in the analysis, you can use the Select button to select a different mode number. Mechanica reports the frequency for each mode by number in the summary file after you run a standard design study. You can use the summary from a previously run standard study to choose a mode number to enter in this dialog box. Use the Info>Status command on the Analyses and Design Studies dialog box to access the summary file. • Using Measures More than Once for Optimization Limits For optimization study limits, you can use the same measure more than once. For measures that use the same combination of analyses and load set or mode numbers, you must adhere to these restrictions: • • • • • • Enter different values for each limit. Do not use c (current) for either value. Use different mathematical operators for each limit. Do not use = as the operator for either limit. For modal analyses, do not use All for the mode for either limit. For modal analyses, use the same selection for Track for both limits. If you set limits within the same analysis that conflict with each other, Mechanica attempts to satisfy only one of the conflicting limits. For example, if you assigned contradictory values to two related measures such as max_stress_xx < 1 and max_stress_prin > 2, Mechanica interprets the limit as meaning it should either keep max_stress_xx less than 1 or keep max_stress_prin greater than 2. 773 Structural and Thermal Simulation - Help Topic Collection Strategy: Preparing for Optimization Studies When considering which sensitivity studies as preparation for your optimization study, be aware of the following: • Optimization typically requires more iterations as the number of parameters increases. You should therefore use as few parameters as possible. Sensitivity studies are helpful in deciding which design parameters are important. In particular, local sensitivity studies help identify parameters that do not affect the design significantly. The smaller the design space being considered, the shorter the optimization run time. You should therefore use the results from the global sensitivity study to narrow the range of each parameter being considered and thus limit the overall design space. The optimization takes less time the closer the baseline model is to the optimum. You might find it useful to review results from sensitivity studies to improve the candidate design prior to optimization. • • Running Solvers Native Mode Solvers Running Analyses and Design Studies Use the Analyses and Design Studies dialog box to run the analyses and design studies you create. The dialog box displays a list of existing analyses and design studies. To run an analysis or design study, select it from the list, and then use the following options to set up and manage the run: • Run menu o Start — Start running the analysis or design study you select. o Stop — Stop running the analysis or design study you select. o Restart — Restart a previously stopped analysis or design study. o Batch — Create the engine input files necessary to run one or more analyses or design studies. o Settings — Open the Run Settings dialog box, which enables you to change certain settings Mechanica uses for the run. Info menu o Status — Open the Run Status window, which enables you to view the status of a run. You can select the Detailed Summary check box at the bottom of the window to view a detailed summary of the run. o Diagnose — Open the Run Diagnostics dialog box, which enables you to review the warning and error messages. o Check Model — Perform model error checks to determine whether there are problems that would prevent an analysis or study run from starting such as missing properties, problems with constraints or boundary conditions, invalid analysis definitions, and so forth. • 774 Structural and Thermal Simulation For information on troubleshooting problems with a run, see Troubleshoot Run Problems. For information about reviewing the results of a run, see About Results. Before You Run an Analysis or Design Study Be aware of the following before starting your run: • You may want to check your Mechanica settings to determine how the software processes your model during analyses and design studies. You can use Mechanica settings to determine the following: o whether Mechanica includes datum curves or surfaces in the mesh o the defining ranges that Mechanica observes when creating elements o whether Mechanica treats the model as a shell or solid You can check your model for errors before you start a run by selecting Info>Check Model on the Analyses and Design Studies dialog box. If you select an invalid design study to run, Mechanica displays an error message after you select Start or Batch. Examples of invalid design studies include: o a design study containing an analysis that requires measures for convergence but has no measures selected o a sensitivity or optimization design study with no parameters Mechanica deletes a standard or sensitivity design study if you delete the only analysis belonging to that study. You should run only one design study at a time to avoid using too much memory. • • • • Before Mechanica Starts a Run Mechanica performs a number of steps before an actual run begins: 1. Performs preliminary error checking to make sure that all analyses, design studies, and model data are valid. 2. Converts surface pairs to midsurfaces if you defined surface pairs for shell modeling and you selected the AutorGEM>Midsuface or AutoGEM>Solid/Midsurface command. See Defining Solid and Shell Models for more information. 3. Merges the geometry, material properties, loads, constraints, design parameter data, analysis definitions, and design study definitions into the .mdb file. Mechanica stores this file, along with the .prt file, in the study directory. See Database Considerations for more information. 4. Checks the geometry and associated entities for errors. If there are any errors, Mechanica writes an error message to the summary file. 5. Creates elements using AutoGEM. Elements are the entities that Mechanica uses to analyze your model. They are the mathematical approximation of your model's geometry that Mechanica uses to simulate the behavior of your design. The elements created by AutoGEM comply with all element creation rules. As elements are created, Mechanica saves the element data. 775 Structural and Thermal Simulation - Help Topic Collection If geometry errors exist in your model, AutoGEM creates elements with approximated linear elements and places them in a new layer. If there are no modeling or meshing errors, Mechanica starts running the analysis. Analyses and Design Studies Dialog Box When you select the Analysis>Mechanica Analyses/Studies command, the Analyses and Design Studies dialog box appears. Use this dialog box to manage and run your analyses and design studies. The Analyses and Design Studies dialog box includes the following: • Menu bar — Perform the following activities using the options on the menu bar: o Create new analyses and design studies using the options available on the File menu. o Modify existing analyses and design studies using the Edit>Analysis/Study menu option. You can also copy or delete analyses or design studies using the options on the Edit menu. o Set up a run using the Run>Settings menu option or selecting the Configure Run Settings button on the toolbar to display the Run Settings dialog box. o Create a batch file to run more than one analysis or design study at a time using the Run>Batch menu option. o Check your model before you start a run by using the Info>Check Model menu option. o Start, stop, or restart analyses and design studies using the options on the Run menu or the buttons on the toolbar. o Monitor the status and view a detailed summary of a run using the Info>Status menu option. o Review the error and warning messages generated during a run using the Info>Diagnose menu option. Toolbar — Use the toolbar buttons to perform many of the functions available on the menu bar. Analyses and Design Studies Table — Lists the name and type of analyses and design studies for the current model. To perform an action on a specific analysis or design study, highlight it in the list and select the action from the options on the menus or use the toolbar buttons. Description — Displays a description, if available, of the analysis or design study you select from the list. • • • Closing the dialog box does not initiate any actions. To Start an Analysis or Design Study Run 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 776 . Structural and Thermal Simulation 2. Select an analysis or design study from the list. 3. Select Settings from the Run menu or click The Run Settings dialog box appears. 4. Make the appropriate changes to the Run Settings dialog box, and then click OK. 5. Select Start from the Run menu. Mechanica may display one or more prompts before starting the run. 6. Click Yes or No when Mechanica asks if you want error detection during the run. Mechanica starts the run. (Configure Run Settings). Setting Up a Run Select the Run>Settings menu option or the Configure Run Settings button on the Analyses and Design Studies dialog box to access the Run Settings dialog box. Use this dialog box to specify the locations of the output and temporary files, any elements you want to use from an existing study, the output file format, and the solver settings. The Run Settings dialog box includes the following options: • • • • • Directory for Output Files —Select the directory for the output files generated by the run. Directory for Temporary Files — Select the directory for the temporary files generated by the run. Elements — Select the source of the elements Mechanica uses during a run. Output File Format — Select an output format for the output file. Solver Settings — Use this area to specify settings for the solver: o Memory Allocation (MB) — Select the check box and enter the appropriate number of megabytes to allocate for the memory. o Use Iterative Solver — Select the check box to use the iterative solver and enter the maximum number of iterations and at which Ploop pass the iterative solver should take over from the direct solver. Defaults — Select this button to return the settings on the dialog box to the default values. • Directory for Temporary Files Specify the directory where you want Mechanica to place temporary files created during the run. Mechanica places temporary files in a directory called study.tmp (study is the name of the design study you are running), and places study.tmp in the directory for temporary files you specify here. 777 Structural and Thermal Simulation - Help Topic Collection The Run Settings dialog box initially displays the name of the directory you specify using the sim_run_tmp_dir config.pro option, or it displays the current working directory if you do not set the config.pro option. The directory you specify appears the next time you open the dialog box. As a general guideline, you should have at least 20 to 30 megabytes of disk space available for temporary files. Mechanica deletes these files when it completes the run. You can specify multiple directories for your temporary files using the -w option of the msengine command. Directory for Output Files Specify the directory where you want Mechanica to place the output files, which contain the results data from the run. Mechanica places all output files and the engine input files in a directory called study (study is the name of the design study you are running), and places study in the directory for output files you specify here. The Run Settings dialog box initially displays the name of the directory you specify using the sim_run_out_dir config.pro option, or it displays the current working directory if you do not set the config.pro option. The directory you specify appears the next time you open the dialog box. As a general guideline, you should have 9 to 15 megabytes of disk space available for the output files. Elements You can specify the elements you want Mechanica to use when you run an analysis or design study by selecting one of the following options on the Run Settings dialog box: • • • Use Elements from Existing Mesh File Create Elements during Run Use Elements from an Existing Study Click the Select button to display the Select Existing Study Directory dialog box that lists the studies in the current directory. When you return to the Run Settings dialog box, the directory path of the study you selected appears. 778 Structural and Thermal Simulation Output File Format Specify whether the Mechanica engine writes the engine output files in binary format or ASCII format. Binary format is the default. Memory Allocation Select Memory Allocation to turn on RAM allocation. This setting is turned off by default. The value you enter sets the amount of RAM reserved for solving equations and for storing element data created by the iterative solver. The engine dynamically allocates the rest of the memory it needs for the run. Before you run design studies, you can set the amount of RAM the engine uses. Depending on the amount of RAM installed in your machine, you might be able to improve the engine solver performance by changing this setting. When you select Memory Allocation, Mechanica displays the default value of 128 megabytes. You can change this default value by setting the config.pro value for sim_max_memory_uasge to a different number. The value you enter must be greater than 0.1. Some tips for setting this value include: • • You can use the default allocation for any run. If you have a lot of RAM on your machine, you may want to enter a higher RAM allocation number so that large models will run faster—you can slow the run substantially if you specify an allocation that is too large to fit in available RAM. You can also slow the run if you do not specify sufficient memory, especially if you specify less than the default. You can increase the speed of the iterative solver by increasing the amount of RAM you allocate with this option. • • For specific information about specifying solver RAM, see Guidelines for Allocating RAM for Solver and Element Data. Use Iterative Solver Select this item to run a study with the iterative solver instead of the direct block solver. The Structure engine uses the direct solver by default because it usually uses less time, disk space, and/or memory than the iterative solver. For more information about choosing a solver and when to use the iterative solver instead of the direct solver, see Select the Solver. You can use the iterative solver in the following situations: • • • if you ran out of disk space running a design study using the direct solver if a run is very time-consuming using the direct solver if you are running a linear static analysis and your model is a solid 779 Structural and Thermal Simulation - Help Topic Collection The iterative solver has the following limitations: • • • If you are running a global sensitivity or optimization design study, you must select Repeat Convergence when you create the study. If you are running a local sensitivity or optimization design study, none of the analyses in the study can have temperature loads in Structure that refer to thermal analyses. If your design study contains any modal analyses, Mechanica does not use the iterative solver for those analyses. For some models, the iterative solver may not converge. If a design study does not converge, the run terminates, and you must re-run the study without the iterative solver. When you select this item, the following additional items appear on the dialog box: • • Maximum Iterations After P-Loop Pass Start Select the Run>Start menu option or select the Start Run button on the Analyses and Design Studies dialog box to start the run of a selected analysis or design study. You can use one of the following methods to start an analysis or design study run: • • Run directly from within Mechanica by selecting the Run>Start menu option or the Start button on the Analyses and Design Studies dialog box. Run from your operating system command prompt. Create the input files for each study by selecting the Run>Batch menu option on the Analyses and Design Studies dialog box. You can then run each study in succession by using the mecbatch command. Mechanica gives you the following feedback before starting a run: • • • If you enter an invalid design study, you will see an error message. Mechanica asks if you want error detection during the run. If your study is a candidate for a regeneration analysis but no other analysis type, the Run Mode dialog box appears, enabling you to: o run the study within the current Pro/ENGINEER session. The study runs faster, but you cannot work in Pro/ENGINEER while the study proceeds. o run the study as a separate task while you continue working in the same Pro/ENGINEER session 780 Structural and Thermal Simulation Existing Design Study Files After you select Start, Mechanica asks you one or both of the following questions: • Do you want to delete any output files that are already present for a previously run study? Before deleting these files, make sure that you do not need the data they contain. If in doubt, you can specify a different directory for output files for the current run or copy the design study to a new name. You can specify the directory for the output files using the Run>Settings menu option. Do you want to delete any temporary files located in the study.tmp directory (study is the name of the design study you selected)? Mechanica automatically deletes temporary files when a run completes normally. If temporary files are still present, it means that a previous run of the same design study ended in error, was stopped before it completed, or is currently running. If the files are left over from a previous run, you can safely delete them. If the design study is currently running, you should wait until it is finished before starting a new run. • Invalid Design Studies If you select an invalid design study, Mechanica displays an error message after you select Start or Batch. Examples of invalid design studies include: • • a design study containing an analysis that requires measures for convergence but has no measures selected a sensitivity or optimization design study with no parameters Error Detection If you do not request error detection, Mechanica goes to the next step. If you skip error detection, and your model contains errors, the run could terminate later with a fatal engine error. If you request error detection, Mechanica checks the model for errors. Mechanica carries out the same checks as it does when you select Info>Check Model on the Analyses and Design Studies dialog box, with these additions: • • If you select a design study that contains analyses from both Structure and Thermal, Mechanica checks for both Structure-specific and Thermal-specific errors, and displays entities specific to both products during error detection. Mechanica checks for some additional errors that Check Model does not detect. 781 Structural and Thermal Simulation - Help Topic Collection • Once a run has started, Mechanica checks for errors in the following areas: o o o o matching parameters convergence measures optimization studies temperature distribution • After error checking is complete or interrupted, Mechanica searches for the following: o o boundary edges boundary faces Even if you previously used Check Model, you should check your model again to catch errors introduced since you used Check Model, and to take advantage of the extra checks performed at this time. Once Mechanica checks your model for errors, you can resolve them. Restart To restart an analysis or design study, select the Run>Restart menu option on the Analyses and Design Studies dialog box. You can restart a standard design study or one of the following analysis types: • • • • • • static prestress static modal prestress modal buckling steady-state thermal Note that Restart does not work for analyses that use the single-pass adaptive method. Before You Use Restart Before you restart an analysis or design study, you can make the following changes to it, on the analysis definition dialog box: • • • Raise the maximum polynomial order in the event that the analysis did not converge the first time. Change the plotting grid, making it larger for more refined results, or smaller to use less disk space or CPU time. This can have an effect on the convergence for analyses that converge on measures. Change the option to calculate stresses, rotations, or heat flux. This is useful, for example, if you forgot to ask for stress output the first time the analysis was run. 782 Structural and Thermal Simulation Before you restart, be aware of the following: • • • • • You can restart stopped analyses in any order. You cannot restart a sensitivity or optimization design study. You cannot restart an SPA analysis. Mechanica must complete at least one pass through the analysis in order for you to restart it. If the engine stops for any reason, including running out of disk space or swap space, power failure, maximum p-level reached (unless the analysis reached pass 9), or user interruption, you can use the Restart command to continue the analysis from the beginning of the pass during which the engine stopped. What Restart Does When you select Restart, Mechanica does the following: • runs the stopped analysis from the last completed p-pass, but does not continue to the other analyses in a design study Note: When running the analysis again, the engine overwrites most existing data for that analysis—if you do not want Mechanica to overwrite these results, you should make a copy of the study before you restart the analysis. • • • if the design study contains more than one analysis, displays the names of the analyses in the design study and prompts you to select the name of the analysis you want to restart saves all the information in the summary (.rpt), log (.stt), and measure convergence plotting (.res) files and appends new data to them gives you the opportunity to save the current restart run to a batch file so you can run it later Restart a Stopped Analysis or Design Study When you restart a run, Mechanica asks if you want to overwrite the results of the existing analysis or design study with the new results from the restarted run. If you made changes to your analysis before restarting it, Mechanica gives you the opportunity to change the polynomial order used in the run. At any time that Mechanica displays informational messages, you can select one of the following options: • • Click Cancel on any of the messages. Mechanica returns to the dialog box. Click Continue on all of the messages. Mechanica runs the analysis with the updated values. 783 Structural and Thermal Simulation - Help Topic Collection Batch Creating a Batch File Select the Run>Batch menu option on the Analyses and Design Studies dialog box to create a batch file. When Mechanica creates a batch file, it generates the engine input files necessary to run one or more design studies from your operating system. By default, Mechanica names the batch file mecbatch and places it in the directory from which you started Mechanica. If you change the name of the batch file or the directory, the new name or directory becomes the default for the next batch file you create. Use the Batch menu option to: • • • create a new batch file change the directory where the batch file is stored append selected studies to an existing batch file What Batch Does When you select Run>Batch, Mechanica does the following: • If output files for the design study already exist for the specified design study, Mechanica asks you if you want to delete them. Mechanica creates output files during a run. These files contain the results of the previous design study run, and may contain useful results even if they were created during a run that did not complete successfully. Before deleting the files, make sure that you do not need the data that they contain. If in doubt, you can specify a different directory for output files for the current run, or copy the design study to a new name. If you decide to save the existing files and not proceed with the run, Mechanica does not start the run and returns you to the Analyses and Design Studies dialog box. • • • If a batch file already exists, Mechanica asks if you want to append this design study to the existing batch file. If you do not append the design study to the existing batch file, Mechanica gives you the opportunity to overwrite the existing mecbatch file with a new one for the current design study. Mechanica asks if you want error detection. 784 Structural and Thermal Simulation If you do not check for errors, or if no errors were detected, Mechanica takes the following steps: o o writes the engine input files places the files in a directory called study, located in the directory for output files you specify on the Run Settings dialog box (study is the name of the design study you selected) adds an msengine command for the current study to the mecbatch file located in the directory from which you are running Mechanica o Run a Batched Analysis or Design Study To run the analyses or design studies you batched, open a command shell. Start the run by entering the mecbatch command. Mechanica runs each analysis or design study you batched in succession. If one analysis or study ends in an error, Mechanica continues running the remaining analyses or studies in the file. Stop To stop running a selected analysis or design study that you started during the current Mechanica session, select Run>Stop or the Stop Run button on the Analyses and Design Studies dialog box. Note: You cannot use Stop to cancel a run you started in a previous Mechanica session, or a run you started directly from the operating system by using the mecbatch or msengine commands. When you select Stop, Mechanica does the following: • • • If the selected analysis or design study is not running, Mechanica informs you that it is not. If Mechanica is currently running the selected analysis or design study started during the current session, Mechanica gives you the opportunity to confirm that you want to stop the run. If you confirm the stop, Mechanica terminates the run and displays a message that the run has successfully been stopped. Monitoring an Analysis or Design Study Run After you create an analysis or design study and start the run, use the Analyses and Design Studies dialog box to monitor the progress of the run. You can view the status window as the run progresses and also check for errors and messages. Using the Analyses and Design Studies dialog box, you can do the following: • Review errors and messages generated when you are running an analysis or design study by selecting the Info>Diagnose menu option. 785 Structural and Thermal Simulation - Help Topic Collection • • Check the status of your run by selecting the Info>Status menu option or clicking the Display Study Status button. See the log file for a run by selecting the Detailed Summary check box. The log file appears in the same window as the status. You can toggle between the status and the log by selecting and clearing the Detailed Summary check box. Status/Summary To access a summary report for the analysis or design study you select, select the Info>Status menu option, or the Display Study Status button on the Analyses and Design Studies dialog box. You can use the summary report to: • • check the status of a run access information about a completed run The summary report includes the following information for the entire analysis or design study: • • • a model summary at the beginning, listing the model type and the number of elements, points, edges, and faces in the model a running status of convergence information that shows how far the analysis has gone, plus the quality of the convergence and the estimated error a memory and disk usage summary at the end, including the total elapsed time, total CPU time, maximum memory usage, and the amount of disk space used by various files You can toggle between the status report window and the detailed summary report by selecting or clearing the Detailed Summary check box at the bottom of the status report window. If you access the status report while the run is in progress, Mechanica adds new information to the dialog box as the engine updates the report file. You can access this same file through your operating system. The file is called study/study.rpt, located in the directory for output files (where study is the name of your design study). Summary Report Contents The summary report includes the following information for the entire design study: • • a model summary at the beginning, listing the model type and the number of elements, points, edges, and faces in the model a running status of convergence information that shows how far the analysis has gone, plus the quality of the convergence and the estimated error 786 Structural and Thermal Simulation • a memory and disk usage summary at the end, including the total elapsed time, total CPU time, maximum memory usage, and the amount of disk space used by various files The contents of the body of the summary report vary by design study and analysis type: • • • • • • Standard Studies: Static, Large Deformation Static, Contact, Prestress Static, Modal, Prestress Modal, Buckling, Steady-State Thermal, and Transient Thermal Analyses Standard Studies: Dynamic Time, Frequency, and Random Analyses Standard Studies, Dynamic Shock Analyses Global Sensitivity Studies Local Sensitivity Studies Optimization Studies RMS Stress Error Estimates Mechanica displays an RMS stress error estimate for all analyses that use the single pass adaptive convergence method. The stress error does not include regions of potential singularities. Mechanica does not include this information when all of the external edges have potential singularities. For static and contact analyses, Mechanica displays the following information: • • Load Set Name — The name of the load set to which the RMS stress error estimate applies. Stress Error — Obtained by sampling the local error estimates along external edges. The estimate excludes regions with potential singularities (constraints, reentrant corners). You can use the stress error as an uncertainty for local stress values. % Of Max Prin Str — Keep in mind that if the maximum principal stress occurs at a singular region of the model, Mechanica excludes it from the sampling when evaluating the stress error estimate. In this case, the % Of Max Prin Str can be artificially low. To assess the achieved stress accuracy, it is always better to use the absolute stress error estimate (from the previous column) rather than this relative value. For modal, prestress modal, and buckling analyses, Mechanica displays the following information: • • mode stress error (% of Max Modal Stress) • 787 Structural and Thermal Simulation - Help Topic Collection Error Messages For all design studies, the summary report also issues two types of error messages: • • Warning messages — If the engine detects an unexpected situation that does not stop the progress of a run, it issues a warning message. This message indicates that there may be a problem requiring further attention. Fatal error messages — For any design study that stops with a fatal error, Mechanica writes a message explaining the error, and in many cases, advises you of corrective action to take. For some fatal errors, Mechanica directs you to use the Results command to see a diagnostic display of your model with entities associated with the error highlighted. Results for a run may be available, even if the run ended with an error: • • • • For each p-loop pass in a static, prestress static, modal, prestress modal, buckling, or contact analysis, Mechanica calculates displacement and stress results. For each p-loop pass in a steady-state thermal analysis, Mechanica calculates temperature and flux results. For the quick check convergence method, Mechanica displays a warning after the convergence loop log, informing you that convergence has not been checked. For the multi-pass adaptive convergence method, following the final p-loop pass, Mechanica writes a message stating that convergence to the specified percentage either was or was not attained. If your run did not converge, you can review a convergence graph for most of the quantities that Mechanica uses for convergence. Time and Disk Usage Information After each milestone, Mechanica displays the time and disk usage information in this format: Elapsed Time CPU Time Memory Usage Work Dir Disk Usage Step Elapsed Time Step CPU Time (sec): (sec): (kb): (kb): (sec): (sec): 29.27 23.48 3731 253 29.27 23.48 Following is a description of each of the lines showing times: • Elapsed Time — the total time from the start of the run through the previous milestone, or step 788 Structural and Thermal Simulation • • • CPU Time — the time your CPU has been in use from the start of the run through the previous milestone, or step Step Elapsed Time — the total time for the previous milestone, or step Step CPU Time — the time your CPU was in use during the previous milestone, or step If an error causes your run to fail, Mechanica displays a message at the end of the log. You can find a more specific error message in the summary window. To see the summary window, select Info>Status on the Analyses and Design Studies dialog box. If no log file exists for the design study you select, Mechanica displays a message that it cannot find the file. If the machine you are using to run the engine is equipped with parallel processors, Mechanica automatically uses all CPUs in the system for the run. However, you can manually specify the number of CPU's devoted to the run if you want to limit the number of CPUs you use. In cases where the ratio of elapsed time to CPU time is close to a value of 1 with one CPU, your solution times may benefit from running the engine in parallel processing de. For other ratios, you may experience performance degradation. For information on the benefits and limitations of parallel processing as well as a discussion of how to manually specify the number of CPU's, see Strategy: Running the Engine with Parallel Processing. Diagnose Select the Info>Diagnose option on the Analyses and Design Studies dialog box to open the Run Diagnostics dialog box. Use this dialog box to review the warnings and errors that Mechanica generates during a run. The software highlights the geometry associated with each error and places a marker on each instance of faulty meshing. Troubleshoot Run Problems You may encounter the following run problems: • Incomplete runs — If a run ends in an error, in some cases you might still be able to display intermediate results if there is one completed p-pass. The engine calculates stress and displacement values or temperature and flux values after each p-pass. You can also create p-level fringe plots from intermediate results. Depending on the nature of the error, however, the engine may not produce convergence information for the run. On UNIX systems, you can also use intermediate results for a run that is still in progress. 789 Structural and Thermal Simulation - Help Topic Collection Note: Keep in mind that the engine overwrites existing intermediate results each time it writes new results. At certain points during a run, Mechanica locks the results files so it can write data to them. When this occurs, you cannot access intermediate results. • Study does not converge — If the summary report says that your study did not converge during the run, and you used the multi-pass adaptive convergence method, you should look at a convergence graph to get more information. For more information, see Strategy: Fixing Convergence Problems. You may also be able to circumvent run problems by managing your computer resources effectively. For technical information on resource and performance management, see Managing Memory and Swap Space, Guidelines for Managing Disk Space Resources, and Managing Performance. Troubleshoot High Elapsed Run Times One indication of computer system performance is the ratio of elapsed time to CPU time for Mechanica engine jobs. A high ratio of elapsed time to CPU time can indicate a performance problem, either with the settings you are using to run Mechanica or with your computer system. For jobs running the direct solver, a ratio of elapsed time to CPU time much greater than 4 can indicate a problem. For jobs running the iterative solver, a ratio much greater than 7 can indicate a problem. The iterative solver generally has a higher ratio of elapsed time to CPU time because it does more I/O per calculation than the direct solver. Following are possible causes of high elapsed times: • Running more than one application at a time — This might not be a true performance problem unless the applications are competing with each other for access to the CPU, memory, or disk. If performance is lower than you expect, consider what other applications might have been competing for resources. Determine whether the problem is repeatable by rerunning the job when there is little or no other activity on the machine. • • • Setting the solver RAM (solram) value too high Setting the solver RAM (solram) value too low Starting the iterative solver after pass 3 or later, instead of after pass 2 — Unless you are solving a class of problems that consistently demonstrate better convergence by starting the iterative solver after pass 3, always start the iterative solver immediately after pass 2. 790 Structural and Thermal Simulation Starting the iterative solver after pass 3 or later frequently results in greatly increased I/O and elapsed time, with little or no reduction in the number of iterations required for convergence. • Using remote NFS-mounted disks for your working directories — I/O to network disks can be up to 10 times slower than I/O to local disks. For example, a local disk might transfer data at 10 MB/sec, whereas a remotely mounted disk might transfer data at only 1 MB/sec. Use local disks whenever possible. Using swap space that is not local to the machine — Add local swap space and avoid using remote swap space. Using swap space or disk space that is not dedicated to that purpose — Some operating systems allow an area of a disk to be shared dynamically between temporary files and swap space. Switching from this type of dynamic sharing to dedicated disk space or dedicated swap space can provide much better performance. You can also gain performance by placing the swap space and the scratch files on separate physical disks. Running a large job with insufficient machine RAM — The performance of many programs suffers when the virtual memory usage exceeds the available machine RAM. However, Mechanica typically uses only a small part of memory at a time. Therefore, performance can remain stable even when the reported total memory usage is 2 or 3 times machine RAM, and sometimes as much as 5 times machine RAM. • • • If you follow the guidelines for all run-setting parameters and you still suspect poor performance, compare the ratio of elapsed time to CPU time and compare the memory usage for this job with previously run jobs using similar models. Make sure all runs were made on the same machine under the same work load conditions. Similar models should have the same element and analysis types and use the same type of solver. If the ratios of elapsed time to CPU time and memory usage to machine RAM are both high, you might need to install more machine RAM in order to improve performance. In some cases, it helps to decrease the solram allocation or reduce the size of the model you are analyzing. For more information on the use of virtual memory, see Managing Memory and Swap Space. mecbatch This command lets you to run a single design study or a series of design studies from your operating system. Mechanica runs the studies in the order in which you enter them into the batch file. If one study ends in an error, Mechanica continues running the remaining studies in the file. You can monitor the status of the runs and review the summary file by selecting Info>Status or the Display study status button on the Analyses and Design Studies dialog box. 791 Structural and Thermal Simulation - Help Topic Collection Use mecbatch The mecbatch command executes from your operating system the run of one or more design studies you previously included in a batch file. To use mecbatch, for each study you want to include in a batch file, do the following: • • • Select the Analysis>Mechanica Analyses/Studies command. Select the design study you want to batch from the dialog box. Select Run>Batch on the Analyses and Design Studies dialog box. The Batch dialog box appears. You can use this dialog box to specify a new name for the batch file, change the directory where this file is stored, or append the study to an existing batch file. By default, Mechanica names the file mecbatch (mecbatch.bat on Windows) and places it in the directory from which you started Mechanica. When you are ready to run the mecbatch command: • • Open a command shell. Enter mecbatch at the operating system command prompt. Note: If you changed the name of the batch file, enter that name instead of mecbatch to start running the design studies. The msengine command for an individual design study contains information you entered on the Analyses and Design Studies dialog box. Each time you select Run>Batch on the Analyses and Design Studies dialog box, Mechanica places an msengine command for a design study. msengine Use this command to run a single design study from your operating system. You can run a study containing structural analyses, thermal analyses, or both. In order to use this command, you need engine input files. When you select Run>Batch on the Analyses and Design Studies dialog box, Mechanica does the following: • • writes the input files that the Structure engine needs for the run, but does not actually start the run places an msengine command in a batch file each time you use the Batch option 792 Structural and Thermal Simulation Optionally, you can run a single design study by manually entering the same msengine command that Mechanica placed in the batch file. You do this by entering the following at the command prompt: msengine study [options] where study is a directory with the same name as your design study. This directory contains the engine input files. You also use the msengine command to access external optimizers for design optimization. After the msengine command executes the run of your design study, you can monitor the status of the run and review the summary file by selecting Info>Status on the Analyses and Design Studies dialog box. Use msengine You can specify one or more of the following options after the input directory name: • • • • • • • • • • • • • –i input_dir — Specifies the location of the directory containing the engine input files. –w working_dir1:working_dir2:... — Specifies the location of the directory or directories in which the engine places temporary files during the run. –solram ram_size — Specifies the amount, in megabytes, of memory to be allocated for direct solver memory and for element data for the iterative solver. –iter n — Specifies that the engine uses the iterative solver after polynomial pass n, a number from 1 to 8. –sturm option — Specifies whether or not the Structure engine performs a Sturm sequence test for a modal analysis. –gdp — Specifies that the engine uses an alternative algorithm for an optimization design study. –extopt — Specifies that Mechanica uses an external optimizer to run either a function evaluation (using a standard study) or a gradient evaluation (using a local sensitivity study). –ascii — Specifies that the engine writes the engine output files in ASCII format. –p password — Specifies an optional password. –T — Causes the design study to run in demo mode. –bsram ram_size — Specifies the amount, in megabytes, of block solver RAM the engine uses for equation solving. –elram ram_size — Specifies the amount, in megabytes, of RAM available to store element matrices created by the iterative solver. –massnorm — Specifies that the Structure engine mass-normalizes mode shape vectors instead of unit-normalizing them in modal analysis. 793 Structural and Thermal Simulation - Help Topic Collection Use External Optimizers Use external optimizers to utilize optimizers other than SQP and GDP to perform design optimization. When you use alternate external optimizers, instead of defining an optimization study, you define one of these two types of study, depending on what you are trying to do: • • Standard study — To perform a function evaluation, define a standard study with all design parameters defined. Local sensitivity study — To perform a gradient evaluation, define a local sensitivity study. You will always need a standard study for function evaluation. If the external optimizer can benefit from gradient information, use a local sensitivity study. If you are running a function evaluation, enter this command: msengine –extopt <standard study name> If you are running a gradient evaluation, enter this command: msengine –extopt <local sensitivity study name> Before executing either of these commands, you need to write a wrapper code that defines the design problem and calls the external optimizer, which in turn calls Mechanica. To use an external optimizer with your study, do the following: • • • Define the appropriate study. Write the wrapper code that calls the external optimizer. Execute the msengine –extopt command. The wrapper code calls the external optimizer, which generates the mech_extopt.in file, and is read by Mechanica. When the study finishes running, Mechanica sends data containing the design objectives and the limits to a mech_extopt.out output file. 794 Structural and Thermal Simulation For information on the format of these files, see: • • mech_extopt.in File Format mech_extopt.out File Format FEM Solvers About Running FEM Analyses and Generating Output Decks Once you generate the mesh for your model successfully, you can perform additional reviews of your mesh, run a FEM analysis from within Mechanica using one of the supported FEA solvers, or generate an output deck that you can use outside of Mechanica. You perform these activities by selecting the Analysis>FEM Solution command and completing the Run FEM Analysis dialog box. Before you start a run, you should have created all modeling entities and generated a mesh for your model. If you plan to run an analysis instead of outputting a deck, you should also have defined an analysis. To give you a general idea of the process you might use, here is a description of how you use the Run FEM Analysis dialog box to prepare for and start a FEM analysis run or to generate an output deck for one of the FEA solvers: • Use the Run FEM Analysis dialog box to choose the solver you are interested in or to select the displayonly method for reviewing the mesh. Set the dialog box to output to a file and click OK to output the mesh. Use the commands on the REVIEW MESH menu to examine the mesh. If you find problems, adjust the model and mesh. • Review the Mesh • • • Run the Analysis or Generate the Deck • • Use the Run FEM Analysis dialog box to select the solver you are interested in and define other aspects of the run, such as the element shape, analyses, and coordinate systems. If you want to run a FEA analysis from within Mechanica, set the dialog box for an online or background run. If you want to generate a deck for later use with one of the FEA solvers, set the 795 Structural and Thermal Simulation - Help Topic Collection dialog box to output to a file. Be aware that this process varies depending on your needs. For some models, you may feel comfortable omitting the mesh review cycle—proceeding immediately with an online run or deck generation. For other models, you may only want to complete the mesh review phase. Solving a Model Using an FEA Program Use the Analysis>FEM Solution command to open the Run FEM Analysis dialog box. This dialog box enables you to review the solver mesh, start an FEA program directly from Mechanica, or generate an output deck for use outside of Mechanica. The dialog box includes the following items: • • • • Solver — Select the solver you want to use for your run or for which you want to generate an output deck. You can also create a neutral file deck for use with solvers that Mechanica does not directly support. Analysis — Select the type of analysis you want the FEA solver to run or for which you want Mechanica to create an output deck. Element Shape — Use the buttons in this area to specify the element shape, which, in turn, determines the order of the finite elements. Higher order elements can, in some cases, result in better model definition. Analyses — Select one or more analyses that you want to include in the run or output deck. Mechanica displays a list that includes the names of all analyses you have created for the analysis category you selected on the Analysis option menu. For example, if you selected Modal on the Analysis option menu, Mechanica lists each of the modal analyses you defined for the model. When Mechanica outputs the deck or sends the model to one of the solvers, it refers to the analyses you select to determine which loads, boundary conditions, and constraints to include in the run. • Coord System — Select the coordinate system that the solver should use when formulating results. You cannot select a coordinate system if you select Display Only on the Solver option menu. If you do not select a coordinate system, Mechanica uses the WCS. Aux Coord System — Select any additional coordinate systems you want to include in the run. You can select one or more individual coordinate systems from the list by highlighting items on the list or select all coordinate systems. You cannot select an auxiliary coordinate system if you select Display Only on the Solver option menu. NASTRAN Analysis Template — Select a template to use for the NASTRAN analysis. This area only appears if you select MSC/NASTRAN on the Solver option menu. run methods area — Use the remaining three items on the dialog box to indicate how you want Mechanica to process the run—online, in the background, or by outputting a deck for the chosen solver. • • • 796 Structural and Thermal Simulation After you complete an online or background run, the system stores the model mesh and the FEA results in a single database file called model.frd (where model is the name of the model). You use this file when you view results in the postprocessor. To fully understand how Mechanica uses the .frd file and what this file contains, see Storing and Retrieving FEA Results. Selecting a Solver Use the Solver option list on the Run FEM Analysis dialog box to select a solver for your FEM analysis run or mesh review. The Solver option list includes the following: • • • Display Only — Display a solver mesh for your model independent of solver type. ANSYS — Perform a structural, modal, or thermal analysis of your model using the ANSYS solver. You can also use this option if you want to create an output deck formatted for use with ANSYS. MSC/NASTRAN — Perform a structural or modal analysis of your model using the NASTRAN solver. You can also use this option if you want to create an output deck formatted for use with NASTRAN. If you are using MSC/NASTRAN as a solver, it creates a NASTRAN results file with the .xdb extension in addition to the model.frd file. Mechanica FEM mode gives you a direct access to the .xdb file, so you can view NASTRAN results in the postprocessor. For more information, see Loading NASTRAN Results Database. • FEM Neutral — Output a FEM Neutral File (FNF file) for use with solvers other than the ones Mechanica supports. If you want to use this option, the solver you plan to use must be able to correctly read the FNF format. You can configure Mechanica to automatically display ANSYS or NASTRAN as the default setting for the Solver scroll list when you open the Run FEM Analysis dialog box. You do this by setting the fem_default_solver configuration option to ANSYS or MSC/NASTRAN. Your ability to view FEA solver results in the Mechanica postprocessor depends on the solver you used as well as whether you ran the solver online or output a deck. FEM Analysis Types You can select one of the following analysis types from the Analysis option menu on the Run FEM Analyses dialog box. You can select any analysis type regardless of the product you are currently working in—whether or not you have actually defined an analysis of that type. The analysis type you select is the one that the FEA solver will perform or for which Mechanica will output a deck. The Analysis option menu includes these items: • • Structural — Outputs a model and mesh for structural analysis. Modal — Outputs a model and mesh for modal analysis. 797 Structural and Thermal Simulation - Help Topic Collection • Thermal — Outputs a model and mesh for thermal analysis. Note that NASTRAN does not support thermal analyses. When you select an analysis type, Mechanica adds all existing analyses of that type to the Analyses area of the dialog box. You can then select one or more individual analyses from that area. You can also choose not to select an analysis. Note that, if you select Structural from the Analysis option menu, Mechanica lists both structural and modal analyses in the Analyses area. If you select a modal analysis under these circumstances, Mechanica runs a structural analysis that includes the constraints, frequency specifications, and so forth from the modal analysis definition. Element Shape Use the Element Shape area on the Run FEM Analysis dialog box to determine the type of elements the solver will use. The Element Shape area includes the following: • Linear — Use linear elements for the run or the output deck. Linear elements have only corner nodes, straight edges, and planar faces. These elements are best suited for models with relatively planar and straight-edged topologies, and can improve solution times for these models. Mechanica outputs linear elements as follows: o shell elements — Uses 3-node elements for triangular mesh and 4node elements for quadrilateral mesh. o solid elements — Uses 4-node elements. Parabolic — Use parabolic elements for the run or the output deck. When Mechanica runs with or outputs parabolic elements, it uses the same mesh, but adds mid-edge nodes to each element. These added nodes aid in the approximation of model curvature by enabling the mesh elements to flex at the added nodes. This ability to flex enables the elements to conform to curved model surfaces better. Mechanica outputs parabolic elements as follows: o shell elements — Adds a mid-node to each edge, using 6-node elements for triangular mesh and 8-node elements for quadrilateral mesh. solid elements — Adds mid-nodes to each tetrahedral edge and outputs 10-node elements to the file. • o If you select Parabolic, you can use the Fix Elements button to adjust the mesh. This button adjusts mid ratios so that they do not exceed values you specified on the Element Quality Checks dialog box. The Fix Elements button is particularly useful if your model has a moderate to high degree of curvature. 798 Structural and Thermal Simulation Determining a Run Method Run Methods While performing a FEA analysis, the system passes the model mesh data to the solver for processing. You can conduct the solve either online or in the background. If you want to use the model data outside of Mechanica, you can also output a deck for the solver of your choice. To indicate which of these methods you want Mechanica to use, you select one of the three items in the run methods area near the bottom of the Run FEM Analysis dialog box. Note: If you plan to run online or in the background, you must supply the software with the correct path to the FEA executable. You provide the path by including the appropriate options in your configuration file. The run methods area of the dialog box includes these items: • Output to File — Outputs a deck formatted for the solver you selected. You can use this deck outside of Mechanica as input for your solver. If you select this option, you must also enter the filename that you want Mechanica to use when writing the deck. You can also output to user-defined solver other than the ones that appear on the Solver option list, provided the solver supports a FEM Neutral File. • Run On-Line — Runs the solver online saving mesh and results in the model.frd file. This ties up the Pro/ENGINEER session until the processing is complete. When it is complete, the system automatically enters the postprocessor and loads the results section from the name.frd file into memory. Run in Background — Runs the solver in the background and stores the results in the file model.frd, where model is the name of your model. Your current session is not interrupted and you can continue working with another model. After the processing is complete, you can view the analysis results in the postprocessor. • Your ability to view FEA solver results in the Mechanica postprocessor depends on the solver you used as well as whether you ran the solver online or output a deck. Reviewing a FEM Mesh Use the Mesh>Review command to review aspects of your mesh. You can also review a mesh if you select Display Only from the Solver option menu on the Run FEM Analysis dialog box or use Output to File to output a solver deck. When you select the Review command or use one of the Run FEM Analysis dialog box methods, the REVIEW MESH menu appears. This menu allows you to review the mesh after it is created or after an analysis is run. 799 Structural and Thermal Simulation - Help Topic Collection The menu includes: • Meshes — Review a mesh after you create it. You can review a list of components by path within the top-level assembly hierarchy, the number of elements and nodes, and the range of element and node ID numbers. You can also review the range of element, node, and local mesh entity IDs with the Mesh ID Offset mesh control applied. This type of review can help you identify and resolve any numbering conflicts. Nodes — Review nodes by selecting: o Coord Systems — Select this option to display a coordinate system icon at each selected node that will be oriented for nodal displacement. If the coordinate system is not Cartesian, then Mechanica calculates and displays the R, , and Z or direction instead. o All — Highlight all element nodes and display their node IDs. o Boundary — Highlight only boundary nodes and display their node IDs. This option only appears if the mesh includes solid elements. o Node ID — Highlight an individual node and display its ID. If you select this option, you enter the integer ID for the node you are interested in. o Select — Highlight an individual node and display its ID. In this case, you use your mouse to select the node on your model. o List Unused — Generate a list of unused node IDs. You use this option to help detect node ID conflicts in hierarchical meshes. You can correct these conflicts by applying mesh ID offset mesh controls to the conflicting nodes. Elements — Review elements by selecting: o Coord Systems — Display the coordinate system for the elements that you review. o Shell Normals — Display the shell normals for the elements that you review. This check box only appears if the mesh includes shell elements. o All — Highlight all elements and display their element IDs. o Boundary — Highlight only boundary elements and display their element IDs. This option only appears if the mesh includes solid elements. o Element ID — Highlight an individual element and display its ID as well as its node IDs. If you select this option, you enter the integer ID for the element you are interested in. o Select — Highlight an individual element and display its ID as well as its node IDs. In this case, you use your mouse to select the element on your model. o List Unused — Generate a list of unused element IDs. You use this option to help detect element ID conflicts in hierarchical meshes. You can correct these conflicts by applying mesh ID offset mesh controls to the conflicting elements. Connectivity — Highlight edges that are only included in one shell surface. You can also use this command to highlight a free node on a one-dimensional element such as a beam or spring. • • • 800 Structural and Thermal Simulation If you review the mesh at run time, Mechanica adds these options to the REVIEW MESH menu: • • • Materials — Highlight elements made of selected materials by selecting: o All — Highlight all elements with specified materials o Material ID — Highlight elements by specific material. Analyses — Highlight nodes or elements from a selected analysis and examine how the loads and constraints defined for the analysis apply to the mesh. Hard Points — Display an information window listing nodes that were created at hard points on the model. Outputting Data to an Offline FEA Program If you are going to perform finite element analysis on your model using an offline FEA program, you must create an output file, or deck, for the model's mesh data. This deck includes the following: • • • • the model's mesh elements and nodes output in a format compatible with the particular FEA program to be used all material data assigned to the model all properties assigned to the model all analyses applied to the model Mechanica creates output decks in a variety of FEA formats. When outputting a hierarchical mesh of an assembly, Mechanica creates a single output file. Depending on whether your goal is to create an output file for MSC/NASTRAN or any other solver, Mechanica arranges the data in two different ways: • For the NASTRAN solver, Mechanica outputs component meshes into sections of a single file. Each section groups together all items that belong to a particular component, such as coordinate systems, materials, properties, nodes, elements, and so on. For other solvers, Mechanica lists separately all assembly nodes, all coordinate systems, all materials, and so forth. The solver then restores the hierarchy according to information each list provides. • Outputting to a User-Defined Solver If a solver can accept input and generate output in the FEM Neutral Format, you can use it to solve a model. You can include the name of the desired solver in the Solver option menu by setting the pro_solver_name config.pro option. To enable the solver, you need to specify the path to the solver executable by setting the pro_solver_path config.pro option. 801 Structural and Thermal Simulation - Help Topic Collection A user solver should work as follows: path_to_solver_executable input_file output_file where: input_file — input file in the FEM Neutral format with the extension .fnf output_file — solution results file in the FEM Neutral format with the extension .fnf For example: /abc/def/fea_solver model.fnf model_res.fnf If it finds a solution, the user solver should return a zero value upon termination. To Display Run Errors If a run ended in an error, and an error message in the summary file for the run directs you to use Results to review a diagnostic display of your model, follow this procedure. 1. Select Analysis>Results or click The Results user interface appears. 2. Use the Results user interface to create a new result window containing the design study that ran unsuccessfully. For help with this step, see To Define a Result Window. The way you define the result window does not affect the diagnostic display. If you are only interested in the diagnostic display, use the default selections on the Result Window Definition dialog box. Partial results may also be available that enable you to define and show other types of result windows. 3. Click the Display definition(s) from selection button on the toolbar. Mechanica displays a message containing information about the error encountered during the run. 4. Click OK in the message box. Mechanica shows a diagnostic display of the model on which it highlights entities associated with the error. If sufficient results are available, Mechanica also shows any other result windows you defined. . 802 Structural and Thermal Simulation To Select the Iterative Solver 1. Select Analysis>Mechanica Analyses/Studies or click The Analyses and Design Studies dialog box appears. 2. Select Settings from the Run menu or click The Run Settings dialog box appears. 3. Select the Use Iterative Solver check box. Additional items appear on the Run Settings dialog box. 4. Enter a value for the maximum number of iterations. 5. Enter a p-loop pass number for After P-Loop Pass. The iterative solver takes over after the pass you specify. (Configure run settings). . Guidelines for Allocating RAM for Solver and Element Data The default values for RAM allocation for the block solver and for element data are minimal values. If your machine has sufficient RAM and swap space available, you may be able to improve the performance significantly by increasing RAM allocation above the default values. If you decide to use values other than the defaults, you can generally improve performance by following these guidelines: • For a static or prestress analysis with the direct solver, block solver RAM should not exceed one-half of your machine RAM. In this case, the RAM allocation for element data has no effect and the default value is the ideal choice. For a static or prestress analysis with the iterative solver, block solver RAM and the RAM allocation for element data together should not exceed threequarters of your machine RAM. A recommended starting point is to allocate one-tenth of your machine RAM for your block solver and one-half of your machine RAM for element data. For a modal, prestress modal, or buckling analysis, block solver RAM and the RAM allocation for element data together should not exceed one-half of your machine RAM. A recommended starting point is to allocate one-quarter of your machine RAM for the block solver and one-quarter for element data. Block solver RAM and the RAM allocation for element data together should never exceed three-quarters of your machine RAM. • • • You can find specific information about the block solver RAM and the RAM allocation for element data in the element calculations section of the study/study.pas file, located in the directory for output files. 803 Structural and Thermal Simulation - Help Topic Collection To set solver RAM allocation, refer to Guidelines for Setting Solram. Detailed Summary When you select the Detailed Summary check box on the status window during or after a run, you access a log file for the run. You can use the log file to: • • check the status of an analysis or design study during a run. Mechanica adds new information to the log as the engine updates the log file access information about a completed run You can access this same file through your operating system. The file is called study/study.stt, located in the directory for output files (study is the name of your analysis or design study). Log information includes the following: • • • • • • the start and end time and date of the run a summary of the AutoGEM settings you specified for your model the settings on the Element Limits dialog box a running status report from AutoGEM a summary of the elements AutoGEM created the time and date of several milestones reached during the run Milestones can include: • • • the start and end times for calculating an analysis within the design study the time for starting a p-loop pass in an analysis other points at which the engine starts an action For more information about the displayed log information, see Time and Disk Usage Information. Restrictions When Specifying Multiple Working Directories Be aware of the following restrictions and behaviors when specifying multiple working directories. Your job may halt prematurely if you do not observe the following: • The only directory that can be shared with the study directory (also known as the directory for output files) is dirn—the last directory you specify. Mechanica fills dir1 to dirn completely with the .bas files if necessary, leaving no space for other types of files. In order to ensure that the study directory has adequate space, write it to a file system separate from any working directory. 804 Structural and Thermal Simulation Your engine job will stop if the study directory runs out of space. • • The only directory that can be NFS-mounted is dirn. Directories dir1 to dirn–1 must be local file systems. The .bas files cannot split past the first NFS directory in the list because of NFS limitations. Directories dir1 to dirn must have enough space available to run your job. There may be less available space than you expect. For example, if another job is using one of the directories in the list at the same time as your job is, it may decrease the available space. You can increase the space available to your job by: o o o adding local directories to the directory list freeing space in dir1 to dirn by moving or compressing files before starting your job adding more local disks to your system Managing Memory and Swap Space All computers that run Mechanica use virtual memory, which allows programs to run on your computer as if it had more RAM than is actually available. Use of virtual memory involves some compromises, such as the following: • Whatever memory your programs use must be backed up by an equivalent amount of swap space, also known as paging space. Swap space is a specially formatted area of your disk that the operating system can use while it is managing the real memory, or machine RAM, of your computer. In principle, the operating system could move all or part of the virtual memory used by your program to the swap space area at any time. Therefore, if you have a shortage of swap space, the operating system may cancel your job because there is not enough room for your job to run. • When the virtual memory used by your programs exceeds the available real memory, performance may suffer. Performance suffers most when the operating system must make frequent transfers between real memory and the swap space area—that is, when the program repeatedly accesses more virtual memory than is available in machine RAM. Performance is acceptable only when transfers between real memory and the swap space area are infrequent—that is, when the virtual memory area used by the program is smaller than the available machine RAM. For 32-bit machines, Mechanica cannot access more than 2 GB of virtual memory, regardless of the amount of RAM or swap space available on your computer. For 64bit machines, Mechanica is limited to about 8 GB. If your operating system has memory limits, Mechanica might be able to access even less virtual memory. If Mechanica attempts to use more than the maximum available memory, your job is likely to fail. 805 Structural and Thermal Simulation - Help Topic Collection You may be able to correct the failure by: • • • • decreasing solver RAM (solram) increasing memory limits increasing swap space decreasing model size For additional information, see Guidelines for Allocating Swap Space. Guidelines for Managing Disk Space Resources The following guidelines will help you to manage disk space resources: • Try to anticipate resource usage and avoid resource shortages. Mechanica is storage-intensive, so make sure you have ample disk and swap space, and monitor the resource usage periodically. This approach helps prevent an unexpected shortage of resources. Resource and performance information is written in the engine log file (the study/study.stt file, where study is the design study name). The engine updates the information in this file for each step of the analysis. While your job is running, you can estimate total disk space required by reviewing the information printed in the study/study.pas file immediately after the heading Begin Element Calculations. This information tells you how large the factored global stiffness matrix will be (if you are using the direct solver) and how large the element matrix files will be. For jobs using the direct solver, total disk space is approximately the size of the global matrix file plus three times the size of the element matrix file. For jobs using the iterative solver, total disk space is approximately the size of the element matrix file plus the global matrix profile for the last pass that used the direct solver (that is, the pass immediately before the first iterative solver pass). Some platforms allow you to configure two or more disks together as a striped file system. A striped file system splits disk I/O among several disks in parallel. You may be able to improve I/O performance and reduce elapsed times by directing Mechanica working directories to the striped file system. • • • • • Managing Performance The engine log file (study/study.stt file) maintains detailed information on how much memory, disk space, elapsed time, and CPU time the engine uses as your job runs. You can review this file to monitor resource requirements and performance. For example, reviewing Step Elapsed Time and Step CPU Time can help you predict how much time a particular job step will take at a future p-pass. Results inconsistent with the trends in this file can help you identify and fix performance problems and resource shortages. 806 Structural and Thermal Simulation Modifying Analyses and Design Studies Use the Analyses and Design Studies dialog box to modify analyses and design studies. The dialog box contains a list of existing analyses and design studies. To modify an analysis or design study, you select an analysis or design study from the list, and then select Analyses/Study from the Edit menu. The dialog box you used to create the analysis or design study appears so you can make any necessary changes. Analyses and Design Studies Toolbar For fast access to some of the most commonly used commands on the menu bar, the Analyses and Design Studies dialog box provides a toolbar with these buttons: Button Action/Name Edit Study — Opens the dialog box for the analysis or design study you select so you can modify it. Copy Study — Copies an analysis or design study. Delete Study — Deletes the selected analysis or design study. Start Run — Starts an analysis or design study run. Stop Run — Stops an analysis or design study run. Configure Run Settings — Opens the Run Settings dialog box so you can define the settings for a run. Display Study Status — Opens the status window for the analysis or design study you select. Strategy: Improving Convergence If an analysis does not converge, the problem is typically due to a few unconverged element edges located in specific areas of the model. • • • Define a p-level plot for that analysis and use Dynamic Query to identify the locations of the edges with maximum p-levels. Consider whether the high p-level is due to a local singularity. If so, you can address the problem by spreading the constraints or loads over a larger area or excluding noncritical elements from the convergence check. If these techniques are not an option, then break up the model into smaller elements in the critical areas that did not converge. Although this method can be tedious, it is a reliable way of improving convergence. 807 Structural and Thermal Simulation - Help Topic Collection -massnorm This option specifies that the engine mass-normalizes mode shape vectors instead of unit-normalizing them in modal analysis. BLF Convergence The convergence index is the maximum percentage change of any BLF (buckling load factor). In a buckling analysis, Mechanica calculates BLF and mode shape for each buckling mode you specify. The BLF is the magnification factor by which the loads applied in a previously specified static analysis would have to be multiplied to produce the critical buckling load. For more information, see Buckling Analysis. –iter n Specifies that the engine uses the iterative solver after polynomial pass n, a number from 1 to 8. For more information on the iterative solver, see Select the Solver. –i input_dir Specifies the location of the directory containing the engine input files. This is the directory with the same name as the design study you are running. The directory is the same as the directory for output files you specify on the Run Settings dialog box. By default, Mechanica places this directory in the current directory. Optimization Studies The report contains the following information for each iteration, or step, of the optimization: • • • the value of each parameter the value of the goal measure and each limit measure a memory and disk usage summary at each step, similar to the summary included at the end of every design study The parameter value is a percentage of the range for the design parameter associated with the parameter. This value tells you where Mechanica has moved the design parameter at a specific stage of the optimization. At the end of the study, Mechanica lists the values for each parameter and measure for the best design found. 808 Structural and Thermal Simulation Measure Convergence The Structure engine calculates and reports in the summary report the convergence percentage of each measure. The convergence index is the maximum percentage change of any measure. The percentage change is the difference between the current pass and the preceding pass divided by the value at the current pass. For multiple load sets, the value is the maximum over all load sets. Local Sensitivity Studies The following information is included for each analysis in the study: • • • • • convergence loop log the value of each measure calculated for each type of analysis included in the study if you selected Calculate Reactions when defining a static analysis, values for the resultant load on the model in the global X, Y, and Z directions for modal analyses, the modal frequency for each mode (cycles per unit time) derivative of each measure calculated in the analysis with respect to each parameter Local Disp/Energy Index, Local Temp/Energy Index These are local measures of convergence. The engine checks the percentage change in total strain energy or total energy norm of each element, and the percentage change in the displacement or temperature along each element edge. After checking all elements and edges, the engine sets the local convergence index to the maximum value encountered. For multiple load sets, the value is the maximum over all load sets. Global RMS Stress Index This is an estimate of the square root of the error in the total strain energy, which is the difference between the strain energy at the current pass and the exact strain energy, divided by the exact strain energy. To estimate the exact strain energy, the engine extrapolates the total strain energies of three successive passes. The three successive passes are referred to as pass one, pass two, and pass three, with pass three being the most recent. The index might detect a significant error if the difference between pass three and pass two is not small compared to the difference between pass two and pass one. For multiple load sets, the value is the maximum over all load sets. 809 Structural and Thermal Simulation - Help Topic Collection Global Sensitivity Studies The summary report contains a convergence loop log for each sensitivity step of a global sensitivity study. For more information on global sensitivity studies, see Global Sensitivity Study. Global Energy Index This is an estimate of the square root of the error in the total energy norm, which is the difference between the energy norm at the current pass and the exact energy norm, divided by the exact energy norm. To estimate the exact energy norm, the engine extrapolates the total energy norms of three successive passes. This index handles the three successive passes as described for the Global RMS Stress Index. Convergence index values always lie between 0% and 100%. The engine may calculate values greater than 100% internally, but it reports 100% in this case. Convergence Indicators The convergence loop log also lists convergence indicators at each pass. These percentages are based on changes between the current pass and the preceding pass, and provide an indication of the accuracy of the results. If you intentionally define an analysis that requires only a single p-loop pass by setting the minimum and maximum polynomial orders to the same value, Mechanica sets the convergence indicators to 100% and warns that convergence has not been checked, because there is no preceding pass with which to compare. The Structure engine calculates the following convergence indicators: • • • • • • Measure Convergence Frequency Convergence BLF Convergence Local Disp/Energy Index, Local Temp/Energy Index Global RMS Stress Index Global Energy Index Strategy: Fixing Convergence Problems When a study does not converge, you should create a convergence graph result window. If the graph shows that the study almost converged during the run, the results are likely to be quite accurate. 810 Structural and Thermal Simulation If the graph shows that the quantity did not come close to converging, you should take one or more of these steps, and then run the study again: • Define and show a fringe plot of the p-level. This will show the polynomial level to which Mechanica calculated to reach convergence for each edge. If one or two elements went to much higher p-levels than the rest, you should try dividing those elements by adding datum points in that location to seed the mesh. If an element did not reach convergence at the location where a load, heat load, constraint, convection condition, or prescribed temperature is applied on a point, or at a small feature of significance, you should be sure you have the appropriate point options selected in the Feature Isolation area of the AutoGEM Settings dialog box. Proper use of these options enables AutoGEM to create small elements surrounding the point or near the small feature. Check the convergence value you entered when you defined the analysis. If that value is too tight, especially if it is below 1%, you should try loosening it. Check the polynomial order you entered when you defined the analysis. If the maximum is lower than 9, you should try increasing it. If you are primarily interested in a quantity other than the convergence quantity, check if that quantity converged. You only need to rerun the study if the quantity of interest did not converge or come close to converging. • • • • Frequency Convergence The convergence index is the maximum percentage change of any modal frequency. For more information on frequency, see Modal and Prestress Modal Analyses. Temperature Distribution Mechanica checks if a temperature load exists for an analysis that depends on it. Error Detection in Optimization Studies Mechanica checks if a measure is associated with the optimization goal if Goal is selected, and if at least one limit is defined if Limits on Measures is selected. If not, Mechanica displays an error message and does not start the run. –solram ram_size Specifies the amount, in megabytes, of memory to be allocated for direct solver memory and for element data for the iterative solver. This option when used overrides any values specified for the –elram and –bsram options. If you do not use the –solram option, solver memory is 128 megabytes by default. 811 Structural and Thermal Simulation - Help Topic Collection Inconsistent Shell Normals If the design study contains Structure analyses, Mechanica checks for inconsistent shell normals in 3D models. If you have not fixed the normal direction of shells, or you added any elements or flipped any normals since fixing them, Mechanica asks you if you want the element normals to be automatically aligned. Fixing normals may change the direction of any pressure load or material orientation you create. –sturm option Specifies whether or not the Structure engine performs a Sturm sequence test for a modal analysis. By default, the engine performs this test in certain situations to ensure that it has identified the correct number of modes of vibration. You can control Sturm sequence checking by using one of the following options: –sturm default Equivalent to giving no –sturm command line option. Mechanica performs a Sturm sequence test only for those modal analyses that include a search for rigid body modes. For nearly all models, Mechanica correctly identifies all of the modes of vibration when you use this option. Mechanica performs a Sturm sequence test for all modal analyses, which may significantly increase execution time. Mechanica does not perform a Sturm sequence test for any modal analyses. –sturm always –sturm never Error Resolution During error checks, Mechanica displays message boxes asking you whether or not you want to place the highlighted entities into groups. It does not consider boundary edges and faces to be errors and does not prevent the run from starting. If your model contains errors, Mechanica returns you to the Analyses and Design Studies dialog box without executing the run. If your model contains no errors, Mechanica continues on to the next step. If your model does not contain errors, or if you did not check for errors, Mechanica takes the following steps: • • 812 saves the model, prompting you to enter a model name if you have not previously saved it writes the engine input files and starts the engine Structural and Thermal Simulation The engine runs the design study in the background. At any time during the run, you can: • • Check the study's status by selecting Info>Status on the Analyses and Design Studies dialog box. Stop the run by clicking the Stop button. Convergence Measures Mechanica checks if measures are associated with any analyses in a design study that use the Measure option for convergence. If there are no convergence measures, Mechanica displays an error message and does not start the run. Boundary Faces Mechanica highlights all boundary faces—faces that belong to only one solid. Although these are not actually errors, you can check each boundary face to make sure it does not represent a missing element. If your model contains boundary faces that are not associated with a surface, Mechanica highlights just those faces separately. You can use this information to identify missing elements. Boundary Edges Mechanica highlights all boundary edges. A boundary edge is an edge associated with only one shell or solid, unless the edge is associated with a solid and a shell coincident with a face of that solid. If your model contains boundary edges that are not associated with a curve, Mechanica highlights just those edges separately. You can use this information to identify missing elements. Allowable Errors In most cases, Mechanica does not start a run if it finds errors. There are a few errors that do not prevent a run from starting, including: • • • loads, constraints, heat loads, prescribed temperatures, and convection conditions that result in singularities elements that should be linked gravity loads that have no effect For more information on allowable errors, see Check Model. 813 Structural and Thermal Simulation - Help Topic Collection Standard Design Study with Parameters You can also create an offset design study by running a standard design study with one or more parameters set to specific values. This option enables you to explore the design space "manually," through a "what if" study. Before defining and running a standard design study with parameters set, you need to define design parameters. For more information on design parameter creation, refer to Strategy: Using Design Parameters. The basic strategy for running an offset design study with specific parameters set and for reviewing the results is the same as for any standard design study. Following are some additional reasons for running offset studies: • • • To facilitate setting one or more parameters to specific values (for example, the next size permitted by your manufacturing requirements). This allows you to see how the model behaves without actually modifying the model. To set one or more design parameters to the start or end point of their range. This technique enables you to bracket the results within the design space. To explore a local region of the design space, such as near a design produced by an optimization study. You can save the version of the model Mechanica creates when you run an offset study. Standard Studies: Static, Large Deformation Static, Contact, Prestress Static, Modal, Prestress Modal, Buckling, Steady-State Thermal, and Transient Thermal Analyses The following information is included for each analysis in the study: • • • • • • • • • • • • • for Structure analyses, the convergence method convergence loop log RMS stress error estimates total mass of model total cost of model moments of inertia about WCS origin principal MOI and principal axes relative to WCS origin center of mass location relative to WCS origin moments of inertia about the center of mass principal MOI and principal axes relative to COM for each if you selected Calculate Reactions when defining a static analysis, values for the resultant load on the model in the global X, Y, and Z directions for modal analyses, the modal frequency for each mode (cycles per unit time) for static and steady-state thermal analyses, the value of each valid measure for that analysis for each load set 814 Structural and Thermal Simulation • • for buckling analyses, the buckling load factor (BLF) for each mode. If only negative BLFs appear, you should reverse the direction of the loads and rerun the previous static analysis and the buckling analysis. The first positive BLF mode is usually the one of interest. for contact analyses, the contact area for each load factor if the number of load increments is greater than one Standard Studies: Dynamic Time, Frequency, and Random Analyses The following information is included for each analysis in the study: • • • total mass of model total cost of model the value of each measure valid for that analysis, except measures using the At Each Step option Standard Studies, Dynamic Shock Analyses The following information is included for each analysis in the study: • • • • total mass of model total cost of model for each mode, the frequency, participation factor, effective mass, and total mass (the frequency is in cycles per unit time) the value of each measure valid for shock analyses –T Specifies that Mechanica run the design study in demo mode. The run cannot exceed a polynomial order of 4 in demo mode. Matching Parameters Mechanica checks if standard design studies with Set Parameters selected reference another design study. This can happen if the study contains a dynamic analysis with Use Previous Modes selected, or an analysis that includes a MEC/T temperature load. In either case, Mechanica checks that the parameters and parameter settings are the same in both the current study and the other study referenced by an analysis in the current study. If the parameters do not agree, Mechanica displays an error message and does not start the run. –p password Specifies an optional password. 815 Structural and Thermal Simulation - Help Topic Collection -gdp Specifies that the engine use an algorithm other than the default algorithm for an optimization design study. This algorithm, gradient projection (GDP), is an alternative to the default algorithm, sequential quadratic programming (SQP). If you allow the optimizer to run in its natural state, Mechanica begins the run using SQP. However, if it encounters an invalid model during an optimization and its several recovery attempts fail, the software attempts to resolve the problem by automatically switching from SQP to GDP for the remainder of the run. In some situations, you may want to use the -gdp option to enforce the GDP algorithm throughout the optimization. When making this decision, you should understand the advantages and disadvantages of each algorithm. SQP typically finds the optimum design faster than GDP does. The disadvantage of SQP is that it does not guarantee that your design satisfies your limits at the end of each iteration. It only guarantees that the optimum design satisfies your limits. This means that if SQP ever fails to find an optimum design, there may be no intermediate designs available that are improvements over the initial design. In contrast, GDP tends to produce a series of intermediate designs that satisfy your limits while getting closer to the goal. Thus, if speed is not an issue and you want to ensure the availability of interim designs, use the -gdp option. –elram ram_size Specifies the amount, in megabytes, of RAM available to store element matrices created by the iterative solver. This option is only relevant if you are also using the iter option. The value must be greater than 0.1. If you do not specify a value, or if you omit this option, the engine allocates 2 megabytes by default. Note: The bsram and elram options have been superseded by the solram option. If you choose to use bsram and/or elram, you must specify them on the msengine command line, or by editing the mecbatch file. This allocation and the –bsram allocation represent part of the memory the engine uses to run a design study. The engine dynamically allocates the rest of the memory it needs for the run. You can increase the speed of the iterative solver by increasing the amount of RAM you allocate with this option. As a general guideline, set this value to one-quarter of your machine RAM. Do not set this value to more than half of your workstation installed RAM. The optimal value also depends on other factors, such as what other processes are running on your machine. 816 Structural and Thermal Simulation –bsram ram_size Specifies the amount, in megabytes, of block solver RAM the engine uses for equation solving. The value must be greater than 0.1. If you do not specify a value, or if you omit this option, the engine allocates 8 megabytes by default. Note: The bsram and elram options have been superseded by the solram option. If you choose to use bsram and/or elram, you must specify them on the msengine command line, or by editing the mecbatch file. This allocation and the –elram allocation represent part of the memory the engine uses to run a design study. The engine dynamically allocates the rest of the memory it needs for the run. You can use the default allocation for any run. If you have a lot of RAM on your machine, large models will run faster if you specify a higher RAM. You can slow the run substantially if you specify an allocation that is too large to fit in available RAM. You can also slow the run if you do not specify sufficient space, especially if you specify less than the default. As a general guideline for large models, set this value to one-half of your machine RAM if you do not use the -iter option, and to one-quarter of your machine RAM if you do use the -iter option. The optimal value also depends on other factors, such as what other processes are running on your machine. For more information, see Setting Up a Run. –ascii Specifies that the engine writes the engine output files in ASCII format. Sample mecbatch File The following example of a mecbatch file would start two design studies: # Batch file written from: # Mechanica Wildfire 2.0 -Parametric Technology 2003 # Wed Sept 8 12:24:54 2003 # Design Study Name " study1 " $MECH_HOME/bin/msengine study1 -i ./ -w ./ -bsram 2 -elram 2 # Batch file written from: # Mechanica Wildfire 2.0 -Parametric Technology 2003 # Wed Sept 8 12:27:23 2003 # Design Study Name " study2 " $MECH_HOME/bin/msengine study2 -i ./ -w ./ -bsram 2 -elram 2 817 Structural and Thermal Simulation - Help Topic Collection Strategy: If Solver RAM Is Too Low If you set solver RAM (solram) too low, performance suffers because Mechanica must transfer data between machine RAM and disk files many more times than with a larger setting. Because disk drives transfer data roughly 100 times slower than machine RAM, excessive disk I/O can degrade system performance. Performance may degrade significantly if you set solram to 0.1 times machine RAM or less. In general, do not set the solram allocation to below 10% of machine RAM unless you have severe memory constraints and you are prepared to accept substandard performance. A solram allocation of 25% of machine RAM is preferable—a setting of 50% of machine RAM is usually optimal. For guidelines on setting the solver RAM allocation, refer to Guidelines for Allocating RAM for Solver and Element Data. Strategy: If Solver RAM Is Too High The purpose of solver RAM (solram) is to reduce the amount of disk I/O. If you set solram too high, performance usually suffers, even on machines with very large RAM, for the following reasons: • There will not be enough machine RAM for other important data. For example, Mechanica allocates many large, non-solver memory areas that will cause excessive swapping unless you leave enough spare machine RAM. Except for the solver, Mechanica allocates memory for other operations as needed. These other memory allocations can become large and, in combination, are often larger than the solram allocation. Even for computers with very large machine RAM, if you set the solram value too high, you may force the other memory areas used by Mechanica out of RAM and into swap space. • There will not be enough RAM for the operating system to do disk caching. Disk caching improves file system performance by holding file data in RAM for faster access. Setting solram to 0.5 times machine RAM is usually the best compromise between reducing the amount of disk I/O and leaving enough machine RAM for disk caching and for other data. By limiting the solram allocation to half the machine RAM or less, you greatly increase your chances of achieving optimal performance. If there is too much demand on machine RAM and swap space, system performance can be severely degraded. In this situation, decreasing solver RAM can increase overall system performance. 818 Structural and Thermal Simulation Select the Solver Mechanica uses one of two solvers in an analysis or design study. You can use either the direct solver or the iterative solver. The direct solver and the iterative solver are different methods by which Mechanica solves systems of simultaneous equations that arise from the geometric element model. Mechanica uses the direct solver by default because it usually requires less time, disk space, and/or memory than the iterative solver. You should use the direct solver in the following situations: • • • • if your model has thin features if your model did not converge using the iterative solver if your design study contains any analyses other than linear static, such as contact, modal, or transient thermal if your model is insufficiently constrained or you want to locate constraint problems in your model. For more information, see Insufficiently Constrained Models. If you want to try the iterative solver, you should monitor how much time and disk space your models take to run with each type of solver. In this way, you can determine which solver is best for which type of model. Note: For jobs running the direct solver, an elapsed time/CPU time ratio much greater than 4 may indicate a problem. For jobs running the iterative solver, a ratio much greater than 7 may indicate a problem. The iterative solver generally has a higher ratio of elapsed to CPU time because it does more I/O per calculation than the direct solver. Guidelines for Allocating Swap Space Use the following guidelines to plan where you should allocate swap space and how much you need: • • • Always configure swap space from a fast local disk. Using swap space from a remote computer can severely degrade performance. If possible, allocate swap space on disks that are not used for the Mechanica working directories. The amount of swap space you need is the maximum of the three values listed below: o 250 MB o 3 × your machine's RAM o 1.5 × maximum job memory (see below) You can estimate the job memory by performing these steps: 1. Start running the study. 2. After the first two passes, check the memory usage reported in the summary file at the end of each pass. 819 Structural and Thermal Simulation - Help Topic Collection 3. Use linear extrapolation to determine the amount of memory the run will need for the pass at which you expect the analysis to converge (for example, the maximum polynomial order you set for the analysis). The following example shows how to calculate swap space requirements for a machine that has 128 MB of RAM, and a model that you expect to converge after seven polynomial passes: pass 1 memory usage = 100 MB pass 2 memory usage = 150 MB estimated memory usage during pass 7 = 400 MB swap space = max (250 MB, 3 × 128 MB, 1.5 × 400 MB) = 600 MB Note: If you are using the iterative solver, the memory usage will jump by the solram value after the first iterative solver pass. For example, if you are running with –iter 2, then you should extrapolate after pass 3 ends or add solram to the estimate you extrapolated from passes 1 and 2. Your result will be the estimate of total memory use for the job. Guidelines for Setting Solram You set solver RAM allocation with a single parameter, called solram. • If the engine is the only memory-intensive application running on your computer, performance is usually best if you set solram equal to half of your machine RAM. For example, solram 120 is a good choice for a machine with 256 MB of RAM. Note that, for large models, Mechanica typically requires more RAM to handle your model's element data. Thus, you may need to set solram to less than 50% of your machine RAM to facilitate the run. If you are running other memory-intensive applications on your computer, decrease the solram allocation accordingly. For example, set solram to 0.25 times machine RAM if you are running two large applications at once. However, you often can run two large jobs faster one after another than if you try to run both jobs at once. • The optimal values also depend on other factors, such as what other processes are running on your machine, and the total amount of swap space available on your machine. If increasing RAM allocation causes a decrease in performance or a shortage of swap space, some performance gains might still be possible by increasing RAM allocation to above the default values, but below the recommended maximums. For solver RAM settings that exceed maximum or minimum ideal settings, refer to Strategy: If Solver RAM Is Too High and Strategy: If Solver RAM Is Too Low. 820 Structural and Thermal Simulation mech_extopt.out File Format The format of the mech_extopt.out file is as follows: objective_value_1 objective_value_2 objective_value_nobj limit_value_1 limit_value_2 limit_value_nlim This file contains nobj objective values and nlim limit values. –w working_dir1:working_dir2:... Specifies the location of the directory or directories in which the engine places temporary files during the run. Mechanica creates a subdirectory in the working directory called study.tmp (study is the name of the design study you are running), and deletes the directory at the end of the run. If you are running a large model or the disk space available on your computer is divided among several different directories, it may help to specify multiple working directories for your Mechanica job. You can specify the list of directories to be used as working directories from either the operating system command line or by editing the command line in a Mechanica batch file. You specify the list of working directories with the –w option, as follows (where dir1, dir2, and so forth, are your directory names): <install_dir>/bin/msengine... –w dir1:dir2:...:dirn If you specify multiple working directories, Mechanica sequentially places temporary files in the working directories as they reach capacity. When using multiple directories, be sure that you specify enough directories, and that the directories are large enough, to complete your run. If the directories are filled before the run completes, the run will terminate. You must order your directories in the following way to allow for how Mechanica places the files: • Large files, with .bas extensions, fill the directories from left to right. Therefore, specify the largest and fastest directories first in the directory list. The .bas files hold data such as the element stiffness and mass matrices and the factored global stiffness matrix. Mechanica fills the first directory you specify in the command line, followed by the second directory, and so on, until it reaches the dirn directory. For 821 Structural and Thermal Simulation - Help Topic Collection example, Mechanica uses the directory dir1 until it is filled, then dir2 is used, and so on. • Other files, such as .tmp files, go only into the last directory specified (dirn). The dirn directory must be big enough to hold all of the .tmp files. Be sure that the last directory can hold at least 50 MB of data. On very large models, this directory may need to hold as much as 5 or 6 GB. Again if you exceed the allotted directory space, the run will terminate, so be sure the last directory specified is sufficiently large. Input and output files (those with the extensions .mdb, .rpt, .stt, .err, or .pas) can go in the last directory specified, or in a separate directory from the –w list. For higher performance during pre- and post-processing, you can move the input and output files back to the fastest disk. The working directory is the same as the directory for temporary files you specify on the Run Settings dialog box. By default, Mechanica places this directory in the current directory. • Strategy: Running the Engine with Parallel Processing By default, Mechanica automatically selects the number of CPU's it will use during a run. For systems with one CPU, Mechanica always uses standard serial processing. For parallel processor machines, Mechanica attempts to use all CPUs on the machine. In certain situations, however, you may want to limit the number of CPUs the software can use. When making this decision, you need to balance the benefits of parallel processing against its limitations. The main advantage of parallel processing is that it can improve solution times. Parallel processing is most likely to improve a design study run time under the following conditions: • • • • Only a single user is using the computer at the time of the run. The computer is equipped with a fast disk, ample memory, and individual processors that are fast in and of themselves. The ratio of elapsed time to CPU time is close to a value of 1 with one CPU. Your model is large, solid, and blocky in shape. Even if these conditions are present, your elapsed run time might improve only slightly when you run the engine in parallel processing mode because parallel processing accelerates just a few phases of the overall solution process. The main disadvantage of parallel processing is that, if you are running other jobs at the same time as Mechanica, you can experience performance bottlenecks. Thus, unless you expect substantial gains from using all CPUs in your system for the engine or you have no other jobs planned for your system during the engine run, you may want to limit the number of CPUs dedicated to the engine. If you do not want to use all of the CPUs in your system for the engine job, you can set the environment variable MEC_NUM_THREADS to the anticipated number of idle 822 Structural and Thermal Simulation CPUs on the machine. For example, on a 4-CPU machine with one CPU-intensive job running in addition to the parallel job, set MEC_NUM_THREADS to 3. Note that Mechanica does not support parallel processing on the HP 32-bit platform. mech_extopt.in File Format The format of the mech_extopt.in file is as follows: ndp design_parameter_name_1 design_parameter_name_2 value_1 value_2 design_parameter_name_ndp nobj objective_name_1 objective_name_2 value_ndp analysis_name_1 analysis_name_2 objective_name_nobj nlim limit_name_1 limit_name_2 analysis_name_nobj analysis_name_1 analysis_name_2 limit_name_nlim where • • • analysis_name_nlim ndp is the number of design parameters nobj is the number of objectives (in Mechanica, there is just one single objective) nlim is the number of limits You must specify: • • the names and values of design parameters for objectives and limits, the names of measures defined in Mechanica, as well as the names of analyses in which these measures are used After P-Loop Pass This item appears only if you selected Iterative Solver. The iterative solver takes over from the direct solver after the pass you specify. You can enter a number from 1 to 9. The default of 2 is usually the best choice. The 823 Structural and Thermal Simulation - Help Topic Collection iterative solver does not always converge if you set this value to 1, and if you set the value to 3 or higher, your job might use excessive time, disk space, and/or memory. Maximum Number of Iterations This item appears only if you selected Iterative Solver. Use this item to specify the maximum number of iteration attempts the iterative solver can make during equation solving. The default is 3000. If the solver exceeds the number of iterations, Mechanica terminates the run. When you re-run the study, allow the block solver to complete one more pass by increasing the After P-Loop Pass number by 1. Reviewing Results Results for Native Mode About Results Use the Analysis>Results command to display the results of an analysis or design study. You view results by defining and displaying one or more result windows. For additional information on FEM mode results, see About FEM Results. The type of model and the items you select in your analysis or design study determine the quantities, locations, and displays that are available in results. Mechanica displays your results using the display format, combined with the quantity and location you select, to define your result window. Only certain combinations of quantities and displays are valid depending on the type of model, design study, or analysis you select for the result window. In addition, a selection in one category might not be valid with some items in the other categories. You can access results for both structural and thermal analyses after you select Analysis>Results. For information you should know about this command, see Before You Use the Results Command. If you have a model open when you select the Analysis>Results command, Mechanica handles this model differently depending on the mode you are using. This affects the state of your working model while you are looking at results. When you select the Analysis>Results command, Mechanica opens the Results user interface. Use this user interface to view, evaluate, and generate reports on analyses and design studies. You use the Result Window Definition dialog box to define and display your results. Once you have found a combination of results that work well for your application, you can save these results as a template using the File>Save As Template 824 Structural and Thermal Simulation command. After you have saved a template, you can recall that template using the Insert>Results Window from Template command. This command opens the Insert Result Windows from Template dialog box. You can also see results information in the summary file available through the Analysis>Mechanica Analyses/Studies command. This information gives you an idea of how well the model withstands the effects of the loads and constraints you apply in your design studies. Even if a design study run is still in progress or ended in error, you might still be able to display results. You can also get information about convergence problems from looking at results. For more information, see Troubleshoot Run Problems. Working with the Results User Interface When evaluating analysis and design study results, you work within the Results user interface. This user interface lets you view, evaluate, and manage results for your analyses and design studies. The Results user interface is independent of the Mechanica workspace. The way you open the Results user interface depends on the mode in which you are operating Mechanica. • • Native mode — Use the Analysis>Results command to open the Results user interface. FEM mode — Use the File>Open FEM Results command to open the .frd file that contains the FEM mesh and analysis results for the model on your screen. If you have performed an analysis of your model using the MSC/NASTRAN solver, in addition to being able to view FEM mesh and analysis results, you can also have a direct access to a NASTRAN results .xdb file. For information on different ways of loading results, see Using the Postprocessor in FEM Mode. The Results user interface incorporates a menu bar, toolbar, a set of basic functions, and a built-in workflow designed to facilitate results viewing. This workflow enables you to set up a variety of result views, evaluate individual results, and control scaling and visualization of multiple results so that you can easily compare one quantity of interest with another. Here is a step-by-step overview of what we suggest as your workflow: 1. Viewing results — You define result windows, display and hide them, and control how they appear on-screen and in your reports. 2. Evaluating results — You study the result windows you defined, probe specific areas of your model, and compare your findings for one model, design study, result quantity, or set of conditions with your findings for another. 3. Saving result windows — You save the set of result windows you created so that you can review or re-use them later. 4. Generating reports — You prepare printed and online reports for evaluation and presentation. 825 Structural and Thermal Simulation - Help Topic Collection While this sequence represents the most linear approach to reviewing results, you may find that you move back and forth through these steps as you refine the result views you have set up. Tip: You can perform many operations in the Results user interface against both single and multiple windows. For example, you can change backgrounds for multiple windows, rotate multiple result windows, and so forth. To select a single result window, move your cursor to the window and leftclick it. Mechanica highlights the window border in yellow. To select multiple result windows, press the SHIFT key and left-click each of the windows you want. If you select multiple result windows, Mechanica deactivates certain commands, such as Edit>Result Window and Export>VRML. Results User Interface Menu Bar The Results user interface features a menu bar at the top of the screen. You create and manage your results using the menus. To acquaint you with the organization of menu bar, here is an overview: • • • File menu — Provides commands that control such basic functions of the Results user interface as opening result sets, closing the interface, saving result definitions, and generating reports. Edit menu — Provides commands that modify result definitions, legends, cutting and capping planes, and annotations. View menu — Provides commands that control such aspects of results viewing as model position, shading, and overlays. You can also use this menu to display or hide result windows, start and stop animations, change or save the orientation of your model, and control the visual characteristics of result windows. Insert menu — Provides commands that define result windows, cutting planes, capping planes, and annotations. Info menu — Provides commands that probe your model for specific items of interest such as quantity maximums and minimums, exact quantities at model locations you select, and so forth. Also provides commands to display node IDs, element IDs, and node result values in FEM mode. Format menu — Provides commands that format result window values, color spectrums, and scales. Utilities menu — Provides commands that refine your results and let you perform result comparisons against the same scale. Window menu — Provides commands that let you manipulate your result windows within the Results user interface. • • • • • The Results user interface also includes a toolbar whose buttons give you fast access to the most frequently used commands on the menus just discussed. 826 Structural and Thermal Simulation Results User Interface Toolbar For fast access to some of the most commonly used commands on the menu bar, the Results user interface provides a toolbar with these buttons: Button Action/Name Open — Closes the current set of result definitions and opens a new one. Save — Saves the result windows currently available in the Results user interface. Save As — Saves the result windows currently available in the Results user interface to a .rwd file you specify. Print — Prints all currently displayed result windows. Insert — Lets you create a result window definition. Edit — Lets you edit a result window definition. Copy — Lets you copy result window definitions. Delete — Deletes the selected result windows. Display — Lets you pick which result windows you want to display. Hide — Hides the selected result windows. Repaint — Repaints all currently displayed result windows. Zoom In — Zooms in on the model in the selected result window. Zoom Out — Zooms out from the model in the selected result window. Refit — Refits the model in the selected result window. Default — Returns the model to the default view. Saved Views — Repositions your model to the orientation of the saved view that you select from the list. Start Animation — Starts an animation of the model in the selected result window. 827 Structural and Thermal Simulation - Help Topic Collection Stop Animation — Stops an animation. Step Animation Backward — Steps backward through an animation frame by frame. Step Animation Forward — Steps forward through an animation frame by frame. Animation Playback Speed Control — Speeds up or slows down all currently displayed animations. Basic Functions for the Results User Interface The Results user interface provides a set of three commands that let you perform basic, low-level functions like opening a set of result windows or closing the Results user interface. These activities are generally preliminary to setting up a results session. You can find all three basic commands on the File menu. Here is an overview of the basic commands: • • • New — Use this command to start a new results session. Open — Use this command to open an existing set of result definitions and view the associated result windows. Exit Results — Use this command to close your results session. Each of these commands clears the current contents of the Results user interface. When you select any of these commands, Mechanica prompts you to save any result windows currently defined for the results session. If you want to save the result windows, reply Yes. Mechanica displays the Save Results Window dialog box. Use this dialog box to create a new .rwd file or save the result windows to an existing .rwd file. Defining and Viewing Results Viewing Results To view results, you perform three activities—define result windows, display result windows, and control the general appearance of the result windows you define. The Results user interface features easy, direct methods of defining result windows as well as a variety of view controls. Here is an overview of the method you use to view results: • Define result windows — You define result windows through the Insert>Result Window command or by clicking the Insert button on the toolbar. Mechanica opens the Result Window Definition dialog box. Use the dialog box to select the design studies, display types, quantities, and locations you are interested in. 828 Structural and Thermal Simulation If you want to add or compare the result windows you define to an existing set of result window definitions, use the Insert>Result Window From File command in concert with Insert>Result Definition. You may find that you can define result windows more quickly by copying them. • Display and hide result windows — You display result windows through the View>Display command or by clicking the Display button on the toolbar. When you select this command, the Display Result Window dialog box appears, enabling you to select and deselect various result windows to display. You hide windows by clicking the Hide button. You can hide a single window or multiple windows. You will find this particularly handy as you prepare to generate reports. You can also make a selected result window occupy the entire Result user interface work area through the Windows>Full Screen command. This command expands the current window to occupy the work area. • Control result window appearance — You control how result windows appear on-screen through commands on the View and Format menus. You can also perform some of these activities through toolbar buttons. When you set up your result windows as you want, you can begin to evaluate and compare results. Once you have studied your result windows, you may also want to alter, copy, or delete some of them. Defining Result Windows Result Window Definition Dialog Box Use the Result Window Definition dialog box to define the contents of a result window. Valid quantity and display combinations depend on whether you are working in native mode or FEM mode as well as on the type of model, design study, and analyses you select for the result window. In addition, a selection in one category may not be valid with some items in the other categories. When you select Analysis>Results, the Result Window Definition dialog box appears. In FEM mode, you can use the Results command when you want to load results directly from a NASTRAN .xdb file. To load Mechanica FEM mesh and results file, select File>Open FEM Results. The Result Window Definition dialog box consists of these main areas: • Name and title area — Enter a name and title for the result window. The name you enter appears in the list on the Display Result Window dialog 829 Structural and Thermal Simulation - Help Topic Collection • • • • • box. The title appears at the bottom center of the result window. You can change the name and title at any time. Study Selection — Select the design study or analysis that the software will use to generate the result display. You can also use this area to select modes, load sets, time steps, and load steps if these are part of the analysis or design study you select. Display Type — Select the type of display for your result window. Quantity tab — Select the quantity for your result window. After you select a quantity from the first option menu, you may see additional option menus or buttons you can use to complete selecting a quantity. Display Options tab — Select various options for displaying your results. The available options depend on the display type you choose. Display Location tab — Select specific locations on your model to display in the results window. The Result Window Definition dialog box provides a top-down approach to defining the result window. As you make selections at the top of the dialog box, different choices become active or inactive as you move down from one area to another area. The type of design study you select affects the available display types and quantities that are available. When you select a display type, that determines the quantities and display options that are available. The dialog box lets you select only valid combinations. For strategies on choosing among the various result window types, see Reviewing the Results. You can display result windows using these methods: • • If you are still working with the Result Window Definition dialog box, click the OK And Show button. If you have finished defining results and are working in the Results user interface, click the Display button on the toolbar and select result windows from the Display Result Window dialog box. As an alternative, you can use View>Display. Study Selection Area Use the Study Selection area of the Result Window Definition dialog box to select the design study/analysis that the software uses to generate the result display. The Study Selection area displays the following: • Design Study — Select the design study for which you want to display the results. The design study name appears in the display-only text box to the right of the button. In FEM mode, if you are loading results directly from a NASTRAN .xdb file, use the button to open the Load NASTRAN XDB dialog box. On this dialog box, you need to select the .xdb file from which you want the software to read the results. Analysis — Select an analysis that is part of the design study you select. Step/Combination — Select a subset of design study results. • • 830 Structural and Thermal Simulation Step/Combination Selection The step/combination selection table displays different columns depending on the design study you select. You can select one or more subsets to include in the result display. If there is only one subset for a design study, the subset is selected by default and you cannot clear it. The possible subsets in the step/combination selection table are: • Load Set/Mode — When you select a static, modal, or steady-state thermal design study, the table lists the load sets or modes used in the study. You can select one or more load set/mode combinations and provide a scaling factor for each load set/mode combination you select. The default scaling factor is 1.0. Note that there are special considerations if you use scaling with centrifugal loads. Time/Frequency/Load Step — When you select a static large deformation, dynamic frequency, dynamic time, or transient thermal analysis, the table lists the time, frequency, or load steps present in the design study. These are the user-defined steps you defined when you created the analysis. You can select one step from the list. Mode (Buckling/Prestress Modal) — When you select a buckling or prestress modal design study, the table lists the mode and buckling load factor present in the design study. You can select one mode or buckling load factor from the list. • • Display Type Area Use this area to define the way you want Mechanica to display your results. The design study or quantity you select can make one or more of the display types unavailable on the option menu. These items can appear on the Display Type option menu: • Fringe — Displays a graphical representation of your model, showing the measurements of the quantity you specify as filled color regions—each corresponding to a numeric range calculated by the analysis or design study. You can also create a contour plot using this display type. Vectors — Displays a graphical representation of your model, showing the measurements and directions of the quantity you specify as colored vector arrows. This display type is not available in FEM mode. Graph — Displays a graph of your model's behavior. Graphs display the relationship between a quantity and the graph location, such as P-loop pass, curve or edge, time, or frequency. Model — Displays your model's geometry in its original or deformed state. Model representations are useful if you want to show a simple animation of how your model deforms or if you want to show the optimized shape of your model. This display type is not available for Thermal. You can query linearized stresses for your model by selecting Model as the display type, Stress as the quantity, and Linearized as the component. 831 • • • Structural and Thermal Simulation - Help Topic Collection When the result window displays, select Linearized Stress Query from the Info menu. Quantity Tab Use the Quantity tab on the Result Window Definition dialog box to select a quantity for your result window display. The choices that appear on the Quantity tab depend on the design study and display type you select. The items that are available change immediately if you change the design study or display type. These are the items that can appear on the Quantity tab: • Quantity — Select the quantity you want to display in the result window. The menu displays only the quantities that are valid for the design study and display type you choose. The quantity you select determines which of the remaining items appears on the Quantity tab. Secondary Quantity Option Menu — Select a secondary quantity to display in the result window. This item appears if you select Fatigue, Reaction, Shell Resultant, or Beam Resultant from the Quantity option menu. Component — Select the component you want to display in the result window. The menu displays only components that are valid for the quantity you select from the Quantity menu, and only appears for certain quantities. Relative To — Select the reference for a directional component. This item appears only if you select a directional component. Graph Location — Select the type of location you want to use for your graph results display. This area appears only if you select a display type of Graph. • • • • The following additional items are available depending on the quantity you select and whether beams or shells are present in the model. These items do not appear in FEM mode. • • Include Contribution from Beams — Select the beam contributions to include in the result window definition. This area appears only if there are beams in the model. Include Contribution from Shells — Select the shell contributions to include in the result window definition. This area appears only if there are shells in the model. In addition to using the Quantity tab to define your basic result quantity, you use the Display Options tab and Display Location tab to further refine the result window display. Display Options Tab Use the Display Options tab on the Result Window Definition dialog box to determine the appearance of your results window display. 832 Structural and Thermal Simulation Selecting one of these display types determines the options available on the Display Options tab: • • • • Fringe (includes contour) Vectors (not available for FEM mode) Graph Model (not available for thermal mode) If you select a display type and then select a design study or quantity that is not compatible with that display type, Mechanica removes the display type from the option menu and displays only the valid display types for that design study and quantity combination. Display Location Tab Use the Display Location tab on the Result Window Definition dialog box to select specific locations to display in your result window. These items appear on the Display Location tab: • Display Location — Select the type of location you want to display in your result window. The options available on this menu vary depending on the design study, display type, and quantity you select. These items can appear on the menu: o All — Display all locations in the result window. This is the default value. o Beams — Display beams in the result window. o Curves — Display curves in the result window. o Surfaces — Display surfaces in the result window. o Volumes — Display volumes in the result window. o Components/Layers — Display specific components or layers in the result window. Select the Use All check box to display all Beams, all Curves, all Surfaces, all Volumes, or all Components/Layers in the result display window. • Location Selector Arrow — Use the selector arrow to select the specific entity on your model that you want to display in the results window. You can select more than one entity. If you accept the default All, the selector arrow is unavailable. To Define a Result Window 1. From the Insert menu, select Result Window or click on the Results user interface toolbar. The Result Window Definition dialog box appears. (Result Window) 833 Structural and Thermal Simulation - Help Topic Collection 2. In the Name text box, enter a name to identify the result window so that you can show or hide the window during your results session, or use the default. 3. In the Title text box, enter the title that you want to display at the bottom center of the result window. . 4. Select the design study for which you want to display results by clicking 5. If the design study has more than one analysis, select an analysis from the Analysis option menu. 6. If Mechanica displays a step/combination table below the Design Study and Analysis option menus, select a load set, mode, time step, or frequency from the table. 7. Select one of these display types from the Display Type option menu: o Fringe o Vectors o Graph o Model 8. Select a quantity from the Quantity option menu on the Quantity tab. 9. Select the Display Options tab and choose among the display options to determine the appearance and behavior of your model in the result window. 10. Select the Display Location tab and choose a location from the option menu. If you want to use all entities of a certain location type, select the Use All check box. To select a single entity, click the selector arrow. 11. To display the result window, click OK And Show. To close the dialog box without displaying the result window, click OK. To Display a Result Window 1. Select View>Display or click (Display) on the toolbar. Mechanica displays the Display Result Window dialog box. 2. If you want to display one or more result windows in the result window list, select the desired result windows. Mechanica highlights each selection you make. 3. If you want to display all result windows in the list, click Tip: If you need to deselect all result windows, click 4. Click OK. (Select All). (Deselect All). Annotating Result Windows Use the Insert>Annotation menu option to create or edit one or more annotations for a result window. You can use annotations to create notes about the results or the model, to point out specific results or features on your model, to make your result reports more meaningful to others, and so on. 834 Structural and Thermal Simulation You can customize annotations in many ways. If you want to include text, you can surround the text with a border and a background color. You can have leader lines, with or without arrows, that point to one or more places on your model. Using the mouse sketch tools, you can be very creative by adding shapes or drawings to your annotation. Any part of the annotation can have its own unique color and you can place it anywhere on the active window. When you select the Insert>Annotation menu option, the Note dialog box appears with the following options: • • • Text — Change the font, the font size, and the font color. Note Location — Select the location where you want the annotation text to appear. The annotation appears to the right of the point you select. Leader — Create one or more leaders for the annotation. You select a point on your model and Mechanica draws the leader line from the annotation to that point. Use the arrow button to put an arrow at the end of the line. If you reorient the model, the end of the leader line that is on the model moves with the model. Display Leader Arrow — Display an arrow at the end of the leader. Mouse Sketch — Create a circle, square, or multiple line shape. Style — Open the Note Style dialog box. • • • Use the Preview button at any time to apply any changes you have made without closing the dialog box. Evaluating Results The way you evaluate results depends on the type of result window you are working with. For example, if you are examining fringe plots, you are likely to be interested in the location of the quantity maximum, the value of the quantity at specific locations, how one quantity compares with another, and so forth. If you are looking at animations, you are likely to be interested in how the model deforms, the pattern of deformation at different steps, how behavior in one mode compares with behavior in another, and so forth. Here is an overview of methods and tools you can use to evaluate the different types of Mechanica results: • Fringe, contour, and vector plots — You perform three basic activities depending on how deeply you need to examine the model for the result quantity: o Adjust the legend, perform comparisons with other result windows, and, if necessary, shade or unshade your model. o Probe your model for specific information like maximum and minimum locations or how the interior of your model responded during analysis. o In FEM mode, display information about the element ID's, node ID's, and values of the result quantity at each node. Graphs — You perform two basic activities depending on how much detail you need on the quantity: o Adjust the graph, perform comparisons with other result windows. 835 • Structural and Thermal Simulation - Help Topic Collection • Probe the graph to obtain more exact values for specific segments of the graph or points on the graph. Animations — You can start, stop, and control stepping and speed for the animation. You can also perform comparisons with the original model shape as well as with other animations. o Once you have evaluated your results, you should save the result definitions for later use. At this point, you can also generate reports on your results. After you have studied your result windows, you may also find that you want to alter, copy, or delete some of them. Loading Result Windows To preserve your work, you typically save a set of result windows you have defined to a named .rwd file so you can use the windows later. In future sessions, you can load this file, review the result windows, modify the definitions, add new result windows to the file, or delete windows. You can load existing result windows in two ways: • File>Open — Use to start a new result session with the result windows active and displayed. This command is convenient if you have just started your results session or if you are finished looking at any result windows you may have created in the current session. Before executing this command, Mechanica checks to see if any you have changed any of the result windows in the current session. If so, the software asks you whether you want to save the result windows. If you respond Yes, the software executes a Save command before starting the new result session. • Insert>Results Window from File — Use to load existing result windows into the current session and add them to the list of windows you can view. This command is handy when you want to preserve the result windows you created during the current session, but also want to see the windows saved from an earlier session. Mechanica ensures that you do not overwrite current result windows by giving you the opportunity to rename any result windows that have duplicate names. When you select either of these commands, a dialog box appears. Select the name of the file you want to load or enter it without the .rwd extension Mechanica gave the file. To Load a Result Window This procedure assumes you are in the Insert menu. There is an alternate method of loading result windows using the File>Load command. However, the effect on the existing session is different. 836 Structural and Thermal Simulation 1. Select Insert>Result Window From File. The Load Result Windows dialog box appears. 2. Select the name of the file you want to load or enter it without the .rwd extension Mechanica gave the file. 3. If you load a result window with the same name as a result window already on the dialog box, the New Result Window Name dialog box appears. Enter a new name for the result window definition you want to load. 4. Click OK. If you have not yet created or loaded any other result windows in the results session, the Results user interface title bar displays the name of the .rwd file you selected in step 2. Saving Results After you create one or more result windows, you can save these windows to a file for later use. Mechanica saves result windows in .rwd files. Saving result windows makes it easier to restore and add to your work. You can also use result windows as templates for developing result windows for multiple models. Use one of these commands on the File menu to save your result definitions: • Save — Use to save the current set of result definitions and associated views in a single .rwd file. If you defined the set of result windows in the current session and this is the first time you have saved them, Mechanica saves the windows to a file named Untitled.rwd. If the result windows displayed were saved to a named .rwd file in the past, Mechanica saves them to the named file. Save As — Use to save the current set of result definitions and associated views as a named .rwd file. When you click Save As, Mechanica displays the Save Result Windows dialog box. Use this dialog box to choose a directory and name the file. Do not include the .rwd extension in the file name you enter—Mechanica appends this automatically. When you use Save As to create a named .rwd file, the name of the .rwd file appears in the Results user interface title bar whenever you load the named .rwd file using Insert>Results Window From File as the first activity in your results session. • Save As Template — Use to save the current result window definition and some of the result window attributes as a named template as a .rwt file. When you click Save As Template, Mechanica displays the Save Results Template dialog box. Use this dialog box to choose a directory and name the file. Do not include the .rwt extension in the file name you enter—Mechanica appends this automatically. You can optionally store the legend values, model orientation, annotations, and deformed scale for the result window as part of the template. Once you create a result window definition as a template, you can create other result windows 837 • Structural and Thermal Simulation - Help Topic Collection from the template by selecting the Insert>Results Window From Template command. Regardless of which approach you use, be aware that Mechanica includes paths for the study directories referenced by the result windows in the .rwd file. Mechanica uses an absolute path when it writes this information to the .rwd file, but you can instruct Mechanica to use a relative path instead through the sim_pp_path_absolute config.pro option. You can retrieve a set of saved windows using one of the load commands. Generating Reports Once you define and display result windows, you can generate reports that capture the vital points of your analyses and design studies. Mechanica provides you with the ability to print reports in a wide variety of print formats, to output reports as HTML, and to generate VRML reports. For graphs, you can generate specialized graph reports so you can study the graph sampling points in depth. Use these commands located on the File menu to generate reports: • • Print — Use to print a selected result window to a printer or to a file. Export — Use to generate each of the following report types, selectable from the associated submenu: o Image — Use to generate printed images. This command is identical to File>Print. o Direct VRML — Use to export a single fringe plot at a time in VRML format. o HTML Report — Use to export result windows to an HTML file for web viewing. o Graph Report — Use to export a graph report file for a single, selected graph. The output file is a text file. o Excel — Use to export a single graph for viewing in Microsoft Excel. The output file is a .xls file. o MPEG — Use to export a single animated result window to an MPEG file. When preparing to generate reports, you may want to pay particular attention to the aesthetics of the result windows you are printing or exporting. You should also consider formatting the result windows to emphasize the aspects of the result you want to focus on when you share the information with others. For example, blended or dark background colors may make it difficult to read some of the information, depending on the quality of your printer. You may want to eliminate excess text from the result window by using Format>Result Window and turning off labels. You may want to work with the Format Legend dialog box to ensure that you are using the best color scale to reflect what takes place in a fringe plot. You can highlight parts of your results and add information using annotations. 838 Structural and Thermal Simulation To Define an Acceleration Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Acceleration from the Quantity option menu on the Quantity tab. 2. Select a component from the Component menu. 3. If you select a directional component, select an option from the Relative To option menu. 4. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Animate a Results Display 1. Select Animate. The Auto Start check box, the animation buttons, and the Frames entry box become available. 2. If you want to start the animation as soon as the result window opens, select Auto Start. 3. If you want the animation to automatically run in reverse after it runs forward, click . 4. If you want the animation to automatically repeat over and over from the beginning, click . 5. If you want the animation to automatically alternate between forward and reverse, click . 6. Enter the number of frames in the animation or accept the default. When you display or load a result window with an animation, you can use the slider on the toolbar to speed up or slow down the animation. To Specify a Result Window Quantity Select a quantity from this list to access the procedure for creating a result window display for the quantity. These procedures assume that you have completed the appropriate preliminary steps in To Define a Result Window: • • • • • • • • • Acceleration Beam Resultant Contact Pressure Displacement Failure Index Fatigue Flux Measure P-Level • • • • • • • • • Rotation Velocity Shear & Moment Shell Resultant Strain Strain Energy Stress Temp Gradient Temperature Thermal Strain (FEM only) 839 Structural and Thermal Simulation - Help Topic Collection • • • • Reaction Reactions at Point Constraints Rotation Rotation Acceleration • • Thermal Strain Energy (FEM only) Velocity Note: The P-Level quantity does not require a procedure. For information on this quantity, see P-Level Results Quantity. To Specify Result Window Display Options The display options available on the Display Options tab vary depending on the display type you choose from the Display Type option menu. Select a display type from the following list to access the procedure for defining the display options for the quantity you selected. These procedures assume that you have completed the appropriate preliminary steps in To Define a Result Window: • • • • • Fringe Contour Vectors Graph Model To Define a Displacement Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Displacement from the Quantity option menu on the Quantity tab. 2. If you are working with dynamic analysis results in FEM mode, select Amplitude or Phase. 3. Select a component from the Component menu. 4. If you select a directional component, select an option from the Relative To option menu. 5. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Deformed Results Display This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. To display your model with deformations in the result window, select Deformed. The Overlay Undeformed and Transparent Overlay check boxes become available. 840 Structural and Thermal Simulation 2. To superimpose the undeformed model over the results model, select Overlay Undeformed. 3. To display the overlay as a transparent filled representation of the model, select Transparent Overlay. 4. In the Scaling text box, enter a positive real number. If you do not want to display the scaling value as a percentage, clear the Percent (%) check box. To Define a Contour Results Display This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Enter the number of legend levels to display or accept the default. 2. Select Contour. The Label Contours and IsoSurfaces check boxes become available. 3. To display labels along the contour lines, select Label Contours. 4. To show isosurfaces in your model, select IsoSurfaces. 5. To include displacements or deformation when you display your model, select Deformed. 6. To display the edges of the elements in your model, select Show Element Edges. 7. To animate your results, select Animate. To Define a Contact Pressure Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Contact Pressure from the Quantity option menu on the Quantity tab. 2. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Beam Resultant Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select tab. 2. Select 3. Select 4. Select Beam Resultant from the Quantity option menu on the Quantity a secondary quantity from the secondary quantity option menu. a component from the Component menu. an option from the Relative To option menu. 841 Structural and Thermal Simulation - Help Topic Collection To Define a Rotation Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Rotation from the Quantity option menu on the Quantity tab. 2. If you are working with dynamic analysis results in FEM mode, select Amplitude or Phase. 3. Select a component from the Component menu. 4. If you select a directional component, select an option from the Relative To option menu. 5. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Rotation Velocity Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Rotation Velocity from the Quantity option menu on the Quantity tab. 2. Select a component from the Component menu. 3. If you select a directional component, select an option from the Relative To option menu. 4. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Rotation Acceleration Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Rotation Acceleration from the Quantity option menu on the Quantity tab. 2. Select a component from the Component menu. 3. If you select a directional component, select an option from the Relative To option menu. 4. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. 842 Structural and Thermal Simulation To Define a Shear & Moment Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Shear & Moment from the Quantity option menu on the Quantity tab. Shear & Moment is only available on the Quantity menu if you select Graph from the Display Type menu. 2. Use the check boxes and option menu under Beam to select beam components. 3. Select beams or curves from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Strain Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Strain from the Quantity option menu on the Quantity tab. 2. Select a component from the Component menu. 3. If you select a directional component, select an option from the Relative To option menu. 4. If beams are present in the design study, make the appropriate selections in the Include Contribution From Beams area. 5. If shells are present in the design study, make the appropriate selections in the Include Contribution From Shells area. 6. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Results Display Location This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select the Display Location tab. 2. Select the location you want to display in the result window from the option menu. One or more the following options may appear: o o o o o o All Beams Curves Surfaces Volumes Components/Layers 3. Click the selector arrow to select one or more entities on your model of the location type you selected. 843 Structural and Thermal Simulation - Help Topic Collection To Define a Vectors Results Display This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select the Display Options tab. 2. Select one of these items: o Wireframe Vectors o Shaded Vectors 3. Enter the number of legend levels to display or accept the default. 4. Enter the maximum relative length of the vectors to be drawn in the result window. 5. To include displacements or deformation when you display your model, select Deformed. 6. To display the edges of the elements in your model, select Show Element Edges. 7. To animate your results, select Animate. To Define a Flux or Temp Gradient Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select either Flux or Temp Gradient from the Quantity option menu on the Quantity tab. 2. Select a component from the Component menu. 3. If you select a directional component, select an option from the Relative To option menu. 4. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Reactions at Point Constraints Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window and that you chose Model as the Display Type. 1. Select Reactions at Point Constraints from the Quantity option menu on the Quantity tab. 2. Select a secondary quantity from the secondary quantity option menu. 3. Select a component from the Component menu. 844 Structural and Thermal Simulation To Define a Reaction Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window and that you chose Graph from the Display Type menu. 1. 2. 3. 4. 5. Select Reaction from the Quantity option menu on the Quantity tab. Select a secondary quantity from the secondary quantity option menu. Select a component from the Component menu. Select an option from the Relative To option menu. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Model Results Display This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select the Display Options tab. 2. To shade the surfaces of your model, select Shade Surfaces. 3. To include displacements or deformation when you display your model, select Deformed. 4. To display the edges of the elements in your model, select Show Element Edges. 5. To animate your results, select Animate. To Define a Measure Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Measure from the Quantity option menu on the Quantity tab. Measure is only available on the Quantity menu if you select Graph from the Display Type menu. The Select A Measure dialog box appears. 2. Select a measure from the Pre-Defined or User-Defined list. 3. Click Accept. 4. Select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. 845 Structural and Thermal Simulation - Help Topic Collection To Define a Graph Results Display This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Graph from the Display Type option menu. Mechanica deactivates the Display Options tab and the Display Locations tabs. 2. Select the quantity you want to graph from the Quantity option menu on the Quantity tab. 3. Select an option from the Graph Location option menu, then use the selector arrow to select one or more locations from your model. Once you click the OK button or the OK And Show button, you can control the appearance of your graph from the Results user interface. To Define a Fringe Results Display This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. This procedure is for a basic fringe plot results display. To create a contour plot results display, see the contour procedure. 1. Select the Display Options tab. 2. To display the fringe in continuous tones rather than discrete colors, select Continuous Tone. 3. Enter the number of legend levels to display or accept the default. 4. To include displacements or deformation when you display your model, select Deformed. 5. To display the edges of the elements in your model, select Show Element Edges. 6. To animate your results, select Animate. To Define a Shell Resultant Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. 2. 3. 4. Select Shell Resultant from the Quantity option menu on the Quantity tab. Select a secondary quantity from the secondary quantity option menu. Select a component from the Component menu. If you select a directional component, select an option from the Relative To option menu. 846 Structural and Thermal Simulation To Define a Failure Index Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Failure Index from the Quantity option menu on the Quantity tab. 2. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Velocity Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Velocity from the Quantity option menu on the Quantity tab. 2. Select a component from the Component menu. 3. If you select a directional component, select an option from the Relative To option menu. 4. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Thermal Strain Quantity Mechanica supports the Thermal Strain quantity for FEM mode only. This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Thermal Strain from the Quantity option menu on the Quantity tab. 2. Select a component from the Component menu. 3. If you select a directional component, select an option from the Relative To option menu. 4. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Thermal Strain Energy Quantity Mechanica supports the Thermal Strain Energy quantity for FEM mode only. This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Thermal Strain Energy from the Quantity option menu on the Quantity tab. 2. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. 847 Structural and Thermal Simulation - Help Topic Collection To Define a Temperature Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Temperature from the Quantity option menu on the Quantity tab. 2. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Strain Energy Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Strain Energy from the Quantity option menu on the Quantity tab. 2. If beams are present in the design study, make the appropriate selections in the Include Contribution From Beams area. 3. If shells are present in the design study, make the appropriate selections in the Include Contribution From Shells area. 4. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Stress Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Stress from the Quantity option menu on the Quantity tab. 2. Select a component from the Component menu. 3. If you select a directional component, select an option from the Relative To option menu. 4. If beams are present in the design study, make the appropriate selections in the Include Contribution From Beams area. 5. If shells are present in the design study, make the appropriate selections in the Include Contribution From Shells area. 6. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. To Define a Fatigue Quantity This procedure assumes that you have completed the appropriate preliminary steps in To Define a Result Window. 1. Select Fatigue from the Quantity option menu on the Quantity tab. 2. Select a component from the Component menu. 848 Structural and Thermal Simulation 3. If you select Graph from the Display Type option menu, select an option from the Graph Location option menu, then use the selector arrow to select the location from your model. Components for Fatigue When you select Fatigue from the Quantity option menu, the Component option menu displays the components specific to this quantity. Use this option menu to further refine your quantity definition. The choices available on this menu depend on the design study, display type, and quantity combination you select. These options appear on the Component menu if you select Fatigue: • • Log Life — Shows the estimated number of cycles until your model breaks. Because of the exponential nature of fatigue, it is useful to express life as a logarithm. Log Damage — Shows the ratio between accumulated fatigue cycles and the total number of cycles to failure. A value greater than unity indicates failure. A value of 0.5, for example, represents a loss of 50% in the useful life of the model. Because of the exponential nature of fatigue, it is useful to express the damage ratio as a logarithm. Factor of Safety — Shows the permissible factor of safety on the input load. When the fatigue life calculated for your model is greater than the target design life, the software carries out a back calculation to determine a permissible factor of safety on the input load. This represents the extent to which the amplitude of the load can be increased without compromising the target design life. If you want the software to calculate the factor of safety, select the check box in the Output area at the bottom of the Fatigue Analysis Definition dialog box. • Confidence of Life — Shows the ratio between the calculated life and the target design life. Because of the statistical nature of fatigue, the greater the confidence the better. Values below unity indicate failure. Values greater than 3.0 usually reflect an adequate confidence of achieving the desired target life. You can display Confidence Of Life results in a tri-colored fringe plot to give an overall view of where the model will break first and where the model will last for a greater number of cycles. Red signifies from 0 cycles to the number of cycles entered for Desired Endurance (considered 1x) on the analysis dialog box. Yellow signifies from 1x to 3x (considered the marginal life). Green signifies any number of cycles over the marginal life (3x). The default is 3x, but you can change this by changing the value of sim_fatigue_safety_margin in the configuration file. For fatigue analyses, Mechanica reports results for all surfaces on your model, but not the interior of your model. • 849 Structural and Thermal Simulation - Help Topic Collection Reviewing the Results You can review many combinations of quantities, locations, and display types for a design study. For a standard design study, you should typically start by defining result windows that contain the following combinations. If possible, always try to make a rough calculation by hand to get an order of magnitude validation of your results. • Convergence Graph — To create a convergence graph for analyses that use multi-pass convergence, select Graph as the display type, Measure as the quantity, and P-Pass as the location. You can define a graph of the value of any measure calculated for the analysis at each p-pass. Deformed Model — To create a deformed result display for static and modal analyses, select Model as the display type, Displacement as the quantity, Magnitude as the component, and All as the location. Select Deformed from the Common Settings section of the Display Options tab. You can also overlay an undeformed or transparent version of the model and animate the displacement to verify that the model is deforming the way you expect it to. Change the scale factor to make the deformed shape look more reasonable, if necessary. To examine the magnitude of the displacements, define another result window using a display type of Fringe or Vectors with the same quantity and location. • Stress — To create a result display for static analyses that shows the distribution and magnitude of stresses, select Fringe as the display type, Max Principal, von Mises, or Beam Total as the component, and All as the location. You can determine whether the distribution and magnitude of stress look reasonable. Locations where the stresses differ greatly across element boundaries are areas where altering the mesh can facilitate convergence. • Temperature — To create a result display that shows temperature distribution for thermal analyses, select Fringe as the display type, Temperature as the quantity, and All as the location. Then select Contour from the Common Settings section of the Display Options tab. You can determine whether the temperature distribution looks reasonable. Flux — To create a flux distribution and magnitude result display for thermal analyses, select Fringe or Vectors as the display type, Flux as the quantity, Magnitude as the component, and All as the location. You can determine whether the distribution and magnitude of flux look reasonable. • • 850 Structural and Thermal Simulation Component and Layer Visibility in Results Use the Components/Layers option on the Display Location tab to show, hide, or isolate specific components or layers of a model in the result window. You can use the layers you created in Pro/ENGINEER or Mechanica. Only layers containing simulation beams or shells are available for display in results. When you select the Components/Layers option, the Component And Layer Visibility dialog box appears. This dialog box contains the following: • Component and Layer Tree — Use to select the components or layers you want to display, hide, or isolate in the results window. If the model is an assembly, the Layer Tree displays the components of an assembly and any layers containing beam or shell definitions that exist in the model. If the model is a part, the Component and Layer Tree displays only layers that contain beam or shell definitions. Buttons — Use to determine which components or layers are visible in the results window. • In general, it is better to use Isolate to visualize the parts and layers of interest in the result window display. Use Blank to exclude a few items from the result window display. If you define assembly-level shell/beam definitions on part-level geometry, blanking the part also blanks the shell/beam definitions unless they are in an isolated layer. For more detailed information on layers, search the Basic Pro/ENGINEER functional area in the Pro/ENGINEER Help Center. Results Relative to Ply Orientation When you select Ply Orientation from the Relative To option menu, Mechanica displays a spin box that allows you to select the ply to use in the result window display. To display results relative to the ply orientation, you need: • • • to have a shell with laminate layup properties to have selected Ply Stresses under Calculate on the Output tab of the Static Analysis Definition dialog box to use Stress or Strain as the result window quantity Note: Mechanica allows you to select only ply locations that are valid for the quantity you choose. 851 Structural and Thermal Simulation - Help Topic Collection Component When you define your result window display, you can select a component to further define the quantity you choose. The items available on the Component option menu depend on the quantity you choose from the Quantity option menu. For more information on the components available for each quantity, select the quantity from this list: • • • • • • • • • • • • • • • • • • Acceleration Beam Bending Beam Resultant Beam Tension Beam Torsion Beam Total Displacement Fatigue Flux Reaction Rotation Rotation Acceleration Rotation Velocity Shear & Moment Shell Resultant Stress, Strain, and Thermal Strain Temp Gradient Velocity Recovery Points for Beam Results The Recovery Point menu option appears in the Include Contribution From Beams area of the Quantity tab when you select the Von Mises, Max Principal, Mid Principal, Min Principal, Maximum Shear Stress, Beam Bending, or Beam Total component of the Stress quantity. Note that in FEM mode, this option appears only when you used the NASTRAN solver to run your analysis. In this case, your only selection from the Component menu can be Beam Total. Use the Recovery Point option to direct Mechanica to report beam stresses at a specific location on the beam section. After you select this option, you need to make additional selections from the menus that appear: • Select a beam section from the list of beam sections available in your model. Mechanica lists every beam section you created while defining your beams. The list contains shape names, such as Square, Rectangle, and so on, for standard cross-sections, and section names, such as my_beam_section, for sketched and general cross-sections. After you select a shape or section name, Mechanica displays a graphic showing the locations of the recovery points on the beam section. 852 Structural and Thermal Simulation If you run in FEM mode with the NASTRAN solver, you may not always be able to see the cross-section names and the graphic displaying the recovery points. If you open the .xdb file alone in a session without the model file or .frd file active in the session, the list displays only default names, with numbers corresponding to the PBEAM property card IDs in the .xdb or .nas file. For example, Section1 corresponds to PBEAM ID 1, Section2 corresponds to PBEAM ID 2, and so on. For all beam sections, regardless of the type, Mechanica displays the graphic corresponding to a general beam section. If you view results from the .frd file in FEM, the beam section names and the graphic displayed are the same as in native mode. Also in FEM mode, if your beam has different section types at the start and end, no section name will be included in the list. You cannot view recovery point results for this type of beam. However, if the sections at the start and end of the beam are of the same type, but of different dimensions, you can view results. • Select a recovery point from the list of available points. The list contains the maximum number of recovery points allowed for the type of beam section that you selected. For example, solid circle sections have nine recovery points, L-sections have eight recovery points, while sketched sections have the number of points you specified when sketching a section. In FEM mode, the number of points is always four. Stress Notes If your model is made up of brick, wedge, or tetrahedral elements that have the same isotropic materials, Mechanica uses a different calculation that increases the rate of stress convergence, yielding more accurate stress results at a lower polynomial order. Mechanica does not use this algorithm to compute the stresses in models made up of: • • • non-isotropic materials more than one material property non-solid elements (the algorithm is used for solids in the same model) In reporting stress results, if identical positive and negative stresses are the highest stresses, Mechanica reports the positive stress. If the negative value is slightly higher than the positive value, Mechanica still reports the positive value. 853 Structural and Thermal Simulation - Help Topic Collection Example: Contour Plot Following is an example of a contour plot with IsoSurfaces turned on: Quantity Notes for Modal and Dynamic Analyses These notes can be helpful when you want to display results for modal and dynamic analyses: • For modal analyses, values for all quantities are not absolute. You cannot compare them to quantities from any other type of analysis. Mechanica unit normalizes displacements and rotations to 1.0 by dividing all displacements by the maximum displacement response. All other modal quantities are mass normalized. If you want to mass normalize displacements and rotations, use the –massnorm engine option. If you select Full Results when you define your analysis, the result window displays all valid quantities plus all valid measures. If you do not select Full Results, the result window displays only the valid measures. • 854 Structural and Thermal Simulation Top and Bottom Shell Location Select Top, Bottom, or Top And Bottom from the first option menu to display the values of the shell top or bottom or both top and bottom at a given plotting-grid point for shells and 2D shells. When you select Top, Bottom, or Top And Bottom from the first option menu, the second option menu appears. If the model does not contain laminate shells, only the first of these items is available on the option menu: • • Shell — Select this option to display a quantity at the top, bottom, or top and bottom of the shell location. Ply — Select this option to display a quantity at the top, bottom, or top and bottom of the ply location. This option is only available if there are shells with laminate properties in the model. When you select Ply, a spin box appears enabling you to select the ply for which to show the results. Maximum and Minimum Shell Values Select Maximum or Minimum from the first option menu to display the most positive or negative value of the shell top or bottom at a given plotting-grid point for shells and 2D shells. When you select Maximum or Minimum from the first option menu, the second option menu appears. This menu contains these items: • • • Of Shell Top/Bottom — Display the maximum (or minimum) values of the shell top or bottom simultaneously on the shell. Of Ply Top/Bottom — Include results on a specific ply number. This option is available only if your model contains laminate shells. Of All Plies — Include all the plies of the model in the results display. This option is available only if your model contains laminate shells. When you select Of Ply Top/Bottom, a spin box appears on the dialog box for entering the ply number for which to display the results. Results Relative to Material Orientation You can define results relative to material orientation if the quantity you select specifically reports for shells—for example, Shell Resultant quantities or Stress and Strain quantities that include shell contributions. When you select Material Orientation from the Relative To option menu, Mechanica displays your results relative to the directional component you select on the Component option menu. For more information about material orientation, see About Material Orientation. 855 Structural and Thermal Simulation - Help Topic Collection Reaction Results Reporting Following are some details for how Mechanica reports reaction results: • • • • Mechanica reports point reactions in force units and reports curve and edge reactions in force per unit length units. Mechanica does not report reaction force data at constraints you associated with a UCS. Mechanica calculates reaction force values for each element at locations shared by more than one element. Mechanica reports the maximum of those values at the shared location when displaying results. Mechanica always reports the maximum reaction force at locations shared by more than one element. Velocity Results Quantity Mechanica supports this quantity for dynamic time and frequency analyses with full results. The Velocity quantity is not available in FEM mode. When you select Velocity from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections on the Quantity tab include: • • • • • Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Include Contribution from Beams — Select the beam contributions to include in the result window definition. This area appears only if there are beams in the model. Include Contribution from Shells — Select the shell contributions to include in the result window definition. This area appears only if there are shells in the model. Relative To — Display results relative to a directional component. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. Thermal Strain Results Quantity Mechanica supports this quantity for all FEM mode Structure models that include temperature loads. The Thermal Strain quantity is not available for native mode. When you select Thermal Strain from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the analysis or design study you choose. 856 Structural and Thermal Simulation The possible selections include: • • • Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. Vectors Display Type Use the Vectors display type to display your results as a vector plot. Vector plots display the directional behavior of the quantity by superimposing sets of colored arrows over a transparent view of your model. Each colored set of arrows represents a different range of values for the quantity you are viewing. Vector plots use arrow length and color to indicate the magnitude of the directional forces. To get a better idea of what a vector plot looks like, you can review an example. When you select Vectors from the Display Type option menu, the options available on the Display Options tab become specific to vector result window displays. The Display Options tab displays some or all of these items depending on the design study and quantity you choose and the selections you make on the tab: • • • • • • • • Wireframe/Shaded — Designate whether the vectors are drawn as wireframe vectors or as shaded (polygon) vectors. Legend Levels — Set the number of legend levels to display in the result window. The minimum value is 2, and the maximum is 16. The default is 9 levels. Max Length — Enter a real, positive number to designate the maximum relative length of the vectors to be drawn in the result window. The default value is 5. Deformed — Display your model in its deformed state. Additionally, you can display an undeformed wireframe or transparent version of the model superimposed over the deformed model. Show Element Edges — Display the edges of the elements in your model when you display the results. Show Loads — Display the load icons in your model when you display the results. Show Constraints — Display the constraint icons in your model when you display the results. Animate — Animate the display of your results in the result window. You can select Auto Start, Reverse-Repeat-Alternate options, and the number of frames in the animation. The Animate option is unavailable for fatigue results. For Max Principal Stress or Min Principal Stress, Mechanica displays a vector plot for both quantities. See an example of a Max Principal Stress vector plot. 857 Structural and Thermal Simulation - Help Topic Collection Animating Your Results Display Use animation to display your results for these purposes: • • • to animate mode shapes to animate deformations in your model in conjunction with quantities such as displacement, stress, strain, strain energy, and so on for buckling analyses, to animate the mode shapes so that you can fully understand how the structure fails You can animate fringe, vector, or model result displays using the Display Options tab on the Result Window Definition dialog box. You cannot animate fatigue or linearized stress results. When you select Animate on the Display Options tab, these options become available: • Auto Start — Start the animation as soon as the result window displays. You can also start and stop the animation using the View>Start, View>Step Forward, and View>Stop commands, or the corresponding toolbar buttons on the result window. • Playback mode — Designate the playback mode of the animation by clicking one of these buttons: o o o (Repeat) — In a static animation, the model moves from zero to maximum deformation in equal, linear steps. (Reverse) — In a static animation, the model moves from zero to maximum deformation and back to zero in equal, linear steps. • (Alternating) — In a modal animation, the model moves from zero to maximum deformation, back to zero deformation, then to negative maximum deformation, and then back to zero, changing shape in unequal steps. Frames — Enter the number of frames you want in a single animation cycle. The default number of frames is 8. The number of frames must be a multiple of 4 except for step animation. If you define a deformed result display, you can toggle the deformed overlay on the animation by selecting View>Overlay in the Results user interface window. When you display the result window for an animated model, you can speed up or slow down the animation by moving the slider on the toolbar in the appropriate direction. For information on controlling your animation, see Controlling Animations. 858 Structural and Thermal Simulation Insert Result Windows From Template Dialog Box Use the Insert Result Windows From Template dialog box to define the contents of a result window using a template. When you use the Insert>Results Window From Template command the Insert Result Windows from Template dialog box appears. This dialog box contains the following areas: • Design Study Selection — Use this area to select a design study or analysis. • Design Study — Select a design study. • Analysis — Select an analysis. Template Selection — Select the template you want to use for the results. Load Set Selection — Determine whether to record results for one or several of the load sets in your model. You must also decide whether to repeat the analysis for each load set, or to combine them. This section appears only if your analysis contains more than one load set. Mode Selection — Determine whether to record results for one or several of the modes in your model. You must also decide whether to repeat the analysis for each mode, or to combine them. This section appears only if your analysis contains more than one mode. Step Selection — Determine whether to record results for one or several of the steps in your model. You must also decide whether to repeat the analysis for each step, or to combine them. This section appears only if your analysis contains more than one load step or time step. • • • • If the template and options combine to produce more than 16 windows, then only the first 16 will be shown. Tips for Fringe Displays These tips can be helpful when you want to create a fringe plot: • For models with a large number of elements, you should look at your results on a contour plot before attempting a fringe plot. Drawing a fringe plot for a large model can be time-consuming. You save time by using a contour plot to view results data. If you want to display fringe and contour result windows that match exactly, enter one less number of contour levels than fringe levels. • 859 Structural and Thermal Simulation - Help Topic Collection Example: Max Principal Stress Vector Plot This is an example of a vector plot using Max Principal Stress: Components for Beam Bending, Tension, Torsion, and Total If the design study you select contains beams, when you select Stress or Strain from the Quantity option menu, the Component option menu displays the components specific to beams in addition to the other components valid for these quantities. If you select Stress from the Quantity option menu and then select one of the beam components from the Component option menu, the check boxes in the Include Contribution From Beams area become unavailable. You can still select an item from the option menu in that area. These are the beam options that can appear on the stress or strain Component option menu: • • • • Beam Bending — Display beam bending in the result window. Beam Tensile — Display beam tension in the result window. Beam Torsional — Display beam torsion in the result window. Beam Total — Display beam tension plus beam bending in the result window. In FEM mode, the only available component specific to beams is Beam Total for the stress quantity. It appears when you display results from the NASTRAN .xdb file. 860 Structural and Thermal Simulation Contour Results Display A contour plot is a type of fringe plot that shows you where the borders of the value ranges lie, as calculated by your analysis or as determined by how you set your legend values. For example, if you display a contour plot of von Mises stress, Mechanica shows a transparent view of your model with the the borders of each stress range shown in a different color. To get a better idea of what a contour plot looks like, you can review an example. When you select Fringe from the Display Type option menu, these items become available on the Display Options tab: • Contour — Display your results model with contour lines. Selecting this check box activates the IsoSurfaces and Label Contours check boxes. Displaying your model using contour lines is ideal for shell or 2D models. For solids, you can get a more informative display of model behavior if you select the IsoSurfaces check box as well. • Label Contours — Select this item to display the value for each contour curve directly in the result window. You probably need to label a contour plot only if you are printing black and white hard copy. The contour colors generally provide enough information when you look at a result window on the screen or on a color hard copy. • IsoSurfaces — Define a contour plot with isosurfaces instead of lines. With this option, you can enhance a contour plot by extending 2D isolines into 3D isosurfaces. Isosurfaces can help you map the interior behavior of your model because they let you see how a quantity varies within solid elements. To change the density of the contour labels so there are more or less in a given area, select Utilities>Relabel Contour from the Results user interface menu bar. Strategy: Using Convergence Graphs to Review Results You can use a convergence graph to determine whether a measure quantity converged acceptably. In a graph that shows good convergence of a measure, the curve becomes asymptotic as it plots values for the final p-passes. The following graph shows how the strain energy in a model converged with each p-loop pass. 861 Structural and Thermal Simulation - Help Topic Collection Measures you might want to graph include strain_energy or max_disp_mag for static analyses, modal_frequency for modal analyses, and energy_norm, max_temperature, or max_flux_mag for thermal analyses. Note that if an analysis converges on local displacement and strain energy or local temperatures and local energy norms, the stress or flux values may not converge. The following graph shows that maximum von Mises stress values are still increasing as of the final p-pass and, therefore, did not converge. 862 Structural and Thermal Simulation Tip: To facilitate convergence, create a layer of small elements around features that exhibit high stress or flux concentrations. For more information, see Singularities. If you are interested in stresses or fluxes, create a convergence graph of the particular stress or flux measures of interest to you. Strategy: Interpreting Beam Resultant Forces and Moments By understanding the sign conventions used for beam resultant forces and moments, you can more easily interpret the results that Structure reports. The following figure illustrates the sign conventions Mechanica uses for resultant forces and moments in beams. The X axis for the beam is defined along the beam length. 863 Structural and Thermal Simulation - Help Topic Collection Note that in the positive direction of the beam element, positive Fx acts in the positive normal X direction. However, in the negative direction of the beam element, positive Fx acts in the negative normal X direction. The resultant moments follow the same sign convention. Applying this resultant force and moment convention to a typical example, note how the results of a beam model solved in Structure relate to a free-body diagram. In the cut section, the resultant forces Fy and moment couple Mz act to maintain equilibrium. In beam a, Fy is negative while, in beam b, Fy is positive. Mz is negative 864 Structural and Thermal Simulation in both beams. Structure always reports values for the resultant forces and moments for the positive direction of the free-body diagram. The X axis for beams is along the length of the beam, with the positive X direction determined when you select the beam references. To find the positive beam direction, look at the orientation of the beam icon axes. The beam icon displays the Y and Z axes for the BSCS. You can determine the positive X direction using the righthand rule. Since Mechanica reports resultant values based on the positive beam direction, review the orientation of the BSCS before running an analysis to ensure that results will make sense to you. If the orientation is reversed, the sign of resultant forces and moments will change. Types of Measure Results Graphs Measure graphs provide different information depending on the type of design study: Standard (except dynamic analyses) Shows the measure's value after each p-loop pass. Use this graph to see how well the analysis converged. You can create this graph only if the analysis uses the multi-pass adaptive convergence method. The location is P-Pass. Note: Mechanica uses absolute values to graph a convergence quantity. Use the Info>Status command on the Analyses and Design Studies dialog box to check the summary file for the actual value of a convergence quantity at each P-loop pass. Standard (dynamic analyses only) Shows the measure's value at each step of a dynamic time, frequency, or random analysis. You can graph this if you select At Each Step for the analysis. The location can be time or frequency. Optimization Shows the measure's value at each step of the optimization. The location is Optimization Pass. Shows the measure's value as a design parameter changes. Design Param is the location. Local or Global Sensitivity 865 Structural and Thermal Simulation - Help Topic Collection Results Relative to Coordinate Systems When you select Coordinate System from the Relative To option menu, a selector arrow appears next to the Coordinate System option. Click the selector arrow to select a UCS from your model. WCS is the default coordinate system. After you select the coordinate system, Mechanica displays the appropriate component labels, as follows: Coordinate System Cartesian Cylindrical Spherical Components X, Y, Z R, T, Z R, T, P Mechanica saves the coordinate system you select when you save a result window definition. Results Relative to Beam Orientation When you select Beam Orientation from the Relative To option menu, Mechanica displays your results relative to the beam orientation that you specified while creating the beam. Beam orientation is available only for design studies with beams. Select Beam Orientation to get results in terms of the local beam coordinates. See About Beam Orientation for information on specifying coordinate systems for beams. 866 Structural and Thermal Simulation Example: Vector Plot Following is an example of a vector plot of model displacement: 867 Structural and Thermal Simulation - Help Topic Collection Example: Fringe Display Following is an example of a fringe plot with Continuous Tone turned on: Local Sensitivity Graph Notes For local sensitivity design studies, if you gave your design parameter an especially large range, a graph can cross the X or Y axis and look as if it were showing negative values. This does not mean that there are negative values associated with the graph. It may appear this way in a local sensitivity study because the result of interest is the slope of the curve between two sample points, not specific values. For more information about local sensitivity graphs, see Local Sensitivity Study. 868 Structural and Thermal Simulation Deformed Results Display Use to view a displaced or deformed version of your model. You can also overlay an undeformed model or a transparent filled representation of the model. The Deformed option is available for structural, dynamic, and contact analyses only. After you select Deformed, these options are available: • • • Overlay Undeformed — Superimpose the undeformed wireframe model over the deformed model in the result window. Selecting this check box activates the Transparent Overlay check box. Transparent Overlay — Display the overlay as a transparent filled representation of the model. Scaling — Enter a positive real number or a percentage value for scaling. Note that for percentage, you must enter a % symbol after the value. The default is 10% except for contact and large deformation analyses, which have a default of 1. If you enter a positive real number, Mechanica scales the deformed shape by the specified value. If you enter a percentage value, Mechanica scales the deformed shape by the specified percentage of the model size. Use a scale factor of 1 to show the true deformation, or a scale factor of 10% to show an exaggerated deformation. For example, suppose the size of the model is 10 inches and the maximum computed displacement for the analysis is 0.05 inches. If you enter a scale factor of 3%, then Mechanica displays a deformed model with the maximum displacement equal to 10 inches * 0.03 (that is 3%) = 0.3 inches. If you enter a scale factor of 3, then Mechanica displays a deformed model with the maximum displacement equal to 0.05 inches * 3 = 0.15 inches. Tip: Entering a percentage can take some of the guesswork out of finding the scale factor you want. Mechanica translates the percentage into a magnitude. After you display this results window, this dialog box shows the magnitude instead of the percentage. You can toggle the deformed overlay on an animation by selecting View>Overlay in the Results user interface window. Acceleration Results Quantity Mechanica supports this quantity for dynamic time and frequency analyses with full results. The Acceleration quantity is not available in FEM mode. 869 Structural and Thermal Simulation - Help Topic Collection When you select Acceleration from the Quantity option menu, Mechanica may alter selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections include: • • • Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. Components for Acceleration, Displacement, Reaction, Rotation, Rotation Acceleration, Rotation Velocity, or Velocity When you select Acceleration, Displacement, Reaction, Rotation, Rotation Acceleration, Rotation Velocity, or Velocity from the Quantity option menu, the Component option menu displays the components specific to these quantities. Use this option menu to further refine your quantity definition. The choices available on this menu depend on the design study, display type, and quantity combination you select. These are the options that can appear on the Component menu if you select Acceleration, Displacement, Reaction, Rotation, Rotation Acceleration, Rotation Velocity, or Velocity: • • • Magnitude — the magnitude of the quantity vector, which is equivalent to selecting all three components. Magnitude is not available for the reaction quantity. X — the quantity in the X direction or about the X axis. X is not available for reaction moment, rotation, rotation acceleration, and rotation velocity for all 2D models. Y — the quantity in the Y direction or about the Y axis. Y is not available for 2D plane strain and 2D axisymmetric models. Y is not available for reaction moment, rotation, rotation acceleration, and rotation velocity for all 2D models. Z — the quantity in the Z direction or about the Z axis. Z is not available for any 2D model. • If you change the coordinate system type for your results display, the directional components in the Component option menu change to reflect the new coordinate system. For example, if you change from the Cartesian coordinate system to the cylindrical coordinate system, the labels change from X, Y, and Z to R, T, and Z. For more information, see Results Relative to Coordinate Systems. 870 Structural and Thermal Simulation Secondary Quantity Option Menu This option menu appears only for the Beam Resultant, Shell Resultant, Reaction, or Reactions at Point Constraints quantities. The items on the menu vary depending on the design study, display type, and quantity you choose. These are the items that can appear on the Secondary Quantity option menu: • • • Force — Specify that you want to evaluate beam resultant forces, shell resultant forces, or reaction forces at point constraints. Moment — Specify that you want to evaluate beam resultant moments, shell resultant moments, or reaction moments at point constraints. Transverse Shear Force — Specify that you want to evaluate shell transverse shear in the Z direction. This option is available only if you select Shell Resultant as your quantity. The components that appear on the Quantity tab change depending on whether you select Force, Moment, or Transverse Shear Force. For more information, see the component topics for Beam Resultant, Shell Resultant, Reaction, or Reactions at Point Constraints. Displacement Results Quantity Mechanica supports this quantity for all Structure models. When you select Displacement from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the analysis or design study you choose. The possible selections include: • • • • • Amplitude — Use this option button to indicate that you want Mechanica to display displacement in terms of amplitude. This button is available for FEM mode dynamic analyses only. Phase — Use this option button to indicate that you want Mechanica to display displacement in terms of phase. This button is available for FEM mode dynamic analyses only. Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. 871 Structural and Thermal Simulation - Help Topic Collection Contact Pressure Results Quantity Mechanica supports this quantity for contact analyses that include calculated stresses. The software reports the contact pressure between the entities that define the contact region. The Contact Pressure quantity is not available in FEM mode. If you select Contact Pressure from the Quantity option menu and Graph as your display type, Mechanica adds the Graph Location selection to the Quantity tab. Use the associated selector arrow to display your model and pick the entity you want to use in your results display. Graph Location Use the Graph Location area on the Quantity tab to select specific locations for your graph result window display. The Graph Location area includes these items: • Graph Location — Select from the option menu the locations you want to display in your graph result window. You can select multiple connected beams or curves. In FEM mode, you can select multiple connected edges. The options on the menu include: o Curves o Beams o P-Pass (Measure quantity only) o Optimization Pass (Measure quantity only, optimization study only) o Design Param o Time o Frequency Location Selector Arrow — Use the selector arrow to select the specific entity on your model that you want to display in the graph results window. The selector arrow is available only for curves and beams. • Components for Beam Resultant When you select Beam Resultant from the Quantity option menu, the Component menu displays the components specific to that quantity. Use this option menu to further refine your quantity definition. These options appear on the Component menu: • • • X — the beam resultant quantity about the X axis. Y — the beam resultant quantity about the Y axis. Z — the beam resultant quantity about the Z axis. Z is not available for 2D models. If you change the coordinate system type for your results display, the directional components in the Component option menu change to reflect the new coordinate system. For example, if you change from the Cartesian coordinate system to the 872 Structural and Thermal Simulation Cylindrical coordinate system, the labels change from X, Y, and Z to R, T, and Z. For more information, see Results Relative to Coordinate Systems. Fatigue Results Quantity Mechanica supports this quantity for fatigue analyses in Structure. The Fatigue quantity is not available in FEM mode. When you select Fatigue from the Quantity option menu on the Quantity tab, Mechanica displays a Component option menu. For fatigue analyses, Mechanica reports results for all surfaces on your model, but not the interior of your model. Beam Resultant Results Quantity Mechanica supports this quantity for 3D models that include beams. In FEM mode, Beam Resultant becomes available on the Quantity option menu when you load results from an MSC/NASTRAN file. When you select Beam Resultant, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the analysis or design study you choose. The possible selections include: • • • Secondary quantity option menu — Select a secondary quantity option. Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. This item is available only when you select X, Y, or Z from the Component option menu. When reviewing beam resultant results, you should be aware of the sign conventions used for beam resultant forces and moments. An understanding of the sign conventions will help you interpret your results correctly. Shell Contribution Use the Include Contribution From Shells area of the Quantity tab to select the shell contributions you want to use for the result window. This area does not appear on the dialog box unless there are shells in the model and they were part of the design study. Note: The discussion below pertains to all quantities that allow specific measurement of shell behavior except for Strain Energy. The options in the Include Contribution From Shells area determine the values used for plotting the result display. All of the check boxes are selected by default. 873 Structural and Thermal Simulation - Help Topic Collection The selections in the Include Contribution From Shells area are as follows: • • • Membrane — Include membrane values for shells in the result display. Bending — Include bending values for shells in the result display. Transverse Shear — Include transverse shear for shells in the result display. There are two option menus below the check boxes. These are the possible options available on the first option menu, and they determine the options available on the second menu: • • • • • Maximum — Display the maximum value of the shell top or bottom at a given plotting-grid point for shells and 2D shells. Maximum is the default option for stress. Minimum — Display minimum value of the shell top or bottom at a given plotting-grid point for shells and 2D shells. For stress, this option appears only with Min Principal. Top — Select this item to use the value of the shell top. The top of a shell or 2D shell is in the normal direction. Bottom — Select this item to use the value of the shell bottom. The bottom of a shell or 2D shell is opposite the normal direction. Top and Bottom — Select this item to display the values of the shell top and bottom simultaneously on the shell, with the top values at the top, and the bottom values at the bottom. Relative To When you select a directional component for a quantity, you can choose the reference direction of the component from the Relative To option menu. The reference options available on the Relative To menu vary depending on the quantity. Use the Relative To menu to display results relative to: • • • • a coordinate system the material orientation the ply orientation the beam orientation Rotation Acceleration Results Quantity Mechanica supports this quantity for dynamic time and frequency analyses with full results. Be aware that: • • • For the Rotation Acceleration quantity, you must select Rotations as an analysis output when you define the analysis. Your model must be a shell or beam model or a mixed solid model with beams or shells present. You cannot specify rotation as a quantity for 2D plane stress models. The Rotation Acceleration quantity is not available in FEM mode. 874 Structural and Thermal Simulation When you select Rotation Acceleration from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections include: • • • Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. Mechanica reports rotation acceleration in radians per unit of time squared. Temp Gradient Results Quantity Mechanica supports this quantity for all Thermal models. For modal analyses, Mechanica only calculates the Temp Gradient quantity if you select Heat Flux as an analysis output when you define the analysis. When you select Temp Gradient from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections on the Quantity tab include: • • • Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. Thermal Strain Energy Results Quantity Mechanica supports this quantity for FEM mode Structure models that include temperature loads. The Thermal Strain Energy quantity is not available for native mode. If you select Thermal Strain Energy from the Quantity option menu and Graph as your display type, Mechanica adds the Graph Location selection to the Quantity tab. Use the associated selector arrow to display your model and pick the entity you want to use in your results display. 875 Structural and Thermal Simulation - Help Topic Collection Temperature Results Quantity Mechanica supports this quantity for all Thermal models. When you select Temperature from the Quantity option menu and Graph as your display type, Mechanica may add the Graph Location selection to the Quantity tab. Use the associated selector arrow to display your model and pick the entity you want to use in your results display. Strain Energy Results Quantity Mechanica supports this quantity for all Structure models. For most modal analyses, Mechanica only calculates the Strain Energy quantity if you select Stresses or Ply Stresses as an analysis output when you define the analysis. When you select Strain Energy from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections include: • Include Contributions from Beams — Select the beam contributions to include in the result window definition. This area appears only if there are beams in the model. This area does not appear in FEM mode. The selections in the Include Contribution From Beams area include: o Shear — Include shear values for shells in the result display. o Bending — Include bending for beams in the result display. In FEM mode, this box is always checked. o Tensile — Include tension for beams in the result display. In FEM mode, this box is always checked. o Torsional — Include torsion for beams in the result display. In FEM mode, this box remains unchecked. Include Contributions from Shells — Select the shell contributions to include in the result window definition. This area appears only if there are shells in the model. This area does not appear in FEM mode. The selections in the Include Contribution From Shells area include: o Membrane — Include membrane values for shells in the result display. o Bending — Include bending values for shells in the result display. o Membrane-Bending — Include both membrane and bending values for shells in the result display. o Transverse Shear — Include shear values for shells in the result display. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. • • Shell Resultant Results Quantity Mechanica supports this quantity for 3D models that include shells. Mechanica obtains values for shell resultant forces and shell transverse shear forces by integrating stress components through the thickness of the shell. For information 876 Structural and Thermal Simulation about shell properties and shell results, including how Mechanica represents the mechanical properties mathematically, see Shell Property Equations. In FEM mode, Shell Resultant becomes available on the Quantity option menu when you load results from an MSC/NASTRAN file. The system only supports CQUAD4 and CTRIA3 shell elements. If your model contains CQUAD8 or CTRIA6 elements, the Quantity option menu does not display Shell Resultant. For information on MSC/NASTRAN output formats, see MSC/NASTRAN. When you select Shell Resultant from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections include: • • • Secondary Quantity option menu — Select a secondary quantity option. Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. This item is available only when you select X, Y or Z from the Component option menu. Shear & Moment Results Quantity Mechanica supports this quantity for Structure models that contain beams, provided you select Graph as your display type. In FEM mode, the Shear & Moment quantity is only available when you are loading results from an MSC/NASTRAN .xdb file. When you select Shear & Moment from the Quantity option menu, Mechanica alters the selections on the Quantity tab. The selections include: • • Beam Area — Select the beam components to include in the result window definition. Mechanica displays up to six graph curves on separate graphs depending on the number of beam components you select. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. Rotation Velocity Results Quantity Mechanica supports this quantity for dynamic time and frequency analyses with full results. Be aware that: • • • For the Rotation Velocity quantity, you must select Rotations as an analysis output when you define the analysis. Your model must be a shell or beam model or a mixed solid model with beams or shells present. You cannot specify rotation as a quantity for 2D plane stress models. The Rotation Velocity quantity is not available in FEM mode. 877 Structural and Thermal Simulation - Help Topic Collection When you select Rotation Velocity from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections include: • • • Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. Mechanica reports rotation velocity in radians per unit of time and displays the square root of the sum of the squares (SRSS) of the rotation components you select. Rotation Results Quantity Mechanica supports this quantity for Structure analyses of shell and beam models. Be aware that: • • For the Rotation quantity, you must select Rotations as an analysis output when you define the analysis. You cannot specify rotation as a quantity for 2D plane stress models. For FEM mode, the Rotation quantity is available for all models, but only returns nonzero results for beam and shell models. When you select Rotation from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections include: • • • • • Amplitude — Use this option button to indicate that you want Mechanica to display rotation in terms of amplitude. This button is available for FEM mode dynamic analyses only. Phase — Use this option button to indicate that you want Mechanica to display rotation in terms of phase. This button is available for FEM mode dynamic analyses only. Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. Mechanica reports rotation in radians (1 radian = 57.29578 ) and displays the SRSS of the rotation components you select. 878 Structural and Thermal Simulation Flux Results Quantity Mechanica supports this quantity for all Thermal models. For thermal analyses, Mechanica only calculates the Flux quantity if you select Heat Flux as an analysis output when you define the analysis. When you select Flux from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections on the Quantity tab include: • • • Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. Model Display Type When you select Model from the Display Type option menu, the options available on the Display Options tab become specific to model result window displays. Use Model for these purposes: • • • • • • to display your original model with all loads, constraints, and other model entities to display your FEM model's geometry in its original form to display and animate your model's structural deformations. You can use Model this way in standard design studies only. to display the optimized shape of your model to display the linearized stresses of your model to display an undeformed model as a rendering of the analysis model The Display Options tab displays some or all of these items depending on the design study and quantity you choose and the selections you make on the tab: • • • • Shade Surfaces — Display your model as light-source shaded frames. If you do not select the check box, the animation appears as a series of wireframe images. Deformed — Display your model in its deformed state. Additionally, you can display an undeformed wireframe or transparent version of the model superimposed over the deformed model. Show Element Edges — Display the edges of the elements in your model when you display the results. Show Loads — Display the load icons in your model when you display the results. 879 Structural and Thermal Simulation - Help Topic Collection • • Show Constraints — Display the constraint icons in your model when you display the results. Animate — Animate the display of your results in the result window. You can select Auto Start, Reverse-Repeat-Alternate options, and the number of frames in the animation. This option is unavailable for fatigue or linearized stress results. Components for Shell Resultant When you select Shell Resultant from the Quantity option menu, a secondary quantity option menu appears. Depending on what you select from the secondary quantity option menu, the Component menu displays the components specific to this quantity. Use this option menu to further refine your quantity definition. If you select Moment or Force from the secondary quantity option menu, these options appear on the Component menu: • • • • • Max Principal — the maximum principal shell resultant. For mixed locations that include beams, Max Principal specifies total stress or strain for beams. Min Principal — the minimum principal shell resultant XX — normal shell resultant along the X axis XY — shear shell resultant acting in the Y direction on the plane whose outward normal is parallel to the X axis YY — normal shell resultant along the Y axis If you select Transverse Shear Force from the secondary quantity option menu, these options appear on the menu: • • X — shear force acting in the Z direction on the plane whose outward normal is parallel to the X axis Y — shear force acting in the Z direction on the plane whose outward normal is parallel to the Y axis Regardless of whether you choose Force, Moment, or Transverse Shear Force from the secondary menu, Mechanica enables you to select a reference coordinate system for any of the directional components. If you change the coordinate system type for your results display, the directional components in the Component option menu change to reflect the new coordinate system. For example, if you change from the Cartesian coordinate system to the Cylindrical coordinate system, the labels change from XX, YY, and ZZ to RR, TT, and ZZ. For more information, see Results Relative to Coordinate Systems. Components for Shear and Moment When you select Shear & Moment from the Quantity option menu, the Beam area displays the components specific to this quantity. Mechanica uses these components to plot the shear and moment graph. You can select one of these components only if a beam is associated with the curve. 880 Structural and Thermal Simulation These are the components that appear in the Beam area: • • • • • • P — Axial force Vy — Shear force in the Y direction Vz — Shear force in the Z direction Mx — Torsional moment My — Bending moment about the Y axis Mz — Bending moment about the Z axis Components for Reactions at Point Constraints When you select Reactions At Point Constraints from the Quantity option menu, the Component menu displays the components specific to this quantity. Use this option menu to further refine your quantity definition. • • • X - The quantity in the X direction or about the X axis. X is not available for reaction moment, rotation, rotation acceleration, and rotation velocity for all 2D models. Y - The quantity in the Y direction or about the Y axis. Y is not available for 2D plane strain and 2D axisymmetric models. Z - The quantity in the Z direction or about the Z axis. Z is not available for any 2D model. Components for Flux and Temp Gradient When you select Flux or Temp Gradient from the Quantity option menu, the Component option menu displays the components specific to these quantities. Use this option menu to further refine your quantity definition. The choices available on this menu depend on the design study, display type, and quantity combination you select. These are the options that can appear on the Component menu if you select Flux Temp Gradient: • • • • Magnitude — the magnitude of the quantity vector, which is equivalent to selecting all three components. X — the quantity in the X direction or about the X axis. Y — the quantity in the Y direction or about the Y axis. Z — the quantity in the Z direction or about the Z axis. Z is not available for 2D models. If you change the coordinate system type for your results display, the directional components in the Component option menu change to reflect the new coordinate system. For example, if you change from the Cartesian coordinate system to the Cylindrical coordinate system, the labels change from X, Y, and Z to R, T, and Z. For more information, see Results Relative to Coordinate Systems. 881 Structural and Thermal Simulation - Help Topic Collection Reactions at Point Constraints Quantity Mechanica supports this quantity for all Structure models in native mode. For most analyses, Mechanica calculates the Reactions at Point Constraints quantity if you select Reactions as an analysis output when you define the analysis. When you select Reactions at Point Constraints from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections on the Quantity tab include: • • Secondary Quantity option menu — Select a secondary quantity option. Component — Select a component. Graph Display Type Use the Graph display type to display graphs of your selected quantity. In FEM mode, you can create graphs for most quantities along one or more edges. For native mode, you can create graphs for: • • Most quantities along one or more curves or beams Predefined or user-defined measures. In this case, the graph shows the result quantity as a function of: o The p-loop pass iteration number in a multi-pass analysis o The optimization pass number in an optimization design study o The value of a design parameter in a global or local design study. For additional information, see Local Sensitivity Graph Notes. o Time or frequency in a dynamic analysis Shear & moment on a curve or beam A study that did not converge when you used the multi-pass adaptive convergence method. In this case, you can create a convergence graph to get more information on why the study did not converge. • • When you select Graph from the Display Type option menu, the Display Options tab and the Display Location tab become unavailable. Quantity for Result Windows Use the Quantity option menu on the Quantity tab of the Result Window Definition dialog box to select the quantity you want to display in the result window. The list of quantities available on the Quantity option menu varies depending whether you are working in native mode or FEM mode as well as on the design study and analysis you select in the Study Selection area of the dialog box. 882 Structural and Thermal Simulation These are the possible choices available on the Quantity option menu: Native Mode • • • • • • • • • • • • • Acceleration Beam Resultant Contact Pressure Displacement Failure Index Fatigue Flux Measure P-Level Reaction Reactions at Point Constraints Rotation Rotation Acceleration • • • • • • • • • Rotation Velocity Shear & Moment Shell Resultant Strain Strain Energy Stress Temp Gradient Temperature Velocity • • • • • • • • • • • • • • FEM Mode Beam Resultant Displacement Flux Reaction Rotation Shear & Moment Shell Resultant Strain Strain Energy Stress Temp Gradient Temperature Thermal Strain Thermal Strain Energy After you select a quantity from the Quantity option menu, additional selections appear that you can use to define the quantity. For information on how Mechanica handles quantities for modal and dynamic analyses, see Quantity Notes for Modal and Dynamic Analyses. Reaction Results Quantity Mechanica supports this quantity for all Structure models. You can display reaction results using the Graph display type only. The Reaction quantity represents reaction forces and moments at constrained curves, edges, or points, for all element types. These results are available for static and modal analyses if you selected Reactions as an analysis output. Mechanica reports reactions using specific criteria that you should be aware of as you evaluate your results. For FEM mode, Mechanica reports reaction forces at constrained curves, edges, or points for all element types. FEM mode does not provide results on reaction moments. When you select Reaction from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections include: • • • Secondary quantity option menu — Select a secondary quantity option. For FEM mode, Force is the only secondary quantity and, therefore, the secondary quantity option menu displays this item only. Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. 883 Structural and Thermal Simulation - Help Topic Collection • Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. For more information about the Reaction quantity, see Reaction Results Reporting. P-Level Results Quantity Mechanica supports this quantity provided you select Fringe as your display type. This quantity is available for analyses using the multi-pass adaptive convergence method. The P-Level quantity is not available in FEM mode. Use P-Level to review a fringe plot of the maximum polynomial order Mechanica calculated, set along each of the element edges in your model. The thickness of the lines representing element edges in the P-Level fringe plot depends on the polynomial order value. The higher the polynomial order value, the thicker Mechanica draws the line. When you select P-Level from the Quantity menu, the Display Options and Display Locations tabs are unavailable. Components for Stress or Strain When you select Stress, Strain, or Thermal Strain (FEM only) from the Quantity option menu, the Component menu displays the components specific to these quantities. Use this option menu to further refine your quantity definition. The choices available on this menu depend on the design study, display type, and quantity combination you select. Following are the possible items that appear in the Component menu if you select Stress, Strain, or Thermal Strain (FEM only). If you have a beam model, Mechanica displays additional items. • Max Principal — the maximum principal stress or strain. For mixed locations that include beams, Max Principal specifies total stress or strain for beams. For an example of a Max Principal stress vector display, see Example: Max Principal Stress Vector Plot. Min Principal — the minimum principal stress or strain Mid Principal — the principal stress or strain that has a numerical value between max principal and min principal von Mises — a combination of all stress components. This component is not available for Strain or Thermal Strain quantities. Maximum Shear — one-half the maximum absolute difference between the principal stresses or strains. This component is not available for Strain or Thermal Strain quantities. XX — normal stress or strain along the X axis XY — shear stress or strain acting in the Y direction on the plane whose outward normal is parallel to the X axis • • • • • • 884 Structural and Thermal Simulation • • • • XZ — shear stress or strain acting in the Z direction on the plane whose outward normal is parallel to the X axis. This component is only available for 3D models. YY — normal stress or strain along the Y axis YZ — shear stress or strain acting in the Z direction on the plane whose outward normal is parallel to the Y axis. This component is only available for 3D models. ZZ — normal stress or strain along the Z axis. This component is only available for 3D models. For directional components, Mechanica displays the Relative To option menu, enabling you to display the result relative to a coordinate system, laminate ply, and so forth. Be aware that if you change the coordinate system for your results display, the directional components in the Component option menu change to reflect the new coordinate system. For example, if you change from Cartesian to Cylindrical, the labels change from XX, YY, and ZZ to RR, TT, and ZZ. For more information, see Results Relative to Coordinate Systems. Native mode expresses stress values and directions somewhat differently than they are sometimes described in textbooks. To learn more about how native mode stresses relate to textbook examples, see How Stress Components Relate to Textbook Examples. Failure Index Results Quantity Mechanica supports this quantity for Structure analyses on models where you defined a failure criterion for at least one of the materials. The Failure Index quantity is not available in FEM mode. Use Failure Index to determine whether a material has failed under given loading conditions. If the failure index is: • • less than 1 — the material has not failed equal to or greater than 1 — the material has failed When reviewing failure index results, be sure to consider the failure modes of the material. If you select Failure Index from the Quantity option menu and Graph as your display type, Mechanica adds the Graph Location selection to the Quantity tab. Use the associated selector arrow to display your model and pick the geometric entity you want to use in your results display. Measure Results Quantity Mechanica supports this quantity provided you select Graph as your display type. Be aware that you cannot select measures if you combine loads or modes. The Measure quantity is not available in FEM mode. 885 Structural and Thermal Simulation - Help Topic Collection When you select Measure from the menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections include: • Measure Selector — Click the measure selector to display the Measures dialog box, which lists the measures available for this design study. Select one measure from the list. You can also review measures through this dialog box. Graph Location — Mechanica automatically selects P-Pass which is the only location for measure quantities. • See Types of Measure Results Graphs to learn about the kinds of results you can display using Measure as the quantity. Fringe Display Type Use the Fringe display type to display your results as a fringe plot, which is a series of filled color regions on the location you select. Each region is a different color, representing a different range of values for the quantity you are viewing. You can use fringes to determine whether certain results are reasonable. For example, you can look at the fringe plot of maximum principal or von Mises stress for static analyses, or flux magnitude for thermal analyses. You can also create a contour display using the Fringe display type. To get a better idea of what a fringe plot looks like, you can review an example. Also, before defining a fringe display, be sure to read the information in Tips for Fringe Displays. When you select Fringe from the Display Type option menu, the options available on the Display Options tab become specific to fringe plot result window displays. The Display Options tab displays some or all of these items depending on the design study and the selections you make on the Quantity tab and the Display Options tab: • Continuous Tone — Display fringes in continuous tones that transition smoothly between fringes. If you do not select this item, fringes display in discrete colors. A fringe with Continuous Tone selected cannot be exported as a VRML file. Averaged — Display quantities as values averaged at locations where two elements in your model meet. If you clear the check box, the results display as unaveraged values. In FEM mode, this option becomes available only when you load results from an .xdb NASTRAN file. In native mode of Mechanica, the Averaged check box is selected by default and is unavailable for quantities other than flux and temperature gradient. You can clear the check box only for flux and temperature gradient to display the result as unaveraged values. Legend Levels — Set the number of levels to display on the model for a fringe window. The minimum value is 2, and the maximum is 16. The default is 9 levels. • • 886 Structural and Thermal Simulation • • • • • • Contour — Display your model with contour lines or isosurfaces. Set to display or not display contour labels. You cannot select both Continuous Tone and Contour. Deformed — Display your model in its deformed state. Additionally, you can display an undeformed wireframe or transparent version of the model superimposed over the deformed model. Show Element Edges — Display the edges of the elements in your model when you display the results. Show Loads — Display the load icons in your model when you display the results. Show Constraints — Display the constraint icons in your model when you display the results. Animate — Animate the display of your results in the result window. You can select Auto Start, Reverse-Repeat-Alternate options, and the number of frames in the animation. This option is unavailable for fatigue results and linearized stresses. Select Dynamic Query from the Info menu to show the value of the result window's quantity at locations you select. Stress Results Quantity Mechanica supports this quantity for all Structure models. For most modal analyses, Mechanica only calculates the Stress quantity if you select Stresses or Ply Stresses as an analysis output when you define the analysis. For information on how Mechanica calculates and reports stress results, see Stress Notes. When you select Stress from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections on the Quantity tab include: • • • • • Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Include Contribution from Beams — Select the beam contributions to include in the result window definition. This area appears only if there are beams in the model. Include Contribution from Shells — Select the shell contributions to include in the result window definition. This area appears only if there are shells in the model. This area does not appear in FEM mode. Relative To — Display results relative to a directional component. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. 887 Structural and Thermal Simulation - Help Topic Collection Strain Results Quantity Mechanica supports this quantity for all Structure models. For most modal analyses, Mechanica only calculates the Strain quantity if you select Stresses or Ply Stresses as an analysis output when you define the analysis. When you select Strain from the Quantity option menu, Mechanica may alter the selections on the Quantity tab. Some selections do not appear unless the item is part of the design study you choose. The possible selections include: • • • • • Component — Select a component. The directional components that appear on this option menu change if you change the coordinate system using the Relative To option menu. Relative To — Display results relative to a directional component. Include Contribution from Beams — Select the beam contributions to include in the result window definition. This area appears only if there are beams in the model. Include Contribution from Shells — Select the shell contributions to include in the result window definition. This area appears only if there are shells in the model. This area does not appear in FEM mode. Graph Location — Select a location from the option menu to display in the result window. Use the selector arrow to display your model and pick the entity you want to use in your results display. This area appears only if you select a display type of Graph. How Stress Components Relate to Textbook Examples If you are trying to relate the stress results or stress measures reported by native mode Structure to textbook examples, you may find that Mechanica expresses stress component direction somewhat differently than your textbook. The diagram below describes the directions of the stress components in a standard textbook application. 888 Structural and Thermal Simulation The following items explain the relation between the textbook definition of stresses and the values reported by Structure: • and a Textbooks commonly denote normal stresses by the symbol subscript indicating the plane on which the stress acts. A normal stress is positive if it is tensile. Structure denotes the normal stresses in Structure as Stress XX, Stress YY, and Stress ZZ. Textbooks commonly denote shear stresses by the symbol and two subscripts. The first designates the plane on which the shear stress acts and the second indicates the coordinate axis to which it is parallel. The sign of a shear stress depends on the normal of the plane on which it is acting. If the outward normal is positive, the shear stress is positive when it points in the positive direction of the coordinate axis which it parallels. If the outward normal is negative, the shear stress is positive when in points in the negative direction of the coordinate axis which it parallels. Structure denotes the shear stresses as Stress XY, Stress XZ, and Stress YZ. The other three shear stress components follow these equivalent relations: Stress XY = Stress YX Stress XZ = Stress ZX Stress YZ = Stress ZY • Beam Contribution Use the Include Contribution From Beams area of the Quantity tab to select the beam contributions you want to use for the result window. This area does not appear on the dialog box unless there are beams in the model and they were part of the design study or analysis. In FEM mode, you can see this area only when you are loading results from an MSC/NASTRAN .xdb file. However, in this case, Include Contribution From Beams area is inactive—showing you which contributions Mechanica will include in the result window, but not allowing you to select contributions. Note: The discussion below pertains to all quantities that allow specific measurement of beam behavior except for Strain Energy. The options in the Include Contribution From Beams area determine the values that the software uses to plot along the beam curve in the result display. All of the check boxes are selected by default. If you clear all three, the result window does not display any beams. If you select beam bending, beam tensile, beam torsional stress, or beam total from the Component option menu, the check boxes in the Include Contribution From Beams area become unavailable. In FEM mode, since your selection is limited to beam total, the check boxes always remain unaccessible. 889 Structural and Thermal Simulation - Help Topic Collection For quantities that have beams, except for strain energy, the selections in the Include Contribution From Beams area include: • • • Bending — Include bending for beams in the result display. In FEM mode, this box is always checked. Tensile — Include tension for beams in the result display. In FEM mode, this box is always checked. Torsional — Include torsion for beams in the result display. In FEM mode, this box remains unchecked. There is a menu below the check boxes with these options: • • • Maximum — Use the maximum value to evaluate the beams in your model. Minimum — Use the minimum value to evaluate the beams in your model. Maximum Absolute — Use the signed value that has the maximum absolute value to evaluate the beams in your model. If the absolute values of the maximum value and minimum value are equal, Mechanica uses the maximum value. Recovery Point — Use one of the locations at which Mechanica reports stresses for the beams in your model. • Results for FEM About FEM Results Once you solve your model, you can review and evaluate a variety of graphical and statistical results using Mechanica's postprocessor. You can: • view graphical renditions of your model's analysis results by defining and displaying result windows. Using this method you can study a variety of quantities calculated during the analysis—among them, stress, strain, displacement, temperature, and thermal flux. You can study your model's interior as well as its exterior surfaces. You can also animate your model, review fringe plots, examine graphs, and so forth. define FEA parameters to calculate and collect results over the model's geometry. You can use these parameters in relations to drive your model according to your results. review analysis statistics that provide information about how your model behaved. Statistical information provides reports on how particular quantities behave at model locations you specify. You can also generate graphs of how model edges react during analysis. evaluate a report of model behavior at one or more hard points. Hard point reports let you study quantities as measured in reference to the three translational and three rotational axes of a coordinate system you specify. • • • To perform these activities, you should become familiar with how to use the postprocessor. To learn about entering and working with the postprocessor, see Using the Postprocessor. 890 Structural and Thermal Simulation Using the Postprocessor in FEM Mode You perform all evaluation of FEM analysis results using Mechanica's postprocessor. Before starting a results session, you should know how to enter the postprocessor and understand the function of the postprocessing tools. You can enter the postprocessor: • • Automatically — After you have run a FEM solver online, the system opens the postprocessor and loads an .frd file with FEM mesh and results, into memory. By using the File>Open FEM Results command — Mechanica stores FEM meshes and analysis results in .frd files. You can choose to load the stored .frd file. Be aware that the software can only retrieve the file that contains both mesh and results and is compatible with the current model. By selecting the Analysis>Results command — This action enables you to load the NASTRAN results database, which gives you an access to more types of available results. You can use the Analysis>Results command only if you have performed an analysis of the FEM model on the MSC/NASTRAN solver and have an .xdb NASTRAN file available. • Once you enter the postprocessor, Mechanica displays the Results user interface that overlays the Pro/ENGINEER work area and menu bar. You can use the Results user interface to view graphical representations of analysis results by creating and manipulating result windows. Another useful tool is the RESULTS menu that appears as an extension of the menu manager to the right of the work area. The menu does not open if you select the Analysis>Results command and are reading results from the NASTRAN .xdb file. On the RESULTS menu you can: • • • • use the Parameters command to work with result parameters use the Info command to obtain statistical information use the Reports command to review hard point reports use the Visualize command to reopen the Results user interface if you closed it earlier Loading NASTRAN Results Database Mechanica FEM mode gives you direct access to MSC/NASTRAN results that you can load into the postprocessor after you select the Analysis>Results command. The ability to access NASTRAN rather than FEM results that you load through the File>Open FEM Results command, gives you the following advantages: • • You can view more types of available results, such as beam stresses, beam and shell resultants, shear and moment for beams, beam stress recovery points, and so forth. You can view results as either averaged or unaveraged values when you display your results as a fringe plot. There are, however, logical limitations on averaging. 891 Structural and Thermal Simulation - Help Topic Collection As a prerequisite for loading NASTRAN results, you need to perform analyses for your FEM model using the MSC/NASTRAN solver. When you run the solver, it creates a NASTRAN results file with an .xdb extension and stores it in the current directory. When you click the Results command, it opens the Results user interface and displays a file selection dialog box, which you use to specify the .xdb file you want to load. Once you specify the NASTRAN .xdb file, the postprocessor can read information about nodes, elements, and their connectivity, as well as results from the file. Also, the postprocessor looks for a FEM mesh and results .frd file associated with the current model in session and selected .xdb file. The postprocessor uses the .frd file to read mesh data only. If you have solved your model offline, the .frd file may not be present in your current directory, but you can still view results from the .xdb file. Depending on whether the .frd file is present or not, Mechanica takes one of these actions: • If the .frd file is present, Mechanica reads the mesh data from the .frd file into memory and displays a mesh in the Pro/ENGINEER window. You can have access to meshed geometric entities and select them as needed. Also, you can view results by layers and display saved views. If the .frd file is not present, Mechanica continues to display the current model and you have no access to meshed geometry. Graph results, layers, or saved views become unavailable. • Graphical Result Windows Viewing FEM Analysis Results You can view FEM analysis results through the Results user interface, a graphical user interface that provides commands, menus, and functions you use to work with graphical results. The system opens the Results user interface when it enters the postprocessor. To learn how you can access the postprocessor, see Using the Postprocessor. To learn about commands and menus on the Results user interface, and how to work with it, see Working with the Results User Interface. To view analysis results for your model, you need to define and display one or more result windows. A result window is a graphical display of your model's behavior as determined by an analysis. You can define a result window so that it: • • • displays a fringe plot of various quantities of interest, such as stress or strain. You can animate the fringe plot, show interior stresses, compare deformed states against original states, and so forth. displays a graph of specific model quantities along edge curves displays a model view showing displacements When defining a result window, you can select from a variety of display types, quantities, and locations. The exact options and combinations available depend on the type of model and the analysis type you select when you define your analysis. 892 Structural and Thermal Simulation Also, you can use only certain combinations of quantities and displays. For more information on defining your results window, see Result Window Definition Dialog Box. Result Windows Working with the Results User Interface When evaluating analysis and design study results, you work within the Results user interface. This user interface lets you view, evaluate, and manage results for your analyses and design studies. The Results user interface is independent of the Mechanica workspace. The way you open the Results user interface depends on the mode in which you are operating Mechanica. • • Native mode — Use the Analysis>Results command to open the Results user interface. FEM mode — Use the File>Open FEM Results command to open the .frd file that contains the FEM mesh and analysis results for the model on your screen. If you have performed an analysis of your model using the MSC/NASTRAN solver, in addition to being able to view FEM mesh and analysis results, you can also have a direct access to a NASTRAN results .xdb file. For information on different ways of loading results, see Using the Postprocessor in FEM Mode. The Results user interface incorporates a menu bar, toolbar, a set of basic functions, and a built-in workflow designed to facilitate results viewing. This workflow enables you to set up a variety of result views, evaluate individual results, and control scaling and visualization of multiple results so that you can easily compare one quantity of interest with another. Here is a step-by-step overview of what we suggest as your workflow: 1. Viewing results — You define result windows, display and hide them, and control how they appear on-screen and in your reports. 2. Evaluating results — You study the result windows you defined, probe specific areas of your model, and compare your findings for one model, design study, result quantity, or set of conditions with your findings for another. 3. Saving result windows — You save the set of result windows you created so that you can review or re-use them later. 4. Generating reports — You prepare printed and online reports for evaluation and presentation. While this sequence represents the most linear approach to reviewing results, you may find that you move back and forth through these steps as you refine the result views you have set up. Tip: You can perform many operations in the Results user interface against both single and multiple windows. For example, you can change backgrounds for multiple windows, rotate multiple result windows, and so forth. 893 Structural and Thermal Simulation - Help Topic Collection To select a single result window, move your cursor to the window and leftclick it. Mechanica highlights the window border in yellow. To select multiple result windows, press the SHIFT key and left-click each of the windows you want. If you select multiple result windows, Mechanica deactivates certain commands, such as Edit>Result Window and Export>VRML. Results User Interface Menu Bar The Results user interface features a menu bar at the top of the screen. You create and manage your results using the menus. To acquaint you with the organization of menu bar, here is an overview: • • • File menu — Provides commands that control such basic functions of the Results user interface as opening result sets, closing the interface, saving result definitions, and generating reports. Edit menu — Provides commands that modify result definitions, legends, cutting and capping planes, and annotations. View menu — Provides commands that control such aspects of results viewing as model position, shading, and overlays. You can also use this menu to display or hide result windows, start and stop animations, change or save the orientation of your model, and control the visual characteristics of result windows. Insert menu — Provides commands that define result windows, cutting planes, capping planes, and annotations. Info menu — Provides commands that probe your model for specific items of interest such as quantity maximums and minimums, exact quantities at model locations you select, and so forth. Also provides commands to display node IDs, element IDs, and node result values in FEM mode. Format menu — Provides commands that format result window values, color spectrums, and scales. Utilities menu — Provides commands that refine your results and let you perform result comparisons against the same scale. Window menu — Provides commands that let you manipulate your result windows within the Results user interface. • • • • • The Results user interface also includes a toolbar whose buttons give you fast access to the most frequently used commands on the menus just discussed. Results User Interface Toolbar For fast access to some of the most commonly used commands on the menu bar, the Results user interface provides a toolbar with these buttons: Button Action/Name Open — Closes the current set of result definitions and opens a new one. Save — Saves the result windows currently available in the Results user interface. 894 Structural and Thermal Simulation Button Action/Name Save As — Saves the result windows currently available in the Results user interface to a .rwd file you specify. Print — Prints all currently displayed result windows. Insert — Lets you create a result window definition. Edit — Lets you edit a result window definition. Copy — Lets you copy result window definitions. Delete — Deletes the selected result windows. Display — Lets you pick which result windows you want to display. Hide — Hides the selected result windows. Repaint — Repaints all currently displayed result windows. Zoom In — Zooms in on the model in the selected result window. Zoom Out — Zooms out from the model in the selected result window. Refit — Refits the model in the selected result window. Default — Returns the model to the default view. Saved Views — Repositions your model to the orientation of the saved view that you select from the list. Start Animation — Starts an animation of the model in the selected result window. Stop Animation — Stops an animation. Step Animation Backward — Steps backward through an animation frame by frame. Step Animation Forward — Steps forward through an animation frame by frame. Animation Playback Speed Control — Speeds up or slows down all currently displayed animations. 895 Structural and Thermal Simulation - Help Topic Collection Basic Functions for the Results User Interface The Results user interface provides a set of three commands that let you perform basic, low-level functions like opening a set of result windows or closing the Results user interface. These activities are generally preliminary to setting up a results session. You can find all three basic commands on the File menu. Here is an overview of the basic commands: • • • New — Use this command to start a new results session. Open — Use this command to open an existing set of result definitions and view the associated result windows. Exit Results — Use this command to close your results session. Each of these commands clears the current contents of the Results user interface. When you select any of these commands, Mechanica prompts you to save any result windows currently defined for the results session. If you want to save the result windows, reply Yes. Mechanica displays the Save Results Window dialog box. Use this dialog box to create a new .rwd file or save the result windows to an existing .rwd file. Viewing Results To view results, you perform three activities—define result windows, display result windows, and control the general appearance of the result windows you define. The Results user interface features easy, direct methods of defining result windows as well as a variety of view controls. Here is an overview of the method you use to view results: • Define result windows — You define result windows through the Insert>Result Window command or by clicking the Insert button on the toolbar. Mechanica opens the Result Window Definition dialog box. Use the dialog box to select the design studies, display types, quantities, and locations you are interested in. If you want to add or compare the result windows you define to an existing set of result window definitions, use the Insert>Result Window From File command in concert with Insert>Result Definition. You may find that you can define result windows more quickly by copying them. • Display and hide result windows — You display result windows through the View>Display command or by clicking the Display button on the toolbar. When you select this command, the Display Result Window dialog box appears, enabling you to select and deselect various result windows to display. 896 Structural and Thermal Simulation You hide windows by clicking the Hide button. You can hide a single window or multiple windows. You will find this particularly handy as you prepare to generate reports. You can also make a selected result window occupy the entire Result user interface work area through the Windows>Full Screen command. This command expands the current window to occupy the work area. • Control result window appearance — You control how result windows appear on-screen through commands on the View and Format menus. You can also perform some of these activities through toolbar buttons. When you set up your result windows as you want, you can begin to evaluate and compare results. Once you have studied your result windows, you may also want to alter, copy, or delete some of them. Defining Results Result Window Definition Dialog Box Use the Result Window Definition dialog box to define the contents of a result window. Valid quantity and display combinations depend on whether you are working in native mode or FEM mode as well as on the type of model, design study, and analyses you select for the result window. In addition, a selection in one category may not be valid with some items in the other categories. When you select Analysis>Results, the Result Window Definition dialog box appears. In FEM mode, you can use the Results command when you want to load results directly from a NASTRAN .xdb file. To load Mechanica FEM mesh and results file, select File>Open FEM Results. The Result Window Definition dialog box consists of these main areas: • Name and title area — Enter a name and title for the result window. The name you enter appears in the list on the Display Result Window dialog box. The title appears at the bottom center of the result window. You can change the name and title at any time. Study Selection — Select the design study or analysis that the software will use to generate the result display. You can also use this area to select modes, load sets, time steps, and load steps if these are part of the analysis or design study you select. Display Type — Select the type of display for your result window. Quantity tab — Select the quantity for your result window. After you select a quantity from the first option menu, you may see additional option menus or buttons you can use to complete selecting a quantity. Display Options tab — Select various options for displaying your results. The available options depend on the display type you choose. • • • • 897 Structural and Thermal Simulation - Help Topic Collection • Display Location tab — Select specific locations on your model to display in the results window. The Result Window Definition dialog box provides a top-down approach to defining the result window. As you make selections at the top of the dialog box, different choices become active or inactive as you move down from one area to another area. The type of design study you select affects the available display types and quantities that are available. When you select a display type, that determines the quantities and display options that are available. The dialog box lets you select only valid combinations. For strategies on choosing among the various result window types, see Reviewing the Results. You can display result windows using these methods: • • If you are still working with the Result Window Definition dialog box, click the OK And Show button. If you have finished defining results and are working in the Results user interface, click the Display button on the toolbar and select result windows from the Display Result Window dialog box. As an alternative, you can use View>Display. Study Selection Area Use the Study Selection area of the Result Window Definition dialog box to select the design study/analysis that the software uses to generate the result display. The Study Selection area displays the following: • Design Study — Select the design study for which you want to display the results. The design study name appears in the display-only text box to the right of the button. In FEM mode, if you are loading results directly from a NASTRAN .xdb file, use the button to open the Load NASTRAN XDB dialog box. On this dialog box, you need to select the .xdb file from which you want the software to read the results. Analysis — Select an analysis that is part of the design study you select. Step/Combination — Select a subset of design study results. • • Step/Combination Selection The step/combination selection table displays different columns depending on the design study you select. You can select one or more subsets to include in the result display. If there is only one subset for a design study, the subset is selected by default and you cannot clear it. 898 Structural and Thermal Simulation The possible subsets in the step/combination selection table are: • Load Set/Mode — When you select a static, modal, or steady-state thermal design study, the table lists the load sets or modes used in the study. You can select one or more load set/mode combinations and provide a scaling factor for each load set/mode combination you select. The default scaling factor is 1.0. Note that there are special considerations if you use scaling with centrifugal loads. Time/Frequency/Load Step — When you select a static large deformation, dynamic frequency, dynamic time, or transient thermal analysis, the table lists the time, frequency, or load steps present in the design study. These are the user-defined steps you defined when you created the analysis. You can select one step from the list. Mode (Buckling/Prestress Modal) — When you select a buckling or prestress modal design study, the table lists the mode and buckling load factor present in the design study. You can select one mode or buckling load factor from the list. • • Display Type Area Use this area to define the way you want Mechanica to display your results. The design study or quantity you select can make one or more of the display types unavailable on the option menu. These items can appear on the Display Type option menu: • Fringe — Displays a graphical representation of your model, showing the measurements of the quantity you specify as filled color regions—each corresponding to a numeric range calculated by the analysis or design study. You can also create a contour plot using this display type. Vectors — Displays a graphical representation of your model, showing the measurements and directions of the quantity you specify as colored vector arrows. This display type is not available in FEM mode. Graph — Displays a graph of your model's behavior. Graphs display the relationship between a quantity and the graph location, such as P-loop pass, curve or edge, time, or frequency. Model — Displays your model's geometry in its original or deformed state. Model representations are useful if you want to show a simple animation of how your model deforms or if you want to show the optimized shape of your model. This display type is not available for Thermal. You can query linearized stresses for your model by selecting Model as the display type, Stress as the quantity, and Linearized as the component. When the result window displays, select Linearized Stress Query from the Info menu. • • • 899 Structural and Thermal Simulation - Help Topic Collection Quantity Tab Use the Quantity tab on the Result Window Definition dialog box to select a quantity for your result window display. The choices that appear on the Quantity tab depend on the design study and display type you select. The items that are available change immediately if you change the design study or display type. These are the items that can appear on the Quantity tab: • Quantity — Select the quantity you want to display in the result window. The menu displays only the quantities that are valid for the design study and display type you choose. The quantity you select determines which of the remaining items appears on the Quantity tab. Secondary Quantity Option Menu — Select a secondary quantity to display in the result window. This item appears if you select Fatigue, Reaction, Shell Resultant, or Beam Resultant from the Quantity option menu. Component — Select the component you want to display in the result window. The menu displays only components that are valid for the quantity you select from the Quantity menu, and only appears for certain quantities. Relative To — Select the reference for a directional component. This item appears only if you select a directional component. Graph Location — Select the type of location you want to use for your graph results display. This area appears only if you select a display type of Graph. • • • • The following additional items are available depending on the quantity you select and whether beams or shells are present in the model. These items do not appear in FEM mode. • • Include Contribution from Beams — Select the beam contributions to include in the result window definition. This area appears only if there are beams in the model. Include Contribution from Shells — Select the shell contributions to include in the result window definition. This area appears only if there are shells in the model. In addition to using the Quantity tab to define your basic result quantity, you use the Display Options tab and Display Location tab to further refine the result window display. Display Options Tab Use the Display Options tab on the Result Window Definition dialog box to determine the appearance of your results window display. Selecting one of these display types determines the options available on the Display Options tab: • • • 900 Fringe (includes contour) Vectors (not available for FEM mode) Graph Structural and Thermal Simulation • Model (not available for thermal mode) If you select a display type and then select a design study or quantity that is not compatible with that display type, Mechanica removes the display type from the option menu and displays only the valid display types for that design study and quantity combination. Display Location Tab Use the Display Location tab on the Result Window Definition dialog box to select specific locations to display in your result window. These items appear on the Display Location tab: • Display Location — Select the type of location you want to display in your result window. The options available on this menu vary depending on the design study, display type, and quantity you select. These items can appear on the menu: o All — Display all locations in the result window. This is the default value. o Beams — Display beams in the result window. o Curves — Display curves in the result window. o Surfaces — Display surfaces in the result window. o Volumes — Display volumes in the result window. o Components/Layers — Display specific components or layers in the result window. Select the Use All check box to display all Beams, all Curves, all Surfaces, all Volumes, or all Components/Layers in the result display window. • Location Selector Arrow — Use the selector arrow to select the specific entity on your model that you want to display in the results window. You can select more than one entity. If you accept the default All, the selector arrow is unavailable. To Define a Result Window 1. From the Insert menu, select Result Window or click on the Results user interface toolbar. The Result Window Definition dialog box appears. 2. In the Name text box, enter a name to identify the result window so that you can show or hide the window during your results session, or use the default. 3. In the Title text box, enter the title that you want to display at the bottom center of the result window. 4. Select the design study for which you want to display results by clicking . 5. If the design study has more than one analysis, select an analysis from the Analysis option menu. 901 (Result Window) Structural and Thermal Simulation - Help Topic Collection 6. If Mechanica displays a step/combination table below the Design Study and Analysis option menus, select a load set, mode, time step, or frequency from the table. 7. Select one of these display types from the Display Type option menu: o Fringe o Vectors o Graph o Model 8. Select a quantity from the Quantity option menu on the Quantity tab. 9. Select the Display Options tab and choose among the display options to determine the appearance and behavior of your model in the result window. 10. Select the Display Location tab and choose a location from the option menu. If you want to use all entities of a certain location type, select the Use All check box. To select a single entity, click the selector arrow. 11. To display the result window, click OK And Show. To close the dialog box without displaying the result window, click OK. To Display a Result Window 1. Select View>Display or click (Display) on the toolbar. Mechanica displays the Display Result Window dialog box. 2. If you want to display one or more result windows in the result window list, select the desired result windows. Mechanica highlights each selection you make. 3. If you want to display all result windows in the list, click Tip: If you need to deselect all result windows, click 4. Click OK. (Select All). (Deselect All). Annotating Result Windows Use the Insert>Annotation menu option to create or edit one or more annotations for a result window. You can use annotations to create notes about the results or the model, to point out specific results or features on your model, to make your result reports more meaningful to others, and so on. You can customize annotations in many ways. If you want to include text, you can surround the text with a border and a background color. You can have leader lines, with or without arrows, that point to one or more places on your model. Using the mouse sketch tools, you can be very creative by adding shapes or drawings to your annotation. Any part of the annotation can have its own unique color and you can place it anywhere on the active window. 902 Structural and Thermal Simulation When you select the Insert>Annotation menu option, the Note dialog box appears with the following options: • • • Text — Change the font, the font size, and the font color. Note Location — Select the location where you want the annotation text to appear. The annotation appears to the right of the point you select. Leader — Create one or more leaders for the annotation. You select a point on your model and Mechanica draws the leader line from the annotation to that point. Use the arrow button to put an arrow at the end of the line. If you reorient the model, the end of the leader line that is on the model moves with the model. Display Leader Arrow — Display an arrow at the end of the leader. Mouse Sketch — Create a circle, square, or multiple line shape. Style — Open the Note Style dialog box. • • • Use the Preview button at any time to apply any changes you have made without closing the dialog box. Evaluating Results The way you evaluate results depends on the type of result window you are working with. For example, if you are examining fringe plots, you are likely to be interested in the location of the quantity maximum, the value of the quantity at specific locations, how one quantity compares with another, and so forth. If you are looking at animations, you are likely to be interested in how the model deforms, the pattern of deformation at different steps, how behavior in one mode compares with behavior in another, and so forth. Here is an overview of methods and tools you can use to evaluate the different types of Mechanica results: • Fringe, contour, and vector plots — You perform three basic activities depending on how deeply you need to examine the model for the result quantity: o Adjust the legend, perform comparisons with other result windows, and, if necessary, shade or unshade your model. o Probe your model for specific information like maximum and minimum locations or how the interior of your model responded during analysis. o In FEM mode, display information about the element ID's, node ID's, and values of the result quantity at each node. Graphs — You perform two basic activities depending on how much detail you need on the quantity: o Adjust the graph, perform comparisons with other result windows. o Probe the graph to obtain more exact values for specific segments of the graph or points on the graph. Animations — You can start, stop, and control stepping and speed for the animation. You can also perform comparisons with the original model shape as well as with other animations. • • 903 Structural and Thermal Simulation - Help Topic Collection Once you have evaluated your results, you should save the result definitions for later use. At this point, you can also generate reports on your results. After you have studied your result windows, you may also find that you want to alter, copy, or delete some of them. Saving Results After you create one or more result windows, you can save these windows to a file for later use. Mechanica saves result windows in .rwd files. Saving result windows makes it easier to restore and add to your work. You can also use result windows as templates for developing result windows for multiple models. Use one of these commands on the File menu to save your result definitions: • Save — Use to save the current set of result definitions and associated views in a single .rwd file. If you defined the set of result windows in the current session and this is the first time you have saved them, Mechanica saves the windows to a file named Untitled.rwd. If the result windows displayed were saved to a named .rwd file in the past, Mechanica saves them to the named file. Save As — Use to save the current set of result definitions and associated views as a named .rwd file. When you click Save As, Mechanica displays the Save Result Windows dialog box. Use this dialog box to choose a directory and name the file. Do not include the .rwd extension in the file name you enter—Mechanica appends this automatically. When you use Save As to create a named .rwd file, the name of the .rwd file appears in the Results user interface title bar whenever you load the named .rwd file using Insert>Results Window From File as the first activity in your results session. • Save As Template — Use to save the current result window definition and some of the result window attributes as a named template as a .rwt file. When you click Save As Template, Mechanica displays the Save Results Template dialog box. Use this dialog box to choose a directory and name the file. Do not include the .rwt extension in the file name you enter—Mechanica appends this automatically. You can optionally store the legend values, model orientation, annotations, and deformed scale for the result window as part of the template. Once you create a result window definition as a template, you can create other result windows from the template by selecting the Insert>Results Window From Template command. Regardless of which approach you use, be aware that Mechanica includes paths for the study directories referenced by the result windows in the .rwd file. Mechanica uses an absolute path when it writes this information to the .rwd file, but you can instruct Mechanica to use a relative path instead through the sim_pp_path_absolute config.pro option. • 904 Structural and Thermal Simulation You can retrieve a set of saved windows using one of the load commands. Generating Reports Once you define and display result windows, you can generate reports that capture the vital points of your analyses and design studies. Mechanica provides you with the ability to print reports in a wide variety of print formats, to output reports as HTML, and to generate VRML reports. For graphs, you can generate specialized graph reports so you can study the graph sampling points in depth. Use these commands located on the File menu to generate reports: • • Print — Use to print a selected result window to a printer or to a file. Export — Use to generate each of the following report types, selectable from the associated submenu: o Image — Use to generate printed images. This command is identical to File>Print. o Direct VRML — Use to export a single fringe plot at a time in VRML format. o HTML Report — Use to export result windows to an HTML file for web viewing. o Graph Report — Use to export a graph report file for a single, selected graph. The output file is a text file. o Excel — Use to export a single graph for viewing in Microsoft Excel. The output file is a .xls file. o MPEG — Use to export a single animated result window to an MPEG file. When preparing to generate reports, you may want to pay particular attention to the aesthetics of the result windows you are printing or exporting. You should also consider formatting the result windows to emphasize the aspects of the result you want to focus on when you share the information with others. For example, blended or dark background colors may make it difficult to read some of the information, depending on the quality of your printer. You may want to eliminate excess text from the result window by using Format>Result Window and turning off labels. You may want to work with the Format Legend dialog box to ensure that you are using the best color scale to reflect what takes place in a fringe plot. You can highlight parts of your results and add information using annotations. FEA Parameters Creating FEA Parameters Mechanica FEM mode postprocessing supports the creation of parameters based on a model's finite element analysis. You can use created parameters to drive model geometry by including them in relations and regenerating the model. After you run an analysis on your model, you can create different types of parameters for any combination of analysis tests, applied analysis, or selected model 905 Structural and Thermal Simulation - Help Topic Collection geometry, provided you obtain your results from an .frd file. To obtain results from an .frd file, you must use the File>Open FEM Results command or run a FEM solver online and look at the results available immediately after the run completes. You cannot create FEA parameters if you select Analysis>Results instead of using one of these two methods. You access parameter creation and management commands by selecting Parameters from the RESULTS menu displayed when you use either of the two methods just discussed. You create the parameters you want by selecting the Create command and using the Define Parameter dialog box. You can specify parameters based on multiple analyses, multiple modes, and multiple geometric entities. If you are working with a shell model, you can define parameters based on a particular shell side. Mechanica only updates parameters when you enter the postprocessor after successfully solving the FEA program online. To Create Parameters You can create parameters for your results provided you obtain your results from an .frd file. To obtain results from an .frd file, you must use the File>Open FEM Results command or run a FEM solver online and look at the results available immediately after the run completes. You cannot create parameters if you select Analysis>Results instead of using one of these two methods. 1. Select File>Open FEM Results and select the result file for the current model. As an alternative, perform an online FEM solver run. Mechanica displays the RESULTS menu. 2. Select Parameters>Define Param from the RESULTS menu. The Define Parameter dialog box appears. 3. 4. 5. 6. Enter a name for the parameter in the Name window. Select the type of parameter from the Type option menu. Select the analysis from the Analysis list. If you selected a modal analysis, select the desired modes from the Mode list. 7. Select the desired quantity from the Result option menu. 8. Select the desired component from the Components option menu. 9. If the model includes shell elements, select the shell side for the parameter from the Shell Side options. 10. From the Reference menu, select either the entire model or specific geometric entities. You can choose different entity types for the same parameter. Be aware that Mechanica bases the parameter on the selected geometry only. 11. Select the reference coordinate system from the Coord System option menu and indicate the coordinate system type. 12. Click Apply. Mechanica creates the parameter. 906 Structural and Thermal Simulation Analysis Statistics Reviewing FEM Analysis Statistics After you run an analysis on your meshed model using a finite element analysis program, you can review thermal, structural, or modal analysis statistics, provided you obtain your results from an .frd file. To obtain results from an .frd file, you must use the File>Open FEM Results command or run a FEM solver online and look at the results available immediately after the run completes. You cannot review statistics if you select Analysis>Results instead of using one of these two methods. Mechanica can output the following statistics from the analysis results: • • • • • • • • • applied analyses type of result—quantities such as von Mises stress, heat flux, strain energy, for example side of the shell elements the analysis results data were calculated from—top, bottom, average of both, or both maximum value of the result on the model minimum value of the result on the model average value of the result on the model variance of the result on the model location of result maximum on the model location of result minimum on the model Mechanica can generate these statistics for the entire model or for selected parts, surfaces, edges, vertices, or hard points. For edges, Mechanica provides the additional option of generating a graph of values measured along the edges. Mechanica also supports mid-node data processing for parabolic elements. You specify the statistics you want using the Postprocessing Info dialog box. You can request that Mechanica output analysis statistics to an information window on your screen, to a readable ASCII text file, or to both the screen and a file. To Display or Output Analysis Statistics You can display or output analysis statistics from your run provided you obtain your results from an .frd file. To obtain results from an .frd file, you must use the File>Open FEM Results command or run a FEM solver online and look at the results available immediately after the run completes. You cannot display or output analysis statistics if you select Analysis>Results instead of using one of these two methods. 1. Select File>Open FEM Results and select the result file for the current model. As an alternative, perform an online FEM solver run. Mechanica displays the RESULTS menu. 2. Select Info from the RESULTS menu. 907 Structural and Thermal Simulation - Help Topic Collection The Postprocessing Info dialog box displays. 3. Select the analysis from the Analysis list. 4. If you selected a modal analysis, select the desired modes from the Mode list. 5. Select the desired Structure or Thermal quantity from the Result option menu. 6. Select the desired component from the Components option menu. 7. If the model includes shell elements, select the shell side for the statistics from the Shell Side options. 8. From the Reference menu, select either the entire model or specific geometric entities. You can choose different entity types for the same statistical report. Mechanica includes analysis statistics on the selected geometry only. 9. Select the reference coordinate system from the Coord System option menu and indicate the type. 10. Select the display or output method as follows: o If you want to display the statistics in an information window on your screen, select Screen. o If you want to output the statistics to a file, select File and type a file name in the associated text box. o If you want both a displayed version and printable output, select Both and type a file name for the printable output in the associated text box. 11. Click the Statistics button. If you selected Screen or Both as an output method, an information window appears displaying the analysis statistics. 12. Click Done. Mechanica closes the dialog box. Hard Point Reports Evaluating FEM Hard Point Reports After you run an analysis on your meshed model using a finite element analysis program, you can generate a report of a selected quantity at one or more hard points on your model, provided you obtain your results from an .frd file. To obtain results from an .frd file, you must use the File>Open FEM Results command or run a FEM solver online and look at the results available immediately after the run completes. You cannot generate hard point reports if you select Analysis>Results instead of using one of these two methods. Mechanica can report values based on the following: • • type of result—Structure or Thermal quantities such as von Mises stress, heat flux, strain energy, for example side of the shell elements the analysis results data were calculated from—top, bottom, average of both, or both. This type of reporting is available for structural and modal analyses only. Mechanica reports values for the selected quantity in all three translational and rotational directions at each of the hard points you select. Hard point reports are 908 Structural and Thermal Simulation useful for recording the exact analysis data for the quantity you choose across all the hard points in your model. You specify the statistics you want using the Postprocessing Report dialog box. You can request that Mechanica output hard point reports to an information window on your screen, to a readable ASCII text file, or to both the screen and a file. To Display or Output Hard Point Reports You can display or output hard point reports from your run provided you obtain your results from an .frd file. To obtain results from an .frd file, you must use the File>Open FEM Results command or run a FEM solver online and look at the results available immediately after the run completes. You cannot display or output hard point reports if you select Analysis>Results instead of using one of these two methods. 1. Select File>Open FEM Results and select the result file for the current model. As an alternative, perform an online FEM solver run. Mechanica displays the RESULTS menu. 2. Select Report from the RESULTS menu. The Postprocessing Report dialog box appears. 3. Select the analysis from the Analysis list. 4. If you selected a modal analysis, select the desired modes from the Mode list. 5. Select the desired quantity from the Result option menu. 6. If the model includes shell elements, select the shell side for the report from the Shell Side options. 7. From the Reference menu, select either the entire model or specific hard points. 8. Select the reference coordinate system from the Coord System option menu and indicate the type. 9. Select the display or output method as follows: o If you want to display the report in an information window on your screen, select Screen. o If you want to output the report to a file, select File and type a file name in the associated text box. o If you want both a displayed version and printable output, select Both and type a file name for the printable output in the associated text box. 10. Click the Report button. If you selected Screen or Both as an output method, an information window appears displaying the hard point report. 11. Click Done. Mechanica closes the dialog box. 909 Structural and Thermal Simulation - Help Topic Collection Supported FEA Solvers The following table lists FEA solvers that are currently supported by Mechanica in FEM mode. Solver ANSYS MSC/NASTRAN Version 8.0 2004 To Generate an Edge Graph You can generate a graph of results on a model edge provided you obtain your results from an .frd file. To obtain results from an .frd file, you must use the File>Open FEM Results command or run a FEM solver online and look at the results available immediately after the run completes. You cannot generate edge graphs if you select Analysis>Results instead of using one of these two methods. 1. Select File>Open FEM Results and select the result file for the current model. As an alternative, perform an online FEM solver run. Mechanica displays the RESULTS menu. 2. Select Info from the RESULTS menu. The Postprocessing Info dialog box displays. 3. Select the analysis from the Analysis list. 4. If you selected a modal analysis, select the desired modes from the Mode list. 5. Select the desired quantity from the Result option menu. 6. Select the desired component from the Components option menu. 7. If the model includes shell elements, select the shell side for the parameter from the Shell Side options. 8. From the Reference menu, click the selector arrow to select a single edge or a contiguous series of edges. 9. Select the display or output method as follows: o If you want to display the edge graph in an information window on your screen, select Screen. The edge graph appears in a graph window on your screen accompanied by the Print dialog box, which enables you to print the graph to a printer or plotter. o If you want to output the statistics to a file, select File and type a file name in the associated text box. Mechanica outputs the graph information to a .dat file, which you can display in a Microsoft Excel spreadsheet. o If you want both a displayed version and printable output, select Both and type a file name for the printable output in the associated text box. 10. Click Done. Mechanica closes the dialog box. 910 Structural and Thermal Simulation To Display or Output Parameters If you want to display or output parameters for your results, you must obtain your results from an .frd file. To obtain results from an .frd file, you must use the File>Open FEM Results command or run a FEM solver online and look at the results available immediately after the run completes. You cannot display or output parameters if you select Analysis>Results instead of using one of these two methods. 1. Select File>Open FEM Results and select the result file for the current model. As an alternative, perform an online FEM solver run. Mechanica displays the RESULTS menu. 2. Select Parameters>Show Param from the RESULTS menu. The FEM PARAMS menu appears. 3. Select the display or output method as follows: o If you want to display the parameters in an information window on your screen, select Screen. o If you want to save the parameters to a file, select File. o If you want both displayed and stored versions of the parameters, select Both. The SEL PARAM menu appears. 4. Use the SEL PARAM menu to select the parameters that you want to display or save. 5. Complete the selection process and close the SEL PARAM menu and display or save the parameter information. To Delete Parameters You can delete a model's obsolete FEA results-based parameters as desired. If you do so, be sure to delete or edit any relation that references deleted parameters. If you want to create or delete parameters for your results, you must obtain your results from an .frd file. To obtain results from an .frd file, you must use the File>Open FEM Results command or run a FEM solver online and look at the results available immediately after the run completes. You cannot create or delete parameters if you select Analysis>Results instead of using one of these two methods. 1. Select File>Open FEM Results and select the result file for the current model. As an alternative, perform an online FEM solver run. Mechanica displays the RESULTS menu. 911 Structural and Thermal Simulation - Help Topic Collection 2. Select Parameters>Delete Param from the RESULTS menu. The SEL PARAM menu appears. 3. Use the SEL PARAM menu to select the parameters to delete. 4. Complete the selection process and close the SEL PARAM menu. Mechanica deletes the selected parameters. Shell Side If your model's mesh comprises shell elements, you can generate analysis statistics, hard point reports, and parameters based on a specific area: • • • • Top — Generate analysis statistics, reports, or parameters based on the top side of the shell elements. Bottom — Generate analysis statistics, reports, or parameters based on the bottom side of the shell elements. Average — Generate analysis statistics, reports, or parameters based on the average value of the top and bottom sides of the shell elements. Both — Generate analysis statistics, reports, or parameters based on both the top and bottom sides of the shell elements. Outputting FEM Analysis Statistics You can output analysis statistics using the Report command on the RESULTS menu. When you select this command, the Postprocessing Info dialog box appears. The Results user interface, if active, closes and the Pro/ENGINEER user interface again becomes visible, showing a meshed view of your model. Tip: To reactivate the Results user interface, select the Visualize command on the RESULTS menu when you finish outputting analysis statistics. The Postprocessing Info dialog box contains these items: • • • • Analysis — Select one or more of the model's analyses. If you select multiple analyses, Mechanica outputs the statistics for all the analyses in a single report or graph. Mode — Select one or more modes. This option is only available for modal analysis statistics. Result — Select one of the result quantities available for the Structure or Thermal analysis. Component — Select one of the components available for the quantity you selected. If you want to generate an edge graph, you can select multiple components. In this case, all the entities you select in the Reference field must be edges. Shell Side — For shell models, select the shell side for which to generate statistics. Reference — Select the whole model or click the selector arrow to specify one or more geometric entities for which to generate statistics. The geometric • • 912 Structural and Thermal Simulation • • entities you can select from are surfaces, edges, vertices, and hard points. If your model is an assembly, you can also select individual parts. Coord System area — Select a coordinate system to use as a reference for showing results. Also, specify its type as follows: o Cartesian — Cartesian coordinate system (X, Y, Z). o Cylindrical — Cylindrical coordinate system (R, Theta, Z). o Spherical — Spherical coordinate system (R, Theta, Phi). Output to area — Select the way you want Mechanica to present the output. o Screen — Presents the specified analysis statistics in an information window on your screen. o File — Routes the specified analysis statistics to an ASCII file whose name and path you specify in the associated text box. o Both — Provides both screen and file output. Use the four buttons at the bottom of the dialog box to indicate the type of analysis statistics you want to review. These buttons are as follows: • • • Edge Graph — Displays an edge graph for an edge or connected chain of edges you specified in the Reference field. This button becomes inactive if you select anything other than connected edges in the Reference field. Statistics — Displays the analysis statistics as specified on the dialog box. This button becomes inactive if you select more than one component in the Component field. Point Data — Displays analysis statistics for a specific point on the model. When you click this button, Mechanica asks you to select a single point on your model. You can select an existing point or click any location on your model to get data for that location. The Point Data button becomes inactive for certain quantities. It also becomes inactive if you select multiple components in the Component field. • Done — Closes the dialog box. Output of Statistics and Reports for Thermal Analyses The FEM mode postprocessor supports the output statistics and hard point reports for thermal analyses based on these quantities: • • • Temperature Heat Flux Temperature Gradient 913 Structural and Thermal Simulation - Help Topic Collection Output of Statistics and Reports for Structural or Modal Analyses The FEM mode postprocessor supports the output statistics and hard point reports for structural or modal analyses based on these quantities: • • • • • Stress Strain Thermal Strain Displacement Reaction Force Limitations of Averaging in Results Mechanica can average result quantities across element boundaries, but only where it is a logical extension of the results. Derivative values will not be averaged in the following instances: • If the properties on all sides of an element boundary are not homogeneous. The software does not check the actually properties, but the names of the properties. In other words, even if ShellProp1 and ShellProp2 are identical , Mechanica will not average the values across the shells' common edge. If more than two elements are connected. For example, if there is a beam along the edge of two shells, then the software will not average derivative quantities across that edge. If there is a discontinuity in the shell edges. That is, two shells must meet at a common line or plane for the quantities to be averaged. this also applies to beams. • • Graphing Statistics You can generate analysis statistics for the entire model or for selected surfaces, edges, vertices, or points. If you select an edge or connected series of edges as a reference on the Postprocessing Info dialog box, you also can display a graph of the quantity as measured at those edges. To help you compare edge behavior, you can select components for your quantity. When you select multiple components, the resulting graph shows each component's curve in a different color, and provides a legend to help you distinguish the components. You can specify whether you want Mechanica to display the edge graph on your screen, output the edge data to a file, or both. When Mechanica displays your edge graph on-screen, it provides a dialog box that lets you output the graph to any of several printer types. If you choose to output the edge graph data to a file, Mechanica generates a .dat file which you can open and format in a Microsoft Excel spreadsheet. 914 Structural and Thermal Simulation FEA Parameter Types The FEM mode postprocessor supports the following parameter types: • • • • • • • Maximum Minimum Average Variance Point of max Point of min Value (at a specific location on the model) Outputting Hard Point Reports You can output hard point reports using the Report command on the RESULTS menu. When you select this command, the Postprocessing Report dialog box appears. The Results user interface, if active, closes and the Pro/ENGINEER user interface again becomes visible, showing a meshed view of your model. Tip: To reactivate the Results user interface, select the Visualize command on the RESULTS menu when you finish outputting hard point reports. The Postprocessing Report dialog box contains these items: • • • • • • Analysis — Select one or more analyses. If you select multiple analyses, Mechanica outputs the hard point data for all the analyses in a single report. Mode — Select one or more modes. This option is only available for modal analyses. Result — Select one of the result quantities available for the Structure or Thermal analysis. Shell Side — For shell models, select the shell side for which to generate statistics. Reference — Select the whole model to get a report for all hard points in the model or click the selector arrow to specify individual hard points. Coord System area — Select a coordinate system to use as a reference for the report. Also, specify its type as follows: o Cartesian — Cartesian coordinate system (X, Y, Z). o Cylindrical — Cylindrical coordinate system (R, Theta, Z). o Spherical — Spherical coordinate system (R, Theta, Phi). Output to area — Select the way you want Mechanica to present the output. o Screen — Presents the report in an information window on your screen. o File — Routes the report to an ASCII file whose name and path you specify in the associated text box. o Both — Provides both screen and file output. • Use the Report button at the bottom of the dialog box to generate the hard point report. The report lists the values for each hard point, as measured in reference to the coordinate system you selected. The report provides a value for each translational and rotational axis. 915 Structural and Thermal Simulation - Help Topic Collection Creating Statistics, Parameters, or Reports from Shell Elements You can gather statistics, define parameters, and generate hard point reports from the top or bottom sides of shell elements. The top side of a shell element is defined as the surface facing in the direction of the element's positive normal vector, and is indicated by a yellow arrow originating from it. The shell element's positive normal vector is calculated by applying the right-hand rule to the shell element's nodes. Stresses and strains on the top side of shell elements can differ from those on the bottom side of shell elements because of the effects of shell element bending. Defining Parameters Based on Results You can define parameters using the Parameters>Define Parameter command on the RESULTS menu. When you select this command, the Define Parameter dialog box appears. The Results user interface, if active, closes and the Pro/ENGINEER user interface again becomes visible, showing a meshed view of your model. Tip: To reactivate the Results user interface, select the Visualize command on the RESULTS menu when you finish working with parameters. The Define Parameter dialog box contains these items: • • • • • • • • • Name — Enter a name for the parameter. Type — Select the parameter type. Analysis — Select one or more of the model's analyses. If you select multiple analyses, Mechanica creates the parameter based on all the analyses. Mode — Select one or more modes. This option is only available for modal or dynamic frequency analysis statistics. Result — Select one of the result quantities available for the analysis. Component — Select one of the components available for the quantity you selected. You can select multiple components. Shell Side — For shell models, select the shell side for which to generate statistics. Reference — Select the whole model or click the selector arrow to specify one or more same-type geometric entities for which to define the parameter. Coord System area — Select a coordinate system to use as a reference for the parameter. Also, specify its type as follows: o Cartesian — Cartesian coordinate system (X, Y, Z). o Cylindrical — Cylindrical coordinate system (R, Theta, Z). o Spherical — Spherical coordinate system (R, Theta, Phi). Generating Point Data You can generate analysis statistics for the entire model or for selected parts, surfaces, edges, vertices, or hard points. In addition, you can use the Point Data button on the Postprocessing Info dialog box to gather information on model locations not directly associated with a geometric entity in the mesh. For example, 916 Structural and Thermal Simulation you can review a quantity at locations in the middle of elements. When it generates a Point Data report, Mechanica interpolates the point value for the selected location in relation to the corner nodes of the element where the point is located. Be aware of these guidelines when preparing to generate Point Data reports: • • • You You and You can obtain point data for all Thermal quantities. can generate point data for only two Structure quantities—displacement reaction force. cannot select multiple components for the quantity. You can specify whether you want Mechanica to display the Point Data report on your screen, to output the report to a file, or both. Since you typically use Point Data reports for on-the-fly examination of your model, displaying the report on your screen is the most common of these choices. To Annotate a Result Window Steps 4 through 8 of this procedure are optional. 1. Select Insert>Annotation. The Note dialog box appears. 2. Enter the annotation text in the text box. 3. Click the Note Location button, and then click the mouse on the result window where you want to place the annotation. The text you entered appears in the result window. 4. To include leader lines, click , and then click the point on your model where you want the leader line to start. Mechanica draws the leader line from the point you click to the closest corner of the annotation. 5. To display or turn off the leader arrow at the end of the leader line, select or clear the Display Leader Arrow check box. 6. To draw a circle, square, or multiline shape on the result window, select , , or and use your mouse to create the desired shape. 7. To make changes to the font, text box, leader, arrow, or mouse sketch styles, click the Style button. The Note Style dialog box appears. 8. When you finish making all changes to the annotation and styles, click OK. 917 Structural and Thermal Simulation - Help Topic Collection To Save a Result Window This procedure assumes you are in the File menu. 1. Select Save As. The Save Result Windows dialog box appears. 2. Enter a name on this dialog box for the file in which you want Mechanica to save your result window definitions. Mechanica automatically gives the file an .rwd extension. To Edit a Result Window 1. Select Edit>Result Window. The Result Window Definition dialog box appears with the selections you previously made for this result window. 2. Change your previous selections as desired. To Format a Fringe, Contour, Vector, Model, or Animation Result Window This procedure assumes that you have defined and displayed one or more result windows. Note that all toggles mentioned below are on by default. 1. Select the result windows you want to format. Tip: If you want to apply the same window format to more than one result window, press the SHIFT key and click each of the windows you want. 2. Select Format>Result Window. Mechanica displays the Format Result Window dialog box. 3. Select a window background from the Background Color option list. 4. If you want to toggle titles at the bottom of the selected result windows, click Title. 5. If you want to toggle a descriptive label at the top left corner of the selected result windows, click Label. 6. If you want to toggle the view coordinate system (WCS) for the selected result windows, click WCS. 7. If you want to toggle legends for the selected windows, click Legend. 918 Structural and Thermal Simulation Note: If you do not turn legends on, it is more difficult to interpret color values for your model, and you might need to use the Dynamic Query command to gain an understanding of your results. There are no legends for model displays or unfringed animations. 8. If you have selected a contour result window only and want to toggle contour labels, click Contour Labels. 9. Click OK. To Customize Annotation Styles This procedure assumes that you clicked the Styles button on the Note dialog box. The steps in this procedure are optional. 1. To change the font, select a font from the Style option menu. 2. To change the size of the font, enter a number in the Height scroll box. 3. To change the color of the font, click and select a color. 4. To surround the text with a border, select Draw Border. 5. Select Background, Solid, or None from the Color Fill Type option list. 6. If you chose Solid, click and select a color. 7. To create the leader line: o Select the leader line thickness from the option menu. Click to select the leader line color. Click the desired button in the Arrow Style area to select the leader arrow appearance. 8. Select the thickness of the mouse sketch lines from the option menu and click o o to select a color for the lines. 9. Click OK to return to the Note dialog box. Adjusting Color Scale for Fringe, Contour, and Vector Legends Use the color scale controls on the Format Legend dialog box to determine the coloring of your model and how many levels the legend contains. You can adjust the following: • • • Levels — Use to select or enter the number of levels you want in the legend. This, along with Minimum and Maximum, determines the amount of detail in your plot. You can select any number between 1 and 9. Color Spectrum — Use to select the color spectrum you want. You can select Structural, Thermal, Huescale, Grayscale, Colorset1, Colorset2, Rainbow, Red Yellow Green, Fatigue, or Mechanica Classic. Invert Color Scale — Use to invert the color spectrum you have chosen. For example, an inverted Structural spectrum uses red as a minimum value and dark blue as a maximum—the opposite of the normal Structural spectrum. 919 Structural and Thermal Simulation - Help Topic Collection Controlling Animations Mechanica provides commands that let you control how an animation progresses. You can execute these commands either from the View menu or through toolbar buttons. The animation controls are: • Start — Start an animation. This command initializes the animation at the frame currently active in the result window. The animation moves without pause through the remaining steps in the animation. The animation repeats until you stop it. Stop — Stop an animation. This command halts the animation at the current frame. Step Forward — Move forward through an animation frame by frame. Step Back — Move backward through an animation frame by frame. Animation Playback Speed Control — Speed up or slow down an animation by moving the slider on the toolbar in the appropriate direction. This option is not available on the View menu. • • • • Adjusting Fringe, Contour, and Vector Legends Use Format>Legend to adjust the appearance and range of values for a fringe, contour, and vector plot. When you select this command, Mechanica displays the Format Legend dialog box. The Format Legend dialog box includes: • Maximum — Use to set the maximum value for the legend. You must select a value that lies between the maximum and minimum of the quantity as determined by the analysis or study. These values appear as the default values in the Format Legend dialog box's Maximum and Minimum text boxes. Depending on how you set the maximum and minimum, Mechanica may redistribute the intervening scale. The maximum and minimum values you enter in the Format Legend dialog box determine how the shading will be graded for your model. You can use these values to get a better idea of how a particular range of values is distributed over your model. • • • Minimum — Use to set the minimum value for the legend. You must select a value that lies between the maximum and minimum of the quantity as determined by the analysis or study. Color Scale — Use the controls in this area to determine the color spectrum of your model and how many levels the legend contains. Show View Min/Max — Use to toggle the minimum and maximum values shown in the result window label on and off. The minimum and maximum values appear in gray on the legend. Toggling this control off streamlines the appearance of your result window. Show Legend — Use to toggle the legend on and off. • In addition to adjusting the minimum and maximum values, you can also adjust individual legend values through the Edit>Legend Value command. 920 Structural and Thermal Simulation Regardless of which method you used to adjust a legend, you can return a legend to its original state through the Utilities>Reset Legend command. Examining Model Interiors for Fringe and Contour Plots Mechanica provides two tools—cutting surfaces and capping surfaces—that let you get information on how the interior of your model behaves. You can access these tools by using Insert>Cutting/Capping Surfs to invoke the Results Surface Definition dialog box, a dialog box that enables you to define the placement and nature of cutting and capping surfaces. You can create cutting and capping surfaces on: • • a non-animating fringe plot a non-animating contour plot with at least one solid element Cutting surfaces and capping surfaces differ in these regards: • • A cutting surface is a plane that slices your model and trims both the top and bottom away. You can define more than one cutting surface for your model. A capping surface is a plane that slices your model and trims either the top or bottom away. You can only define one capping surface for your model. Here is an illustration of the difference: The left result window above shows a model with multiple cutting surfaces. The most valuable of these is the first from the bottom, which indicates how far the high stress (red) area intrudes into the interior of the model. The right result window shows the same model with a capping surface that removes the upper two thirds of the model. Cutting and capping surfaces are particularly useful for thick models, models that may have significant variations of interior stress, or models that may undergo 921 Structural and Thermal Simulation - Help Topic Collection unseen deformations. Consider zooming in on areas of interest for cutting or capping surfaces to get a more exact idea of how quantities behave inside your model. If you find that a cutting or capping surface is not giving you the information you need, you can modify or delete it. Example: Comparing Animation Stages for the Same Model To compare animation stages, use Insert>Result Window to define and display the basic animation result window. Then, select the animation result window and use Edit>Copy to replicate the result definition until you have one definition for each frame you are interested in. Tip: You may want to change the result window title for each replication so you will be able to distinguish one result window from the next. To do so, enter a new title on the Result Window Definition dialog box. Be sure all animation result windows are displayed. Select the first window and use View>Step Forward to find the first frame you are interested in. Select the second window and use Step Forward to find the next frame you are interested in. Repeat this process for all result windows until you have set all the result windows to different stages. Here is an example of a comparison between Step 9 and Step 15 for the same model, showing the different deformations for the two steps: You can use animation comparisons like the one above to help determine when areas of the model move into higher quantity ranges and when certain deformations begin 922 Structural and Thermal Simulation to take place. Since you can also see this behavior by simply stepping through an animation, you may find that this type of comparison is primarily useful for generating formal reports. Example: Comparing Mode Animations for the Same Model To compare modes, define and display animation result windows for each mode you are interested in studying. Be sure to specify the same number of frames for each result definition. The closer you make the definitions, the better the correlation and synchronization between the animations. For each animation result window, select Format>Legend and ensure that all the result windows have the same format and number of legends. Then, select all the animation result windows. To do so, use the SHIFT key and mouse to select the windows you want. Use View>Step Forward and View>Step Back to move the animations through the frames. Compare the animations frame by frame to note the different patterns of stress induced by each mode. Here is an example of a comparison between Mode 10 and Mode 6 for the same model, showing the different deformations of the two modes as well as the stress distribution for the two modes: Note: Both windows use the same number of frames and show the same frame of the animation, forming the basis of comparison. 923 Structural and Thermal Simulation - Help Topic Collection Determining the Minimum and Maximum Locations for a Quantity Mechanica provides several commands that show you where minimum and maximum values for the quantity are located. Use the following commands on the Info menu to determine minimums and maximums: • View Max — Use to find the location of the quantity maximum for the model view in the result window. If you rotate your model, move it, or change its size, you need to select the View Max command again to obtain a new maximum. View Min — Use to find the location of the quantity minimum for the model view in the result window. If you rotate your model, move it, or change its size, you need to select the View Min command again to obtain a new minimum. Model Max — Use to find the location of the quantity maximum for the model as a whole. If Mechanica does not display a value, you may need to rotate your model to find where the value lies. Model Min — Use to find the location of the quantity minimum for the model as a whole. If Mechanica does not display a value, you may need to rotate your model to find where the value lies. • • • When you select any of these commands, Mechanica marks each location with a small gray triangle icon and displays the value next to the icon. A triangle pointing up indicates a maximum. A triangle pointing down indicates a minimum. If the plot has a maximum or minimum at multiple locations, Mechanica marks one location and displays a message box telling you there are more. When you have finished reviewing a value, you can clear it from the result window for better model visibility. Modifying and Deleting Cutting and Capping Surfaces Use these commands on the Edit menu to modify or delete cutting and capping surfaces: • • Cutting Surf and Capping Surf — Use to modify the position or orientation of a specific cutting surface or capping surface in your result window. Delete Cutting Surf and Delete Capping Surf — Use to delete a specific cutting surface or capping surface in your result window. 924 Structural and Thermal Simulation Copying and Deleting Result Windows Once you create a result definition, you may want to copy it as a means of efficiently replicating result windows for a study. You may also find that you want to delete a result window you defined. To perform these tasks, you use commands from the Edit menu: • Edit>Copy — Use to make a copy of the definition of the currently selected result window. Mechanica assumes that the definition you are creating through the Copy command is for the same design study. It also assumes that the new definition references the same analysis, mode, and load combination as the original definition. Thus, when you select this command, Mechanica prompts you for a new result window name, and then immediately opens the Result Window Definition dialog box. You can change any settings that you want. Once you enter a window name on the Create Result Window dialog box, you cannot cancel this operation, so if you decide you do not want the copy, display and select the copy. Then, use Edit>Delete to delete it. One use of the Copy command is to create a result window that acts as a simple template for other result window definitions you want to create for the same design study. If you use Copy this way, Mechanica is able to skip some of the definition steps, making the general process of defining result windows quicker. • Edit>Delete — Use to delete the selected result window. If no result window is currently selected, the Selection dialog box appears and you can select one or more result windows from the list to delete. Clearing Query Tags from a Result Window During extensive model querying, your model may become cluttered with query tags. Query tags consist of triangular point marks and associated value labels. Once you have studied the queried values, you may want to restore your model view to its original appearance. To do so, use the following commands on the View menu: • • Clear Query Tags — Use to delete query tags one by one. This function can be useful if you just want to remove some of the tags. For example, you may want to generate a report with only some of the query tags still in place. Clear All Query Tags — Use to delete all query tags at once. This function can be useful if you want to clear your model view as efficiently as possible. Comparing Animations Comparing animations helps you make important decisions about your model or models. One of the most common reasons you compare animations is to help you determine which of several models shows the most desirable behavior pattern for the quantity, mode, and so forth. 925 Structural and Thermal Simulation - Help Topic Collection You can also compare animations of the same model to: • Learn how the animated shapes compare with the original model shape. Use the View>Overlay toggle to superimpose a wireframe of the original model over the animation of the model. The Overlay command is only available for unfringed animations. Learn how the model behaves for different analysis conditions. In this case, you animate the same model using different load sets, constraint sets, or analysis types to get a better idea of overall reaction to multiple environments. Learn how the model behaves for different modes. This shows you which modes are likely to be a problem and how a quantity distributes at the same stage for different modes. To learn more, see Example: Comparing Mode Animations for the Same Model. Learn how the model behaves at different stages of the animation. This shows you how a quantity distributes at different times or how resonance behaves over time. To learn more, see Example: Comparing Animation Stages for the Same Model. • • • Displaying Element IDs, Node IDs, and Result Values (FEM mode) For fringe, contour, and vector result windows, you can display element IDs, node IDs, and result values for your model. Viewing values for individual elements provides you the ability to closely examine the behavior of a quantity by studying individual values in the areas of interest. You display the information by using the following commands in the Info menu: • • • Display Element IDs — Turn element IDs on and off for a result window. Display Node IDs — Turn node IDs on and off for a result window. Display Result Values — Turn a display of node values on and off for a result window. This command is only available for the following quantities: o Displacements o Rotations o Reactions o Temperatures Note Style Dialog Box When you click the Style button on the Note dialog box, the Note Style dialog box appears with the following options: • Font — Use this area to define the font for your annotation. You can define the following: o Style — Select the font style for your annotation. Click the color button to define the color of the font. o Height — Enter the font height in the scroll box. Text Box — Use this area to define the text box properties: o Draw Border — Surround the annotation text with a box. • 926 Structural and Thermal Simulation • • Color Fill Type — Select from Background, Solid, or None. If you select Solid, click the color button to define the color of the text box. Leader — Use this area to define the appearance of the leader and arrow. You can define the following: o Color and Thickness — Select the leader thickness from the option menu and click the color button to define the leader color. o Arrow Style — Click one of the style buttons to define the arrow style. Mouse Sketch — Define the color and thickness of the mouse sketch lines. o Click the Preview button to view your changes as you make them, or click OK to close the dialog box. Reviewing and Altering Result Windows Once you create result definitions, you can use several commands to review or alter a definition. To perform these tasks, you use commands from the Info and Edit menus: • Info>Review Result Window — Review the key specifications in the result definition for the selected result window. Mechanica displays a version of the following message box based on your result definition: You cannot edit the information in this box. If you need more details on the definition, use Edit>Result Window to see the original version of the Result Window Definition dialog box. • Edit>Result Window — Review and change the result window definition through the Result Window Definition dialog box. This command does not enable you to change analyses, mode number, or load combination. To change these items, use Edit>Change. If no result window is currently selected, the Selection dialog box appears. This dialog box allows you to select an existing result window. You can also copy and delete result windows. 927 Structural and Thermal Simulation - Help Topic Collection Format Result Window Dialog Box When you select Format>Result Window, the Format Result Window dialog box appears. Use this dialog box to define the visual characteristics of the highlighted result windows. The Format>Result Window command is not available for graphs. The options available on the Format Result Window dialog box depend on the display type for your result window. For example, if you select Format>Result Window for a fringe plot, the active options include such items as coordinate systems, title, legend, and so forth. But, the active options would not include an item like contour labels, which is only available for contour plots. The Format Result Window dialog box includes the following toggles and option menus: • • • • • • • • • • Background Color — Controls the background color for the result window. Title — Displays a title at the bottom of the result window. Label — Displays a result description in the upper left corner of the result window. The contents of this area depend on the type of analysis and result window. Coordinate Systems — Displays the view coordinate system (VCS) of the model in the lower left corner of the result window. Legend — Displays the result window legend. This option is not available for e Model display type or unfringed animations. Display Triad — Displays the triad icon in the lower left corner of the result window. Contour Labels — Displays the contour labels for contour result displays. If you want to reset contour labels, use Utilities>Relabel Contour. Loads — Displays load icons where they are present Constraints — Displays constraints icons where they are present. Annotations — Displays annotations you define. You can use the Format>Result Window command to control the display format for multiple windows at once. To do so, use the SHIFT key and left-click to select the windows you want. Then select Format>Result Window. Mechanica tailors the Format Result Window dialog box to include only characteristics that are common to all of the selected windows. Querying Quantities for Fringe Plots and Linearized Stress Analyses Mechanica provides two commands that let you determine a quantity at a particular location or locations on your model. One command operates for unanimated fringe plots and the other is specific to plots generated from linearized stress analyses. Use these commands on the Info menu for specific queries: • Dynamic Query — Use to find quantity values at any point on your model. You can use this command to pinpoint exact locations or to study a continuously updated quantity as you use your mouse to scan your model. 928 Structural and Thermal Simulation If you use the command to label a series of locations on your model with their calculated values, you may want to clear these values from the result window after you study them to restore a clean model view. • Linearized Stress Query — Use to review a report of extrapolated values linearized between two points you select. The report gives you information on the membrane, bending, peak, and total stresses relative to a coordinate system defined by the two points. You can base the report on a variety of standard measures like von Mises stress or component stress. Displaying Result Windows Use View>Display or the Display button on the toolbar to display the result windows you select from the Display Result Window dialog box. You can display up to 16 result windows at once. After you select Display, the dialog box disappears, and Mechanica displays the result windows you selected in the work area. If you want to change aspects of how the model appears in a result window, you can adjust the view. If you are looking at a graph result window generated for a function load, only some of the view controls are available. Saved Views Use the View>Saved Views menu option or the Saved Views button on the toolbar to change the orientation of your model to a saved view or to save the current view. When you select the View>Saved Views menu option, the Saved Views dialog box appears with the following options: • • • Saved view list — Lists the views you save in Pro/ENGINEER or results. Set — Repositions your model to the orientation of the saved view that you select from the list. Save — Saves the current orientation of your model. To save the view, type a name that is 31 characters or less in the text box and select Save. The view appears on the Saved Views list. When you select the Saved Views button on the toolbar, an alphabetical list of saved views appears. Select a view from the list to reorient your model in the result window. Before You Use the Results Command You should know the following information when you use Analysis>Results: • You do not need to save your current model when you activate results. 929 Structural and Thermal Simulation - Help Topic Collection • • You do not need the original model to access results, only the study directory containing the results from a run. For Results, Mechanica opens a copy of the model it makes when you start a run. Save your result windows before exiting Mechanica if you want to use them again. Mechanica does not keep result windows between results sessions. Use the File>Save command in the Results user interface to save result windows and either the File>Open command or the Insert>Results Window from File command to re-use saved result windows. Mechanica saves the result window definitions in an .rwd file. If you define a result window for a design study, save it, and then rerun the same design study, the original result window definition may no longer be valid. You can change result window definitions for a particular design study whether or not you change anything about the design study just by modifying the values and settings you use when you define the result window. • You can use results from previous versions of Mechanica. Mechanica automatically converts old results for use with the current release. Comparing Results For many models, one of the most valuable understandings you can have is how the quantities you are interested in compare with each other. While you can perform this comparison by studying the legends and scales for the various result windows or by looking at the measures in your analysis Summary file, Mechanica provides tools to make comparing results easier. The Results user interface provides functionality that lets you tie the scale of one result window to that of another. To tie scales for two result windows, use Utilities>Tie and its subcommands. The method for tying graphs together is slightly different from the method for tying fringe, contour, and vector plots. Shading Your Model For fringe, contour, and vector result windows, use the View>Shade toggle to turn shading on and off for your model. The default for the toggle is the On state. In most cases, the shaded view improves the overall appearance of the result window. However, for viewing flat-surface models at certain angles, you may need to turn shading off to get an accurate idea of what your plot looks like. This is because shading is based on reflected light, and a flat surface viewed straight on reflects minimal color. Thus, you do not see correct demarcation between the various legend values. When you turn shading off, the model shows demarcations correctly. 930 Structural and Thermal Simulation Probing Graphs After you initially evaluate your results and adjust your result windows for efficient viewing, you can examine your results more closely by probing specific aspects of the result window. You can study a segment of your graph to get a more exact impression of the values in that area. These detailed probes can help you get a more exact idea of how your model behaves at certain key points in the graph. For example, if you are working with the results of a dynamic time, frequency, or random response analysis, you may want to segment the graph around some of the resonant peaks so that you can study the peaks in more detail, as shown below. The result window on the left is a full graph of displacement in the Z direction for a dynamic frequency analysis. The result window on the right is a segmented version of the first graph, showing the details of the point values from 1.0 on the frequency scale, and capturing the displacement peak. Note that this example also segments the graph at 0.01 along the displacement measure scale to provide easier interpretation of the point values on the graph. 931 Structural and Thermal Simulation - Help Topic Collection Probing Fringe, Contour, and Vector Plots After you initially evaluate your results and adjust your result windows for efficient viewing, you can examine your results more closely by probing specific aspects of the result window. You can: • • • determine where the quantity minimum and maximum lie check values at specific locations of interest study how the quantity behaves in the interior of your model These detailed probes help you decide how well your model behaves as a whole, whether the model needs to be improved, and, if so, where the improvements should take place. Using Maximum and Minimum Legend Values to Get More Details The maximum and minimum values you enter in the Format Legend dialog box determine how the shading will be graded for your model. You can use these values to get a better idea of how a particular range of values is distributed over your model. For example, if you enter a new maximum that lies halfway between the calculated minimum and maximum for the quantity, Mechanica shades all areas that fall above that value red, assuming you are using the Structural color spectrum. The software linearly re-scales the values that lie between the new minimum and maximum. As a result, you will be able to see a more detailed fringe of the lower ranges of your model. 932 Structural and Thermal Simulation To see the difference between a default view and various alternate settings for the legend minimum and maximum, study this illustration: Note that with the maximum set low, you see much more detail on the lower half of the original range than you do in the original model. On the other hand, you can get more definitive information on the upper half of the original range, with the minimum set high. For example, were you to zoom in on the left hole for the version that shows the minimum set high, you would see a more exact representation of the stress distribution around the high stress area at the bottom of the hole. Tip: You can also control the level of detail in your plots by specifying either fewer or more legend levels. Orientation Dialog Box When you select View>Spin/Pan/Zoom, the Orientation dialog box appears. Use this dialog box to control the view angle, position, and size of your model within the result window. Spin/Pan/Zoom can be used for single or multiple windows. The Orientation dialog box includes: • Fixed View buttons — Use to quickly orient your model to any of several standard views, including isometric, trimetric, front, back, left, right, top, and bottom. 933 Structural and Thermal Simulation - Help Topic Collection • • • • • Pan controls — Use to move your model horizontally and vertically within the window. To pan your model, enter values in the Horizontal and Vertical text boxes. Negative values move your model to the left and down. Positive values move your model to the right and up. If you want to see the effects of panning live, use the Horizontal and Vertical slider controls instead of the text boxes. Zoom controls — Use to increase and reduce the size of your model within the window. To increase model size, enter positive values in the Zoom text box. To reduce the size, enter negative values. If you want to see the effects of zooming live, use the Zoom slider control instead. Refit button — Use to fit your model in the window. This button counteracts the Zoom controls. Center button — Use to center your model in the window. This button counteracts the Pan controls. Spin controls — Use to spin your model about the model spin center or the screen center. If you use the model center as your spin reference, the model spins about the X, Y, and Z axes. If you use the screen center as your spin reference, the model spins about the horizontal, vertical, and center axes of the screen. To spin your model, enter positive or negative values in the three text boxes. If you want to see the effects of zooming live, toggle the Dynamic Update box on and then use the Spin slider controls. Controlling Result Window Appearance You can control various characteristics of result window and model appearance, from the view angle to the model size to the color of the window. These characteristics fall into two categories: • Model view — Model view is the view angle, size, and position of your model as it appears in the result window. You can find controls for manipulating the model view on the View menu. All model view controls operate over single or multiple windows. Model view controls on the View menu include: o Repaint — Use Repaint to restore a clean appearance to all displayed result windows. This command removes any unnecessary clutter or spurious highlighting. For quick access, the toolbar includes a Repaint button, or you can press CTRL-R. Default — Use Default to return your model to its default position. For quick access, the toolbar includes a Default button, or you can press CTRL-D. Refit — Use Refit to fit the model to the size of the selected result windows. For quick access, the toolbar includes a Refit button. Saved Views — Use Saved Views to change the orientation of your model to a saved view or to save the current view. The Saved Views list includes views you saved in Pro/ENGINEER or Mechanica results. For quick access, the toolbar includes a Saved Views button. o o o 934 Structural and Thermal Simulation o Spin/Pan/Zoom — Use Spin/Pan/Zoom to open the Orientation dialog box, which lets you set the model view angle and size. For quick access, the toolbar includes Zoom In and Zoom Out buttons on the toolbar to help size your model. You can also press the CTRL key while holding down the middle mouse button to move the model around within the window. Note: For information on using Zoom and Refit when displaying a graph, see Segmenting a Graph. • Window format — Window format is the format of a result window—whether it includes a caption, whether it includes a legend, the background color, and so forth. You control window format using the Format>Result Window command and the View menu. Window format controls include: o o Format>Result Window — Use the Format Result Window dialog box to select and deselect various window characteristics. View menu — Use the View menu to overlay the undeformed model over an animation or to shade your model. How Mechanica Handles Your Working Model A working model is the model displayed in the Mechanica work area before you click the Analysis>Results command. A results model is the model in the design study you select for results viewing. Mechanica maintains two separate workspaces—the main Mechanica work area and the Results user interface. These two workspaces are independent of each other in system memory. If you activate the Results user interface while a model is displayed in the Mechanica work area, the model remains untouched. Both the working model and results model exist in system memory during your results session. When you close the Results user interface, the working model will be in the same state you left it. To Modify a Cutting Surface Use this procedure to modify an intersecting cut through your model. 1. Select Edit>Cutting/Capping Surfs. Depending on how many cutting surfaces you created for the result window, Mechanica performs one of these actions: o If you created only one cutting surface, the Results Surface Definition dialog box appears. o If you created multiple cutting surfaces, Mechanica instructs you to select a cutting surface. Once you select a surface, the Results Surface Definition dialog box appears. 935 Structural and Thermal Simulation - Help Topic Collection 2. To redefine the surface definition method, select a method from the Define By option menu. 3. If you changed your surface definition method to Three Points, use the selector arrow to select three points. 4. If you changed your surface definition method to UCS, use the selector arrow to select the desired coordinate system. 5. If you want to redefine the reference plane orientation, select XY, YZ, or ZX, as appropriate. 6. If you want to change the cutting surface depth, use one of the following methods: o Manually change the depth by entering a new value in the Depth entry box. o Dynamically change the depth by clicking Dynamic and dragging the mouse to increase or decrease the depth. Click the middle mouse button when you are finished repositioning the cutting surface. Mechanica updates the Depth value on the Results Surface Definition dialog box to reflect your change. 7. Click OK to close the dialog box. To Create a Cutting Surface Use this procedure to create an intersecting cut through your model. 1. Select Insert>Cutting/Capping Surfs. The Results Surface Definition dialog box appears. 2. Select Cutting Surface from the Type option menu. 3. Select the method for defining the surface from the Define By option menu. 4. If you selected Three Points as your surface definition method, use the selector arrow to select three points. 5. If you selected UCS as your surface definition method, use the selector arrow to select the desired coordinate system. 6. For all surface definition methods except Isosurfaces, select XY, YZ, or ZX as the reference plane. 7. Enter the depth of the cut along the axis normal to the plane. If you want Mechanica to calculate the value you enter as a percentage rather than an absolute value, select the % check box. 8. Click OK to close the dialog box. To Create a Capping Surface Use this procedure to make a solid cut through your model. 1. Select Insert>Cutting/Capping Surfs. The Results Surface Definition dialog box appears. 936 Structural and Thermal Simulation 2. Select Capping Surface from the Type option menu. 3. Select the method for defining the surface from the Define By option menu. 4. If you selected Three Points as your surface definition method, use the selector arrow to select three points. 5. If you selected UCS as your surface definition method, use the selector arrow to select the desired coordinate system. 6. For all surface definition methods except Isosurfaces, select XY, YZ, or ZX as the reference plane. 7. Select Above or Below to indicate which side of the capping surface Mechanica should trim. 8. Enter the depth of the cut along the axis normal to the plane. If you want Mechanica to calculate the value you enter as a percentage rather than an absolute value, select the % check box. 9. Click OK to close the dialog box. To Set Titles You can toggle the title of a result window on or off. The title appears centered at the bottom of the window. 1. Select Format>Result Window. Mechanica displays the Format Result Window dialog box. 2. Select Titles to turn the title on or off. Mechanica toggles the title. Any change you make to the title stays with the result window until you edit the window definition or close your result window. To Untie Multiple Result Windows Use this procedure if you want to untie a group of result windows so that they no longer share a common range. This procedure assumes you are in the Utilities menu. 1. Select Untie. Mechanica restores the original range for the current window if the range was altered when you tied the window. Mechanica redraws the display if the range has changed. 2. To untie any other windows you tied to the current window, repeat step 1 for each window you want to untie. To Tie Multiple Result Windows Use this procedure if you want to tie a group of contour, fringe, graph, and/or vector windows together so that they all share a common range. This procedure assumes you are in the Results user interface. 1. Select the first result window. 2. Select Utilities>Tie. 3. When the Tie submenu appears, select from: o Legend 937 Structural and Thermal Simulation - Help Topic Collection o o o Graph Quantity Graph Location Graph Both The options available on the Tie submenu depend on the result window type. 4. Select the second result window. 5. Repeat steps 3 and 4 to tie the first result window to each other window you want to include in the group. By the time you reach the last window in the group, all windows should be tied to the first window. All windows in the group share a common range. For fringe, vector, and contour plots, changing the legend values of the first window changes the legend value of all the tied windows. To Set Labels You can toggle the labels displayed on a result window on or off. The labels are the lines of information shown in the upper left of each window. 1. Select Format>Result Window. Mechanica displays the Format Result Window dialog box. 2. Select Labels to turn on or off. Mechanica toggles the label that appears in the upper left corner of your result window. Any change you make to the labels stays with the result window until you edit the window definition or close your result window. To Query for Linearized Stress This procedure assumes you are in the Info menu. 1. Select Linearized Stress Query. 2. Select two locations on your model. The line connecting the locations defines the X axis. 3. For 3D models, enter a third location to define the positive Y axis. Mechanica displays a Cartesian UCS with the origin at the midpoint of the line between point 1 and point 2. The Linearized Stress Report dialog box appears, displaying the results. 938 Structural and Thermal Simulation To Generate a Report for Linearized Stress This procedure assumes you are in the Linearized Stress Report dialog box. 1. Select Generate Report. The Generate Query Report dialog box appears. 2. Enter a file name for the report. Mechanica writes the data in tabular form to the file you specified and adds the extension .qrt to the name. To Export a File in VRML 1. Select File>Export>Direct VRML. 2. If you have multiple result windows, select one result window. You can export only one fringe plot at a time. The Export VRML dialog box appears. 3. Enter a name for the target VRML file. The file is saved with a .wrl extension. 4. Select a location to store the VRML file. 5. Click Save to export the VRML file. To Tie Multiple Graph Result Windows, Procedure 1 This procedure assumes you clicked either the Graph Quantity or Graph Location commands for tying a group of windows. 1. Find the result window containing the graph with the maximum value and the graph with the minimum value on the axis you want to tie. 2. If the same graph has both the maximum and minimum values, tie that graph to each other window. 3. If two different graphs have the maximum and minimum values, tie those two graphs together. Then tie either graph to the remaining windows in your group. If you want to tie both axes, carry out the above procedure for both the Graph Quantity and Graph Location commands. To Modify a Capping Surface Use this procedure to modify a solid cut through your model. 1. Select Edit>Cutting/Capping Surfs. The Results Surface Definition dialog box appears. 939 Structural and Thermal Simulation - Help Topic Collection 2. To redefine the surface definition method, select a method from the Define By option menu. 3. If you changed your surface definition method to Three Points, use the selector arrow to select three points. 4. If you changed your surface definition method to UCS, use the selector arrow to select the desired coordinate system. 5. If you want to redefine the reference plane orientation, select XY, YZ, or ZX, as appropriate. 6. If you want to redefine which side of the capping surface Mechanica trims, select Above or Below, as appropriate. 7. If you want to change the cutting surface depth, use one of the following methods: o Manually change the depth by entering a new value in the Depth entry box. o Dynamically change the depth by clicking Dynamic and dragging the mouse to increase or decrease the depth. Click the middle mouse button when you are finished repositioning the cutting surface. Mechanica updates the Depth value on the Results Surface Definition dialog box to reflect your change. 8. Click OK to close the dialog box. To Segment a Graph This procedure assumes you have selected a graph results window. 1. Select the Segment Graph command. 2. Select the first graph segment point. 3. Select the second point. Mechanica redraws the graph. 4. If necessary, you can do one of the following for the next step: o Segment the graph further. o Use Full Graph to restore the original graph. To Export a File as an MPEG Use File>Export>MPEG to save your animation as an MPEG file. 1. Select a result window from the option menu. 2. Select Export>MPEG from the File menu. The MPEG Export dialog box appears. 3. Enter the path and name for the target MPEG file by typing it or using the Browse button. The software automatically adds a .mpg extension to the path. 940 Structural and Thermal Simulation 4. Select an output setting. If you choose Custom, you must also define the frames per second, height, and width, or accept the default settings. 5. Set the compression. 6. Set the duration as either the number of frames, or seconds. 7. Click Export. The file is saved. To Export a File in HTML In performing the following procedure, be aware that certain steps—creating a browser heading, adding a title block and introduction, and creating a conclusion— are optional. 1. Select File>Export>HTML Report. The HTML Report dialog box appears. 2. Enter the path for the target HTML file by typing in the name. The software automatically adds an .htm extension to the path. 3. Enter a browser title. 4. Enter a title for your report. 5. Configure the Title Block. 6. Enter text for the Introduction. 7. Configure the inclusion of modeling information and VRML for the results window(s). 8. Enter a Conclusion for your web report. 9. Click Export. Mechanica saves the file with a .htm extension. To Edit the Legend This procedure assumes you are in the Edit menu. 1. Select Legend Value. 2. Select a value from the legend. Mechanica displays a dialog box. 3. Enter a new value. If you enter a new minimum or maximum value, Mechanica may ask if you want to redistribute levels. 4. To keep the new minimum or maximum value, enter y. To Create a Graph Report 1. Click File>Export>Graph Report. 941 Structural and Thermal Simulation - Help Topic Collection The Export To Text dialog box appears. 2. Enter a path and file name. 3. Click OK. Mechanica creates a file with a .grt extension. To Create an Excel Graph Report 1. Click File>Export>Excel. The Export To Excel dialog box appears. 2. Enter a path and file name. 3. Click OK. Mechanica creates a file with a .xls extension. To Tie Multiple Graph Result Windows, Procedure 2 This procedure assumes you clicked the Graph Quantity, Graph Location, or Graph Both command for tying a group of windows. 1. Tie the first result window to each other window you want to include in the group. 2. Tie the second result window to each other window you want to include in the group except the first window. 3. Repeat this sequence for each window. By the time you reach the last window in the group, all windows should be tied to each other. If you use this method, you would use the appropriate Graph command six times to tie a group of four result windows. Strategy: Displaying Graphs with Logarithmic Scales The most common reason you switch from a linear to a logarithmic scale is to better visualize graph values for dynamics results. In this case, you need to use logarithmic scales to get an accurate picture of how your model responds to frequencydependent conditions. Here is an example of the same graph shown with linear and logarithmic scales. The graph is a plot from a dynamic frequency response analysis run on a cantilever beam. The graph plots the magnitude of the displacement versus frequency. 942 Structural and Thermal Simulation In the graph on the left, both the X and Y axes use linear scales. Here all the values are compacted along the X and Y axes, making it difficult to see any changes in the response. In the graph on the right, with logarithmic X and Y axes, you can see much more detail. Here it is easy to see that the displacement varies widely at low frequencies, decreasing smoothly once the frequency increases sufficiently. Logarithmic axes are especially helpful when you plot a very large range of values. If you decide to return a graph to its original state, use the Format Graph dialog box to re-enter the original settings. Customizing Graph Display Settings You can use the bmgr_pref_file config.pro option to customize various settings for your graphs. The settings you can define in this file include the axis and graph line weights, label fonts, tick mark types, grid styles, and so forth. With this option turned on, Pro/ENGINEER uses settings stored in a user-created graph preferences text file to determine how to render your graphs. Customizing your graph in this way can help you ensure the exact graph display characteristics you want each time you view a graph. You can also save yourself the time of manually reformatting each graph through the Graph Window Options dialog box. 943 Structural and Thermal Simulation - Help Topic Collection If you want to change the appearance of your customized graph, you are still free to do so through the Format>Graph command. You can create a graph preferences file manually or automatically: • Automatic method — Before selecting the Analysis>Results command, select Tools>Options and activate the bmgr_pref_file option, being sure to specify a file name for the graph preferences file. When you next format a graph result window, Mechanica adds a Set Default button to the Graph Window Options dialog box. Use the Graph Window Options dialog box to make all desired changes to your graph appearance and click the Set Default button to save these settings. Mechanica then creates a text file with the name you specified and stores the settings from the dialog. The next time you create a graph result window, Mechanica uses the text file to determine the appearance of the graph. Manual method — Create a text file that contains the settings you want. Once you create the file, you add the bmgr_pref_file option to your config.pro file, making sure to set the option to the file name of your graph settings file. To help you create a valid graph settings file, here is a sample file, showing the items you can set and what some of the possible values might be. X_Axis_Color 5.019608e-01f,5.019608e-01f,1.000000e+00f X_Axis_DisplayLabel 1 X_Axis_GridColor 5.019608e-01f,5.019608e-01f,0.000000e+00f X_Axis_GridEnabled 1 X_Axis_GridStyle 2 X_Axis_LabelColor 1.000000e+00f,1.000000e+00f,1.000000e+00f X_Axis_LabelEnabled 1 X_Axis_LabelFont graphtool_font X_Axis_LabelFontHeight 1.500000e-01f X_Axis_Thickness 4 X_Axis_TickColor 1.000000e+00f,1.000000e+00f,1.000000e+00f X_Axis_TickFont graphtool_font X_Axis_TickFontHeight 1.000000e-01f X_Axis_TickHorizontal 1 Y_Axis_Color 1.000000e+00f,0.000000e+00f,0.000000e+00f Y_Axis_DisplayLabel 1 Y_Axis_GridColor 5.019608e-01f,5.019608e-01f,0.000000e+00f Y_Axis_GridEnabled 1 Y_Axis_GridStyle 2 Y_Axis_LabelColor 1.000000e+00f,1.000000e+00f,1.000000e+00f Y_Axis_LabelEnabled 1 Y_Axis_LabelFont graphtool_font Y_Axis_LabelFontHeight 1.500000e-01f Y_Axis_Thickness 2 Y_Axis_TickColor 1.000000e+00f,1.000000e+00f,1.000000e+00f Y_Axis_TickFont graphtool_font Y_Axis_TickFontHeight 1.000000e-01f Y_Axis_TickHorizontal 1 • Managing Graphs When you select the Format>Graph command, Mechanica displays the Graph Window Options dialog box. Use this dialog box to define the visual characteristics of the graph display window. For example, you can change the background color of 944 Structural and Thermal Simulation the window or the color of the x and y axes to improve the overall appearance of your graph. You can also specify new axis labels or adjust the scale for the graph to have a better view. The dialog box contains the following tabs: • • • • Y Axis — Use to modify the appearance of the graph's y axis, its label and grid lines, and to change the scale for the graph. X Axis — Use to modify the appearance of the graph's x axis, its label and grid lines, and to change the scale for the graph. Data Series — Use to control the appearance of data series for the graph you select and to toggle the legend. Graph Display — Use to control the display of the graph's title and to change the background color of the window. You can customize the basic settings for graph displays and, consequently, for this dialog box by using the bmgr_pref_file config.pro option to set graph defaults. Querying for Linearized Stress Use Info>Linearized Stress Query to display linearized stress values. After you select Linearized Stress Query or Query, Mechanica prompts you to select two locations. For each location, select a point, an edge, or the intersection of two plotting grid lines. Mechanica labels them points 1 and 2. The line connecting the first two locations defines the X axis. For 3D models, you enter a third location to define the positive Y axis. Mechanica displays a Cartesian UCS with the origin at the midpoint of the line between point 1 and point 2. The Linearized Stress Report dialog box then appears, displaying the results. Graph Report Use this command to write the graph data to a text file. After you select File>Export>Graph Report, you enter a path and file name in the Export To Text dialog box. When you click Save, Mechanica creates a text file with a .grt extension. This file contains header information consisting of the graph quantity, an indication of selected geometry, axis designations, and so forth. Immediately after the header information, Mechanica lists the graph values for each axis in vertical format. 945 Structural and Thermal Simulation - Help Topic Collection Dynamic Query Show the value of the result window's quantity at locations you select. You can query one location or multiple locations: • One location — Drag the cursor over the location. While you drag, a dialog box shows the value at each location the cursor crosses. To cancel, click the Done button. Tip: Some locations may be difficult to select at certain views. If you have trouble selecting a query location, try changing the view and selecting the location again. • Multiple locations — Click the left mouse button at a location. Mechanica marks the location with a diamond-shaped icon and displays the value above the icon. To cancel, click the Done button. Relabel Contour Use this command to change the number of lettered labels that appear on the contour plot. The command is Utilities>Relabel Contour. You specify label density on the Result Window Definition dialog box. Labels are only visible for the contour plot if you select the Labels toggle on the Format Result Window dialog box When you define the result window, you set the initial state of labels. See Contour Results Display for information. When you select the Relabel Contour or Relabel command, Mechanica prompts you to enter a new value for label density. The density is an integer from 1 to 10. Use lower numbers to get more labels. Results Surface Definition Dialog Box When you select Insert>Cutting/Capping Surfs, the Results Surface Definition dialog box appears. Use this dialog box to define cutting and capping surfaces in your model. The dialog box includes these items: • Type — Select Cutting Surface or Capping Surface, as applicable. You can create only one capping surface for your result window. If you create a capping surface in a result window, the Insert>Cutting/Capping Surfs command becomes inactive until you delete the capping surface. You can create multiple cutting surfaces for your result window. Once you create one cutting surface, Mechanica deactivates the Type option menu, and 946 Structural and Thermal Simulation from that point forward you can add cutting surfaces only. If you delete all your cutting surfaces, you will again be able to create capping surfaces. • • • Define By — Select the method for defining the surface. Plane — Select the plane the surface lies in. This area does not appear if you define your cutting or capping surface as an isosurface. Location — For capping surfaces only, select one of these option buttons: o Above — Cap the model above the capping surface. In this case, Mechanica fringes the model below the capping surface and hides the fringe display above the capping surface. o Below — Cap the model below the capping surface. In this case, Mechanica fringes the model above the capping surface and hides the fringe display below the capping surface. Depth — Enter the depth of the cutting or capping surface along the axis normal to the plane. You can enter depth as an absolute value or select the % check box to treat the value as a percentage. Dynamic — Use your mouse to dynamically change a surface's depth and update its visualization. Apply — Preview the cutting/capping surface without closing the dialog box. Once you select this button, the Dynamic button becomes active. • • • Titles Use this command to turn on and off the title of a result window, or to edit the text of the title. The title appears centered at the bottom of the window. You can include a title and a subtitle in this block. When you select Titles, you also select a result window if you are displaying more than one. Mechanica then toggles the title display in that result window. To edit the title, use the Edit>Result Window command. Any change you make to the title with this command stays with the result window until you either edit the window definition or close the Results user interface. If you have the title block displayed when you print your work area, it appears in the printed copy. Printing Result Windows Use the File>Print command or the File>Export>Image command to print result windows or export an image from a part or assembly. The Export Image dialog box is identical to the Print dialog box. When you select Print or Image, the Print dialog box appears. The Print dialog box contains the following items: • • • Output Format — Select the format you want to use to print. Paper — Select the size, height, and width of your page. Quality 947 Structural and Thermal Simulation - Help Topic Collection • • • Resolution — Select 100, 200, 300, 400, 500, or 600 dots per inch from the option menu. o Image Depth — Select 24 bit or 8 bit from the option menu. Plot Format o Spin image — Select the orientation of the plot, landscape or portrait. o Zoom factor — Select a scaling factor for the print in HPGL2 or Postscript formats. o Offset — Enter values to move the plot away from the x or y axes of the paper. Copies — Select the number of copies from the option menu. Output Options o To File — Select this check box to print to a file. Type the name of the destination file or use the Browse button to select the desired file. o To Printer — Select this check box to send the file to a printer. Enter the command that you want Mechanica to use to print directly to the specified printer. o Delete Temporary Plot Files — Select Never, Immediately, or Dialog. o Labels Use this check box to turn labels on and off in a result window. The labels are the lines of textual information shown in the upper left corner of each window. Selecting the Label check box toggles the display of labels in the result window or multiple windows you select. Any change you make to the labels with this command stays with the result window, stored in the .rwd file, until you edit the window definition or exit the Results user interface. Each result window contains one or more of these labels, depending on how you define the window: • • • • • • • • the selected quantity and its units, and any scale factor you specified for a graph the maximum value in a contour, fringe, or vector plot the minimum value in a contour, fringe, or vector plot the maximum displacement value for a deformed model unless the quantity is stress or strain the scale of deformation for structural analyses the mode number and, if available, frequency, for modal analyses the buckling load factor for buckling analyses the load set, if available, for static, dynamic, and thermal analyses Contour Labels Use this command to turn on or off lettered labels on the contour plot. Use the Format>Result Window command. Select or clear the Contour Labels box on the 948 Structural and Thermal Simulation Format Result Window dialog box. The Contour Labels box is active only if you selected Label Contours when you defined the result window. Select Labels to toggle the labels on or off. When Labels is active, Mechanica displays a series of labels along each contour curve. The labels are capital letters. Labels are especially useful if you are printing black and white hard copy. Otherwise, the contour colors generally provide enough information. Overlay Use to superimpose the undeformed model over the animation. Select this command to turn the overlay display on or off. When you first access the View menu, Overlay is active unless you deselected the Overlay option when you defined the result window. Excel Use this command to write the graph data to a Microsoft Excel spreadsheet. This command is only available if you select a single graph result window. After you select File>Export>Excel, Mechanica displays the Export To Excel dialog box. Enter a path and file name on the dialog box. When you click OK, Mechanica creates a file with an .xls extension. The file contains a pictorial rendition of the graph as well as a numeric table of graph results at given intervals. Following is a sample spreadsheet. 949 Structural and Thermal Simulation - Help Topic Collection HTML Report Use File>Export>HTML Report to publish results on the web. You can export multiple graphic results at a time using this command. If the results are animated, Mechanica adds a movie icon to the bottom of the report. Click this icon to view the animation in MPEG form. After you select HTML Report, the Export HTML dialog box appears. This dialog box enables you to specify a title and enter introductory remarks, comments, and a conclusion for your web report. In the Item area, select the window you wish to annotate, then enter your comments in the Comment section in the Content area. Height and width measurements of the result graphics appear for all size options except Current View. In this case, results are the same size as they appear in the Mechanica result window. Tie Multiple Graph Result Windows If you want to tie a group of graph windows together so that they all share a common interval, you must tie each window in the group to each other window in the group. There can be no existing ties between any of the windows. You can use one of the following for tying a group of windows: • • Use the Graph Quantity or Graph Location command. Use the Graph Quantity, Graph Location, or Graph Both command. 950 Structural and Thermal Simulation Linearized Stress Report Use this dialog box to view linearized stress results for a result window: At the top of the dialog box, Mechanica displays the WCS coordinates of the locations you selected. The middle area of the dialog box displays the values of your selected stress quantity at the three locations, or two in the case of 2D models. It also lists the maximum of the values. These results are in terms of the local coordinate system. For information on how Mechanica calculates these values, see Linearized Stress Value Calculation. The dialog box also contains these items: • • Component — Select the specific type of linearized stress quantity results you want Mechanica to display. Generate Report — Save the results to a file. 951 Structural and Thermal Simulation - Help Topic Collection Generate Report for Linearized Stress Results Use the Generate Report button to save the results in a text file. When you click the button, Mechanica displays a dialog box in which you enter a file name for the report. Mechanica writes the data in tabular form to the file you specified, and adds the extension .qrt to the name. Defining Reference Planes for Cutting or Capping Surfaces Use the Plane area on the Results Surface Definition dialog box to select the plane that you want Mechanica to use as a reference when creating the cutting or capping surface. You can select from among: • XY — Create a cutting or capping surface parallel to the XY plane of the coordinate system, screen view, or three-point grid you selected. In this case, Mechanica calculates the depth of the cut or cap in the direction of the Z axis starting with the model geometry nearest the coordinate system origin. XZ — Create a cutting or capping surface parallel to the XZ plane of the coordinate system, screen view, or three-point grid you selected. In this case, Mechanica calculates the depth of the cut or cap in the direction of the Y axis starting with the model geometry nearest the coordinate system origin. YZ — Create a cutting or capping surface parallel to the YZ plane of the coordinate system, screen view, or three-point grid you selected. In this case, Mechanica calculates the depth of the cut or cap in the direction of the X axis starting with the model geometry nearest the coordinate system origin. • • Dynamic Cutting and Capping Surface Displays Use the Dynamic button on the Results Surface Definition dialog box to dynamically change a cutting or capping surface's depth. This button is only active if you are modifying an existing cutting or capping surface. When you click the Dynamic button, Mechanica closes the Results Surface Definition dialog box. You can then use your mouse to dynamically move the cutting or capping surface to different areas of your model. To do so, depress the left mouse button and move the mouse as follows: • • To raise the cutting or capping surface — move the mouse upward in the positive Y screen direction. To lower the cutting or capping surface — move the mouse downward in the negative Y screen direction. Mechanica repositions the cutting or capping surface according to your mouse movements, but retains the original angle of the surface. When you finish positioning 952 Structural and Thermal Simulation the cutting or capping surface, click the middle mouse button to return to the Results Surface Definition dialog box. The dialog box's Depth field now reflects the change you made in the cutting or capping surface location. Defining Cutting or Capping Surface Depth Use the Depth area of the Results Surface Definition dialog box to define the depth of the cutting or capping surface relative to the geometry or values in the model. Mechanica determines depth differently depending on the option you select in the Define By option menu. • WCS, Three Point, UCS, and Screen — For absolute values, Mechanica calculates the depth by measuring the value you enter along the axis normal to the reference plane, using the model geometry nearest the reference entity as a starting point. For percentage values, Mechanica measures the percentage along the axis normal to the reference plane, with the exact position determined by the distance between the widest portion of your model along that axis normal. • Isosurfaces — For absolute values, enter a value in the legend range for the result window. Mechanica displays the isosurface nearest that value. For percentage values, Mechanica uses the top and bottom values in the legend range to convert the percent you enter to a specific legend value. The software then displays the isosurface nearest the calculated legend value. Defining Cutting or Capping Surface References Use the Define By field on the Results Surface Definition dialog box to indicate the references for cutting or capping surfaces. You can select from: • • WCS — Create the cutting or capping surface relative to the WCS. Three Points — Create the cutting or capping surface relative to an XY plane established when you select three points. The Three Points option provides you with a high degree of flexibility in how you define the cutting or capping angle relative to your model's geometry. When you select this option, Mechanica adds a selection area to the dialog box. Use the selector arrow in this area to select the points. Mechanica treats the points as follows: o First Point — Establishes the point of origin for the coordinate system o Second Point — Establishes the direction of the X axis o Third Point — Establishes the direction of the Y axis UCS — Create the cutting or capping surface relative to a coordinate system you defined for the model. The UCS you select must be Cartesian. • 953 Structural and Thermal Simulation - Help Topic Collection When you select this option, Mechanica adds a selection area to the dialog box. Use the selector arrow in this area to select the UCS. • • Screen — Create the cutting or capping surface relative to the angle at which you are currently viewing the model in the result window. Isosurface — Create the cutting or capping surface based on the nearest isosurface. This option is only available for fringe plots. The Isosurface option behaves differently depending on whether you are working with cutting surfaces or capping surfaces: o o Cutting Surface — Mechanica displays the single isosurface whose range is nearest the value you specify in the Depth field. Capping Surface — Mechanica displays the single isosurface whose range is nearest the value you specify in the Depth field. It also fringes the model above or below the isosurface range, depending on the location you select. MPEG Export Dialog Box When you select File>Export>MPEG, the MPEG Export dialog box appears. You use this dialog box to control the quality of the MPEG file. The dialog box includes: • • File Selection Button — Select a path and name for the MPEG file. Output Settings — Controls the size and quality of the image using specific standards. You can select from four pre-set options, or use the custom selection. o NTSC Web o NTSC CDROM o PAL Web o PAL CDROM o Custom — Selecting Custom allows you to edit the FPS, Height, and Width options. Image Quality — Use this area to control the quality of the animation. o FPS — Specifies the number of pictures per second for the animation. Generally, the more frames per second, the smoother the animation will appear. The maximum value is 30. o Compression — Controls the file compression. The default is 0.75. The higher the number, the higher the quality of the picture. Image Size — Use this area to define the size of the generated MPEG in pixels. o Height — Control the height of the animation. o Width — Control the width of the animation. Duration — Use this area to control the length of the animation. You can define the duration in two ways: o Number of Frames — Define the duration of the animation by a specific number of frames. o Seconds — Define the duration of the animation by a specific amount of time. • • • 954 Structural and Thermal Simulation Log Scale Use the Log Scale check box on the X Axis and Y Axis tabs of the Graph Window Options dialog box to change the values on the graph's X or Y axis to a logarithmic scale. After you select Log Scale for an axis, Mechanica converts the values on the appropriate axis to log base 10. If you then deselect the check box, the values return to a linear scale. Following are the limitations of these commands: • • • You cannot convert an axis to a log scale if the axis contains any non-positive values. You cannot change the scale of a graph that is tied to another graph. You cannot tie two graphs that are not using the same scale on both axes. For example, if graph 1 uses log scale on the x axis and linear scale on the y axis, and graph 2 uses linear scale on both axes, you cannot tie them in any way. If you change the x axis on graph 2 to log scale, you can then tie the graphs. Linearized Stress Value Calculation Mechanica calculates the linearized stress values with respect to a local coordinate system with the X axis aligned with the line from location 1 to location 2 and the origin at the midpoint of the line from location 1 to location 2. Mechanica first calculates the total local coordinate stress components at each point. It then calculates membrane, bending stress, peak stress, and total stress as follows: • Membrane and bending stress values are obtained from numerical integration along the line between location 1 and location 2 as follows: where: is any local stress component L is the distance from location 1 to location 2 955 Structural and Thermal Simulation - Help Topic Collection • Total stress is the value calculated by Mechanica, and the peak stress is defined by: Peak = Total – (Membrane + Bending) Peak, Total, and Bending Stresses vary along the line from location 1 to location 2; however, membrane stress remains constant. Mechanica then processes the component values of these stresses at each point to obtain principal and von Mises stresses, using the standard formula for principal and von Mises stress. Note: The formula for peak and total stress applies for each component of stress, but not for the principal or von Mises stress. For axisymmetric models, similar formulas are used, with correction terms to account for the offset of the neutral bending axis from the midpoint. Component for Linearized Stress Results Use the Component option menu to select the specific type of linearized stress quantity results you want Mechanica to display on the Linearized Stress Report dialog box. You can then view linearized stress values for different locations in your model, using the same component option. These stress quantities apply to 2D shells, 2D solids, 2D plates, and 3D solids. You can select from these options: • • • • • • • • • • • Max Principal — the most positive principal stress Min Principal — the least positive principal stress Max Prin – Min Prin — the difference between the most positive and least positive principal stress Von Mises — a combination of all stress components Local XX — normal stress along the local X axis Local YY — normal stress along the local Y axis Local ZZ — normal stress along the local Z axis Local XY — shear stress in the local XY plane Local XZ — shear stress in the local XZ plane Local YZ — shear stress in the local YZ plane ZZ — normal stress along the local Z axis for 2D shells and 2D solids. This stress component is always 0 for 2D plates. Graphtool Window You use the Graphtool window to view and manage different types of graphs. In Mechanica, the Graphtool can draw functions or graph various analysis results. After you display your graph, you can interact with it in several ways. To find out the x and y values for any graph point, click on this point and a message box appears showing the values. 956 Structural and Thermal Simulation To work with the graph and manage its appearance, use toolbar buttons or the following menu commands: • File o o • • o o View o Toggle Grid — Display grid lines for your graph or turn them off. o Repaint — Refresh the view of your graph, removing all temporarily displayed information. o Refit — Restore a graph to its original state. Use this command after you zoom in on a particular graph segment to return to an unsegmented state. Mechanica automatically redraws the complete graph in the current window. o Zoom In — Zoom in on the graph to get a close-up view. This command is especially useful when your graph contains too many points, 100 or more. Zooming in on certain points helps you to display a specific segment of interest. Format • Graph — Open the Graph Window Options dialog box to manage your graph and its display window. Export Excel — This option is available on Windows platforms only. Use it to save the graph data as a Microsoft Excel spreadsheet. When you click this command, Mechanica displays the Export To Excel dialog box. Enter a path and a file name on the dialog box. When you click OK, Mechanica creates a file with a .xls extension. The file contains a pictorial rendition of the graph as well as a numeric table of graph results at given intervals. Export Text — Save the graph data as a text file. When you click this command, Mechanica displays the Export To Text dialog box. Enter a path and a file name on the dialog box. When you click OK, Mechanica creates a file with a .grt extension. Print — Send your graph to a printer. Exit — Close the Graphtool window. X Axis and Y Axis Tabs Use the X Axis and the Y Axis tabs on the Graph Window Options dialog box to customize the appearance of the x and y axes, specify new axis labels, and adjust the scale for the graph. The tabs display the following fields: • Graph — This field appears on the Y Axis tab only and displays a list of subgraphs when they are available. Mechanica uses subgraphs to plot multiple sets of data that share a common x axis but have different y axes. From the list, select a subgraph for which you want to customize the y axis. Axis Label — Use the input field to edit an axis label. The label is a textual line that appears next to each axis. You can change the style, color, and size of the label's font by clicking the Text Style button. Use the Display Axis Label check box to turn the axis label on or off. Range — Change the range of the axis. You can use this area to reset minimum and maximum values so that the window displays a specified segment of the graph. Tick Marks — Set the number of major and minor tick marks on the axis. • • • 957 Structural and Thermal Simulation - Help Topic Collection • • • • Tick Labels — Change the alignment of value labels for the major tick marks. If you want to change the style, color, and size of the font, click the Text Style button. Grid Lines — Select the style for the grid lines. If you want to change their color, click the color selection button. Axis — Modify the thickness of the axis. Click the color selection button if you want to change the axis color. Scaling — Use this area to adjust the scale for your graph: o Log Scale — Change the values on the axis to a logarithmic scale. Using a logarithmic scale can provide you with additional information that you may not be able to see on a normal scale. o Scale — This field appears on the Y Axis tab only. You can use it to change the scale of the y axis. Segmenting a Graph When your graph has too many points and looks crowded, you can segment it to display a specific section of interest. Segmenting a graph is especially useful for dynamic time, frequency, or random response analysis results, which may contain 100 or more points in Structure. You can use one of the following methods to segment your graph: • • Zoom In — Use the View>Zoom In command on the graph results window to get a close-up view of a specific graph segment you select. Change the Axis Range — Reset minimum and maximum values for the graph range to define a segment you want to display. The x minimum should display the x coordinate that is at the left edge of the graph segment, the x maximum at the right edge, the y maximum at the top edge, and the y minimum at the bottom edge. Mechanica then redraws the graph to show the specified segment. After you finish studying a particular graph segment, you can restore a graph to its original, unsegmented state. Use the View>Refit command. After you select the command, Mechanica automatically redraws the complete graph in the current window. Legend Value Use this command on the Edit menu to change one or more of the values on the legend along the right side of a fringe, fringe animation, contour, or vector result window. If no result window is currently selected, the Selection dialog box appears and you can select one or more result windows from the list to edit. The legend shows the colors used in the plot and the range connected to each color. Mechanica calculates the level of each fringe boundary by distributing the levels linearly from minimum to maximum. 958 Structural and Thermal Simulation After you select the command, select a value from the legend. Then enter a new value. For more information about entering new values, see Guidelines for Changing Legend Values. If you enter a new minimum or maximum value, Mechanica may ask if you want to redistribute levels. Mechanica regenerates the plot to take the new levels into account. Redistribute Levels If you enter a minimum value greater than the level above it, or a maximum value less than the level below it, Mechanica prompts: Do you want to redistribute levels linearly from first to last <y>? To keep the new minimum or maximum value, you must enter y. Mechanica cannot use the new value without redistributing levels. Direct VRML Use File>Export>Direct VRML to export files in VRML format. You can export one non-animating discrete colored fringe plot (excluding p-level plots) at a time using this command. After you select this command, the Export VRML dialog box appears. If there is re than one fringe plot available, you are prompted to select one. Tip: You should minimize the number of graphical entities required to visualize the results. This reduces download time and improves graphics performance. Mechanica can export fringes as VRML 1.0 or VRML 2.0 format files. You can use a config.pro option to control the VRML format Mechanica uses as well as whether the VRML report will include feature edges. Tie — Contour, Fringe, Graph, or Vectors Result Windows Use to set a common range for two or more contour, fringe, graph, or vector plots currently displayed. This feature makes it easier to visually compare different result windows. You can also alter characteristics of the parent window for fringe, vector, and contour plots and Mechanica will alter those characteristics for all of the tied windows. For example, changing the legend values of the parent window changes the legend values of all the tied windows. 959 Structural and Thermal Simulation - Help Topic Collection You can tie two windows only if they meet certain criteria. You can find the Tie command on the Utilities menu. The Tie command invokes a submenu containing the Legend command, which you use to tie fringe, contour, and vector plots. The submenu also contains three commands for tying graphs. Mechanica sets up a new range that works for both result windows. This may involve changing one or both plots. Mechanica redraws either plot for which the ranges have changed. MPEG Export MPEGs to produce animated reproductions of your results. This feature can be used to help create presentations. The software offers the option of saving the animation of a single window as an MPEG file for just this reason. You can access this command using the File>Export>MPEG command. This command opens the MPEG Export dialog box. This dialog box enables you to specify a title and to determine the size and quality of the animation export. You can choose from five available options. The options are: • • • • • NTSC Web NTSC CDROM PAL Web PAL CDROM Custom The height, width, and number of frames per second are controlled by the option selected. You can only edit these options if you choose Custom. Default Select the Default command to set the view of your model back to the default orientation. A model appears in its default view orientation when it is first created, but a retrieved model appears in the orientation in which it was last saved. You can resume the default view at any time. Graphic Size Select one of the following graphic sizes: • • • • Current View — Results are the same size as they appear in the Mechanica results window. ISO A7 — 74 x 105 mm ISO A6 — 105 x 148 mm ISO A5 — 148 x 210 mm 960 Structural and Thermal Simulation View Menu on Results Window Toolbar Use the View menu to change the view of your model with the following commands: • • • • Repaint — Repaint a view to remove all temporarily displayed information. Repainting redraws the screen but does not regenerate the model. Default — Set the view to the default orientation. Refit — Refit your model so it is fully visible on the screen. Spin/Pan/Zoom — Change the position or size of your model. Graph Display Tab Use the Graph Display tab on the Graph Window Options dialog box to specify the graph's Label and change the background color of the window. The following fields appear on the tab: • Label — Edit the graph's label, which appears in the upper left corner of the graph window. If you want to change the style, color, and size of the font, click the Text Style button. Use the Display Label check box to display the label or remove it from the window. Background Color — Modify the background color. Click the Edit button to customize the blended background color. If you deselect the Blended Background check box, click the color selection button to change the background color. Selection Color — Change the color you use to highlight points on your graph. • • Orientation Dialog Box Select the Spin/Pan/Zoom command to change the position of your model by using the Orientation dialog box. The dialog box contains the following items: • Fixed o o o Views — Changes the view to one of the following: Isometric — Changes the view to an isometric view. Trimetric — Changes the view to a trimetric view. Front, Back, Left, Right, Top, Bottom — Changes the view to the named position. Pan — Modifies the location of the model relative to the display window by moving the frame of reference horizontally or vertically. Zoom — Modifies the size of the model relative to the display window by moving in or out relative to the screen. Use the slider or counter to increase or decrease the size. Refit — Redisplays the model so it is fully visible on the screen. Center — Displays your model relative to the center. Spin — Orients the model by spinning it about a specified spin center. Dynamic update — Enables you to view changes to your model as you make adjustments to it. • • • • • • 961 Structural and Thermal Simulation - Help Topic Collection File Menu on Results Window Toolbar When reviewing a graph of a function load, use the File menu to perform the following tasks: • • Print — Print an output file containing a picture of an object. Export — Export components or objects in your model to other formats. The following commands appear on the Export menu: o Image — Export an image of a part or assembly. o Direct VRML — Export an object directly to VRML. o HTML Report — Export an HTML report. Exit Results — Closes the result window. • Export VRML Dialog Box This dialog box appears if you select File>Export>Direct VRML. The dialog box includes these items: • • • Look In— Shows the path to the current directory and the list of files in that directory is shown below. Name— Displays the name of the VRML file to be exported. Type — Lists all files that end in .wrl, the type for VRML files. Export HTML Setup Dialog Box This dialog box appears if you click Setup and enables you to control the format of the HTML page. The setup dialog box includes the following items: • • • • • Graphic Format — Use JPEG File Interchange Format for a fringe plot or if your results have many colors. The more colors your results have, the more useful the JPEG format is. Graphic Size — Select the current view, ISO A7, ISO A6, or ISO A5. Alignment — Select Landscape or Portrait, if available. Height — This text box displaying the height of the graphic cannot be edited. Width — This text box displaying the width of the graphic cannot be edited. Export HTML Dialog Box This dialog box appears if you select File>Export>HTML Report. The dialog box includes these items: • • • • 962 HTML Report Name — Specify the file name, including path, to which you want to save the .htm file. Browser Title (optional) — Enter the title that will appear on the title bar of the browser. HTML Report Title (optional) — Enter the title that will appear at the top of the report. Item — This menu lists the windows selected for inclusion in the report. In addition to the windows, a Title Block, Introduction, and Conclusion section Structural and Thermal Simulation • • are listed as well. Selecting on any one of these brings up the attributes for that window in the content layout to the right of the list. o Title Block (optional) — Controls the appearance of the table of contents, as well as other descriptors. o Introduction (optional) — Enter an introduction you want included in the report. o Results Windows — Include modeling information and VRML. Use the Select button to choose which modeling entities to include for each window. o Conclusion (optional) — Enter a conclusion you want included in the report. Preferences — Controls the options for the appearance of the HTML file. Export — Export the .htm file to the directory specified in the HTML Report Name text box. Guidelines for Changing Legend Values Follow these guidelines for changing the values on a fringe, contour, or vector legend: • For any level except the minimum and maximum levels, you cannot change the value to a number greater than the next level up or less than the next level down. If you want to set a new value that would violate this rule, start from the top or bottom level and change each level in turn to make room for the new value. • The minimum value must always be less than the maximum value. Alignment The alignment options are available only if you selected Current View for the graphic size. The two options are: • • Landscape — Select this option to orient the graphic along the horizontal axis. The graphic is wider than it is high. Portrait — Select this option to orient the graphic along the vertical axis. The graphic is higher than it is wide. Data Series Tab Use the Data Series tab on the Graph Window Options dialog box to change the appearance of data series. Mechanica can display multiple data series that share common x and y axes in a single graph window. 963 Structural and Thermal Simulation - Help Topic Collection Use the following fields to work with the data series: • • Graph — Select a graph or subgraph whose data series you want to customize. Data Series — Use the input field to edit the label for the selected data series. To change the color of the graph's points and lines, click the color selection buttons. You can also modify the points' style and interpolation and the lines' thickness. Legend — Use this area to toggle the legend. If you want to change the style, color, and size of the font, click the Text Style button. • Untie — Contour, Fringe, Graph, or Vectors Result Windows Use this command to remove any ties you previously established for the current window. This command is available for these result window types: • • graph — The command undoes ties you created with the Tie>Graph Both, Tie>Graph Quantity, or Tie>Graph Location commands. fringe, contour, and vector plots — The command undoes ties you created with the Tie>Legend command. When you select Untie, Mechanica restores the original range for the current window if the range was altered when you tied the window. Mechanica redraws the display if the ranges have changed. To untie any other windows you tied to the current window, access the Control menu for each window separately and then select Untie. Tie Graph Windows These three commands are not active for graphs you display through the Function Definition dialog box. They are active for result window graphs, but they do not invoke prompts or take actions when only one graph is on the screen. Use these commands to more closely compare two different result window graphs: • • • Graph Quantity — Ties the quantity data on the Y axes of two graphs. Graph Location — Ties the location data on the X axes of two graphs. Graph Both — Ties the data on both axes of two graphs. After you select one of the Tie commands, select another graph result window. Mechanica sets up a new interval for the data on each axis that works for both result windows. This may involve changing one or both graphs. Mechanica redraws either graph for which the interval has changed. For more information on these commands, see Guidelines for Tying Graphs. 964 Structural and Thermal Simulation For a description of how to tie a group of graph windows together so that they all share a common range, see Tie Multiple Graph Result Windows. General Guidelines for Tying Result Windows Follow these guidelines when tying two result windows: • The result windows you plan to tie must be of the same type. You can tie the legends for fringe, vector, and contour plots together. You can also tie the scales of graph plots to each other. However, you cannot tie a graph to a fringe, contour, or vector plot. You cannot tie values for unfringed animations or model result windows because there are no values to tie. If you are working with fringe, contour, and vector plots, the quantities must be in the same general category. For example, you can tie a von Mises stress fringe plot to a maximum principal stress fringe plot, but not to a displacement fringe plot. If you are working with graphs, there are a number of special guidelines to bear in mind. • • • Guidelines for Tying Graphs Follow these guidelines when tying two graphs: • Both graphs must have the same location category for the X axis and the same quantity category for the Y axis, no matter which command you select. For example: o In Structure, you can tie a graph using Stress XX for the quantity to a second graph using Max Prin Stress, but not to a second graph using Disp Mag or Measure as the quantity. In Thermal, you can tie a graph using Temp Gradient X for the quantity to a second graph using Temp Gradient Mag, but not to a second graph using Flux Mag or Measure as the quantity. o • • If Iteration is the location, you cannot use the Tie Loc or Tie Both commands. If two graphs use different types of values on either axis—that is, if one is linear and one is logarithmic—you cannot tie them. See the description of the Log Scale check boxfor more information. Spin Spin orients the model by spinning it about a specified spin center. The Spin area contains the following items: • Spin center button — Click this button to spin your model using the spin center axis. o X — Use the slider or counter to spin the model about its x axis. 965 Structural and Thermal Simulation - Help Topic Collection • o Y — Use the slider or counter to spin the model about its y axis. o Z — Use the slider or counter to spin the model about its z axis. Screen center button — Click this button to spin your model using the screen center axis. o H — Use the slider or counter to spin the model about its horizontal axis. o V — Use the slider or counter to spin the model about its vertical axis. o C — Use the slider or counter to spin the model about its center. Refit Select the Refit command or click the Refit button on the toolbar to refit the model to the screen so that you can see the entire model. A refitted model uses 80 percent of the screen. You can also refit the model by clicking Refit on the Orientation dialog box Paper Size — Select one of the following page sizes from the option menu: F (40.0 x 28.0 in.) E (44.0 x 34.0 in.) D (34.0 x 22.0 in.) C (22.0 x 17.0 in.) B (17.0 x 11.0 in.) A (11.0 x 8.5 in.) A0 (1189 x 841 mm) A1 (841 x 594 mm) A2 (594 x 420 mm) A3 (420 x 297 mm) A4 (297 x 210 mm) Variable in Inch Variable in mm Height — Select the page height from the option menu. This option is available if you select the Variable in Inch or Variable in mm option for size. Width — Select the page width from the option menu. This option is available if you select the Variable in Inch or Variable in mm option for size. 966 Structural and Thermal Simulation Pan Pan modifies the location of the model relative to the display window by moving the frame of reference horizontally or vertically. The Pan area contains two items: • • H (horizontal setting) — Use the slider or counter to move the frame of reference to the left or right. V (vertical setting) — Use the slider or counter to move the frame of reference into or out of the screen. Output Format Use this option to specify the format that you want Mechanica to use when printing to a file. You can use the following output formats for Windows: • • Microsoft Print Manager — Prints a file to one of the available printers. Select a printer from the list. This format generates raster plots. Microsoft Print Manager (Vector) — Prints a file to one of the available printers. The files generated for vector plots are usually smaller than those for raster plots. Use this print format, for example, for pen plotters that cannot use raster fonts. Vector printouts are best used for printing text or wireframe images. You cannot use a vector format for a shaded image. You can use the following output formats for both Windows and UNIX: • • PostScript (Vector) — Prints a PostScript file for any printer that supports the PostScript page description language. HPGL2 (for exporting plots only) — Prints a file in the Hewlett-Packard Graphics Language. This format is used to print on a plotter or printer that supports HPGL2. Use it for graphs and contour plots. Some plotters might not fill solid areas such as shaded areas or fringe plots properly. When the plotter does fill solid areas, the fill might damage the paper or plotter pens. Using HPGL2 format to produce a fringe plot produces an extremely large plot file. It is strongly recommended that you use a contour plot instead. • • BMP (for exporting images only) — Prints a bit-mapped image. Encapsulated PostScript — Prints a file that you can include within another PostScript file. You cannot print this type of file without printing a PostScript file. You can use the following additional output formats for UNIX only: • • JPEG — Prints a file in the Joint Photographic Experts Group format. TIFF — Prints a file in the Tagged Image File Format. Only black and white output is available. Color .tif files cannot be produced, even though there is a color button selection. If possible, you should use .jpg. Both color and black and white .jpg files can be produced. 967 Structural and Thermal Simulation - Help Topic Collection If you do not have sufficient disk space when you output a file, such as a PostScript file, Mechanica may terminate. Common Facilities Working With Normals Surface Normals Use the Normal>Surface command to display the normal direction for each surface and to change the direction for one or more surfaces. This command appears for 3D models. Because Mechanica sets the normal direction separately for each surface when you create it, the direction of the normals for adjoining surfaces may end up in opposite or inconsistent directions. See Normal Direction for Surfaces and Shells for information on how Mechanica creates and uses normal directions. When you select Surface, magenta arrows appear displaying the normal direction for each surface in your model. Mechanica also displays a utility menu with the following commands: • • Fix Flip Mechanica checks whether you have fixed surface normals at certain points in the modeling process. Normal Direction for Surfaces and Shells The normal is always perpendicular to a surface or shell, except if a surface belongs to one and only one volume. These surfaces already have a natural consistent normal that points out of the volume. If your shell model is a midsurface compressed model, the normal direction is from the red side to the yellow side of the midsurface. For 3D models, if a solid face lies on a surface or shell, the surface or shell determines the normal direction of the face. If a solid face is not coincident with a surface or shell, the normal direction of the solid face always points away from the center of the solid. 968 Structural and Thermal Simulation The normal direction has these two purposes: • • Pressure loads always oppose the normal of a surface, midsurface shell, or any other element. However, for quilts, pressure load direction always coincides with the shell normal. The top of a surface or shell is always in the normal direction. The surface or shell displayed on the screen represents the midsurface of the element. You can view results for stress quantities at the top or bottom of a surface or shell. Specifying Y Direction for Beams When you create a beam, Mechanica sets the beam length as the X axis of the beam action coordinate system. You determine how the beam action coordinate system relates to the WCS by specifying the Y direction on the Beam Definition dialog box. See Beam Coordinate Systems for more information. If you reference two geometric entities such as two points, or a point and a surface, for the beam length, the positive X direction goes from the first entity selected to the second. If you reference an edge or curve, Mechanica displays a purple arrow pointing in the positive direction when you select the edge or curve. If you want to reverse the positive X direction, select the edge or curve again. The illustration shows a beam with a square cross-section defined along a curve that parallels, but is opposite in sign to, the WCS X axis. The software uses the beam X axis and the Y direction you specify on the Beam Definition dialog box to define an XY plane for the beam action coordinate system. It then defines a Z axis perpendicular to the XY plane, and completes the coordinate system using the righthand rule. 969 Structural and Thermal Simulation - Help Topic Collection Shell Normals Use the Surfaces selector arrow on the Shell Definition dialog box to display the normal direction for each shell and to change the direction for one or more shells. Because Mechanica sets the normal direction separately for each shell when you create it, the direction of the normals for adjoining shells may end up in opposite or inconsistent directions. See Normal Direction for Surfaces and Shells for information on how Mechanica creates and uses normal directions. You can fix or flip the shell normals if your shell is not part of a volume, or part of a shell pair in a midsurface compressed model. When you use the Surfaces selector arrow to select the shell on your model, a magenta arrow appears displaying the normal direction. Do one of the following to fix or flip the normal direction: • • Select the shell, and then select the shell again to flip the direction of the arrow that shows the normal direction. On the SIM SELECT menu, select Fix Normals or Flip Normals. Mechanica checks if you have fixed normals at certain points in the modeling process. To reverse the normal direction of a compressed midsurface, use the MODIFY PAIR Menu. Working with Functions Functions for Native Mode Functions Dialog Box Use this dialog box to create a new function or to copy, review, or delete a selected function. The type of function you can define depends upon the area of Mechanica where you are working. If you are working in FEM mode, see Functions Dialog Box for FEM Mode. The dialog box lists all functions of the specified type in your model. The dialog box also contains the following items: • New — Click this button to create a function. The Function Definition dialog box appears. There is no limit to the number of functions you can create for a given model. • Copy — Click this button to copy the function you select from the list. The Copy Function dialog box appears, displaying the name of the selected 970 Structural and Thermal Simulation • • function. Use the default or enter a name for the copy, then click OK. Mechanica adds the new name to the list. You cannot copy a system function. Edit — Click this button to edit or review the function you select. The Function Definition dialog box appears, containing the values you entered for the selected function. You cannot review a system function. Delete — Click this button to delete the currently selected function. You cannot delete a system function. If a description was entered for a selected function, it appears in the Description area below the list of functions. Function Definition Dialog Box Use this dialog box to create or edit a function. The Function Definition dialog box contains the following items: • • • • Name — Use the default or enter a function name. Description (optional) — Enter a description of the function. Coordinate system (not available for time-dependent functions) — Click the selector arrow to select a coordinate system to reference your function. Type — Select the type of function you want to create or review. Depending on your selection, the dialog box changes to display additional options: o o Symbolic — Enables you to enter a symbolic expression for the function. Table (not available for time-dependent functions or in FEM mode) — Enables you to enter data from a table for the function. • • • Definition — Use this area to define your function using a symbolic expression or table data. Available function components — Click this button to display the Symbolic Options dialog box. Review — Click this button to display the Graph Function dialog box. You can use this form to define the independent variables and values for your selected function. Following is an example of a function: if (time<10), sin (pi*time/5), 0) Symbolic Function Type If you select Symbolic as the type for your function, you enter an algebraic expression in the Symbolic entry box. Click the Available Function Components button to access the Symbolic Options dialog box. This dialog box contains the following: • independent variables, which correspond to the axes of the selected coordinate system. 971 Structural and Thermal Simulation - Help Topic Collection • constants, operators, and functions, which you can also find on the Symbolic Options dialog box. The expression cannot include another function or refer to the same function. Following is an example of a function: if (time<10, sin (pi*time/5), 0) For all functions, if you click the independent variable in the Variables box and the other symbols in their respective boxes, Mechanica places them in the Symbolic entry box. You can also type in the expression, using the Valid Symbols table as a guide. Note: For material properties, the only valid independent variable is temperature. Independent Variables The Variables box displays the name of the independent variable or variables available for the type of function you are defining. You can use these independent variables as part of the expression that defines the function. Valid Symbols You can use the following symbols when defining a symbolic function: Functions sin(x), cos(x), tan(x) asin(x) acos(x) atan(x) atan2(y,x) ln(x) log(x) abs(x) sqrt(x) 972 Definitions standard trigonometric functions arc sine in range – /2 to arc cosine in range 0 to /2 arc tangent in range – /2 to /2 arc tangent of y/x in range – to natural (base e) logarithm base 10 logarithm absolute value. If x>0 returns x, otherwise –x. square root Structural and Thermal Simulation Functions min(x,y) Definitions returns the minimum of x and y. If x<y returns x, otherwise y. returns the maximum of x and y. If x>y, returns x, otherwise y. sign transfer of y to x. If y<0 returns –abs(x), otherwise abs(x). remainder function, that is x–int(x/y)*y where int() means "integer part of". The sign of the result is always the same as the sign of x. "if" test, or switching function. If expression c (the "condition") returns non-zero (true) then the if function returns x, otherwise (if c=0.0) it returns y. Read like this: if c then x else y. limits x to be between bounds lo and hi. If x<lo returns lo, if x>hi returns hi, otherwise, returns x. lo must be <hi. provides a "dead zone" when x is between lo and hi. If x<lo returns x–lo, if x>hi, returns x–hi, otherwise returns 0. "ceiling" function, rounds toward positive infinity rounds toward negative infinity "nearness" test. Returns 1.0 (true) if x is within delta of y. If abs(x–y)<delta returns 1.0, otherwise returns 0.0. max(x,y) sign(x,y) mod(x,y) if(c,x,y) bound(x,lo,hi) dead(x,lo,hi) ceil(x) floor(x) near(x,y,delta) Constants: pi e Arithmetic Operators: + – add subtract, unary minus, negate = 3.14159... = 2.71828... 973 Structural and Thermal Simulation - Help Topic Collection Functions * / ^ Definitions multiply divide exponentiate Logical Operators (these operators return 1.0 for true, 0.0 for false): ! == != < > <= >= && || Grouping Operators: () parentheses, grouping unary "not" equal not equal less than greater than less than or equal to greater than or equal to logical and logical or Table Function Type If you select Table as your function type, you need to: • select an independent variable from the Value option menu Mechanica displays the name of the independent variable in this column. This is the independent variable you can use as part of the expression that defines the function. • enter at least one value for the independent variable in the independent variable column, which is on the left side of the table 974 Structural and Thermal Simulation Values in this column must be in either increasing or decreasing sequence, and you cannot use a single number more than twice. • • specify a function value in each row of the Value column. Enter a corresponding value for each dependent variable in this column. specify an interpolation method for the variables You can use these buttons with the table: • • • Add Row — adds up to 50 rows Delete — removes all rows you indicated Clear All — clears all values from both columns Interpolation Method Use this option to select the interpolation method for each variable. The first option menu specifies a method for the independent variable, and the second option menu for the dependent variable. Each option menu contains these two options: • • Linear — Mechanica linearly interpolates the variable between values. Log — Mechanica linearly interpolates the log of the variable between values. Graph Function Dialog Box Use this dialog box to specify settings for a graph of a function you are defining. Select an independent variable. Mechanica displays the Graph At entry box with an equal sign and displays this variable as the Range Limits for Variable. Enter a number in the Graph At entry box. You can also enter the word current for any independent variable that is a parameter. You can enter min, max, or current for any independent variable that is an independent parameter. Mechanica graphs the value of the equation versus the selected independent variable at the values of the remaining independent variables entered in the entry boxes. The dialog box also contains: • Range Limits for Variable x, y, or z — Specify the range you want to include on the graph by entering a lower and upper limit value for the independent variable. These limits should define a segment of the graph that enables you to visualize the function. For example, the limits could correspond to the time or frequency range you use in defining the analysis. Graph — Click this button to display the graph. Mechanica opens the Graphtool window and displays the graph. • 975 Structural and Thermal Simulation - Help Topic Collection To Create a Function Use this procedure to create a function in Mechanica. This procedure assumes you are in the Function Definition dialog box. 1. Use the default or enter a function name. 2. Enter a description of the function. This step is optional. 3. Use the default or select a coordinate system. (This option is not available for time-dependent functions.) 4. Select the type of function you want to create—Symbolic or Table. Functions for FEM Mode Functions Dialog Box (FEM mode) Use this dialog box to create a new function or to copy, edit, or delete an existing function. The dialog box lists all functions of the specified type in your model. The dialog box also contains the following items: • • New — Opens the Function Definition dialog box where you can create a new function. There is no limit to the number of functions you can create for a given constraint. Copy — Opens the Copy Function dialog box where you can copy the function you select from the list of functions. Use the default or enter a name for the copy. When you close the dialog box, Mechanica adds the new name to the list. You cannot copy a system function. Edit — Opens the Function Definition dialog box where you can edit or review the function you select. You cannot edit or review a system function. Delete — Deletes the currently selected function. You cannot delete a system function. • • If a description exists for a selected function, it appears in the Description area below the list of functions. Function Definition Dialog Box (FEM mode) Use this dialog box to create a new function or to edit or review an existing function. The Function Definition dialog box contains the following items: • • • Name — Use the default name or enter a new name for the function. Description (optional) — Enter a description of the function. Coordinate system — Click the selector arrow to select a coordinate system for your model. 976 Structural and Thermal Simulation • Definition — Use this area to define your function using an algebraic expression, that can contain only the following: o An independent variable listed on the Symbolic Options dialog box. Click the Available Function Components button to access the dialog box. o The constants, operators, and functions listed on the Symbolic Options dialog box. The expression cannot include another function or refer to the same function. The following is an example of a function: if (pi<10), sin (pi*pi/5), 0) For all functions, if you click the independent variable in the Variables box and the other symbols in their respective boxes, Mechanica places them in the Symbolic entry box. You can also type in the expression, using the Valid Symbols table as a guide. Independent Variables The Variables box displays the name of the independent variable or variables available for the type of function you are defining. You can use these independent variables as part of the expression that defines the function. Valid Symbols (FEM mode) You can use the following symbols when defining a symbolic function: Functions abs(x) acos(x) asin(x) atan(x) ceil(x) cos(x) Definitions absolute value. If x > 0 returns x, otherwise –x. arc cosine in range 0 to arc sine in range – /2 to /2 /2 arc tangent in range – /2 to "ceiling" function, rounds toward positive infinity standard trigonometric function (the argument x is in radians) rounds toward negative infinity natural (base e) logarithm floor(x) ln(x) 977 Structural and Thermal Simulation - Help Topic Collection Functions log(x) sin(x) Definitions base 10 logarithm standard trigonometric function (the argument x is in radians) square root standard trigonometric function (the argument x is in radians) hyperbolic trigonometric function hyperbolic trigonometric function hyperbolic trigonometric function sqrt(x) tan(x) sinh(x) cosh(x) tanh(x) exp(x) if(c, x, y) Constants: pi = 3.14159... Arithmetic Operators: + – * / ^ add subtract, unary minus, negate multiply divide exponentiate Logical Operators (these operators return 1.0 for true, 0.0 for false): ! == != < unary "not" equal not equal less than 978 Structural and Thermal Simulation Functions > <= >= & | Grouping Operators: () Definitions greater than less than or equal to greater than or equal to logical and logical or parentheses, grouping To Create a Function (FEM mode) This procedure assumes you are in the Function Definition dialog box. 1. Use the default or enter a function name. 2. Enter a description of the function (optional). 3. Click on the selector arrow to select the coordinate system you want the constraint to be relative to. 4. Enter an expression in the Definition text box. 5. Click OK to return to the Functions dialog box. To Create a Table Function This procedure assumes you are in the Function Definition dialog box. 1. Select Table. 2. Select an independent variable from the Value option menu. The independent variables correspond to the coordinate system axes. 3. Click Add Row. 4. Enter the number of rows you want to add. You can add rows to any location in the table by entering a value in Start At. 5. Enter a value for the independent variable in each row of the independent variable column. The values in this column must be in either increasing or decreasing order, and you cannot use a single number more than twice. 6. Specify a corresponding value for the dependent variable in each row of the Value column. 7. Specify an interpolation method for the variables. If you select Table, you can also import an ASCII file containing the table values. 979 Structural and Thermal Simulation - Help Topic Collection To Create a Symbolic Function This procedure assumes you have completed the preliminary steps in the Function Definition dialog box. 1. Select Symbolic. 2. Click Available Function Components to display the Symbolic Options dialog box. 3. Build your symbolic expression by clicking a variable and the appropriate constant, operator, and function. Clicking an item in any field displays the item in the Symbolic entry box on the Function Definition dialog box. Alternately, you can type a function into the entry box using the options shown on the Symbolic Options dialog box. Use of Function Definitions You can use the function definition utility to define equations that relate one quantity in Mechanica to another. For example, if you want to apply a load to your model, you can create an equation that describes the spatial distribution of the load. The following table lists the dialog boxes for which you can define functions: Command Product Independent variable time time or frequency frequency Dependent variable amplitude base excitation damping coefficient amplitude phase damping coefficient base excitation load set power spectral density damping coefficient base excitation base excitation Dynamic Time Analysis Definition Structure Dynamic Frequency Analysis Definition Structure frequency frequency frequency time or frequency Dynamic Random Analysis Definition Structure frequency frequency time or frequency Dynamic Shock Analysis Structure frequency 980 Structural and Thermal Simulation Command Product Independent variable Dependent variable Definition Material Structure (native mode only) temperature temperature temperature Young's modulus Poisson's ratio coefficient of thermal expansion spatial variation of force/moment load spatial variation of pressure load spatial variation of global temperature load spatial variation of structural temperature load translation and rotation directions bulk temperature Force/Moment Load Pressure Load Structure coordinates (WCS or UCS) coordinates (WCS or UCS) coordinates (WCS or UCS) Structure Global Temperature Load Structural Temperature Load Constraint Structure (FEM mode only) Structure (FEM mode only) coordinates (WCS or UCS) Structure (FEM mode only) Thermal (native mode only) Thermal (FEM mode only) coordinates (WCS or UCS) time Convection Condition coordinates (WCS or UCS) spatial variation of convection coefficient and bulk temperature spatial variation of emissivity and ambient temperature spatial variation of temperature spatial variation of heat load heat load Radiation Condition Thermal (FEM mode only) coordinates (WCS or UCS) Prescribed Temperature Heat Load Thermal coordinates (WCS or UCS) coordinates (WCS or UCS) time Thermal Thermal (native mode only) 981 Structural and Thermal Simulation - Help Topic Collection Additional Information Background Information Long-Term Limitations When you work with Mechanica, you should be aware of various limitations that affect the way the product operates. To learn about limitations, read the following: Topic General Limitations Model and Analyses Limitations General Limitations Following is a list of general limitations: • If your model is any of the following, you cannot enter Mechanica: o A part or assembly in a geometry or graphics simplified representation. o An assembly simplified representation that contains one or more components in geometry or graphics simplified representations. For each of these model types, the Applications>Mechanica command is inactive. To learn more about simplified representations, see the Assembly and Welding functional area in the Pro/ENGINEER Help Center. • If you use the Set Working Directory command on the Pro/ENGINEER File menu to change directories during a Mechanica session, be aware that Mechanica may still refer to the original directory for certain operations. For example, assume you have a study results directory named study in two different directories—a and b. If you were working in directory a and decided you wanted to review the study results in directory b, you would normally use the Set Working Directory command to switch directories. However, although Mechanica switches directories, it still sees the study results directory that resides in directory a, and these would be the results the software would display unless you specifically select directory b when defining your result windows. 982 Structural and Thermal Simulation Model and Analyses Limitations Following is a list of limitations that covers the models and analyses: • • • • • There are limitations in the ability of Mechanica and Pro/ENGINEER to share materials. Native mode and FEM mode of Mechanica share some, but not all, modeling entities. For assemblies, you cannot apply loads or constraints to a merged surface unless you first define a region to separate the unmerged portion of the surface. Native mode does not support variable-thickness shell modeling. You cannot define compressed shell midsurfaces for structural assemblies unless you first start Mechanica from part mode and predefine pairs for each of the parts in the assembly. You then leave part mode and start Mechanica from assembly mode to add modeling entities and analyze the assembly as a whole. You cannot create beam–face links. • 983 Structural and Thermal Simulation - Help Topic Collection Icons Used in Mechanica When you create most modeling entities, Mechanica adds icons to your model in the work area to indicate the presence of the entity and its associations. The following topics illustrate and briefly describe most of the icons used in the Mechanica work area. This discussion does not cover beam section icons. You can learn about beam section icons by reading the online help for the beam section you are interested in. Topic Icons Common to Structure and Thermal Icons Specific to Structure Icons Specific to Thermal Icons Common to Structure and Thermal Refer to the following topics for descriptions of icons and default graphic representations that are common to Structure and Thermal: Topic Coordinate Systems Connections Constraints Material Orientations Coordinate Systems Following are the icons Mechanica uses to represent coordinate systems. Mechanica displays coordinate systems in yellow. If you designate a coordinate system as the current coordinate system, Mechanica highlights this coordinate system in green. 984 Structural and Thermal Simulation World Coordinate System or Cartesian User Coordinate System This icon appears when you create a Cartesian coordinate system. This icon also represents the WCS. The icon changes orientation, but not scale, in response to view changes. Cylindrical User Coordinate System This icon appears when you create a cylindrical coordinate system. The icon changes orientation, but not scale, in response to view changes. Spherical User Coordinate System This icon appears when you create a spherical coordinate system. The icon changes orientation, but not scale, in response to view changes. Connections Following are the graphic representation Mechanica uses for connections: Welds This icon appears when you create an end or perimeter weld between components in an assembly. The icon changes orientation, but not scale, in response to view changes. Spot Welds This icon appears when you create a spot weld between entities. The size of the disks in this icon depend on the diameter you specify for the spot weld. The icon changes orientation in response to view changes. Spot welds are only available in native mode. 985 Structural and Thermal Simulation - Help Topic Collection Interfaces This icon appears when you create an interface between components in an assembly. The version without dots represents a free interface while the version with dots represents a bonded interface. The icon changes orientation, but not scale, in response to view changes. Rigid Connections This icon appears when you create a rigid connection between components in an assembly. The icon changes orientation, but not scale, in response to view changes. Rigid connections are only available in native mode. Rigid and Weighted Links This icon appears when you create a rigid or weighted link between components in an assembly. The icon changes orientation, but not scale, in response to view changes. Rigid and weighted links are only available in FEM mode. Constraints Structure and Thermal have only one type of constraint in common—cyclic symmetry. Following is the default icon Mechanica uses for cyclic symmetry: This icon appears at each location where you apply a cyclic symmetry constraint. The icon does not change orientation or scale in response to view changes. Material Orientations Following is the graphic representation Mechanica uses for material orientation. This icon appears when you review the material orientation of a surface, shell, or part. The icon changes orientation, but not scale, in response to view changes. 986 Structural and Thermal Simulation Icons Specific to Structure Refer to the following topics for descriptions of icons and default graphic representations that are specific to Structure: Idealizations Following are the default icons Structure uses for mass and spring idealizations: Masses This weight shape represents a mass concentrated at a point. The mass icon does not change orientation or scale in response to view changes. Springs (advanced and simple) This coil represents a spring between two points. The icon changes orientation, but not scale, in response to view changes. Note that the spring orientation is indicated by arrow vectors at one end of the icon. Springs (to ground) This coil, extending at one end to a point and at the other end to ground, represents a spring connected to ground. The icon does not change orientation or scale in response to view changes. Gaps (point to entity) This icon appears when you define a gap between a point and another entity. The arrow branches indicate gap orientation and the "x" indicates the reference point. The icon changes orientation, but not scale, in response to view changes. Gaps are only available in FEM mode. Gaps (surface to surface) This icon appears when you define a gap between two surfaces. The icon changes orientation, but not scale, in response to view changes. Gaps are only available in FEM mode. 987 Structural and Thermal Simulation - Help Topic Collection Connections Structure has only one connection that it does not share with Thermal, namely contacts. Following is the default icon Structure uses for contact regions: This icon appears when you define a contact region between two curves in a 2D model or between two surfaces in a 3D model. The icon does not change orientation or scale in response to view changes. Contacts are only available in native mode. Constraints Following are the default icons that Structure uses for constraints: Constraints This icon appears at each location where you apply a constraint. The icon does not change orientation or scale in response to view changes. This icon shows which degrees of freedom you constrained. Two rows of boxes appear at the base of the triangle, with each box representing a degree of freedom. The top row of boxes represents displacement degrees of freedom, and the bottom row of boxes represents rotational degrees of freedom. Boxes corresponding to degrees of freedom that you constrained or for which you prescribed a displacement are filled. Boxes corresponding to degrees of freedom that you designated as free are empty. For example, this icon indicates that displacement in the x and y directions are constrained and rotation about the z axis is also constrained. Mirror Symmetry Constraints This icon appears at each location where you apply a mirror symmetry constraint. The icon does not change orientation or scale in response to view changes. 988 Structural and Thermal Simulation Along Surface Constraints This icon appears at each location where you apply an Along Surface constraint. The icon does not change orientation or scale in response to view changes. Along Surface constraints are available in FEM mode only. Loads Following are the default icons that Structure uses for loads: Force Loads This icon, with a single arrowhead, appears on an entity to which you apply a force load. The icon changes orientation, but not scale, in response to view changes. Moment Loads This icon, with a double arrowhead, appears on an entity to which you apply a moment load. The icon changes orientation, but not scale, in response to view changes. Total Load At Point This icon appears on an entity to which you apply a force or moment load, associate the load to entities, and specify Total Load At Point as the distribution method. Mechanica displays the icon as a yellow arrow pointing in the direction of the force vector. It does not change orientation or scale in response to view changes. Total Load At Point distributions are only available in native mode. Gravity Loads This icon appears when you apply a gravity load to your model. The vector changes orientation, but not scale, in response to view changes. Structure places this icon at the WCS origin. Centrifugal Loads (Velocity) This icon appears when you apply a centrifugal velocity load to your model. The icon changes orientation, but not scale, in 989 Structural and Thermal Simulation - Help Topic Collection response to view changes. Centrifugal Loads (Acceleration) This icon appears when you apply a centrifugal acceleration load to your model. The icon changes orientation, but not scale, in response to view changes. Global Temperature Loads This icon appears when you apply a global temperature load to your model. The icon does not change orientation or scale in response to view changes. Structure places this icon at the WCS origin. MEC/T Temperature This icon appears when you apply a MEC/T temperature load to your model. The icon does not change orientation or scale in response to view changes. Structure places this icon at the WCS origin. MEC/T temperature loads are only available in native mode. External Temperature This icon appears when you import an externally calculated or measured temperature load to your model. Structure places this icon near the WCS origin. Structural Temperature This icon appears distributed across the entity when you create a structural temperature load. Structural temperature loads are only available in FEM mode. Pressure Loads When you apply a pressure load, this arrow-type icon appears normal to shells, faces, and surfaces, or perpendicular to edges or 2D shells. The icon changes orientation, but not scale, in response to view changes. 990 Structural and Thermal Simulation Icons Specific to Thermal Following are the default icons specific to Thermal for prescribed temperatures, convection conditions, and heat loads: Prescribed Temperatures This icon appears on an entity for which you prescribe a temperature. This icon does not change orientation or scale in response to view changes. Convection Conditions This icon appears on an entity for which you define a convection condition. This icon does not change orientation or scale in response to view changes. Radiation This icon appears on an entity for which you define a radiation boundary condition. This icon does not change orientation or scale in response to view changes. Radiation boundary conditions are available in FEM mode only. Heat Loads This icon appears on an entity to which you apply a heat load. It does not change orientation or scale in response to view changes. The sign on the icon indicates whether the load magnitude is positive or negative, that is, a heat source or a heat sink. For spatially varying loads, which may change sign, the sign on the icon corresponds to the sign of the entry for Q, which multiplies the interpolation. 991 Structural and Thermal Simulation - Help Topic Collection Bibliography This document contains a bibliography of information on topics relevant to Mechanica. The bibliography is divided into the following sections: Topic General Finite Element Fatigue P-method Optimization Mechanics Formulas and Numerical Results Heat Transfer General Finite Element Bathe, Klaus-Jurgen. Finite Element Procedures in Engineering Analysis. Englewood Cliffs, NJ: Prentice-Hall, 1982. Bonet, Javier, and Richard D. Wood. Nonlinear Continuum Mechanics for Finite Element Analysis. New York: Cambridge University Press, 1997. Hughes, Thomas J.R. The Finite Element Method: Linear Static and Dynamic Finite Element Analysis. Englewood Cliffs, NJ: Prentice-Hall, 1987. Kardestuncer, H., and Norrie, D. H., eds. Finite Element Handbook. New York: McGraw-Hill, 1987. Zienkiewicz, O.C. The Finite Element Method. New York: McGraw-Hill, 1988. Fatigue Baumel, A. and Seeger, T. "Materials Data for Cyclic Loading, Supplement 1." Materials Science Monographs, 61. Pub: Elsavier. Morrow, J. "Fatigue Design Handbook." Advances in Engineering. Vol. 4. Society of Automotive Engineers, Warrendale, PA. (1968): Sec 3.2, pp 21–29. 992 Structural and Thermal Simulation Smith, K. N., Watson, P., and Topper, T. H. "A Stress-Strain Function for the Fatigue of Metals." Journal of Materials. Vol. 5, No. 4, (1970): 767–778. p-Method Babuska, I., and Suri, M. "The p- and h-p Versions of the Finite Element Method, an Overview." Computer Methods in Applied Mechanics and Engineering. 80 (1990): 5– 26. Babuska, I., and Szabo, B. "On the Rates of Convergency of the Finite Element Method." International Journal for Numerical Methods in Engineering. 18 (1982): 323–341. Babuska, I., Szabo, B., and Katz, I. N. "The p-Version of the Finite Element Method." Society for Industrial and Applied Mathematics. (1981): 515–545. Szabo, B. "Geometric Idealizations in Finite Element Computations." Communications in Applied Numerical Methods. 4 (1988): 393–400. Szabo, B. "Mesh Design for the p-Version of the Finite Element Method." Computer Methods in Applied Mechanics and Engineering. 55 (1986): 181–197. Szabo, Barna, and Ivo Babuska. Finite Element Analysis. New York: Wiley, 1991. Szabo, B., and Sahrmann, G. "Hierarchic Plate and Shell Models Based on pExtension." International Journal for Numerical Methods in Engineering. 26 (1988): 1855–1881. Optimization Bennett, J.A., and M.E. Botkin. The Optimum Shape. New York: Plenum, 1986. Haug, Edward J., and Jasbir S. Arora. Applied Optimal Design. New York: Wiley, 1979. Haug, Edward J., Kyung K. Choi, and Vadim Komkov. Design Sensitivity Analysis of Structural Systems. London: Academic Press, 1986. Vanderplaats, Garret N. Numerical Optimization Techniques for Engineering Design. New York: McGraw-Hill, 1984. Wismer, David A., and R. Chatterly. Introduction to Nonlinear Optimization. New York: North-Holland, 1983. 993 Structural and Thermal Simulation - Help Topic Collection Mechanics Gere, James M., and Stephen P. Timoshenko. Mechanics of Materials. 2nd ed. Monterey, CA: Brooks/Cole Engineering Division, 1984. Jones, Robert M. Mechanics of Composite Materials. Washington, D.C.: Scripta Book Company, 1975. Popov, E. P. Introduction to Mechanics of Solids. Englewood Cliffs, NJ: Prentice-Hall, 1968. Reddy, J. N. Energy and Variational Method in Applied Mechanics. New York: John Wiley & Sons, 1984. Shigley, Joseph Edward Mechanical Engineering Design. 3rd ed. New York: McGrawHill, 1977. Timoshenko, S. P., and J.N. Goodier. Theory of Elasticity. New York: McGraw-Hill, 1970. Tsai, Stephen W. Composites Design. 4th ed. Dayton, OH: Think Composites, 1988. Tsai, Stephen W., and H. Thomas Hahn. Introduction to Composite Materials. Westport, CT: Technomic Publishing Co., 1980. Ugural, A. C. Stresses in Plates and Shells. New York: McGraw-Hill Book Company, 1981. Formulas and Numerical Results Blevins, Robert D. Formulas for Natural Frequency and Mode Shape. New York: Van Nostrand Reinhold Co., 1979. Roark, Raymond J., and Warren C. Young. Formulas for Stress and Strain. 5th ed. New York: McGraw-Hill, 1975. Heat Transfer Holman, J. P. Heat Transfer. 6th ed. New York: McGraw-Hill, 1986. Incropera, Frank P., and David P. Dewitt. Fundamentals of Heat Transfer. New York: Wiley, 1981. Kreith, Frank, and Mark S. Bohn. Principles of Heat Transfer. 4th ed. New York: Harper & Row, 1986. 994 Structural and Thermal Simulation The Database Database Considerations To support the many activities it performs, Mechanica adds information to existing Pro/ENGINEER files and creates database files in the directory that stores your Pro/ENGINEER part or assembly. To learn about Mechanica database files, how the software maintains the database, and other related issues, read the following: Topic Native Mode Files Using Pro/ENGINEER File Commands FEM Database Considerations Support for Pro/INTRALINK and Windchill In reading this material, bear in mind that you do not need an in-depth understanding of the Mechanica database in order to work with your model. Treat these discussions as background information only. Native Mode Files For native mode, the software creates many files as it proceeds through the menus and commands. Some of these files store part or assembly information, including simulation information, others store mesh and results information, while still others store a record of the session. The following files contain most of your model data and results data: • • Model files — Mechanica stores simulation information in Pro/ENGINEER .prt files (part mode) and .asm files (assembly mode). Model with mesh files — When you run an analysis or design study, Mechanica creates a study directory and copies the .prt or .asm file to that directory. In the course of the run, the software generates a separate model file that includes geometry, simulation entities, and the mesh generated during the run. This type of model file is called .mdb (part mode) or .mda (assembly mode). 995 Structural and Thermal Simulation - Help Topic Collection The most important thing to bear in mind is that these files are paired—.prt files with .mdb files and .asm files with .mda files. Following is a brief summary of the purpose of each file: • • .prt file — This file stores information about part geometry and all simulation entities for the part. .mdb file — The content of this file depends on whether or not you have actually run an analysis or design study. When you begin a run or create a mecbatch file, the .mdb file contains a subset of simulation entities such as measures, materials, analysis definitions, and so forth. Once the analysis or design study begins to run, Mechanica updates this file to include the model mesh. .asm file — This file stores information about assembly geometry and all simulation entities for the assembly. .mda files — As with the .mdb file, the content of these files depends on whether or not you have actually run an analysis or design study. When you begin a run or create a mecbatch file, the .mda file contains a subset of simulation modeling entities for your assembly. Once the analysis or design study begins to run, Mechanica updates this file to include model mesh. • • To help prevent data loss and enable you to return to a prior model if you encounter problems, the software creates .prt or .asm backups each time you perform a save through the Pro/ENGINEER File menu. The backup files are as follows: • .prt and .asm files — an earlier version of the file. For the most recent backup, use the file with the next-to-highest number, although you can also access an earlier version of the part or assembly by opening files with lower numbers. Session files — Each session of Pro/ENGINEER or Mechanica generates one session record, or playback file in case you need to replay a session. Pro/ENGINEER and Mechanica use a trail.txt.X (where X is an interger) file to store session records. The software starts a new trail.txt.X file at the beginning of each session, incrementing the integer to create a unique identity. • To learn more about the file structure and some of the guidelines you should observe as you work with these files, read the following: Topic Overview of File Creation Starting a New Model Moving to Independent Mode 996 Structural and Thermal Simulation Overview of File Creation To give you an understanding of when Mechanica creates files, the following discussion guides you through the Mechanica process from a file creation perspective, as started from part mode. Note: File creation is similar for assembly mode, so simply substitute appropriate file extensions to see how file creation takes place in assembly mode. 1. When you open Pro/ENGINEER, the software creates a trail file, trail.txt.x, which tracks your actions in Pro/ENGINEER. The software stores this file in the current directory. 2. When you create and save a part, Pro/ENGINEER saves the geometry, relations, and so forth in a part (.prt) file, which it stores in the pro directory (where pro is the directory that contains the Pro/ENGINEER part). 3. After you enter Mechanica, the software stores Mechanica entities that you add to the part—modeling entities, analysis definitions, and design study definitions—in the .prt file. It stores this data each time you save the model. 4. When you run an analysis or design study, Mechanica creates a study directory (where study is the name of your design study). The software then copies the .prt file into this directory, creates an .mdb file, and merges the simulation information from the .prt file into the .mdb file. The .mdb file that appears in the study directory carries the study name. However, the .prt file that appears in the study directory carries the original name of the part. As Mechanica runs the analysis or design study, it updates the .mdb file by adding mesh data. Mechanica uses this information to display model results. Starting a New Model If you need to start a fresh model for the part or assembly, you can use the New Simulation Model command on the File menu. This command deletes the simulation information in the .prt or .asm file, eliminating most modeling entities for the part or assembly. Note: Do not use the New Simulation Model command if you are trying to delete individual modeling entities. Reserve this command for situations where your model requires deep-level cleanup. Moving to Independent Mode If you decide to work with your model in independent mode, use the File>Independent Mechanica command to start a separate Mechanica user interface. Mechanica merges all model information—whether your model is a part or assembly—into an .mdb file that becomes your independent mode model file. This 997 Structural and Thermal Simulation - Help Topic Collection operation creates a complete Mechanica database file that you can no longer use in integrated mode. Using Pro/ENGINEER File Commands Following is a list of actions Mechanica takes when you use the model management commands on the Pro/ENGINEER File menu. Mechanica takes these actions only if the current Mechanica model is associated with the Pro/ENGINEER part or assembly being saved, erased, and so forth. Note: While Mechanica is active, the only commands you can select from the list below are Save, Save a Copy, Backup, and Delete. To use the other commands, you must select a different Pro/ENGINEER application. File menu option Erase Delete Action taken by Mechanica This command provides two options—Current and Not Displayed. Both options close the Mechanica model without saving. This command provides two options—Old Versions and All Versions. Delete All Versions closes and deletes the Mechanica model. If there is no Mechanica model in memory but one exists on disk, the software deletes that model. Delete Old Versions has no effect in Mechanica. Save Save A Copy Saves the Mechanica model. Saves the Mechanica model under the new name. The name of the Mechanica model in memory does not change. If there is no Mechanica model in memory but a file of that name exists, the software copies the file to a new name matching the new Pro/ENGINEER part. If you have accessed Mechanica at least once during the current Pro/ENGINEER session, saves a backup of the Mechanica model in a directory you specify. Backup FEM Database Considerations As you perform the three phases of finite element modeling (preprocessing, processing, and postprocessing), a number of different files are added to the Pro/ENGINEER database. This section lists and describes these files. To learn more about FEM files, read the following: Topic Files Output to FEA Programs 998 Structural and Thermal Simulation Miscellaneous FEM Mode Database Files By default, all files you create by using Mechanica FEM mode have the format "modelname.ext," where modelname is the name of the current model and ".ext" is a three-character extension indicating the file type. Files Output to FEA Programs Following is a list of files that are output by Mechanica FEM mode meshing for export to an offline finite element analysis program or by FEM mode postprocessing directly to an online finite element analysis program. File modelname.ans modelname.nas modelname.fnf Description ANSYS output file MSC/NASTRAN output file FEM Neutral output file Miscellaneous FEM Mode Database Files Following is a list of various files that are generated in FEM mode during the finite element modeling process. File modelname.bde Description File listing problem mesh elements that fail a requested quality check File containing mesh data of a part File containing mesh data of an assembly File containing model mesh and results data File listing a definition of your model and finite element results statistics Plot file output from postprocessing modelname.fmp modelname.fma modelname.frd modelname.inf modelname.plt 999 Structural and Thermal Simulation - Help Topic Collection Support for Pro/INTRALINK and Windchill Integrated mode and FEM mode Mechanica support direct access of certain files to an active Pro/INTRALINK workspace. These include Mechanica part and assembly model files, and files associated with meshing in integrated mode and FEM mode. Mechanica also supports access to Windchill. Other files that you generate in Mechanica, and which are discussed elsewhere in this document and in Files Created by Mechanica, including result files, study directories,and property library files, are not supported for Pro/INTRALINK or Windchill access. To learn more about file support, read the following: Topic Model Files Meshing Files FEM Mode Meshing Files Support for Windchill Model Files • • When you enter Mechanica, model files, .prt and .asm, are read from the active workspace. If your active workspace does not contain a Mechanica model, but there is a model on disk in the current working directory, it will be read from disk and checked into the workspace. In either case, when you save your model, Mechanica writes it to the active workspace. The software also automatically creates a Pro/INTRALINK dependency between a Mechanica model and its associated Pro/ENGINEER model when it saves the model to your active workspace. Mechanica reads certain auxiliary files from the workspace, such as those containing temperature fields for structural analysis. These files are not written to the workspace, so you must either check these files out of common space or import them into a workspace before Mechanica can access them directly. Meshing Files If you are working in Pro/INTRALINK, the following points apply to your AutoGEM .mmp and .mma files in Mechanica. • Associating files — There is no dependency established between a part or assembly file and a mesh file when you import them from a directory into your workspace. To establish an association: 1. Import both files into your workspace. 1000 Structural and Thermal Simulation • 2. Open the .prt or .asm file in your workspace. 3. Select AutoGEM>Create to open the AutoGEM dialog box. 4. Select File>Load Mesh on the AutoGEM dialog box to open the mesh file (.mmp or .mma). 5. Select File>Save Mesh on the AutoGEM dialog box to save the mesh file in your workspace. 6. Check the part or assembly files and the mesh files into the commonspace. Saving files — If you have checked out a part or assembly from commonspace into a workspace, when you select the File>Save Mesh command on the AutoGEM dialog box to save a new mesh file, the .mmp or .mma file is saved into the same workspace. If you retrieved the mesh file from commonspace, when you select the File>Save Mesh command on the AutoGEM dialog box, the software checks the mesh file out and then saves it to the same workspace. • Retrieving files — Here are the rules that Mechanica uses to determine which mesh file to retrieve when you open a mesh file and a part file in your Pro/INTRALINK workspace. o If you check out both the mesh file and the model file from commonspace into your workspace at the same time, and then open Mechanica, the software tries to check out the latest version of the mesh file that is compatible with the model file. If it cannot find an appropriate version of the mesh file, it uses the version of the mesh file that is specified by the user configuration. o If you check out a model file from commonspace into your workspace without simultaneously checking out a mesh file, open Mechanica, and then use the AutoGEM dialog box to retrieve a mesh file, the software will try to find a compatible mesh file. If no appropriate file is available, Mechanica displays an error message. o If you check out a mesh file from commonspace into your workspace without checking out a model file, the software automatically checks out an associated model file. FEM Mode Meshing Files If you are working in Pro/INTRALINK, the same rules apply to saving and retrieving your FEM mode .fmp and .fma files as discussed above for .mmp and .mma files. If you work with hierarchical meshes, when you check out an assembly from a workspace, the software checks out both the meshes saved for the parts and the meshes saved for the assembly. Support for Windchill If you are working in Windchill, the following points apply to your AutoGEM .mmp and .mma files in Mechanica. • When you create a mesh file, it is added to the same Windchill document as the Mechanica model file. 1001 Structural and Thermal Simulation - Help Topic Collection • • When you retrieve a part or assembly file from a Windchill cabinet, the latest version of the .mmp or .mma file corresponding to the model file is also retrieved. If you update a .mmp or .mma file, the version number of the Windchill document is incremented. The behavior when you retrieve or save .fma and .fmp files is identical to that for the .mmp and .mma files. 1002 Structural and Thermal Simulation Files Created by Mechanica This document lists files created by Mechanica and explains their purpose. Each of the following topics covers a different type of file: Topic Engine Files Library Files Results Files AutoGEM Files FEM Mode Files Miscellaneous Files Engine Files Refer to the following topics for information on different categories of engine files: Topic mecbatch Engine Input Files Temporary Engine Files Engine Output Files mecbatch The mecbatch command executes from your operating system the run of one or more design studies you previously included in a batch file. When you create a batch file, you can specify a name for the batch file or use the default name mecbatch (mecbatch.bat on Windows). Mechanica places the file in the directory from which you started Mechanica. 1003 Structural and Thermal Simulation - Help Topic Collection Engine Input Files Mechanica creates the following engine input files when you start a run of an analysis or design study (study represents the name of the design study you are running): study.mdb Contains a snapshot of the model database for your part at the time you start the analysis or design study. Contains a snapshot of the model database for your assembly at the time you start the analysis or design study. A transient file that enables Mechanica to reuse a mesh from an analysis or design study you had run previously. If you run the analysis or study as part of the Mechanica session, this file exists as a temporary conduit for the mesh and is deleted as soon as the analysis or study is underway. However, for batch runs, Mechanica does not delete this file. An empty file that locks the directory for results viewing when analysis or design study is running. The file is automatically deleted as soon as results are available. study.mda meshed_stdmdl.mdb study.lok Mechanica places the files in a directory called study, and places study in the directory for output files you specify through the Run>Settings command on the Analsyses and Design Studies dialog box. Temporary Engine Files During a design study run, Mechanica creates a series of temporary files with .tmp and .bas extensions. Mechanica places these files in a directory called study.tmp (study represents the name of the design study you are running). The software places study.tmp in the directory for temporary files you specify through the Run>Settings command on the Analsyses and Design Studies dialog box. Mechanica deletes the study.tmp directory when the run finishes successfully. If you stop a run in progress or Mechanica terminates a run because of an error, these files are automatically saved. Mechanica prompts you to delete any temporary files left over from a previous run when you start a new run of the same design study. 1004 Structural and Thermal Simulation Engine Output Files The Structure engine creates the following engine output files when you run a design study. These files are placed in one of three directories: • • • the study directory created during a run (where study is the name of the design study you run) the analysis subdirectory of the study directory (where analysis is the name of the analysis in that study) the step#### subdirectory of the study directory (where the four pound signs (####) represent the number of the master interval defined for the dynamic structural or transient thermal analysis in four-digit format) The Structure engine creates the following files: dpiupdtl.mdb Contains a snapshot of the model database if the engine replaced elements that became invalid during a global sensitivity study. If this happens, Mechanica uses the dpiupdtl.mdb file (rather than the study.mdb file) when you review results. Contains multi-pass and single-pass convergence information. For multi-pass adaptive, this file contains the final p-order of each edge and a list of edges and elements for which convergence was not achieved. Mechanica also lists the errors in edge displacements and strain energies, or temperatures and energy norms, depending on the type of analysis. For single-pass adaptive, this file contains the final p-order of each edge. For transient thermal analyses, there are multiple .cnv files displaying p-orders at every master interval where results are saved. These are stored in the step#### directory. study.dia Communicates an error code to the user interface in the event of a non-recoverable condition during the engine run. Contains displacements or temperatures, depending on the analysis type. The two pound signs (##) represent the load set or mode number in two-digit format. Contains the engine input echo along with non-recoverable conditions encountered during run time. Contains plotting data for global sensitivity. Mechanica reports values of measures at each design parameter step. The two pound signs (##) represent the design parameter number in two-digit format. 1005 study.cnv study.d## study.err study.g## Structural and Thermal Simulation - Help Topic Collection study.hst Contains information about model updates during an optimization or a sensitivity design study. Contains plotting data for local sensitivity. Two points give a linear sensitivity plot for each measure versus the selected design parameters. The two pound signs (##) represent the design parameter number in two-digit format. Contains data used to formulate results windows, including layer information. Contains the connectivity of the grid. Contains plotting data for optimization. Mechanica reports values of measures at every step of the optimization. Contains information similar to the study.stt file but is more detailed. Contains the connectivity information of the geometric element model. Contains values of measures for each analysis pass. Contains information about a run, including values of measures, warning messages, and, for optimization design studies, information about parameters and goal and limit quantities at each step of the optimization. You can access this file through the Info>Status command on the Analyses and Design Studies dialog box, or print out the file through your operating system. study.l## study.mcd study.neu study.opt study.pas study.pnu study.res study.rpt study.rst Contains the state of the last pass for a multi-pass adaptive analysis. Mechanica uses this file if you decide to restart an analysis that you had previously stopped. Contains information on solutions generated during an analysis. The study.solution file is in binary and is intended for internal engine use only. Mechanica refers to this file when performing analyses that rely on the solution of a previously run analysis. For example, to preform a buckling analysis, you must specify a previously run static analysis that the Structure engine uses to determine the BLF. During the buckling analysis run, the Structure engine locates and refers to the study.solution file generated by the static analysis you specified when you defined the buckling analysis. study.solution 1006 Structural and Thermal Simulation study.stt Contains the start and completion times of major steps in the engine run. You can access this file through detailed summary you can review using the Info>Status command on the Analyses and Design Studies dialog box. This file contains the stress/strain distribution or the fluxes and temperature gradients, depending on the analysis type. The two pound signs (##) represent in two-digit format the load set or mode number. study.s## study.ter Contains a summary of your model as it is seen during the engine run expressed in ASCII. The summary includes such items as loads, constraints, materials, and so forth. Contains plotting data for dynamic structural and transient thermal analyses. Measure values of response points are reported at successive time steps. The two pound signs (##) represent the load set or mode number in two-digit format. study.t## Mechanica also creates the following engine output files for structural analyses only: study.a## Contains the rotations. The two pound signs (##) represent the load set or mode number, in two-digit format. Contains the laminate stress/strain distribution calculated for a static, modal, dynamic time, dynamic frequency, dynamic random, dynamic shock, or buckling analysis. Mechanica calculates all quantities at the h-node locations and reports values with respect to the global rectangular coordinate system. The two pound signs (##) represent the load set number in two-digit format. Contains plotting data for frequency response. Measure values are reported at successive frequency steps. The two pound signs (##) represent the load set number in two-digit format. Contains the results for a fatigue analysis. Mechanica calculates all quantities at the h-node locations lying on the external surface of the model and reports values with respect to the global rectangular coordinate system. The two pound signs (##) represent the load set number in two-digit format. Contains the displacement phases from a dynamic frequency analysis. The two pound signs (##) represent the load set number in two-digit format. Contains the velocity phases from a dynamic frequency analysis. The two pound signs (##) represent the load set study.b## study.f## study.fatigue## study.h## study.i## 1007 Structural and Thermal Simulation - Help Topic Collection number in two-digit format. study.j## Contains the acceleration phases from a dynamic frequency analysis. The two pound signs (##) represent the load set number in two-digit format. Contains the rotation phases from a dynamic frequency analysis. The two pound signs (##) represent the load set number in two-digit format. Contains the rotational velocity phases from a dynamic frequency analysis. The two pound signs (##) represent the load set number in two-digit format. Contains the rotational acceleration phases from a dynamic frequency analysis. The two pound signs (##) represent the load set number in two-digit format. Contains reactions on constrained points and edges for static deformation or mode of vibration. The two pound signs (##) represent the load set or mode number in two-digit format. Contains the stress components distribution from a fatigue analysis expressed in ASCII. The two pound signs (##) represent the load set number in two-digit format. Contains information that the engine uses if you run a dynamic analysis using the Use Previous Modal or Dynamic Analysis option. Contains the velocity in a dynamic time or dynamic frequency analysis. The two pound signs (##) represent the load set or mode number in two-digit format. Contains the acceleration in a dynamic time or dynamic frequency analysis. The two pound signs (##) represent the load set or mode number in two-digit format. Contains the angular velocity in a dynamic time or dynamic frequency analysis. The two pound signs (##) represent the load set or mode number in two-digit format. Contains the angular acceleration in a dynamic time or dynamic frequency analysis. The two pound signs (##) represent the load set or mode number in two-digit format. Contains maximum/minimum principal stress directions in static, modal, dynamic time, dynamic frequency, shock or buckling analysis. The two pound signs (##) represent the study.k## study.m## study.q## study.r## study.ss## study.coe study.v## study.w## study.x## study.y## study.p## 1008 Structural and Thermal Simulation load set or mode number in two-digit format. study.n## Contains shell stress/strain results in static, modal, dynamic time, dynamic frequency, shock, or buckling analysis. The two pound signs (##) represent the load set or mode number in two-digit format. Contains static analysis solution information needed to reconstruct element stress during buckling analysis. Contains the material orientation information. Contains plotting data for contact analysis. Mechanica reports values of measures at each load increment. The two pound signs (##) represent the load set or mode number in two-digit format. study.buc study.mor study.c## Mechanica also creates the following engine output file for thermal analyses only: study.tld Contains information that the engine uses for structural analyses containing a thermal temperature load or temperaturedependent material properties. Library Files Mechanica creates and adds to the following library files when you place a material set, beam section set, shell property sets, or spring stiffness set in the library with the Add To Library button on the appropriate dialog box: mmatl.lib beam_section.bsf Contains material sets. Contains the definition of a beam section you create (where beam_section is the name of the beam section). The beam library contains one .bsf file for each beam you create. Contains shell property sets. Contains spring stiffness sets. mshlprp.lib mspstf.lib A default material library resides in the lib subdirectory of the Mechanica home directory. When you start a Mechanica product, Mechanica searches for library files in the following directories, in this order: • • • the lib subdirectory in the Mechanica home directory the text subdirectory in the Mechanica load point the current directory (the directory from which you started Mechanica) 1009 Structural and Thermal Simulation - Help Topic Collection • your home directory Mechanica uses the first copy of the appropriate configuration or library file it finds. If you choose to add a material, beam section, spring stiffness, or shell property to the library, Mechanica creates a new version of the appropriate library file as follows: • • If Mechanica finds the file in the current directory or your home directory, Mechanica replaces the existing file with the new version. If Mechanica finds the file in the lib subdirectory or does not find the file, Mechanica places the new file in your home directory. Results Files Individual Mechanica products create the following results files (file represents the name you assign to the file): file.rwd file.grt Contains the result window definitions you create and save. Contains in tabular form the XY values for a results graph you create for all Mechanica products. You create this file when you generate a graph report. AutoGEM Files Mechanica creates the following files when you use AutoGEM: model.agm Contains information about the most recent AutoGEM operation you executed for the current model. You can access the AutoGEM log file regardless of whether AutoGEM completed successfully or unsuccessfully, or you interrupted it. Mechanica saves the AutoGEM log file as model.agm (where model is the name of your model). Mechanica overwrites these files with each successive AutoGEM session. If you want to save a particular AutoGEM session, you can rename it through the operating system. untitled.agm Mechanica saves the AutoGEM log file as untitled.agm if you have not named your model. Mechanica overwrites these files with each successive AutoGEM session. If you want to save a particular AutoGEM session, you can rename it through the operating system. 1010 Structural and Thermal Simulation FEM Mode Files Mechanica FEM mode creates the following output files that you can export to an FEA program to perform a finite element analysis: model.ans Contains your model's mesh data in ASCII format. Use this output file with the ANSYS solver. Contains your model's mesh data in ASCII format. Use this output file with the MSC/NASTRAN solver. Contains information about an entire finite element model. Use the FEM Neutral output file to exchange data between Pro/ENGINEER and FEA programs. model.nas model.fnf In addition, Mechanica FEM mode creates the following files during the finite element modeling process. model.bde model.fmp Lists problem mesh elements that fail a requested quality check. Contains mesh data of a part. Mechanica creates this file in the current directory while generating the finite element mesh of your model. Contains mesh data of an assembly. Mechanica creates this file in the current directory while generating the finite element mesh of your model. Contains model's mesh and results data. Mechanica creates this file while performing a finite element analysis of your model. Lists a definition of your model and finite element results statistics. Contains plot file output from postprocessing. model.fma model.frd model.inf model.plt 1011 Structural and Thermal Simulation - Help Topic Collection Miscellaneous Files Mechanica creates the following files when you start the product: mech_trl.txt.X (where X is an interger) Contains playback information of your actions in Mechanica. Mechanica automatically creates this file in the current directory when you start the program. The software starts a new mech_trl.txt.X file whenever you begin a new Mechanica session. Customer support can use this file to diagnose any problems you might have while running Mechanica. 1012 Structural and Thermal Simulation Information Transfer Transferring Entities From Integrated Mode to Independent Mode This document describes how to transfer geometry, loads and constraints, and points out what to consider before you use the File>Independent Mechanica command to transfer a model from integrated mode to independent mode Mechanica. To learn about transferring these entities, read the following: Topic Transferring Geometry Geometry Transfer Limitations Transferring Loads and Constraints Import Considerations What Does Not Transfer Transferring Geometry To learn about transferring geometry, read the following: Topic Transferring Geometric Entities Importing Geometry into Mechanica 1013 Structural and Thermal Simulation - Help Topic Collection Transferring Geometric Entities The following table lists each Pro/ENGINEER geometric entity that transfers to Mechanica, and the equivalent entity in independent mode Mechanica: Pro/ENGINEER arc Bspline Bspline surface cone Coons patch cylinder face fillet surface surface of revolution line planar surface ruled surface spline spline surface tab cylinder torus cylindrical spline surface Mechanica arc NURBS NURBS surface revolved surface Coons surface ruled surface trimmed surface NURBS surface revolved surface line planar surface ruled surface piecewise Bezier curve piecewise Bezier surface ruled surface revolved surface Bezier surface 1014 Structural and Thermal Simulation If you transfer a Pro/ENGINEER part containing surface pairs, one midsurface transfers into independent mode Mechanica for each surface pair. The midsurface translates to the same type of surface in Mechanica as the original Pro/ENGINEER surfaces in the surface pair would. For example, a planar surface pair in Pro/ENGINEER transfers to a single planar surface in Mechanica. You can also transfer datum points, curves, and surfaces from Pro/ENGINEER to Mechanica. For datum surfaces, you can transfer datum surfaces created using Pro/SURFACE or import them from an IGES file. Importing Geometry into Mechanica When you import geometry into independent mode Mechanica, you should be aware of various factors that can affect how your geometry imports. To learn about importing geometry, read the following: Topic Internal and External Geometry General Rules Internal and External Geometry When geometry is first imported from Pro/ENGINEER, independent mode Mechanica marks it as external. Mechanica treats this geometry differently than geometry that originated in Mechanica (internal geometry) or that was imported from other MCAD systems. You cannot edit or delete external geometry. Mechanica displays an error message if you select external geometry to edit or delete. You can only modify external geometry through external design parameters. If you want to change external geometry in Mechanica, you need to save your model in Mechanica or, if you are working with a linked mode model from Release 2000i or earlier, use the Applications>Pro/ENGINEER>Unlink MCAD Model independent mode command to unlink the model from Pro/ENGINEER. General Rules Keep the following points in mind when importing your model into independent mode Mechanica: • When you import a surface, the defining curves may be trimmed away. You can check a surface's defining curves by reviewing a surface through the Entity command on the Review menu. You can return defining curves to your model using the Untrim Surface command on the Edit>Geometry menu. 1015 Structural and Thermal Simulation - Help Topic Collection • • After you import midsurface geometry into Mechanica, you should use the Review>Boundary Curves command to make sure there are no unintended cracks in your model. Cracks can occur if any curves and surfaces do not maintain their associations. When you import an assembly that contains mated surfaces, Mechanica merges the two surfaces into a single surface. If you create contacts for two parts with mated surfaces, Mechanica treats the two parts as separate, unmerged entities and places contacts on all surfaces it considers valid for the contact. Should you then decide to work with the model in independent mode, Mechanica eliminates any superfluous contacts when it merges the surfaces during import. • During import, Mechanica makes all surface normals consistent. For surfaces that are part of the boundary of a single volume, the normals are always set outward. Geometry Transfer Limitations Following is a list of limitations that affect the way that the interface transfers geometry: • Pro/ENGINEER models holes as negative masses. The holes can be located outside the enclosing solid. This can result in negative values for the mass and moments of inertia of the part. Because this is not physically possible, Mechanica assigns default values for mass and inertia matrices to the part when you transfer it. • • • • Mechanica approximates fillet surfaces imported from Pro/ENGINEER as NURBS surfaces. Mechanica approximates cylindrical spline surfaces in Pro/ENGINEER with Bezier surfaces. When you transfer midsurface geometry from Pro/ENGINEER to Mechanica, circles created in Pro/ENGINEER may transfer to arcs in Mechanica. If two datum surfaces overlap without a common trimming curve, Mechanica does not create associations between the two surfaces during import. Transferring Loads and Constraints If you create loads and constraints in the integrated mode of Mechanica and then start the full Mechanica product to use independent mode, the loads and constraints transfer to Structure. For information on creating loads, see About Loads, and for information on creating constraints, see About Structure Constraints or About Thermal Boundary Conditions. 1016 Structural and Thermal Simulation Import Considerations Before you transfer your part or assembly to Mechanica, you should be aware of the following: • Some of the geometry you import into Mechanica may not have the accuracy that Mechanica requires. In these cases, Mechanica uses the geometry's topological data to construct a valid model. If you delete any of the geometry that Mechanica has transformed, you may not be able to recreate it accurately because Mechanica's geometry creation facilities are not the same as those of Pro/ENGINEER. • • When you import geometry, Mechanica highlights, but does not merge, partly coincident curves so you can carry out any needed edits. When you import a part, you cannot use some of the Mechanica commands on the Geometry>Model>Design Variables, and Edit>Geometry menus. These commands are displayed as inactive. If you save your model in Mechanica or unlink the model from Pro/ENGINEER, these commands become available again. Mechanica provides a Settings dialog box that you use to define the characteristics of geometry imported from an MCAD product. This dialog box defines such characteristics as the tolerance Mechanica applies in determining whether to merge geometry, the maximum surface aspect ratio, and so forth. If you are not satisfied with the results of an MCAD import, varying these settings can improve the quality of the import. To access the Settings dialog box, use the File>Import>Settings command. • If you import intricate geometry, Mechanica attempts to delete surfaces that have an aspect ratio greater than 100:1 and a width less than 1/1000th of the model size. If you have very small surfaces that are larger than this, Mechanica will not delete them but may not be able to use AutoGEM efficiently. To specify a larger aspect ratio than the default just described, use the File>Import>Settings command to redefine the maximum surface aspect ratio. • • If a gap in your model is bigger than 1/1000th of the model size, Mechanica may not trim the surface at the gap. If it cannot trim the surface, Mechanica will not create a volume in your model. At times, two distinct nodes, edges, or faces in a single Pro/ENGINEER part are so close together that they must merge in Mechanica. When such a merge occurs, the .mnl file will contain one of the following warning messages (where name is the number of the entity or of the nodes, edges, or faces): Curve name is a boundary curve. or • 1017 Structural and Thermal Simulation - Help Topic Collection Curve name is partially coincident with another curve. Although the resulting model is a valid volume in Mechanica, the two nodes, edges, or faces are associated to each other, preventing the model from behaving as you intended it to. What Does Not Transfer The following aspects of your part do not transfer from integrated mode to your independent mode Mechanica model: • • Colors you assign to entities in Pro/ENGINEER Mass properties (Structure gets density values from Mechanica material properties, rather than from Pro/ENGINEER density definitions) 1018 Structural and Thermal Simulation FEM Neutral Format File This document describes how to use FEM Neutral Format files, with which you can exchange data between Mechanica and FEA programs. To learn about FME Neutral Format files, see the following: Topic About the FEM Neutral Format Defining an Object Sections of a FEM Neutral Format File About the FEM Neutral Format Use the FEM Neutral Format to create concise model descriptions by using the hierarchical file structure and references to data that is already defined. A FEM Neutral Format file contains information about an entire Finite Element Model, including the following data: • • • • • Definitions of element types and their topology Description of FEM topology (that is, nodes and elements) Properties Applied loads and constraints Calculated results Currently, Pro/ENGINEER outputs a FEM Neutral Format file containing information only about the model's mesh and loads/constraints. After you run a solver on the model, you must convert the solution results into FEM Neutral Format before the model is retrieved in Mechanica. Note: Pro/ENGINEER uses FEM Neutral Format revision 3. Consider the following conventions when you create your FEM Neutral Format file: • • FEM Neutral Format files have the extension .fnf. A FEM Neutral Format file has the following characteristics: o It is an ASCII file consisting of lines. o Each line contains 80 characters or less. o You can continue longer lines by using sub-lines. o End each sub-line with a backslash character (\), except for the last one. The FEM Neutral Format is case-insensitive. 1019 • Structural and Thermal Simulation - Help Topic Collection • Lines starting with a pound sign (#) as well as empty lines are treated as comments and are skipped (except for the first line). Information in a FEM Neutral Format file is organized into sections. Each section describes its own class of objects. The order of sections in the FEM Neutral Format file is critical because information from the earlier-defined sections may be required in the sections that follow. You can skip some of the sections that are not relevant to the model description. Note: The FEM Neutral Format is backward-compatible. A FEM Neutral Format file must start with an identification line used to recognize the FEM Neutral Format. The identification line format follows. #PTC_FEM_NEUT n <flags> where: n revision number of the FEM Neutral Format file (corresponds to the revision number of the specification). The default is 3. flags reserved for future use. An identification line can appear as follows: #PTC_FEM_NEUT 1 Include the creation date as a comment: #DATE Wed Mar 22 13:56:07 EET 2000 Defining an Object Define each object in a FEM Neutral Format file with "instructions." An instruction line starts with a percent sign (%). It consists of fields separated by spaces and/or tabulations. An instruction line includes the following components: • • • • instruction keyword indicating an instruction, for example, statistics obj_id integer handle of the object (this ID is not necessarily consecutive) key string definition used for a general definition of an object or another string specifying a feature of the object data object description (for example, placement, node ID, or element type) The format of an instruction is as follows: %instruction <obj_id key> [: data ...] 1020 Structural and Thermal Simulation Follow these general guidelines for writing instructions: • • Standard abbreviations may be used instead of full names of keywords. You can also define and use your own aliases. There may be cases when you need to skip a fieldfor example, when a particular field in an instruction is not applicable, or you want to use the system default for this field. To skip a field, enter an asterisk (*) in place of the data to be skipped. In this document, descriptions of the fields that can be replaced with an asterisk (*) are enclosed within angle brackets (< >), and the fields that can be omitted are enclosed in square brackets ([ ]) You can skip the final fields in an instruction by simply omitting them. Non-empty lines that begin with anything other than an asterisk (*) or a percent sign (%) are illegal and will generate an error. • • You can define an object using one instruction or a group of instructions. If you use a group of instructions, follow these guidelines: • • • If the object contains more than one instruction, you must combine the objects together as a group. You must assign the same instruction keyword obj_id to all instructions in the group. You must assign the key definition (DEF) to the first instruction in the group. To learn about the instructions and items you will work with in defining a FEM Neutral Format file, see the following: Topic List of Available Sections List of Available Instructions Special Instructions Definitions of Some Fields Used in Instructions List of Available Sections Sections in a FEM Neutral Format file must appear in the following order: • • • • • • • • • • HEADER General information about the file and FEM model. ELEM_TYPES Definition of element types. COORD_SYSTEMS Definition of coordinate systems. MATERIALS Definition of materials used in the model. PROPERTIES Definition of element properties used in the model. MESH Definition of the model's nodes and elements. MESH_TOPOLOGY Definition of the model's surfaces and edges. LOADS Description of applied load/constraint sets. ANALYSIS Definition of analysis types. RESULTS Description of solution results of the model. 1021 Structural and Thermal Simulation - Help Topic Collection List of Available Instructions The following table lists supported instructions, their standard abbreviations, and sections in which they may appear. Instruction Name START_SECT END_SECT END ALIAS TITLE STATISTICS ELEM_TYPE COORD_SYS MATERIAL ELEM_PROP ELEM_END_PROP NODE ELEM EDGE SURFACE LOAD_TYPE CON_CASE LOAD SOLUTION Abbreviation STS ENS END ALS TTL STT ETP CS MAT EP EEP ND EL EDG SRF LTP CC LD SLU outside a section before using an alias HEADER HEADER ELEM_TYPE COORD_SYSTEMS MATERIALS PROPERTIES PROPERTIES MESH MESH MESH_TOPOLOGY MESH_TOPOLOGY LOADS LOADS LOADS ANALYSIS Section Name 1022 Structural and Thermal Simulation Instruction Name RESULT_TYPE RESULT Abbreviation RTP RES Section Name RESULTS RESULTS In this document, abbreviations are shown in parentheses. For example: RESULT_TYPE (RES). Special Instructions FEM Neutral Format files include special instructions. To learn about these special instructions, see the following topics: Topic Start and End of a Section End Instruction Defining Aliases Start and End of a Section Each section starts with the instruction START_SECT (STS) and ends with the instruction END_SECT (ENS). A section will appear as follows: %START_SECT : section_name ... %END_SECT END Instruction The END instruction appears as follows: %END The END instruction is optional. In a FEM Neutral Format file, all lines appearing after END are skipped. 1023 Structural and Thermal Simulation - Help Topic Collection Defining Aliases The ALIAS (ALS) instruction is used to define aliases. You can define an alias for any keyword (instruction or key) and use it instead of the full name or abbreviation. Note: Do not create an alias with the name reserved for keywords and standard abbreviations: this results in an error. If several aliases are defined for a keyword, only the last one is considered valid. You can use only alphanumeric aliases. An alias is defined as follows: %ALIAS : keyword alias where: keyword = full name or its abbreviation. alias = user-defined alias. A Typical Alias %ALIAS : CON_CASE C %ALIAS : EL FEM_ELEMENT Definitions of Some Fields Used in Instructions FEM Neutral Format instructions can include any of several fields, depending on the instruction. To learn about some of these fields, see the following topics: Topic Referencing IDs Value Types Referencing IDs Use the following format to reference IDs of various geometry objects: • • 1024 elem_id ID of an element in the model (any positive number). node_id ID of a node in the model (any positive number). Structural and Thermal Simulation • • • node_in_el_id ID of a node in an element (in the range from 1 to num_nodes, where num_nodes is the number of element nodes). The order of nodes in the element is defined in the ELEM_TYPE instruction. edge_in_el_id ID of an edge in an element (in the range from 1 to num_edges, where num_edges is the number of element edges). The order of edges in the element is defined in the ELEM_TYPE instruction. face_in_el_id ID of a face in an element (in the range from 1 to num_faces, where num_faces is the number of element faces). The order of faces in the element is defined in the ELEM_TYPE instruction. Value Types Value_type appears in instructions describing applied loads/constraints and obtained results. Typically, the format is as follows: data_type <MASKABLE> where: data_type is one of the following: • • • • • SCALAR (SCL) VECTOR_2 (VEC2) a vector with two components VECTOR (VEC) a vector with three components VECTOR_6 (VEC6) a vector with 6 components TENSOR (TNS) MASKABLE indicates that the instruction may have skipped (not defined) components. MASKABLE can be defined for VECTOR_6 only. For TENSOR, defined in the XYZ coordinates, the order of the components is the following: TX, TY, TZ, TXY, TYZ, TXZ and the tensor is defined as: T(X,Y,Z) = TX*X*X + TY*Y*Y + TZ*Z*Z + 2*TXY*X*Y + 2*TYZ*Y*Z + 2*TXZ*X*Z The statement "Value corresponds to the given Value_type" means that the value is one of the following: • • • • 1 2 3 6 scalar if data_type in Value_type is SCALAR scalars if data_type in Value_type is VECTOR_2 scalars if data_type in Value_type is VECTOR scalars if data_type in Value_type is VECTOR_6 or TENSOR 1025 Structural and Thermal Simulation - Help Topic Collection Sections of a FEM Neutral Format File For the list of sections in a FEM Neutral Format file, refer to List of Available Sections. Currently, Pro/ENGINEER outputs a FEM Neutral format file containing all sections except RESULTS. A solver should create a file that contains all the information from the input file "model.fnf," and append to this information the ANALYSIS and RESULTS sections. You then end up with a file that contains all the information originally defined in the input file, as well as the ANALYSIS and RESULTS data. The solution results are expected to be in exact correspondence with model definitions. To learn about these sections and the instructions they can contain, see the following topics: Topic HEADER Section ELEM_TYPES Section COORD_SYSTEMS Section MATERIALS Section PROPERTIES Section MESH Section MESH_TOPOLOGY Section LOADS Section ANALYSIS Section RESULTS Section HEADER Section The HEADER section can contain the TITLE (TTL) and STATISTICS (STT) instructions. 1026 Structural and Thermal Simulation TITLE (TTL) Instruction This instruction appears as follows: %TITLE : Model_name where: Model_name is the name of the described model. A Typical Title %TITLE : bracket STATISTICS (STT) Instruction The STATISTICS (STT) instruction provides information about the number of element types, coordinate systems, materials, element properties, nodes, and elements in the model. This instruction has the following format: %STATISTICS : num_elem_types num_coord_systems num_materials\ num_properties num_nodes num_elements where: num_elem_types number of element types. num_coord_systems number of coordinate systems. num_materials number of materials used in the model. num_properties number of defined properties. num_nodes number of nodes in the model. num_elements number of elements in the model. A Typical Statistic %STATISTICS : 2 1 2 5 21 33 ELEM_TYPES Section The ELEM_TYPES section contains the ELEM_TYPE (ETP) instruction. 1027 Structural and Thermal Simulation - Help Topic Collection ELEM_TYPE (ETP) Instruction An element type description defines a topological scheme of an element. It consists of lines containing data about: • • • an element as an entity a line with the key DEF each edge lines with the key EDGE each face lines with the key FACE ELEM_TYPE Instruction with the DEF Key The ELEM_TYPE instruction with the key DEF has the following format: %ELEM_TYPE id DEF : Class Type <Sub_type> Num_corner_nodes \ Num_edges Num_faces where: Class is one of the following: • • • • SOLID (SOL) for tetrahedral elements SHELL (SHL) for triangle or quad elements BAR for elements with 2 nodes (for example, BEAM elements) POINT (PNT) for elements with 1 node (MASS or To Ground SPRING elements) Type is defined as shown in the following table of supported element types. Class SOLID SHELL TETRA (TET) TRIANGLE (TRI), QUAD (QUA) BAR SPAR, BEAM, GAP, ADV_BEAM (ADB), SPRING (SPR), Supported Types 1028 Structural and Thermal Simulation Class Supported Types ADV_SPRING (ADS) POINT MASS, TO GROUND SPRINGS Sub_type can be LINEAR (LIN) or PARABOLIC (PAR). The default is LINEAR. This field must be skipped if Class is BAR or POINT. Typical ELEM_TYPE Instructions %ELEM_TYPE 1 DEF : SOLID TETRA PARABOLIC 4 6 4 %ELEM_TYPE 3 DEF : SHELL QUAD LINEAR 4 4 2 %ELEM_TYPE 4 DEF : SHELL TRIANGLE PARABOLIC 3 3 2 %ELEM_TYPE 7 DEF : BAR GAP * 2 1 0 %ELEM_TYPE 8 DEF : POINT MASS * 1 0 0 ELEM_TYPE Instruction with the EDGE Key Note: The number of ELEM_TYPE instructions is equal to Num_edges given in the ELEM_TYPE instruction with the key DEF. The format of the ELEM_TYPE instruction with the key EDGE is as follows: %ELEM_TYPE id EDGE : edge_id Edge_placement where: id same as in the DEF line. Edge_placement lists the ID's of the element's end nodes and the ID of the mid-node (for PARABOLIC sub_type only) in the following format: node_in_el_id_1 node_in_el_id_2 <midnode_in_el_id> ELEM_TYPE Instruction with the FACE Key Note: The number of these instructions is equal to Num_faces, given in the ELEM_TYPE instruction with the key DEF. The format is the following: %ELEM_TYPE id FACE : face_id Face_placement 1029 Structural and Thermal Simulation - Help Topic Collection where: id same as in the DEF line. Face_placement consists of the ID's of the element's face edges in the counterclockwise direction, if looked at from the end of the positive normal to the face. The format is the following: edge_in_el_id_1 edge_in_el_id_2 ... Example of the ELEM_TYPE Instruction %ELEM_TYPE 2 DEF : SHELL TRIANGLE PARABOLIC 3 3 2 %ELEM_TYPE 2 EDGE : 1 1 2 4 %ELEM_TYPE 2 EDGE : 2 2 3 5 %ELEM_TYPE 2 EDGE : 3 3 1 6 %ELEM_TYPE 2 FACE : 1 1 2 3 %ELEM_TYPE 2 FACE : 2 1 3 2 COORD_SYSTEMS Section The COORD_SYSTEMS section contains the COORD_SYS (CS) instructions. COORD_SYS (CS) Instruction A description of a coordinate system includes five lines with the following keys: DEF, X_VECTOR, Y_VECTOR, Z_VECTOR, ORIGIN. COORD_SYS Instruction with the DEF Key This instruction has the following format: %COORD_SYS cs_id DEF [: <name> <type>] where: cs_id ID of the coordinate system (starting with 1). name (optional) name of the coordinate system. 1030 Structural and Thermal Simulation type is one of the following: • • • CARTESIAN (CAR)default CYLINDRICAL (CYL) SPHERICAL (SPH) COORD_SYS Instruction with the X_VECTOR Key This instruction has the following format: %COORD_SYS cs_id X_VECTOR : X_vect0 X_vect1 X_vect2 where: cs_id ID of the coordinate system (starting with 1). X_vect0, X_vect1, and X_vect2 global coordinates of the X-vector of the described coordinate system. The abbreviated form for X_VECTOR is X. COORD_SYS Instruction with the Y_VECTOR Key This instruction has the following format: %COORD_SYS cs_id Y_VECTOR : Y_vect0 Y_vect1 Y_vect2 where: cs_id ID of the coordinate system (starting with 1). Y_vect0, Y_vect1, and Y_vect2 global coordinates of the Y-vector of the described coordinate system. The abbreviated form for Y_VECTOR is Y. COORD_SYS Instruction with the Z_VECTOR Key This instruction has the following format: %COORD_SYS cs_id Z_VECTOR : Z_vect0 Z_vect1 Z_vect2 1031 Structural and Thermal Simulation - Help Topic Collection where: cs_id ID of the coordinate system (starting with 1). Z_vect0, Z_vect1, and Z_vect2 global coordinates of the Z-vector of the described coordinate system. The abbreviated form for Z_VECTOR is Z. COORD_SYS Instruction with the ORIGIN Key This instruction has the following format: %COORD_SYS cs_id ORIGIN : Orig0 Orig1 Orig2 where: cs_id ID of the coordinate system (starting with 1). Orig0, Orig1, and Orig2 global coordinates of the origin of the described coordinate system. The abbreviated form for ORIGIN is ORG. MATERIALS Section The MATERIALS section contains the MATERIAL (MAT) instruction. MATERIAL (MAT) Instruction The instruction MATERIAL with the key DEF specifies the material name and type. Each additional MATERIAL instruction contains a key indicating the name of the material property to be defined in this instruction. The following material properties are supported: • • • • • • • • • • • • • YOUNG_MODULUS (YNG) POISSON_RATIO (PSN) SHEAR_MODULUS (SHR) MASS_DENSITY (DNS) THERMAL_EXPANSION_COEFFICIENT (TEC) THERM_EXPANSION_REF_TEMPERATURE (TER) STRUCTURAL_DAMPING_COEFFICIENT (SDP) STRESS_LIMIT_FOR_TENSION (SLT) STRESS_LIMIT_FOR_COMPRESSION (SLC) STRESS_LIMIT_FOR_SHEAR (SLS) THERMAL_CONDUCTIVITY (THC) EMISSIVITY (EMS) SPECIFIC_HEAT (SHT) 1032 Structural and Thermal Simulation MATERIAL Instruction with the DEF key This instruction has the following format: %MATERIAL id DEF: mat_name <mat_type> where: id material ID (starting with 1). mat_name name of the material (up to 32 characters). mat_type type of material. Currently, the system supports only one type: ISOTROPIC (default). MATERIAL Instruction with the MAT_PROP Key This instruction has the following format: %MATERIAL id MAT_PROP : data where: id material ID (same as in the DEF line). Mat_prop one of the names of material properties (refer to MATERIAL (MAT) Instruction). data depends on Mat_prop. For all currently supported properties, there is one scalar value. Note: Material properties that are not defined are assumed to be zeros. Typical Material Instructions %MATERIAL 1 DEF : ALUM ISOTROPIC %MATERIAL 1 YOUNG_MODULUS : 1.900000E+07 %MATERIAL 1 POISSON_RATIO : 2.100000E-01 %MATERIAL 1 SHEAR_MODULUS : 7.850000E+06 %MATERIAL 1 MASS_DENSITY : 2.830000E-01 %MATERIAL 1 THERMAL_EXPANSION_COEFFICIENT : 6.780000E+00 1033 Structural and Thermal Simulation - Help Topic Collection %MATERIAL 1 THERMAL_CONDUCTIVITY : 1.000000E-02 PROPERTIES Section The PROPERTIES section may contain the following instructions: • • ELEM_PROP (EP) ELEM_END_PROP (EEP) ELEM_PROP (EP) Instruction The ELEM_PROP instruction defines element properties. The key (except when DEF) is the name of the property. For beam elements with additional end properties, the key REF can be used to reference instructions, defining the appropriate end properties (that is, ELEM_END_PROP). The supported element properties (keys of the ELEM_PROP instruction) are listed in the following table. Property Name THICKNESS CROSS_SECTION_AREA Abbreviation THI XSA Used for SHELL elements BEAM and ADV_BEAM elements MASS elements Moment of inertia in an elemental coordinate system for BEAM and MASS elements GAP elements GAP elements GAP elements SPRING elements SPRING elements ADV_SPRING elements MASS_VALUE MOMENT_OF_INERTIA MAS INE GAP_VALUE NORMAL_STIFFNESS SLIDE_STIFFNESS EXTENSIONAL_STIFFNESS TORSIONAL_STIFFNESS VECTOR_STIFFNESS GV NST SST EST TST VST 1034 Structural and Thermal Simulation Property Name DAMPING STRESS_RECOVERED Abbreviation DMP SRV Used for ADV_SPRING elements For ADV_BEAM elements, it may be one of: YES or NO. ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements SHEAR_STIFF_FACTOR_IN_XZ_PLANE SHEAR_STIFF_FACTOR_IN_XY_PLANE SHEAR_RELIEF_COEFF_IN_XZ_PLANE SHEAR_RELIEF_COEFF_IN_XY_PLANE SSZ SSY SRZ SRY ELEM_PROP Instruction with the DEF key This instruction has the following format: %ELEM_PROP id DEF: elem_type_id <name> where: id ID of the set of properties. elem_type_id ID of ELEM_TYPE for which the properties are defined. name name of this set of properties (if it is named). ELEM_PROP Instruction with the PROP_NAME Key This instruction has the following format: %ELEM_PROP id PROP_NAME : data where: id ID of the set of properties being defined. PROP_NAME one of the property names (refer to ELEM_PROP (EP) Instruction). The property name has to be valid for a given ELEM_TYPE, referenced in the line DEF. 1035 Structural and Thermal Simulation - Help Topic Collection data depends on the PROP_NAME: • • • • For MASS_VALUE, GAP_VALUE, NORMAL_STIFFNESS, SLIDE_STIFFNESS, EXTENSIONAL_STIFFNESS, TORSIONAL_STIFFNESS, and CROSS_SECTION_AREA, data is one scalar value. For THICKNESS, data is num_nodes scalar values, one per element node; values are in the order of node ID's within the element (num_nodes is the number of corner nodes for ELEM_TYPE, referenced in the line DEF). For MOMENT_OF_INERTIA, data is a one-vector (three scalars) value. For VECTOR_STIFFNESS and DAMPING, data is a one-vector (three scalars) value, defined in the coordinate system, referenced in the description of the element. Typical ELEM_PROP Instructions %ELEM_TYPE 2 DEF : SHELL TRIANGLE LINEAR 3 3 2 ... %ELEM_TYPE 3 DEF : BAR SPAR * 2 1 0 ... %ELEM_PROP 1 DEF : 2 %ELEM_PROP 1 THICKNESS : 0.5 0.6 1.0 ... %ELEM_PROP 2 DEF : 3 %ELEM_PROP 2 CROSS_SECTION_AREA : 0.01 ELEM_PROP Instruction with the REF Key This instruction has the following format: %ELEM_PROP id REF: node_in_el_id end_prop_id where: node_in_el_id is the node ID number inside the element. end_prop_idrefers to the corresponding ELEM_END_PROP instruction. 1036 Structural and Thermal Simulation ELEM_END_PROP (EEP) Instruction The ELEM_END_PROP instruction defines properties for the ends of a bar element. Keys for this instruction (except when DEF) are the names of the properties. Keywords, indicating property names, are listed in the following table. Property name CROSS_SECTION_AREA Abbreviation XSA Used for BEAM and ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM PIN_FLAG PIN MOMENT_OF_INERTIA_ABOUT_Z_AXIS MIZ MOMENT_OF_INERTIA_ABOUT_Y_AXIS MIY AREA_PRODUCT_OF_INERTIA API TORSION_STIFFNESS_PARAMETER TSP NONSTRUCT_MASS_PER_UNIT_LENGTH NML Y_COORD_OF_POINT_C YCC Z_COORD_OF_POINT_C ZCC Y_COORD_OF_POINT_D YCD Z_COORD_OF_POINT_D ZCD Y_COORD_OF_POINT_E YCE Z_COORD_OF_POINT_E ZCE 1037 Structural and Thermal Simulation - Help Topic Collection Property name Abbreviation Used for elements Y_COORD_OF_POINT_F YCF ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements ADV_BEAM elements Z_COORD_OF_POINT_F ZCF NONSTR_MASS_MOMENT_PER_UNIT_LEN NMU WARPING_COEFFICIENT WRC Y_COORD_OF_GRAVITY_CENTER YGC Z_COORD_OF_GRAVITY_CENTER ZGC Y_COORD_OF_NEUTRAL_AXIS YNA Z_COORD_OF_NEUTRAL_AXIS ZNA All of the end properties listed above are scalars. ELEM_END_PROP Instruction with the DEF Key This instruction has the following format: %ELEM_END_PROP id DEF: elem_type_id <name> where: id ID of the set of properties. elem_type_id ID of the ELEM_TYPE for which this set is defined. name name of this set of properties (if it is named). 1038 Structural and Thermal Simulation ELEM_END_PROP Instruction with the PROP_NAME This instruction has the following format: %ELEM_END_PROP id PROP_NAME : data where: id is the ID of the set of properties being defined. PROP_NAME is one of the keys listed above. The property name must be valid for a given ELEM_TYPE, referenced in the line DEF. data depends on the PROP_NAME. Typical ELEM_END_PROP Instructions %ELEM_TYPE 3 DEF : BAR BEAM * 2 1 0 ... %ELEM_PROP 2 DEF : 3 %ELEM_PROP 2 REF : 1 5 %ELEM_PROP 2 REF : 1 7 %ELEM_PROP 2 MOMENT_OF_INERTIA : 0. 0. 0. ... %ELEM_END_PROP 5 DEF : 3 %ELEM_END_PROP 5 CROSS_SECTION_AREA : 0.1 ... %ELEM_END_PROP 7 DEF : 3 %ELEM_END_PROP 7 CROSS_SECTION_AREA : 0.21 ... MESH Section The MESH section may contain the following instructions: • • NODE (ND) ELEM (EL) 1039 Structural and Thermal Simulation - Help Topic Collection NODE (ND) Instruction This instruction has the following format: %NODE node_id DEF : placement <cs_id> where: node_id node ID in the model (starting with 1). placement vector of the node coordinates. cs_id ID of the coordinate system used for constraints applied to this point. If skipped, the default coordinate system is used. Typical Node Instructions %NODE 1 DEF : 0.8 -0.88 9. 2 %NODE 2 DEF : 0. 1. 2. ELEM (EL) Instruction This instruction has the following format: %ELEM elem_id DEF : elem_type_id <material_id> <prop_id> placement where: elem_id is the ID of the element in the model (starting with 1). elem_type_id refers to the ELEM_TYPE description. material_id refers to the MATERIAL description (not required for MASS, SPRING, and ADVANCED SPRING elements). prop_id refers to the ELEM_PROP description (may not be defined for some elements). placement describes element placement, depends on the ELEM_TYPE. Element Placement This instruction has the following format: node1_id node2_id ... [cs_id] [offsets] 1040 Structural and Thermal Simulation For SOLID and SHELL elements, placement is a list of node_id's for all element nodes. Corner nodes should be listed first in the order referenced in ELEM_TYPE; then mid-nodesin the order of element edges. The format is as follows: node1_id ... nodeN_id where: N num_nodes for linear elements from the corresponding ELEM_TYPE definition, or (num_nodes + num_edges) for parabolic elements. For MASS and To Ground SPRING elements, placement is defined as follows: node_id <cs_id> where: node_id ID of the element node. cs_id ID of the elemental coordinate system. For MASS elements, cs_id is required only if inertia is defined for the element; that is, Prop_id is defined, and it references a set of properties with the MOMENT_OF_INERTIA line. For SPAR, GAP, SPRING elements, placement is: node1_id node2_id where: node1_id, node2_id IDs of its end nodes. For BEAM, ADV_BEAM elements, placement is defined as follows: node1_id node2_id cs_id <offset1 offset2> where: node1_id, node2_id IDs of its end nodes. cs_id ID of the elemental coordinate system. offset1 vector representing the offset of the first bar end from node1 in the elemental coordinate system. offset2 vector representing the offset of the second bar end from node2 in the elemental coordinate system. The default for offset1 and offset2 is a zero vector. 1041 Structural and Thermal Simulation - Help Topic Collection For ADV_SPRING element, placement is: node1_id node2_id cs_id where: node1_id, node2_id IDs of its end nodes. cs_id ID of the elemental coordinate system. Refer to the following example: %ELEM_TYPE 5 DEF : BAR BEAM * 2 1 0 ... ... %COORD_SYS 3 DEF : * CARTESIAN %COORD_SYS 3 X_VECTOR : 0. 1. 0. %COORD_SYS 3 Y_VECTOR : 1. 0. 0. %COORD_SYS 3 Z_VECTOR : 0. 0. -1. %COORD_SYS 3 ORIGIN : 0.88 -99. -1.5 ... ... %ELEM_PROP 2 DEF : 5 %ELEM_PROP 2 CROSS_SECTION_AREA : 0.01 0.021 %ELEM_PROP 2 MOMENT_OF_INERTIA : 0. 0. 0. ... ... %MATERIAL 1 DEF : ALUM ISOTROPIC %MATERIAL 1 YOUNG_MODULUS : 1.900000E+07 %MATERIAL 1 POISSON_RATIO : 2.100000E-01 ... 1042 Structural and Thermal Simulation ... ... %NODE 7 DEF : 0.88 -99. -1.5 .88 -99. -1.5 %NODE 8 DEF : 0.88 0. -1.5 .88 0. -1.5 %ELEM 10 DEF : 5 1 2 7 8 3 0.1 0. 0. 0. 0. 0. MESH_TOPOLOGY Section The MESH_TOPOLOGY section may contain the following instructions: • • EDGE (EDG) SURFACE(SRF) EDGE (EDG) instruction with the DEF Key This instruction has the following format: %EDGE edge_id DEF: <num_nodes> where: edge_id ID of the edge. num_nodes number of nodes on the edge. EDGE (EDG) instruction with the NODES Key This instruction has the following format: %EDGE edge_id NODES: <corner_node_id> where: corner_node_id list of corner node IDs along the edge. The length of the list is num_nodes. SURFACE (SRF) instruction with the DEF Key This instruction has the following format: %SURFACE surface_id DEF: <num_faces> 1043 Structural and Thermal Simulation - Help Topic Collection where: surface_id ID of the surface. num_faces number of faces lying on the surface. SURFACE (SRF) instruction with the FACES Key This instruction has the following format: %SURFACE surface_id FACES: <elem_id face_id> where: elem_id face_id list of element and face ID pairs. The length of the list is num_faces. LOADS Section The LOADS section may contain the following instructions: • • LOAD_TYPE (LTP) CON_CASE (CC) LOAD_TYPE (LTP) Instruction This instruction has the following format: %LOAD_TYPE id DEF: Name Placement_type Value_type where: Name is the name of the load/constraint. It can be one of the following: • • • • • • • • • • • • • • 1044 PRESSURE (PRE) FORCE (FOR) MOMENT (MOM) DISPLACEMENT (DSP) TEMPERATURE (TEM) ACCELERATION (ACC) ANG_VELOCITY (AVE) CONVECTION (CNV) RADIATION (RAD) HEAT_FLUX (HFL) HEAT_SOURCE (HSR) FREQ_RANGE (FRQ) NUM_MODES (MNU) INIT_GUESS (ING) Structural and Thermal Simulation Placement_type can be one of the following: BODY, ELEM, ELEM_FACE, ELEM_EDGE, NODE. Typical LOAD_TYPE Instructions %LOAD_TYPE 1 DEF : DISPLACEMENT NODE VECTOR_6 MASKABLE %LOAD_TYPE 3 DEF : FORCE NODE VECTOR %LOAD_TYPE 5 DEF : ACCELERATION BODY VECTOR %LOAD_TYPE 7 DEF : TEMPERATURE NODE SCALAR CON_CASE (CC) Instruction This instruction has the following format: %CON_CASE id DEF : name <num_steps> where: name name of the analysis. num_steps number of steps for time-dependent analyses (reserved for future use). The system default is 1. A Typical CON_CASE Instruction %CON_CASE 1 DEF : Case1 Instruction LOAD (LD) This instruction has the following format: %LOAD id DEF : load_type_id con_case_id <step>\ <cs_type> <cs_id> <mask> %LOAD id VAL : <placement> value where: load_type_id refers to LOAD_TYPE. con_case_id refers to CON_CASE containing this load/constraint. If this analysis is time-dependent and the load/constraint is included in one step, specify the case number starting with 1. 1045 Structural and Thermal Simulation - Help Topic Collection cs_type indicates whether the value is defined in the global coordinate system (GCS), local nodal coordinate system (NCS), or local elemental coordinate system (ECS). For SCALAR values, cs_type should be skipped. The default is GCS. cs_id refers to the definition of coordinate system. mask string of 0's or 1's, used to define mask for MASKABLE values (refer to LOAD_TYPE (LTP) Instruction). placement depends on the corresponding LOAD_TYPE. value corresponds to the Value_type, defined in LOAD_TYPE. For MASKABLE loads, it contains only values for components with 1's. Placement If Placement_type in LOAD_TYPE is: • • • • • BODY then placement is absent. ELEM then placement is elem_id. ELEM_FACE then placement is elem_id face_in_el_id. ELEM_EDGE then placement is elem_id edge_in_el_id. NODE then placement is node_id. Refer to the following example: %NODE 5 DEF : 0.88 -99. -1.5 ... %NODE 15 DEF : 11. -11. 0.11 ... %LOAD_TYPE 3 DEF : DISPLACEMENT NODE VECTOR_6 MASKABLE ... %LOAD 1 DEF : 3 1 * GCS * 111000 %LOAD 1 VAL : 5 0. 0. 0. %LOAD 1 VAL : 15 3. 4. 5. ANALYSIS Section The ANALYSIS section may contain the SOLUTION (SLU) instruction. 1046 Structural and Thermal Simulation SOLUTION Instruction with the Key DEF This instruction has the following format: %SOLUTION id DEF : type <sub_type> where: type type of analysis. It can be either STRUCTURAL, THERMAL, or MODAL. sub_type either STATIC (default for the type STRUCTURAL) or STEADY_STATE (default for the type THERMAL). SOLUTION Instruction with the Key CON_CASES This instruction has the following format: %SOLUTION id CON_CASES : con_case_ids where: con_case_ids IDs of analyses (refer to the CON_CASE instructions) to be solved in this run of the solver. Typical SOLUTION Instructions %SOLUTION 1 DEF : STRUCTURAL STATIC %SOLUTION 1 CON_CASES : 1 3 4 7 RESULTS Section The RESULTS section may contain the following instructions: • • RESULT_TYPE (RTP) RESULT (RES) RESULT_TYPE (RTP) Instruction This instruction has the following format: %RESULT_TYPE id DEF : Name Placement_type Value_type 1047 Structural and Thermal Simulation - Help Topic Collection where: Name is the name of the result. It can be one of the following: • • • • • • • • • • DISPLACEMENT (DSP) STRESS (STR) STRAIN (STN) REACTION_FORCE (RF) ERROR_ESTIMATE (ERR) THERMAL_STRAIN (THS) TEMPERATURE (TEM) HEAT_FLUX (HFL) HEAT_GRADIENT (HGR) MODE_FREQUENCY (FRQ) Placement_type one of the following types: • • • • ELEM is the elemental result (currently it may be only ERROR_ESTIMATE). ELEM_NODE is the non-averaged data, defined for every node of an element (for example, STRESS, STRAIN, THERMAL_STRAIN, HEAT_FLUX, HEAT_GRADIENT) NODE is the nodal data (for example, DISPLACEMENT, REACTION_FORCE, TEMPERATURE). BODY is the whole model result (currently it may be only MODE_FREQUENCY). The following table lists Solid Element Result Types. Placement_type NODE Result_type DISPLACEMENT, REACTION_FORCE, STRESS, STRAIN, TEMPERATURE, HEAT_FLUX, HEAT_GRADIENT ERROR_ESTIMATE STRESS, STRAIN, THERMAL_STRAIN, HEAT_FLUX, HEAT_GRADIENT MODE_FREQUENCY ELEM ELEM_NODE BODY The following table lists Shell Element Result Types. Placement_type NODE Result_type DISPLACEMENT, REACTION_FORCE, STRESS, STRAIN, TEMPERATURE, HEAT_FLUX, HEAT_GRADIENT 1048 Structural and Thermal Simulation Placement_type ELEM ELEM_NODE ERROR_ESTIMATE Result_type STRESS, STRAIN, THERMAL_STRAIN, HEAT_FLUX, HEAT_GRADIENT MODE_FREQUENCY ERROR_ESTIMATE (For different values on both sides) STRESS, STRAIN (For different values on both sides) BODY ELEM_FACE FACE_NODE Refer to the following examples: %RESULT_TYPE 1 DEF : DISPLACEMENT NODE VECTOR_6 %RESULT_TYPE 3 DEF : STRESS ELEM_NODE TENSOR %RESULT_TYPE 4 DEF : ERROR_ESTIMATE ELEM SCALAR RESULT (RES) Instruction This instruction has the following format: %RESULT id DEF : result_type_id con_case_id <step/mode> <cs_type> %RESULT id VAL : placement value where: result_type_id refers to RESULT_TYPE. con_case_id refers to the analysis for which the results were obtained. If a analysis has steps, the number of steps must be specified. step/mode is the time step or mode number for dynamic and modal analyses. cs_type indicates whether a value is defined in the global coordinate system (GCS), local nodal coordinate system (NCS), or local elemental coordinate system (ECS). For SCALAR values, it should be skipped. The default is GCS. placement depends on Placement_type, defined in the RESULT_TYPE. value corresponds to Value_type, defined in RESULT_TYPE. 1049 Structural and Thermal Simulation - Help Topic Collection Placement of Results The following table lists possible placements depending on Placement_type given in the RESULT_TYPE instruction. Placement_type ELEM ELEM_FACE ELEM_NODE FACE_NODE NODE BODY elem_id elem_id face_in_el_id elem_id node_in_el_id elem_id face_in_el_id node_in_el_id node_id none Placement %ELEM_TYPE 1 DEF : SHELL TRIANGLE LINEAR 3 3 2 %ELEM_TYPE 1 EDGE : 1 1 2 %ELEM_TYPE 1 EDGE : 2 2 3 %ELEM_TYPE 1 EDGE : 3 3 1 %ELEM_TYPE 1 FACE : 1 1 2 3 %ELEM_TYPE 1 FACE : 2 1 3 2 %RESULT_TYPE 1 DEF : DISPLACEMENT NODE VECTOR_6 %RESULT_TYPE 2 DEF : STRESS FACE_NODE TENSOR\ ECS %RESULT_TYPE 3 DEF : ERROR_ESTIMATE ELEM SCALAR %ELEM 5 DEF : 1 .... # Displacement %RESULT 1 DEF : 1 1 # in node17 %RESULT 1 VAL : 17 1. 2. 3. 0. 0. 0. 1050 Structural and Thermal Simulation # in node 25 %RESULT 1 VAL : 25 11. 22. 33. 0. 0. 0. ... # Stress %RESULT 20 DEF : 2 1 * ECS # in SHELL element #5, face 1 (top), node #1 %RESULT 20 VAL : 5 1 1 0.1 0.2 0.3 0.4 0.5 -0.6 # in SHELL element #5, face 2 (bottom), node #1 %RESULT 20 VAL : 5 2 1 ... # in SHELL element #5, face 2 (bottom), node #3 %RESULT 20 VAL : 5 2 3 ... ... # Error Estimate %RESULT 50 DEF : 3 # on element #5, Face 1 (Top) %RESULT 50 VAL : 5 1 0.5 # on element #5, Face 2 (Bottom) %RESULT 50 VAL : 5 2 0.05 1051 Structural and Thermal Simulation - Help Topic Collection Specialized Information Understanding Fatigue Analysis This document provides background information on fatigue and describes the methodology used in Mechanica fatigue analysis. It covers the following topics: Topic History of Fatigue Physics of Fatigue The E-N Approach • • Strain Cycles Includes the effect of mean residual stresses, hysteresis loop capture and rainflow cycle counting. Factors that Affect Fatigue Life Includes Component Size, Loading Type, Surface Finish, Surface Treatment (that is, Mechanical Treatments, Plating, and Thermal Treatments), and Effect of Surface Treatments on Endurance Limit. The solver technology integrated with Mechanica fatigue analysis is provided by nCode International. Fatigue analysis requires a Fatigue Advisor license from PTC. History of Fatigue The majority of component designs involve parts subjected to fluctuating or cyclic loads. Such loading induces fluctuating or cyclic stresses that often result in failure by fatigue. About 95% of all structural failures occur through a fatigue mechanism. The damage done during the fatigue process is cumulative and generally unrecoverable, due to the following: • • It is nearly impossible to detect any progressive changes in material behavior during the fatigue process, so failures often occur without warning. Periods of rest, with the fatigue stress removed, do not lead to any measurable healing or recovery. It was well-known that wood or metal could be made to break by repeatedly bending it back and forth with a large amplitude. But, it was then discovered that repeated stressing can produce fracture even when the stress amplitude is apparently well within the elastic range of the material. When fatigue failures of railway axles 1052 Structural and Thermal Simulation became a widespread problem in the middle of the nineteenth century, this drew attention to cyclic loading effects. This was the first time that many similar components had been subjected to millions of cycles at stress levels well below the monotonic tensile yield stress. Between 1852 and 1870 the German railway engineer August Wöhler set up and conducted the first systematic fatigue investigation. Some of Wöhler's data are for Krupp axle steel and are plotted, in terms of nominal stress (S) vs. number of cycles to failure (N), on what has become known as the S-N diagram. Each curve on such a diagram is still referred to as a Wöhler line. Note: 1centner = 50 kg, 1 zoll = 1 inch, 1 centner/zoll2 ~ 0.75 MPa At about the same time, other engineers began to concern themselves with problems of failures associated with fluctuating loads in bridges, marine equipment, and power generation machines. During the first part of the twentieth century, more effort was placed on understanding the mechanisms of the fatigue process rather than just observing its results. This activity finally led, in the late fifties and early sixties, to the development of the two approaches, one based on linear elastic fracture mechanics, LEFM, to explain how cracks propagate, and the so-called Coffin-Manson local strain methodology to explain crack initiation. Through this understanding, modern designers and engineers have been able to create more fatigue-resistant components without relying solely on experimentation. From a practical point of view, this has been a much more profitable approach. 1053 Structural and Thermal Simulation - Help Topic Collection Physics of Fatigue Since 1830, it has been recognized that metal under a repetitive or fluctuating load will fail at a stress level lower than required to cause failure under a single application of the same load. The following diagram shows a simple component subjected to a uniform sinusoidally varying force. After a period of time, a crack can be seen to initiate on the circumference of the hole. This crack will then propagate through the component until the remaining intact section is incapable of sustaining the imposed stresses and the component fails. The physical development of a crack is generally divided into 2 separate stages. These relate to the crack initiation phase (Stage I) and the crack growth phase (Stage II). Fatigue cracks initiate through the release of shear strain energy. The following diagram shows how the shear stresses result in local plastic deformation along slip planes. As the loading is cycled sinusoidally, the slip planes move back and forth like a pack of cards, resulting in small extrusions and intrusions on the crystal surface. These surface disturbances are approximately 1 to 10 microns in height and constitute embryonic cracks. 1054 Structural and Thermal Simulation A crack initiates in this way until it reaches the grain boundary. At this point the mechanism is gradually transferred to the adjacent grain When the crack has grown through approximately 3 grains, it is seen to change its direction of propagation. Stage I growth follows the direction of the maximum shear plane, or 45° to the direction of loading. During Stage II the physical mechanism for fatigue changes. The crack is now sufficiently large to form a geometrical stress concentration. A tensile plastic zone is created at the crack tip as shown in the following diagram. After this stage, the crack propagates perpendicular to the direction of the applied load. As the physical mechanism for fatigue is divided into two stages, the methods of analysis are also conventionally divided into two stages. Stage I is typically analyzed using the local strain (or E-N) approach, while Stage II is analyzed using a fracture mechanics based approach. A complete fatigue prediction could therefore use a combination of both methods: Total Life = Life to initiation + Life taken to propagate crack to failure 1055 Structural and Thermal Simulation - Help Topic Collection However, most engineering components spend most of their time at either one stage or the other. In this case, it is normal to conservatively consider only one stage. For example, in most ground vehicle designs, life is typically governed by time to initiation. Components are relatively stiff and the materials fairly brittle. Once the crack has initiated, it takes a relatively short time to propagate to failure. By contrast, many aerospace applications use flexible components made of very ductile materials. In this case, cracks propagate relatively slowly and so the fracture mechanics approaches are usually more appropriate. The physical nature of fatigue was not widely understood during the early days. August Wöhler therefore took a more pragmatic view of fatigue analysis. The method he developed later became known as nominal stress (or S-N) fatigue analysis. This did not differentiate between the Stage I and II growth methods and instead related the nominal stress range to the time taken to complete failure. Though S-N analysis is still widely used in test-based fatigue analysis, it has one major drawback for CAE applications. Fatigue initiation is driven by local plastic strains, but S-N analysis uses elastic stress as the input. Therefore, S-N analysis is unsuitable for performing CAE analysis on components containing local areas of plasticity. For this reason local strain (or E-N) methods are more universally suitable. Mechanica fatigue analysis uses the E-N method. The E-N Approach In a fatigue test, hourglass-shaped specimens of different material types are subjected to various types of cyclic loading, such as: small-scale bending, torsion, tension, and compression. The E-N approach uses these tests to measure fatigue life. The results are plotted in terms of strain (E) vs. cycles to failure (N) on an E-N diagram. A typical E-N diagram is illustrated below for a low alloy steel and an aluminum alloy. 1056 Structural and Thermal Simulation Mechanica uses a generic set of fatigue properties to model low alloy steels, unalloyed steels, aluminum alloys, and titanium alloys. These generic properties have been compiled by Baumel Jr. and Seeger and are known as the Uniform Material Law. While they cannot be expected to give accurate fatigue lives for practical purposes, they are ideal for determining whether a component is likely to suffer from fatigue problems, and whether a more detailed analysis is needed before commissioning. For more information on the Uniform Material Law, see Materials Science Monographs, 61, "Materials Data for Cyclic Loading, Supplement 1." The following discussion covers two aspects of fatigue theory that are critical to an understanding of the how Fatigue Advisor measures fatigue: Topic Strain Cycles Factors That Affect Fatigue Life Strain Cycles Before looking in more detail at the E-N procedure, it helps to understand the three different types of cyclic strains that contribute to the fatigue process. The following diagrams and descriptions explain each separate type. The first figure illustrates a fully-reversed strain cycle with a sinusoidal form. This is an idealized loading condition typically found in rotating shafts operating at constant speed without overloads. This is also the type of strain cycle used for most fatigue tests. For this kind of cycle, the maximum ( max) and minimum ( min) strains are of equal magnitude but opposite sign. Usually tensile strain is considered to be positive and compressive strain negative. The strain range, r, is the algebraic difference between the maximum and minimum strains in a cycle. r = max – min a, The strain amplitude, a is one half the strain range. – min) = r /2=( max /2 1057 Structural and Thermal Simulation - Help Topic Collection The second figure illustrates the more general situation where the maximum and minimum strains are not equal. In this case, they are both tensile and define a mean offset, m = ( max + min) / 2, for the cyclic loading. As mentioned above, most basic fatigue data are collected using fully-reversed loads. Therefore, these data are not directly applicable for strain cycles with a non-zero mean ( m 0). In order to predict more realistic life estimates for strain cycles with tensile or compressive mean stress, results of the tests conducted using fullyreversed loads are corrected. The choice of corrective approach to use depends on whether the mean stress is primarily tensile or compressive. The reason for this can be seen in the following plot which schematically illustrates the effect of mean stress on the strain-life (E-N) curve. Viewed conceptually, tensile mean stress acts to pull open a crack while compressive mean stress works to keep it closed. Typically the effects are concentrated at the long life end of the diagram, with tensile mean stress reducing life and compressive mean stress extending it. 1058 Structural and Thermal Simulation Since the tests required to calculate E-N curves for a range of mean stresses are quite expensive, several empirical relationships have been developed to model the effect of mean stress. Of all the proposed methods, two have been most widely accepted: • • The Smith, Watson, Topper Approach The Morrow Correction For loading sequences which are predominantly tensile in nature, the Smith, Watson, Topper approach is more conservative and is therefore recommended. In the case where the loading is predominantly compressive, particularly for wholly compressive cycles, the Morrow correction can be used to provide more realistic life estimates. Mechanica uses both methods and the most appropriate method is automatically chosen. For more information on the Smith, Watson, Topper approach, see "A Stress-Strain Function for the Fatigue of Metals", Journal of Materials, Vol. 5, No. 4, 1970. For more information on the Morrow correction, see "Fatigue Design Handbook", Advances in Engineering, Vol. 4, Society of Automotive Engineers, 1968. The next figure illustrates a more complex, variable amplitude loading pattern that is closer to the cyclic strains found in real structures. 1059 Structural and Thermal Simulation - Help Topic Collection For variable amplitude loading it is necessary to extract the fatigue damaging cycles from the signal and then evaluate the damage carried out by each cycle. The total damage is the sum of the damage caused by each individual cycle. Each fatigue cycle is extracted by a process known as hysteresis loop capture. The loci of the stress and strain are plotted as shown in the following diagram. When a stress-strain hysteresis loop is closed, then the strain range and mean stress are returned and the damage calculated using the E-N curve modified for mean stress correction. This analysis is carried out over the whole strain time signal until all the cycles have been extracted and the total damage evaluated. A very efficient algorithm has been developed to perform cycle extraction known as: Rainflow Cycle Counting. This is the algorithm that Mechanica uses. Mechanica normally uses a linear elastic solution to determine the pseudo-elastic strains in a component. In other words, the solution ignores plasticity. Before proceeding with the fatigue analysis, these strains are automatically converted into non-linear elastic-plastic strains using Neuber's relationship. Factors that Affect Fatigue Life As mentioned above, the E-N curve is derived from strain control tests based on hourglass-shaped specimens. A standardized, fully reversed fatigue test is used to determine a base-line E-N relationship for a polished specimen, approximately 6 mm in diameter. While the fatigue or endurance limit measured in this test is denoted by 'e, a component in service has lower limit, e, that reflects modifications to a specimen outside of the laboratory. For steels in particular, several empirical relationships account for the variation in e as a result of the following: • 1060 Component size, Csize Structural and Thermal Simulation • • • • The The The The type of loading, Cload effect of notches, Cnotch effect of surface finish, Csur < 1 (promotes crack growth) effect of surface treatment, Csur >1 (inhibits crack growth) To account for these effects, specific modifying factors are typically applied to the test result so that: e = 'eCnotchCsizeCloadCsur . . . where reciprocal of the product, CnotchCsizeCloadCsur , is collectively known as the fatigue strength reduction factor Kf: Kf = 1 / (CnotchCsizeCloadCsur . . .) It is very important to remember that all the modification factors are empirical, conservative and generally only applicable to steel. They provide little or no fundamental insight into the fatigue process itself other than providing approximate trends. In particular they should not be used in areas outside their measured applicability. Read the following to learn more about the factors that influence fatigue life: Topic The Influence of Component Size The Influence of Loading Type The Influence of Surface Finish The Qualitative Influence of Surface Treatment The Quantitative Effect of Surface Treatments on the Endurance Limit The Influence of Component Size Fatigue in metals results from the nucleation and subsequent growth of crack-like flaws under the influence of an alternating stress field. The theory is that failure starts at the weakest link, the most favorably orientated metal crystal for example, and then grows through less favorably orientated grains until final failure. Intuitively, it would seem reasonable to suppose that the larger the volume of material subjected to the alternating stress, the higher the probability of finding the weakest link sooner. Actual test data do confirm the presence of a size effect particularly in the case of bending and torsion. The stress gradient built up through the section, in bending and to a lesser extent in torsion, concentrates more than 95% of the maximum surface stress in a thin layer of surface material. In large sections, this stress gradient is less steep than in smaller sections. So the volume of material available that could contain a critical flaw 1061 Structural and Thermal Simulation - Help Topic Collection will be greater, leading to a reduced fatigue strength. The effect is small for axial tension where the stress gradient is absent. The value for Csize is estimated from one of the following. If the diameter of the test specimen shaft is d < 6 mm: Csize = 1 If the diameter of the test specimen shaft is 6 mm < d < 250 mm Csize = 1.189d-0.097 The effect of size is particularly important for the analysis of rotating shafts such as might be found in vehicle powertrains. For situations where components do not have a round cross section, the following equation calculates an equivalent diameter, deq, for a rectangular section under bending with width (w) and thickness (t): deq2 = 0.65wt The Influence of Loading Type Fatigue data measured using one type of cyclic loading, axial tension for example, may be "corrected" to represent the data that would have been obtained had the test been performed using some other loading methodology such as torsion or bending. The standardized rotating bend test calls for tests to be carried out under conditions of fully reversed bending. In moving from one loading condition to another, the values of Cload to be used with the endurance limit, e are detailed below: Measured Loading Axial Axial Bending Bending Torsion Torsion to to to to to to Target Loading Bending Torsion Torsion Axial Axial Bending C load 1.25 0.725 0.58 0.8 1.38 1.72 Thus, using the values from this table, if an axial tension load produces a strain of e, the strain produced under a bending load would be 1.25 e. 1062 Structural and Thermal Simulation In addition to influencing the endurance limit, loading conditions can also influence the Basquin slope, b, which is used when plotting the E-N curve on log-log scale. This effect is usually taken into account by modification of the strain at 103 cycles, 3, as well as e. The following factors are used to define C'load, the 3 modification factor: Measured Loading Axial Bending Torsion Torsion to to to to Target Loading Torsion Torsion Axial Bending C' load 0.82 0.82 1.22 1.22 The Influence of Surface Finish A very high proportion of all fatigue failures nucleate at the surface of components so that surface conditions become an extremely important factor influencing fatigue strength. Various surface conditions are usually judged against the polished laboratory specimen standard. Normally, scratches, pits, machining marks, and so forth, influence fatigue strength by providing additional stress raisers that aid the process of crack nucleation. The diagram below shows that high strength steels are more adversely affected by a rough surface finish than softer steels. For this reason, the surface finish correction factor, Csur < 1, is strongly related to tensile strength. Here the surface finish correction factor categorizes finish in qualitative terms such as polished, machined, and forged. 1063 Structural and Thermal Simulation - Help Topic Collection Note that some of the curves presented in this figure include effects other than just surface finish. For example, the forged and hot rolled curves include the effect of decarburization. Other diagrams present the surface finish correction factor in a more quantitative way by using a quantitative measure of surface roughness such as RA (the root mean square) or AA (the arithmetic average). The following diagram shows the effect of surface roughness on the surface finish correction factor. 1064 Structural and Thermal Simulation Values of surface roughness associated with each of the manufacturing processes are readily available in handbooks, as in the example below: Type of Finish (Microns) Lathe-formed Partly hand polished Hand Polished Ground Superfinished Ground and polished Surface Roughness 2.67 0.15 0.13 0.18 0.18 0.05 The Qualitative Influence of Surface Treatment As in the case of surface finish, surface treatment can greatly influence fatigue strength, particularly the endurance limit. The net effect of the treatment is to alter the state of residual stress at the free surface. 1065 Structural and Thermal Simulation - Help Topic Collection Residual stresses arise when plastic deformation is not uniformly distributed throughout the entire cross section of the component being deformed. In the preceding figures, a metal bar has a surface that is being deformed in tension by bending. • • • At time T=1, bending moment M1 is being applied and is in the elastic range. At time T=2, the bending moment has increased to M2, the yield stress (Sy) has been reached, and the surface undergoes plastic deformation. When the external force is removed, the regions that were plastically deformed prevent the adjacent elastic regions from complete elastic recovery to the unstrained condition. In this way, the elastically deformed regions are 1066 Structural and Thermal Simulation left in residual tension, and the plastically deformed regions are in a state of residual compression. The result is the stress distribution at time T=3. For many purposes, residual stress can be considered identical to the stresses produced by an external force. Thus, the presence of a compressive residual stress at the surface of a component will effectively decrease the probability of fatigue failure. The preceding figure illustrates the superposition of applied and residual stresses. • • The top schematic shows an elastic stress distribution in a beam under bending moment M with no residual stress. In the center schematic, a typical residual stress distribution associated with a mechanical surface treatment such as shot peening is detailed. Note that the 1067 Structural and Thermal Simulation - Help Topic Collection • compressive stress at the surface is compensated by an equivalent tensile stress over the interior of the cross section. In the bottom schematic, the distribution due to the algebraic summation of the applied stress (caused by bending moment M) and residual stress is shown. Note that the maximum tensile stress at the surface has been reduced by the amount of the residual stress. Also, the peak tensile stress has now been moved to the interior of the beam. The magnitude of this stress will depend on the gradient of the applied stress and the residual stress distribution. Under these conditions, subsurface crack initiation becomes a possibility. Surface treatments are divided broadly into mechanical, thermal, and plating processes. The first two processes provide a compressive layer. The plating process provides a tensile residual stress. Following is detailed description of each process: • Mechanical Treatments — The main commercial methods for introducing residual compressive stresses are cold rolling and shot peening. Although some alteration in the strength of the material occurs as a result of work hardening, the improvement in fatigue strength is due mainly to the compressive surface stress. Surface rolling is particularly suited to large parts and is frequently used in critical components such as crankshafts and the bearing surface of railway axles. Bolts with rolled threads typically possess twice the fatigue strength of conventionally machined threads. Shot peening, which consists of firing fine steel or cast iron shot against the surface of a component, is particularly well suited to processing small mass produced parts. It is important to remember that cold rolling and shot peening have their greatest effect at long lives. At short lives they have little or no effect. As with other modifying factors, correction factors can be used to account for the effect of these mechanically induced compressive stresses by adjusting the endurance limit e. Typically the factor associated with peening is about 1.5 to 2.0. • Thermal Treatments — Thermal treatments are processes that rely on the diffusion of either carbon (carburizing) or nitrogen (nitriding) onto and into the surface of a steel component. Both types of atoms are interstitial, that is they occupy the spaces between adjacent iron atoms, thereby increasing the strength of the steel and causing a compressive residual stress to be left on the surface through volumetric changes. Carburizing is typically a three-step process: o o o packing the steel components within boxes which contain carbonaceous solids sealing to exclude the atmosphere heating to about 900 degrees Celsius for a period of time that depends on the depth of the case required 1068 Structural and Thermal Simulation Alternatively components may be heated in a furnace in the presence of a hot carburizing gas such as natural gas. This process has the advantage that it is quicker and more accurate. In addition, the carburizing cycle may be followed up by a diffusion cycle with no carburizing agent present. This allows some of the carbon atoms to diffuse further into the component and thus reduces gradients. The nitriding process is very similar in nature to gas carburizing except that ammonia gas is used and the components are soaked at lower temperatures. Typically 48 hours at about 550 degrees Celsius will provide a nitrided case depth of about 0.5 mm. Nitriding is particularly suited to the treatment of finished notched components such as gears and slotted shafts. The effectiveness of the process is illustrated in the following table: Endurance Limit (MPa) Geometry Not Nitrided 310 175 175 Nitrided Un-notched Semicircular notch V notch • 620 600 550 Plating — Chrome and nickel plating of steel components can decrease the endurance limit by more than half, due to the creation of tensile residual stresses at the surface. These tensile stresses are a direct result of the plating process itself. As in the case of mechanically induced surface stresses, the effect of plating is most pronounced at the long life end of the spectrum and also with higher strength materials. Introducing a compressive residual stress prior to the plating process such as shot peening or nitriding can reduce the harmful effects of plating. Annealing components after plating, thereby relieving the tensions, is an alternative approach. 1069 Structural and Thermal Simulation - Help Topic Collection The Quantitative Effect of Surface Treatments on the Endurance Limit (Steels) The effect of surface treatment depends on the surface finish. The increase in endurance limit stress due to the surface treatment is given in the following table: Increase in Endurance Limit Finish Polished Ground Machined Hot Rolled Cast Forged Shot Peened +15% +20% +30% +40% +40% +100% Cold Rolled +50% +0% +70% +0% +0% +0% Nitrided +100% +100% +100% +100% +100% +100% Whatever correction was made by the surface finish, applying a surface treatment will have a subsequent effect based on the preceding table. For example, if machining reduces the endurance limit by 30%, then from the table it can be seen that cold rolling will recover the loss by increasing the limit 70%. 1070 Structural and Thermal Simulation Shell Property Equations This document provides a very brief description of how the mechanical properties of shells are represented mathematically in Mechanica. This document also defines the terminology used to describe shell properties and shell results within Mechanica. This document is divided into the following sections: Topic Overview Formulae for Calculating Shell Properties List of Symbols Bibliography Overview The formulae given in this document express the fundamental relationships between shell forces, moments, strains, curvature changes, and shell properties and results. These formulae are provided to unambiguously define the conventions used to describe the various modeling and results data for shells. You specify properties that define the mechanical behavior of laminate shells on the laminate stiffness version of the Shell Property Definition dialog box. See About Shell Properties for more information. At the point for which you want to see results, you define the following properties relative to the material orientation: • • • • • • • • shell extensional stiffnesses shell transverse shear stiffnesses shell extensional-bending coupling stiffnesses shell bending stiffnesses shell resultant thermal moment coefficients shell resultant thermal force coefficient mass per unit area rotary inertia per unit area You can review the following results quantities with respect to the material orientation at the point of interest or with respect to a coordinate system. See Relative Results for more information. • • rotation of shell midsurface about the X and Y axes midsurface strain 1071 Structural and Thermal Simulation - Help Topic Collection • • • • • • curvature change of the shell midsurface shell resultant moment shell resultant force shell transverse shear force stress displacement of the shell midsurface See the List of Symbols for the symbols that represent these terms. These formulae and their descriptions are not meant to be a tutorial for the analysis of shells. More detailed information concerning the modeling of laminated or orthotropic shells may be found in the texts by Jones (1), Reddy (2), Tsai (3), Ugural (4) and others. The Bibliography describes these texts. The figures and equations presented in this section are given for flat shells, or plates. The engineering concepts presented here generalize to curved shells, but the mathematical descriptions of curved shells are more complicated and will not be given. Formulae for Calculating Shell Properties A shell is a section of your Mechanica model that is thin in comparison to its width and length. It is computationally efficient to model the thin regions of your structure with shells. This efficiency results, in part, from a basic assumption concerning the behavior of shells. That is, that the mechanical behavior of a shell can be approximated by describing the mechanical behavior of the midsurface of the shell. Thus, the displacement of a shell can be described by the displacement and rotation of its midsurface, the straining of a shell can be described by the straining and curvature changes of its midsurface, and the equilibrium of a shell can be described by the equilibrium of stresses integrated through the thickness of the shell. The figure below shows a flat rectangular shell, the edges of which are aligned with the X and Y axes of a Cartesian coordinate system. The XY plane of this coordinate system is halfway between the top and bottom surfaces of the shell; that is, the midsurface of the shell is at z=0. The shell has thickness t, so that the top surface is at z = t/2 and the bottom surfaces is at z = –t/2, as the following figure illustrates: 1072 Structural and Thermal Simulation As mentioned above, it is assumed that the displacement of any point (x, y, z) in the shell can be expressed in terms of the displacement and rotation of the point (x, y, 0) on the midsurface of the shell. Specifically, it is assumed that: where: • • • are the components of displacement in the x, y, and z directions, respectively are the components of displacement of the midsurface are the (small) rotations of the midsurface about the x and y axes, respectively and of any point (x,y,z) can be expressed ) and curvature Similarly, the strain components in terms of the midsurface (or membrane) strains ( changes ( ) as: Note that Equation (A.2) contains the tensor shear strain components, and , and not the engineering shear strain components, which are twice the values of the tensor shear strain components. For flat shells, the tensor shear strain components are: and 1073 Structural and Thermal Simulation - Help Topic Collection The shell resultant forces ( ), the shell resultant moments ( ), ) are obtained by integrating the stress and the shell transverse shear forces ( through the thickness of the shell. The shell components resultant forces are given by: The shell resultant moments are given by: The shell transverse shear forces are given by: The following figure illustrates the sign conventions employed for the resultant forces and moments, and transverse shear forces. Note that a positive moment, , induces positive strain, , in the top half of the shell (z > 0) and negative strain in the bottom half of the shell (z < 0). 1074 Structural and Thermal Simulation 1075 Structural and Thermal Simulation - Help Topic Collection The relationship between the shell resultants, and the midsurface strains and curvature changes are given by: and: (where i,j = 1, 2, 6) are called the shell In equation (A.6), the quantities are called the bending stiffnesses, the extensional stiffnesses, the quantities are called the extensional-bending coupling stiffnesses, and the quantities quantities (where k,l = 4,5) are called the transverse shear stiffnesses. The quantities quantities and and are the transverse shear strains on the midsurface. The are the resultant thermal forces and moments respectively. The shell stiffness and thermal resultants introduced in Equations (A.6) and (A.7) are defined by integrating the material properties of the shell through the thickness of the shell. The extensional, bending, and extensional-bending stiffnesses are given by: and: 1076 Structural and Thermal Simulation and: where are the reduced stiffnesses of the material. The transverse shear stiffness is given by: where: • • are (non-reduced) stiffnesses of the material, and are the shear correction coefficients, which for a homogeneous shell are often taken to be . Note that if the material of the shell is distributed symmetrically about the midsurface, then the integral in Equation (A.9) vanishes and the extensional-bending coupling stiffnesses are identically zero. The resultant thermal forces and moments are given by: and: where: • • are the coefficients of thermal expansion of the material, and is the change in temperature from the stress-free state. 1077 Structural and Thermal Simulation - Help Topic Collection If the change in temperature is uniform through the thickness of the shell, then the in Equations (A.12) and (A.13) may be removed from the integral, resulting in Equations (A.14) and (A.15): where coefficients, which are given by: are called the shell resultant thermal The mass properties for shells are also obtained by integrating the material property data through the thickness of the shell. The mass per unit area, , is given by: where is the density of the material. , is given by: The rotary inertia per unit area, 1078 Structural and Thermal Simulation List of Symbols The following table defines the symbols used in this document: Symbol Definition coefficients of thermal expansion (i,j = 1,2,6) (k,l = 4,5) (i,j = 1,2,6) shell extensional stiffness shell transverse shear stiffness shell extensional-bending coupling stiffness rotation of shell midsurface about the X and Y axes (k,l = 4,5) (i,j = 1,2,6) material stiffness shell bending stiffness temperature change strain midsurface (or membrane) strain curvature change of the shell midsurface (k,l = 4,5) shell resultant moment shell resultant thermal moment shell resultant thermal moment coefficient shell resultant force shell resultant thermal force shell resultant thermal force coefficient shear correction coefficients 1079 Structural and Thermal Simulation - Help Topic Collection Symbol Definition shell transverse shear force (i,j = 1,2,6) material reduced stiffness mass per unit area rotary inertia per unit area stress t shell thickness displacement displacement of the shell midsurface x, y z midsurface coordinates coordinate perpendicular to the shell midsurface Bibliography 1. Jones, Robert M. Mechanics of Composite Materials. Washington, DC: Scripta Book Company, 1975. 2. Reddy, J.N. Energy and Variational Method in Applied Mechanics. New York: John Wiley & Sons, 1984. 3. Tsai, S. W. and H. T. Hahn Introduction to Composite Materials. Westport, CT: Technomic Publishing Co., 1980. 4. Ugural, A. C. Stresses in Plates and Shells. New York: McGraw-Hill Book Company, 1981. 1080 Structural and Thermal Simulation Verification Guide Verification Overview Mechanica is a family of design analysis products. The main products are Structure and Thermal. Several optional modules are tightly integrated with these main products. Mechanica documentation is written for mechanical engineers. It assumes a working knowledge of mechanical engineering theory, terminology, and practice. However, you do not need any specialized knowledge of design analysis to use Mechanica software or its documentation. Read the following topics for information on using this book, Verification Guide, and for an overview of the documentation available for the current release of Mechanica. This preface covers: Topic Using This Guide References Using This Guide The Verification Guide uses a series of problems, based on finite element models and mechanism analysis models for which analytic solutions are known, to demonstrate the accuracy and efficiency of Mechanica in the design analysis process. Mechanica's results are compared to those obtained using traditional analysis codes such as ANSYS, NASTRAN, and NAFEMS, or to theory. A number of problems are drawn from the well-known MacNeal-Harder finite element problem set. The models used in this guide are located on the Mechanica CD-ROM. You can use the models to rerun the studies on your platform. See msengine for information on running the studies. There is a separate section in this guide for models verified by each of the Mechanica analysis types: Structure, Thermal, Vibration, Buckling, and Nonlinear. There is also a section for Structure optimization models. 1081 Structural and Thermal Simulation - Help Topic Collection Organization Here are the topics covered in this guide: Structure Models Static Analysis Describes several static analysis problems and compares results. Modal Analysis Describes several modal analysis problems and compares results. Thermal Models Steady State Thermal Analysis Describes steady state thermal analysis problems and compares results. Transient Thermal Analysis Describes transient thermal analysis problems and compares results. Vibration Models Dynamic Time Response Analysis Describes a dynamic time response analysis problem and compares results. Dynamic Frequency Response Analysis Describes a dynamic frequency response analysis and compares results. Dynamic Shock Response Analysis Describes a dynamic shock response analysis problem and compares results. Buckling Models Buckling Analysis Describes a buckling analysis problem and compares results. 1082 Structural and Thermal Simulation Nonlinear Models 2D and 3D Contact Models Describes 2D and 3D contact problems and compares results. Prestress Modal Analysis Describes a prestress modal analysis problem and compares results. Describes a large deformation analysis problem and compares results. Large Deformation Analysis Optimization Models Optimization Analysis Describes an optimized static structural model. The results in this guide are from the current release of Mechanica running on the Sun workstation. If you are running these programs on a different platform, your results and what you see on the screen may differ slightly from the results and graphics in this document. We have not discovered any significant differences in any results on the different platforms that we support. Identification System The verification problems are identified by their study name. For example, mvsm003 indicates that this is the third Structure modal analysis problem in the Verification Guide. The study names are determined by the following convention: • First two alphabetic characters: mv — Mechanica Verification • Third alphabetic character: s — Structure t — Thermal o — Optimization 1083 Structural and Thermal Simulation - Help Topic Collection • Fourth alphabetic character: o Structure m — Modal s — Static l — Laminate t — Dynamic Time Response f — Dynamic Frequency Response k — Dynamic Shock Response b — Buckling c — Contact d — Large Deformation p — Prestress o Thermal s — Steady-State t — Transient o Optimization o — Optimization o Three digit numeral: 001 — Sequential problem number Use these design study names if you want to run a study or review results. 1084 Structural and Thermal Simulation Results Conventions This section describes the conventions used in the results table included for each problem. Following is an example of a results table: Theory MSC/ NASTRAN Structure % Difference Radial Deflection @ Load (m=disp_x_radial) 2.8769e– 3 2.8715e–3 2.8725e– 3 0.18% Convergence %: 0.5% on Local Disp and SE Max P: 7 No. Equations: 33 Refer to the following information for an explanation of each column in the results table: • • • • • Column 1 — Displays the results quantity of interest. Column 2 — Displays the theoretical results, which are taken from the "Reference" listed on the first page of each model summary. Column 3 (optional) — Displays results from other programs, in this case NASTRAN. Column 4 — Displays Mechanica results. Column 5 — Displays the percentage difference between the Mechanica results and the theoretical answer. Beneath the results quantity name, in parentheses, is additional information you can use to view the results on your system. In this area, you will find one or more pieces of information (xxxx is the name of the measure, analysis, or load; x is the mode number): • • • • measure name, denoted by (m=xxxx) analysis name, denoted by (a=xxxx) load name, denoted by (l=xxxx) mode number (for modal analysis), denoted by (mode=x) When multiple analyses, loads, or measures exist in a study, the analysis name and load name, measure name, or mode number are listed. 1085 Structural and Thermal Simulation - Help Topic Collection You can use this information in two ways. You can view or print out the study.rpt file in a shell, or you can view the information in the summary file for the design study. To display the summary file, open the model with the same name as the study, select Run from the Main menu, then select Status. Next, select Summary from the Design Study Status dialog box and find the measure name. For verification problems, the bottom line of the table displays the convergence percentage and the type of convergence, the maximum p-level order reached at convergence, and the number of equations required for convergence. For Structure models, the convergence option Local Edge Disp & Local Strain Energy is abbreviated as Local Disp and SE in this guide. For Thermal models, the convergence option Local Temp and Energy Norm is abbreviated Local Temp and EN. Installation Instructions The verification models are on the Pro/ENGINEER CD-ROM you received. The models are in the ms_verf.23 directory. You install the Mechanica verification models with your Mechanica installation. References Following is a list of references used in this guide: • • • • • • • • • • • • • Barlow, J., and Davies, G.A.O. Selected FE Benchmarks in Structural and Thermal Analysis. UK: NAFEMS, Revision 2, October, 1987. Chahjes, A. Principles of Structural Stability Theory. Prentice-Hall, 1974. Cameron, A.D., Casy, J.A., and Simpson, G.B. Benchmark Tests for Thermal Analysis (Summary). UK: NAFEMS, August, 1986. Imai, Kanji. Configuration Optimization of Trusses by the Multiplier Method. LA: University of California, UCLA-ENG-7842. Kane, T.R., and Levinson, D.A. Dynamics: Theory and Application. NY: McGraw-Hill, 1985. Kreith, F. Principles of Heat Transfer. 2nd ed. PA: International Textbook Co., 1959. Love, A.E.H. A Treatise on the Mathematical Theory of Elasticity. 4th ed. NY: Dover Publications, 1944. MacNeal, R.H., and Harder, R.L. "A Proposed Standard Set of Problems to Test Finite Element Accuracy." Finite Elements in Analysis and Design I. Elsevier Science Publishers, 1985. MacNeal-Schwendler Corporation. MSC/NASTRAN Verification Problem Manual. MSC/NASTRAN Version 64, January, 1986. Meriam, J.L. Engineering Mechanics, Vol. 2: Dynamics. NY: John Wiley and Sons, Inc. 1978. Noor, A.K., and Mathers, M.D., "Shear-Flexible Finite-Element Models of Laminated Composite Plates and Shells." NASA TN D-8044. Langley Research Center, Hampton, VA. December, 1975. Roark, R. J., and Young, W. Formulas for Stress and Strain. 5th ed. NY: McGraw-Hill, 1982. Schneider, P. J. Conduction Heat Transfer. 2nd ed. MA: Addison-Wesley Publishing Co., Inc., 1957. 1086 Structural and Thermal Simulation • • • • • Shigley, J.E., and Uicker, J.J. Theory of Machines and Mechanisms. NY: McGraw-Hill. 1980. Swanson Analysis Systems, Incorporated. ANSYS Verification Manual. Thomson, W.T. Theory of Vibration with Applications. NJ: Prentice-Hall, Inc. 2nd printing, 1981. Timoshenko, S. Strength of Materials, Part II, Advanced Theory and Problems. 3rd ed. NY: D. Van Nostrand Co., Inc. 1956. Timoshenko, S., and Young, D.H. Vibration Problems in Engineering. 3rd ed. NY: D. Van Nostrand Co., Inc. 1955. Additional references pertaining to specific problems are listed where applicable. 1087 Structural and Thermal Simulation - Help Topic Collection Static Analysis Problems This chapter contains static analysis problems and Structure's results. In a Static analysis, Structure calculates deformations, stresses, and strains on your model in response to specified loads and subject to specified constraints. Structure also automatically calculates all predefined measures. This list of measures differs based on the analysis type. This chapter contains the following models: Topic mvss001: 2D Axisymmetric Cylindrical Shell mvss002: 2D Axisymmetric Flat Circular Plate mvss003: 2D Plane Stress Cantilever Plate mvss004: 2D Plane Strain Thick-Walled Cylinder mvss005: 2D Axisymmetric Thick-Walled Cylinder mvss006: 3D Cantilever Beam mvss007: 3D Beam with Multiple Constraints mvss008: 3D Beam with Parallelogram-Shaped Shell Elements mvss009: 3D Beam with Trapezoidal-Shaped Shell Elements mvss010: 3D Curved Beam Modeled with Shells mvss011: 3D Simply Supported Rectangular Plate mvss012: 3D Clamped Rectangular Plate mvss013: 3D Hemispherical Shell mvss014: 3D Cantilever Beam Twisted by 90 mvss015: 3D Scordelis-Lo Roof mvss016: 2D Axisymmetric Cylinder/Sphere mvss017: 2D Tapered Membrane with Gravity Load mvss018: 3D Z-Section Cantilevered Plate mvss019: 3D Cylindrical Shell with Edge Moment mvss020: Beam Sections mvss021:Thick-Walled Cylinder Under Internal Pressure mvss022: Thin-Walled Spherical Vessel Under Its Own Weight mvsl001: Static Analysis of Composite Lay-up mvss001: 2D Axisymmetric Cylindrical Shell Analysis Type: Model Type: Comparison: Static 2D Axisymmetric NASTRAN No. V2411 1088 Structural and Thermal Simulation Reference: • • P.E. Grafton and D.R. Strome, "Analysis of Axisymmetrical Shells by the Direct Stiffness Method," AIAA Journal, 1(10): 2342-2347. J.W. Jones and H.H. Fong, "Evaluation of NASTRAN," Structural Mechanics Software Series, Vol. IV (N. Perrone and W. Pilkey, eds.), 1982. Description: Find the radial deflection at the loaded end of a cantilever cylinder that is modeled axisymmetrically. Note: Element B is optional, but has been included here to increase the accuracy of results in the area local to the loaded end and to reduce computation time. Specifications Element Type: Units: Dimensions: 2D shell (2) IPS length: 6 radius: 5 thickness: 0.01 1089 Structural and Thermal Simulation - Help Topic Collection Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 1e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraint: placed on point A: fixed in all DOF Load: placed on point C: FX = 1 Distribution: N/A Spatial Variation: N/A Comparison of Results Data Theory Radial Deflection @ Load (a=disp_x_radial) 2.8769e– 3 MSC/ NASTRAN 2.8715e–3 Structure 2.8725e– 3 % Difference 0.15% Convergence %: 0.5% on Local Disp and SE Max P: 7 No. Equations: 33 mvss002: 2D Axisymmetric Flat Circular Plate Analysis Type: Model Type: Comparison: Static 2D Axisymmetric ANSYS No. 15 1090 Structural and Thermal Simulation Reference: Timoshenko, S. Strength of Materials, Part II, Advanced Theory and Problems. 3rd ed. NY: D. Van Nostrand Co., Inc. 1956, pp. 96, 97, and 103. A flat circular plate, modeled axisymmetrically, is subjected to various edge constraints and surface loadings. Determine the maximum stress for each case. Description: Specifications Element Type: 2D shell (1) Units: IPS Dimensions: radius: 40 thickness: 1 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Poisson's Ratio: 0.3 Thermal Expansion: 0 1091 Structural and Thermal Simulation - Help Topic Collection Young's Modulus: 3e7 Conductivity: 0 Constraints: clamped Location placed on point B: Degrees of Freedom fixed in all DOF simple placed on point B: fixed in TransX and TransY Loads: clamped Location/Magnitude: placed on edge A-B: FY = –6 Distribution: per unit area Spatial Variation: uniform simple placed on edge A-B: FY = –1.5 per unit area uniform Comparison of Results Data Theory Maximum Stress (m=max_prin_mag, a=clamped) 7200 ANSYS 7152 Structure 7200 % Difference 0.0% Convergence %: 0.0% on Local Disp and SE Max P: 5 No. Equations: 15 Maximum Stress (m=max_prin_mag, –2970 –2989 29701 0.0% 1092 Structural and Thermal Simulation a=simple) Convergence %: 0.0% on Local Disp and SE Max P: 5 No. Equations: 16 1 Sign of result is dependent upon direction of load. mvss003: 2D Plane Stress Cantilever Plate Analysis Type: Model Type: Comparison: Reference: Static 2D Plane Stress NASTRAN No. V2408A Singer, Ferdinand L. Strength of Materials. Harper & Row, 1962, Art. 52, p. 133. Find the bending stress at the fixed end for a cantilever plate subjected to an in-plane shear load. Description: 1093 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: Units: 2D plate (1) IPS Dimensions: length: 3 height: 0.6 thickness: 0.1 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 1.07e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on edge A-B: fixed in TransX, TransY Loads: placed on edge C-D: FY load per unit length = –200 Distribution: per unit length Spatial Variation: uniform The theoretical results are based on elementary beam theory. Structure models the actual physical structure, capturing the singular stresses present at the constrained corners. Setting Poisson's ratio equal to zero reduces the model to its elementary form. 1094 Structural and Thermal Simulation Comparison of Results Data Theory Bending Stress @ Node A (m=max_stress_xx) 6.0e4 MSC/ NASTRAN 5.5190e4 Structure 6.0121e4 % Difference 0.20% Convergence %: 0.0% on Local Disp and SE Max P: 4 No. Equations: 22 mvss004: 2D Plane Strain Thick-Walled Cylinder Analysis Type: Model Type: Comparison: Reference: Static 2D Plane Strain The MacNeal–Harder Accuracy Tests MacNeal, R.H., and Harder, R.L. "A Proposed Standard Set of Problems to Test Finite Element Accuracy." Finite Elements in Analysis and Design I. Elsevier Science Publishers, 1985. A thick-walled cylinder, modeled symmetrically, is loaded with unit internal pressure. Find the radial displacement at the inner radius for three nearly incompressible materials. Description: 1095 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: 2D solid (1) Units: IPS Dimensions: outer radius: 9.0 inner radius: 3.0 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 1000 Poisson's Ratio: • • • 0.49 (case 1) 0.499 (case 2) 0.4999 (case 3) Thermal Expansion: 0 Conductivity: 0 Constraints (UCS): placed on edges A-B & C-D: fixed in all DOF except TransR 1096 Structural and Thermal Simulation Loads: placed on edge A-D: pressure load = 1 Distribution: per unit length Spatial Variation: uniform Comparison of Results Data Theory Radial Displacement @ Inner Radius (case 1) (m=rad_disp) 5.0399e– 3 Structure 5.0395e– 3 % Difference < 0.01% Convergence %: 0.2% on Local Disp and SE Max P: 6 No. Equations: 38 Radial Displacement @ Inner Radius (case 2) (m=rad_disp) 5.0602e– 3 5.0555e– 3 0.09% Convergence %: 1.0% on Local Disp and SE Max P: 6 No. Equations: 38 Radial Displacement @ Inner Radius (case 3) (m=rad_disp) 5.0623e– 3 5.0577e– 3 0.09% 1097 Structural and Thermal Simulation - Help Topic Collection Convergence %: 0.9% on Local Disp and SE Max P: 7 No. Equations: 46 mvss005: 2D Axisymmetric Thick-Walled Cylinder Analysis Type: Model Type: Comparison: Reference: Static 2D Axisymmetric NASTRAN No. V2410 Crandall S.H., Dahl N.C. , and Larnder T.J. An Introduction to the Mechanics of Solids. 2nd ed. NY: McGraw-Hill Book Co., 1972, pp. 293-297. Find the stress at radii r = 6.5" and r = 11.5". A thick-walled cylinder is modeled axisymmetrically and subjected to internal pressure. Description: 1098 Structural and Thermal Simulation Specifications Element Type: 2D solid (3) Units: IPS Dimensions: inner radius: 6 height: 8 thickness: 6 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 0 Constraints (UCS): placed on edges A-D & B-C: fixed in TransY and RotZ Loads: placed on edge A-B: pressure load = 10 Distribution: per unit area Spatial Variation: uniform Comparison of Results Data Theory @ r= 6.5 Stress Radial (m=r6_5_radial) –8.03 MSC/ NASTRAN –8.05 Structure –7.9721 % Difference 0.72% 1099 Structural and Thermal Simulation - Help Topic Collection Stress Hoop (m=r6_5_hoop) 14.69 14.73 14.69 0.0% @ r= 11.5 Stress Radial (m=r11_5_radial) –.30 –.30 –.26636 2.98% Stress Hoop (m=r11_5_hoop) 6.96 6.96 6.96 0.0% Convergence %: 0.1% on Local Disp and SE Max P: 4 No. Equations: 54 mvss006: 3D Cantilever Beam Analysis Type: Model Type: Comparison: Reference: Static 3D NASTRAN No. V2405 Roark, R.J., and Young, W.C. Formulas for Stress and Strain. NY: McGraw-Hill Book Co., 1982, p. 96. A cantilever beam is subjected to a load at the free end. Find the deflection at the free end and the bending stress at the fixed end. Description: 1100 Structural and Thermal Simulation Specifications Element Type: beam (1) Units: IPS Dimensions: length: 30 Beam Properties: Area: 0.310 IYY: 0.0241 Shear FY: 10001 CY: 0.5 J: 0.0631 IZZ: 0.0390 Shear FZ: 10001 CZ: 0.375 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 1.0e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on point A: fixed in all DOF Loads: placed on point B: FY = 100 1101 Structural and Thermal Simulation - Help Topic Collection Distribution: N/A Spatial Variation: N/A 1 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. Comparison of Results Data Theory Deflection @ Tip (m=max_disp_y) 2.3077 MSC/ NASTRAN 2.3077 Structure 2.3077 % Difference 0.0% Bending Stress @ Fixed End (m=max_beam_bending) 38461 38461 38461 0.0% Convergence %: 0.0% on Local Disp and SE Max P: 4 No. Equations: 24 mvss007: 3D Beam with Multiple Constraints Analysis Type: Model Type: Comparison: Reference: Static 3D ANSYS No. 2 Timoshenko, S. Strength of Materials, Part I, Elementary Theory and Problems. 3rd ed. NY: D. Van Nostrand Co., Inc., 1955, p. 98, Problem 4. A standard 30" WF beam, supported as shown below, is loaded Description: 1102 Structural and Thermal Simulation on the overhangs uniformly. Find the maximum bending stress and deflection at the middle of the beam. Specifications Element Type: beam (4) Units: IPS Dimensions: length: 480 Beam Properties: Area: 50.65 IYY: 1 Shear FY: 0.8333 CY: 15 J: 7893 IZZ: 7892 Shear FZ: 0.8333 CZ: 15 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 1103 Structural and Thermal Simulation - Help Topic Collection Constraints Location placed on point B: placed on point D: Degrees of Freedom fixed in all DOF except RotY and RotZ fixed in TransY and TransZ Loads: Location/Magnitude: Distribution: Spatial Variation: uniform uniform placed on edge A-B: FY = – 833.33 placed on edge D-E: FY = – 833.33 per unit length per unit length Comparison of Results Data Theory Max Bending Stress @ Middle (m=max_beam_bending) 11400 ANSYS 11404 Structure 11404 % Difference 0.03% Max Deflection @ Middle (m=disp_center) 0.182 0.182 0.182 0.0% Convergence %: 0.3% on Local Disp and SE Max P: 4 No. Equations: 96 1104 Structural and Thermal Simulation mvss008: 3D Beam with ParallelogramShaped Shell Elements Analysis Type: Model Type: Comparison: Reference: Static 3D The MacNeal–Harder Accuracy Tests MacNeal, R.H., and Harder, R.L. "A Proposed Standard Set of Problems to Test Finite Element Accuracy." Finite Elements in Analysis and Design I. Elsevier Science Publishers, 1985. A straight cantilever beam, constructed of parallelogram-shaped elements, is subjected to four different unit loads at the free end, including • • • • extension in-plane shear out-of-plane shear twisting loads Find the tip displacement in the direction of the load for each case. Description: 1105 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: shell (3) Units: IPS Dimensions: length: 6 width: 0.2 thickness: 0.1 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 1e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on edge A-D: fixed in all DOF Loads: extension Location/Magnitude: placed on edge B-C: FX = 1 Distribution: total load Spatial Variation: uniform in_plane placed on edge B-C: FY = –1 total load uniform out_plane placed on edge B-C: FZ = 1 total load uniform twist placed on point E: MX = 1 total load N/A 1106 Structural and Thermal Simulation Comparison of Results Data Theory Tip Disp. in Direction of Load (l=extension, m=max_disp_x) 3e–5 Structure 2.998e–5 % Difference 0.06% Tip Disp. in Direction of Load (l=in_plane, m=max_disp_y) –0.1081 –0.1078 0.27% Tip Disp. in Direction of Load (l=out_plane, m=max_disp_z) 0.4321 0.4310 0.27% Tip Disp. in Direction of Load (l=twist, m=max_rot_x) 0.034081 0.03393 0.44% Convergence %: 0.9% on Local Disp and SE 1 Max P: 6 No. Equations: 396 There is a typographical error in Table 3 (p. 10) of MacNeal-Harder for the twist load on a straight beam. It should read 0.03408. 1107 Structural and Thermal Simulation - Help Topic Collection mvss009: 3D Beam with Trapezoidal-Shaped Shell Elements Analysis Type: Model Type: Comparison: Reference: Static 3D The MacNeal–Harder Accuracy Tests MacNeal, R.H., and Harder, R.L. "A Proposed Standard Set of Problems to Test Finite Element Accuracy." Finite Elements in Analysis and Design I. Elsevier Science Publishers, 1985. A straight cantilever beam, constructed of trapezoidal-shaped elements, is subjected to four different unit loads at the free end, including • • • • extension in-plane shear out-of-plane shear twisting Find the tip displacement in the direction of the load for each case. Description: 1108 Structural and Thermal Simulation Specifications Element Type: Units: shell (3) IPS Dimensions: length: 6 width: 0.2 thickness: 0.1 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 1e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on edge A-D: fixed in all DOF Loads: Location/Magnitude: Distribution: Spatial Variation: extension in_plane out_plane twist placed on edge B-C: FX = 1 placed on edge B-C: FY = –1 placed on edge B-C: FZ = 1 placed on point E: MX = 1 total load total load total load total load uniform uniform uniform N/A 1109 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory Structure % Difference Tip Disp. in Direction of Load (l=extension, m=max_disp_x) 3e–5 2.998e–5 0.08% Tip Disp. in Direction of Load (l=in_plane, m=max_disp_y) –0.1081 –0.1078 0.32% Tip Disp. in Direction of Load (l=out_plane, m=max_disp_z) 0.4321 .4307 0.32% Tip Disp. in Direction of Load (l=twist, m=max_rot_x) 0.034081 0.03393 0.44% Convergence %: 0.5% on Local Disp and SE 1 Max P: 7 No. Equations: 492 There is a typographical error in Table 3 (p. 10) of the McNeal-Harder reference for the twist load on a straight beam. It should read 0.03408. 1110 Structural and Thermal Simulation mvss010: 3D Curved Beam Modeled with Shells Analysis Type: Model Type: Static 3D Comparison: The MacNeal–Harder Accuracy Tests Reference: MacNeal, R.H., and Harder, R.L. "A Proposed Standard Set of Problems to Test Finite Element Accuracy." Finite Elements in Analysis and Design I. Elsevier Science Publishers, 1985. Description: A curved beam, spanning a 90 arc, is fixed at one end and free at the other. If the beam is subjected to in-plane and out-ofplane loads at the free end, find the tip displacement in the direction of the load for both cases. 1111 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: Units: Dimensions: shell (2) IPS outer radius: 4.32 inner radius: 4.12 thickness: 0.1 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 1e7 Poisson's Ratio: 0.25 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on edge A-D: fixed in all DOF Loads: Location/Magnitude: Distribution: Spatial Variation: in_plane out_plane placed on edge B-C: FY = 1 placed on edge B-C: FZ = 1 total load total load uniform uniform Comparison of Results Data Theory Structure % Difference Tip Displacement in Direction of Load (l=in_plane, m=tip_disp_y) 0.08734 0.08834 1.14% 1112 Structural and Thermal Simulation Tip Displacement in Direction of Load (l=out_plane, m=tip_disp_z) 0.5022 0.50057 0.32% Convergence %: 0.3% on Local Disp and SE Max P: 6 No. Equations: 234 mvss011: 3D Simply Supported Rectangular Plate Analysis Type: Model Type: Comparison: Reference: Static 3D The MacNeal–Harder Accuracy Tests MacNeal, R.H., and Harder, R.L. "A Proposed Standard Set of Problems to Test Finite Element Accuracy." Finite Elements in Analysis and Design I. Elsevier Science Publishers, 1985. A flat plate is simply supported on all four edges. One quarter of the plate is modeled using symmetry. The plate is loaded with two different loads, including uniform pressure and a point load at the center. Find the displacement at the center of the plate. Description: 1113 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: Units: Dimensions: shell (2) IPS length: 5 width: 1 thickness: 0.0001 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 1.7472e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints Location Degrees of Freedom placed on edges A-D, C-D: placed on edge A-B: placed on edge B-C: fixed in TransX, TransY, and TransZ fixed in TransY, RotX, and RotZ fixed in TransX, RotY, and RotZ Loads: Location/Magnitude: Distribution: Spatial Variation: pressure placed on all shells: pressure = 1e–4 total load per unit area uniform point placed on B: FZ = 1e–4 N/A N/A 1114 Structural and Thermal Simulation Comparison of Results Data Theory Structure % Difference Displacement @ Center (l=pressure, m=disp_z_cen) –12.97 –12.97 0.0% Displacement @ Center (l=point, m=disp_z_cen) 16.96 16.80 0.94% Convergence %: 0.8% on Local Disp and SE Max P: 9 No. Equations: 465 mvss012: 3D Clamped Rectangular Plate Analysis Type: Model Type: Comparison: Reference: Static 3D The MacNeal–Harder Accuracy Tests MacNeal, R.H., and Harder, R.L. "A Proposed Standard Set of Problems to Test Finite Element Accuracy." Finite Elements in Analysis and Design I. Elsevier Science Publishers, 1985. One quarter of a rectangular plate, clamped on four edges, is modeled using symmetry. The plate is loaded with two different loads, including uniform pressure and a point load at center. Find the displacement at the center of the plate. Description: 1115 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: Units: Dimensions: shell (2) IPS length: 5 width: 1 thickness: 0.0001 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 1.7472e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints Location Degrees of Freedom placed on edges A-D, D-C: placed on edge A-B: fixed in all DOF fixed in TransY, RotX, and RotZ 1116 Structural and Thermal Simulation placed on edge B-C: fixed in TransX, RotY, and RotZ Loads: Location/Magnitude: Distribution: Spatial Variation: pressure placed on all shells: pressure = 1e–4 per unit area uniform point placed on B: FZ = 1e–4 N/A N/A Comparison of Results Data Theory Structure % Difference Displacement @ Center (l=pressure, m=measure1) 2.56 2.604 1.71% Displacement @ Center (l=point, m=measure1) 7.23 7.194 0.49% Convergence %: 1.1% on Local Disp and SE Max P: 9 No. Equations: 823 1117 Structural and Thermal Simulation - Help Topic Collection mvss013: 3D Hemispherical Shell Analysis Type: Model Type: Comparison: Reference: Static 3D The MacNeal–Harder Accuracy Tests MacNeal, R.H., and Harder, R.L. "A Proposed Standard Set of Problems to Test Finite Element Accuracy." Finite Elements in Analysis and Design I. Elsevier Science Publishers, 1985. One quarter of an open hemisphere is modeled with symmetry and loaded with alternating point loads at 90 intervals on the equator. Find the radial displacement at any load point. Description: 1118 Structural and Thermal Simulation Specifications Element Type: Units: Dimensions: (using a one-quarter model) shell (4) IPS radius: 10 arc span: 90o thickness: 0.04 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 6.825e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints Location Degrees of Freedom placed on curve A-C: placed on curve G-E: placed on point D fixed in TransP, RotR, and RotT fixed in TransP, RotR, and RotT fixed in TransT Loads: Location/Magnitude: Distribution: Spatial Variation placed on point C: FR = –1 placed on E: FR = 1 N/A N/A N/A N/A 1119 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory Structure % Difference Radial Displacement @ Load (m=disp_rad) 0.0924 0.0933 0.97% Convergence %: 0.6% on Local Disp and SE Max P: 9 No. Equations: 965 mvss014: 3D Cantilever Beam Twisted by 90 Analysis Type: Model Type: Comparison: Reference: Static 3D The MacNeal–Harder Accuracy Tests MacNeal, R.H., and Harder, R.L. "A Proposed Standard Set of Problems to Test Finite Element Accuracy." Finite Elements in Analysis and Design I. Elsevier Science Publishers, 1985. A cantilever beam, twisted by 90 , is subjected to in-plane and out-of-plane loads at the free end. Find the tip displacement in the direction of the load for each case. Description: 1120 Structural and Thermal Simulation Specifications Element Type: solid (2) Units: IPS Dimensions: length: 12 width: 1.1 thickness: 0.32 angle of twist 90o (from fixed to free end) Material Properties: Mass Density: 0 Poisson's Ratio: 0.22 1121 Structural and Thermal Simulation - Help Topic Collection Cost Per Unit Mass: 0 Young's Modulus: 29e6 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on root surface: fixed in all DOF Loads: Location/Magnitude: Distribution: Spatial Variation: in_plane placed on free end surface: FY = 1 total load uniform out_plane placed on free end surface: FZ = 1 total load uniform Comparison of Results Data Theory Structure % Difference Tip Displacement in Direction of Load 0.005424 0.005407 0.31% 1122 Structural and Thermal Simulation (l=in_plane, m=disp_tip_y1) Tip Displacement in Direction of Load (l=out_of_plane, m=disp_tip_z1) 0.001754 0.001771 0.97% Convergence %: 0.8% on Local Disp and SE Max P: 6 No. Equations: 303 mvss015: 3D Scordelis-Lo Roof Analysis Type: Model Type: Comparison: Reference: Static 3D The MacNeal–Harder Accuracy Tests MacNeal, R.H., and Harder, R.L. "A Proposed Standard Set of Problems to Test Finite Element Accuracy." Finite Elements in Analysis and Design I. Elsevier Science Publishers, 1985. A Scordelis-Lo roof is one-quarter of an arched roof modeled using symmetry and loaded uniformly. Find the vertical displacement at the midpoint of the straight side (of the whole roof). Description: 1123 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: shell (1) Units: IPS Dimensions: (using a one-quarter model) length: 25 radius: 25 arc span: 40 thickness: 0.25 Material Properties: Mass Density: 0 Poisson's Ratio: 0 1124 Structural and Thermal Simulation Cost Per Unit Mass: 0 Young's Modulus: 4.32e8 Thermal Expansion: 0 Conductivity: 0 Constraints Location Degrees of Freedom (UCS) (UCS) (UCS) placed on curve A-B: placed on curve A-D: placed on curve C-D fixed in TransZ, RotR, and RotT fixed in TransT, RotZ, and RotR fixed in TransR and TransT Loads: Location/Magnitude: Distribution: Spatial Variation: placed on face A-B-C-D: FZ = – 90 per unit area uniform 1125 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory Structure % Difference Vertical Displacement @ Point B (m=disp_z_mid) 0.3024 0.3008 0.53% Convergence %: 0.2% on Local Disp and SE Max P: 7 No. Equations: 148 mvss016: 2D Axisymmetric Cylinder/Sphere Analysis Type: Model Type: Reference: Description: Static 2D Axisymmetric NAFEMS, LSB1, No. IC 39 An axisymmetric cylinder and half-sphere vessel is loaded with uniform internal pressure. Find the hoop stress on the outer surface at point D. 1126 Structural and Thermal Simulation Specifications Element Type: 2D shell (4) Units: MNS Dimensions: radius: 1 thickness: 0.025 Material Properties: Mass Density: 0.007 Cost Per Unit Mass: 0 Young's Modulus: 210000 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 1127 Structural and Thermal Simulation - Help Topic Collection Constraints Location Degrees of Freedom constraint1 placed on point A: placed on point E: fixed in TransX and RotZ fixed in TransY Loads: Location/Magnitude: load1 placed on all 2D shell elements: internal pressure = 1 Comparison of Results Data Theory Structure1 % Difference Szz on outer surface 38.5 38.62 0.3% Convergence %: 0.8% on Local Disp and SE 1 Max P: 7 No. Equations: 72 You cannot view the results information in the summary file. To view the results, you must define a result window for the Stress ZZ (Bottom), and query the value at 1128 Structural and Thermal Simulation point D. mvss017: 2D Tapered Membrane with Gravity Load Analysis Type: Model Type: Reference: Description: Static Plane Stress NAFEMS, LSB1, No. IC 2 A tapered membrane has uniform acceleration in the global X direction. Find the direct stress Sxx at point B. 1129 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: 2D plate (2) Units: MNS Dimensions: thickness: 0.1 Material Properties: Mass Density: 0.007 Cost Per Unit Mass: 0 Young's Modulus: 210000 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: Location Degrees of Freedom constraint1 placed on curves A-B, B-C: placed on point B: fixed in TransX fixed in TransX, TransY Loads: Location/Magnitude: load1 Global acceleration: GX=9.81 1130 Structural and Thermal Simulation Comparison of Results Data Theory Structure % Difference Stress XX at point B (m=measure1) 0.247 0.247 0% Convergence %: 0.0% on Local Disp and SE Max P: 8 No. Equations: 136 mvss018: 3D Z-Section Cantilevered Plate Analysis Type: Model Type: Reference: Description: Static 3D NAFEMS, LSB1, No. IC 29 A Z-section cantilevered plate is subjected to a torque at the free end by two uniformly distributed edge shears. Find the direct stress Sxx at the mid-plane of the plate. 1131 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: shell (6) Units: MNS Dimensions: length: 10 thickness: 0.1 Material Properties: Mass Density: 0.007 Cost Per Unit Mass: 0 Young's Modulus: 210000 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 1132 Structural and Thermal Simulation Constraints Location Degrees of Freedom constraint1 placed on curves A-B, B-C, and C-D: fixed in TransX, TransY, and TransZ Loads: Location/Magnitude: Distribution Spatial Variation load1 placed on curve E-F: FZ=0.6 placed on curve G-H: FZ=–0.6 total load total load uniform uniform Comparison of Results Data Theory Structure1 % Difference Sxx at mid-surface at point M –108.8 –110.05 1.1% 1133 Structural and Thermal Simulation - Help Topic Collection Convergence %: 0.4% on Local Disp and SE 1 Max P: 7 No. Equations: 870 You cannot view the results information in the summary file. To view the results, you must define a result window for the measure Stress XX (Top and Bottom), and query the value at point M. Then average the top (–114.9) and bottom (–105.2) values. mvss019: 3D Cylindrical Shell with Edge Moment Analysis Type: Model Type: Reference: Description: Static 3D NAFEMS, LSB1, No. IC 19 A cylindrical shell in 3D space is loaded with a uniform normal edge moment on one edge. Find the outer surface tangential stress at point E. 1134 Structural and Thermal Simulation Specifications Element Type: shell (1) Units: MNS Dimensions: radius: 1 thickness: 0.01 Material Properties: Mass Density: 0.007 Poisson's Ratio: 0.3 1135 Structural and Thermal Simulation - Help Topic Collection Cost Per Unit Mass: 0 Young's Modulus: 210000 Thermal Expansion: 0 Conductivity: 0 Constraints Location Degrees of Freedom constraint1 placed on curve A-B: placed on curves A-D and B-C: fixed in all DOF fixed in TransZ, RotX, and RotY Loads: Location/Magnitude: Distribution Spatial Variation load1 placed on curve C-D: MZ=0.001 force per unit length uniform Comparison of Results Data Theory Structure1 % Difference Sxx on outer surface 60.0 59.6 .67% 1136 Structural and Thermal Simulation at point E Convergence %: 0.9% on Local Disp and SE 1 Max P: 5 No. Equations: 66 You cannot view the results information in the summary file. To view the results, you must define a result window for measure Stress XX (Top) with Face Grid on, and query the value at point E. mvss020: Beam Sections Analysis Type: Model Type: Comparison: Reference: Static 3D Theory Roark, R.J., and Young, W.C. Formulas for Stress and Strain. 5th Edition. NY: McGraw–Hill Book Co. 1982, p. 64. A cantilever beam is subjected to transverse loads in Y and Z and axial load in X . Find the deflection at the free end, the bending stress at the fixed end, and the axial stress along the beam. Description: 1137 Structural and Thermal Simulation - Help Topic Collection This Beam Sections model contains the following element types and corresponding results: Topic Square Beam Rectangle Beam Hollow Rectangle Beam Channel Beam I-Section Beam L-Section Beam Diamond Beam Solid Circle Beam Hollow Circle Beam Ellipse Beam Hollow Ellipse Beam Note: In all cases, the displacement results are dependent upon the direction of the load. Thus, in this problem, all the results listed as Deflection at Tip may be interpreted as positive or negative. 1138 Structural and Thermal Simulation Square Beam Specifications Element Type: Square Beam Units: IPS Dimensions: a: 0.25 Beam Properties: Area: 0.0625 IYY: 0.000325521 Shear FY: 10001 CY: 0.125 J: 0.000549316 IZZ: 0.000325521 Shear FZ: 10001 CZ: 0.125 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on point A: fixed in all DOF Load: Location: Magnitude: 1139 Structural and Thermal Simulation - Help Topic Collection axial placed on point B FX=100 transverse y placed on point B FY=100 transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. Comparison of Results Data (Square Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference axial sq_d_x 1.6e–3 1.6e–3 0% transverse y sq_d_y 9.216e1 9.215996e1 0% transverse z sq_d_z 9.216e1 9.215996e1 0% 1140 Structural and Thermal Simulation Stress: Load Measure Name Theory Structure % Difference axial sq_s_ten 1.6e3 1.6e3 0% transverse y sq_s_bnd 1.152003e6 1.151999e6 0% transverse z sq_s_bnd 1.152003e6 1.151999e6 0% Convergence: Load Lcl Disp & SE Max P No. Equations axial 0% 4 264 transverse 1141 Structural and Thermal Simulation - Help Topic Collection y 0% 4 264 transverse z 0% 4 264 Rectangle Beam Specifications Element Type: Rectangle Beam Units: IPS Dimensions: b: 1 d: 0.25 Beam Properties: Area: 0.25 IYY: 0.0208333 Shear FY: 10001 CY: 0.125 J: 0.00438829 IZZ: 0.00130208 Shear FZ: 10001 CZ: 0.5 1142 Structural and Thermal Simulation Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on point A: fixed in all DOF Load: Location: Magnitude: axial placed on point B FX=100 transverse y placed on point B FY=100 transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. Comparison of Results Data (Rectangle Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference 1143 Structural and Thermal Simulation - Help Topic Collection axial rct_d_x 4.0e–4 4.0e–4 0% transverse y rct_d_y 2.304e1 2.304e1 0% transverse z rct_d_z 1.44 1.44 0% Stress: Load Measure Name Theory Structure % Difference axial rct_s_ten 4.0e2 4.0e2 0% transverse y rct_s_bnd 2.880e5 2.880e5 0% transverse z rct_s_bnd 7.200e4 7.200e4 0% 1144 Structural and Thermal Simulation Convergence: Load Lcl Disp & SE Max P No. Equations axial 0% 4 264 transverse y 0% 4 264 transverse z 0% 4 264 Hollow Rectangle Beam Specifications Element Type: Hollow Rectangle Beam Units: IPS 1145 Structural and Thermal Simulation - Help Topic Collection Dimensions: b: 1 bi: 0.875 d: 0.25 di: 0.125 Beam Properties: Area: 0.140625 IYY: 0.013855 Shear FY: 10001 CY: 0.125 J: 0.00343323 IZZ: 0.00115967 Shear FZ: 10001 CZ: 0.5 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on point A: fixed in all DOF Load: Location: Magnitude: axial placed on point B FX=100 transverse y placed on point B FY=100 1146 Structural and Thermal Simulation transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. Comparison of Results Data (Hollow Rectangle Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference axial hrct_d_x 7.112e–4 7.111e–4 0.02% transverse y hrct_d_y 2.5869e1 2.5869e1 0% transverse z hrct_d_z 2.1653 2.1653 0% Stress: Load Measure Name Theory Structure % Difference 1147 Structural and Thermal Simulation - Help Topic Collection axial hrct_s_ten 7.112e2 7.111e2 0.02% transverse y hrct_s_bnd 3.2337e5 3.2337e5 0% transverse z hrct_s_bnd 1.0826e5 1.0826e5 0% Convergence: Load Lcl Disp & SE Max P No. Equations axial transverse y 0% 0% 4 4 264 264 transverse z 0% 4 264 1148 Structural and Thermal Simulation Channel Beam Specifications Element Type: Channel Beam Units: IPS Dimensions: b: 1 di: 1 t: 0.125 tw: 0.125 Beam Properties: Area: 0.375 IYY: 0.0369466 Shear FY: 10001 CY: 0.625 J: 0.00179932 IZZ: 0.0898438 Shear FZ: 10001a CZ: 0.645833 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 1149 Structural and Thermal Simulation - Help Topic Collection Constraints: placed on point A: fixed in all DOF Load: Location: Magnitude: axial placed on point B FX=100 transverse y placed on point B FY=100 transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. Comparison of Results Data (Channel Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference axial chnl_d_x 2.6667e–4 2.6667e–4 0% transverse y chnl_d_y 3.339e–1 3.339e–1 0% 1150 Structural and Thermal Simulation transverse z chnl_d_z 8.1198e–1 8.1198e–1 0% Stress: Load Measure Name Theory Structure % Difference axial chnl_s_ten 2.6667e2 2.6667e2 0% transverse y chnl_s_bnd 2.087e4 2.087e4 0% transverse z chnl_s_bnd 5.244e4 5.244e4 0% Convergence: Load Lcl Disp & SE Max P No. Equations axial 0% 4 264 1151 Structural and Thermal Simulation - Help Topic Collection transverse y 0% 4 264 transverse z 0% 4 264 I-Section Beam Specifications Element Type: I-Section Beam Units: IPS Dimensions: b: 1 di: 1 t: 0.125 tw: 0.125 Beam Properties: Area: 0.375 J: 0.00179932 1152 Structural and Thermal Simulation IYY: 0.0209961 Shear FY: 10001 CY: 0.625 IZZ: 0.0898438 Shear FZ: 10001 CZ: 0.5 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on point A: fixed in all DOF Load: Location: Magnitude: axial placed on point B FX=100 transverse y placed on point B FY=100 transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. 1153 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data (I-Section Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference axial I_d_x 2.6667e–4 2.6667e–4 0% transverse y I_d_y 3.3391e–1 3.3391e–1 0% transverse z I_d_z 1.4288 1.4288 0% Stress: Load Measure Name Theory Structure % Difference axial I_s_ten 2.6667e2 2.6667e2 0% 1154 Structural and Thermal Simulation transverse y I_s_bnd 2.0870e4 2.0870e4 0% transverse z I_s_bnd 7.1442e4 7.1442e4 0% Convergence: Load Lcl Disp & SE Max P No. Equations axial 0% 4 264 transverse y 0% 4 264 transverse z 0% 4 264 1155 Structural and Thermal Simulation - Help Topic Collection L-Section Beam Specifications Element Type: L-Section Beam Units: IPS Dimensions: b: 1 d: 1 t: 0.125 tw: 0.125 Beam Properties: Area: 0.25 IYY: 0.0105794 Shear FY: 10001 CY: 0.789352 J: 0.00119955 IZZ: 0.0423177 Shear FZ: 10001 CZ: 0.433047 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 1156 Structural and Thermal Simulation Constraints: placed on point A: fixed in all DOF Load: Location: Magnitude: axial placed on point B FX=100 transverse y placed on point B FY=100 transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. Comparison of Results Data (L-Section Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference axial L_d_x 4.0e–4 4.0e–4 0% transverse y L_d_y 7.0892e–1 7.0892e–1 0% 1157 Structural and Thermal Simulation - Help Topic Collection transverse z L_d_z 2.8357 2.8357 0% Stress: Load Measure Name Theory Structure % Difference axial L_s_ten 4e2 4e2 0% transverse y L_s_bnd 5.5611e4 5.5959e4 0.62% transverse z L_s_bnd 1.228e5 1.228e5 0% Convergence: Load Lcl Disp & SE Max P No. Equations 1158 Structural and Thermal Simulation axial 0% 4 264 transverse y 0% 4 264 transverse z 0% 4 264 Diamond Beam Specifications Element Type: Diamond Beam Units: IPS Dimensions: b: 0.25 d: 0.25 Beam Properties: Area: 0.03125 J: 0.000146484 1159 Structural and Thermal Simulation - Help Topic Collection IYY: 8.13802e–5 Shear FY: 10001 CY: 0.125 IZZ: 8.13802e–5 Shear FZ: 10001 CZ: 0.125 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on point A: fixed in all DOF Load: Location: Magnitude: axial placed on point B FX=100 transverse y placed on point B FY=100 transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. 1160 Structural and Thermal Simulation Comparison of Results Data (Diamond Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference axial dmnd_d_x 3.2e–3 3.2e–3 0% transverse y dmnd_d_y 3.6864e2 3.6864e2 0% transverse z dmnd_d_z 3.6864e2 3.6864e2 0% Stress: Load Measure Name Theory Structure % Difference axial dmnd_s_ten 3.2e3 3.2e3 0% transverse y dmnd_s_bnd 4.608e6 4.608e6 0% 1161 Structural and Thermal Simulation - Help Topic Collection transverse z dmnd_s_bnd 4.608e6 4.608e6 0% Convergence: Load Lcl Disp & SE Max P No. Equations axial 0% 4 264 transverse y 0% 4 264 transverse z 0% 4 264 1162 Structural and Thermal Simulation Solid Circle Beam Specifications Element Type: Solid Circle Beam Units: IPS Dimensions: r: 0.25 Beam Properties: Area: 0.19635 IYY: 0.00306796 Shear FY: 10001 CY: 0.25 J: 0.00613592 IZZ: 0.00306796 Shear FZ: 10001 CZ: 0.25 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on point A: fixed in all DOF Load: Location: Magnitude: 1163 Structural and Thermal Simulation - Help Topic Collection axial placed on point B FX=100 transverse y placed on point B FY=100 transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. Comparison of Results Data (Solid Circle Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference axial crcl_d_x 5.093e–4 5.093e–4 0% transverse y crcl_d_y 9.77848 9.77848 0% transverse z crcl_d_z 9.77848 9.77848 0% 1164 Structural and Thermal Simulation Stress: Load Measure Name Theory Structure % Difference axial crcl_s_ten 5.093e2 5.093e2 0% transverse y crcl_s_bnd 2.44462e5 2.44462e5 0% transverse z crcl_s_bnd 2.44462e5 2.44462e5 0% Convergence: Load Lcl Disp & SE Max P No. Equations axial 0% 4 264 transverse 1165 Structural and Thermal Simulation - Help Topic Collection y 0% 4 264 transverse z 0% 4 264 Hollow Circle Beam Specifications Element Type: Hollow Circle Beam Units: IPS Dimensions: ri: 0.25 Beam Properties: Area: 0.147262 IYY: 0.00287621 Shear FY: 10001 CY: 0.25 J: 0.00575243 IZZ: 0.00287621 Shear FZ: 10001 CZ: 0.25 Material Properties: Mass Density: 0 Poisson's Ratio: 0.3 1166 Structural and Thermal Simulation Cost Per Unit Mass: 0 Young's Modulus: 3e7 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on point A: fixed in all DOF Load: Location: Magnitude: axial placed on point B FX=100 transverse y placed on point B FY=100 transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. Comparison of Results Data (Hollow Circle Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference axial hcr_d_x 6.7906e–4 6.7906e–4 0% 1167 Structural and Thermal Simulation - Help Topic Collection transverse y hcr_d_y 1.04304e1 1.04304e1 0% transverse z hcr_d_z 1.04304e1 1.04304e1 0% Stress: Load Measure Name Theory Structure % Difference axial hcr_s_ten 6.7906e2 6.7906e2 0% transverse y hcr_s_bnd 2.6076e5 2.6076e5 0% transverse z hcr_s_ten 2.6076e5 2.6076e5 0% Convergence: Load Lcl Disp Max No. 1168 Structural and Thermal Simulation & SE P Equations axial 0% 4 264 transverse y 0% 4 264 transverse z 0% 4 264 Ellipse Beam Specifications Element Type: Ellipse Beam Units: IPS Dimensions: a: 1 b: 0.25 1169 Structural and Thermal Simulation - Help Topic Collection Beam Properties: Area: 0.785398 IYY: 0.19635 Shear FY: 10001 CY: 0.25 J: 0.0461999 IZZ: 0.0122718 Shear FZ: 10001 CZ: 1 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on point A: fixed in all DOF Load: Location: Magnitude: axial placed on point B FX=100 transverse y placed on point B FY=100 transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. 1170 Structural and Thermal Simulation Comparison of Results Data (Ellipse Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference axial elps_d_x 1.2732e–4 1.2732e–4 0% transverse y elps-d_y 1.527887e–1 1.527887e–1 0% transverse z elps_d_z 2.4446 2.4446 0% Stress: Load Measure Name Theory Structure % Difference axial elps_s_ten 1.273239e2 1.27324e2 0% transverse y elps_s_bnd 1.527887e4 1.527884e4 0% 1171 Structural and Thermal Simulation - Help Topic Collection transverse z elps_s_bnd 6.11155e4 6.111573e4 0% Convergence: Load Lcl Disp & SE Max P No. Equations axial 0% 4 264 transverse y 0% 4 264 transverse z 0% 4 264 1172 Structural and Thermal Simulation Hollow Ellipse Beam Specifications Element Type: Hollow Ellipse Beam Units: IPS Dimensions: a: 1 b: 0.25 ai: 0.875 Beam Properties: Area: 0.184078 IYY: 0.081253 Shear FY: 10001 CY: 0.25 J: 0.0191184 IZZ: 0.00507832 Shear FZ: 10001 CZ: 1 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on point A: fixed in all DOF 1173 Structural and Thermal Simulation - Help Topic Collection Load: Location: Magnitude: axial placed on point B FX=100 transverse y placed on point B FY=100 transverse z 1 placed on point B FZ=100 Structure beams consider shear; however, the represented theoretical problem does not. The values for shear factor compensate for this. Comparison of Results Data (Hollow Ellipse Beam) Deflection at Tip: Load Measure Name Theory Structure % Difference axial hel_d_x 5.4325e–4 5.4325e–4 0% transverse y hel_d_y 3.6922e–1 3.6922e–1 0% transverse z hel_d_z 5.9075 5.9075 0% 1174 Structural and Thermal Simulation Stress: Load Measure Name Theory Structure % Difference axial hel_s_ten 5.4325e2 5.4325e2 0% transverse y hel_s_bnd 3.6922e4 3.6922e4 0% transverse z hel_s_bnd 1.4769e5 1.4769e5 0% Convergence: Load Lcl Disp & SE Max P No. Equations axial 0% 4 264 transverse 1175 Structural and Thermal Simulation - Help Topic Collection y 0% 4 264 transverse z 0% 4 264 mvss021:Thick-Walled Cylinder Under Internal Pressure Analysis Type: Model Type: Reference: Static 3D Roark, R.J., and Young, W.C. Formulas for Stress and Strain. NY: McGraw-Hill Book Co., 5th edition, Table 32, Case 1. A thick-walled cylinder subjected to an internal pressure is free to expand in all directions. Obtain maximum radial and circumferential stresses. Description: 1176 Structural and Thermal Simulation Specifications Element Type: tets (133) Units: IPS Dimensions: length: 20 Ro: 6 Ri: 4 Material Properties: Mass Density: 0.0002614 Poisson's Ratio: 0.33 1177 Structural and Thermal Simulation - Help Topic Collection Cost Per Unit Mass: 0 Young's Modulus: 1.06e7 Thermal Expansion: 1.25e–05 Conductivity: 9.254 Constraints Location Degrees of Freedom constraint1 placed on point A: placed on point B: placed on point D: fixed in TransX, TransY, and TransZ fixed in TransY fixed in TransY and TransZ Loads: Location/Magnitude: Distribution Spatial Variation pressure placed on all internal surfaces: — pressure = 1000 total load/unit area uniform Comparison of Results Data Theory Structure % Difference 1178 Structural and Thermal Simulation yy along edges C-E & F-G 2600 2630 1.2% xx along edges C-E & F-G 1000 1003 0.03% Multi-Pass Convergence %: The analysis converged to within 0.2% on measures. Max P: 7 No. Equations: 12411 mvss022: Thin-Walled Spherical Vessel Under Its Own Weight Analysis Type: Model Type: Reference: Static 3D — Cyclic Symmetric Roark, R.J., and Young, W.C. Formulas for Stress and Strain. NY: McGraw-Hill Book Co., 5th edition, Table 29, Case 3c. A thin-walled half-spherical vessel is subjected to its own weight (gravity load). Obtain the hoop stress at points A and B. Description: 1179 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: shells (3) Units: IPS Dimensions: R: 10 Material Properties: Mass Density: 0.0002588 Cost Per Unit Mass: 0 Young's Modulus: 1.0e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 1180 Structural and Thermal Simulation Constraints Location Degrees of Freedom constraint1 Edges @ =0& = 90: cyclical symmetry fixed in TransZ fixed in TransR, TransT, and TransZ Edge @ z = 0: Placed on point C @ r = 10, = 0, z = 0: Load: Direction: Magnitude: gravity x y z 0.0 386.4 0.0 Comparison of Results Data Theory Structure % Difference zz at point A: 1 0.989 1.1% 1181 Structural and Thermal Simulation - Help Topic Collection tt at point B: -1 -0.983 1.7% Multi-Pass Adaptive Convergence %: The analysis converged to within 4.9% on Local Displacement and Element Strain Energy. It converged to 1.7% on Global RMS Stress. Max P: 9 No. Equations: 773 mvsl001: Static Analysis of Composite Lay-up Analysis Type: Model Type: Comparison: Reference: Static with Orthotropic Material Properties 3D Theory Noor, A.K. and Mathers, M.D., "Shear-Flexible Finite-Element Models of Laminated Composite Plates and Shells." NASA TN D8044; Langley Research Center, Hampton, Va. Dec. 1975. Determine maximum resultant bending moment and transverse deformation in a clamped, nine-layered, orthotropic square plate. Description: 1182 Structural and Thermal Simulation Specifications Element Type: shell (4) Units: IPS Dimensions: length: 2.5 width: 2.5 thickness: 0.5 Shell Properties: 1183 Structural and Thermal Simulation - Help Topic Collection Extensional Stiffness A11=10.266 A12=0.1252 A16=0 A22=10.266 A26=0 A66=0.3 Extensional–Bending Coupling Stiffness B11=0 B12=0 B16=0 B22=0 B26=0 B66=0 Bending Stiffness D11=0.25965 D12=0.0026082 D16=0 D22=0.1681 D26=0 D66=0.00625 1184 Structural and Thermal Simulation Transverse Shear Stiffnesses A55=0.275004 A45=0 A44=0.275004 Mass per Unit Area 7.2915e–5 Rotary Inertia per Unit Area 1.5191e–5 Thermal Resultant Coefficients: Force N11=0 N22=0 N12=0 Moment M11=0 M22=0 M12=0 Stress Recovery Locations CZ Ply Orientation (Degrees) Material Location Reported for "Top" in Results 0.25 0 trniso1 Location Reported for "Bottom" in Results –0.25 0 trniso1 1185 Structural and Thermal Simulation - Help Topic Collection Material Properties: Mass Density: 0.00014583 Cost Per Unit Mass: 0 Young's Moduli E1=4e1 E2=1 E3=1 Poisson's Ratio Nu21=0.25 Nu31=0.25 Nu32=0 Shear Moduli G21=0.6 G31=0.6 G32= E2/[2*(1+Nu32)] Coefficients of Thermal Expansion a1=0 a2=0 a3=0 Constraints: • • symmetry constraints on edges B-C and C-D clamped on edges A-B and A-D Loads: uniform pressure load over the entire surface = 1 1186 Structural and Thermal Simulation Comparison of Results Data Theory Structure % Difference Displacement 11.596 11.596 0% Bending Moment1 1.4094 1.40638 0.21% Convergence %: 0.2 % on local displacement and element strain energy and 0.5% on global RMS stress. Max P: 5 No. Equations: 223 To verify this Mechanica result, create a query result window for the quantity — Moment:Shell Resultant:XX. Show the result window and query for the value in the upper left corner of the model. This is obtained using View:Model Min. The absolute value of this negative number is greater than the value reported using View:Model Max and is reported here. 1 1187 Structural and Thermal Simulation - Help Topic Collection Modal Analysis Problems This chapter contains modal analysis problems and Mechanica's results. In a modal analysis, Structure calculates the natural frequencies and mode shapes of your model. Structure also automatically calculates all predefined measures. This list of measures differs based on the analysis type. This chapter contains the following modal problems: Topic mvsm001: 2D Plane Strain Shell Cantilever Plate mvsm002: 2D Plane Stress Cantilever Plate mvsm003: 2D Plane Strain Solid Cantilever Plate mvms004: 2D Axisymmetric Radial Vibration of an Annulus mvsm005: 3D Radial Vibration of a Ring mvsm006: 3D Cantilever Wedge-Shaped Plate mvsm007: 3D Cantilever Cylindrical Shell mvsm008: 3D Solid Wedge-Shaped Plate mvsm009: 3D In-Plane Vibration of a Pin-Ended Cross mvsm010: 3D Annular Plate Axisymmetric Vibration mvsm001: 2D Plane Strain Shell Cantilever Plate Analysis Type: Modal Model Type: 2D Plane Strain Comparison: Theoretical Results 1188 Structural and Thermal Simulation Reference: Roark, R.J. and Young, W.C. Formulas for Stress and Strain. NY: McGraw-Hill Book Co. 1982. pp. 576–578. Description: Find the fundamental frequency of a cantilever plate modeled as a plane strain model. Specifications Element Type: 2D shell (1) Units: MKS Dimensions: width: 2 thickness: 0.01 Material Properties: Mass Density: 7850 Cost Per Unit Mass: 0 Young's Modulus: 2e11 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraint: placed on point A: fixed in all DOF 1189 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory Structure % Difference Fundamental Frequency (Hz) (mode=1) 2.1393 2.1375 0.08% Convergence %: 0.4% on Frequency Max P: 4 No. Equations: 12 mvsm002: 2D Plane Stress Cantilever Plate Analysis Type: Modal Model Type: 2D Plane Stress Comparison: Theoretical Results Reference: Roark, R.J. and Young, W.C. Formulas for Stress and Strain. NY: McGraw-Hill Book Co. 1982. pp. 576–578. Description: Find the fundamental frequency for the lateral vibration of a cantilever plate. 1190 Structural and Thermal Simulation Specifications Element Type: 2D plate (1) Units: IPS Dimensions: length: 36 width: 4 thickness: 0.1 Material Properties: Mass Density: 7.28e–4 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraint: placed on edge A-B: fixed in TransX and TransY 1191 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory Structure % Difference Fundamental Frequency (Hz) (mode=1) 101.326 100.99 0.33% Convergence %: 0.4% on Frequency Max P: 6 No. Equations: 42 mvsm003: 2D Plane Strain Solid Cantilever Plate Analysis Type: Modal Model Type: 2D Plane Strain Comparison: Theoretical Results Reference: Roark, R.J., and Young, W.C. Formulas for Stress and Strain, NY: McGraw-Hill Book Co. 1982. pp. 576–578. Description: Find the fundamental frequency of a cantilever plate modeled as a plane strain model. 1192 Structural and Thermal Simulation Specifications Element Type: 2D solid (2) Units: IPS Dimensions: length: 36 width: 4 Material Properties: Mass Density: 7.28e–4 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraint: placed on edge A-B: fixed in TransX, TransY, and RotZ 1193 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory Structure % Difference Fundamental Frequency (Hz) (mode=1) 106.219 106.50 0.26% Convergence %: 1.0% on Frequency Max P: 5 No. Equations: 58 mvsm004: 2D Axisymmetric Radial Vibration of an Annulus Analysis Type: Modal Model Type: 2D Axisymmetric Comparison: ANSYS No. 67 Reference: Timoshenko, S., and Young, D.H. Vibration Problems in Engineering. 3rd ed. NY: D. Van Nostrand Co., Inc. 1955. p. 425, Art. 68. Description: Find the fundamental frequency for the radial vibration of an annulus modeled axisymmetrically. 1194 Structural and Thermal Simulation Specifications Element Type: 2D solid (1) Units: IPS Dimensions: inner radius: 99.975 outer radius: 100.025 height: 0.05 Material Properties: Mass Density: 7.3e–4 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on edge A-B: fixed in TransY and RotZ placed on edge C-D: fixed in TransY and Rot Z 1195 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory ANSYS Structure % Difference Radial Frequency (Hz) (model=1) 322.64 322.64 322.64 0.0% Convergence %: 0.0% on Frequency Max P: 2 No. Equations: 10 mvsm005: 3D Radial Vibration of a Ring Analysis Type: Modal Model Type: 3D Comparison: Theoretical Results Reference: Love, A.E.H. A Treatise on the Mathematical Theory of Elasticity. 4th ed. NY: Dover Publications. 1944. p. 452, Art. 293b. Description: Determine the first and second modal frequencies for the radial vibration of a ring modeled as a one-quarter model. 1196 Structural and Thermal Simulation Specifications Element Type: beam (1) Units: IPS Dimensions: radius: 2 Beam Properties: Area: 0.01 IYY: 1e–3 Shear FY: 0.83333 CY: 1 J: 1.008e–3 IZZ: 8.33e–6 Shear FZ: 0.83333 CZ: 1 Material Properties: Mass Density: 7.28e–4 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 1197 Structural and Thermal Simulation - Help Topic Collection Constraints: placed on point A: fixed in all DOF except TransX placed on point B: fixed in all DOF except TransY Comparison of Results Data Theory Structure % Difference Mode 1 Frequency (Hz) 625.65 624.43 0.19% Mode 2 Frequency (Hz) 3393.06 3369.13 0.70% Convergence %: 0.0% on Frequency Max P: 9 No. Equations: 50 mvsm006: 3D Cantilever Wedge-Shaped Plate Analysis Type: Modal Model Type: 3D Comparison: ANSYS No. 62 Reference: Timoshenko, S., and Young, D.H. Vibration Problems in Engineering. 3rd ed. NY: D. Van Nostrand Co., Inc. 1955. p. 392, Art. 62. Description: Find the fundamental frequency for the lateral vibration of a cantilever, wedge-shaped plate. 1198 Structural and Thermal Simulation Specifications Element Type: shell (1) Units: IPS Dimensions: length: 16 width: 4 thickness: 1 Material Properties: Mass Density: 7.28e–4 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 0 Constraint: placed on edge A-B: fixed in all DOF 1199 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory ANSYS Structure % Difference Frequency (Hz) (mode=1) 259.16 260.99 259.15 0.004% Convergence %: 0.0% on Frequency Max P: 4 No. Equations: 60 mvsm007: 3D Cantilever Cylindrical Shell Analysis Type: Modal Model Type: 3D Comparison: Theoretical results Reference: Roark, R.J., and Young, W.C. Formula for Stress and Strain. NY: McGraw-Hill Co. 1982. p. 576. Description: A cantilever cylindrical shell is modeled as a half cylinder using symmetry. Find the fundamental frequency. 1200 Structural and Thermal Simulation Specifications Element Type: shell (3) Units: IPS Dimensions: length: 36 radius: 1 thickness: 0.1 Material Properties: Mass Density: 7.28e–4 Poisson's Ratio: 0.3 1201 Structural and Thermal Simulation - Help Topic Collection Cost Per Unit Mass: 0 Young's Modulus: 3e7 Thermal Expansion: 0 Conductivity: 0 Constraint: placed on edge A-B: fixed in all DOF placed on edge A-C, B-D: fixed in TransX, RotY, and RotZ Comparison of Results Data Theory Structure % Difference Frequency (Hz) (mode=1) 62.05 62.08 0.05% Convergence %: 0.3% on Frequency Max P: 6 No. Equations: 246 mvsm008: 3D Solid Wedge-Shaped Plate Analysis Type: Modal Model Type: 3D Comparison: ANSYS No. 62 Reference: Timoshenko, S., and Young, D.H. Vibration Problems in Engineering. 3rd ed. NY: D. Van Nostrand Co., Inc. 1955. p. 392, Art. 62. Description: Find the fundamental frequency for the lateral vibration of a cantilever, wedge-shaped plate. 1202 Structural and Thermal Simulation Specifications Element Type: solid (1) Units: IPS Dimensions: length: 16 width: 4 depth: 1 Material Properties: Mass Density: 7.28e–4 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 0 Constraint: placed on face A-B-C-D: fixed in all DOF 1203 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory ANSYS Structure % Difference Fundamental Frequency (Hz) (mode=1) 259.16 260.99 259.25 0.03% Convergence %: 0.0% on Frequency Max P: 4 No. Equations: 72 1204 Structural and Thermal Simulation mvsm009: 3D In-Plane Vibration of a PinEnded Cross Analysis Type: Modal Model Type: 3D Reference: NAFEMS, SBNFA (November 1987), Test 1. Description: Determine the first to eighth modal frequencies for the in-plane vibration of a cross with a pin joint at points A, B, C, & D. 1205 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: beam (4) Units: NMS Dimensions: length: 5 Beam Properties: Area: 0.015625 IYY: 2.0345e–5 Shear FY: 0.83333 CY: 0.0625 J: 4.069e–5 IZZ: 2.0345e–5 Shear FZ: 0.83333 CZ: 0.0625 Material Properties: Mass Density: 8000 Cost Per Unit Mass: 0 Young's Modulus: 2e11 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: placed on points A, B, C, D: fixed TransX, TransY, TransZ placed on beams A-O, B-O, C-O, D-O: fixed in TransZ Comparison of Results Data Theory Structure % Difference Mode 1 Frequency (Hz) 11.336 11.324 0.11% 1206 Structural and Thermal Simulation Mode 2 & 3 Frequency (Hz) 17.709 17.637 0.4% Mode 4 Frequency (Hz) 17.709 17.665 0.2% Mode 5 Frequency (Hz) 45.345 45.155 0.4% Mode 6 & 7 Frequency (Hz) 57.390 56.692 1.2% Mode 8 Frequency (Hz) 57.390 57.002 0.7% Convergence %: 3.4% on Frequency Max P: 8 No. Equations: 157 mvsm010: 3D Annular Plate Axisymmetric Vibration Analysis Type: Modal Model Type: 3D Reference: NAFEMS, SBNFA (November 1987), Test 53. Description: Determine the first to fifth modal frequencies for the axisymmetric vibration of an annular plate. 1207 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: solid (3) Units: NMS Dimensions: inner radius: 1.8 outer radius: 6 height: 0.6 Material Properties: Mass Density: 8000 Cost Per Unit Mass: 0 Young's Modulus: 2e11 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 1208 Structural and Thermal Simulation Constraints: Location Degrees of Freedom constraint1 placed on surfaces ABCD, BCNO, ADMP, ABMN, CDPO, MNOP fixed in TransT, RotR, and RotZ placed on curve MP fixed in TransZ Comparison of Results Data Theory Structure % Difference Modal 1 Frequency (Hz) 18.583 18.551 0.17% Modal 2 Frequency (Hz) 140.15 138.22 1.4% Modal 3 Frequency (Hz) 224.16 224.16 0% 1209 Structural and Thermal Simulation - Help Topic Collection Modal 4 Frequency (Hz) 358.29 355.80 0.7% Modal 5 Frequency (Hz) 629.19 620.43 1.4% Convergence %: 1.3 on Frequency Max P: 9 No. Equations: 1044 1210 Structural and Thermal Simulation Steady-State Thermal Analysis Problems This chapter contains thermal analysis problems and Thermal's results. In a steadystate thermal analysis, Thermal calculates the thermal response of your model to specified heat loads and subject to specified constraints. Thermal also automatically calculates all predefined measures that apply to a model. This chapter contains the following models: Topic mvts001: 3D Cooling Fin with Beam Element mvts002: 2D Plate with Convection mvts003: 2D Axisymmetric Cylinder with Prescribed Flux mvts004: 2D Axisymmetric Hollow Cylinder with Central Heat Source mvts005: 2D Unit Depth Two-Layer Wall Temperatures mvts006: 3D Cooling Fin with Solid Elements mvts007: 3D Solid Cylinder Temperature Distribution mvts008: 3D Shell with Prescribed Temperature mvts001: 3D Cooling Fin with Beam Element Analysis Type: Steady-State Thermal Model Type: 3D Comparison: ANSYS No. 95 Reference: Kreith, F. Principles of Heat Transfer. 2nd ed. PA: International Textbook Co., 1959. Description: A cooling fin of square cross-sectional area is surrounded by 1211 Structural and Thermal Simulation - Help Topic Collection fluid, with one end maintained at a certain temperature, and the other end insulated. Find the temperature at the insulated tip, B. Specifications Element Type: beam (1) Units: Hr Ft Btu F Dimensions: length: 0.6666 Beam Properties: Area: 0.00694 IYY: 0 Shear FY: 0 CY: 0 J: 0 IZZ: 0 Shear FZ: 0 CZ: 0 1212 Structural and Thermal Simulation Material Properties: Mass Density: 1 Cost Per Unit Mass: 0 Young's Modulus: 0 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 25 Prescribed Temperatures: therm_constr1 Location/Magnitude: placed on point A: 100 Convection Conditions: Location/ Film Coefficient: placed on curve A-B: 0.333332 Bulk Temperature: therm_constr1 0 Comparison of Results Data Theory Temperature at Tip B (m=tip_temp) 68.594 ANSYS 68.618 Thermal 68.583 % Difference 0.16% Convergence %: 0.0% on Local Temp and Energy Index Max P: 5 No. Equations: 5 mvts002: 2D Plate with Convection Analysis Type: Steady-State Thermal Model Type: 2D Plate Reference: NAFEMS, FEBSTA, No. T4 1213 Structural and Thermal Simulation - Help Topic Collection Description: A plate with uniform thickness is insulated on one side and surrounded by fluid on two other sides. The fourth side is maintained at a certain temperature. Find the temperature at point E. Specifications Element Type: 2D plate (2) Units: Hr M W C Dimensions: length: 1.0 width: 0.6 1214 Structural and Thermal Simulation Material Properties: Mass Density: 0.08 Cost Per Unit Mass: 0 Young's Modulus: 0 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 52 Prescribed Temperatures: therm_constr1 Location/Magnitude: placed on curve A-B: 100 Convection Conditions: Location/ Film Coefficient: placed on curves C-D, B-E, C-E: 750 Bulk Temperature: 0 therm_constr1 Comparison of Results Data Theory Temperature at Point E (m=pt_e_temp) 18.3 Thermal 18.3 % Difference 0.0% Convergence %: 1.0% on Local Temp and Energy Index Max P: 9 No. Equations: 79 mvts003: 2D Axisymmetric Cylinder with Prescribed Flux Analysis Type: Steady-State Thermal Model Type: 2D Axisymmetric 1215 Structural and Thermal Simulation - Help Topic Collection Reference: NAFEMS, BMTTA(S), No. 15(i) Description: A cylinder has a prescribed heat flux around part of the boundary. The bottom side is maintained at a certain temperature and the top is insulated. Find the temperature at point E. Specifications Element Type: 2D solid (2) Units: Hr M W C Dimensions: inner radius: 0.0 outer radius: 0.1 height: 0.05 1216 Structural and Thermal Simulation Material Properties: Mass Density: 7850 Cost Per Unit Mass: 0 Young's Modulus: 0 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 52 Prescribed Temperatures: therm_constr1 Location/Magnitude: placed on curve A-B: 0 Heat Loads therm_load1 Location/Magnitude placed on curve C-E: 500000 Distribution heat/time per unit area Spatial Variation uniform Comparison of Results Data Theory Temperature at Target Point E (m=target_pt_temp) 213.6 Thermal 213.1 % Difference 0.2% Convergence %: 0.0% on Local Temp and Energy Index Max P: 8 No. Equations: 72 mvts004: 2D Axisymmetric Hollow Cylinder with Central Heat Source Analysis Type: Steady-State Thermal Model Type: 2D Axisymmetric 1217 Structural and Thermal Simulation - Help Topic Collection Reference: NAFEMS, BMTTA(S), No. 15 (iii) Description: A hollow cylinder has a prescribed heat flux over the central part of the inner surface; the ends are insulated. The top, bottom, and outer surfaces are maintained at a uniform temperature. Find the temperature at point G. Specifications Element Type: 2D solid (2) Units: Hr M W C Dimensions: inner radius: 0.02 1218 Structural and Thermal Simulation outer radius: 0.1 height: 0.14 Material Properties: Mass Density: 7850 Cost Per Unit Mass: 0 Young's Modulus: 0 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 52 Prescribed Temperatures: Therm_constr1 Location/Magnitude: placed on curves A-B, B-C, C-D: 0 Heat Loads Therm_load1 Location/Magnitude placed on curve E-F: 500000 Distribution hear/time per unit area Spatial Variation uniform Comparison of Results Data Theory Temperature at Target Point G (m=target_pt_temp) 59.82 Thermal 59.85 % Difference 0.05% Convergence %: 0.0% on Local Temp and Energy Index Max P: 9 No. Equations: 133 1219 Structural and Thermal Simulation - Help Topic Collection mvts005: 2D Unit Depth Two-Layer Wall Temperatures Analysis Type: Steady-State Thermal Model Type: 2D Unit Depth Comparison: ANSYS No. 92 Reference: Kreith, F. Principles of Heat Transfer. 2nd ed. PA: International Textbook Co., 1959. Description: A two-layer wall is surrounded by heated fluid on both the inner and outer surfaces; the ends are insulated. Find the temperatures at the inner and outer surfaces. 1220 Structural and Thermal Simulation Specifications Element Type: 2D solid (2) Units: Hr Ft Btu F Dimensions: thickness of layer 1: 0.75 thickness of layer 2: 0.416666 Material Properties: Mass Density: 1 Cost Per Unit Mass: 0 Young's Modulus: 0 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: • • layer 1 (K1): 0.8 layer 2 (K2): 0.1 Convection Conditions: Therm_constr1 Location/Film Coefficient: placed on curve A-B: 12 placed on curve C-D: 2 Bulk Temperature: 3000 80 Comparison of Results Data Theory Temperature at Inner Surface (m=inner_temp_1) 2957 ANSYS 2957.2 Thermal 2957.2 % Difference N/A Temperature at Outer Surface (m=outer_temp_1) 336 336.7 336.7 0.2% Convergence %: 0.0% on Local Temp and Energy Index Max P: 2 No. Equations: 13 1221 Structural and Thermal Simulation - Help Topic Collection mvts006: 3D Cooling Fin with Solid Elements Analysis Type: Steady-State Thermal Model Type: 3D Comparison: ANSYS No. 96 Reference: Kreith, F. Principles of Heat Transfer. 2nd ed. PA: International Textbook Co., 1959. Description: A cooling fin of square cross-sectional area is surrounded by fluid with one end maintained at a certain temperature, and the other end insulated. Find the temperature at the insulated tip (surface EFGH). 1222 Structural and Thermal Simulation Specifications Element Type: solid (2) Units: Hr Ft Btu F Dimensions: length: 0.6666 width: 0.083333 height: 0.083333 Material Properties: Mass Density: 1 Cost Per Unit Mass: 0 Young's Modulus: 0 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 25 Prescribed Temperatures: thermal_constr1 Location/Magnitude: placed on surface ABCD: 100 Convection Conditions: therm_constr1 Location/Magnitude: Bulk Temperature: 0 placed on all outer surfaces except surfaces ABCD and EFGH: 1 1223 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory Temperature at Tip (m=tip_temp_1) 68.592 ANSYS 68.618 Thermal 68.533 % Difference 0.09% Convergence %: 0.0% on Local Temp and Energy Index Max P: 9 No. Equations: 303 mvts007: 3D Solid Cylinder Temperature Distribution Analysis Type: Steady-State Thermal Model Type: 3D Comparison: ANSYS No. 101 Reference: Schneider, P. J. Conduction Heat Transfer. 2nd ed. MA: Addison-Wesley Publishing Co., Inc., 1957. Description: A short, solid cylinder is subjected to prescribed temperatures over all surfaces. Find the temperature distribution in the cylinder. 1224 Structural and Thermal Simulation Specifications Element Type: solid 1(2) Units: Hr Ft Btu F Dimensions: outer radius: 0.5 height: 0.5 Material Properties: Mass Density: 1 Cost Per Unit Mass: 0 Young's Modulus: 0 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 1.0 Prescribed Temperatures: Location/Magnitude: 1225 Structural and Thermal Simulation - Help Topic Collection therm_constr1 placed on surface EMN (top): 40 placed on surfaces AKL (bottom) and KLMN (outer surface): 0 Comparison of Results Data Theory Point A (m=node_1_temp) 0 ANSYS 0 Thermal 0.0 % Difference 0.0% Point B (m=node_11_temp) 6.8 7.4427 6.8533 0.8% Point C (m_node_21_temp) 15.6 16.361 15.3693 1.5% Point D (m_node_31_temp) 26.8 27.411 26.5707 0.9% Point E (m=node_41_temp) 40 40 40.0 0.0% Convergence %: 1.4% on Local Temp and Energy Index Max P: 9 No. Equations: 622 mvts008: 3D Shell with Prescribed Temperature Analysis Type: Steady-State Thermal Model Type: 3D Reference: 1226 NAFEMS, BMTTA(S), No. 9 (i) Structural and Thermal Simulation Description: A plate has a prescribed temperature distributed evenly around its boundary. No internal heat is generated. Find the temperature at point E. Specifications Element Type: Shell (10) Units: Hr M W C Dimensions: length: 0.6 width: 0.4 thickness: 1 1227 Structural and Thermal Simulation - Help Topic Collection Material Properties: Mass Density: 7850 Cost Per Unit Mass: 0 Young's Modulus: 0 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 52 Prescribed Temperatures: therm_constr1 Location/Magnitude: placed on curve A-B: 1000 placed on curves A-D, C-D, B-C: 0 Comparison of Results Data Theory Temperature at Target Point E (m=target_pt_temp) 260.5 Thermal 260.6 % Difference 0.04% Convergence %: 2.0% on Local Temp and Energy Index Max P: 9 No. Equations: 198 1228 Structural and Thermal Simulation Transient Thermal Analysis Problems This chapter contains transient thermal analysis problems and Thermal's results. In a transient thermal analysis, Thermal calculates the thermal response of your model to heat loads that change with time and that are subject to specified constraints. Thermal also automatically calculates all predefined measures that apply to a model. This section contains the following models: Topic mvtt001: 3D Solid Transient Heat Flow mvtt002: 3D Solid Plate with Convection mvtt001: 3D Solid Transient Heat Flow Analysis Type: Transient Thermal Model Type: 3D Comparison: Theory Reference: Holman, J.P. Heat Transfer. 5th ed. McGraw-Hill Book Co., Inc., 1981. Example 4.2. Description: A large solid cylinder of steel is at an initial uniform temperature of 35 C. One end is then exposed to a constant surface heat flux of 3.2e5 W/m2. Find the temperature after 30 s at a depth of 2.5 cm from the heated end. 1229 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: tet (167) Units: smW C Dimensions: radius 0.25 length 6.5 Properties: Mass Density 8000 kg/m3 Thermal Expansion 1.4e-5 m2/s Conductivity 45 W/m C Specific Heat 401.79 J/kg C 1230 Structural and Thermal Simulation Prescribed Temps: Location/Magnitude: therm_constr1 everywhere: 35 C therm_load1 placed on surface ABDC: 320000 W/m2 Comparison of Results Data Theory Thermal % Difference Point E (m=temp_2_5) 79.3 79.05 0.31% Single-Pass Adaptive Convergence Max P: 6 No. Equations: 3046 mvtt002: 3D Solid Plate with Convection Analysis Type: Transient Thermal Model Type: 3D Comparison: Theory Reference: Holman, J.P. Heat Transfer. 5th ed. McGraw-Hill Book Co., Inc., 1981. Example 4.5. Description: A plate of steel is at an initial uniform temperature of 200 C. All exposed surfaces of the plate are then suddenly subjected to a 1231 Structural and Thermal Simulation - Help Topic Collection convection condition of 70 C with a heat transfer coefficient of 525 W/m2 C. Find the temperature after 60 s at a depth of 1.25 cm from one of the exposed faces. Specifications Element Type: solid (48) Units: smW C Dimensions: width: 0.3 height: 0.3 thickness: 0.05 Properties: Mass Density 2700 kg/m3 Specific Heat 900 J/kg C Conductivity 215 W/m C 1232 Structural and Thermal Simulation Prescribed Temps: therm_constr1 Location/Magnitude: placed on all exposed surfaces • • thermal transfer coefficient: 525 W/m2 C bulk temperature: 70 C Initial temperature entire body at 200 C Comparison of Results Data Theory Thermal % Difference Point A (m=pnt_1_25cm) 147.7 144.12 2.42% Single-Pass Adaptive Convergence Max P: 4 No. Equations: 964 1233 Structural and Thermal Simulation - Help Topic Collection Dynamic Time Response Analysis Problem This chapter contains a dynamic time response analysis problem and Mechanica's results. In a dynamic time response analysis, Structure calculates the response of your model to time-varying loads. Structure also automatically calculates all predefined measures. This list of measures differs based on the analysis type. mvst001: 3D Mass-Spring-Damper System Analysis Type: Dynamic Time Response Model Type: 3D Comparison: ANSYS No. 74 Reference: Thomson, W.T. Vibration Theory and Applications. NJ: PrenticeHall, Inc. 2nd printing, 1965. p. 99, Article 4.1. Description: A mass-spring system is subjected to an impact load, and thereafter undergoes free vibration. Determine the deflection at time t = 0.1 sec for a damped and undamped system. 1234 Structural and Thermal Simulation Specifications mass (1), spring (1) Element Type: Units: IPS Dimensions: spring length: 10 (arbitrary) Mass Properties: M: 0.5 Mxx: 0 Mxy: 0 Mxz: 0 Myy: 0 Myz: 0 Mzz: 0 Spring Properties: (extensional stiffness) Kxx: 200 Kxy: 0 Kxz: 0 Kyy: 0 Kyz: 0 Kzz: 0 1235 Structural and Thermal Simulation - Help Topic Collection Constraints: placed on point A: fixed in all DOF placed on point B: fixed in all DOF except TransY Loads: placed on point B: FY = 10 Distribution: N/A Spatial Variation: N/A Comparison of Results Data % Difference < 0.01% Theory Max Deflection @ t = 0.1 (a=undamped) 0.909297 ANSYS 0.90693 Structure1 0.9093 Max Deflection @ t = 0.1 (a=damped, damping=70%) 0.3418 0.34252 0.3418 0.0% Convergence %: 0.0% on Frequency Max P: N/A No. Equations: 1 1 You cannot view the results information in the summary file. To view the results, you must define a displacement result window and query the result at t = 0.1. 1236 Structural and Thermal Simulation Dynamic Frequency Response Analysis Problem This chapter contains a dynamic frequency response analysis problem and Structure's results. In a dynamic frequency response analysis, Structure calculates the amplitude and phase of displacements, velocities, accelerations, and stresses in your model in response to a load oscillating at different frequencies. Structure also automatically calculates all predefined measures. This list of measures differs based on the analysis type. mvsf001: Harmonic Response of a Two-Mass Spring System Analysis Type: Dynamic Frequency Model Type: 3D Comparison: ANSYS No. 90 Reference: Thomson, W. T. Vibration Theory and Applications. PrenticeHall, Inc., Englewood Cliffs, N. J., 2nd Printing, 1965. Description: Determine the response of the two-mass-spring system when excited by a harmonic force acting on mass at point B. 1237 Structural and Thermal Simulation - Help Topic Collection Specifications mass (2), spring (3) Element Type: Units: IPS Dimensions: spring length: 1 (arbitrary) Mass Properties: M: 0.5 Mxx: 0 Mxy: 0 Mxz: 0 Myy: 0 Myz: 0 Mzz: 0 Spring Properties: (extensional stiffness) Kxx: 200 Kxy: 0 Kxz: 0 Kyy: 0 Kyz: 0 Kzz: 0 1238 Structural and Thermal Simulation Constraints: constraint1 Location: placed on points A and D placed on points B and C Degrees of Freedom: fixed in all DOF fixed in all DOF except TransX Loads: load1 Location/Magnitude: placed on point B: FX = 200 Distribution: N/A Spatial Variation: N/A Comparison of Results Data Structure Loc. Frequency = 1.5 Hz Disp/phase at A, B (m=dispx_2, 3/ phase_2, 3) point A point B point A point B point A point B Theory 0.8227/ 0 0.4627/ 0 0.5115/ 180 1.2153/ 180 0.5851/ 180 0.2697/ 0 ANSYS 0.8227/ 0 0.4627/ 0 0.5115/ 180 1.2153/ 180 0.5851/ 180 0.2697/ 0 1 % Diff. 0% 0.8227/0 0.4627/0 0% Frequency = 4.0 Hz Disp/phase at A, B (m=dispx_2, 3/ phase_2, 3) 0.5115/18 0 1.215/180 0% 0% Frequency = 6.5Hz Disp/phase at A, B (m=dispx_2, 3/ phase_2, 3) 0.5851/18 0 0.2697/0 0% 0% Convergence %: 0% on Frequency & Local Disp 1 Max P: 1 No. Equations: 2 You cannot view the results information in the summary file. To view the results, you must define a measure result window and view the graph. 1239 Structural and Thermal Simulation - Help Topic Collection Dynamic Shock Response Analysis Problem This chapter contains a dynamic shock response analysis problem and Mechanica's results. In a dynamic shock response analysis, Structure calculates maximum values of displacements and stresses on your model in response to a base excitation with a specified response spectrum. Structure also automatically calculates all predefined measures. This list of measures differs based on the analysis type. mvsk001: Seismic Response of a Beam Structure Analysis Type: Dynamic Shock Model Type: 3D Comparison: ANSYS No. 70 Reference: Biggs, J. M. Introduction to Structural Dynamics. McGraw-Hill Book Co., New York, 1964. Description: A simply supported beam is subjected to a vertical motion of both supports. The motion is defined in terms of a seismic displacement response spectrum. Determine the fundamental displacement and the corresponding maximum bending stress. 1240 Structural and Thermal Simulation Specifications Element Type: beam (2) Units: IPS Dimensions: length: 240 height: 14 Beam Properties: Area: 273.9726 IYY: 333.333 Shear FY: 0.83333 CY: 7 J: N/A IZZ: 333.333 Shear FZ: 0.83333 CZ: 7 Material Properties: Mass Density: 0.00073 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 1241 Structural and Thermal Simulation - Help Topic Collection Constraints: constraint1 Location: placed on point A Degrees of Freedom: fixed in TransY and TransZ placed on point B fixed in TransX, TransY, TransZ placed on point C fixed in TransZ, RotX, RotY Response Spectrum: resp_spectrum1 Frequency: Displacement: 0 10 0.44 0.44 Comparison of Results Data % Difference 0.04% Theory Frequency 6.0979 ANSYS 6.0974 Structure 6.0953 Max. Displacement (m=disp_max) 0.560 0.553 0.560 0% Max. Bending Stress 20158 20156 20138 0.1% Convergence %: 0.0% on Frequency Max P: 6 No. Equations: 70 1242 Structural and Thermal Simulation Buckling Analysis Problems This chapter contains buckling analysis problems and Structure's results. In a buckling analysis, Structure calculates buckling load factors and mode shapes that determine the critical magnitudes of load at which a 3D structure will buckle. Structure also automatically calculates all predefined measures. This list of measures differs based on the analysis type. This chapter contains the following models: Topic mvsb001: Linear Buckling of a Laterally Unrestrained Frame mvsb002: Buckling Analysis of Composite Lay-up mvsb001: Linear Buckling of a Laterally Unrestrained Frame Analysis Type: Model Type: Comparison: Reference: Buckling 3D MSC/NASTRAN Cahajes, A. Principles of Structural Stability Theory. PrenticeHall, 1974, p. 180. A simple inverted U-shaped frame, clamped at points A and B. Point loads are applied at the top of each vertical column. Determine the critical buckling load. Description: 1243 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: Units: Dimensions: Beam Properties: beams IPS length: 5 Area: 10 IYY: 1e20 Shear FY: 0.83333 CY: 1 J: 1e20 IZZ: 1.907e–4 Shear FZ: 0.83333 CZ: 1 Poisson's Ratio: 0.27 Thermal Expansion: 0 Conductivity: 0 Material Properties: Mass Density: 7.32e–4 Cost Per Unit Mass: 0 Young's Modulus: 3e7 1244 Structural and Thermal Simulation Constraints: placed on points A, B: fixed in all DOF Comparison of Results Data Theory Mode 1 106.097 MSC/ NASTRAN 106.386 % Difference 0.3% Structure 106.073 % Difference 0.02% Convergence %: 0.4 % on Buckling Load Factor Max P: 4 No. Equations:66 mvsb002: Buckling Analysis of Composite Lay-up Analysis Type: Model Type: Comparison: Reference: Buckling Transversely Isotropic 3D MSC/NASTRAN Jones, R.M., Mechanics of Composite Material, Hemisphere Publishing Corp., 1975, pp 260-261. A four-layered transversely isotropic square plate is simplysupported and subjected to an in-plane load. Determine the buckling load factor. Description: 1245 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: Units: Dimensions: shell IPS length: 10 width: 10 thickness: 0.1 Shell Properties: Ply lay-up: 0/90/90/0 Extensional Stiffness A11=1.54e06 Thickness of each ply: 0.025 A12=18,779 A22=A11 A16=0 A26=0 1246 Structural and Thermal Simulation A66=37,500 Extensional– Bending Coupling Stiffness B11=0 B12=0 B22=0 B16=0 B26=0 B66=0 Bending Stiffness D11=2,198.75 D12=15.6495 D22=367.762 D16=0 D26=0 D66=31.25 Transverse Shear Stiffnesses Material Properties: Mass Density: 0.002 Young's Moduli Poisson's Ratio Shear Moduli E1=3e7 Nu21=0.25 G21=375,000 Cost Per Unit Mass: 0 E2=750,000 Nu31=0.25 G31=375,000 E3=750,000 Nu32=0 G32= E2/[2*(1+Nu32)] Coefficients of Thermal Expansion Constraints: a1=0 a2=0 a3=0 A55=27,585 A45=0 A44=17,925 • • • Fixed outer Fixed Fixed in out of plane (z-direction) translation along all edges (AB, BC, CD, and DA). in translation in all directions at point D in x & z-direction translation at point A Loads: In-plane force/unit length load=1: • • in +x-direction along edge DA in -x-direction along edge BC 1247 Structural and Thermal Simulation - Help Topic Collection Comparison of Results Data Theory Buckling Load Factor 268.73 Structure 267 Max P: 6 % Difference 0.6% No. Equations: 455 Convergence %: 1.0 % on buckling load factor. 1248 Structural and Thermal Simulation 2D-3D Contact Analysis Problems This chapter contains 2D and 3D contact problems and Mechanica's results. In a contact analysis, Mechanica calculates deformations, stresses, and strains on your model in response to specified loads and subject to specified constraints. Mechanica also automatically calculates all predefined measures. This list of measures differs based on the analysis type. This chapter contains the following contact problems: Topic mvsc001: 2D Contact-Hertz Contact mvsc002: 3D Contact-Hertz Contact mvsc001: 2D Contact-Hertz Contact Analysis Type: 2D Contact Model Type: Plane Strain Comparison: Theory Reference: Roark, R.J. and Young, W. Formula for Stress and Strain. NY; McGraw-Hill Co. 1982. p. 517. Description: A half model of two cylinders of unit depth in contact. Modeled using 2D contact. Determine the maximum stress and contact area. 1249 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: 2D solid Units: IPS Dimensions: R1: 1 R2: 1 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 1e6 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: 1250 fixed in all but y on vertical edges; fixed in all but x on Structural and Thermal Simulation bottom edge Loads: -1000 on top element edges (symmetry): Total Load=-2000 Comparison of Results Data Theory Structure % Difference Contact Area 0.0481 0.0483 0.42% Maximum Stress (m=contact_max_press) 26450 26545.44 0.36% Convergence %: 1.1 % on Contact Area and Contact Pressure Max P: 9 No. Equations: 865 mvsc002: 3D Contact-Hertz Contact Analysis Type: 3D Contact Model Type: 3D Comparison: Theory Reference: Roark, R.J. and Young, W. Formula for Stress and Strain. NY; McGraw-Hill Co. 1982. p. 517. Description: A quarter section of two hemispheres in contact. Determine the maximum stress and contact area. 1251 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: 2D solid Units: IPS Dimensions: R1: 2 R2: 3 Material Properties: Mass Density: 1 Cost Per Unit Mass: 1 Young's Modulus: 1e7 Poisson's Ratio: 0.3 Thermal Expansion: 1 Conductivity: 1 Constraints: fixed in all but y on xz face; fixed in all but x on yz face; fixed on bottom edge 1252 Structural and Thermal Simulation Loads: -25000 on top element faces (symmetry): Total Load=-100000 Comparison of Results Data Theory Structure % Difference Contact Area 0.0507 0.0482 4.9% Maximum Stress (m=contact_max_pres) 740285 753247.2 1.75% Convergence %: 0.9 % on Contact Area and Contact Pressure Max P: 7 No. Equations: 1391 1253 Structural and Thermal Simulation - Help Topic Collection Large Deformation Analysis Problem This chapter contains a large deformation analysis problem. In a large deformation analysis, Structure calculates the deformations, stresses, and strains that occur as a result of a load that produces a large deformation where the model's deformed configuration differs appreciably from its original configuration. In addition to a set of standard results, Structure also automatically calculates all predefined measures. This list of measures differs based on the analysis type. mvsd001: Hinged Right-Angle Frame Under a Single Nonconservative Force Analysis Type: Large Deformation Analysis Model Type: 3D Reference: Argyris, J.H., and Symeonidis, Sp., "Nonlinear Finite Element Analysis of Elastic Systems Under Nonconservative Loading Natural Formulation Part I. Quasistatic Problems," Computer Methods in Applied Mechanics and Engineering, 26 (1981), pp75–123. Description: A hinged, right-angle frame is constrained in translation at the upper right and lower left corners. It is subjected to a nonconservative downward load 96 cm from the upper right constraint. The load is simulated using a pressure load applied over a small area. Calculate the lateral and vertical displacements at the load application point. 1254 Structural and Thermal Simulation Specifications Element Type: solid (56) Units: cm, N Dimensions: length: 120 width: 3 depth: 2 Material Properties: Mass Density: 0 Cost Per Unit Mass: 0 Young's Modulus: 7.2e6 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 1255 Structural and Thermal Simulation - Help Topic Collection Constraints: at upper right and lower left corners: fixed in translation Loads: Location/Magnitude: Distribution: Spatial Variation: uniform vertical 15 kN over 3 cm2 applied at 96 cm from the upper right constraint pressure Comparison of Results Data Displacements at the load application point Lateral Displacement (x) Theory 3.5 Structure 3.79 % Difference 8.3% Vertical Displacement (y) 17.0 17.39 2.3% Convergence: SPA RMS Stress Error Estimates: 0.4 % Max P: 7 No. Equations: 4152 1256 Structural and Thermal Simulation Prestress Modal Analysis Problem This chapter contains a prestress modal problem. In a prestress modal analysis, Mechanica calculates the natural frequencies and mode shapes of your model. Mechanica also automatically calculates all predefined measures. This list of measures differs based on the analysis type. mvsp001: Prestress Modal Analysis of a Stretched Circular Membrane Analysis Type: Prestress Modal Model Type: 3D Comparison: ANSYS Reference: Timoshenko, S., and Young, D.H. Vibration Problems in Engineering, 3rd Edition. D. Van Nostrand Co., Inc., New York, 1955. Description: Determine the first three radially symmetric, out of plane, natural frequencies of a circular membrane. Use stiffness calculated from static analysis where membrane is loaded radially. Edges are simply supported. 1257 Structural and Thermal Simulation - Help Topic Collection Specifications Element Type: plate Units: IPS Dimensions: radius: 15 thickness: 0.01 Material Properties: Mass Density: 0.00073 Cost Per Unit Mass: 0 Young's Modulus: 3e7 Poisson's Ratio: 0.3 Thermal Expansion: 0 Conductivity: 0 Constraints: edge simply supported Loads: radial load of 100 lb/in 1258 Structural and Thermal Simulation Comparison of Results Data Theory ANSYS % Difference Structure % Difference Mode 1 94.406 94.471 0.07% 94.437 0.03% Mode 6 216.77 217.38 0.28% 217.07 0.14% Mode 15 339.85 342.98 0.92% 341.297 0.45% Convergence %: 0.3 % on Frequency Max P: 9 No. Equations: 978 Note: Results are only for radially symmetric modes—modes 1, 6, and 15 of the solution. These are out-of-plane modes, in other words; they appear in the profile view. 1259 Structural and Thermal Simulation - Help Topic Collection Optimization Analysis Problem This chapter contains an optimization problem. In an optimization of a static analysis, Structure finds the optimal values of the parameters in your model to achieve a specific design goal (for example, to minimize mass). mvoo001: Five-Bar Configuration Problem Analysis Type: Static Model Type: 3D Reference: Imai, Kanji. Configuration Optimization of Trusses by the Multiplier Method. LA: University of California, UCLA-ENG-7842. Description: A five-bar truss has the following conditions for optimization: the cross-section area for bars AB, CD, BE, and CE are kept the same; bar BC has an independent cross-section area, and the load applied on point E is 20000 psi. Find the minimum weight of the truss with the maximum tensile stress in the model under 20000 psi. 1260 Structural and Thermal Simulation Specifications Element Type: beam (5) Units: IPS Dimensions: length A-B, C-D: 240 length B-C: 480 length B-E, C-E: 339.41 Beam Properties: Area: 0.1 IYY: 0 Shear FY: 0 CY: 1 J: 0 IZZ: 0 Shear FZ: 0 CZ: 1 1261 Structural and Thermal Simulation - Help Topic Collection Material Properties: Mass Density: 0.1 Cost Per Unit Mass: 0 Young's Modulus: 1.0e7 Poisson's Ratio: 0 Thermal Expansion: 0 Conductivity: 0 Constraints: constraint1 Location all beams points A and D Degrees of Freedom fixed in RotX, RotY, and RotZ fixed in all DOF Loads: load1 Location/Magnitude point E: -20000 Distribution uniform Spatial Variation N/A Design Variables: x Location: Min to Max: Current: length of bar BC 480 to about 0 480 y length of bars AB and CD 240 to about 0 240 dvar_1 placed on bars AB and CD 0.1 to 10 0.1 dvar_2 placed on bar BC 0.1 to 10 0.1 dvar_4 placed on bar BE and CE 0.1 to 10 0.1 1262 Structural and Thermal Simulation Optimization Parameters Optimization Goal: Minimize the total mass of the truss Limits: measure8 Quantity tensile stress over bar BC Magnitude < 20000 measure9 tensile stress over bar CE < 20000 measure10 tensile stress over bar CD < 20000 measure18 tensile stress over bar BC > -20000 measure19 tensile stress over bar CE > -20000 measure20 tensile stress over bar CD > -20000 Comparison of Results Data Theory Goal — minimize total mass 63.5 Structure 63.59 % Difference 0.1% Convergence %: 1% 1263 Structural and Thermal Simulation - Help Topic Collection Glossary for Mechanica This Glossary contains brief definitions of some mechanical engineering terms and Mechanica terms. For more complete definitions of the mechanical engineering terms, consult a mechanical engineering textbook. One or two bold letters in parentheses indicate that the definition applies only to those Mechanica products. The possible letters are S (Structure) or T (Thermal). Otherwise, the definition applies to all three Mechanica products. A analysis An examination of your model through which Mechanica determines how the model behaves under specified conditions. You run an analysis as part of a standard or other design study. Structure calculates your model's response to a set of loads and constraints. See also these analysis types: buckling, contact, dynamic frequency response, dynamic random response, dynamic shock response, dynamic time response, modal, prestress modal, prestress static, and static. Thermal calculates your model's response to a set of heat loads that are subject to specified prescribed temperatures and/or convection conditions. See also steady-state thermal. animation A dynamic display of mode shapes, static displacement results, a variety of fringed results, and shape changes for a sensitivity or optimization study in both products. applied flux (T) A prescribed rate at which heat energy is applied. 1264 Structural and Thermal Simulation associativity How any entity (such as geometry, load, boundary condition) in Mechanica relates to any other entity. If one entity is related to a second entity, the definition of the first entity depends on the definition of the second. For instance, if a load is associated with a point and that point moves, the load also moves. AutoGEM (Automatic Geometric Element Modeling) Mechanica's automated process for generating geometric elements on a model. AutoGEM generates elements that comply with all element creation rules and that provide accurate results when Mechanica analyzes your model. axisymmetric model A two-dimensional model for which the geometry, loads, deformations, prescribed temperatures, and convection conditions are symmetric about an axis of rotation. For example, you can use an axisymmetric model type for a cylindrical or spherical structure, such as a storage tank. B beam See beam element, flexible beam. beam element A one-dimensional entity used to represent part or all of a structural component that has a length much greater than its other two dimensions. The beam element axis lies on a curve or edge. In Structure, you describe the cross section by a set of section properties and an orientation. See also CY, CZ, IYY, IZZ, J, orientation, shear FY and FZ, and theta. bearing load (S) A load that approximates the pressure applied to a 3D surface or 2D circle by a rigid pin or axle passing through a hole. 1265 Structural and Thermal Simulation - Help Topic Collection boundary condition (T) See convection condition and prescribed temperature. boundary condition set (T) A grouping of convection conditions and/or prescribed temperatures placed on a single model. You typically include a boundary condition set as part of an analysis. boundary edge An edge associated with only one shell or solid, unless the edge is associated with a solid and a shell coincident with a face of that solid. See also boundary face. boundary face A face that belongs to only one solid element. See also boundary edge. buckling analysis (S) An analysis that calculates the critical magnitudes of load at which a structure will buckle, and the model's stresses, strains, and deformations in response to loads and constraints that do not vary in time. buckling load factor (S) A quantity obtained by running a buckling analysis in Structure. The buckling load factor multiplied by the applied load yields the buckling load. bulk temperature (T) In convective heat transfer through a surface, the temperature of the fluid far from the surface. 1266 Structural and Thermal Simulation C C1 continuous curve or surface A mathematical description of a curve or surface. A curve or surface is C1 continuous if both the direction and the magnitude of its first derivatives vary continuously everywhere on the curve or surface. C2 continuous curve or surface A mathematical description of a curve or surface. A curve or surface is C2 continuous if both the direction and the magnitude of its second derivatives vary continuously everywhere on the curve or surface. centrifugal load (S) An inertial body load that results from rotation about an axis, directed radially out from the axis. check button A square button on a dialog box. From a group of check buttons, you can select one or more. com_x, com_y, com_z (S) The location of the center of mass in relation to the WCS origin. conductivity (T) The physical property of a material that, for a given temperature gradient, governs the rate at which heat energy is transferred within the material. 1267 Structural and Thermal Simulation - Help Topic Collection constraint (S) An external limit on the movement of a structure or part of a structure. You can constrain your model in any of the six degrees of freedomtranslation or rotation about any of the three coordinate directions. constraint set (S) A grouping of constraints placed on a single model. You typically include a constraint set as part of an analysis. contact analysis (S) A nonlinear analysis in which Structure calculates the contact area at each contact region in a model, and the model's stresses, strains, and deformations in response to loads and constraints that do not vary in time. contour plot A type of result display that superimposes a set of curves on the model. Each curve has a color that represents a constant value of a specified scalar quantity. You also have the option of labeling contour plots for black-andwhite printing. Examples of scalar quantities include stress, displacement, temperature, or flux components. convection condition (T) A boundary condition you can specify on the convective heat exchange between a moving fluid and geometric and/or element entities within your model. convergence The method Mechanica uses to find a solution to an analysis, based on your requirements and restrictions. There are two main convergence methods in Mechanica: multi-pass adaptive and single-pass adaptive. 1268 Structural and Thermal Simulation coordinate system A generic term for a system of coordinates enabling you to define precise locations of entities. Mechanica uses a default world coordinate system. In addition, you can create three types of user coordinate systemsCartesian, cylindrical, and spherical. You can specify orientation of a beam or spring by defining its local coordinate system. See also local coordinate system, user coordinate system, view coordinate system, and world coordinate system. critical damping (S) Amount of damping below which oscillation occurs. See also damping coefficient. current body The body that is active and available for modification. You are always using the current body. current directory The directory from which you started Mechanica. current model The model you currently have open on the screen. Mechanica allows you to open only one model at a time. See also model. CY (S) The distance off a beam's neutral axis in the local Y direction at which you direct Structure to report bending stresses. 1269 Structural and Thermal Simulation - Help Topic Collection cyclic symmetry A type of constraint that you create by making cuts in a model at two symmetric surfaces. Subsequent analyses can be done on the symmetric surfaces only, which can significantly reduce the analysis time. CZ (S) The distance off a beam's neutral axis in the local Z direction at which you direct Structure to report bending stresses. D damping coefficient (S) The percentage of critical damping of a mode in a dynamic frequency response, random response, or time response analysis. A damping coefficient of 100% means the model is critically damped and does not vibrate freely. A damping coefficient of 1% means the amplitude decays by about 6% over a period of oscillation. See also critical damping. degrees of freedom A means of expressing the potential motion of a mechanical system. design study An examination of your model using one or more analyses you previously defined (standard study). A design study may also use an analysis to examine alternatives to your design (optimization and sensitivity studies). See also global sensitivity study, local sensitivity study, optimization study, and standard study. dialog box A separate window, invoked by a command, in which you enter values and other information. 1270 Structural and Thermal Simulation dimension parameter A range of values you associate with a Pro/ENGINEER dimension. As the parameter value changes during a shape review, shape animation, sensitivity study, or optimization study, Mechanica also regenerates the associated dimension in both the Pro/ENGINEER and Mechanica versions of the model. You use dimension parameters to change your model's shape. displacement (S) The movement of a point on the model, measured as the change in position relative to the point's location on the undeformed model. Displacements are calculated by default during an engine run. dynamic frequency response analysis (S) An analysis that calculates the amplitude and phase of displacements, velocities, accelerations, and stresses in your model in response to a load oscillating at different frequencies. dynamic random response analysis (S) An analysis that calculates the power spectral densities and RMS values of displacements, velocities, accelerations, and stresses in your model in response to a load of specified power spectral density. dynamic shock response analysis (S) An analysis that calculates maximum values of displacements and stresses in your model in response to a base excitation with a specified response spectrum. dynamic time response analysis (S) An analysis that calculates displacements, velocities, accelerations, and stresses in your model at different times in response to a time-varying load. 1271 Structural and Thermal Simulation - Help Topic Collection E element An entity based on your model's geometry that Mechanica uses to analyze your model. Types of elements include beams, shells, solids, 2D shells, 2D solids, and 2D plates. Structure also has mass and spring elements. You create elements by using AutoGEM, Mechanica's automatic element generation technology. AutoGEM creates elements for your model at the start of every analysis. You can also manually start AutoGEM during your modeling session to evaluate and refine your mesh. See also AutoGEM or geometric element modeling. Encapsulated PostScript A PostScript file you can include in another PostScript file. Encapsulated PostScript files are used to place illustrations in a PostScript document. You cannot print out an Encapsulated PostScript file on its own. See also PostScript file. energy norm (T) A scalar quantity that is proportional to the integral over the element of the flux squared. It is analogous to element strain energy in a static structural analysis. You can create measures for this and use it for a convergence quantity. enforced displacement (S) A known displacement you prescribe on part of your model when you create a constraint. entity A general term for anything in a model, including points, curves, springs, beams, and so forth. There are also entities specific to each productfor example, loads and constraints in Structure and convection conditions and heat loads in Thermal. 1272 Structural and Thermal Simulation entry box A box on a dialog box in which you enter data. You make an entry box active by moving your mouse cursor over the box and pressing the left mouse button. extensional stiffness (S) A spring stiffness constant that equals the ratio of spring force to displacement along a principal coordinate axis. F film coefficient (T) In convective heat transfer through a surface, the constant of proportionality between the flux through the surface and the difference between the surface temperature and the bulk temperature. flux (T) The rate at which heat energy is transferred per unit area. frequency response analysis (S) See dynamic frequency response analysis. fringe plot A type of result display that superimposes a set of colored regions on the model. Each color represents a different range of values of a specified scalar quantity, such as stress, displacement, temperature, or flux. 1273 Structural and Thermal Simulation - Help Topic Collection G G1 continuous curve or surface A mathematical description of a curve or surface. A curve or surface is G1 continuous if the direction, but not necessarily the magnitude, of its first derivatives varies smoothly everywhere on the curve or surface. G2 continuous curve or surface A mathematical description of a curve or surface. A curve or surface is G2 continuous if the direction, but not necessarily the magnitude, of its second derivatives varies smoothly everywhere on the curve or surface. GEA See geometric element analysis. GEM See geometric element modeling. GEO See geometric element optimization. geometric element analysis (GEA) Mechanica's technology for analyzing a model by analyzing its geometric elements to the polynomial order required to achieve the level of accuracy you specify. geometric element modeling (GEM) Mechanica's technique for defining a model for analysis by breaking it up into elements that you associate directly with the geometry. See also element. 1274 Structural and Thermal Simulation geometric element optimization (GEO) A process that helps you determine the best balance between design constraints and performance by automatically varying design parameters that are associated with a geometric element model. See also optimization. global sensitivity study A design study in which Mechanica calculates the changes in your model's measures when you vary a parameter over a specified range. Mechanica does this by calculating measure values at regular intervals in a parameter's range. You can vary more than one parameter simultaneously. See local sensitivity study, optimization study, and standard study. gravity load (S) A body load that represents the effect of a uniform gravitational field or the inertial load of constant acceleration. H heat capacity (T) A property that indicates the ability of a material to absorb heat from the external surroundings. It represents the amount of energy required to produce a unit temperature rise. heat load (T) A thermal load you can place on specific locations on your model to study the effects of internal heat generation or applied flux. If you specify a positive heat load, the load is adding heat to the model, making the load a heat source. If you specify a negative heat load, the load is removing heat from the model, making the load a heat sink. You can group heat loads into load sets. See also heat sink and heat source. heat sink (T) A prescribed rate of heat energy lost. See also heat load. 1275 Structural and Thermal Simulation - Help Topic Collection heat source (T) A prescribed rate of heat energy generated. See also heat load. HPGL Hewlett-Packard Graphics Language, a page description format you can use to print on a plotter or printer that supports HPGL. I inertia (Iy, Iz) (S) Factors that you specify for the second moment of area for a beam element. Along with Young's modulus, these properties describe stiffness in bending about a beam's principal Y and Z axes. isotropic Describes a material with an infinite number of planes of material symmetry, making the properties equal in all directions. You enter a single value for each property. You can assign isotropic materials to any element type. IYY (S) A beam cross section's second moment of area describing stiffness in bending about the local Y axis. IZZ (S) A beam cross section's second moment of area describing stiffness in bending about the local Z axis. 1276 Structural and Thermal Simulation J J (S) A beam cross section's effective second polar moment of area describing stiffness in torsion. For circular cross sections, the effective second polar moment of area is equal to the actual second polar moment of area. L Large Deformation Analysis An option you can select to compute large deformation results for static structural analyses only, using nonlinear equations. This is only available for 3D, 2D plane strain, and 2D plane stress model types. limit A value or range of values for a specified measure that Mechanica must respect during an optimization study. list box A list of items on a dialog box with a scroll bar to its right. load (S) A force you place on your model. You can specify the direction and magnitude of the force. See also bearing load, centrifugal load, gravity load, pressure load, and temperature load load set A grouping of structural loads or heat loads placed on a single model. You can include load sets in most analysis types. Mechanica calculates results separately for each load set, unless you use the Sum Sets option for a dynamic analysis. 1277 Structural and Thermal Simulation - Help Topic Collection local sensitivity study A design study in which Mechanica calculates the sensitivity of your model's measures to slight changes in one or more parameters. Mechanica calculates the slope of the sensitivity curve between two sample points. See also global sensitivity study, optimization study, and standard study. M mass element (S) An element that represents a concentrated mass and concentrated moment of inertia at a particular point of a model. mass properties Properties calculated from a model's geometry and material properties. The mass properties for the full model are included in the summary file when you run a design study with certain types of analyses. material damping A material property that allows you to model the dissipation of energy, caused by friction, heat exchange, or deformation, that occurs during a contact event. material orientation The principal material directions, relative to the current coordinate system, associated with the surfaces, volumes, shells, solids, 2D solids, or 2D plates in your model. You can specify both the coordinate system axis with which each principal material direction is aligned and an angle of rotation for those directions. See also orientation. 1278 Structural and Thermal Simulation material properties Properties of the material you assign to geometry or elements. The following table indicates the material properties for each product: Material Property Coefficient of Thermal Expansion Conductivity Cost per Unit Mass Mass Density Poisson's Ratio Shear Modulus Young's Modulus S T S, T S, T S S S Product See also isotropic, orthotropic, and transversely isotropic. material set A set of material properties. Material sets can reside in a material library and can be assigned to one or more entities in your model. maximum magnitude principal stress (S) The principal stress value having the maximum magnitude. For example, if the maximum principal stress is 100 but the minimum principal stress is 200, the principal stress with the greatest magnitude is the minimum principal stress (200). maximum principal stress (S) The most positive principal stress in the model. 1279 Structural and Thermal Simulation - Help Topic Collection maximum shear stress The maximum shear stress (also known as Tresca stress), is defined as one half of the largest difference in the principal stresses at a given point. MCAD Mechanical computer-aided design, a type of software you can use to draw a mechanical model design. Pro/ENGINEER is an example of an MCAD program. measure A scalar quantity of interest that Mechanica calculates in a design study. You can set up measures to monitor specific aspects of your model's performance. For instance, you might want to know the stress tangent to a fillet for the later calculation of fatigue. You can use measures as convergence criteria for an analysis or for an optimization study goal or limit. You also use measures to measure sensitivity to parameter changes in a local or global sensitivity design study. During a design study, Mechanica calculates results for the measures that are valid for each analysis in the study. For example, a stress measure is calculated for a static analysis but not for a modal analysis. menu A list of commands you can execute. menu item A command or submenu listed on a menu. message box A box Mechanica displays that contains a message or a question. 1280 Structural and Thermal Simulation minimum principal stress (S) The least positive principal stress in the model. modal analysis (S) An analysis in which Structure calculates the natural frequencies and mode shapes of your model. mode tracking (S) During an optimization that includes a modal analysis, you can direct the Structure engine to follow a particular mode through the optimization, even if that mode's frequency becomes greater than or less than a neighboring mode's frequency. model Your representation on the computer of a structure or object. You can associate analyses and design studies with a model. modeling The process of simplifying and abstracting a structure, object, or physical system so that it can be represented mathematically and studied with the aid of a computer. Model Tree window A window that graphically shows features of a model, including simulation features (datum points, coordinate systems, datum curves, surface regions, and volume regions). 1281 Structural and Thermal Simulation - Help Topic Collection model type The dimensional treatment you want Mechanica to apply for your model. The available model types are 3D, 2D plane strain, 2D plane stress, or 2D axisymmetric. modified Mohr theory A theory used for predicting the failure of brittle materials. It is a variant of the Coulomb-Mohr theory modified to better predict fracture in brittle materials. moment of inertia (S) An inertial constant that equals the ratio of applied moment to the resulting angular acceleration about an axis. multi-pass adaptive convergence The point during a run at which the results for the last calculation for an analysis differ from the results for the preceding calculation by less than a specified percentage. The quantities Mechanica uses to make this comparison depend on the convergence option you select when defining the analysis. Mechanica increases the polynomial order along each edge of the model until either convergence or the maximum polynomial order has been reached. See also polynomial order. N net heat flux (T) A measure that Thermal calculates by finding the total amount of heat that flows through one or more of the boundaries of one or more elements. For example, in 3D models, Thermal can calculate the net heat flux for the endpoints of beams, the edges of shells, the faces of solids, or a combination of these. 1282 Structural and Thermal Simulation O optimization study A design study in which Mechanica adjusts one or more parameters to best achieve a specified goal or to test feasibility of a design while respecting specified limits. See also global sensitivity study, local sensitivity study, and standard study. orientation (S) A property of beams and two-point springs. Orientation is a vector with three WCS components. This vector specifies the beam's or spring's local Z axis relative to the WCS. See also material orientation. orthotropic Describes a material with symmetry relative to three mutually perpendicular planes. You can assign orthotropic properties to surfaces and parts. P parameter space The representative space, internal to Mechanica's code, in which Mechanica represents geometric entities. Mechanica simultaneously represents all geometry by two methodsthe actual 2D or 3D representation of your model, and the 1D, 2D, or 3D parametric representation that Mechanica uses to manipulate geometric entities. Mechanica performs many operations on geometric entities in parameter space and then maps the entities back to 3D space. As a result, the appearance of an entity may differ significantly from its parametric representation. phase (S) The angle by which an output quantity is out of phase with the force that prompted the response. A negative angle means that the output quantity lags behind the force. 1283 Structural and Thermal Simulation - Help Topic Collection p-level The highest polynomial order to which Mechanica performs calculations on a given edge during a run of a design study. See also polynomial order. plotting grid The locations at which Mechanica calculates values for displacement, stress, temperature, flux, and other quantities. Mechanica places a grid across each element and calculates a value at each location where two grid lines cross, or where a grid line intersects an element edge. You can determine the size of the grid when you define an analysis by specifying how many intervals along each element edge Mechanica uses to create the grid. The grid size affects the level of detail of the results. Poisson's ratio (S) The ratio of lateral contraction to longitudinal extension when a material is under tension. You specify Poisson's ratio when you define material properties. polynomial order When Mechanica runs a design study, it calculates the value of specified quantities at successively higher polynomial orders for each edge until it reaches convergence or the maximum polynomial order. Mechanica uses functions that may range from linear to a 9th order polynomial, although you can specify a subset of that range when you define an analysis. See also convergence and p-level. PostScript file A file written in the PostScript language, a page description language. You can create color or black-and-white files in PostScript format from Mechanica to print out on PostScript printers. 1284 Structural and Thermal Simulation p-pass A single analysis calculation by the Structure engine with each element edge set to a particular polynomial order. After each p-pass, Mechanica updates the polynomial orders of the edges for the next p-pass. The process continues until either convergence or the maximum polynomial order is reached. prescribed temperature (T) A temperature boundary condition that you specify for a geometric or model entity. Thermal determines the temperature at every location on your model for which you have not prescribed a temperature. You can add prescribed temperatures to new or existing constraint sets. pressure load (S) A load that acts normal to a surface and has units of force per unit area. prestress modal analysis (S) An analysis that calculates natural frequencies and modes of a prestressed model. The stress stiffness is calculated using stresses from a previous static analysis, then added to the elastic stiffness to create a combined stiffness. The combined stiffness is then used in place of the elastic stiffness for the modal analysis. prestress static analysis (S) An analysis that calculates deformations, stresses, and strains of a prestressed model. The stress stiffness is calculated using stresses from a previous static analysis, then added to the elastic stiffness to create a combined stiffness. The combined stiffness is then used in place of the elastic stiffness for the static analysis. 1285 Structural and Thermal Simulation - Help Topic Collection Mechanica A family of design analysis products that enable you to simulate and optimize the structural and thermal performance of your designs before you build prototypes. The two main Mechanica products are as follows: • • Structure a structural design analysis tool Thermal a thermal design analysis tool These two products are integrated, so that you can access either product from inside a single user interface. Your installation may also include the optional Vibration module, a vibration analysis tool integrated with Structure. prompt A request for a single input that appears on the command line. properties See CY, CZ, IYY, IZZ, J, mass properties, material properties, orientation, shear FY and FZ, shell properties, theta. push button A button on a dialog box that enables you to select an action that Mechanica performs. Typical push buttons include OK or Cancel. Q Q (T) The heat rate you apply to selected entities when you create a heat load. 1286 Structural and Thermal Simulation R radio button A diamond-shaped or circular button on a dialog box. From a group of radio buttons, you can select only one. random response analysis (S) See dynamic random response analysis. reaction forces (S) The forces present at constrained edges or points. See also resultant. resultant (S) You can define a resultant force or resultant moment measure. Structure calculates the resultant force measure by integrating the total traction forces acting on one or more of the boundaries of one or more elements. Structure calculates the resultant moment measure by integrating the product of a moment arm and the traction forces acting on one or more of the boundaries of one or more elements. In 3D models, Structure can calculate a resultant measure for the endpoints of beams, the edges of shells, the faces of solids, or a combination of these. The value of a resultant measure is equal to the sum of the resultants for all of the entities selected. result window A single display of a design study result. A result window contains one quantity, such as stress or displacement, defined over a location, such as an edge or the entire model, in a specific graphic display, such as a graph or fringe plot. 1287 Structural and Thermal Simulation - Help Topic Collection right-hand rule A method for determining the direction of the positive Z axis relative to the positive X and positive Y axes. If your right hand is in front of you with the palm up, your thumb pointing to the right represents the positive X axis, and your index finger pointing straight ahead represents the positive Y axis. If you then bend your middle finger up by 90 , it represents the direction of the positive Z axis. rigid body modes (S) Modes that have no strain associated with them. rotation (S) The local change in orientation at a location on the model relative to the undeformed model. run During a run, the engine performs the calculations needed to provide results for a specified design study. S sensitivity study A "what if" design study where Mechanica uses parameters to study variations in the design of your model to help you find the best design. See also global sensitivity study and local sensitivity study. shape history An animation sequence showing the changing shape of your model during each step of an optimization or global sensitivity design study. You also use a shape history result window definition to save the optimized version of a model. 1288 Structural and Thermal Simulation shear FY and FZ (S) The ratio of a beam's effective "shear area" to its true cross-sectional area for shear in the Y direction (for shear FY) or in the Z direction (for shear FZ). Structure uses these factors to improve the accuracy of calculations involving beams. shell element A three- or four-sided entity used to represent part or all of a structural component that has a thickness much smaller than its other two dimensions. Mechanica displays the shell element midsurface. shell properties The properties you assign to a shell depend on its type. For a homogeneous shell, which consists of a single material whose properties do not vary through the shell's thickness, you assign a thickness. For a laminated shell, which consists of one or more materials whose properties may vary through the shell's thickness, you specify laminate stiffness properties. shock response analysis (S) See dynamic shock response analysis. simulation features Features that you can create in the Mechanica environment that allow you to focus on a portion of your model that the feature will simulate. Simulation features are only visible in the Mechanica environment, and include datum points, coordinate systems, datum curves, surface regions, and volume regions. single-pass adaptive convergence A method Mechanica uses to find a solution to your analysis. Mechanica runs a first pass with the polynomial order set to 3, estimates stress errors, raises the polynomial order of each element to a higher level based on the 1289 Structural and Thermal Simulation - Help Topic Collection magnitude of the local stress errors, and then carries out a second solution using the updated polynomial orders. The results of this second solution are output as the final results. singularity A region of the model where the results are theoretically infinite for any physical quantity, such as displacement, stress, temperature, or heat flux. Singularities usually result from point loads, point constraints, and reentrant corners. solid element A cubical, tetrahedral, or wedge-shaped entity you use in Mechanica to represent a part or all of a three-dimensional structural component. spatial variation The process by which Mechanica spatially varies a Structure load or a Thermal heat load. You can direct Mechanica to vary a load or heat load linearly, quadratically, or cubically along an edge, curve, face, or surface. specific heat (T) The heat capacity per unit mass. See heat capacity. spline A continuous curve that is typically composed of several polynomial segments. spring (S) An idealization that represents an elastic spring connection between two points or an elastic spring connection to ground at a single point. 1290 Structural and Thermal Simulation standard study A study in which Mechanica calculates results for one or more analyses. You can specify different parameter settings for the analysis. See design study, global sensitivity study, local sensitivity study, and optimization study. static analysis (S) An analysis in which Structure calculates a model's stresses, strains, and deformations in response to loads that do not vary in time, where the model is also subject to constraints. steady-state thermal analysis (T) An analysis in which Thermal calculates your model's response to a set of specified heat loads, subject to any convection conditions and/or prescribed temperatures. This is the only type of analysis available in Thermal. T temperature load (S) A body load due to a temperature change over the model. A temperature change causes local expansion or contraction of the model. You can cause the model to resist expansion or contraction by using constraints. The two types of temperature load are MEC/T and global. tensile/compressive/shear failure stress The maximum stress a body can endure under a tensile/compressive/shear load before failure occurs. thermal expansion coefficient (S) A material constant that equals the ratio of strain to temperature change in degrees. 1291 Structural and Thermal Simulation - Help Topic Collection theta ( ) (S) A property of beams and two-point springs. Theta is the angle between the principal Z axis and the local Z axis. The default local Y axis lies in the plane of the beam unless theta is nonzero. time response analysis (S) See dynamic time response analysis. torsional stiffness (S) A spring stiffness constant that equals the ratio of spring moment to rotation about a principal coordinate axis. transient thermal analysis (T) An analysis in which Thermal calculates temperatures and heat fluxes in your model at different times in response to specified heat loads and subject to specified prescribed temperatures and/or convection conditions. transversely isotropic Describes a material with rotational symmetry about an axis that you can assign to surfaces and parts. The properties are equal for all directions in one plane, the plane of isotropy. You enter two values for each property, one for the plane of isotropy, and one for the remaining principal material direction. true angle The actual, absolute 3-D angle (as opposed to a projected angle). Tsai-Wu failure criterion A general multiaxial failure theory used to predict failure of anisotropic materials. It is named after Stephen Tsai and Edward Wu, who proposed the theory. 1292 Structural and Thermal Simulation Tsai-Wu normalized interaction term A mathematical term used in the calculation of the Tsai-Wu failure criterion. It represents the interaction between the normal stresses in material directions 1 and 2. See also material orientation and transversely isotropic. 2D axisymmetric model See axisymmetric model. 2D plate element A three- or four-sided element that represents a plate in a 2D plane stress model. 2D plane stress model A two-dimensional model you can use when modeling a thin, flat plate. All elements must lie in the WCS Z=0 plane. You can only create 2D plate elements for a 2D plate model. 2D plane strain model A two-dimensional model representing a cross section of a structure that is very long in the dimension perpendicular to the cross section. In plane strain models, all out-of-plane components of load and strain must be zero, and loading cannot vary in the out-of-plane direction. For example, in Structure, you can use a plane strain model type for applications such as long pipes, dams, and retaining walls. In Thermal, you use 2D plane strain models for structures where the heat flow in one direction is negligiblethat is, the temperature varies in two directions but not the third. For example, you could use this model type for modeling a long pipe. 1293 Structural and Thermal Simulation - Help Topic Collection 2D shell element A one-dimensional entity that represents a shell element in a 2D plane strain or 2D axisymmetric model. 2D solid element A three- or four-sided element that represents a 2D plane strain or 2D axisymmetric model. U UCS See user coordinate system. user coordinate system A Cartesian, cylindrical, or spherical coordinate system you define, which is also referred to as a UCS. See also coordinate system, local coordinate system, view coordinate system, and world coordinate system. V VCS See view coordinate system. Vibration An optional vibration analysis module integrated with Structure. view coordinate system The system Mechanica uses to define the view window. The origin is always at the center of your screen with the positive X axis horizontal and to the right, the positive Y axis vertical and up, and the positive Z axis perpendicular to the other axes and pointed at you as you sit at the computer. See also coordinate system, local coordinate system, user coordinate system, and world coordinate system. 1294 Structural and Thermal Simulation This coordinate system is a reference point for view changes. When you rotate, translate, or zoom your model, you are in effect repositioning the VCS in relation to your model. volume A set of associated surfaces that visually represents an entity with volume. A volume must be closed, but can have interior voids. von Mises stress (S) An equivalent stress that is a combination of all stress components. The von Mises yielding criterion states that a material reaches its elastic limit if the von Mises stress is equal to the material's yield stress in simple tension. W WCS See world coordinate system. work area The largest window of the Mechanica screen, where you create and modify models, and review results. By default, the work area is below the command area and tools button area and to the left of the design menu area. world coordinate system The default coordinate system, also referred to as the WCS, in Mechanica. You use this coordinate system when you create your model. See also coordinate system, local coordinate system, user coordinate system, and view coordinate system. 1295 Structural and Thermal Simulation - Help Topic Collection Y Young's modulus (S) The ratio of stress to strain for a specific material, describing its stiffness. You specify Young's modulus when you define material properties. yield stress The value of stress at or above which a material no longer exhibits linear elastic behavior. 1296 Index 2D models 2D axisymmetric model type Structure ............................. 134 Thermal ............................... 137 2D axisymmetric model type ..... 134 2D plain strain model type Structure ............................. 133 Thermal ............................... 136 2D plain strain model type ........ 136 2D plane stress model type Structure ............................. 133 Thermal ............................... 136 2D plane stress model type ....... 136 defining .................................. 139 elements ................................ 574 preparing.................................. 45 2D models ................................... 45 3D model type .................... 132, 135 acceleration measure defining .................................. 541 overview................................. 524 acceleration measure .................. 524 acceleration results ..................... 869 advanced springs ........................ 237 analysis creating .................................. 749 dynamic frequency ................... 722 dynamic random ...................... 723 dynamic shock ......................... 724 dynamic time........................... 720 FEM modal .................................. 738 overview .............................. 737 structural and thermal............ 738 FEM ........................................ 737 modal ..................................... 670 modifying ................................ 807 planning for optimization .............46 prestress modal ....................... 671 prestress static ........................ 664 selecting measures ................... 516 static ...................................... 662 structural ................................ 660 thermal................................... 704 types ...................................... 659 vibration ................................. 719 1297 Structural and Thermal Simulation - Help Topic Collection workflow................................. 747 analysis..................................... 658 animation of results .................... 858 annotating result windows .... 834, 902 ANSYS ...................................... 745 approximated elements ............... 636 assemblies and midsurface compression ..... 219 and optimized parts ................... 47 automatic midsurface connections .......................................... 161 connected and unconnected parts .......................................... 102 fasteners ................................ 168 gaps ...................................... 219 guidelines ................................. 35 modeling entities and idealizations94 rigid connections...................... 166 welds ..................................... 161 assemblies................................... 35 AutoGEM AutoGEM dialog box ................. 569 controlling the mesh Datum options ......................... 588 file menu................................. 571 geometry tolerances absolute and relative.............. 590 setting ................................. 589 geometry tolerances ................. 588 info menu................................ 571 log file .................................... 583 mesh treatment options .....221, 587 settings dialog box feature isolation .................... 585 limits tab .............................. 586 settings tab .......................... 586 settings dialog box ................... 584 settings menu .......................... 584 AutoGEM.................................... 564 automatic connections gaps in assemblies ................... 219 results when using.................... 241 automatic connections ................. 161 BACS (Beam Action Coordinate System) .................................. 265 batch design studies .................... 784 edge distribution ................... 566 edge length .......................... 567 creating mesh elements............ 570 1298 BCPCS (Beam Centroidal Principal Coordinate System) .................. 266 beam action coordinate system ..... 265 Index beam bending in results .............. 860 beam centroidal principal coordinate system ................................... 266 Beam command ......................... 573 guidelines................................ 441 bibliography ............................... 992 boundary conditions, Thermal prescribed temperatures ........... 421 beam elements .......................... 573 beam orientation defining .................................. 266 in results ................................ 866 beam orientation ........................ 264 beam releases............................ 267 beam resultant results quantity .... 873 beam shape coordinate system .... 265 beams action coordinate system .......... 265 centroidal principal coordinate system ................................ 266 creating.................................. 226 checking model........................... 654 in results ................................ 873 color scale.................................. 919 normals .................................. 969 component visibility in results ....... 851 orientation ....................... 264, 866 components - defining heat loads .. 488 releases.................................. 267 computers with parallel processing 822 sections.................................. 258 configuration file shape coordinate system .......... 265 changing settings .......................61 beams....................................... 225 connected and unconnected parts . 102 bearing loads connections defining .................................. 442 1299 BSCS (Beam Shape Coordinate System) .................................. 265 buckling analysis overview ................................. 672 buckling analysis......................... 672 capping surfaces ......................... 921 center of mass measures defining .................................. 534 overview ................................. 528 center of mass measures ............. 528 centrifugal loads defining .................................. 445 Structural and Thermal Simulation - Help Topic Collection automatic midsurface connections .......................................... 161 contact regions........................ 179 defining................................ 386 guidelines ............................. 381 relations functions ................. 431 end welds ............................... 161 troubleshooting ..................... 398 fasteners ................................ 168 displacement ........................... 376 FEM mode............................... 187 symmetry gaps ...................................... 188 mirror .................................. 393 interfaces constraints, Structure .................. 376 FEM mode ............................ 187 contact analysis native mode ......................... 185 creating .................................. 669 interfaces ............................... 199 contact measures perimeter welds....................... 161 defining .................................. 527 precedence rules .............. 190, 239 overview ................................. 537 rigid connections...................... 166 contact measures........................ 527 rigid links................................ 181 contact pressure results quantity... 872 weighted links ......................... 183 contact regions connections ............................... 160 2D models............................... 179 constraint sets 3D models............................... 180 guidelines ............................... 380 creating .................................. 180 overview................................. 381 overview ................................. 179 constraint sets ........................... 381 contact regions ........................... 179 constraints, Structure contour plot for results ................ 861 along surface .......................... 394 convection conditions displacement defining .................................. 418 adding ................................. 377 coordinate systems 1300 Index creating.................................. 148 in results ................................ 866 setting for an advanced mass .... 232 coordinate systems ..................... 147 creating features ........................ 143 custom system of units editing.................................... 106 overview................................. 109 custom system of units ............... 109 custom unit creating.................................. 106 editing.................................... 105 custom unit ............................... 108 cyclic symmetry adding.................................... 391 defining .................................. 392 guidelines ............................... 390 database files............................. 995 datum features coordinate systems creating ............................... 148 cylindrical ............................ 155 overview .............................. 147 spherical .............................. 153 coordinate systems .................. 147 datum axes creating................................ 146 datum curves creating................................ 147 overview .............................. 146 datum curves........................... 146 datum planes creating................................ 145 overview .............................. 145 datum planes........................... 145 datum points and custom measures ............ 548 creating................................ 144 overview .............................. 144 datum points ........................... 144 promoting to Pro/ENGINEER ...... 142 datum features ........................... 142 deformed display in results........... 869 design parameters defining .................................. 643 overview ................................. 638 preparing your model................ 640 types ...................................... 641 design parameters ...................... 641 design studies 1301 Structural and Thermal Simulation - Help Topic Collection defining accessing summary report...... 786 batch file ............................. 784 creating ............................... 658 global sensitivity ................... 754 local sensitivity ..................... 757 modifying............................. 807 optimization ......................... 759 results ................................. 824 running................................ 774 standard .............................. 752 defining .................................. 752 types ..................................... 752 design studies ............................ 749 Diagnose command .................... 789 dimension name changes............... 33 direction, in pressure loads .......... 449 defining .................................. 538 overview ................................. 529 driven pro parameter measure...... 529 driving parameters ........................98 DSGN CONTROLS menu ............... 638 dynamic analyses, measures for.... 517 dynamic frequency analysis .......... 722 dynamic query............................ 946 dynamic random analysis ............. 723 dynamic shock analysis................ 724 dynamic time analysis ................. 720 elements 2D solids ................................. 574 approximated linear edges......... 636 beam ...................................... 573 creating automatically using AutoGEM .............................. 564 mass ...................................... 573 displacement measure................. 521 properties ............................... 257 displacement results quantity ....... 871 shell ....................................... 572 display location in results...... 833, 901 solid ....................................... 572 display options in results ...... 832, 900 spring ..................................... 573 display types in results ......... 831, 899 types in Structure..................... 576 displaying result windows ............ 929 types in Thermal ...................... 576 driven parameters ........................ 98 elements.................................... 575 driven pro parameter measure 1302 Index entities, transferring from Pro/ENGINEER........................1013 environment variables ................... 62 equations, for shell properties .....1071 export as MPEG .......................... 960 Export HTML command................ 962 Export VRML command................ 962 failure index measure defining .................................. 534 overview................................. 520 failure index measure.................. 520 failure index results quantity ........ 885 family tables for simulation features 54 fasteners effect on mesh ........................ 170 prerequisites ........................... 169 fasteners ................................... 168 fatigue fatigue measures defining ............................... 535 overview .............................. 527 fatigue measures ..................... 527 fatigue results quantity............. 873 fatigue ........................................ 84 feature interference ...................... 30 features coordinate systems................... 147 creating simulation features in Pro/ENGINEER ...................... 143 datum curves........................... 146 datum planes........................... 145 datum points ........................... 144 simulation features guidelines .... 143 suppressing ...............................30 volume region.......................... 158 features ..................................... 141 FEM mode analyses.................................. 737 basic workflow ...........................24 connections ............................. 187 creating parameters ................. 906 database files .......................... 995 display settings and visibilities .....55 displaying analysis results ......... 892 FEA solver runs ........................ 795 gaps creating................................ 190 overview .............................. 188 gaps ....................................... 188 material 1303 Structural and Thermal Simulation - Help Topic Collection assigning ............................. 297 overview .............................. 297 material.................................. 297 meshes assembly ............................. 597 checking .............................. 623 connections .......................... 604 erasing ................................ 591 flat meshes .......................... 598 mixed mesh ......................... 619 operations............................ 620 parabolic elements ................ 798 retained meshes ................... 592 retrieving ............................. 629 reviewing ...................... 621, 799 shell mesh ........................... 617 storing.......................... 628, 742 transient meshes .................. 592 troubleshooting..................... 596 meshes .................................. 591 neutral format file ...................1019 outputting decks ...................... 797 overview................................... 77 radiation constraint .................. 425 running FEM analysis ................ 795 supported FEA solvers............... 910 FEM mode ....................................77 FEM Mode command.................... 591 file types.................................. 1003 flat FEM meshes.......................... 598 flux results quantity..................... 879 force and moment loads defining .................................. 439 distribution .............................. 438 guidelines................................ 437 force and moment results beam resultant......................... 873 reaction .................................. 883 shear and moment ................... 877 shell resultant .......................... 876 shell transverse shear ............... 855 force and moment results............. 882 force measures defining .................................. 536 overview ................................. 522 force measures ........................... 522 frequency/time step, in results..... 831, 898 fringe plot for results running FEA solvers online ........ 797 1304 Index contour plots ........................... 861 displaying values ..................... 946 overview................................. 886 tips ........................................ 859 fringe plot for results .................. 886 function in FEM mode creating ............................... 979 overview .............................. 976 valid symbols ....................... 977 in FEM mode ........................... 976 in native mode creating ............................... 976 overview .............................. 970 symbolic overview ........................... 971 valid symbols..................... 972 symbolic .............................. 971 in native mode ........................ 970 function..................................... 970 gap connections in FEM mode....... 188 gaps in assemblies...................... 219 gaps in parts.............................. 218 global sensitivity design study ...... 754 glossary ...................................1264 graphing results .......................... 944 gravity loads defining .................................. 447 guidelines for assemblies ...............35 guidelines for building parts............29 guidelines for shell properties ....... 272 guidelines for structure loads ........ 434 heat flux measure defining .................................. 538 overview ................................. 532 heat flux measure ....................... 532 heat loads defining FEM mode ............................ 491 native mode.......................... 487 defining .................................. 487 overview ................................. 481 reviewing ................................ 492 heat loads .................................. 481 help system..................................63 icon display ..................................55 icons mesh control ........................... 613 setting icon visibilities .................55 toolbar......................................50 1305 Structural and Thermal Simulation - Help Topic Collection types ..................................... 984 icons........................................... 50 idealizations and connections....................... 160 beams .................................... 225 in assembly mode ...................... 94 masses................................... 230 precedence rules .............. 190, 239 shells ..................................... 210 springs ................................... 234 idealizations............................... 210 independent mode for Mechanica.... 27 integrated mode for Mechanica....... 26 isosurfaces, in results.................. 861 iterative solver overview................................. 779 selecting................................. 819 iterative solver ........................... 779 labels in result windows............... 948 large deformation static analysis creating.................................. 667 overview................................. 666 layers in results ................................ 851 overview................................... 52 1306 layers ..........................................52 load sets guidelines.........................435, 483 in results..........................831, 898 load sets .............. 434, 435, 482, 483 loads basics ..................................... 432 bearing loads defining................................ 442 guidelines ............................. 441 centrifugal loads defining................................ 445 force and moment loads defining................................ 439 distribution ........................... 438 guidelines ............................. 437 gravity loads defining................................ 447 heat loads defining FEM mode.......................... 491 native mode ....................... 487 defining................................ 487 overview .............................. 481 reviewing ............................. 492 Index heat loads............................... 481 importing external temperatures 455 load sets.......................... 435, 483 MEC/T temperature load defining ............................... 455 mass elements ........................... 573 mass properties .......................... 281 masses adding to curves, edges, and surfaces ............................... 234 adding to points ....................... 232 overview .............................. 453 overview ................................. 230 MEC/T temperature load ........... 453 Mechanism Design loads creation ............................... 477 defining ............................... 458 pressure loads defining ............................... 450 relations functions ................... 431 structure loads guidelines ............................ 434 overview .............................. 430 structure loads ........................ 430 temperature loads guidelines ............................ 451 troubleshooting ....................... 459 using temperature load in Structure .......................................... 453 loads ................................. 430, 481 measure results quantity.............. 885 local sensitivity design study ........ 757 measures Log command, on AutoGEM menu. 583 acceleration ............................. 524 1307 types for curves, edges, and surfaces ............................... 233 types for points ........................ 231 masses ...................................... 230 material orientation assigning................................. 308 in results................................. 855 material orientation ..................... 305 materials assigning................................. 290 assigning in FEM mode .............. 297 defining ...........................291, 298 FEM mode ............................... 297 guidelines................................ 282 types ...................................... 283 materials ................................... 282 Structural and Thermal Simulation - Help Topic Collection center of mass ........................ 528 contact ................................... 527 coordinate systems and ............ 511 displacement........................... 521 driven pro parameter ............... 529 failure index ............................ 520 fatigue ................................... 527 for dynamic analyses................ 517 for thermal analysis ................. 531 moment of inertia .................... 528 phase..................................... 526 predefined .............................. 497 results available....................... 533 results graph types .................. 865 results quantity ....................... 885 rotation .................................. 521 rotational acceleration .............. 525 rotational velocity .................... 525 selecting for analyses ............... 516 strain ..................................... 520 stress..................................... 520 time ....................................... 526 ucs-based ............................... 562 uses....................................... 495 velocity .................................. 524 1308 measures ................................... 494 MEC/T temperature load defining .................................. 455 overview ................................. 453 MEC/T temperature load .............. 453 Mechanica 2D analysis................................45 analysis overview ..................... 749 assembly considerations..............35 bibliography ............................ 992 creating custom system of units . 109 database considerations ............ 995 dimension name changes ............33 DSGN CONTROLS menu ............ 638 FEM mode .................................77 files ...................................... 1003 getting started ............................ 3 glossary ................................ 1264 guidelines for building parts .........29 icons ...................................... 984 Model menu............................. 130 model types............................. 131 modeling strategies and optimization......................46 building parts and assemblies....29 Index operating modes independent mode .................. 27 integrated mode ..................... 26 process overview ....................... 65 product line overview ................................ 21 Structure ............................... 21 Thermal ................................. 22 product line............................... 21 setting simulation display............ 55 setting units.............................. 36 toolbar ..................................... 50 using Pro/ENGINEER parameters . 39 workflow................................... 65 Mechanica ..................................... 1 mechevnt file ............................1003 meshing guidelines, FEM mode ..... 593 midsurface compression assemblies .............................. 219 parts ...................................... 218 midsurface compression .............. 221 modal analysis overview................................. 670 results............................. 831, 898 model display in results ............... 879 model types 2D axisymmetric structure......... 134 2D axisymmetric thermal .......... 137 2D plate thermal ...................... 136 2D unit depth thermal............... 136 3D...................................132, 135 defining 2D models................... 139 guidelines................................ 138 model type specification ............ 130 plane strain ............................. 133 plane stress ............................. 133 selecting ................................. 138 model types ............................... 131 modeling entities in assembly mode 94 modeling features ....................... 141 moment measures defining .................................. 537 overview ................................. 522 moment measures ...................... 522 moment of inertia measures defining .................................. 536 overview ................................. 528 moment of inertia measures ......... 528 NASTRAN importing files for mesh ............ 620 1309 Structural and Thermal Simulation - Help Topic Collection outputting to ........................... 744 templates ............................... 741 NASTRAN .................................. 744 near point measures ................... 505 normals shell....................................... 970 surface ................................... 968 normals..................................... 968 optimization and assemblies .......... 47 optimization and suppressed features ............................................... 46 optimization design study gaps ....................................... 218 guidelines for building .................29 midsurface compression ............ 218 parts ...........................................29 perimeter welds .......................... 161 phase measure defining .................................. 539 overview ................................. 526 types ...................................... 561 phase measure ........................... 526 plane strain model type ............... 133 plane stress model type ............... 133 creating.................................. 764 p-level quantity in results............. 884 saving optimized shape ............ 765 ply orientation in results .............. 851 optimization design study ............ 759 point measures ........................... 504 optimization planning .................... 46 precedence rules..................190, 239 parallel processing ...................... 822 predefined systems of units .......... 126 parameter-capable edit fields ....... 244 predefined units .......................... 127 parameters prescribed temperatures in design studies...................... 757 defining .................................. 424 Pro/ENGINEER parameters .......... 39 overview ................................. 421 parameters ................................ 757 prescribed temperatures .............. 421 parameters, driven and driving....... 98 pressure loads parts defining .................................. 450 connected and unconnected ...... 102 direction.................................. 449 1310 Index guidelines ............................... 449 prestress modal analysis overview................................. 671 results............................. 831, 898 prestress static analysis overview................................. 664 results............................. 831, 898 prestress static analysis............... 664 Pro/ENGINEER parameters, using in Mechanica................................. 39 Pro/ENGINEER Relations menu ..... 431 guidelines ............................. 282 material .................................. 282 material orientation creating................................ 310 material orientation .................. 305 shell defining................................ 275 guidelines ............................. 272 shell ....................................... 269 spring ..................................... 276 properties .................................. 256 Pro/ENGINEER, transferring entities from .....................................1013 Pro/FEM neutral file format .........1019 promoting simulation features to Pro/ENGINEER......................... 142 properties beam orientation ..................... 264 beam releases ......................... 267 beam sections ......................... 258 deleting .................................. 256 for elements............................ 257 guidelines for using .................. 257 mass properties....................... 281 material creating ........................ 292, 299 quantity in results ....................... 882 query in results........................... 928 quilts......................................... 620 radiation constraint ..................... 425 reaction at point constraints results quantity .................................. 882 reaction results quantity .............. 883 relative results............................ 874 result windows defining ...........................829, 897 display options animation ............................. 858 contour ................................ 861 displaying result window......... 929 1311 Structural and Thermal Simulation - Help Topic Collection fringe .................................. 886 graph .................................. 882 model.................................. 879 vectors ................................ 857 display options ................. 832, 900 labels ..................................... 948 loading ................................... 836 location ........................... 833, 901 reviewing................................ 927 saving ............................. 837, 904 titles ...................................... 947 toolbar ............................ 826, 894 result windows .................... 829, 897 results animation ............................... 858 animation control..................... 920 annotating ....................... 834, 902 available for measures.............. 533 component visibility ................. 851 dynamic query ........................ 928 evaluating........................ 835, 903 exporting HTML ....................... 962 exporting VRML ....................... 962 FEM mode loading NASTRAN results........ 891 1312 overview .............................. 890 FEM mode ............................... 890 graphing ................................. 944 layer visibility .......................... 851 linearized stress ....................... 951 quantity .................................. 882 relative ................................... 874 reporting ..........................838, 905 result windows annotating .....................834, 902 basics functions..............828, 896 changing .............................. 927 comparing ............................ 930 defining.........................829, 897 displaying ............................. 929 editing ................................. 918 file menu .............................. 962 loading................................. 836 location .........................833, 901 printing ................................ 947 reviewing ............................. 927 saving ...........................837, 904 saving views ......................... 929 titles .................................... 947 toolbar ..........................827, 894 Index tying multiple ....................... 937 untying ................................ 937 view menu ........................... 961 result windows ................. 829, 897 templates creating new result windows from ....................................... 859 saving .......................... 837, 904 results in FEM mode .................... 890 results user interface ............825, 893 rigid connections creating .................................. 167 overview ................................. 166 rigid connections ......................... 166 rotation acceleration measure defining .................................. 539 templates ........................ 837, 904 overview ................................. 525 viewing .................................. 828 rotation acceleration measure ....... 525 results ...................................... 824 results in FEM mode creating parameters ................. 905 displaying element IDs, node IDs, and result values .................. 926 displaying the mesh ................... 82 rotation measure ........................ 521 loading NASTRAN results .......... 891 rotation results quantity ............... 878 modal analysis ........................ 914 rotation velocity measure statistics defining .................................. 539 graphing .............................. 914 overview ................................. 525 output ................................. 912 rotation velocity measure ............. 525 output thermal ..................... 913 rotation velocity results quantity ... 877 statistics ................................. 914 run structural analysis.................... 914 accessing summary report ......... 786 thermal analysis ...................... 913 batch file................................. 784 using the postprocessor ............ 891 1313 rotation acceleration results quantity ............................................. 874 rotation measure defining .................................. 537 overview ................................. 521 Structural and Thermal Simulation - Help Topic Collection error detection ........................ 781 error resolution ....................... 812 for FEM output formats...................... 743 outputting decks ................... 801 overview .............................. 795 reviewing the solver mesh621, 799 solving online ....................... 796 for FEM................................... 795 overview................................. 774 parallel processing ................... 822 reviewing errors ...................... 789 stopping ................................. 785 run ........................................... 774 saved views in results ................. 929 shear & moment results quantity .. 877 shell elements ............................ 572 shell models creation guidelines ................... 214 defining shells advanced ............................. 213 simple ................................. 212 defining shells ......................... 211 shell models............................... 210 shell normals ............................. 970 1314 shell properties equations .............................. 1071 guidelines................................ 272 thickness................................. 359 types ...................................... 272 shell properties ........................... 269 shell resultant results quantity ...... 876 shell transverse shear.................. 876 simple springs ............................ 236 simulation display .........................55 simulation features coordinate systems................... 147 creating ...........................141, 142 datum curves........................... 146 datum planes........................... 145 datum points ........................... 144 guidelines................................ 143 promoting to Pro/ENGINEER ...... 142 simulation features...................... 141 simulation model information..........81 sketcher, using ........................... 261 solid elements ............................ 319 solvers iterative .................................. 819 supported FEA ......................... 910 Index solvers ...................................... 819 spatial variation for loads............. 439 spin softening ............................ 692 spring stiffness........................... 276 springs advanced................................ 237 creating advanced springs .................. 239 simple springs ...................... 236 to ground springs.................. 237 creating.................................. 234 guidelines for creating .............. 235 simple .................................... 236 to ground ............................... 237 springs...................................... 234 standard design study creating.................................. 753 overview................................. 752 standard design study ................. 752 static analysis creating.................................. 663 strain energy results quantity....... 876 strain measure defining .................................. 540 overview................................. 520 strain measure ........................... 520 strain results quantity.................. 888 stress measure defining .................................. 540 overview ................................. 520 stress measure ........................... 520 stress results quantity ................. 887 structural analysis ....................... 660 Structure .....................................21 Structure constraints adding .................................... 377 defining .................................. 386 guidelines................................ 381 guidelines for sets .................... 380 sets ........................................ 381 troubleshooting ........................ 398 using in structural analyses ....... 661 Structure constraints ................... 376 Structure loads basics ..................................... 432 guidelines................................ 434 heat loads ............................... 481 spatial variation ....................... 439 troubleshooting ........................ 459 Structure loads ........................... 430 1315 Structural and Thermal Simulation - Help Topic Collection study, selecting in results ..... 829, 897 summary report for design study .. 786 suppressed features in optimized parts ............................................... 46 suppressing features ..................... 30 temperature measure defining .................................. 540 overview ................................. 532 temperature measure .................. 532 temperature results quantity ........ 876 suppressing simulation features...... 54 Thermal .......................................22 Surface command, on AutoGEM menu ............................................. 578 surface normals.......................... 968 surface regions creating.................................. 158 symbolic function........................ 971 overview ................................. 396 systems of units ......................... 108 prescribed temperatures temp gradient measure ............... 532 defining................................ 424 temp gradient results quantity...... 875 overview .............................. 421 temperature gradient measure prescribed temperatures ........... 421 defining .................................. 538 overview................................. 532 temperature gradient measure ..... 532 temperature loads global temperature change........ 451 guidelines ............................... 451 importing external temperatures 455 MEC/T .................................... 453 structural in FEM mode ............. 463 using in Structure .................... 453 1316 thermal constraints and boundary conditions ............................... 396 Thermal elements ....................... 576 Thermal icons ............................. 984 Thermal loads heat loads ............................... 481 Thermal loads............................. 481 Thermal measures heat flux ................................. 532 temp gradient .......................... 532 thermal analysis measures for ........................... 531 thermal analysis ......................... 704 thermal constraints and boundary conditions Index temperature............................ 532 thermal strain energy results quantity ............................................. 875 thermal strain results quantity...... 856 managing ................................ 107 predefined ............................... 127 reviewing ................................ 105 setting .................................... 127 time measures units ......................................... 128 defining .................................. 540 Units command........................... 128 overview................................. 526 vectors in results ........................ 857 time measures ........................... 526 velocity measure time step/frequency, in results .... 831, 898 titles, in result windows ............... 947 TLAP load .................................. 471 to ground springs ....................... 237 total heat loads reviewing................................ 492 total heat loads .......................... 485 UCS (User Coordinate System) ..... 147 unit conversion tables ................. 110 unit, creating custom .................. 106 unit, editing custom .................... 105 units creating custom system ............ 129 custom ................................... 108 custom system ........................ 109 defining .................................. 128 guidelines ............................... 110 dynamic shock response analysis ......................................... 1240 dynamic time response analysis 1234 large deformation analysis ....... 1254 modal analysis ....................... 1188 optimization analysis .............. 1260 prestress modal analysis ......... 1257 static analysis ........................ 1088 steady-state thermal analysis .. 1211 1317 defining .................................. 535 overview ................................. 524 velocity measure......................... 524 velocity results quantity ............... 856 Verification Guide 2D and 3D contact analysis...... 1249 buckling analysis .................... 1243 dynamic frequency response analysis ......................................... 1237 Structural and Thermal Simulation - Help Topic Collection Verification Guide ......................1081 vibration analysis dynamic frequency................... 722 dynamic random...................... 723 dynamic shock ........................ 724 dynamic time .......................... 720 vibration analysis ....................... 719 viewing icons ............................... 55 visibility of icons ........................... 55 Volume command, on AutoGEM menu strategies ............................... 580 volume regions creating .................................. 159 overview ................................. 158 volume regions ........................... 158 volumetric heat loads .................. 488 WCS (World Coordinate System) ... 147 working with assemblies ................35 Y direction for advanced springs................. 238 for beams................................ 228 Y direction.................................. 228 1318