ABSTRACTThe project focuses on the design and stress analysis of a car frontal protection system (Bumper) simulations. To achieve that, we go to basic concepts of improving the safety on the car by do analysis the car bumper. It is important to know their mechanical properties, how their failure mechanism during the impact. This analysis was carrying out by using commercial Finite Elements software (ALGOR) to evaluate the behavior of bumper system. Another additional innovative for improving crashworthiness is the use of material to produces the part to absorb Energy during the process of a crash. Research concentrates on polymer composite material. It is considering their function, geometry, and other parameters that influence the compatibility of the bumper. In future research, this bumper will face the static test and analyses do on their load distributions by applying the variation of load and locations. Result will be compare for the centre and side load. How the load applied effect the stress distribution. After that a related study was carried out to know bumper properties during the impact. Bumpers play an important role in preventing theimpact energy from being transferred to the automobile and passengers. Saving the impact energy in the bumper to be released in the environment reduces the damages of the automobile and passengers Bumper car It is the generic name for a type of flat ride consisting of several small electric cars which draw power from the floor and/or ceiling, and which are turned on and off remotely by an operator]. They are also known as bumping cars, dashing cars, dodgem cars, or simply dodgems, the last name being the usual term in British English. Design Power is commonly supplied by one of two methods: The oldest and most common method uses a conductive floor and ceiling, each with a separate power polarity. Contacts under the vehicle touch the floor while a pole mounted contact touches the ceiling, forming a complete circuit. newer method uses alternating strips of metal across the floor separated by insulating spacers, and no ceiling grid. The alternating strips carry the supply current, and the bumper cars are large enough so that the vehicle body can always cover at least two strips at any one time. An array of brushes under the car make random contact with whatever strip is below, and the voltage polarity on each contact is sorted out to always provide a correct and complete circuit to operate the vehicle. The metal floor is usually set up as a rectangular or oval track, and graphite is sprinkled on the floor to decrease friction. A rubber bumper surrounds each vehicle, and drivers ram each other as they travel. The controls are usually an accelerator and a steering wheel. The car necessary in the frequent pile-ups that occur. Most carnivals and amusement parks require riders to be at least 42 inches or taller to ride and 52 inches (1.3 m) or taller to drive the cars. Although the idea of the ride is to bump other cars." Depending on the level of enforcement by operators. safety-conscious (or at least litigationconscious) owners often put up signs reading "This way around" and "No bumping. . these rules are often ignored by bumper car riders. especially younger children. in development of technology especially in engineering field make among the engineers more creative and competitive in designing or creating new product. Additionally. namely bumper beam. it should be able to protect its occupants when accidents happen. and it carries out multiple functions. and ability to produce complex shapes.CHAPTER 1 INTRODUCTION 1. high specific strength. They must be precise and showing careful attentions on what they produce. Here. we concentrate on automotive industry. a short crumple zone for crash energy absorption One of the options to reduce energy consumption is weight reduction. low weight. bumper fascia. Among the components in the automotive industry substituted by polymeric based composite materials are the bumper beam. A new invention in technology material was introduced with polymeric based composite materials. connecting rod. the automotive body designer should . the designer should be aware that in order to reduce the weight.1 BACKGROUND OF THE STUDY Nowadays. To do this. It should hold the parts of the vehicle together and serve to filter noise and vibration. However. The automotive body is one of the critical subsystems of an automobile. corrosion free. The bumper system consists of three main components. The greatest demand facing the automotive industry has been to provide safer vehicles with high fuel efficiency at minimum cost. pedal box system. and door inner panel. spoiler. Current automotive vehicle structures have one fundamental handicap. fascia and energy absorber. which offer high specific stiffness. the safety of the car passenger must not be sacrificed. and high impact energy absorption [1]. Substitution of polymeric based composite material in car components was successfully implemented in the quest for fuel and weight reduction. 3]. stiffness. Figure 1: Based composite material bumper Proton Pesona .create a structure with significant levels of strength. and energy absorption [2. BUMPER DESIGN FOR VEHICLE SAFETY Because of these limitations. Evans and Morgan (1999) [9] studied thermoplastic energy absorbers for bumpers. (2002) [5] investigated the applicability of stainless steel for crash-absorbing bumpers to increase crash performance in automotive vehicles. Carley (2004) [7] introduced Expanded Polypropylene (EPP) foam technologies and techniques for bumper systems. bumper design has focused on material and structure. Anderson et al. During a frontal crash. . the fatality rate increases dramatically in high speed impacts. Butler (2002) [6] studied the design of efficient epoxy structural foam reinforcements to increase the 9 energy absorbed in front and rear automotive bumper beams. the front side member is expected to fold progressively. (1995) [8] developed a new composite bumper that has two pads at each end of the bumper. so as to absorb more energy and to ensure enough passenger space. To do so. Cheon et al. the mechanism of absorbing the crash energy would be totally different from that of the passive structure. their design included reinforcing the cross-section. various cross sections and shapes have been investigated for the front rail of the automotive body to maximize crashworthiness and weight efficiency. For several decades. technological development is still needed. In order to design a successful lightweight vehicle and significantly improve the crash performance of current cars. If the automotive body could extend its front end during or right before a crash. Figure 2: Automotive bumper system component . Its types include foam. Fig. Usuallyfascias are made of polypropylene. 1. Energy absorbers: energy absorbers are designed to absorb a portion of the kinetic energy From vehicle collision. However mechanical absorbers have several times the weightof foam and honey comb . Traditional models have corrugated open section areas for installing some car elements and increasingbending strength of the bumper.II. lightweight and aesthetically pleasing to the consumer. Main parts of theconventional bumper systems are depicted in Fig. polyurethane orpolycarbonate.BUMPER MODEL DESIGN There are several models and systems for bumpers ofpassenger cars [15]. 1 Configuration of common bumper type 1. honeycomb and mechanical ones. 2. Fascia: bumper fascias must be aerodynamic. in low-speed contacts. 1. In addition to 4 horizontal springs for connecting the fascia tobase plate. Connecting plastic parts: two propylene (PEP) parts thatconnect the bumper base plate to the car. Front rubber tape: that is composed of polypropylene(PEP) for damping of poor Contacts. Reinforcing beam: this part is a key component of thebumper and helps absorb the kinetic energy and provideprotection to the rest of the vehicle. the kinetic energy of impact or is absorbed by changing the impactforce direction by the spring system (as mechanical energy absorbers) and in high speed contacts it is absorbed bydeformation of conic composite cells of the bumper (asreinforcing beam).Absorber. 3. Spring system: it contains 26 vertical springs forconverting the kinetic energy to the spring potential energy. reinforcing beam). The designed bumper in this research is a combination ofthese element. Fascia: it indicates the aerodynamic form of the bumper 3. Conics and base plate: they are main elements of thebumper for energy absorbing in high speed contacts (i. In other words.The main elements of this bumper are as follows (see Fig. .e. they receive limited usage. 5. 2. 4. it absorbs kinetic energy in the form of spring potentialenergy. which guarantee easier deformation rather than the other parts of the cover. so. there are two lateral notch at the top andbottom corners of the cover). For high speed contacts. Also. the cover edges movements mechanism is completely predictedand in control. There is aconcavity in the cover where the plastic tape seats on andincreases the bending strength of the bumper.So. two small areas Between the cover edge and themiddle part of the cover have designed with thinner thicknesses (i. .e. the cover reaches the conics and they deforms as a composed part. Fig. 3 section view of bumper – cover and spring movement during Frontal impact . The computer system consists of the hardware and software to perform the specialized design functions required by particular use firm. one or more graphics display terminals. The computer has grown to be essential in the operations of business. who communicates data and commands to the computer through and several input devices. Ultimately CAD will provide the technology base for the computer-integrated factory of the future. engineering. and numerical control part programming. especially in recent years. This technology is moving in the direction of greater integration of design and manufacturing which was earlier treated as distinct and separate function in a production firm. It is a technology concerned with the use of computers to perform certain functions in Design and Production. analysis. to be very powerful tool in design and manufacturing . modification. and other peripheral equipment. These factors raise the difference in CAD system requirements. the other major component is human designer. The CAD software consists of the computer programs to implement computer graphics on the system plus application programs to facilitate the engineering functions of the user company. The user in the computer graphics design system in the designer. and research. and customer markets are different. It also demonstrated itself. heat transfer calculations. government. The collection of application programs will vary from one user firm to the next because their product lines. or optimization of a design. dynamic response of mechanisms. the military. manufacturing processes. . Interactive computer graphics denote a user-oriented system in which the computer is employed to create. It is important to note that ICG system is one main component of computer-aided design system. Computer-aided design(CAD) can be defined as the use of computer system to assist in the creation. Examples of these application programs include stress-strain analysis of components.INTRODUCTION TO PRO-E INTRODUCTION TO CAD CAD is the term which means computer-aided design. Modern computers systems are based on interactive computer graphics (ICG). and display data in the form of pictures and symbols. transform. keyboards. The CAD hardware typically includes the computer. Computers also include nongraphic applications of the computer in deisgn work. APT is the acronym of Automatically Programmed Tools. Nongraphic hardware can employee to create rough images on a piece of paper by appropriate combinations of characters and symbols. It represents a significant factor in determining how convenient and efficient it is for a designer to use the CAD system. configurations and capabilities. . The process of designing something is characterized as an iterative procedure. The CAD workstation is the system interface with the outside world. 3) It must provide digital displacement of graphic image. 1) It must interface with the central processing unit. The workstation must accomplish five functions. ICG forms the essential technological foundation for computer-aided design. Engineering firms that are not involved in production would chose a system exclusively for drafting and design-related functions. 1) Recognition of need 2) Definition of problem 3) Synthesis 4) Analysis and Optimization 5) Evaluation 6) Presentation Hardware components for computer-aided design are available in a variety of sizes. Let us first consider the general design process. which consists of six identifiable steps of phases. Hence it is possible to select a CAD system that meets the particular computational and graphics requirements of the user firm.The evolution of computer-aided design has been largely related to developments in computer graphics.Before examining the several facts of computer-aided design. One of the significant initial projects in the area of computer graphics was the development of the APT language. 2) It must generate a study graphic image for the user. These consistes of engineering results which are best displayed in order than graphical form. Surfacing. Created by Dr. Simulation. All data is associative and interchangeable between the CAD. This capability enables concurrent engineering — design. Companies use Creo Elements/Pro to create a complete 3D digital model of their products. Data Interoperability. Tolerance Analysis. analysis and manufacturing capabilities on one. integrated 3D CAD/CAM/CAE solution. and revision control information. analysis and manufacturing engineers working in parallel — and streamlines product development processes. Samuel P. Creo Elements/Pro is a software application within the CAID/CAD/CAM/CAE category. rapid prototyping. Geisberg in the mid-1980s. Routed Systems Design. Creo Elements/Pro provides a complete set of design. The parametric modeling approach uses parameters. PTC's parametric. features. integral. and relationships to capture intended product behavior and create a recipe which enables design automation and the optimization of design and product development processes. along with other similar products currently on the market. or where the resulting geometry may be complex or based upon equations. design and manufacturing. Pro/ENGINEER was the industry's first successful rule-based constraint (sometimes called "parametric" or "variational") 3D CAD modeling system. scalable platform. A product and its entire bill of materials (BOM) can be modeled accurately with fully associative engineering drawings. The models consist of 2D and 3D solid model data which can also be used downstream in finite element analysis. dimensions. is used by discrete manufacturers for mechanical engineering. tooling design. and CNC manufacturing. . The associativity functionality in Creo Elements/Pro enables users to make changes in the design at any time during the product development process and automatically update downstream deliverables. These required capabilities include Solid Modeling. CAE and CAM modules without conversion. Rendering. This design approach is used by companies whose product strategy is family-based or platform-driven.Creo Elements/Pro (formerly Pro/ENGINEER). where a prescriptive design strategy is fundamental to the success of the design process by embedding engineering constraints and relationships to quickly optimize the design. and NC and Tooling Design. as exemplified by the trajpar parameter. These range from conceptual Industrial design sketches. feature-based modeling architecture incorporated into a single database philosophy with advanced rule-based design capabilities. In addition to the general geometry tools there is also the ability to generate geometry of other integrated design disciplines such as industrial and standard pipe work and complete wiring definitions.Creo Elements/Pro is a parametric. It provides in-depth control of complex geometry. This data is then documented in a standard 2D production drawing or the 3D drawing standard. Tools are also available to support collaborative development. The capabilities of the product can be split into the three main headings of Engineering Design. A number of concept design tools that provide up-front Industrial Design concepts can then be used in the downstream process of engineering the product. . reverse engineering with point cloud data and comprehensive freeform surface tools. Engineering Design Creo Elements/Pro offers a range of tools to enable the generation of a complete digital representation of the product being designed. Analysis and Manufacturing. SKETCH USED IN MAKING CAR BUMPER EXTRUDE THE ABOVE SKETCH . SKETCH THE FOLLOWING SECTION TO MAKE HOLE . REMOVE THE MATERIAL SKETCH THE FOLLOWING SHAPE . EXTRUDE THE SKETCH COMPLETE DESIGN OF CAR BUMPER . 0. Part 581. Spring-damper element (Combi 165) was used for spring system modeling.0 of the bumper model was imported to LS-Dyna Anys8. conics and base plate is much smaller than the other dimensions of the part. Solid 164elements were used for imp actor. Then. Each plastic part is attached to the car body by screws at fourpoints. meshing has created on a 3D model. 4: . All degrees of freedoms of the corresponding nodes on the bumper. one-eighth of the car weight was attached to each screwed node as a point mass element (Mass166). The PRO E 5. There is no external force on the elements and no frictionwas assumed between the imp actor and the bumper surfaces and the car was taken to be laying on a flat and frictionless surface and all other conditions were drawing from American Traffic Safety Administration (49 CFR.Theimpactor as a steel structure was modeled by isotropicrigid pyramid solid impact elements. plastic parts and plastic tape (screwpoints) were coupled Andmerged. Hence. MESHING AND BOUNDARY CONDITIONS Explicit method is a fast method for short time problems. Membrane Blystchstchko-Tsy method was used for solution. the best element for meshing was the shell element (Shell163).III. on the model. BumperStandard).Finally meshing of different parts of the bumper with adequate numbers of elements Have done by Mapped method. Since the average thickness of the cover. (it is a fast method for membrane problems andcomposite material with corrugated surface).FEM specifications and element types used for the main parts Of the bumper are tabulated in Table 1 and Fig. complicated contact and impact Problems and multiple nonlinearities large deformations (Dynamic & quasi static) inLS-Dyna. plastic parts and plastic front rubber meshing. Introduction to ANSYS Starting ANSYS: The ANSYS graphical user interface can be started by selecting the ANSYS icon located in the ANSYS 8.1 folder. Selecting the ANSYS icon will take you directly to the graphical user interface. ANSYS Graphical User Interface: After starting ANSYS, two windows will appear. The first is the ANSYS 8.1 Output Window: This window displays a listing of every command that ANSYS executes. If you encounter problems, this is a good place to look to see what ANSYS is doing or has done. This is one location where you will find all of the warnings and error messages that appear and the command that generated the warning/error. The second window is the ANSYS ResearchFS graphical user interface. This is divided into 4 sections (shown on next page): 1. ANSYS Utility Menu 2. ANSYS Toolbar Menu 3. ANSYS Main Menu 4. Display window Each section will be discussed in further detail below. Within this menu, you can perform file operations, list and plot items, and change display options. Change Directory allows you to switch directories where the files are being saved. change. and save the current model.File Drop-down Menu The File drop-down menu includes the options to clear the database. it will write everything to the current jobname. Change Jobname changes the name of the database and associated files. It will not delete the previous jobname or associated files. The next time you save. . Note: unless you check the box for New log and error files. It does not clear the log or error files. it will continue to write to the current log and error files. Clear and Start New deletes the current database. resume. ANSYS does not automatically switch the current jobname to the name of the file you resumed from. and boundary conditions and loads applied to the model. Save as Jobname.db and Resume from allows you to open a model that has already been saved. the next time you save it will overwrite the current jobname and not the ―save as‖ file name. . If you do not change the jobname.Resume Jobname.db and Save as allow you to save the model. nodes. List Pull-down Menu The list pull-down menu allows you to view the log and error files. elements and their properties. If you choose ―save as‖ it will save the file as a different name. Note: If you resume a file. obtain a listing of geometric entities. Change the jobname otherwise you may write over another model. areas. . Use the plot elements command to obtain the mesh plot. These list the geometric entities and their components.This menu allows you to view the log and error files. Selecting the Nodes and Elements listings are easy methods to determine the number of nodes and elements in the model. volumes and elements. Plot Pull-down Menu: This pull-down menu allows you to plot the various components of the model such as key points. The log file is a summary of every command performed in ANSYS while the error file may provide insight into troubleshooting problems with the model/analysis. PlotCtrls Pull-Down Menu This menu includes the controls to pan/zoom/rotate your model. zoom and rotate the model. select the numbering options. change styles and generate hard copies of the plots. This pops up a window allowing you to pan. . volumes. lines. ANSYS Toolbar If you get a message reporting that the percent error cannot be calculated with powergraphics turned on. apply loads. The Main Menu is divided into sections that sequentially follow the steps involved in an analysis. solve. click the POWRGRPH button to turn off powergraphics. mesh. ANSYS Main Menu The ANSYS Main Menu contains all of the commands to create. The Hard Copy selection sends the plot to a printer or image file.The Numbering selection allows you to turn on/off the keypoint. nodes and element numbering. and view results of the FE analysis. areas. . . Use the modeling options to create the model. Multiple materials may be entered and applied to a model. Note: ANSYS uses a hierarchy for modeling: keypoints (lowest) lines areas volumes (highest) If you create a volume. Multiple types may be selected and applied to a model. lines and keypoints will be automatically created for you. .Select the element types to be used. all of the areas. Input the material properties. If you select Areas and Below. choose the Delete menu under Modeling. once deleted. it will delete the area plus the lines and keypoints that define the area. if you select Areas Only. To delete mistakes. the area will be deleted but the lines and keypoints that make up that area will remain. . the component must be re-created. It is important to select the right option.Use the meshing options to mesh the model. For example. NOTE: there is not an undo button in ANSYS. Choose the type of analysis to perform. . Apply loads and boundary conditions to the model. Solve the model. Post Processing . This can be used to get the maximum and minimum values of results. . click the powergraphics button on the ANSYS Toolbar to turn it off.Plot contour or vector plots of results. Lists the percent error. List the results for every node. If you get a message ―Cannot view percent error with powergraphics on‖. 5 Shows a cross section of this cellular structure. and the extra properties And the impact energy absorption capacity of GMThave been identified.) has less peak loads and more toughness in comparison with the GMT with 40% V.F. Fig. diameter ratio ofcell-top to cell-bottom. The GMT with 30%Volume fraction (V. including cell height. multi-layer 3D woven. 5 Schematic geometry of a basic grid-domed cellular structure In this research an impact test has simulated (with the sametest conditions that S.F.W. cell density and component content have also been optimized [17] Fig. Lam has Implemented [18]) for the grid-domed cell with GMT in AnsysLs-Dyna. 6) . MODEL ANALYSIS The results of some investigations by Tao & Yu [17-19] identified that the grid-domed cellular structure possesses the highest specific energy absorbing capacity among so many cell Configurations (including circular and square tubularknitted.IV. Projected wall area. non-woven Suspended and grid-domed cells) under both quasi-static compression andimpact conditions. other geometrical factors onthese flat-tapped cellular composites that govern the Energy absorbing capacity. In addition. (see Fig. the total impact energyshould be used for cover change from stage 1 to Stage 2 which also cause the springs to extend simultaneously (See Fig. So. the GMT with 30% V. 7). initial kinetic energy of the imp actor (as a Result fits initial velocity) could be derived as in (1): The objective of the spring design is to completely absorbthe above (1) kinetic energy as the cover reaches the conic sand its edges are opened and the springs are in maximumextension Length. In other words. . the Mass of imp actor must be equal to net camass.Fig.F. In accordance with the standard of straight front a impact test. with similar dimensions as usual car dampers has used for the first Try of design and analysis. 6 Absorbed energy – Normal displacement of GMT grid-domed Cellular sample under impact So. 7 cover movements and spring extension: stage 1-2 .Fig. so absorbed energy is negligible too. the simulation shows that in changing from stage 1 to stage 2. 1. the vertical displacement of the cover edges are more than 6 cm.In the case which there are no springs. prescribed parameters are: δ (springs displacement) and ns(number of springs in the system) which are held betweenconics. elastic hinges) and all deformations are completely elastic. Variable vector In which ―N‖ is the number of active coils.Mathematical model of the problem Will be as in equation(2) to (5): 1. thus there isn’t anyresistance forces on the cover edges. in this case. stressesare negligible.e. Related to the stages 1 & 2 and numbers of conics. ―D‖ is mean spring diameter and ―d‖ is spring wire diameter. Objective function . except in a small area Between the cover edge and the middle part of the cover (i. Other Parameters are identified by utilizing a genetic algorithm with the consideration on the minimum Weightofspring system (and so minimum weight of bumper). a movable bumper.Non equal boundary condition equations Today. what is interesting related of this research is now an innovative inflatable bumper concept.Equal boundary condition equation 3. and a morphing lattice structure with a locking mechanism that provides desired rigidity and energy absorption capability during a collision. Then stress distributions on vertical and horizontal path taken at time intervals of 0. including a morphing mechanism.2.25 s shown in .‖ is developed in this research for improved crashworthiness and safety of military and commercial vehicles. called the ―I-bumper. Another additional innovative means for improving crashworthiness is the use of tubes filled with a granular material to absorb energy during the process of a crash. two explosive airbags. The developed I-bumper has several active structural components. 052 s which correspond with the time that cover reaches to the conics. Maximum Von Misses stress Occurs at location 4 since the elements are under compression on the contacting surface with the Imp actor and under tension on the lateral direction. On vertical path. stresses are more tension than compression and also stress wave fluctuate and decreases along the path from the center of the . In horizontal path. Points 7. 16 respectively. 8 & 9 are those on the cover edge after the hinge and hence yielding Von Misses stresses of nearly zero. 15 & Fig. The maximum stress distribution occurs at t=0. The next extremes are for points 2 and 6 Because of stress concentration due to relative sharp corner and implemented notch (hinge) respectively.Fig. the stresses are a combination of compression in Longitudinal& lateral directions and tension in lateral direction. design engineers are Increasingly concerned about stress-related problems. Minimum value occurs at point 4 and is about 1. sporting. Material properties of plastics such as elastic modulus. typically with the strength. are the thermoplastics very different from metals? The answer is yes and no.Bumper to each side. and construction industries.5 that is generally satisfactory. because such behaviors are encountered only in special applications of metals. aerospace. Thus such stress analysis is also similar. plastics have been used for applications in load-bearing structural components in the automotive. there is a growing awareness of the importance of stress analysis. 1. Hence. these problems were primarily associated with the metallic components. because several calculations and test procedures for characterizing the mechanical properties of thermoplastics are very similar to those of metals. Many structural plastics design may be . 17. because a few types of behaviors of thermoplastic materials call for advanced techniques of analysis. because an effective analysis needs to bring together a thorough knowledge of the operating characteristic of the product. structural behavior and solid mechanics. yield point. Safety factor can be derived with the aid of maximum Von Misses stress and GMT yield strength. By utilizing this concept. stiffness and life expectancy of their products. Structural plastics design is a field that is evolving in the same manner as did the aero-space and nuclear power industries. the safety factor in vertical path has shown in Fig.2 MATERIAL PROPERTIES The common use of the term stress analysis includes any kind of structural analysis. Stress analysis has always been interdisciplinary. About many years ago. Material behavior. tensile strength and fracture toughness are understood. and better methods of design and analysis continuously reinforce each other and lead to the optimum design of the product. Stress analysis is a vital activity in this process. In the field of thermoplastics design. From the point of view of stress analysis. No. Yes. measured and used in a manner similar to those for metals. That is. a sequence of products innovations. In many years. b) To evaluate failure mechanism of the car bumper: i. iii. To analyze on mechanical properties focus on stress analysis ii. just take fixed point both end of the bumper. To modeling the actual dimension of the car bumper into the Solid Work software and analyze by using FE software (ALGOR). Only the Fascia part of the bumper will take into account.performed using the familiar strength of material approach.4 OBJECTIVES AND SCOPES a) To analyze the mechanical properties on front part (fascia) of car bumper: i.3 PROBLEM STATEMENT From the previous research or analysis on car bumper. Likewise detailed stress analyses of plastic components are performed assuming linear elastic behavior 1. 1. In the real situation. for this analysis just focusing on the stress analysis on car bumper by applying various loads on the static condition only. basically they focus on the design and crashworthiness optimization. there is much point that bumper mounting to the car which make it stronger or can absorb more energy during the impact. For the simulation. To study the load distribution on the bumper either it is uniformly . To investigate polymer composite material bumper (Proton Persona) based on their geometry and other parameters that Influence the compatibility of car bumper. However. To predict the critical point. or even a hood in some cases. material properties as well as boundary and loading conditions can produce this scatter in the result. Some energy may be observed for such members. Research from the American Iron and Steel Institute on bumper compatibility stated that the difference in heights and weights between these two types of vehicles (and indeed averagesized cars and trucks) creates an advantage for the heavier and/or taller vehicle when in a collision. geometry. Engineers today emphasize robust behavior of the energy-dissipating structure. Hence. is not. A bumper is designed to absorb the energy of a low speed impact with another vehicle. the bumper will sustain less damage and .1 PARAMETER CONSIDERED Basically in car collisions.Distributes to all the part during the analysis. loading and boundary conditions. So they must very wall in decide the variation in the material. CHAPTER 2 LITERATURE REVIEW 2. Axially loaded members will normally dissipate a substantial part of the energy during a front collision. We will analysis how this parameter can effect and to reduce energy dissipation and thus to prevent more damage during the collision [5]. the automotive industry uses finite element analysis in order to reduce the lead time to develop a new product and cost. members are loaded axially and by bending or a combination all of that. When a bumper strikes an object that is not designed for impact. which normally collapse by folding and bending of the plate elements composing the component. Small variation in geometry. most of energy is dissipated by body deformation. ii. But the things is depending on the type of collision. while an incompatible structure such as a headlight. Electrical energy carried to the cars from the grid is converted to kinetic energy. Some bumper use energy absorbers or brackets and others made with foam cushioning material.3 GEOMETRY Bumpers are structural components installed to reduce physical damage to the front and rear ends of a passenger motor vehicle from low-speed collisions. Each car has a large rubber bumper all around it. grille. trunk. the relative displacements representing stiffness performance are defined and examined. which prolongs the impact and diffuses the force of the collision. Bumper car rides are designed so that the cars can collide without much danger to the riders. fuel. The function is when a low speed collision occurs.inflict much more damage on the soft item. the bumper system absorbs the shock to prevent or reduce damage to the car. The car bumper is design to prevent or reduce physical damage to the front car. rubber or plastic that is mounted on the front and rear of passenger car. Damage and protection assessments are the commonly used design criteria in bumper design. 2. exhaust and cooling system besides the engine. For damage assessment. However. conventional bumper analysis through FEM outputs a constant . The bumper cars run on electricity. carried by a pole on the back of the car that leads up to a wire grid in the ride's ceiling. At the protodesign stage for a new car. Bumpers need to hit each other squarely to serve their purpose 2. finite element (FE) analysis is often utilized to predict the stiffness of a bumper. aluminum.2 FUNCTION A bumper is a shield made any of material like steel. It is also design to protect the hood. some of which is converted to heat. This grid carries the electricity that runs the car. It is not safety feature intended to prevent or mitigate injury to occupants in the passenger cars. All vehicles made by BMW Group. Isuzu. Mazda. then the bumpers of each vehicle are not going to behave optimally. Having considered all of these facts. But what is compatible? The AAM defines compatibility as having the majority of the Primary Energy Absorbing Structure within sixteen to twenty inches of the ground . Subaru. The uncertainties are assumed to be the tolerances of thicknesses. Then.stiffness even though the stiffness has some distribution due to uncertainties. Nissan. Under this uncertain condition. Honda. The height disparity can cause unnecessary damage to the lower vehicle and. the displacements representing stiffness are calculated by approximate statistics and by worst-case analysis. Suzuki. Ford Motor Company. Toyota and Volkswagen will be compatible (they will also have a variety of other safety features per this agreement). a robust design is determined by design of experiments (DOE) using the orthogonal array strategy to find the design having a minimum weight of bumper within the stiffness constraints Steel can be used to effectively absorb impacts. more importantly. but when the impact structures are set at different heights and the bumpers do not hit each other squarely. the Alliance of Automobile Manufacturers has voluntarily agreed to alleviate Vehicle Incompatibility all together by 2009. Hyundai. Mitsubishi. Kia. General Motors. DaimlerChrysler Corporation. the occupants of the lower vehicle. or high-speed impacts from the front or rear of the vehicle. Numerous designs come equipped on .Figure 4: Cross section of the bumper system technology Car Bumper Components Automobile car bumpers have the important function of lessening low. Bumper Brackets and Support-Brace Rods Bumper brackets come in a variety of shapes and sizes for the different makes and models. with large-diameter bores and coarse threads. Spacers and Washers Sometimes called bumper "lug nuts. Some vehicles can have as few as four mounting bolts." the mounting bolts used for securing the steel bumper frame to the chassis. stretches from one side of the vehicle to the other. made of solid steel rod. Typically made of high-tensile steel. Yet they all serve the same function: protecting the occupants of the vehicle from traumatic shock during a collision or lessening body damage to the vehicle by absorbing collision force. making it the largest and heaviest piece of all the bumper components. Cast of angular steel. whereas heavier trucks might have four.various makes and models with different components and features. On older vehicles. Bumper support rods. Some bumpers have extremely technical features and designs. the bumpers were designed to crush completely upon impact. Some cars have two large adjustable brackets on each end. the bolts have thick spacers and locking washers to secure them in place. they had extremely heavy construction and often had chrome plating. typically made of steel. Bumper Frame The bumper frame. They . serving as the main impact component. the brackets connect the bumper frame to the vehicle chassis frame. have extremely heavy construction. The bumper frame sits between the vehicle chassis and the outside bumper cover. Mounting Bolts. while others might have up to 10 or 12. connect the chassis frame to the outside ends of the bumper frame and serve as extra braces. Constructed of pliable. Bumper Trim Strips Instead of using protruding solid bumper guards. Some bumper shocks have spring-loaded tubes that allow high impact. where the bumper end can become crushed or forced inward. some car and heavy truck bumpers come equipped with inset bumper trim strips constructed of high-impact polyethylene . The entire bumper can travel backward with the impact and rebound back into position. the bumper guards bolt to the bumper frame---usually with two bolts. high-impact plastic or polystyrene. usually two rectangular rubber blocks that sit near each of the bumper's outer ends. They can incorporate thick fiber pads. allowing them to rebound when struck.guard against outside angular impacts. Some bumper shocks function with gas or hydraulic-operated tubes. rubber bushings. Bumper guards extend outward from the bumper surface as much as 4 to 6 inches. performing the same function as the spring-type bumper shock. Crush Cans and Absorbers Crush cans and absorbers function as impact dampeners that mount between the bumper frame and the chassis. Their design allows them to crush or give upon impact. serve as the first impact components on the bumper. allowing the bumper frame to flex inward with minimal damage. Bumper Guards Bumper guards. solid rubber. which ensures that they make contact with an object before any other bumper component. instead of using the crush can or absorber. . Bumper Shocks Many foreign-make and newer vehicles come equipped with shock tubes mounted between the bumper and the chassis. Extending 1/2-inch or so outward from the bumper face. Bumpers protect the vital components on your car by reducing collision damage. along with mounting holes for license plate brackets. usually have one-piece designs that bolt or screw onto the bumper frame. Bumper Covers Bumper covers. . and sometimes match the color of the vehicle. or consist of solid. constructed of high-impact plastic or rubber.plastic. usually bisecting a chrome bumper through the middle. . They can be insulated with foam. They also serve as decorative trim pieces. molded pieces. The trim strip extends from one end of the bumper to the other. the trim strip makes first contact with any object. Primarily designed to serve as the bumper’s decorative outside covering. they provide a minimal amount of impact protection. protecting the finish of the bumper. this vital component of your vehicle plays an integral role in modern transportation safety. . What Are Car Bumpers Made Of? Although the makeup of car bumpers has changed over the years. Some bumpers have mounting holes and brackets for lower turn signals and fog lamps. They serve as the covering or outer shell of the entire bumper surface. . Importance Bumpers protect important equipment on your car such as headlights. bumpers sometimes incorporate polypropylene foam or formed thermoplastic. fiberglass composite. In addition to crushable brackets and a bar. car bumpers are made of a plastic cover reinforced by a bar made of steel. hood and exhaust and cooling systems. some are designed for style. These additional components act as spacers between the bumper and bar. Types While most bumpers have a standard design to protect important components on a car. These components are all expensive to replace. This emphasis on style often reduces a bumper's. taillights. resulting in decreased effectiveness in resisting damage during a crash. Materials Generally. The first car bumpers were made of metal beams attached to both the front and rear of a car for the purpose of protecting a car in a low-speed collision. plastic or aluminum. and a bumper can eliminate or reduce the costs of repairing them.History Frederick Simms invented the car bumper in 1901. Attributes The attributes of a good car bumper include geometry. not as energy absorbers. energy absorption and stability. These traits allow a bumper to line up flush with an opposing bumper in order to absorb any impact and maintain stability. these problems were primarily associated with the metallic components. because several calculations and test procedures for characterizing the mechanical properties of thermoplastics are very similar to those of metals. there is a growing awareness of the importance of stress analysis. . Hence.MATERIAL PROPERTIES The common use of the term stress analysis includes any kind of structural analysis. sporting. because a few types of behaviors of thermoplastic materials call for advanced techniques of analysis. Thus such stress analysis is also similar. material behavior. measured and used in a manner similar to those for metals. and construction industries. typically with the strength. About many years ago. and better methods of design and analysis continuously reinforce each other and lead to the optimum design of the product. stiffness and life expectancy of their products. No. are the thermoplastics very different from metals? The answer is yes and no. design engineers are 5 increasingly concerned about stress-related problems. Yes. because an effective analysis needs to bring together a thorough knowledge of the operating characteristic of the product. because such behaviors are encountered only in special applications of metals. In many years. Material properties of plastics such as elastic modulus. Likewise detailed stress analyses of plastic components are performed assuming linear elastic behavior. tensile strength and fracture toughness are understood. In the field of thermoplastics design. structural behavior and solid mechanics. plastics have been used for applications in load-bearing structural components in the automotive. Stress analysis has always been inter disciplinary. That is. Stress analysis is a vital activity in this process. From the point of view of stress analysis. aerospace. Structural plastics design is a field that is evolving in the same manner as did the aero-space and nuclear power industries. Many structural plastics design may be performed using the familiar strength of material approach. a sequence of products innovations. yield point. or even a hood in some cases. Research from the American Iron and Steel Institute on bumper compatibility stated that the difference in heights and weights between these two types of vehicles (and indeed averagesized cars and trucks) creates an advantage for the heavier and/or taller vehicle when in a collision. the bumper will sustain less damage and inflict much more damage on the soft item.PARAMETER CONSIDERED Basically in car collisions. loading and boundary conditions. the automotive industry uses finite element analysis in order to reduce the lead time to develop a new product and cost. So they must very wall in decide the variation in the material. which normally collapse by folding and bending of the plate elements composing the component. material Properties as well as boundary and loading conditions can produce this scatter in the result. A bumper is designed to absorb the energy of a low speed impact with another vehicle. members are loaded axially and by bending or a combination all of that. Engineers today emphasize robust behavior of the energy-dissipating structure. while an incompatible structure such as a headlight. Bumpers need to hit each other squarely to serve their purpose. is not. When a bumper strikes an object that is not designed for impact. Hence. We will analysis how this parameter can effect and to reduce energy dissipation and thus to prevent more damage during the collision. Axially loaded members will normally dissipate a substantial part of the energy during a front collision. . But the things is depending on the type of collision. Some energy may be observed for such members. geometry. most of energy is dissipated by body deformation. Small variation in geometry. the bumper system absorbs the shock to prevent or reduce damage to the car. The failure analysis of composite materials was the next comparison of the experimental measurement with numerical simulation [2]. This grid carries the electricity. rubber or plastic that is mounted on the front and rear of passenger car. grille. 20. The comparison of experimental and numerical values of failure force are shown in Table.05 mm. The experimental setup scheme is illustrated in Fig. aluminum. The function is when a low speed collision occurs. some of which is converted to heat. The stripes properties where: length 105 mm. A transverse displacement of the plate u(t) was Measured directly under the point of impact. It is also design to protect the hood. . Three stripes were made.FUNCTION A bumper is a shield made any of material like steel. It is not safety feature intended to prevent or mitigate injury to occupants in the passenger cars. The Displacement was measured by a laser sensor optoNCDT by Micro-Epsilon. aluminum. 25 mm and fiber orientation 0 (A00). which prolongs the impact and diffuses the force of the collision. 5. Electrical energy carried to the cars from the grid is converted to kinetic energy A bumper is a shield made any of material like steel. The bumper cars run on electricity. Fig. trunk. 45 (A45) a 90 (A90). Bumper car rides are designed so that the cars can collide without much danger to the riders. rubber or has a large rubber bumper all around it. exhaust and cooling system besides the engine. 6. The car bumper is design to prevent or reduce physical damage to the front car. carried by a pole on the back of the car that leads up to a wire grid in the ride's ceiling. Some bumper use energy absorbers or brackets and others made with foam cushioning material. Experimental measurements A steel impact or was dropped from the height of h = 300 mm on a composite plate which was clamped along one edge was measured. see Fig. width 15. Each car That runs the car. fuel. thickness 1. 10 mm from the edge of the plate. 4 bellow. b) actual photograph from measurement (1 – tube fixture. Experimental measurement: a) experimental schema. 3 – composite plate. 2 – impact or guide tube.\ Fig. 6. 4 – optoNCDT laser sensor) . 9. four different simple geometry bumper reinforcement profiles were proposed as shown in Fig. The connection is Rigid and realized by so-called tied elements. The goal is to achieve the same. height and curvature of bumper are Similar. eventually better.1.Design of new composite bumper reinforcement In this part new composite bumper reinforcement is proposed. The aim was to keep the basic shape of the bumper reinforcement the same as in the case of the steel bumper – it means the length. mechanical behavior of the bumper reinforcement because the steel reinforcement shows fracture during RCAR test as discussed below. Stiffness analysis For this stiffness analysis. Afterwards. 6. a large strain damage analysis and a weight comparison of selected bumper reinforcements are performed and the corresponding weights are compared.profile . It is compared with original steel bumper reinforcement by means of stiffness analysis. In the next step the stiffness analysis is performed. The connection between the reinforcement and the deformable element is not investigated. At first. the composite structure lay-ups of both profiles B and D were modified to [0. 10. . 13.. 11.Fig. 6. i. 12) by a prescribed displacement. the lay-up of the composite structure was proposed as [01. 90.2. 10. 0] in the next step and so the new total composite thickness was 7. they were not taken into consideration in the next simulations. The complete results from Stiffness analysis can be found in [1]. ±30. To further improve the designs. ±30. Stiffness analysis The stiffness test is displayed in Fig. which was pushed against the bumper reinforcement and the deformable element. ∓ 30. This composite structure did not reach stiffness improvement in comparison with original steel bumper reinforcement (see [1]). 0] and the total composite thickness was 6 mm. Damage analysis The testing was realized with a rigid barrier. shift of the barrieris 40 % of the maximum width of the car without mirrors.6 mm. ∓ 30.2. The results are displayed in Fig. It can be seen that the modified profiles are now stiffer than the original steel structure. ±30.e. The displacement of the bumper reinforcement is evaluated under the steel cylindrical position. therefore. (see Fig. Steel cylindrical ―impact or‖ is pushed into the bumper reinforcement with a force of 1 kN. The new results are displayed in Fig. The parameters of the simulation barrier are equal to the barrier used in RCAR tests as introduced in section 2. ∓ 30. 90. The profiles A and C showed low stiffness values and. rigid barrier with an inclination of 10 degrees. Damage of composite reinforcement in simulation time 20 ms .Fig. Damage test Fig. 13. 12. before fracture . see Fig. the com.Fig. which does not demonstrate a good damage behavior of the bumper reinforcement. This means that the loading is still transferred to the deformable element (see Fig reinforcement also shows certain fracture on the edge as shown in Fig. 14. 14. 2) which is necessary feature for a well designed bumper reinforcement. 15. The maximum value of damage in the simulation is about 60 % (maximum dmax value in the whole model). The modified profile D proved to be the best of all tested profiles. The fracture initiation on the edge of modified profile B The analysis revealed fracture on the edge of the profile B. Therefore. The original steel bumper posite profile D proved to be a suitable replacement for the original steel structure from both the stiffness and damage point of view. The comparison shows a great mass reduction of the bumper reinforcements with use of the composite materials – up to 78 % in the case of best profile D. Table 6. Mass comparison between original steel bumper reinforcement and composite bumper reinforcements is displayed in Tab. The mass was calculated from elements volume and material density.14 1.45 1.6. Fracture on the original steel bumper reinforcement The main advantage of the new bumper is the mass reduction. 15.63 1.94 .89 1. Bumper reinforcement mass comparison Material Mass original steel composite profile A modified composite profile B composite profile C modified composite profile D [kg] 8.Fracture Fig. This problem has not been involved in the numerical model yet. moreover. Acknowledgements . The main part of the work is focused on the design of a new composite bumper reinforcement with the aim to maintain or improve its mechanical properties while reducing the mass. a great mass reduction could be achieved with the use of the composite structure.Conclusions The work is dedicated to the simulation of car bumper behavior according to prescribed safety procedures. The numerical models for PAM-Crash software using shell elements and Ledev`eze model for the composite material are validated by experimental measurements. the matter of price and damage of the reinforcement due to composite material delamination must be further inspected. The damage analysis proved one of the profile to be a suitable replacement for the original part as it showed no fracture and. However. The connection between the reinforcement and the deformable element was also not resolved in this work since it is rather a technological issue. four composite profiles are proposed and tested using stiffness analysis performed according to RCAR specification. After modification of the material structure. Afterward. two profiles are found to have greater stiffness that the original steel structure and they are selected for latter damage analysis. . Front impact [on-line]. URL: <http://www. pp.org/index. (in Czech) .htm>. collision. Brno. Progressive damage of unidirectional composite panels. URL: <http://www.rcar..com/tests/frontimpact. [6] Vlk. University of West Bohemia. Rcar homepage [on-line]. 2008. 2008. 243 pp. Solver Notes Manual. 25–44. [5] The official site of the European New Car Assessment Programme.aspx>.. 1. 42. biomechanics. ESI-Group. structure. Journal of Composite Materials. Car body : ergonomics.References [1] Kleisner. 2008-20-05]. V. [3] PAM-CRASH 2007. passive safety. materials. Zemˇc´ık. [cit. ISBN 80-238-5277-9. F. Diploma thesis. Paris. (in Czech) [2] Laˇs. 2008-20-05]. [4] Research Council for Automobile Repairs. [cit. Publisher Vlk.. V. Design of composite car bumper. No.euroncap. R. Vol. 2000..