APPLIED MECHANICS LAB (MEC424) – DYNAMICS OF MACHINES LABTITLE Forced Vibration Experiment – Resonance of Spring-Dashpot System with Damping ABSTRACT The experiment is study the for the spring-dashpot system where we to study the effect of damping on the system. Through the experiment, we are to study the damped frequency and relate it to the natural frequency as well study the occurrence of resonance and its effect on the system. 1 .......APPLIED MECHANICS LAB (MEC424) – DYNAMICS OF MACHINES LAB TABLE OF CONTENTS 1.................................................................................................. 4 3.................. 3 2..........1 Objective .................................................... 3 3.....................................0 Theory ....................................................................................................... 6 6..............................................................................0 Apparatus ................................................................................................................................. 7 7........... 5 5..................................0 Experimental Procedure ........................... Results and Conclusion 8.............................................0 Introduction.............................................................0 List of Figures ........................................................................................0 Discussion.............0 References 2 ....... 4 4..........................0 List of Table ........... APPLIED MECHANICS LAB (MEC424) – DYNAMICS OF MACHINES LAB 1.0 LIST OF TABLES Table: Experimental data 2.0 LIST OF FIGURES Set up of apparatus Dimension of the beam page 6 page 6 3 . 0 INTRODUCTION Forced vibration is vibration that takes place under the excitation of external forces. Resonance will occur if the frequency of excitation coincides with one of the natural frequencies of the system and dangerously large oscillations may result. The system will vibrate at the excitation frequency when the excitation is oscillatory. bridges. The failure of major structures such as buildings.1 OBJECTIVE OF THE EXPERIMENT The objective of the experiment is to determine the resonance of spring-dashpot system in different damping. 4 .APPLIED MECHANICS LAB (MEC424) – DYNAMICS OF MACHINES LAB 3. or airplane wings is an awesome possibility under resonance. 3. is the damped frequency and is the natural frequency of the system. This is because. resonance will occur if the frequency of excitation coincides with one of the natural frequencies of the system and dangerously large oscillations may result. it resists motion via viscous friction. The large oscillations may reach the maximum amplitude of the oscillation for a certain body thus may result in failure of member of the system. The resulting force is proportional to the velocity. slowing the motion and absorbing energy.APPLIED MECHANICS LAB (MEC424) – DYNAMICS OF MACHINES LAB 4. As for the damper. 5 . It is commonly used in conjunction with a spring. Where. Both are in (rad/s) in unit. the member may reach the maximum deformation it can attain and soon will fracture. The relation of rotational frequency during resonance is. but acts in the opposite direction. As they are equal. the resonance will occurs and result in maximum amplitude for the oscillation.0 THEORY As stated in Introduction section. APPLIED MECHANICS LAB (MEC424) – DYNAMICS OF MACHINES LAB 5.mm) Mechanical recorder Unbalance exciter Damper Control Unit (TM150) The dimensions of the beam are as follows: Width Length Thickness Thickness.0 APPARATUS Frame Beam Spring (k=3. w = 25 mm Length.0 N. h = 12 mm Width. L = 700 mm 6 . The mechanical recorder is then tested. As the graph paper is ensured in grip. The control unit is turned on. Data for each 0. 6. range of reading needed to be taken is tabulated. 8. fn of reading is set. to ensure if the graph is being recorded clearly and properly. Before any reading is taken. 7 . (It is advisable to use blunt-tip pen or a gel pen). With no damper. 5. damper (needle closed) is positioned at 150 mm of the beam. Once we roughly know at what frequency the amplitude is at maximum. 2.0 EXPRIMENTAL PROCEDURE 1. 3. Steps 6-8 is repeated with damper (needle open) is positioned at 150 mm of the beam. so that. 4. and damper (needle closed) is positioned at 550 mm of the beam. The excited oscillation of each set frequency is plotted on the graph paper by the mechanical recorder each. the maximum amplitude at what frequency is first predicted as the beam is forced oscillation by the exciter.APPLIED MECHANICS LAB (MEC424) – DYNAMICS OF MACHINES LAB 6. the apparatus is set up.5 Hz is taken. The graph paper (which attached in roll on the mechanical recorder) is slotted into the holder. the unbalance exciter is controlled its frequency by the control unit. Precaution: Each graph plotted needs to be labeled every time before plotting the next graph. First. 7. a pen is fixed in the graph pointer slot. ± of 2 Hz is taken from the predicted natural frequency. 9. later on will not be confused or mistakenly taken.