Vibration Isolation and Base Excitation

vibration isolation and it's objectives

1. PRESENTATION ON “VIBRATION ISOLATION AND BASE EXCITATION” DYNAMICS OF MACHINERY SUBMITTED BY: HIMANSHI GUPTA ( 140120119057)/ ME/A2 GUIDED BY : PROF. SAMEER RAVAL ( 2161901) GANDHINAGAR INSTITUTE OF TECHNOLOGY

2. INTRODUCTION Vibrations are produced in machines having unbalanced masses or forces High vibration levels can cause machinery failure, as well as objectionable noise levels A common source of objectionable noise in buildings is the vibration of machines that are mounted on floors or walls

3. SOURCES OF VIBRATION EXAMPLES  Rotating and reciprocating Unbalance Pumps, Turbines, Electric Generators, Compressors Misalignment and wear of tools Manufacturing – machining   Seismic Vibrations Buildings, Bridges, Chimneys and Cooling Towers Wind (Pressure loading) Tall Structures Small magnitude vibrations E.g. Pedestal and vehicular traffic Sensitive systems like optical instruments, microscopes, Nanofabrication  Impact and shock loads Hammer and presses, in vehicles due to bumpy/ irregular nature of road

4. VIBRATION ISOLATION Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibration The effectiveness of isolation is expressed in terms of force or motion Lesser the amount of force or motion transmitted to the foundation greater is said to be the isolation

5. TYPES PASSIVE VIBRATION ISOLATION R efers to vibration isolation or mitigation of vibrations by passive techniques such as rubber pads or mechanical springs ACTIVE VIBRATION ISOLATION Also known as electronic force cancellation Employs electric power, sensors, actuators, and control systems for vibration isolation

6. OBJECTIVES The basic objectives of vibration isolation are: To protect the delicate machine from excessive vibration transmitted to it from its supporting structure To prevent vibratory forces generated by machine from being transmitted to its supporting structure

7. MECHANISM OF VIBRATIONS TRANSMISSION SOURCE PATH RECEIVER

8. VIBRATION ISOLATORS The vibration isolation may be obtained by placing materials, called vibration isolators in between the vibrating body and the supporting foundation or structure

9. PASSIVE VIBRATION ISOLATORS METALLIC SPRING ISOLATION PAD ISOLATION HANGER PNEUMATIC ISOLATOR

10. ACTIVE VIBRATION ISOLATORS FRAME MOUNTABLE ACTIVE HARD-MOUNT PIEZOELECTRIC VIBRATION CONTROL SYSTEM ACTIVE VIBRATION ISOLATION TABLE

11. IMPORTANT CONSIDERATIONS WITH VIBRATION ISOLATOR SELECTION 1) Machine Location : As far away from sensitive areas as possible And on as rigid a foundation as possible 2) Proper sizing of isolator units : Correct stiffness Sufficient travel to prevent bottoming out during shock loads, or during system startup and shutdown 3) Location of isolators : I solators should be equally loaded, and the machine should be level

12. 4) Stability : Sideways motion should be restrained with snubbers The diameter of the spring should also be greater than its compressed height 5 ) Adjustment : S prings should have free travel, should not be fully compressed, nor hitting a mechanical stop 6) Eliminate vibration short circuits : A ny mechanical connection between machine and foundation which bypasses the isolators, such as pipes, conduits, binding springs, poorly adjusted snubbers or mechanical stops 7) Safe operation : To avoid a spring break, you must have mechanical supports on which the machine can rest without tipping

13. VIBRATION ISOLATION MATERIALS The materials normally used for vibration isolation are rubber, felt, cork, metallic springs, etc. These are put between the foundation and the vibrating body

14. RUBBER FELT CORK METALLIC SPRING

15. BASE EXCITATION It models the behavior of a vibration isolation system The base of the spring is given a prescribed motion, causing the mass to vibrate This system can be used to model a vehicle suspension system, or the earthquake response of a structure

16. FBD OF SDOF BASE EXCITATION SYSTEM …(1)

17.   For a car , The steady-state solution is just the superposition of the two individual particular solutions ( system is linear) (1)

18. PARTICULAR SOLUTION (SINE TERM) With a sine for the forcing function,

19. PARTICULAR SOLUTION (COS TERM)   With a cosine for the forcing function , we showed

20. MAGNITUDE X/Y Now add the sin and cos terms to get the magnitude of the full particular solution

21.  EFFECT OF SPEED ON THE AMPLITUDE OF CAR VIBRATION

22. Thank You 