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PRESENTATIONON
“VIBRATION ISOLATIONAND
BASE EXCITATION”
DYNAMICS OF MACHINERY
SUBMITTED BY:HIMANSHI GUPTA (140120119057)/ ME/A2GUIDED BY:PROF. SAMEER RAVAL
(2161901)
GANDHINAGAR INSTITUTE OF TECHNOLOGY
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
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
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
TYPESPASSIVE VIBRATION ISOLATION • Refers 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
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
MECHANISM OF VIBRATIONS TRANSMISSION
SOURCE
PATH
RECEIVER
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
PASSIVE VIBRATION ISOLATORS
METALLIC SPRING ISOLATION
PAD
ISOLATION HANGER PNEUMATIC ISOLATOR
ACTIVE VIBRATION ISOLATORS
FRAME MOUNTABLE ACTIVE HARD-MOUNT
PIEZOELECTRIC VIBRATION CONTROL
SYSTEM
ACTIVE VIBRATION ISOLATION TABLE
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 :• Isolators should be equally loaded, and the machine should be
level
4) Stability :• Sideways motion should be restrained with snubbers• The diameter of the spring should also be greater than its compressed
height
5) Adjustment :• Springs should have free travel, should not be fully compressed, nor
hitting a mechanical stop
6) Eliminate vibration short circuits :• Any 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
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
RUBBER FELT
CORK METALLIC SPRING
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
FBD OF SDOF BASE EXCITATION SYSTEM
…(1)
• For a car,
• The steady-state solution is just the superposition of the two individual particular solutions
(system is linear)
(1)
PARTICULAR SOLUTION (SINE TERM)• With a sine for the forcing function,
PARTICULAR SOLUTION (COS TERM)
• With a cosine for the forcing function, we showed
MAGNITUDE X/Y• Now add the sin and cos terms to get the magnitude
of the full particular solution
EFFECT OF SPEED ON THE AMPLITUDE OF CAR VIBRATION
Thank You