technical seminar-vibration isolators
TRANSCRIPT
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VIBRATION ISOLATORS
ByS. Vivek
07671A03A8
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Vibration is the oscillation of a rigid or elastic body that is created by the
transfer of energy from one body to another.
Transportation vehicles, portable devices and consumer electronics all
contain parts that are constantly in motion and subject to vibration.
The movement of these parts creates energy that radiates audible noise in
the form of vibration.
Vibration can damage sensitive equipment and reduce the reliability of an
otherwise durable product.
To avoid the possibility of damage and ensure proper performance for
the long term, sensitive components should be isolated from vibration
energy.
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Methods of Vibration Control
Avoid Resonance
Balancing /Control of Excitation Forces
Adequate Damping
Vibration Isolation
Vibration Absorber
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The transmission of vibratory motions or
forces from one structure to another may
be reduced by interposing a relatively
flexible isolating element between the two
structures. This is called vibration
isolation
Such systems are used extensively
to isolate machinery (industrial
and marine), civil engineeringstructures (base isolation in
building, bridges, etc.), and sensitive
components from the foundation/base.
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It is important to distinguish
between vibration dampingand
vibration isolation.
The dampingof a structural
mode consists in reducing the
response of the structure near the
corresponding natural frequency.
Isolation, on the other hand, consists in reducing the vibrationtransmission from one part of the structure (sometimes called noisy
side) to the other(quiet side): the reduction of the transmission
generally occurs in a large frequency region.
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Isolating the structures from the
vibrations is very important due to
1. To protect sensitive items, such as delicate electronic components,
from high environmental vibration levels.
2. To reduce the magnitude of the oscillatory forces transmitted to the
supports, when inertial or other forces are developed in a machine.
3. Sound generated due to vibrations
is to be in limits
4. Vibration of the buildings due to the
equipment present in them.
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Isolators act as springs that
deflect energy as vibrations
impact their surface and then
rebound to return the vibration
energy back towards the source.
Reducing structure-borne excitation can extend the life of
transportation vehicles, portable devices and consumer electronics
and prevent performance problems.
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Oscillating Force Fd is
internal to massM
Isolator has stiffness
K=Weight/Static Deflection()
Goal is to minimize the
transmitted force into the
building, Ft
Natural or Resonate Frequency of the oscillation
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SOURCE-PATH-RECEIVERMODEL
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Source: a mechanical or fluid disturbance, generated internally by the machine,such as unbalance, torque pulsations, gear tooth meshing, fan blade passing, etc.
These typical occur at frequencies which are integer multiples of the rotating
frequency of the machine.
P
ath: the structural or airborne path by which the disturbance is transmitted tothe receiver.
Receiver: the responding system, generally having many natural frequencies
which can potentially be excited by vibration frequencies generated by the
source. (M
urphy says the natural frequency of the system will always coincidewith an excitation frequency.
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Solutions in Source-path-recivermodel:
1. Relocate machine
2. Replace machine3. Change the operating speed
4. Balance rotating elements
5. Using isolator springs and/or inertia blocks
6. Change the natural frequencies of the system
7. Add structural damping
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1. Many isolation systems involve
center-of-gravity installations of
the equipment. That is, the
center-of-gravityof the equipment
coincides with the elastic center
of the isolation system.
2. Many equipment isolation systems
are required to be isoelastic. That is, the system
translational spring rates in all directions are the same.
3. Many pieces of equipment are relatively light in weight and Support structures are
relatively rigid incomparison to the stiffness of the isolators used to support and
protect the equipment.
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THANK YOU