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# Glossary of Terms

Acceleration:
Acceleration is a vector quantity that specifies the time rate of change of velocity.

Amplitude:
Amplitude is the maximum value of a sinusoidal quantity (i.e. acceleration, displacement).

Center of Gravity:
The point of support at which a body would be in balance.

Damping:
Damping is dissipation of energy in an oscillating system. Limits maximum amplitude at isolator natural frequency.

A decade is the interval between two discrete frequencies having a basic frequency ratio of ten. For example, frequencies of 7 Hz and 70 Hz are said to be one decade apart.

Deflection:
Deflection is the distance an elastic body or spring moves when subjected to a static or dynamic force. Typical units are inches or mm.

Displacement:
Displacement is the change of position of a body, usually measured form the mean position of rest. Common units are inches (double amplitude) or mm (double amplitude). Displacement is related to acceleration by frequency.

Elastomer:
A generic term which encompasses all types of rubber, natural or synthetic. There are numerous families of elastomers. The type of elastomer chosen for any application depends on the environment in which the elastomer will be used.

Forced Vibration:
Forced vibration is the vibration resulting from the application of an external periodic force.

Foundation (Support):
A foundation is a structure that supports the gravity load of a mechanical system. Fabreeka International, Inc.

Fragility:
Fragility is the amount of shock or vibration which a piece of equipment can withstand. Isolation systems are designed or selected to limit the transmission of forces to the stated fragility.

Free Vibration:
Free vibration is the periodic motion occurring when an elastic system is displaced from its equilibrium position.

Frequency:
Frequency is the number of times the motion repeats itself per unit of time. (The unit cycle per second is called Hertz (Hz.))

Isolation:
Isolation is a reduction in the capacity of a system to respond to an excitation. This is attained by the use of a resilient element between the equipment and mounting surface.

Mass:
Weight in pounds divided by the gravitational constant, (g=32.2ft/sec2 or 386 in/sec2)

Natural Frequency:
Natural frequency is defined as the number of cycles of oscillation that occurs in a time period when moved from its normal position and allowed to vibrate freely.

Octave Band:
An octave is the interval between two discrete frequencies having a frequency ratio of two. For instance, frequencies of 25 Hz and 50 Hz are said to be separated by one octave.

Periodic Motion:
Periodic motion is a motion that repeats itself at definite intervals of time.

Random Vibration:
Random vibration is vibration whose magnitude is not specified for any given instant of time.

Resonance:
Resonance occurs when the frequency of excitation is equal to the natural frequency of the system. When this happens, the amplitude of vibration increases and is only limited by the amount of damping present in the isolation system.

Resonant Frequency:
Resonant frequency is a frequency at which resonance exists.
Fabreeka International, Inc.

Shock:
Shock is a transient condition where the equilibrium of a system is disrupted by a sudden applied force or increment of force, or by a sudden change in the direction or magnitude of a velocity vector.

Shock Absorber:
A shock absorber is a device which dissipates energy to modify the response of a mechanical system to applied shock.

Shock Isolator (Mount):
A shock isolator is a resilient support that tends to isolate a system from shock motion (excitation).

Shock Pulse:
A primary disturbance characterized by a rise and decay of acceleration in a relatively short time. Shock pulse is generally shown as a plot of acceleration vs. time.

Sinusoidal Vibration:
Oscillations in which motion is periodic with time in the form of a sine curve. Rotating equipment generate vibrations which are frequently considered as sinusoidal.

Spring Rate/Stiffness:
The force required to deflect an isolator a unit distance. Stiffness is the slope of a curve showing force on the Y-axis and deflection on the X-axis. Typical units are pounds/inch.

Steady state vibration exists in a system if the amplitude is a continuous periodic quantity.

Structural Damping:
Reduces the vibration of resonating surfaces that radiate noise. Damping is accomplished by affixing a material directly to the vibratory surface. This material converts the mechanical vibration energy into to a minimal amount of heat energy.

Transient Vibration:
Transient vibration is temporarily sustained vibration of a mechanical system. It may consist of forced vibration.

Transmissibility:
Percentage of vibratory force or motion transmitted to its support.

Velocity:
Velocity is a vector quantity that specifies the time rate of change of displacement with respect to a reference time. Fabreeka International, Inc.

Vibration:
Vibration is a force which oscillates about some specified reference point. Vibration is commonly expressed in terms of frequency such as cycles per second (cps), Hertz (Hz), cycles per minute (cpm) or (rpm) and strokes per minute (spm). This is the number of oscillations which occurs in that time period. The amplitude is the magnitude or distance of travel of the force.

Vibration Isolator:
A resilient support that tends to isolate a mechanical system from steady state excitation.

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