Acceleration is the rate of change of velocity with time, usually along a specified axis and usually expressed in “G” or gravitational units. It may refer to angular motion.
Amplitude is the maximum displacement from its zero-value position.
Compression when specified as a direction for loading is a deformation caused by squeezing the layers of an object in a direction perpendicular to the layers.
Damping the mechanism in an isolation system dissipates a significant amount of energy. This mechanism is important in controlling resonance in vibratory systems.
Disturbing frequency is the number of oscillations per unit time of an external force or displacement applied to a vibrating system.
Durometer (hardness) is an arbitrary numerical value, which measures the resistance to the penetration of the durometer meter indenter point; value may be taken immediately or after a very short specified time.
Fragility is the highest shock or vibration level that can be withstood without equipment failure.
“G” Level is an expression of the vibration shock acceleration level being imposed on a piece of equipment as a dimensionless factor times the acceleration due to gravity.
Isolation is the protection of equipment from vibration and/or shock. The degree (or percentage) of isolation necessary is a function of the fragility of the equipment.
Load deflection curve is the measured and recorded displacement of a mounting plotted versus an applied load.
Natural frequency is the number of cycles (expressed as Hertz or cycles per second) at which a structure will oscillate if disturbed by some force and allowed to come to rest without any further outside influence.
Random vibration is a non-sinusoidal vibration characterized by the excitation of a broad band of frequencies at random levels simultaneously.
Resonance vibratory system is said to be operating at resonance when the natural frequency of the disturbance (vibration or shock) coincides with the system’s natural frequency.
Set is the amount of deformation never recovered after removal of a load. It may be in shear or compression.
Shear when specified as a direction for loading is a deformation caused by sliding layers of an object past each other in a direction parallel to the layers.
Shock pulse is a transmission of kinetic energy to a system, which takes place in a relatively short length of time compared to the natural period of this system. It is followed by a natural decay of the oscillatory motion. Shock pulses are usually displayed as plots of acceleration vs. period of time.
Spring rate is the force required to induce a unit deflection of spring. A steel spring has a very linear relationship between force and deflection. Elastomeric springs may or may not be linear depending on the amount of deflection due to the load.
Static deflection is the deflection of the isolator under the static or deadweight load of the mounted equipment.
Transmissibility is a dimensionless unit expressing the ratio of the response vibration output to the input condition. It may be measured as motion, force, velocity or acceleration.