The magnitude of the displacement from mean position of a deflection caused by vibration.
Interference frequency
f
Hz
Typically the rotational frequency of a machine
Frequency
f0
Hz
The number of vibrations in a freely oscillating system per unit of time (/second for Hz)
f0 = 1/2π√ (Kdyn/m)
Mass
m
Kg
The mass of the oscillating system
Spring force
F
N
The force exerted on or from a spring (or AV mounting)
Deflection
d
m
The deformation of a spring (AV Mount) from neutral position
Static spring stiffness
Kstat
N/m
The force in Newtons to compress the spring or mounting by 1m
Dynamic spring stiffness
Kdyn
N/m
Spring stiffness when an alternating force is applied
Tuning ratio
Z
-
The ratio between Interference frequency (f) and natural frequency (f0)
Interference force
Fs
N
The force transmitted to the base of an isolated machine
Impulse force
Fi
N
The force transmitted to the base of a rigidly mounted machine
Level of isolation
I
-
That part of the impulse force which is eliminated by the vibration isolation
Damping Coefficient
c
Ns/m
The linear viscous damping coefficient
Critical damping
ccr
Ns/m
The linear viscous damping at critical damping. i.e. no over oscillation after displacement
Damping factor
D
-
The ration between c and ccr
Reduction
R
dB
Isolation expressed in decibels R=20log(1/B)
Deflection
δstat
Mm
The static deflection for a spring = F/ Kstat
An essential difference between rubber and a steel spring is that the rubber material has an inherently high damping capacity built in.
This is particularly important for vibration isolation and shock absorption. When deformed and released, a wide hysteresis curve is generated showing a loss of energy as illustrated.
The lost energy is converted to heat which, in normal applications is readily dissipated.
