# Vibration Isolation Damping Coefficient

1. Apr 21, 2010

### p_j_whelan

1. The problem statement, all variables and given/known data
I am trying to solve how to select a vibration isolator for a machine to be mounted on a vibrating surface. I know the disturbance frequency, 22.5Hz and the mass of the machine is 40kg. I have selected some commercially available rubber isolators and subsequently know their stiffness but nothing else. Is there a correlation between the stiffness, natural frequency etc. to the damping coefficient. It is a single degree of freedom system so I know that omega(n) =sqrt(k/m).

2. Relevant equations
How do I determine the damping coefficient, C, if I want to determine the transmission of energy from one system to the other by as much as possible? Should the selected dashpots have a specified damping coefficient or can it be derived? Does the dampign factor depend on conditions and not a rating?

3. The attempt at a solution
I am led to believe that C^2- 4mk=0 where:
C = damping co-eff
m = mass of machine
k = stiffness of spring from which I can get a value for C, but is that not in units (kg*N/m) not Ns/m?

And from there, if I get value for C, can I just assume Cc is the same even though I would have to select a dashpot with that subsequent damping coefficient? I am really struggling if anybody could help.