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Conversion of structural damping to equivalent viscous damping for pbush elements

Experimenter
Experimenter

Hi,

I have a frequency dependent damping values for PBUSH(GE).If i want to convert the structural damping v/s frequency data to equivalent viscous data in the pbush entry for different frequencies is it possible??

1 REPLY

Re: Conversion of structural damping to equivalent viscous damping for pbush elements

Experimenter
Experimenter

It is wery rough estimation, but lets see...

For single mass problem i. e. mass oscilation on spring and damper your damping coefficient GE=2*C/C0, where C is viscous damping of pbush, and C0 is critical damping. C0=(k*m)^0,5 - k is the spring stiffness, m is the mass attached to spring. As you see in this case your damping depend from attached mass of structure. For example if you have box, supported by four springs at four corners, you can divide mass of box by 4. And this equations are true for TX, TY, TZ damping, for rotarional components you need to search rotational analogy.