Guidelines for damping schedule of flexbody?

Question

The default Adams CRATIO for a flexbody is the following:

1% damping for all modes with frequency lower than 100. 
 10% damping for modes with frequency in the 100 to 1000 range. 
 100% critical damping for modes with frequency above 1000.

Lets say I run a flexbody with a 200Hz cutoff frequency in the EIGRL card. What would be the best way to adjust the default damping schedule to reflect my flexbody? Running with a flat X% damping percentage doesn't seem to run well as the residual vectors add a lot of high frequency noise to the sim.

Jan Sotnik · Accepted Answer

Hello Michael,

say, for your NVH study you are interested in frequencies up to 6 kHz then apply modal damping of 0.02 (2% of critical damping) up to that frequency and then step up to 1.0 of modal damping (critical damping) over some frequency range. My tutor used to say, have at least 6 modes over that range if possible, to let solver have a smooth transition from low damping to critical damping.

STEP(FXFREQ, 6.0E3, 0.02, 1.0E3, 1.0)

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