Available Techniques to Determine Damping Coefficients for Landing Gear

[SwimBikeRun4342]

Hi all:

I have a question regarding the use of FEA Software to determine damping coefficients. Basically, I want to find the damping of a skid landing gear via FEA Software, or any other readily available computational tool. I'm aware that the only physical way to determine damping would be through an actual experiment.

However, for a given CAD model in Abaqus (or any equlivialnt FEA software), is there an accepted technique to approximate the damping of the structure? Could I edit the Rayleigh Damping Coefficients such that the dynamics fit a certain curve? But this is dependent on whether or not I can find legitimate data plots/curves that describe the motion. I'm basically wondering if there is an accepted method to find damping coefficients of a skid landing gear without doing any physical experimental work.

In other words, I only want to obtain the damping on this FEA model in order to obtain damping coefficients for a completely separate code that I'm writing. Is this feasible?

Thank you

 

[GregLocock]

Pretty much, no.

Typical %critical damping for low frequency modes are around 0.1% for welded or solid steel, 0.3 for ditto aluminium, and say 1% for bolted steel assemblies.

Any rubber pads, nylon washers etc etc will have a disproportionate effect on this, so for complete large assemblies 15% would be a lousy outcome (from the point of view of trying to fit mode shapes experimentally) , 5% is not unusual.





Cheers

Greg Locock


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