Hello all,

I'm running a Linear Dynamic Harmonic Analysis modelling a vibration test rig I'm using.

The problem I'm having is that when I try to use Modal Damping based on Material Properties I get the same results, every time I run the test.

When I use Modal damping not based on 'Compute from material damping' with a value of 0.005 I get a result that is close (enough) to my experimental results.

But I want to be able to vary the damping for different parts.

So all the parts have custom materials assigned, with a value for Material Damping Ratio. But it seems that no matter what I set that to (and Update All Components) it makes no effect on the results, they look the same as when I ran with a global value of around 0.02.

I expect I'm doing something wrong but I can't work out what it is...

Thanks in advance for any help offered,

Hi Doug: As far as I know, that option to "compute from material damping" is supposed to work. You might need to review each material property data sheet for each component and see if there's an entry at the bottom labeled "material damping ratio". I have noticed, some materials have "N/A" posted and I'm not sure what the software does with an N/A.