Hello everyone,

I have a question regarding the modal damping option in the simulation studies. In linear dynamic analysis there are three options to set for the global damping:
 

I know, what Rayleigh damping is and also the theory about modal damping and that I can set it for each respective mode. I assume, that I put values here for the entire system so for example for a metal structure with joints 0.03 - 0.07 according to:
But I wonder about the option "Compute from material damping". Does anyone know, how exaclty this is done? I can specify the MDAMP (material damping ratio) in the properties of a material, but I do not know which value I should put here. Is it the equivalent viscous material damping ratio, I can also find in the literature or in the table given above, so for example 0.5 e-04 for aluminum?

And maybe someone has an idea, how exaclty the solver computes then the modal damping ratio from this material parameter. Regarding that, I only found out about "Composite Modal Damping", which seems to be the procedure for this option. However, the documentation is very short on the website. And also it says: "If you specify material damping ratio MDAMP to be m for all materials in the model, the equivalent modal damping ratio will be m for all modes." This confuses me, because it would mean that it directly uses the material damping ratio which would be too low for the entire system.

Thanks a lot for your help!