Problems with Direct Steady State Dynamic Analysis Mode Deployment

[JimmyJazz13]

I have a simple Flat plate (shell) where I apply a ponctual force in the middle and analyze with Frequency and Direct Steady State Dynamic Analysis. When I apply Structural Damping, there seems to be problem with the results of some resonant mode (not all). Some mode seems to disapear. I look at history output or even Field output and for some mode, the displacement for the bias frequencies (frequencies very close to the resonant mode) increases close to the resonant mode, than for the frequency of the resonant mode, negligible displacement occur and the mode shape on the field output is very weird. Then for next bias frequencies after, the displacement start to be significant again with correct mode shape until it transition to a next mode.

Also, when I go to the right resonant frequency in the field output, as I said, displacement is negligible and mode shape is not correct, but when I activate the video of the mode, displacement explodes to very high values and mode shape is correct (for the video only).

Finally, when I diminish the structural damping, this phenomena seems to happen for fewer resonant frequencies, but still happen.

Any explanation why?

Thanks!!!

 

[JimmyJazz13]

Please help!!!!

 

[Mustaine3]

Hard to say. I'm also not an expert with damping.

Have you tried to do the same with mode-based SSD?