Weird Issue about Modal Analysis on Plate Covering Thick Damping Layer

[JosephX]

I am now facing an uncertainty which is about a normal plate structure covering some thicker damping layers (thickness: relative to the thickness of the plate) during modal analysis (Natural frequency and Mode Shapes).

What I am actually modeling is that I dug out some materials from the plate making some hole-liked features on the plate and then placed the damping material in these hole-liked features. In Abaqus, I used Tie Contact to treat the contact between the plate and the damping layer. Actually, I used another way to avoid potential contact issue that I combined two parts, which are plate and damping layer, into one part and then make the partitions so I defined the material differently for two partitions. However, these two ways led to same issue.

Following the steps what I usually did in Abaqus for Modal Analysis. But for this case, some modes show the mesh of damping layer crashed and plate did not show any modes. I expect the reason could be that Young’s Modulus for damping layer is less two orders of magnitudes than plates’. In the mean time, I tried to decrease the thickness of the damping layer and then after this treatment the mode shape can now correctly show up but some few higher order modes were still crashed.

Do you have similar experiences for this? Any advice for me to make this simulation correctly in Abaqus? or this is a limitation for Abaqus? Thanks!

 

[JosephX]

This is what I got from the analysis. You can see how messy the damping layer is.

Actually, what I expect is this figure showing below. In fact, I did this after increasing Young's Modulus a bit of damping layer. In the mean time, it still has some modes which are crashed.

Thanks, if you have any idea for this.