Modal analysis problems in Abaqus

[NTUCE]

Hello everyone,

I'm doing modal analysis in Abaqus (step type: frequency).

Yet the results seem to have some problems.

The picture below is mode 1 shape.

The result is wrong, it seems that most elements are not deforming.

Normally, it should be like this:

Boundary condition at the bottom: (fixed)

Constraint between inner part(finite element) and outer frame(infinite element): (tie)

I've checked everything, still couldn't find where the problem is.

Need your kind suggestion and guidance, thank you very much!

 

[FEA way]

It seems that some elements detach from the model. Make sure that all parts are properly connected, especially that perforated plate on top.

 

[NTUCE]

I've used "find contact pairs". This function works well. So I think all parts are attached together properly.

 

[FEA way]

This option is very convenient but sometimes doesn’t work as expected. Check warnings and sets generated by Abaqus, they should show you which nodes were connected by tie constraints and which weren’t.

 

[NTUCE]

I've checked surfaces generated by find contact pairs. They all look fine. No surfaces were missed, and they are all defined as surface to surface contact.

 

[271828]

Have you started with a simple model with known results? Something like a simply-supported beam made of these shell.