Can you share the corresponding Abaqus model (.inp)? Alternatively, the inner and outer diameter and the material properties (Youngs modulus E, Poisson ratio \nu and density \rho) are neeeded to compute the natural frequencies.

Nils Wagner

Thanks for your response. I have added the required info to the description of the question.

Just out of curiosity, why did you use the eight node plane stress element (CPS8R) ? What about out-of-plane modes?

In the case of an axially symmetric structure with the chosen boundary conditions, you will always get multiple/double eigenvalues.

Nils Wagner

I am working on a 2D problem; so I used the eight-node element. The current example is axially symmetric, but it is just for verification of my FEM Matlab code.

The problem I intend to solve is asymmetric.

Can you shed more light into your asymmetric problem?

I have attached the corresponding PERMAS model (.dat). The natural frequencies match perfectly.

Nils Wagner

Asymmetry may include load and material distribution.

How are natural frequencies match perfectly?

In the attached Matlab image, I am not getting similar results to those in Abaqus. Some natural frequencies are not obtained

I have compared PERMAS with Abaqus.

There seems to be a bug in your Matlab script, though.

You may get help if you also provide your Matlab script.

Nils Wagner, I have sent it to you in a message.