I am seeking the natural frequencies of a stationary disc (modeled in the r & theta plan) through a home-developed Matlab code, and then compare the results with Abaqus. The disc is fixed from the inner surface and is allowed to deform freely at its outer surface.
What I get is repeated values of certain frequencies that are unique in Abaqus. Most of the frequencies are not obtained. Any recommendations for such a problem?
In the attached two images, I am showing the repeated results of my FEM Matlab code and Abaqus output. As seen, the first natural frequency is repeated around 60 times. However, it's only appearing for one time in Abaqus results.
(I am using a Q8 element with two degrees of freedom at each node. Thickness is unity.)
Inner radius: 0.2m
Outer radius: 0.5m
Density: 2800 kg/m3
Elastic modulus: 200GPa
Poission's ratio: 0.3
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.
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