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Continuity problem for shell type physics
Posted 10 feb 2020, 07:45 GMT-5 Acoustics & Vibrations Version 5.5 3 Replies
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Dear Comsol community,
I am creating a structural model of two plates connected through a frame for which it is important to use only surfaces since the thickness is small and the model needs to have minimum DOFs. The problem I encounter is that the continuity for shell physics can only be defined for edges. Where on the contrary the contact pairs are properly defined . To have a better view I can say that I use asssembly and with a bit of correction the model pairs are recognized. I am uploading the model for the ones who are interested to provide some information how to solve this problem.
Thank you for your time
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Hi Theodore,
The reason Continuity is not available for boundary-to-boundary in the Shell interface is that the degree of freedom values should not be equal. Thickness and offset must also be taken into account.
You can solve your problem in two different ways. One is to use contact with adhesion, and having the adhesion being always active. The other one is to connect the degrees of freedom using an extrusion coupling operator mapping from one boundary to another. You then prescribe the displacements and rotations on one side in terms of those on the other. Rotations should be equal, while the displacements will also contain terms from the mid-surface distance and rotation.
The situation you describe is however interesting. We will look into adding a more natural 'Continuity-like' condition for modeling it.
Regards,
Henrik
Henrik Sönnerlind
COMSOL
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Hej Henrik,
Appreciate the reply. I tried the approach described related to adhesion. Thing is, the model for an eigenfrequency analysis shows mode shapes that are separate. For each eigenfrequency only one domain from the whole assembly has a mode shape. It seems as the eigenfrequencies are calculated for each part separately. I used extra pairs so as to restate previous continuity from each domain union but with or without them the results remain the same. I believe I have checked all parameters so could you provide your opinion about it.
Thank you for your time
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Hi Theodore,
When you combine contact with eigenfrequency analysis, you should run an Eigenfrequnecy, Prestressed study in order to get the correct linearization point for the eigenfrequency analysis.
Regards,
Henrik
Henrik Sönnerlind
COMSOL