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solid to shell modelling

Posted Dec 30, 2022, 4:30 a.m. EST Version 6.1 3 Replies

Panson Poon
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I have a fully-solid model in component1. Its eigenfrequency results are used as a reference for the shell models.

The shell model in component2 is based on the solid. Boundaries are obtained using extract node. The eigenfrequency results of this shell mode are very different from the reference solid one.

Another shell model is created in component3. The vertical boundary is displaced intentionally in z-direction for 0.2 mm. Edge to edge connector node is then used to connect the vertical and horizonal boundaries. Eigenfrequency results of this second shell mode are closer to the reference.

If edge to boundary node is added to the first shell model (comp2), the result is improved. But it is still not as good as that of the second shell model.

Is there anything wrong in the first shell model? I suppose the two extracted boundaries are connected automatically by form union. We don't need to do any manual connection as that is done in the second shell model. Is the edge to edge/boundary connection necessary?

Thank you.

3 Replies Last Post Jan 10, 2023, 10:35 a.m. EST
Henrik Sönnerlind COMSOL Employee

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Posted: 2 years ago Jan 3, 2023, 7:33 a.m. EST
Updated: 2 years ago Jan 3, 2023, 10:48 a.m. EST

Since the edges are shared in the second model, you should not use a coupling condition. That may give unpredictable results, most likely some kind of overconstraint.

Probably, you have just applied wrong thickness in the second model.

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Henrik Sönnerlind
COMSOL
Since the edges are shared in the second model, you should not use a coupling condition. That may give unpredictable results, most likely some kind of overconstraint. Probably, you have just applied wrong thickness in the second model.
Panson Poon
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Posted: 2 years ago Jan 5, 2023, 1:35 a.m. EST
Updated: 2 years ago Jan 5, 2023, 8:15 a.m. EST

Thank Henrik! Yes, I did swap the thicknesses in the second model. The result is okay now.

When I zoom in for a mode shape, a gap betweem the vertical and horizontal plates can be seen. Is it just a visulaization "artifact"? The image file is attached.

Thank Henrik! Yes, I did swap the thicknesses in the second model. The result is okay now. When I zoom in for a mode shape, a gap betweem the vertical and horizontal plates can be seen. Is it just a visulaization "artifact"? The image file is attached.

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Henrik Sönnerlind COMSOL Employee

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Posted: 2 years ago Jan 10, 2023, 10:35 a.m. EST

Yes, it a visualization artifact. The shell is drawn as a solid by extruding it along the direction of the normal.

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Henrik Sönnerlind
COMSOL
Yes, it a visualization artifact. The shell is drawn as a solid by extruding it along the direction of the normal.

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