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Easy way to convert a complex solid model to shell model

Posted 31 janv. 2013, 15:18 UTC−5 Geometry, Structural Mechanics Version 4.3a 3 Replies

Roy Martin
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I am working with a complex structure with formed sheet metal and tubes. Wall thickness of ~.030" with linear dimensions on the scale of 8 to 15". Definitely a problem that would benifit from a shell model.

However, there seems to be no easy way to collapse the solid forms down to shells/boundaries.

And with over a 1000 boundaries, manually selecting the outer or inner surface of the solids seems to be a very tedious task that will be prone to errors.

Is this the only way in comsol to set up a shell model?

I rememeber 10 years back using Pro/Mechanica being able to pick a thin walled part and collapse it's boundaries down to either a midplane, inner or outer boundary.

Comsol does not have anything like this?

3 Replies Last Post 12 févr. 2020, 13:37 UTC−5
Josh Thomas Certified Consultant
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Posted: 1 decade ago 31 janv. 2013, 16:27 UTC−5
Roy-

If you right-click on Geometry and select Conversions>Convert to Surface you can convert solid bodies to surface bodies for use with the Shell Physics Interface.

You can also select the Create Selections box to have all the surfaces saved into a selection that can be accessed by any drop-down boxes for your Boundary Selection in your Physics set-up.

A relatively new feature in COMSOL is the ability to automatically select all boundaries that have a continuous tangent to a selected boundary. This may be helpful to you. You can go under Definitions and add an Explicit selection. Change the geometric entity level to Boundary. Then, check the "Group by continous tangent" check box. Then, which ever boundary you add will automatically have all continuous tangent boundaries added. This may enable you to easily limit your new surface body to only 1/2 of the boundaries without a lot of manually selecting.

Best regards,
Josh Thomas
AltaSim Technologies
Roy- If you right-click on Geometry and select Conversions>Convert to Surface you can convert solid bodies to surface bodies for use with the Shell Physics Interface. You can also select the Create Selections box to have all the surfaces saved into a selection that can be accessed by any drop-down boxes for your Boundary Selection in your Physics set-up. A relatively new feature in COMSOL is the ability to automatically select all boundaries that have a continuous tangent to a selected boundary. This may be helpful to you. You can go under Definitions and add an Explicit selection. Change the geometric entity level to Boundary. Then, check the "Group by continous tangent" check box. Then, which ever boundary you add will automatically have all continuous tangent boundaries added. This may enable you to easily limit your new surface body to only 1/2 of the boundaries without a lot of manually selecting. Best regards, Josh Thomas AltaSim Technologies
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 1 févr. 2013, 01:00 UTC−5
Hi

remains that certain other programmes have geometrical features that collapses thin walled volumes to the mid surfaces, but you also need to get the boundaries to link again, increasing slightly the length of others. And for 1000 surfaces you need to check and verify all this anyhow

By the way with shell elements you can set an offset I believe. I have mostly given up the shell elements for this reason, but I agree, for complex models they give often better results, but you have quite some manual knitting to do

--
Good luck
Ivar
Hi remains that certain other programmes have geometrical features that collapses thin walled volumes to the mid surfaces, but you also need to get the boundaries to link again, increasing slightly the length of others. And for 1000 surfaces you need to check and verify all this anyhow By the way with shell elements you can set an offset I believe. I have mostly given up the shell elements for this reason, but I agree, for complex models they give often better results, but you have quite some manual knitting to do -- Good luck Ivar
Jeff Hiller COMSOL Employee

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Posted: 4 years ago 12 févr. 2020, 13:37 UTC−5
Updated: 4 years ago 12 févr. 2020, 13:39 UTC−5

The Design Module, launched a couple of years after this thread started, includes the midsurfacing capability, which does exactly what Roy was looking for, namely replace a thin object with an equivalent surface.

Best,

Jeff

-------------------
Jeff Hiller
The [Design Module](https://www.comsol.com/design-module), launched a couple of years after this thread started, includes the midsurfacing capability, which does exactly what Roy was looking for, namely replace a thin object with an equivalent surface. Best, Jeff

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