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Shell-Shell connection

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Hi all,

I'm trying to model a shell with a thin film on top, modelled with another shell. In the geometry, I just have one surface, which I use in two shell-physics. In order to couple the physics I thought the following prescribed displacement in the bottom shell would be sufficient:

where H1 and H2 are the thickness of the bottom and top shell, respectively.

However, this does not seem to give the correct result. Furthermore, when I modify the offset of either of the shells, the results change. I don't see how the offset would couple into this coupling, are u1,v1,w1 not evaluated in the midsurface? How should I modify these equation to make the correct coupling, indepedent of the offset?

Best, Emiel


1 Reply Last Post 18/10/2019, 03:08 GMT-3
Henrik Sönnerlind COMSOL Employee

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Posted: 1 year ago 18/10/2019, 03:08 GMT-3
Updated: 1 year ago 18/10/2019, 06:55 GMT-3

Hi,

The degrees of freedom in the Shell interface live on the meshed surface, not on the midsurface.

The easiest solution in your case is to just rename the DOFs in the second Shell interface to be (u,v,w) (arx,ary,arz). Then, the offset will do the rest. No extra equations like the one you indicate are needed.

See for example https://www.comsol.com/model/failure-prediction-in-a-layered-shell-48371 where this technique is used.

Regards,
Henrik

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Henrik Sönnerlind
COMSOL
Hi, The degrees of freedom in the Shell interface live on the meshed surface, not on the midsurface. The easiest solution in your case is to just rename the DOFs in the second Shell interface to be (u,v,w) (arx,ary,arz). Then, the offset will do the rest. No extra equations like the one you indicate are needed. See for example where this technique is used. Regards, Henrik

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