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Solid Mechanics equation doesn't line up with documentation

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Hello,

I'm trying to better understand the workings of the solid mechanics module, and I came across an apparent discrepancy between the documentation and the module itself.

The momentum balance equation in the module itself (Solid Mechanics -> Equation) for a stationary solution is:

,

but according to the documentation, the correct equation is:

.

I feel like I must be missing something simple here. Does the solver assume that the strain is small, and therefore ? Or is there maybe one of the gradients in terms of the materials frame and one is not?

Cheers, Adam


2 Replies Last Post Nov 13, 2018, 9:17 AM EST
Henrik Sönnerlind COMSOL Employee

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Posted: 1 year ago Nov 13, 2018, 6:59 AM EST

Hi Adam,

What you see in the GUI is, as you suspect, the geometrically linear form. If you select the Include geometric nonlinearity check box in the study, the displayed equation will change accordingly.

Regards,
Henrik

Hi Adam, What you see in the GUI is, as you suspect, the geometrically linear form. If you select the *Include geometric nonlinearity* check box in the study, the displayed equation will change accordingly. Regards, Henrik

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Posted: 1 year ago Nov 13, 2018, 9:17 AM EST

Henrik,

Thanks so much, that was indeed the problem!

Adam

Henrik, Thanks so much, that was indeed the problem! Adam

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