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how to model an Hyperelastic material

Posted 26 set 2011, 10:59 GMT-4 Structural Mechanics Version 4.1 3 Replies

Giacomo Cerretti
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Hi,
I have to model the strain and stress trend for an hyperelastic material and I'd like like to have some advices because I don't know which equations I can use. The second Piola-Kirchhoff equation can be used for hyperelastic materials?
I found this one:

S= J*F^-1*σ*F^-T

but I don't if I can use it in this kind of material. If it's possible to use it how can I calculate σ (stress)? And the strain (ε)? And in which way they are related? Because I suppose I can't use the Hooke law (σ=E*ε).

Thanks.
3 Replies Last Post 30 set 2011, 07:13 GMT-4
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 26 set 2011, 17:41 GMT-4
If you have a hyperelastic material you can just use the COMSOL capability that allows you to define your own hyperelastic strain-energy function. That way COMSOL will internally handle the stress transformations, and provide you output of Cauchy (true) stress, first and second Piola Kirchhoff stress.

Nagi Elabbasi
Veryst Engineering
If you have a hyperelastic material you can just use the COMSOL capability that allows you to define your own hyperelastic strain-energy function. That way COMSOL will internally handle the stress transformations, and provide you output of Cauchy (true) stress, first and second Piola Kirchhoff stress. Nagi Elabbasi Veryst Engineering
Alper Ozturk
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Posted: 1 decade ago 27 set 2011, 10:00 GMT-4
Comsol have a number of hyperelastic material models that you can use, and alternatively, you can define your own material model. Generally, a neo-Hookean material model, or Mooney-Rivlin model defines rubber-like material quite well. However, it sounds like you don't know the behavior of the hyperelastic material you are interested in. You might want to start with some experimental data of the stress strain (or force-elongation) curve of the material which might help you.
Comsol have a number of hyperelastic material models that you can use, and alternatively, you can define your own material model. Generally, a neo-Hookean material model, or Mooney-Rivlin model defines rubber-like material quite well. However, it sounds like you don't know the behavior of the hyperelastic material you are interested in. You might want to start with some experimental data of the stress strain (or force-elongation) curve of the material which might help you.
Giacomo Cerretti
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Posted: 1 decade ago 30 set 2011, 07:13 GMT-4
Hi,
thanks so much. I think I found something interesting. I just have to insert my equations and see what happens. If i'll need more explainations I'll write down all my questions.

Thanks, bye
Hi, thanks so much. I think I found something interesting. I just have to insert my equations and see what happens. If i'll need more explainations I'll write down all my questions. Thanks, bye

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