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Incompressible Yeoh Model - Solid Mechanics

Posted Mar 14, 2017, 7:32 a.m. EDT Structural Mechanics Version 5.0, Version 5.2, Version 5.2a 4 Replies

Javier Escuer
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Hello,


I'm relatively new working on Solid Mechanics with hyperelastic materials in COMSOL Multiphysics.

I'm using Yeoh model. How can I simulate incompressibility conditions in this model? I have the 3 model parameters:

c1 = 17005.903 Pa
c2 = -73429.379 Pa
c3 = 414952.313 Pa

But I'm having problems to determine the initial bulk modulus in order to simulate incompressibility.

Any help would be appreciate!

Best regards,

Javier
4 Replies Last Post Apr 11, 2017, 10:51 a.m. EDT
Nagi Elabbasi Facebook Reality Labs
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Posted: 8 years ago Mar 16, 2017, 2:35 p.m. EDT
Hi Javier,

You make the material nearly incompressible by selecting a high bulk modulus. For a Yeoh model the initial uniaxial modulus is 6*c1 which in your case is 1e5. So if you select a bulk modulus roughly 2 orders of magnitude higher then it’s nearly incompressible. However, for your case, I would make it even higher since your Yeoh parameters define a material that stiffens significantly with deformation (because of the high c3 value). So I would use a bulk modulus of at least 1e8.

Nagi Elabbasi
Veryst Engineering
Hi Javier, You make the material nearly incompressible by selecting a high bulk modulus. For a Yeoh model the initial uniaxial modulus is 6*c1 which in your case is 1e5. So if you select a bulk modulus roughly 2 orders of magnitude higher then it’s nearly incompressible. However, for your case, I would make it even higher since your Yeoh parameters define a material that stiffens significantly with deformation (because of the high c3 value). So I would use a bulk modulus of at least 1e8. Nagi Elabbasi Veryst Engineering
Nagi Elabbasi Facebook Reality Labs
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Posted: 8 years ago Mar 16, 2017, 2:36 p.m. EDT
Here are figures showing the stress-strain behavior up to 10% logarithmic/true strain and up to 50% logarithmic/true strain.
Here are figures showing the stress-strain behavior up to 10% logarithmic/true strain and up to 50% logarithmic/true strain.
Javier Escuer
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Posted: 8 years ago Apr 3, 2017, 6:03 a.m. EDT
Thank you so much for your answer. I will try your suggestion.

Best wishes
Thank you so much for your answer. I will try your suggestion. Best wishes
Javier Escuer
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Posted: 8 years ago Apr 11, 2017, 10:51 a.m. EDT
Hello again

I have a new problem... I am doing a new 2D-axisymmetric model with two different domains. The first layer has the parameters I wrote before in my first post. How can I simulate incompressibility conditions (value of the initial bulk modulus) in the second layer if the parameters of this new layer are:

c1 = 32682 Pa
c2 = -295847 Pa
c3 = 1138050 Pa

It's very easy to solve this problem in ABAQUS for example, but not here in COMSOL...

Thank you in advance.

Best regards,

Javier
Hello again I have a new problem... I am doing a new 2D-axisymmetric model with two different domains. The first layer has the parameters I wrote before in my first post. How can I simulate incompressibility conditions (value of the initial bulk modulus) in the second layer if the parameters of this new layer are: c1 = 32682 Pa c2 = -295847 Pa c3 = 1138050 Pa It's very easy to solve this problem in ABAQUS for example, but not here in COMSOL... Thank you in advance. Best regards, Javier

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