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Finite Strain Formulation For Solid Mechanics Module
Posted 28 lug 2022, 05:08 GMT-4 Structural Mechanics, Physics Interfaces, Material Models 0 Replies
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Hello everyone,
I have a query regarding External Strain sub-node for a hyperelastic material and I hoped someone could help me. I understand that when we add an External Strain for a hyperelastic material in solid mechanics module, COMSOL first calculates the elastic Second Piola- Kirchhoff Stress and then, using a pull-back operation determines the same stress in undeformed (material) configuration. I was wondering how the elastic Second Piola- Kirchhoff Stress is being calculated for a hyperelastic material?
As you can see in the attached screenshot which is the equation view section for a hyperelastic material, COMSOL is calculating the elastic Second Piola- Kirchhoff Stress first, by taking the derivative of the strain energy function (Ws) with respect to the elastic right Cauchy-Green tensor (Ce), until this part everything seems to be correct but after taking the derivative, the result is being divided by the Jacobian of the inelastic deformation tensor (Ji), I am curious what is the reason that the derivative is being divided by the Ji? because according to Hooke’s law, Ji is just being used for the pull-back operation and not in the definition of the elastic Second Piola- Kirchhoff Stress.
Thank you in advance for any feedback.
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Hello Lucas Jones
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