Discussion Forum

Dear Sirs,

I am currently using Comsol 4.2a. I am performing numerical tests of structural problems both using the Structural Mechanics module and the General PDE module. I am modelling the material as Neo-Hookean in the nearly-incompressible form.

My problem is that, using the two modules, performing the same test on the same geometry and using the same BCS, the results are clearly different. It's evident I am making some errors.

Since in the General PDE - Weak form (that is what I am using) I have to specify the weak formulation of the problem, I define the first Piola-Kirchhoff tensor and then use. I am wondering where, when the Structural Mechanics module is used, I can see the definition of the first Piola Kirchhoff tensor.

Please note: As you know, in the Structural Mechanics module, when I insert the strain energy function and I activate the Equation view, I can already find a definition of the First Piola-Kirchhoff tensor. That one is useless to check how the tensor P is defined. In fact, it is formulated as the product of F*S where F is the deformation gradient and S is the second Piola Kirchhoff tensor. Recursively, the definition of the tensor S is given in terms of general derivatives of the strain energy functions ( \partial W / \partial C) where W is the strain energy and C is the right Cauchy-Green tensor.

Is there a way to check the tensorial expression of P and not its symbolic one?

Thanks a lot,

I wish you a nice day.

Paolo Tricerri