Discussion Forum

I'm simulating mechanical resonators made of anisotropic materials and am struggling to understand COMSOL's expected input for the material's elasticity tensor.

Under the Linear Elastic Material node, there's a dropdown to choose "Material data ordering" and can be toggled to select either "Standard" or "Voigt". Under the Materials node, you can either specify a material's "Elasticity matrix", or its "Elasticity matrix, Voigt notation."

I ran the same study on the same component 4 times with all possible permutations of the toggles above, and I'm not understanding how to interpret the results.

Study 1: "Standard" ordering and "Elasticity matrix." Study 2: "Standard" ordering and "Elasticity matrix, Voigt notation." Study 3: "Voigt" ordering and "Elasticity matrix." Study 4: "Voigt" ordering and "Elasticity matrix, Voigt notation."

Studies 1 and 3 gave identical results, while studies 2 and 4 also gave identical results. This makes it seem like the "Material data ordering" toggle has no effect on simulations, so what does it do? I understand that changing between "Elasticity matrix" and "Elasticity matrix, Voigt notation" while inputting the same tensor values changes the order of the shear terms, so seeing different results between those studies was expected.

In each case, I set the elasticity matrix to be assigned from the material rather than choosing "User defined." Is the toggle really only necessary when inputting "User defined" material properties?

I compared these 4 studies with a study where the "Material symmetry" was set to "Crystal" and inputted the c_ij values for the elasticity tensor (in Voigt notation); and this study gave identical results to studies 2 and 4.

What is the "proper" way to set the "Material data ordering" and input elasticity tensors in these simulations?

Thanks!