Improved Formulation for Small Strain Plasticity with Geometric Nonlinearity
You can now use a small plastic strain formulation for significantly larger strains without significant loss of accuracy. When you select Small plastic strains as the plasticity model in the Plasticity node, and the study incorporates geometric nonlinearity, the Cauchy stress tensor is used to evaluate the yield function and plastic potential. In earlier versions of the software, the second Piola-Kirchhoff stress tensor was used instead, which limited the useful strain range to a few percent. The Large plastic strains option, available since an earlier release of COMSOL Multiphysics, is more accurate but computationally more expensive. With the new formulation for small plastic strains, the limit for when the full large strain formulation is needed increases from a strain of a few percent to 20% or more, depending on the required accuracy.
Stresses during elastoplastic compression of a pipe, with both a small (left) and large (right) plastic strain assumption.