Insight into a model for large strain anisotropic elasto-plasticity

Efficient and accurate simulation of the deformations in anisotropic metallic sheets requires a constitutive model and an accompanying algorithm at large strains which take into account the anisotropy of both the elastic and plastic material behaviors, as well as their evolution with plastic strains. Recently we proposed such a constitutive model based on continuum energy considerations, the Lee decomposition and an anisotropic stored energy function of the logarithmic strains in which the rotation of the orthotropic axes is also considered. We obtained a framework similar to the one used in isotropic elasto-plasticity. In the present work we give some physical insight into the parameters of the model and their effects on the predictions, both in proportional and in non-proportional loading problems. We also present a procedure to obtain the spin parameter of the model from Lankford R-values.