On the modeling of evolving anisotropy and large strains in pearlitic steel

A phenomenological model for deformation induced evolution of anisotropy at large strains in pearlitic steel is proposed. The modeled anisotropy is based on a homogenization of an ideal pearlitic microstructure. An areal affine type of reorientation is assumed for the individual grains. Furthermore, a yield criterion of the Hill type is proposed and motivated from the grain reorientation. In each pearlitic grain the cementite lamellas have a privileged direction. The symmetry group of each individual grain is therefore considered transversally isotropic. In a virgin material, the privileged directions of the different grains are randomly oriented, which allows for the interpretation that the material on the macroscopic length scale is initially isotropic. However, the cementite lamellas in the grains tend to align after large stretching or shearing deformation. The modeled evolution of anisotropy on the macroscopic length scale shows a saturation characteristics under large deformations.