Anisotropic strain-rate potential based on multiple linear transformations

The plastic anisotropy of sheet metals can be described using phenomenological yield criteria or strain- rate potentials. Linear transformations provide one of the most effective ways to describe anisotropy in this framework. In this work, an anisotropic strain-rate plastic potential with an arbitrary number of transformations is formulated as an extension of former potentials involving one or two transformations, respectively. The parameter identification becomes an important issue since the number of parameters increases along with the number of transformations. A specific parameter identification method is used, based on a micromechanical model. Several sheet aluminium alloys and sheet steels are used to investigate the gain in accuracy when the number of linear transformations in the model increases. It is shown that when five or more transformations are used, the new model is able to describe the initial plastic anisotropy as accurately as a micromechanical model - provided that its parameters are identified accordingly.