New convex yield functions for orthotropic metal plasticity

Two new yield functions for orthotropic sheet metals are proposed. The first one, called Yld2011-18p, provides 18 parameters that may be calibrated to experimental data. The second one, called Yld2011-27p, is a straightforward extension and provides 27 parameters. Both yield functions are unconditionally convex. Their formulations are based on the established concept of multiple linear transformations of the stress deviator. Furthermore, they are able to account for planar as well as for three-dimensional stress states. The proposed yield functions are applied to describe complex plastic anisotropies of different alloys. The ability of accurately predicting earing in cup-drawing is demonstrated by means of a non-linear finite element analysis.

► New non-quadratic yield functions for orthotropic metal plasticity were developed.
► Several application cases are considered that demonstrate the ability of the proposed yield functions to describe complex plastic anisotropy.
► A non-linear finite element analysis of cup-drawing using one of the proposed yield functions demonstrates that earing can be predicted with very good accuracy.