A nonlinear kinematic hardening model for the simulation of cyclic loading paths in anisotropic aluminum alloy sheets

Sheet metal forming processes generally involve complex loadings and material nonlinearities. Combinations of drawing, re-drawing and/or reverse drawing operations commonly induce cyclic loads with different strain paths, leading to Bauschinger effects that can not be predicted by conventional isotropic hardening laws. In order to properly represent such an effect, it is required to accommodate an appropriate kinematic hardening model along with a planar anisotropic yield function. Yld2000 (Barlat et al. [1]), for instance, can accurately capture both yield stress and r-value directionalities. In this work, the Barlat yield function Yld2000 is implemented with a nonlinear kinematic hardening model, based on the definition of two yield surfaces by Dafalias and Popov. The incremental deformation theory is used to properly handle the stress integration for non-quadratic yield functions in elasto-plasticity.