An application of homogeneous anisotropic hardening to springback prediction in pre-strained U-draw/bending

In this work, a constitutive model based on anisotropic hardening was used in the finite element (FE) simulations of springback and its performance was compared with that of conventional hardening laws. The homogeneous yield function-based anisotropic hardening (HAH) model (Barlat et al., 2011), considered in this work, describes a partial distortion of the yield surface under plastic loading. Although it does not use the concept of kinematic hardening, the HAH model was able to predict the complex material behavior upon load reversals such as the Bauschinger effect, transient hardening and permanent softening. For the application to springback, FE simulations were conducted for U-draw/bending of base (as-received) and pre-strained DP780 steel sheets, which was recently proposed as one of the Numisheet 2011 benchmark problems. The predictions with the HAH model, combined with a non-quadratic anisotropic yield function and a plastic strain-dependent unloading modulus, were in good agreement with experimental results for both as-received and pre-strained DP780 sheets.