Reverse loading parameter determination for ultra-thin steel sheets

Abstract

In the present study, the springback profiles of pre-strained ultra-thin steel sheets after the three-point bend test are measured and predicted with a finite element (FE) analysis. Various constitutive models are considered in the FE simulations: Two yield criteria based either on the von-Mises isotropic or the non-quadratic Yld2000-2d anisotropic yield functions are employed. Strain hardening is assumed to be either isotropic or captured by the homogeneous anisotropic hardening (HAH) model. The change of Young’s modulus is also considered for further refinement. Based on the comparison between the experimental and predicted springback profiles obtained for an ultra-thin 470FC2-1 ferritic stainless steel sheet sample, the hardening parameters of the homogeneous anisotropic hardening (HAH) model are calibrated and validated using an inverse method. Among the different constitutive model combinations investigated in this study, the isotropic hardening (IH) model associated with the elastic modulus change (E_var) leads to the best prediction results compared to the other material descriptions, in particular those including HAH. In other words, the consideration of reverse loading behavior does not seem to improve the modeling of the three-point bend test of ultra-thin sheets significantly. It is also found that planar anisotropy based on Yld2000-2d leads to slightly better springback predictions compared to those based on the isotropic von-Mises description.