Work-hardening predicition using a dislocation based model for automotive Interstitial Free (IF) steels

Abstract

With a view to environmental, economic and safety concerns, car manufacturers need to design lighter and safer vehicles in ever shorter development times. In recent years, High Strength Steels (HSS) like Interstitial Free (IF) steels which have higher ratios of yield strength to elastic modulus, are increasingly used for sheet metal parts in automotive industry to reduce mass. The application of simulation models in sheet metal forming in the automotive industry has proven to be beneficial to reduce tool costs in the design stage and optimizing current processes. The Finite Element Method (FEM) is quite successful to simulate metal forming processes but accuracy depends both on the constitutive laws used and their material parameters identification. The purpose of this study is to present, a work-hardening physically-based model at large strain with dislocation density evolution approach. This approach can be decomposed as a combination of isotropic and kinematic contributions. The predictive capabilities of the model are investigated for different Interstitial Free (IF) steels of grain sizes varying in the 5.5-22µm value range. Different loadings paths are analyzed and stress-strain curves have been experimentally assessed and they are compared to the model predictions.