Investigation of constitutive equation parameters on dual phase steel sheets

Abstract

This study is about using of the least squares' method for parameter defining and model accuracy investigation of mechanical-based work-hardening laws of automotive dual phase steels. The experimental true stress true strain curves were determined by standard, quasi-static tensile tests at room temperature. As most of the commercial finite element codes are using mechanical-based constitutive equations for describing the stress-strain relationship of the materials, the coefficients of these equations are one of the most important input parameters of the simulations. The results show that most of the models are able for data estimation, but the physical meaning of each model parameters is not taking into account by this mathematical technique. The highest of the stress values are observed at Ludwik's solution, while the lowest are given by the Voce model at each steel grades. Although the differences are negligible in the strain range of uniform elongation, but significant discrepancies are displayed at higher strains, which typically occur during sheet forming processes in the press shop. The model parameters' developing in the function of the martensite volume fraction was also considered.