Plastic deformation characterization of automotive dual-phase steel sheets using a non-associated flow rule framework

Dual-phase steels (DP590 and DP780) are widely utilized in automotive applications due to their high strength and good formability. However, their anisotropic behavior necessitates advanced constitutive modeling beyond conventional isotropic assumptions. This study characterizes the anisotropy of DP590 and DP780 sheets through a series of experiments, including uniaxial tensile, plane-strain and shear tests. Constitutive models are developed under assumptions of associated and nonassociated flow rules (NAFRs) to capture the experimental observation. The developed constitutive models were then implemented in a VUMAT subroutine for the ABAQUS/Explicit solver, considering Hill’s quadratic yield function to simulate plane-strain and shear tests for validation. Comparison between the experimental and numerical responses demonstrates advantages of the model developed under the NAFR approach, which provides superior accuracy than that of models developed under the associated flow rule approach. The developed model based on NAFR significantly improves the predictive accuracy of dual-phase steels in forming simulations.