A model for strain-induced martensitic transformation of TRIP steel with pre-strain

Pre-strain is one of the key factors which can influence metal sheet mechanical properties during material multi-step deformation process. In this study, a constitutive model, which can describe the transformation-induced plasticity (TRIP) accompanying the strain-induced martensitic transformation in TRIP steel under pre-strain, is developed. The increase of nucleation site in the austenite due to the plastic deformation is formulated as the increase of the shear-band intersection. The nucleation site probability and shear-band intersection are derived not only by stress state, plasticity strain and temperature, but also by pre-strain to simulate the transformation-induced plasticity characteristic for TRIP steel. Anisotropic yield function is used to describe the sheet anisotropic property. A mixture hardening law, which is based on the pre-strain, with four phases is developed. The constitutive model is implemented into ABAQUS/UMAT to analyze the material deforming processes. Mixture hardening law of four phases with pre-strain is verified by experiment. The martensitic volume fraction is tested by X-ray to describe the comparison between experiment data and simulation. All the results are agreeable.