Abstract: The thermo-mechanical and martensitic transformation coupled constitutive models and heat transfer between contact interfaces models of hot forming are proposed. Based on the independently developed CAE software KMAS (King-Mesh analysis system) for steel forming, a new numerical simulation module of hot forming is developed which considers high strength steels thermo-mechanical and martensitic transformation multi-field coupled nonlinear and large deformation analysis. During the KMAS simulation of hot forming, the martensitic transformation latent heat is introduced into the analysis of high strength blank and U-shaped tools temperature fields. Then, the temperature fields are introduced into the developed multi-field coupled constitutive equation and static explicit finite element equations to calculate the variation of equivalent stress and fraction of martensite. Good agreement comparison between temperature and fraction of martensite simulation and experimental results indicate the validity and efficiency of the present multi-field coupled constitutive models and the KMAS numerical simulation of hot forming.

Key words: Heat transfer, High strength steels, Hot forming, Martensitic transformation, Numerical simulation, Thermo-mechanical coupling