Modeling of a tempered martensitic hot work tool steel behavior in the presence of thermo-viscoplastic coupling

In the present analysis a constitutive model is proposed to describe the fatigue behavior of martensitic hot work tool steel in non-isothermal conditions. 2M1C (2 mechanisms-1 yield criterion) model derived by Cailletaud and Saï (1995) and identified by Velay et al. (2006) to describe the fatigue behavior of AISI L6 steel at different (but constant) temperatures, is extended to account for the effect of temperature change. Two cases are compared: (1) partial coupling, when changing temperature is accounted only in changing material parameters, and (2) full coupling, when additional terms proportional to temperature rate are added in the kinetic equations of thermodynamic conjugate forces. Numerical simulations are performed, which indicate the significant influence of temperature rate on the response of constitutive model when cyclic thermo-mechanical loading is considered.