Numerical simulation of an U-channel component tailored tempering process considering the effect of stress on the shift of TTT curves

A numerical model of the tailored hot stamping process was developed in the framework of the commercial FE code Forge™ and accurately calibrated in order to take into account the influence of applied stress and strain on the phase transformation kinetics. The calibration was carried out by introducing in the numerical model data on the shift of the TTT curves due to applied stress and the transformation plasticity coefficients, which were obtained through an extensive dilatometric analysis. The numerical model was validated through a laboratory-scale hot-formed U-channel produced using a segmented die with local heating and cooling zones. The predicted distribution of Vickers hardness and evolution of microstructure given by the numerical model was compared with the experimental results to show the significant predictive improvements introduced by considering the influence of the transformation plasticity and deformation history on the phase transformation kinetics.