Thermomechanical modeling of the shearing process during fine blanking of quenched and tempered steel

In order to develop an alloy design for fine blanking of deformation mechanism-based sheet metal materials such as high manganese steel, knowledge of the temperature during the shearing process is required. Thermomechanical modeling of shear zone temperature requires consideration of contact heat transfer, which depends on stress state as well as temperature. This paper deals with a methodology for calibrating the contact heat transfer coefficient during fine blanking using indirect temperature measurements. For this purpose, a thermomechanically coupled finite element (FE) model was designed considering thermoviscoplasticity, temperature-dependent physical and thermophysical parameters as well as a steady-state calibrated contact heat transfer coefficient. Experimental fine blanking tests were carried out to validate the model using force, die roll and thermography measurements based on varied blanking velocities. The thermomechanically coupled FE modeling showed a sufficiently accurate correspondence regarding the experimentally determined blanking force, die roll as well as sheared surface temperature. Thermographically determined sheared surface temperatures allowed calibration of locally different contact heat transfer coefficients as a simplified approach under steady-state conditions.