Triaxiality Effect on Material Damage Evolution in Hot Rolling

Abstract

High temperature tensile tests have been conducted on double-notched bars (DNBs) of varying notch acuity ratios (a/R), achieving a range of triaxiality, to evaluate the effect of stress state on edge cracking in hot rolling of free cutting steel. The conditions of the tensile tests are selected to physically simulate hot rolling condition of as-cast material to wrought structure. All experiments were conducted using a Gleeble 3800 thermo-mechanical testing system. The aim here is to develop a qualitative relationship between the activated damage mechanisms with respect to different stress states (arising from the sample geometry). Double-notch bars have been selected for this investigation as they enable the optical examination of the pre-failure mechanisms, captured in the unbroken notched area. The damage features have been observed at the notch areas and different damage mechanisms have been identified for different stress state deforming at different temperatures.