Thermo-mechanical-metallurgical and damage modeling for hot stamping and warm-cutting of boron steel

Hot stamping parts have been widely used in automobile bodies to reduce weight and ensure crash safety. The warm-cutting is an important method to replace the laser cutting of hot stamping parts to achieve low cost and high efficiency manufacturing. However, the warm-cutting is a coupling process of thermal, mechanical, metallurgical and shear fracture, and the cutting process parameters and tool design have a very important influence on the cutting quality. To achieve accurate simulation of warm-cutting process, a coupling model of thermal, mechanical, metallurgical and damage evolution is proposed. A robust numerical implementation method of the proposed model is developed. The reliability of the proposed model and numerical implementation is verified by one element tests under typical thermomechanical loading conditions. The novel thermomechanical coupled damage test is designed to identify the damage parameters related to temperature and strain rate of the proposed model. The shear damage parameters and their variation rules are obtained under high and low stress triaxiality. The reliability of the proposed model is verified by the test of typical specimens under different load conditions, the results show that the maximum prediction error is less than 5.5 %, which verifies the reliability of the proposed model. Finally, the proposed model is applied to the simulation of warm-cutting of typical parts, which can accurately predict the fracture surface quality, microstructure and hardness characteristics of the warm-cutting parts, and provide a reliable model and modeling method for fast pace and low cost hot stamping process and tool design.