Experimental study and a damage model approach to determine the effect of hot forming deformation on the service performance of 22MnB5 steel

Abstract

Forming damage affects the service performance of hot stamped components such as A-pillars, B-pillars and anti-collision beams. Existing constitutive models are not suitable for predicting this problem. This research aimed to experimentally and numerically study the effect of forming damage caused by hot stamping on the service performance of quenched 22MnB5 steel. The pre-forming defects were introduced into samples at 850 °C, and then the samples were quenched, cut, and stretched to fracture to ascertain the relationship between the forming strain, ultimate stress and failure strain. X-ray diffraction (XRD) tests and microstructure tests were conducted to investigate the phase composition and microdefects, respectively. A Damage-Coupled Pre-forming Constitutive Model (DCPCM) was proposed and embedded into ABAQUS by the VUMAT interface to simulate the service performance of quenched 22MnB5 steel. The results showed that the main reason for the reduced mechanical properties of the quenched 22MnB5 steel with pre-strain was increases in the number of microvoids and microcracks rather than changes in phase composition. The prediction by the proposed constitutive model agreed with the experimental results. These predictions are important for the performance design of hot stamped components.