Comparative analysis by simulating and testing pole impact for hot stamping front crossbeam of automobile

Hot stamping 22MnB5 steel plate with ultra high strength has been widely used for body structural members in consideration of automobile safety and lightweight. This paper presents a verification program of simulating and testing pole impact in order to verify if the front crossbeam reinforcement assembly can meet the design requirements, reduce the overall vehicle simulation and test cost and shorten the operation period. In the same condition, the simulation proved conforming to the design requirements; however, the bumper cracked at the impacting point in the course of pole impact test. The analysis of the crack by optical microscope, Vickers and scanning electron microscope indicates that mixture of ferrite, bainite and martensite was produced in the weld heat affected zone of the 340/590DP tow hook holder and the 22MnB5 front crossbeam; therefore, their hardness and mechanical property were reduced obviously, so that they fractured when impacted. No welding process with continuous weld but spot welding or other bonding method may be employed for the reason that the capacity of the 22MnB5 steel plate in the weld heat affected zone was reduced obviously.