Effect of internal pressure assisted on hydroforming for CP800 high-strength steel torsion beam

Abstract

With the growing application of advanced high-strength steel in automobile components, hydroformed hollow parts become popular because of the advantages of high strength and high stiffness. Hydroforming process of CP800 high-strength steel torsion beam was researched by numerical simulation and experiment in order to avoid defects and improve thickness distribution. It had been theoretically proved that circumferential bending moment in the V-shape region is an important contributing factor toward the depth of dent between up die and tube, which has a significant effect on forming performance after hydroforming. Therefore, supporting pressure was carried out in the hydropressing process to make a better preparation for hydroforming. And the effect of different pressures on forming performance was discussed. It showed that the thickness distribution could be improved effectively after hydroforming within an appropriate supporting pressure range during preforming. In hydroforming process, the effect of supporting pressure during axial feeding was developed by an experiment based on the simulation numerical simulation. It showed that an appropriate internal pressure could avoid wrinkle and improve thickness distribution nearby the end area of tube effectively. Finally, a qualified hydroformed torsion beam was manufactured.