Spring-back Suppression Forming Technology of Automotive Parts by Using In-plane Compression

Abstract

Ensuring dimensional accuracy has become difficult with the increasing application of ultra high strength steel sheet to the automotive parts. Generally, the cross section of an automotive part is U-shaped or hat-shaped, and a wavy spring-back, one of the cross section opening, occurs in the wall of curved-in-top view part in conventional bending process. Wavy spring-back is caused by difference of the degree of wall curl along longitudinal direction and its main factor is stress difference in thickness direction of the wall, caused by bending-unbending deformation at the die shoulder. To ensure the dimensional accuracy of the cross section, spring-back prospection to the negative angle is necessary, that increase forming process and costs. In order to resolve this issue, a new forming technology is developed that can suppress factor stress by applying inplane compression to the cross sectional direction. In this research, spring-back suppression effect is investigated by press trial and FEM analysis.