Suppressing method of the cross section deformation for extruded square tubes in press bending

Abstract

Aluminum alloys are widely used in the automotive industry to realize weight reductions. Extruded square tubes made from aluminum alloys show superior workability, and therefore, they are used as lightweight structural elements in various fields. To use such tubes in automobile parts, fabrication processes such as bending are necessary. However, bending can easily cause undesirable distortions such as thickness deviation and flattening. Generally, the use of a mandrel is considered to suppress these distortions effectively. However, studies have not yet established a bending technology for achieving highly accurate cross sections. This study aims to develop a press bending technology for obtaining tubes with highly accurate cross sections. First, we designed and developed a restraint jig for use in this bending process. A laminated mandrel was applied to the inside of the square tube and a constraint load was applied to the restraint plate on the outside to suppress cross-sectional deformation. The effect of the use of a mandrel and restraint plate on the bending of a square tube was experimentally investigated. Furthermore, the press bending process was analyzed through simulations using the finite element method (FEM).