Forming Technology for 3D Closed Section Parts from Sheet Metal

Most conventional closed section parts are made of tubular blanks including welded tubes; however, it is difficult to fabricate complex shapes with large variations of circumferential length because of restrictions in the circumferential direction. Another approach is to fabricate closed section parts directly from sheet blanks. Direct forming from sheets has less restriction in the circumferential direction than tube forming. Therefore, direct forming is expected to enable fabrication of more complex shaped closed section parts with larger variation of circumferential length. However, only a few fundamental researches were conducted. In this paper, fundamental studies on direct sheet forming were carried out for better understanding of deformation and to provide information regarding the design and forming condition. The horn tube, which consists of circular and truncated conical tubes, is a rather simple shape but it is a typical shape of a closed section. It is selected for this study. Through this study, even in two-stroke forming from sheets to final shape, it is revealed that it can be broken down into several deformation modes.