2020 年 61 巻 713 号 p. 131-137
The purpose of this research is to develop technology to make complex-shape closed-section parts from sheet blanks. Closed-section parts with large expansion of circumferential length are expected to be manufactured by such forming technology. In this work, the effect of the deformation path is investigated in the forming of horn tubes, curved circular tubes, and curved conical tubes. These tubes are formed by three processes (U-shaping, curving, and closing). The main conclusion based on the results of finite element (FE) analysis is as follows. The parameter α = κ B1/ κ B2 is proposed as a universal parameter that indicates the difference between deformation paths. κ B1 is the longitudinal curvature at the bottom of a U-shaped section of the sheet after the U-shaping process. κ B2 is that after the closing process. It is clarified that the strain induced during forming can be organized relatively by using parameter α. With an increase in parameter α, stretch strain at the sheet edge of section of each tube increases. On the other hand, compression strain at the bottom of the section decreases.