| 摘要 |
When forming a hat-shaped cross section member having, on its cross section perpendicular to its longitudinal direction, vertical wall portions (1b and 1b) on both sides, flange portions (1a and 1a) on both sides connected to the respective vertical wall portions (1b and 1b), and a top sheet portion (1c) connected to the vertical wall portions (1b and 1b) on both sides, and having a bent portion (2) bent in the longitudinal direction with the flange portions (1a and 1a) positioned outside by using punches (5) and dices (4), a dice shoulder radius of the dice (4) for obtaining the final shape of the hat-shaped cross section member is set to R 0 , the hat-shaped cross section member is formed by the dice (4) having a dice shoulder radius R 1 larger than the dice shoulder radius R 0 , and then the hat-shaped cross section member is formed by the dice (4) having the dice shoulder radius R 0 . By performing the forming at two stages as above, stress relaxed in a compressing direction acts in the flange portions (1a and 1a) in the final shape, and thus the balance of tensile-compressive stresses can be minimized. |
