Experimental and numerical investigation of flange angle in Chain-die formed AHSS U-channel sections

With an increasing demand to reduce the body weight of motor vehicles, advanced high strength steel (AHSS) is widely applied in the automobile industry. However, high residual stresses and redundant deformation caused by the cold roll forming process are still outstanding problems. Under such circumstances, Chain-die forming technology is developed. Through enlargement of the effective roll radius, the deformation length is significantly stretched, leading to a significant reduction in residual stresses and redundant strain. In this study, Chain-die formed AHSS U-channel products are investigated experimentally and numerically. The influences of a number of features such as material strength, sheet metal thickness, vertical forming gap, and effective virtual roll radius are discussed regarding average flange angle and the variation of flange angle along the longitudinal direction. The results show that the average flange angle decreases with the increase of material strength, vertical forming gap, and effective virtual roll radius. Furthermore, among all four controllable variables, effective virtual roll radius has the most significant impact on the variation of the flange angle along the longitudinal direction.