Abstract
This paper deals with the complexly-shaped hat channel product, which combines a straight part with a curved part in the longitudinal direction. Twist in the longitudinal direction is the most typical and serious of all dimensional inacuracies in the product. Influencing factors in twisting can be classified into residual stress and residual moment. At first by varying forming conditions, such as blank holding force and cushion force, the influence of the residual stress generated on shrink and stretch flange on twist are investigated. Contrary to our expectation, the residual stress had almost no twist. Subsequently, by cutting flanges and side wall to release the residual moment, the influence of the residual moment on twist was investigated. It was observed that the residual moment plays an important role on twist. Based on the above, some parts of die radius are varied to control residual moment. As a result, it is experimentally found that twist decreased.
