A study on the bi-directional springback of sheet metal stamping

The U-draw bending process is traditionally adopted to evaluate the springback of drawn sheet metals because of its large amount and uni-directional characteristic of springback. The results of springback of the U-draw bending process are, however, more or less limited to apply to general stamping processes. In this work, the bi-directional springback of drawn sheet metal parts is studied using the modified U-draw bending process. In the process, a strip with the fixed width is drawn by the elliptical tool and laid freely. Therefore, the primary springback along the longitudinal direction and the secondary springback along the transverse direction of the strip occur at the same time. In the numerical analysis, the explicit time integration method is used in the simulation of drawing stage, whereas the implicit time integration method is applied to the springback stage in order to get readily the static solution. To verify the results of numerical analysis, the experiment is also carried out. Both results are shown to be generally coincident with each other. The study is considered to be helpful to understand multi-directional springback phenomena which take place generally in industrial sheet metal stamping processes. (c) 2004 Elsevier B.V. All rights reserved.