Comparison of spring-back characteristics in symmetrical and asymmetrical U-bending processes

Abstract

In recent years, increased manufacturing precision of complicated U-shaped parts is required. Such parts are typically fabricated by the U-bending process. However, there is a lack of research on the asymmetrical U-bending process. This results in processing difficulty in the control of spring-back characteristics. Therefore, in this study, the spring-back characteristics in the asymmetrical Ubending process were clearly clarified and compared with those in the symmetrical U-bending process using the finite element method (FEM). Furthermore, the effects of bend angle and tool radius on the spring-back characteristics were also investigated. The results revealed that the asymmetry of the U-shaped parts resulted in changes in bending and reversed bending stress distribution as well as in the spring-back characteristics. Therefore, with asymmetrical bend angles or tool radii in a U-shaped part, the changes in bend angle and/or tool radius on one side resulted in different spring-back characteristics and the obtained bend angle on the other side compared with the symmetrical U-shaped parts. Laboratory experiments were performed to validate the accuracy of the FEM simulation results. Based on the bend angles and bending forces, the FEM simulations showed good agreement with the experiments in terms of both the bend angles and bending forces.