Finite element analysis of asymmetrical leg-length in closed U-bending process

In almost all industrial fields such as automobile and aerospace industries, in recent years, the precisely complicated shapes of channel and frame parts are increasingly applied. To fabricate these parts, the U-bending process being a common sheet-metal forming process is widely employed. However, the asymmetrical U-bending process lacks researches. Therefore, in this study, the effects of asymmetrical leg-length on spring-back characteristics in the U-bending process were investigated by using the finite element method (FEM) and laboratory experiments. Specifically, on the basis of stress distribution analysis, they were clearly clarified and also compared with those in the symmetrical leg-length case. These results revealed that, with asymmetrical leg-length in a U-shaped part, the changes in leg-length on one side did not result in any different spring-back characteristics and the obtained bend angle on the other side compared with the symmetrical U-shaped parts. Furthermore, the effects of leg-length on the spring-back characteristics were confirmed that the spring-back slightly increased as the leg-length increased. Laboratory experiments were performed to validate the accuracy of the FEM simulation results. Based on the bend angles and bend forces, the FEM simulation showed good agreement with the experiments in terms of both the bend angles and bending forces.