Tool shape design in the sheet bending process by inverse analysis of springback

摘要

Elastic recovery of formed parts in unloading, known as springback, causes shape error in the final product of sheet metal forming processes. The final product shape deviates from the target geometry owing to the springback. In the present paper, an analytical approach is proposed for springback analysis in the sheet bending process. By development of this approach for inverse springback analysis, an inverse algorithm for compensation of the springback error is proposed. In the inverse algorithm, the modified die geometry is obtained from the target geometry by inverse springback modelling. The proposed compensation algorithm is adapted to apply the finite element (FE) method for the inverse analysis of springback. The capability of the proposed algorithms is verified in the asymmetric bending process. The optimum die shape for producing the target geometry is obtained in a few trials. Both algorithms present high accuracy and convergence rate. The results of the analytical approach are in accordance with the FE approach with high precision. The accuracy of the presented algorithms is investigated by performing an experimental asymmetric bending test. The optimum shape obtained from the compensation algorithm is applied to produce the bending die. The obtained product matches to the target geometry with high precision. The analytical algorithm is fast and accurate for springback compensation in the bending processes. The FE algorithm is not as fast as the analytical approach, but it enables more complicated three-dimensional processes to be analysed.