Tool shape design in V-bending and channel forming processes by inverse analysis of springback

摘要

Elastic recovery of a formed part in unloading, known as springback, causes shape errors in the final product of sheet metal forming processes. Several approaches have been proposed for the analysis of springback and compensating its error. The springback occurs at the last step of process and the final geometry of the work piece can be obtained at the end of direct process modelling. In this article, an algorithm for inverse springback modelling is presented. In this approach, required conditions for the inverse movement of final product towards the end of the loading state are prepared. Having the product geometry at the end of the loading, the geometry of die parts can be designed for the production of a target shape. For this inverse movement in FE modelling, the optimum constrained node and balanced contact forces are proposed in this algorithm. The presented approach is verified for symmetric and asymmetric bending processes. The results have shown that this approach can model symmetric and asymmetric processes inversely with tight tolerances. An optimization algorithm for compensating springback error and iterative tool design is presented based on inverse modelling. This algorithm is verified on symmetric V-bending process and its convergence rate is compared to the direct trial trend. The inverse approach shows more convergence rate in this comparison. Performing an experimental test on symmetric V-bending and asymmetric bending processes, the accuracy of the presented algorithms is investigated. The results show that the presented algorithms are efficient and accurate in both cases.