Optimum Draw-beads Setting for Suppressing Wrinkle and Torsional Springback of Stepped-beam Model

Abstract

In this paper, we propose a new method of suppressing the wrinkle and torsional springback in sheet metal forming by FE simulation. The key technique is the determination of the optimum shape and height of drawbeads by an optimization technique. To demonstrate this technique for the forming of a Stepped-shape beam using a high-strength steel sheet, we show a new approach to evaluating the degree of wrinkle based on the curvature distribution in wrinkle areas. The optimization problem, where the objective function to be minimized is the degree of wrinkle and the design variables are geometric parameters of drawbead shape, is solved under several constraints on torsional springback, fracture, sheet thickness and so on. Using the thus-determined drawbeads, we have succeeded in reducing wrinkle and torsional springback markedly, which was confirmed in a Stepped-beam forming experiment.