Optimum blank design of an automobile sub-frame

A roll-back method is proposed to predict the optimum initial blank shape in the sheet metal forming process. The method takes the difference between the final deformed shape and the target contour shape into account. Based on the method, a computer program composed of a blank design module, an FE-analysis program and a mesh generation module is developed. The roll-back method is applied to the drawing of a square cup with the flange of uniform size around its periphery, to confirm its validity. Good agreement is recognized between the numerical results and the published results for initial blank shape and thickness strain distribution. The optimum blank shapes for two parts of an automobile sub-frame are designed. Both the thickness distribution and the level of punch load are improved with the designed blank. Also, the method is applied to design the weld line in a tailor-welded blank. It is concluded that the roll-back method is an effective and convenient method for an optimum blank shape design.