Experimental and Numerical Study of Effective Parameters in Forming of Double-Stepped Parts and Optimization of the Initial Blank Shape

Production of double-stepped metal sheet parts is considered a complex and difficult task in industries. The crankcase is such a complex double-stepped part for the automobile industry and its production with traditional methods is associated with many problems. In this paper, the formability of this stepped part has been studied experimentally and by simulation using hydrodynamic deep-drawing with radial pressure. It is shown that the crankcase can be formed successfully in one step by the hydroforming process. Moreover, the effect of fluid pressure on the thickness distribution and die filling and the effect of geometric parameters such as punch corner radius and the height of the steps on the thinning, and also optimal shape design of the original blank were investigated. The study showed that choosing the correct forming pressure can improve formability and increase the amount of die filling. It is also illustrated that by increasing the punch corner radius, the maximum thinning is reduced and the thickness distribution is improved and, by increasing the height of the steps, thinning in the wall of the first step and the punch corner radius increase; by decreasing the height of the steps, thinning position will be shifted toward the second step. Also, by optimizing the original blank, it has been concluded that the optimization of the shape of original blank has a major impact on the material flow and will delay the sheet rupture.