A multi-objective Pareto design approach for simultaneous control of thinning and springback in complex stamping operations.

Abstract In sheet metal forming operations design, optimization problems have to be solved in order to reach optimal process conditions. In these problems, there are some crucial issues to be taken into account: - most of the problems are multi objective problems, generally characterized by conflicting objectives: the definition of proper parameters aimed to prevent both springback and fracture is a typical example of an optimization problem in sheet metal forming characterized by conflicting goals; - in an industrial environment a great interest would be focused on the availability of a cluster of possible optimal solutions instead of a single “almost optimal” solution. Taking into account all these issues, a multi-objectives optimization procedure based on Pareto optimal solution search techniques seems a very attractive approach to deal with sheet metal forming processes design. In this paper, integration between numerical simulations, response surface methodology and Pareto optimal solution search techniques was applied in order to design a 3D complex stamping process. Two process parameters (blank holder force and drawbeads penetration) were utilized as design variables to be optimized in order to accomplish two different objectives: control thickness distribution along the workpiece and avoid excessive geometrical distortions due to springback occurrence. The final aim of the research is to develop a predictive tool able to identify a sort of process window for the analysed operation also minimizing the computational effort with respect to mono-objective optimization techniques or traditional trial and error methods.