A new progressive design methodology for complex sheet metal stamping operations: Coupling spatially differentiated restraining forces approach and multi-objective optimization

The growing interest in sheet metal stamping processes, particularly in the automotive industry has led to three main issues in this field:
• request of very complex shapes;
• growing interest in springback control;
• solution of multi-objective problems.These issues make a sheet metal stamping processes design very difficult and proper design methodologies to reduce times and costs are highly required.In this paper, a computer aided approach aiming to satisfy the mentioned issues is proposed. In particular, a progressive design approach based on the integration between numerical simulations, Response Surface Methodology (RSM) and Pareto optimal solutions search techniques was applied in order to design a complex 3D automotive stamping operation. An explicit/forming-implicit/springback approach was utilized to develop the numerical simulations.The proposed design approach is able to verify the necessity of a spatially differentiated restraining forces approach and to design the best policy for them.Pareto optimal solutions search techniques were applied in two different phases: the former Pareto frontier was built using an uniform restraining forces policy while the latter, which is the final process design tool, was based on a differentiated restraining forces strategy.Two different restraining force policies were applied: the former focused on drawbeads utilization, the latter utilized a segmented blankholder.As the optimization objective functions are concerned, indicators related both to thinning distribution and to springback amount were taken into account.The obtained Pareto curves can be used in order to discriminate which conditions have to be expected once a desired value of one of the objective functions is fixed.A new and flexible design methodology is proposed, able to:
• deal with complex sheet metal stamping processes;
• investigate many possible technological scenarios;
• carry out a set of reliable solutions able to satisfy different design requirements.