Numerical and Experimental Verification of an Iterative Coupling Method for Analyzing the Lorentz-force-driven Sheet Metal Stamping Process

The Lorentz-force-driven stamping process is a newly developed forming process, which combines the advantages of the quasi-static stamping and electromagnetic forming to a certain extent. It involves complex physical problems such as strong electro-magneto-mechanical interactions and considerable deformation. Therefore, it is still a challenge to accurately predict the electromagnetic parameters (coil current and Lorentz force, etc.) and workpiece deformation (forming height and material flow) during the stamping process for different forming conditions. To solve this problem, taking the cylindrical cup forming of 5052-O aluminum alloy sheet metal as an example, a numerical method based on the iterative calculation of a circuit-electromagnetic model and an electromagnetic-mechanical model is developed and systematically validated. Numerical tests show that, compared with the non-iterative model, the proposed iterative mode can significantly improve the simulation accuracy for different forming conditions (such as varied discharge voltages and initial gaps between the coil and the punch). It has been confirmed that the iterative procedure can well consider the effect of the increased distance between the coil and the punch on the calculations of electromagnetic and mechanical parameters. Furthermore, numerical and experimental investigations for a Lorentz-force-driven stamping system using a discharge circuit with an additional crowbar branch are carried out, showing the simulation data of discharge current and workpiece deformation agree well with that of experiment measurement. This confirms the applicability of the proposed method to different discharge circuits.