Investigation of the Lorentz-force-driven sheet metal stamping process for cylindrical cup forming

Abstract

A new dynamic forming method denoted as Lorentz-force-driven (LFD) sheet metal stamping was proposed in this work, which has been applied to cylindrical cup forming. A series of experiments were carried out to investigate the deformation behavior of workpiece based on the forming method under different conditions, and a three-dimensional coupled electromagnetic-mechanical numerical model was established to better understand the dynamic forming process. Results show that the features of discharge current waveform including current frequency and damping state have obvious effects on the forming behavior of workpiece, and an additional crowbar circuit with no resistance could be used to achieve a relatively high forming efficiency in a wide frequency range. Further, a flat-bottom cylindrical cup made of 5052-O aluminum alloy with a thickness of 0.96 mm and a drawing ratio of 2 can be achieved by only two discharges, where the total discharge energy is 32 kJ and the final cup height is about 66.4 mm. More importantly, it has been demonstrated that the thickness reduction of workpiece in the forming process could be improved by additional radial pulsed Lorentz forces, showing that the new dynamic forming method is expected to have good prospect in deep drawing of workpieces with large drawing ratios.