Comparison of quasi-static and electrohydraulic free forming limits for DP600 and AA5182 sheets

Electrohydraulic forming is a pulsed metal forming process that uses the discharge of electrical energy across a pair of electrodes submerged in fluid to form sheet metal at high velocities. Pulsed metal forming processes, including electrohydraulic forming, have been shown to increase the formability of sheet metals. Although significant formability enhancement has been reported for electrohydraulic die forming, there have been conflicting reports about the formability in electrohydraulic free forming (EHFF). Numerical modeling was used to design sheet metal specimen geometries to generate data for specific regions of the EHFF forming limit curve. The electrohydraulic free forming specimens were formed with the precise amount of input energy to cause a neck at the center of the gauge section. The quasi-static and EHFF forming limit curves for both AA5182-O and DP600 sheets were determined in accordance with the conventional North American formability evaluation method to allow for direct comparison. It was found that the forming limits in EHFF increased by approximately 5% major strain for DP600 and 8% major strain for AA5182, relative to their respective as-received FLC.