Determination of the flow curve at high strain rates using electromagnetic punch stretching

A simple new method is proposed and applied to determine the flow curve of aluminum alloy 1100-O at high strain rates. A high-speed camera was used to record the free flying process, from which the retrieved images were used to characterize the impacting velocity. The determined flow curve was established by combining the effective stress retrieved from the simulation and the effective strain measured from the deformed workpiece. Moreover, an iteration procedure was utilized to improve the accuracy of the determined flow curve. Using the determined flow curve to simulate the forming process, the simulated deformation performed good agreement with the experimental result, where the deviation of effective strain could be reduced from 17.9% to 6.74%. Besides, the effective strains reached in these high rate forming experiments exceed the effective strain at failure determined in a quasi-static tensile test. The material could be deformed to the effective strain of 0.56 without any fracture.