Verification of dynamic flow stress obtained using split Hopkinson pressure test bar with high-speed forming process

In numerical simulation, the flow stress-strain curve plays a key role in plastic deformation behavior during the forming process. Generally, quasi-static tension tests performed at a rate less than 1 s −1 are used to acquire the stress-strain curve because the process of deformation involves a low strain rate. However, the tensile properties change considerably according to the strain rate when the workpiece deforms faster than in the static state because of the effects of inertia and stress-wave propagation. In this study, the dynamic flow stress of Al 1050-H14 is acquired with the split Hopkinson pressure test bar (SHPB) test machine at strain rates of the order of 10 3 s −1 based on a modified Johnson-Cook material model. In order to verify the obtained dynamic flow stress at high strain rates, the high-speed forming process is studied through numerical simulation. In the numerical simulation, the displacements of deformation are compared with consideration of the dynamic flow stress to verify the integrity of the material test. The dynamic material test is found to be valid, and the high-strain-rate flow stress obtained using the SHPB test machine should be applied to high-speed forming processes such as electromagnetic forming and electro hydraulic forming.