Analytical and experimental investigation on stretch forming of an anisotropic DC04 steel sheet

Stretching of sheet metals due to the high applied tensile stress and elimination of springback leads to the production of high-strength parts with high dimensional accuracy. In this research, an analytical-experimental study of stretching of the DC04 steel sheet as one of the most widely used sheets in the automotive industry has been considered. In the experimental stage, by performing uniaxial tensile test at angles of 0 °, 45 °, and 90 ° with respect to the rolling direction of the sheet, the plastic anisotropy coefficients, the constants of the power-law hardening model, and the other mechanical factors of the material were obtained. Then the strain components in different areas of the specimens were calculated by using the Hill-48 anisotropic yield criteria based on the associated flow law. Using equilibrium equations at the contact surfaces of the sheet with the tooling components, the effect of frictional forces on the stress-strain distribution was determined. After designing and fabricating the apparatus and performing experimental tests, the values of strain, stress and thickness were measured with three displacements of punch stroke at 10.5, 15.75, and 21 mm on the specimens. Finally, comparing the results of analytical method with experimental observation, the magnitude of the errors for three mentioned punch strokes were obtained 15.8%, 4.7%, and 0.07%, respectively.