Effects of temperature, forming speed and stress relaxation on springback in warm forming of high strength steel sheet

摘要

Springback of sheet metals in warm forming is strongly influenced by temperature, forming speed and the stress relaxation. In the present work, springback of a high strength steel sheet of 980 MPa grade in V- and U-bending was experimentally investigated at temperatures ranging from room temperature to 973 K. In both V- and U-bending, amount of springback decreased with temperature rise especially at temperatures above 573K. Springback was much reduced by lower forming speed. These phenomena directly correspond to the material's viscoplastic behavior at elevated temperature. The effect of stress relaxation on the springback was discussed by performing a V-bending springback experiment and the visco-plasticity stress analysis.