The Evaluation of Formability of the 3rd Generation Advanced High Strength Steels QP980 based on Digital Image Correlation Method

摘要

Application of Ultra High Strength Steels(UHSS) in car BIW(body in white) is regarded as the most economic way to satisfy the lightweight goal as well as the automobile safety. In this paper, the formability of the 3rd generation Advanced High Strength Steels(AHSS) QP980 was studied and compared with that of the 1st generation AHSS DP980. The static uni-axial tensile test was conducted and the longitudinal strain of the whole deformation area were analyzed with the DIC(Digital Image Correlation) techniques. Forming limit tests of QP980 and DP980 were operated in the Marciniak way using VIC-3D . The 'RA' volume fraction of QP980 at different plastic strain was detected by XRD(X-ray Diffraction). The results show that the formability of QP980 is better than DP980.The two materials show similar formability during local deformation stage from necking to fracture. Also, proper part design and process design should be considered to avoid too much local deformation, or the better formability of QP980 could not be put into use.