Dynamic response of a Q&P steel to high-strain-rate tension

The experimental study on the volume fraction of retained austenite for QP980CR steel under high-strain-rate tension is briefly described. An interrupted tensile split Hopkinson bar (TSHB) is developed to control the elongation of specimens. The QP980CR steel samples recovered from the interrupted TSHB tests are investigated using synchrotron X-ray diffraction (XRD) to analyze the effects of strain and strain rate on the martensitic transformation of retained austenite. A constitutive model of QP980CR steel coupling with the transformation-induced plasticity (TRIP) effect is presented based on Delannay's mean-field modeling. The stress-strain curves of quasi-static and dynamic tensile tests for QP980CR steel are compared with the results predicted by the presented constitutive model. The diffuse necking of QP980CR steel sheet specimens in TSHB tests is analyzed using Batra and Wei's instability criterion and the presented constitutive model. The effects of strain rate and temperature on the dynamic tensile fracture strain of QP980CR steel are also given.