Study on Defect Evolution of Steel Strip under High-speed Cold Rolling

Abstract

Abstract In this paper the strain rate effect of the material was quantitatively tested by INSTRON tensile testing machine and Zwick/Roell HTM5020 high-speed tensile testing machine. The dimple size of the fracture surface of the tensile specimen was determined and analyzed by using the scanning electron microscope. Based on the Cowper-Symonds constitutive model, the parameters in the dynamic constitutive model and the true stress-strain curve under quasi-static condition were obtained by combining the results of quasi-static and dynamic tensile tests and the finite element numerical analyses. Considering the strain rate effect of the material the effects of cold rolling speed on the evolution of different types of defects were analyzed by the ANSYS/LS-DYNA dynamics code. The results show that with the increasing of crack length and decreasing of crack width, the critical rolling speed decreases. But if the crack length is less than 5 mm and the aspect ratio of crack length to crack width is larger than 5, the critical rolling speed of crack growth can be much large.