Experimental and Fracture Model Study of Q690D Steel Under Various Stress Conditions

The fracture failure of high-strength steel has an important relationship with the stress state. In order to predict the fracture failure of high-strength steel under different stress conditions, based on the void growth model (VGM), a fracture model which comprehensively considers the effect of stress triaxiality and the Lode parameter on fracture failure is proposed and is called LVGM. A batch of Chinese Q690D high strength steel round rods and plate shaped specimens reflecting different stress states were processed, and the monotonic tensile tests, the scanning electron microscopy tests and the finite element calculation were carried out to study the crack initiation of the specimens. The microscopic mechanism of the fracture damage of the specimens was analyzed. Based on the fracture test results of the specimens and the corresponding finite element analysis, the LVGM parameters of the Q690D high strength steel were calibrated. Finally, the LVGM was used to predict the crack initiation and fracture failure process of the specimens with initial gap. The prediction results are in good agreement with the experimental results, and the LVGM has better prediction accuracy than the VGM.