Effects of prestrain on the fracture properties of pressure vessel steel

In this paper, various methods have been used to measure the effects of prestrain on the fracture toughness of 20 g steel experimentally. Based on elastic-plastic FEM analysis, the relationships between crack tip opening displacement _T and the maximum strain _maxc have been obtained and the effects of prestrain _p on the critical fracture strain _maxc have been examined. At the same time, based on the Rice-Tracey's void growth model [4], the cause of the void formation ahead of the crack tip, the condition of the principal crack propagation and the effects of prestrain _p on the fracture properties of 20 g steel were investigated. For ductile material there was a maximum value of V_G ahead of the crack tip that was the cause of the void formation in that place. It is believed that when the maximum value of V_G ahead of the crack tip reaches a critical value, it may be the principal crack propagating condition for high ductile material.