Prediction of prestraining effect on fracture toughness of high strength structural steel by local approach

In the present study, the tension and fracture toughness tests on high strength structural steel of Q420 were carried out in different conditions of non-prestraining and prestraining. The results indicated that the prestrain increased the yield stress and tensile strength, but decreased the fracture toughness. Meanwhile, the local parameters m and σ_u controlling the brittle fracture were obtained using finite element method (FEM) analysis. Based on the Weibull stress fracture criterion, the prestraining effect on the fracture toughness was predicted from fracture toughness results of the virgin material by the local approach. The prediction was in good agreement with the experimental results. It certified that the critical Weibull stress obeys the two-parameter Weibull distribution in the local approach, and the fracture behaviour of the material with prestrain can be characterised well by the local approach.