A Method Of Fracture Failure Probability Analysis Based On Numerical Simulation

A508-? steel is a standard material for pressure vessels.The existing research results show that it has an obvious ductile brittle transition zone.In this temperature range,the fracture toughness measured by experiments shows a probability distribution.In this paper,PCVN,W,0.5CT and 1CT samples are taken as research objects.Based on the numerical simulation,the fracture toughness and failure probability of A508-? steel in the ductile brittle transition zone are analyzed.Based on the J-Q theory,the stress field at the crack tip is divided into three stages:small strain stage,transition stage and finite deformation stage.In the finite element simulation,the crack growth is restrained,and the fracture toughness distribution interval is determined based on a series of theories such as J resistance curve,the energy flux flowing into the crack tip and so on.The concepts of virtual radius and real radius are introduced to improve the accuracy of fracture toughness distribution,and the influencing factors of real radius are analyzed.The upper bound of fracture toughness interval is used to replace the size parameter of fracture toughness to determine the cumulative failure probability,which is basically consistent with the cumulative failure probability curve predicted by the experimental solution,and the distribution curve of cumulative failure probability is highly consistent with the KJC vs Weibull stress curve,which reflects the change of restraint degree during the loading process.The parameters of Beremin model are analyzed briefly,m and ?u is mainly determined by the combination of samples,and the parameters obtained by the combination of different samples for the same sample are basically different.For 0.5CT sample,the value of m is in the range of 4-30,but it has no effect on the judgment of cumulative failure probability.When the cumulative failure probability is around 0.6,the corresponding fracture toughness is basically the same.