Cleavage fracture of notched bar at low temperature by using local approach

摘要

Beremin cleavage fracture model has been widely used to predict cleavage fracture probability of structures, but it is seldom used to study the effect of structure's size on cleavage fracture load. This paper uses this local model to predict the effect of notch size of notch bars on cleavage fracture load. In order to complete the study, the physical meaning of different cleavage fracture is discussed firstly. It is found that the to pressure vessel carbon-manganese steels, there are two cleavage fracture probability values we should pay more attention to, one is about 44%, at which the corresponding Weibull stress is the average Weibull stress, the other is about 61%, at which cleavage fracture most take place. Based on this, curves of cleavage fracture loads of notched tensile bars versus notch size at the two values of cleavage fracture probability are predicted. The experiments show that the average cleavage fracture load is almost equal to the predicted cleavage fracture load corresponding to 44% cleavage fracture probability. Predicted result shows that the cleavage fracture load increases rapidly with the radius of notch increases firstly and then increases and decreases slowly with the radius of notch increases. Fracture experiment of notched tensile bars proved the trend true.