On locations initiating cleavage fracture in precracked specimens of low alloy steel and weld metal

On the basis of a model of an `active zone' for initiating cleavage fracture proposed by authors, the distributions of cleavage initiation location in precracked specimens are explained, and the factors affecting cleavage initiation locations are analyzed. The change of the length of the active zone with applied load determines the distributions of cleavage initiation locations. With increasing temperatures, the distance X_f from precrack tip to locations initiating cleavage fracture and its scatter increase, and the lower boundary of X_f increases slowly, and the scatter is mainly caused by the rapid increase of the upper boundary. With decreasing the strength of the weakest constituent in steels and increasing their number, the minimum distance X_min and the average distance for initiating cleavage fracture will decrease and the maximum distance X_max will increase, and the corresponding toughness values will be decreased.