Relation of fracture mode to loading type in a mixed-mode crack

It has been shown that, in a mixed-mode crack, not only mode I (opening type) fracture but also mode II (shearing type) fracture can occur under some loading condition. Therefore, we previously proposed the fracture criteria for mode I and mode II fractures based on the CED (crack energy density) in an arbitrary direction, Eφ, with the criterion for judging the fracture mode. In this paper, at first, based on the above fracture criteria, the relation of the fracture mode to loading type in an elastic mixed-mode crack is discussed, changing the loading type in the neighborhood of a crack tip represented by stress intensity factors KI and KII from mode I to mode II continuously. Subsequently, the influence of plastic deformation on the fracture mode is also discussed based on the change of Eφ with the increase of plastic deformation. Moreover, through comparison between the results of fracture experiments of the specimen with an inclined crack under tensile type loading and the corresponding results predicted by the criteria, the influence of plastic deformation on a fracture accompanied with small scale yielding is studied.