Loading type dependence of fracture mode of a mixed-mode crack

It has been shown that not only mode I (opening type) fracture but also mode II (shearing type) fracture can occur in a mixed-mode crack under some loading type. 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, E_φ, 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 the 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 K_I and K_II 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 E_φ with the increase of the amount of plastic deformation. Moreover, through the 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 the fracture accompanied with small scale yielding is studied.