Effects of material brittle/ductile property and crack tip loading type on fracture mode of a mixed-mode crack

It was shown that the fracture mode of a mixed-mode crack in a homogeneous ductile material changes from mode I (opening) type to mode II (in-plane shear) type or vice versa by changing the loading type in the vicinity of a crack tip. The characteristics of this fracture mode change may depend not only on the loading type in the vicinity of a crack tip but also on the brittle/ductile property of a material. From this point of view, the fracture experiments of the specimens with an inclined crack made up by using acryl resin and aluminum alloy are carried out, in the present study, under tensile type and shearing type external loads. It is confirmed first through the experiments that the different fracture modes can be realized between the specimens of above two materials even under the same loading type in the vicinity of a crack tip. Moreover, the CED in an arbitrary direction is evaluated through the finite element analyses corresponding to the experiments. Finally, it is demonstrated that the effects of brittle/ductile property of a material and loading type in the vicinity of a crack tip on fracture mode of a mixed-mode crack can be grasped in a unified way by the criterion based on the CED in an arbitrary direction.