Abstract
In this study, the mixed II+III mode fatigue test is conducted using a single-axis testing machine. The test specimen is a four-point-shear specimen with a side crack. After the test, the fracture surface is observed using SEM (Scanning Electron Microscope) and the characteristic feature of the mixed mode fatigue surface is obtained. The three-dimensional FEM (Finite Element Method) analysis is conducted and KII and KII are evaluated. For mode II+III fatigue test, the mode I static load is give to avoid the contact of crack surfaces. By the SEM observation, it is found that the contact does not occur during the fatigue test. The fatigue crack grows faster at the surface of the specimen than that of inside of the specimen. The crack growth direction is straight along the original crack direction, which is different from the predicted direction by Erdogan-Sihcriterion. The fracture surface shows a characteristic feature of shear fatigue crack, on which many thin laminas are piled up along the normal direction to the crack front. It agrees with what proposed by Otsuka et al.
