抄録
Fracture tests under the mixed I, II and III mode conditions with different mode ratios have been carried out, by adopting cylindrical notched specimens and introducing the initial crack by a cyclic axial loading. A special jig has been developed so that any mode ratio can be obtained by tensile and torsion loadings. Based on the effective maximum strain energy release rate and the experimental results, the fracture criterion of a crack under mixed I, II and III modes has been proposed. It is found that the fracture direction can be well predicted by the effective maximum strain energy release rate, and the fracture occurs when the effective maximum strain energy release rate reaches the fracture toughness G_C, which is related to K_<IC>. The relationship between K_<IC> and K_<IIIC> for a homogenous material has also been clarified theoretically and experimentally. Through the comparison of the elliptical criterion and the criterion proposed in this study, it is found that the experimental results agree better to the criterion based on the effective maximum strain energy release rate. Moreover, the criterion proposed is continuous with the σ_<θmax> criterion for the mixed I and II modes condition, and also contains the pure mode fracture criterion.
