응력비 변화에 따른 혼합모드 피로균열 전파거동

Most cracks in the structure occur under mixed mode loading and those fatigue crack propagation behavior heavily depends on the stress ratio. So. it is necessary to study the fatigue behavior under mixed mode loading as the stress ratio changes. In this paper. the fatigue crack propagation behavior was respectively investigated at stress ratio 0.1, 0.3, 0.5, 0.7 and we changed the loading application angle into 0˚,3D˚,60˚ to apply various loading mode. The mode I and II stress intensity factor of CTS specimen used in this study was calculated by the displacement extrapolation method using FEM (ABAQUS). Using both the experiment and FEM analysis, we have concluded the relationship between crack propagation rate and stress intensity factor range at each loading mode due to the variation of stress ratio. Also, when the crack propagated under given stress ratio and loading mode condition. we have concluded the dominant factors of the crack propagation rate at each case.