Abstract
Elastic-plastic stress analysis of a circumferential crack in round steel bars under mode I, mode III and mixed mode (I+III) loadings was conducted by the finite element method. The J-integral was found to be the most appropriate fracture mechanics parameter for characterizing the fatigue crack propagation behavior of mode I, mode III and mixed mode (I+III) cracks. In this paper, two methods were used for the estimation of J-integral value of mixed mode (I+III). The one is the simple estimation method, and the other method is the energy method. The J-integral value under the mixed mode (I+III) obtained by the simple method was in good agreement with that estimated from the energy method in the range of applied displacement u≤0.035mm and applied twist angle θ≤0.014rad.
