Leak-before-break (LBB) assessment of nuclear piping involves ductile fracture analysis of pipes or elbows with postulated through-wall cracks. Due to the fact that the crown part of an elbow is one of the positions that crack initiation occurs in most frequently, the calculation of J-integrals to investigate fracture behavior are important research topics. This paper proposes a 3-D finite element model of an elbow embedded with an axial through-wall crack to estimate the J-integral parameters under bending moment. The J-integral values can be calculated by using ABAQUS and taking into account the effects of geometrical and model of material in non-linear analysis. The results show that the non-linear deformation and contact condition of crack surfaces play important roles for the J-integral values. In addition, the J values estimated by the proposed model are more conservative and realistic than previous studies.

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James performed a series of experimental study on austenitic stainless steels and suggested an equation for assessing the influences of temperature, stress ratio and loading frequency on the fatigue crack growth rate. Authors have studied the effect of either loading frequency alone or of temperature alone on the fatigue crack growth rate by employing the mechanical behaviors of material. In this study, the mechanical behaviors of material are employed for evaluating the combined effect of loading frequency and temperature. Using the derived dimensionless functions of yielding stresses and Young’s modulus, the equation represented the combined effect of loading frequency and temperature on fatigue crack growth rate of 304SS was proposed.

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