Applicability of reference stress method for J-integral evaluation to failure assessment curve

In the rules on fitness-for-service for nuclear power plants of the Japan society of mechanical engineers (JSME), the two-parameter approach is prescribed for failure assessment of defects. In JSME rule, the failure assessment curve (FAC) for the two-parameter approach has to be determined using J-integral value when existing FAC is not available. The reference stress method can estimate J-integral value using stress-strain relation of the material. However, the accuracy of estimation depends on the limit load used for an evaluation of the reference stress. In this study, applicability of several limit load solutions was investigated by comparing with results of elastic-plastic finite element analyses. Pipes containing axial or circumferential flaw were analyzed under internal pressure or bending load. Appropriate limit load solutions were suggested for evaluation of FAC, based on analyses of 2880 cases for different flaw and pipe geometries and materials used in nuclear power plants. (author)