Fracture behavior of pipes with local wall thinning is very important for the integrity of nuclear power plant. Then we studied on the fracture behavior of straight pipe and elbow with local wall thinning. For the straight pipe, failure mode, limit load and allowable wall thinning limit based on plastic deformation ability have been studied systematically. The tested straight pipes were 22 specimens. The failure mode was divided into four types; cracking, local buckling, ovalization and plastic collapse (ovalization+buckling). Maximum load was successfully evaluated using plastic modulus and modified flow stress, in spite of failure mode. For the elbow, plastic collapse and low cycle fatigue fracture by reverse loading have been tested using 10 specimens. Observed failure modes were ovalization and local buckling under monotonic loading, and were local buckling and cracking under cyclic loading, especially local buckling promoted crack initiation. Test results were compared with ASME design curve and allowable limit of local wall thinning was discussed.
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