The local brittle zone (LBZ), which has lower tensile properties as well as lower fracture toughness than base metal and weldment, can occur on the heat affected zone (HAZ) of some nuclear components made of low alloy steels due to the carbide coarsening by multi-pass welding and post-weld heat treatment. These variations of material strengths across the welds due to the LBZ can produce strain concentrations when the stress amplitude is large enough to cause cyclic plastic flow. But, it is difficult to find the previous researches about a relation between the fatigue life of LBZ on real nuclear components and plasticity. So, in this study, the microstructures and tensile properties of HAZ on nuclear components are predicted by using the semi-analytical method, and the fatigue lifetimes of welds on nuclear components with the LBZ are evaluated by the finite element method considering the local plasticity and the variations of tensile properties, and the fatigue analysis procedure of ASME B&PV Code Sec.III. Finally, the effect of LBZ on nuclear components on fatigue lifetime is reviewed.

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