P91 heat-resistant steel pipes are widely used at high temperature in power plants and nuclear power plants. The service condition and manufacturing process may produce defects of local wall thinning, which may result in stress redistribution of the pipes during the service process at elevated temperature. For the purpose of understanding the creep stress and strain accumulation affected by local wall thinning geometries under creep condition, three groups of models were calculated, using three-dimensional models based on finite element analyses (FEA) codes ABAQUS. In this study, monotonic internal pressure was conducted on P91 full-scale steel pipes at 625°C, with local wall thinning located at the inner surface. Then, the creep strain and stress of pipes after 100,000h could be obtained corresponding to different models. Based on the analysis, the figures of creep stress and strain varying with defect geometries were plotted. Then, the stress and strain of pipes with local wall thinning affected by defect geometries, including different defect depths, different defect axial lengths and different defect hoop angles, were discussed. The results indicate that creep stress and creep strain increase with defect geometries. The variation laws have been summarized. The research results can provide the possibility on safety assessment and structure integrity analysis of the pipe with local wall thinning at high temperature effectively.

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