Abstract
Welded joints are widely used in the pipeline connection of nuclear power plants. Defects in these joints are an important factor leading to the failure of welded joints. It is critical to study the fatigue crack growth and life prediction methods for the welded joints with defects, to reduce their likelihood. In this paper, we present our study of the uncertainty of fatigue crack propagation and probabilistic life prediction for welded joints of nuclear stainless steel. The standard compact tension (CT) specimens were fabricated according to the American Society for Testing and Materials (ASTM) standard. Fatigue crack propagation tests with different stress ratios were performed on CT specimens, using the Mei Te Si (MTS) fatigue test system. A fatigue crack propagation rate model considering the uncertainty of material parameters, and based on the Paris formula and crack propagation experimental data, was established. A probabilistic life prediction method based on Monte Carlo simulation was developed. The fatigue crack propagation prediction result of a CT specimen was compared with the actual tested result, to verify the effectiveness of the proposed method. Finally, the method was applied to an embedded elliptical crack in welded joints of nuclear stainless steel, to predict the fatigue crack growth life and evaluate the reliability.
Highlights
As of April 2020, 47 nuclear power units have been built and put into operation in China [1].With the increase of the service time of nuclear power units, the risk of failure of nuclear safety related components is increasing
Lu et al conducted fatigue crack propagation research on nuclear casting austenitic stainless steel; the results showed that the crack growth rate, da/dN, has a strong correlation with load ratio, R [2]
The results showed that the prediction curve of fatigue crack growth behavior simulated by Monte Carlo (MC) can accurately describe the real fatigue crack growth behavior of specimens
Summary
As of April 2020, 47 nuclear power units have been built and put into operation in China [1]. A study is necessary to investigate the fatigue crack growth behavior of the welded joint and the life prediction method of a pipeline with defects. To predict the fatigue crack growth life more accurately, the randomness of fatigue crack growth parameters in welding parts should be considered, and the probabilistic statistics and mechanical analysis methods should be used to solve the fatigue analysis problem. The crack propagation of welded joints of nuclear stainless steel prepared by a specific welding procedure was investigated to obtain the material parameters for life prediction. A probabilistic life prediction method, which combined the crack growth parameters distribution function, Paris formula, and Monte Carlo method, was developed to predict the life of welding joints with defects
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