Fatigue fracture and probabilistic assessments of a cone and pipe welded structure of stainless steels.

Probabilistic assessments are important for weldments due to large scatters in the fatigue strength. Using thin‐walled cone‐pipe welded joints of stainless steels, fatigue tests under bending loads were carried out. The test data were statistically analyzed with the Benard's approximation, Gaussian, 2P‐Weibull, and 3P‐Weibull distributions. Stress–life curves at different failure probabilities by a uniform scatter band model were obtained. The metallographic structures were investigated, and the stress concentration states were analyzed to elucidate the causes of the strengths and scatters. In the high‐cycle fatigue regime, the 3P‐Weibull distribution was most matched with the Benard's approximation, and the coefficient of determination was 0.9817. The microstructure of the weld metal with a high weld opening angle was mainly ferrite phase with 20% austenite distribution, which had the high strength. The stress concentration factors depended on the weld opening angle, indicating the main factor that affected strengths and scatters. Highlights: A uniform strength scatter band model was used for failure probability evaluations.The 3P‐Weibull estimation was most matched with the data in bending fatigue tests.The fatigue strengths and scatters mainly depended on the weld opening angle.The microstructures around the notch affected the fatigue strengths and scatters. [ABSTRACT FROM AUTHOR]

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