With the continuous advancement of aerospace technology, ensuring the reliability of aerospace engines after testing is critical. While various methods exist for assessing fatigue life, non-destructive prediction based on in-situ X-ray diffraction (XRD) residual stress analysis remains underexplored—particularly for low-cycle fatigue in welded joints. This study proposes a novel approach that uses in-situ XRD to monitor residual stress evolution under fatigue and creep loading in gas tungsten arc welding (GTAW) joints of aerospace-grade austenitic stainless steel SUS321. Through metallographic observation, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and in-situ XRD measurements, we demonstrate a strong correlation between longitudinal residual stress at the weld center and fatigue life. Under fatigue loading at 60% of the ultimate tensile strength (UTS), longitudinal residual stress transitions from tensile to compressive with increasing cycles, and fatigue fracture occurs once residual stress approaches base metal levels (~0 MPa). In contrast, under creep loading, no clear trend in Y-direction residual stress was observed, limiting its utility for creep life prediction. This work establishes a reliable, non-destructive framework for evaluating the service life of welded aerospace components, offering a new methodology beyond conventional practices.
Li et al. (Fri,) studied this question.