Abstract: To investigate the influence of different plug-welded configurations on fatigue crack growth behavior and to establish a remaining useful life prediction model, four typical plug-welded joints were fabricated using Q350EWR1 weathering steel：single-point, two-point in series, two-point in parallel, and three-point in series. Axial tension-tension fatigue crack growth tests were conducted on these specimens. Digital image correlation was employed to capture the surface strain fields during crack propagation. The stress intensity factors were calculated through Franc 3D finite element analysis combined with the M-integral method, while the crack growth rates were determined using the seven-point incremental polynomial method. A life prediction model was then developed based on the Paris law. The results show that cracks initiated at the fusion zone edge in all specimens. In series configurations, edge welds exhibited pronounced stress concentration and greater damage, whereas parallel configurations achieved more uniform stress distribution and higher load-carrying efficiency. For all four plug-welded configurations, the remaining useful life prediction models achieved coefficients of determination (R²) exceeding 0.92, enabling reliable quantitative predictions of service life across different joint types. These findings provide a scientific basis for evaluating joint safety in service and formulating maintenance strategies in engineering applications.

Key words: plug-welded joints, fatigue crack growth, digital image correlation, stress intensity factor, remaining useful life prediction model