Fatigue performance of bogie weld roots: Failure analysis and numerical modeling

In engineering practice, accurately identifying root failure mechanisms and quantitatively evaluating fatigue performance improvements in the absence of load spectrum conditions remains a challenge. This study proposes a framework integrating crack path simulation, traction-based failure analysis, and quantitative structural improvements to systematically address this issue. Using the welded frame as research subjects, a numerical model of potential multi-crack paths is established to localize stress concentration zones, while the traction force method is presented to reveal the mechanical driving mechanisms of fatigue initiation. The results show that high traction forces at the weld throat root induce bending stresses that drive both fatigue initiation and crack propagation. The fatigue failure position, crack initiation sites, and propagation paths identified through simulation are consistent with actual fatigue cracking. The proposed damage-equivalence method reveals that increasing the weld throat thickness reduces the stress concentration by 46.7% and extends fatigue life by 7.17 times. These results offer a robust reference for the diagnosis and mitigation of weld root failures.