Fatigue failure analysis and life prediction of welded aluminum alloy frames suspended from high-speed EMU.

• The field tests were carried out for more than two years on Chinese high-speed railway lines, it is found that the main failure cause of the BBF is the resonant vibration of 8–20 Hz which excites the first-order natural mode of the frame. • It is found that the measured data are quite different from the IEC61373 standard, it is necessary to reassess whether the limits in the standard are safe or not for Chinese high-speed railway lines. • The bolster exhibits obvious non-Gaussian characteristics, it could be inferred that the Gaussian signal maybe not always suitable for the input load spectrum. Aiming to solve the failure problem of welded frame suspended under high-speed EMU, a long-term tracking test was carried out. The modal resonance of 8–20 Hz is the main cause of structural failure. The characteristics of the in-service vibration environment and the difference with the standard load spectrum are analyzed. The measured load spectrum exceeds the IEC61373 standard load spectrum in the frequency range of 10–20 Hz and 30–120 Hz. Meanwhile, the kurtosis of measured acceleration signal does not always follow the Gaussian distribution for the carbody bolsters, and the acceleration and dynamic stress amplitude of the bolster and suspension equipment frame increase more with higher train speed. After a finite element model with welded joints was developed to evaluate the fatigue life, an optimized prototype BBF was designed. The reliability of the optimized structure is verified by rig test. The optimized structure avoids 8–20 Hz resonance and meets the test requirements. [ABSTRACT FROM AUTHOR]