Research on fatigue life and damage tolerance design of metro bogie frame.

Traditional evaluation of accumulative damage calculates fatigue life of metro's bogie frame based on material properties and stress spectrums, which has limitation on evaluating accurate life due to non-crack assumption. In this paper, crack propagation is numerically simulated to give more accurate result, showing that a crack's initial geometry has great effects on reducing fatigue life cycles, and the count of cycles required for a crack with an initial size of 3 mm and 5 mm to propagate to an equivalent crack length is 68.5 % and 48.3 %, respectively, in comparison to a 2 mm initial crack size. On this basis, damage tolerance analysis is introduced for optimizing anti-fatigue evaluation strategy and maintenance periods. The results suggest that accumulative damage and damage tolerance methods should be comprehensively combined for staging evaluation of bogie frame's fatigue life, by establishing a control boundary between the initial crack and the critical crack, proactive repairs can be executed, which facilitates the ongoing usability of the bogie frame, leading to an extension of its effective operational periods. [ABSTRACT FROM AUTHOR]