Fatigue crack analysis in a bolster of a metro train

A Metro train is one of the heavily designed structures and is capable of having long life span of 20-30 years. The occurrence of fatigue crack in the bolster of a metro train is very unusual. In this paper, a series of fatigue damage assessments on a bolster was performed to understand the possibility of fatigue crack initiation under normal operating conditions. Additionally, fatigue crack growth analysis was performed to check for the possibility of unstable crack growth during normal service operation. In the fatigue damage assessment, minimum safety margin of 2.71 was calculated until the end of design life span of 30 years. In the crack growth analysis, operable years of 6.9 was calculated even a 30 mm-sized-initial-crack grows to unstable crack growth. From these two results, we can conclude that the cracks found at the bolster thought to initiate due to accidental over loadings during service, and even though the 30 mm-sized-initial-crack can be detected before it brings unstable crack growth considering maintenance period of normally every 3 years.