Reasons for Fatigue Fracture of ω-Shaped Spring Rod for a Railway

The ω-shaped spring rod for a railway fractured when the load cycle was about 3×106 times in a fatigue test. The reasons for spring rod fracture were analyzed by chemical composition analysis, hardness testing, microstructure observation, and fracture morpholohy examination. The results show that a large stress concentration happened on the fulcrum at the end of tail of the ω-shaped spring rod because the alternating load in this location was larger than in other areas during the fatigue test. Moreover, there were corrosion pits on the fulcrum. These two reasons promoted the initiation and development of the fatigue cracks, which eventually led to fatigue fracture failure of the ω-shaped spring rod.