Analysis on the Rupture Failure of Railway Cross Rails

In this paper the failure of two railway cross rails that ruptured during a simulation test under alternating load was investigated. The railway cross rails were made of alloy steel. Visual inspection found that the macrofracture surfaces of the ruptured rails were very flat without macroscopic plastic deformation, and there were conchoidal structures on the fractures that were covered with corrosion products. These are the typical macrofracture characteristics of corrosion fatigue cracking. Tensile and impact tests showed that the mechanical properties of the steel plates met the proper specifications. Optical microscopy found the microstructure of the steel also qualified. Macrofracture analysis revealed that the two ruptures originated at the transitional line from flat plane to camber area on the outer surface of the steel plates. Microfracture observations showed that there were some machining notches near the rupture origins. It was concluded that there was localized stress concentration near the transitional line that was caused by machining notches or the transition structure from the flat plane to camber or by both. The localized stress concentration induced the initiation of a fatigue crack under alternating load, which propagated by corrosion fatigue under alternating load in a humid atmosphere.