A novel condition monitoring system has for the first time enabled reliable extraction from service and detailed forensic examination of failing rail axle bearings, before the usual catastrophic destruction of the evidence. Computed Tomography has been used to produce a map of the damage allowing targeted sectioning of subsurface cracking. Traditional metallographic techniques have revealed large white etched layers associated with the subsurface cracking, while observations with a scanning electron microscope have confirmed rolling contact fatigue crack propagation, possibly initiated from pre-existing electrical arcing damage of the raceways
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