Railway axle failure investigations and fatigue crack growth monitoring of an axle

Railway axles have typically been designed for an infinite life, with a normal maximum service life of 40 years. However, some axles have failed in service. This paper describes five axles that have failed in service and the consequences of the failures, and suggests causes of the failures. Most had resulted from the slow growth of fatigue cracks across the axles. Electrical arcing, corrosion and stress corrosion cracking had initiated the fatigue cracks. An axle containing small cracks has been returned to service and the crack sizes regularly monitored. It is concluded that more information on axles is required and it is recommended that information on the loads, stresses and materials data should be obtained so that guidance for the design of axles can be updated. It is also recommended that earth return brush seats should be regularly tested for cracks and all axles regularly visually inspected for corrosion.