Fretting Wear in Selected Elements of Rail Vehicles

The wear of vehicle elements during operation is a natural phenomenon. A dangerous situation occurs when elements more crucial than others wear unexpectedly. Such an element in rail vehicles is, for example, a wheel set. Its main task is to run the vehicle in the track, which directly influences the safety of the journey. Any premature or unexpected damage will lead to train derailing. Then hundreds of lives may be lost. The load on the wheel set from the vehicle weight and the oscillatory micro displacement of the wheel in relation to its axle during travel will be conducive to premature wear. Those conditions will cause the development of fretting wear, whose implication may be fatigue wear or the loosening of the wheel/axle joint. In this article, the results of fretting wear tests conducted in a shaft/sleeve forced-in joint are presented. The results of those tests, given that the relevant probability conditions are met, can be successfully compared to the real wheel/axle joint. The wheel set operation conditions, which will be conducive to the initiation of the development of fretting wear, have been discussed. Test results are presented in the photographs showing the axle seat with an area affected by wear. Both those places, and the place of contact between the connected surfaces, were subjected to micrographic examinations with a view to identifying damage comprised by fretting. Macrographic observations demonstrated fretting on either side of the shaft axle seat, which phenomenon comprises, for example, abrasive wear and adhesion. Visible are micro cracks and material build-ups, which became plastically deformed and oxidised.