An Acoustic Emission based Structural Health Monitoring Approach to Railway Axles

Considering railway axles, classical fatigue damage can occur at the body as a consequence of corrosion or ballast impacts, while fretting damage can occur as a result of micro-sliding between the wheel assembly and the press-fit seat. As safety critical components, railway axles, whose failure can lead to unacceptable human losses, are periodically inspected by means of well-established non-destructive techniques (typically ultrasonic and magnetic particle inspections) usually requiring expensive service interruptions. On the contrary, as shown within the aeronautical field, a condition-based maintenance can improve the safety and at the same time minimize costs respect to scheduled inspections. This paper investigates the feasibility of an Acoustic Emission based Structural Health Monitoring approach applied to railway axles subjected to classical and fretting fatigue damages. Experiments were performed on full-scale axles using a Vitry test rig, i.e. a three point bending test, with one acoustic-emission sensor coupled at the free end of the axle. Results are found to be consistent with damage evolution.