FEASIBILITY OF AN ACOUSTIC EMISSION BASED STRUCTURAL HEALTH MONITORING FOR RAILWAY AXLE UNDER FRETTING FATIGUE DAMAGE

During service of railway axles, fretting fatigue damage can occur because of micro-sliding between the wheel hub and the axle press-fit seat. It is an important issue for fatigue life assessment since it can trigger crack initiation and consequent failure. 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 with respect to scheduled inspections. This paper investigates the feasibility of an Acoustic Emission based Structural Health Monitoring system applied to railway axle subjected to fretting fatigue damage. Experiments were performed on a full-scale axle using a Vitry test rig, i.e. a three point rotating bending test, with one acoustic-emission sensor coupled at the free end of the axle. Preliminary results are introduced and are found to be consistent with damage evolution.