Railwheel interaction monitoring using Acoustic Emission: A laboratory study of normal rolling signals with natural rail defects
This paper presents a laboratory study on the Acoustic Emission (AE) generated during railway wheelrail track interaction, with a view to developing methods of in situ railwheel interaction monitoring using rail-mounted sensors. It is known that the physical processes of impact and wear generate AE and it was therefore expected that axle loads, speed and traction would influence the AE generated by an interaction and that the characteristics of normal interaction would be affected by wheel and/or track defects and/or any misalignment between rail and track. A set of laboratory experiments were carried out on a scaled test rig to characterise the continuous AE generated by a wheel rolling on a rail and, secondarily, to assess the effect on the AE characteristic of the natural defects present on the contact profile of the rail. The natural defects were of a relatively minor nature and their assessment serves as part of the calibration of background AE for experiments with more significant simulated defects. A simplified analytical model, devised for AE waves propagating from a moving source, based on vehicle speed and wave damping coefficients, has been developed for the test track and fitted to the measured results. As a wheel rolls towards a sensor and then away from the sensor the measured AE generally rises and falls in a predictable way. The effects of wheel and rail surface features were found to introduce deviations from this background, and a method to identify the location of surface defects, based on identifying peaks above the background is also demonstrated.
railwheel interaction acoustic emission rail defects