A new damage detection technique for rails based on wave propagation

Rails maintenance is becoming a critical issue because of the increase of the traffic and the train speed, which amplify the risk of catastrophic failures. A methodology, based on wave propagation theory, aimed at detecting damage in rails is presented in this paper. The damage detection algorithm is based on the assumption that the rails behave as a wave guides and stress waves may travel alongside the rail length without being reflected unless they meet discontinuities (damages). The Wave Propagation Based Damage Detection (WPBDD) algorithm proposed is a two steps technique. In the first step the travel time of a perturbation wave, generated by a train passage, from its arrival to the sensor locations to the discontinuity and back to the sensor, is measured by a Time Correlation Function (TCF) evaluated using the wavelet transform. The second algorithm locates the damage sites using a Ray-Tracing (RT) algorithm. The WPDDD algorithm has been designed to use indifferently either body waves (P and S waves) or surface waves (Rayleigh waves). The technique proposed aimed at the identification of single and multi-site rolling contact fatigue damages was tested on a numerical test case.