Detection of loose fasteners in a third rail support assembly using a wavelet analysis

摘要

The function of the third rail is to supply power in a mass rapid transit system through a semi-continuous rigid conductor placed alongside the rails of a railway track. Although it is fully segregated and fixed along the floating slab tracks (FSTs), which is used to insulate the surrounding buildings from vibration of the passing trains, the FSTs and the third rail are still prone to reverberation. Precisely because of this reason, many of the fasteners used to tighten the claw to the insulator eventually become loose, dislodging the claw holding the third rail and causing part of it to sag. This, in turn, can damage the collector shoes and causing the trains to lose power. Hence, the root of the problem is due to loose fastener in the third rail system. In this study, the dynamic response of a vehicle-rail interaction system is analysed, and the results show that the natural frequency of the interactive system decreases as a vehicle passes through a loose support. Based on this fact, a detection algorithm based on wavelet analysis is proposed. Numerical verification for different cases is produced and analysed, and the results show that it is plausible to use the proposed method in practice to detect loose fastener in a third rail support.