Abstract
A permanently installed Ultrasonic Broken Rail Detection system monitors the Sishen-Saldanha railway line in South Africa [1]. The system detects complete rail breaks at long-range using guided wave ultrasound. For the system to be reliable, its damage detection performance must be evaluated under actual environmental and operational conditions (EOCs). However, obtaining monitoring data containing damage reflections is virtually impossible since detected defects in operational rail track sections are immediately removed and replaced with new rail. Laboratory experiments are also not possible since end reflections from short sections of rail dominate the response. Therefore, damage signals can only practically be obtained from numerical simulations. The simulated damage signals should be realistic and include varying EOCs, especially temperature variations. This paper aims to demonstrate a procedure to model temperature variations in ultrasonic signals. The temperature model and the modelling framework developed in [2] are used to simulate reflections from welds. The framework models the excitation, propagation and scattering of GWs from discontinuities by employing a hybrid model based on the 3D Finite Element method and the 2D Semi-Analytical Finite Element method. The simulated results are validated using experimental measurements collected from an operational rail at different temperatures.
Highlights
The Council for Scientific and Industrial Research (CSIR) and Maritime Institute of Technology (MIT) identified the need for a reliable monitoring system for defect detection in rails
Since the installation of the Ultrasonic Broken Rail Detection (UBRD) system on the Sishen-Saldanha Ore line in April 2016, seven rail breaks and several major flaws [1] recorded as false alarms have been reported
The numerical models that form the basis of the modelling framework are the Semi-Analytical Finite Element (SAFE) method for modelling wave propagation; two hybrid methods couple SAFE and traditional 3D Finite Element method (FEM) to model guided waves (GWs) excitation and scattering from reflectors, respectively
Summary
The aim is to guarantee a solution to the problem of train derailments caused by broken rails. This has led to a permanently installed Ultrasonic Broken Rail Detection (UBRD) system, which monitors the Sishen-Saldanha railway line in South Africa [1]. If the receive station does not detect the transmitted signals, an alarm indicates a broken rail, and train operation stops to prevent derailments. Since the installation of the UBRD system on the Sishen-Saldanha Ore line in April 2016, seven rail breaks and several major flaws [1] recorded as false alarms have been reported. Detecting a crack before the rail breaks would avoid these derailments and allow condition-based maintenance
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