Ultrasonic guided wave monitoring of an operational rail track

Abstract

An experimental monitoring system was installed on an operational heavy haul rail track. The system used two piezoelectric transducers mounted under the head of the rail to transmit and receive ultrasonic guided waves in pulse-echo mode and data were captured over a 2-week period. An artificial defect was introduced by glueing a small mass under the head of the rail at a distance of 370 m from the transducers. The size of the signal reflected by the mass varied as the glue joint deteriorated. The measurements were reordered to simulate a monotonically growing defect. The pre-processing of the captured time signals included averaging, filtering, phased array processing, dispersion compensation, signal stretching and amplitude scaling. Singular value decomposition and independent component analysis of the data were performed. Independent component analysis, with dimension reduction achieved by retaining only the larger principal components, produced the best defect detection. The defect signature was separated as an independent component, and the weight of this component increased monotonically. The results indicate that a transverse defect in the rail head could be detected and located at long range by a system comprising only two transducers. The variation of the signals due to changing environmental and operational conditions limits the size of defect that can be detected, but it is expected that even a relatively small defect, which is significantly smaller than the critical size, would be detected.

Multi-feature integration and machine learning for guided wave structural health monitoring: Application to switch rail foot

“…In guided wave monitoring systems for rail tracks, previous studies adopted longitudinal wave probes, such as longitudinal piezoelectric transducers, as the actuator and receiver. 10,26,53 However, in practical EOCs, such as those in which rail surfaces are covered with liquid loads like water or lubricating oil, this method will not be effective since the guided wave mode generated by the longitudinal piezoelectric transducer has a significant out-of-plane displacement. Figure 8(a) and (b) presents the influence of water on practical raw guided wave signals collected by a piezoelectric transducer, which was mounted under the switch rail foot and worked in pulse-echo mode.…”

“…25 Recently, the independent component analysis (ICA)-based algorithm has been employed in the SHM of switch rails. 10,26 However, because it starts from a random initial set of weight vectors, the detection results of the rails may be different if the algorithm is performed repeatedly, which usually leads to false negatives or false positives in practical applications. In addition, the independent component belongs to a single feature, which may overlook discriminative information of damage conditions and has difficulty comprehensively characterizing the guided wave behavior of various types of damage.…”

Rail Diagnostics Based on Ultrasonic Guided Waves: An Overview

“…2. Land-based systems [9,[50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67]-The employed equipment is placed on the ground near to the railway infrastructure, and its actuators and sensors are attached to the rails under test. The detection of defects in the rails is achieved through a pulse-echo approach.…”

“…For example, the use of electromagnetic acoustic transducers (EMATs) has been taken into consideration [55]. In the meantime, the reflection characteristics of defects and their dependence on time and environmental conditions are under evaluation [9,56,57,65].…”

Selective generation of ultrasonic guided waves for damage detection in rectangular bars

“…Apart from pipes 24 and rails, 23,26–28 few waveguides with a bi-dimensional cross section have been studied. The semi-analytical finite element (SAFE) method offers a great potential to predict guided modes propagating along waveguides with arbitrary cross sections 29–32 and, in particular, rectangular cross sections.…”