A new damage detection technique based on wave propagation for rails

Abstract

This paper presents a novel damage detection technique, tailored at the identification of structural surface damage on rail structures. The damage detection, proposed in this paper, exploits the wave propagation phenomena (P, S, Rayleigh and guided wave velocities) by identifying discrepancies, due to damage presence, in the dynamic behaviour of the structure. The uncorrelations are generated by waves reflected back to the sensor locations by the flaw surfaces. The peculiarity of the presented approach is the use of a time frequency coherence function for the identification of the arrivals of guided wave reflected back to the sensors by the damage surfaces.The damage detection methodology developed was divided into three steps. In the first step, the presence of the damage on the structure was assessed. In the second step, the arrival time of the reflected wave (or echo) was estimated using the continuous wavelet transform. Then, the detection algorithm was able, through a ray-tracing algorithm, to estimate the location of damage.A numerical investigation of two single damages was carried out. The damage was introduced on the railhead surface to simulate rolling contact fatigue defects. The results showed that the proposed methodology can be used successfully to localise the damage location, however, as expected, the localisation is strongly affected by the frequency range used. The results suggested that the separation and the characterisation of single modes are crucial for the identification of different types of rail defects. Further work is needed to establish the damage severity by relating the magnitude of the changes of the time frequency coherence to reflection and attenuation coefficients of each guided wave used and on the selection of the best range of frequency according to the type of damage to be identified.

Damage localization using transient non-linear elastic wave spectroscopy on composite structures

“…The TNEWS exploits changes in transient structural dynamic responses [13] due to the nonlinear behaviour introduced into the structure by the damage presence. The uncorrelations (discrepancies) between two structural dynamic responses generated by two different pulse excitation amplitudes are highlighted by a time-frequency coherence function [22]. As result, the arrival (at the sensor locations) of nonlinear elastic waves (generated by the Gaussian pulse wave impinging in the damage) will be observed in the time-frequency space with behaviours resembling those typical of structural change scattering mechanisms (Figure 7), though, the largest uncorrelations will be found around the harmonics of the excitation Gaussian pulse central frequency.…”

“…One of main drawbacks of the standard ultrasonic techniques, developed in either the time or the frequency domain [22][23], is that their performances decrease consistently in presence of echo overlaps, attenuation phenomena at high frequencies and critical sampling. These limitations can be overcome using Time Frequency Representations (TFRs) [23], which decrease the attenuation phenomena, and allows a careful control between overlapped echoes resulting in an increased accuracy of the measures.…”

“…The methodology analyse the changes in transient structural dynamic responses [13] due to the nonlinear material behaviour due to the damage presence. In particular, the method analyse the discrepancies in the times signal between two structural dynamic responses generated by two different pulse excitation amplitudes by using a time-frequency coherence function [22].…”

Feasibility in assessing the dipped rail joint defects through dynamic response of heavy haul locomotive

“…Rail damage detection exploiting ultrasonic wave propagation phenomena (P, S, Rayleigh and guided-wave velocities) identifies the presence of damage to the rail structure by discrepancies in the expected wave transmission paths [12]. The approach presented used a time-frequency coherence function for the identification of the returning guided waves reflected back to the sensors by the damage surfaces.…”

Damage identification in beams by a response surface based technique

“…Other inspection methods based on ultrasonic wave propagation have been proposed [3]. To detect internal flaws, very short ultrasonic pulse-waves with main frequencies ranging from 0.1-50 MHz are launched into the material.…”