Abstract
Ultrasonic guided wave (UGW) has shown great potential in the field of structural health monitoring of rail tracks due to its long-range capability and full cross section coverage. However, the practical application of UGW has been hindered by the complicated signal interpretation because of the natures of multiple modes and dispersion. Therefore, it is desirable that the effective UGW modes with high excitability and least dispersion can be identified and extracted for practical applications. In this paper, a numerical study on the guided wave propagation was carried out on a standard rail with 56E1 profile. Firstly, Floquet-Bloch theory was applied to obtain the dispersion curves of guided wave in a rail. Then, a 3D FE model was built to investigate the UGW propagation along the rail within the frequency range of 0–120 kHz. Wavenumber-frequency analysis method was applied to decompose and identify the propagating UGW modes. With a carefully designed 2D bandpass filter, a specific mode W0 was extracted in the wavenumber-frequency domain. Finally, a frequency band sweep technique was also proposed to get the optimal frequency band to achieve a pure and least-dispersive UGW mode along the rail web. The proposed method provides an effective way to extract efficient UGW modes to assess the integrity of the rail track, as well as other waveguides with complex geometry.
Highlights
Ultrasonic guided wave (UGW) has continuously attracted researchers’ attention in the fields of nondestructive testing (NDT) and structural health monitoring (SHM) in railway engineering [1,2,3]
Zhou et al developed a 3D diagnostic imaging technique based on time-of-flight signal features [5]. e advantages of UGW include long-range capability, full coverage across the whole cross section of the rail track, and rapid inspection with few transducers
Due to the complex cross section of rail track compared to the plate or pipe, there are much more UGW modes propagating along the rail [6]
Summary
Ultrasonic guided wave (UGW) has continuously attracted researchers’ attention in the fields of nondestructive testing (NDT) and structural health monitoring (SHM) in railway engineering [1,2,3]. Sanderson and Smith proposed a three-dimension FE model based on eigenfrequency analysis to obtain the dispersion curves of rail [18] In these methods, the process should be repeated by changing the length of unit cell until all the modes are obtained. Inspired by the filtering method in plates, the broadband UGW signal in the rail excited by conventional ultrasonic transducer or laser pulse can be analysed in the wavenumber-frequency domain. We will focus on the study of extraction of efficient ultrasonic guided wave mode in rail track based on Floquet-Bloch theory.
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