Numerical and Experimental Research on Identifying a Delamination in Ballastless Slab Track

Fan, Guopeng; Zhang, Hai Yan; Zhu, Wen-Fa; Zhang, Hui; Chai, Xiao

doi:10.3390/ma12111788

Cited by 12 publications

(7 citation statements)

References 42 publications

(44 reference statements)

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“…The noise, caused by material backscattered energy correlated over time, is always considered the limiting factor in most ultrasonic defect detection scenarios [19]. It resists detailed analysis and should be eliminated to yield quality results.…”

Section: The Theory Of Diffuse Fieldsmentioning

confidence: 99%

Phase Coherence Imaging for Near-Surface Defects in Rails Using Cross-Correlation of Ultrasonic Diffuse Fields

Zhang

Shao

Fan

et al. 2019

Metals

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In this paper, phase coherence imaging is proposed to improve spatial resolution and signal-to-noise ratio (SNR) of near-surface defects in rails using cross-correlation of ultrasonic diffuse fields. The direct signals acquired by the phased array are often obscured by nonlinear effects. Thus, the output image processed by conventional post-processing algorithms, like total focus method (TFM), has a blind zone close to the array. To overcome this problem, the diffuse fields, which contain spatial phase correlations, are applied to recover Green's function. In addition, with the purpose of improving image quality, the Green's function is further weighted by a special coherent factor, sign coherence factor (SCF), for grating and side lobes suppression. Experiments are conducted on two rails and data acquisition is completed by a commercial 32-element phased array. The quantitative performance comparison of TFM and SCF images is implemented in terms of the array performance indicator (API) and SNR. The results show that the API of SCF is significantly lower than that of TFM. As for SNR, SCF achieved a better SNR than that of TFM. The study in this paper provides an experimental reference for detecting near-surface defects in the rails.calculating the cross-correlation of noise recorded at two locations on the surface. In 2001, Weaver et al. [4] validated that the impulse response of the structure between two receiving points can be extracted by using the cross-correlation of noise recorded at two receiving points in random noise fields. The retrieved signals were only different in magnitude from Green's function. From then on, due to the ability of retrieving deterministic signals (Green's function) from random signals, this method has been applied in many fields, such as electromagnetics [5], seismology [6,7], ocean acoustics [8], civil engineering [9], medicine [10], and ultrasonics [11]. In 2004, under the isotropic scattering assumption, Snieder et al. [12] deduced the feasibility of recovering Green's function of the ballistic wave from the coda. The global requirement of the equipartitioning of normal modes was held if the scattered waves propagated quasi-isotropically near the receivers. Subsequently, after considering the limitation of time-reversal invariance in correlating noise, he found that it was possible to obtain Green's function of diffusion by correlating the solutions of the diffusion equation that were excited randomly [13]. This property was used to retrieve Green's function for diffusive systems from ambient fluctuations. In 2011, Moulin et al. [14] tested ambient vibrations for passive real-time monitoring of structures by low-frequency random vibration data, which was collected on an all-aluminum naval vessel operating at high speed. In 2014, Roux et al. [15] evaluated the relative contributions of source distribution and medium complexity in the two-point cross-correlations, showing that the fit between the cross-correlation and the 2D Green's function strongly depended on the nature of th...

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Section: The Theory Of Diffuse Fieldsmentioning

confidence: 99%

Phase Coherence Imaging for Near-Surface Defects in Rails Using Cross-Correlation of Ultrasonic Diffuse Fields

Zhang

Shao

Fan

et al. 2019

Metals

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“…A straightforward method of damage detection for slab track is regular visual inspection or non-destructive testing (NDT) methods [20][21][22][23][24][25][26][27][28]. The NDT techniques are powerful in damage detection for concrete structures, especially in structural health monitoring of bridges [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

“…The NDT techniques are powerful in damage detection for concrete structures, especially in structural health monitoring of bridges [29][30][31]. The NDT techniques adopted in ballastless railway detection mainly includes impact-echo method [21,23,24], ground-penetrating radar (GPR) [21], digital image correlation (DIC) [25,26] and synthetic aperture focusing technique (SAFT) ultrasound imaging method [27,28]. They can detect specific slab defects and report the size and even geometry of defects through customized devices.…”

Section: Introductionmentioning

confidence: 99%

Identification of Temperature-Induced Deformation for HSR Slab Track Using Track Geometry Measurement Data

Liu

2019

Sensors

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Slab track is widely used in many newly built high-speed rail (HSR) lines as it offers many advantages over ballasted tracks. However, in actual operation, slab tracks are subjected to operational and environmental factors, and structural damages are frequently reported. One of the most critical problems is temperature-induced slab-warping deformation (SWD) which can jeopardize the safety of train operation. This paper proposes an automatic slab deformation detection method in light of the track geometry measurement data, which are collected by high-speed track geometry car (HSTGC). The characteristic of track vertical irregularity is first analyzed in both time and frequency domain, and the feature of slab-warping phenomenon is observed. To quantify the severity of SWD, a slab-warping index (SWI) is established based on warping-sensitive feature extraction using discrete wavelet transform (DWT). The performance of the proposed algorithm is verified against visual inspection recorded on four sections of China HSR line, which are constructed with the China Railway Track System II (CRTSII) slab track. The results show that among the 24,806 slabs being assessed, over 94% of the slabs with warping deformation can be successfully identified by the proposed detection method. This study is expected to provide guidance for efficiently detecting and locating slab track defects, taking advantage of the massive track inspection data.

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“…The ballastless track structure is the main track structure of China’s high-speed rail lines, accounting for more than 50% of the operating lines [2]. The high-speed rail ballastless track structure is a typical multilayer structure in which the track slab (concrete material) and bedplate (concrete material) are bonded together by cement, asphalt, and mortar [3]. The high-speed rail ballastless track structure is an important bearing component.…”

Section: Introductionmentioning

confidence: 99%

A SAFT Method for the Detection of Void Defect inside a Ballastless Track Structure Using Ultrasonic Array Sensors

Zhu

Chen

et al. 2019

Sensors

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High-precision ultrasound imaging of void defects is critical for the performance and safety assessment of ballastless track structures. The sound propagation velocity of each layer in the ballastless track structure is quite different. However, the traditional concrete Synthetic Aperture Focusing Technique (SAFT) ultrasound imaging method is based on the assumption that the concrete has a single constant shear wave velocity. Thus, it is not a suitable method for the ultrasonic imaging of multilayer structures. In this paper, a Multilayer SAFT high-precision ultrasound imaging method is proposed. It is based on the ray-tracing technique and uses the Fermat principle to find the refraction point that minimizes the delay of the acoustic wave propagation path at the interface of the discrete layers. Then, the acoustic wave propagation path is segmented by the position of the refraction point, and the propagation delay of the ultrasonic wave is obtained segment by segment. Thus, the propagation delay of the ultrasonic wave is obtained one by one, so that the propagation delay of the ultrasonic wave in the multilayer structure can be accurately obtained. Finally, the focused image is obtained according to the SAFT imaging algorithm. The finite element simulation and experimental results show that the Multilayer SAFT imaging method can accurately track the propagation path of the ultrasonic wave in ballastless track structures, as well as accurately calculate the propagation delay of the ultrasonic wave and the lengths of void defects. The high accuracy of the Multilayer SAFT imaging represents a significant improvement compared to traditional SAFT imaging.

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Numerical and Experimental Research on Identifying a Delamination in Ballastless Slab Track

Cited by 12 publications

References 42 publications

Phase Coherence Imaging for Near-Surface Defects in Rails Using Cross-Correlation of Ultrasonic Diffuse Fields

Phase Coherence Imaging for Near-Surface Defects in Rails Using Cross-Correlation of Ultrasonic Diffuse Fields

Identification of Temperature-Induced Deformation for HSR Slab Track Using Track Geometry Measurement Data

A SAFT Method for the Detection of Void Defect inside a Ballastless Track Structure Using Ultrasonic Array Sensors

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