Early stages of rail squat formation and the role of a white etching layer

Pal, Sarvesh; Daniel, William J.T.; Farjoo, Mohammadali

doi:10.1016/j.ijfatigue.2013.02.016

Cited by 56 publications

(13 citation statements)

References 31 publications

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“…According to the literature, the size of roughly about 0.2 mm dent which is a fine depression at the rail surface is considered as an early stage of crack initiation and propagation. 8 In this regard, the kurtosis value of 3.8 attributed to the dent with the same size which can reflect the early stage of faults on the wheel surface is considered as the baseline to determine the existence of the fault in the sound map. Similarly, Figure 8(c) and (e) shows a vague beamforming map; therefore, the location of the wheel with fault cannot be identified.…”

Section: Results Of Fault Detection and Localisationmentioning

confidence: 99%

“…3 In the wheel/rail system, faults or imperfections can be categorised into wheel-flat due to severe wearing, dent due to crack and squat due to rolling contact fatigue. 4–8 It is critical to identify and localise the position of the fault on the wheel so that repair and maintenance can be performed on time. However, it remains technically challenging to localise the wheel fault in real time.…”

Section: Introductionmentioning

confidence: 99%

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Fault detection of wheel in wheel/rail system using kurtosis beamforming method

Chen

Choy

Wang

et al. 2019

Structural Health Monitoring

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Fault detection systems are typically applied in the railway industry to examine the structural health status of the wheel/rail system. We herein propose a time-domain kurtosis beamforming technique using an array of microphones for the fault identification and localisation of the wheel/rail system under an environment with high background noise. As an acoustics-based noncontact diagnosis method, this technique overcomes the challenge of the contact between the sensors and examined structures, and it is more applicable for impulsive signals of broadband nature, such as impact noise generated from faults on the wheel surface. Moreover, the application of kurtosis enables the identification and localisation at low signal-to-noise ratio. Under such circumstance, the impulsive signals generated by faults were totally merged in rolling noise and background noise. Meanwhile, different types of faults on the wheels could be identified and localised by observing the kurtosis value on the beamforming sound map. The effectiveness of the proposed method to diagnose the type of wheel fault with low signal-to-noise ratio and moving source has been validated experimentally. This method may provide a useful tool for the routine maintenance of trains.

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Section: Results Of Fault Detection and Localisationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fault detection of wheel in wheel/rail system using kurtosis beamforming method

Chen

Choy

Wang

et al. 2019

Structural Health Monitoring

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“…Fatigue failure formed on the friction surface is related to the microstructure of the material. White etching layers on the wheel-rail friction surface exert immense influences on the initiation and propagation of fatigue cracks and the subsequent spalling at the wheel-rail contact interface [11] [12] [13] [14]. The research results of Chen [14] and others reveal that the white etching layers formed through local laser quenching will accelerate the formation of fatigue cracks.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Relation between Rolling Contact Fatigue Property and Microstructure on the Surface Layer of D2 Wheel Steel

Wang¹,

Zhao²,

Liu³

et al. 2019

MSA

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Through the rolling contact fatigue experiment under the condition of the lubricating oil, this article investigated the relation between contact fatigue property and microstructure on the surface layer of D2 wheel steel. The results showed that although the roughness of the original specimen induced by mechanical processing would diminish to some extent in the experiment, the 0.5-1.5 μm thick layer of ultrafine microstructure on the original mechanically-processed specimen surface would still become micro-cracks and small spalling pits due to spalling, and would further evolve into fatigue crack source. Additionally, even under the impact of the load that was not adequate to make the material reach fatigue limit, the ferrite in the microstructure underwent plastic deformation, which led the refinement of proeutectoid ferrite grains. During the experiment, the hardening and the refinement caused by plastic deformation consisted with the theory that dislocation gave rise to plastic deformation and grain refinement. The distribution laws of hardness and ferrite grain sizes measured could be explained by the distribution law of the shearing stress in the subsurface.

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“…The development of these cracks coincides with the formation of black spots in the rail running surface. Pal et al [5,6] also performed some metallurgical observations and pointed out that the crack initiation in the rail surface was related to microstructural changes and the consequential white etching layer (WEL) and ratcheting. Grassie et al [7] argued that the WEL is not a necessary condition for squat initiation, and squat-like defects associated with the WEL could be classified as studs.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the formation of corrugation-induced rail squats based on extensive field monitoring

Deng

Qian

et al. 2018

International Journal of Fatigue

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Rail squats originate from a number of sources, such as corrugations, indentations and welds. A five-year continual field monitoring study was performed on squats induced by corrugations. This study indicated that a small black depression formed at the corrugation under wheel-rail dynamic forces, and then, a primary crack typically initiated on the gauge side edge of the depression. Subsequently, the crack began to propagate in the rail surface in a U shape toward the gauge side in both the traffic direction and the opposite-traffic direction and into the rail toward the field side at an angle of approximately 20°. Rail inclination could influence the crack initiation location and propagation path. The geometry of the black squat depression was initially elliptical, and then, its edge followed the U-shaped cracking path as it grew. The squats turned into a kidney-like shape, typically with a U-shaped crack. Tensile stress likely led to the squat crack initiation and propagation. This cracking phenomenon and mechanism are analogous to the ring/cone crack formation of brittle materials under sphere-sliding contact. As the squats grew further, a ridge formed in the middle part of the depression, and an I-shaped crack appeared at this ridge due to the impact of the wheels. This process eventually led to two-lung-shaped mature squats, typically with a Y-shaped crack. The findings of this paper provide insight into the formation of rail squats.

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Early stages of rail squat formation and the role of a white etching layer

Cited by 56 publications

References 31 publications

Fault detection of wheel in wheel/rail system using kurtosis beamforming method

Fault detection of wheel in wheel/rail system using kurtosis beamforming method

Investigation of the Relation between Rolling Contact Fatigue Property and Microstructure on the Surface Layer of D2 Wheel Steel

Investigation of the formation of corrugation-induced rail squats based on extensive field monitoring

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