Influential microstructural changes on rolling contact fatigue crack initiation in pearlitic rail steels

Eden, H. C.; Garnham, J.E.; Davis, Claire

doi:10.1179/174328405x43207

Cited by 69 publications

(44 citation statements)

References 13 publications

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“…The depth of the notches varied between 2 and 15 mm, while for more realistic representation of RCF cracking certain notches were angled with respect to the surface normal and the rail edge and the railhead surface. RCF head checks detected in rails are often inclined to the surface, penetrating initially at a shallow angle of approximately 15-301 until they reach a characteristic depth and turn down into the railhead at an angle of approximately 601 [24,25]. Fig.…”

Section: Experimental Details For the Spinning Rail Rig Testsmentioning

confidence: 99%

High-speed inspection of rails using ACFM techniques

Papaelias

Lugg

Roberts

et al. 2009

NDT & E International

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Section: Experimental Details For the Spinning Rail Rig Testsmentioning

confidence: 99%

High-speed inspection of rails using ACFM techniques

Papaelias

Lugg

Roberts

et al. 2009

NDT & E International

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“…It has been established in earlier work [13,15,17,19,20] that in standard grade, pearlitic rail steels subject to cyclic wheel-rail contact, where some pro-eutectoid (PE) ferrite was present at PA grain boundaries, there was strain-partitioning between the PE ferrite and the fully pearlitic zones. Earlier ductility exhaustion took place in the PE ferrite than in the fully pearlitic zones and hence RCF crack initiation and propagation took place along the PE ferrite / pearlite boundaries [20,21].…”

Section: Crack Characteristics For Cracks Up To Pa Grain Sizementioning

confidence: 99%

Visualization and Modelling to Understand Rail Rolling Contact Fatigue Cracks in Three Dimensions

Garnham

Fletcher

Davis

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part F:

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The paper presents an extensive survey of experimental data on rolling contact fatigue (RCF) crack shape and propagation characteristics in rails removed from service, where such cracks are angled to the rail axis. The data includes re-analysis of previously published experimental data to extract crack shape information and new experimental work on crack shapes at different stages in the early RCF life. Periods from initiation (ratcheted 'flake cracks') have been considered through very early growth to the limit of one prior austenite (PA) grain and on to rail-head visual cracks. Techniques included multi-sectioning through single cracks and crack zones, on used rail and test discs, to build up real 3D data on crack shapes and propagation characteristics. This data has been compared with the UK rail system guidance charts relating to visual crack length and respective vertical depth; all data fell within the indicated guidance zones. The configuration of such angled cracks, typically found in curves, so aligned due to the vector of both lateral and longitudinal traction, rather than just axially, was identified as an important case for modelling. A fracture mechanics based model has been developed to predict mode I and II stress intensity factors for such cracks covering multiple PA grains. An important geometry effect is revealed by which a contact approaching a crack angled to the rail axis is effectively 'offset' from the approach direction considered in 2D models, thereby resulting in lower predicted peak stress intensity factor values, compared with 2D, for the prediction of crack growth rates.

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“…The two-lobe form on the surface of a rail suggests a planar crack network below the surface, causing internal wear within the crack, which in turn causes the rail surface to sink and get a darker appearance due to less surface wear. Metallographic cross-sectioning shows an initial crack growing at small angles, around 10°to 30°, from the surface of the rail, then deviating to propagate nearly parallel to the surface within a shallow depth [10]. In more serious cases, the growth can deviate into a downwards angle leading to risk of rail break [9].…”

Section: Squat Initiation and Growthmentioning

confidence: 99%

3D characterization of rolling contact fatigue crack networks

Jessop

Ahlström

Hammar

et al. 2016

Wear

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a b s t r a c tRolling contact fatigue (RCF) damage is becoming more frequent with increased traffic, accelerations, and loading conditions in the railway industry. Defects which are characterized by a two-lobe darkened surface and a V-shaped surface-breaking crack are defined as squats. The origination and propagation of squats in railway rails is the topic of many recent studies; the associated crack networks develop with complicated geometry near the surface of rails, but can be difficult to detect and distinguish from normally existing head checks in their early stages, using in-field non-destructive detection techniques. After cutting out damaged sections of rail, there are a number of options to characterize the damage. The aim of this study was to evaluate different methods to geometrically describe squat crack networks; through X-ray radiography complemented with geometrical reconstruction, metallography, X-ray tomography, and topography measurements. The experiments were performed on squats from rail sections taken from the field. In the first method, high-resolution and high-energy X-ray images exposed through the entire rail head from a range of angles were combined using a semi-automated image analysis method for geometrical reconstruction, and a 3D representation of the complex crack network was achieved. This was compared with measurements on cross-sections after repeated metallographic sectioning to determine the accuracy of prediction of the geometrical reconstruction. A second squat was investigated by X-ray tomography after extraction of a section of the rail head. A third squat was opened by careful cutting, which gave full access to the crack faces, and the topography was measured by stylus profilometry. The high-energy X-ray, 3D reconstruction method showed accurate main crack geometry at medium depths; the advantage of the method being that it potentially could be developed for nondestructive testing in field. However significant drawbacks exist due to limitations in radiography in terms of detecting tightly closed cracks in very thick components. This includes the inability to detect the crack tips which is an important factor in determining the risks associated to a specific crack. Metallographic investigation of the cracks gave good interpretation of crack geometry along the sections examined, and gave the possibility to study microstructure and plastic deformation adjacent to the crack face. However this time-consuming method requires destruction of the specimen investigated. The X-ray tomography revealed the 3D crack network including side branches in a 10 Â 10 Â 30 mm 3 sample, and provided topographic information without completely opening the squat. Topography measurements acquired by stylus profilometry provided an accurate description of the entire main crack surface texture, including features such as surface ridges and beach marks.

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Influential microstructural changes on rolling contact fatigue crack initiation in pearlitic rail steels

Cited by 69 publications

References 13 publications

High-speed inspection of rails using ACFM techniques

High-speed inspection of rails using ACFM techniques

Visualization and Modelling to Understand Rail Rolling Contact Fatigue Cracks in Three Dimensions

3D characterization of rolling contact fatigue crack networks

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