Assessment of degradation of railroad rails: finite element analysis of insulated joints and unsupported sleepers

El–sayed, H.M.; Lotfy, Mohamed; Youssef, Haytham; Sobhy, Hany

doi:10.2140/jomms.2019.14.429

Cited by 8 publications

(3 citation statements)

References 25 publications

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“…The track parameters are as follows: rail meter mass 60 kg/m, rail bending stiffness 6. Figure 5 The mechanical model of track and vehicle interaction in the void zone [44] The present study, different to the previous studies [13,44], is directed to the research of the sleeper-ballast interaction. The model parameters are fitted to the experimental measurement (Fig.…”

Section: Numerical Simulation Of the Dynamic Impactmentioning

confidence: 99%

“…The study could identify the location of the excessive strain due to an influence of unsupported sleepers on girder of the bridge. The research [13] investigates the response of rails due to unsupported sleepers and insulated rail joints using an elastic-plastic FEM framework. The findings showed the high sensitivity of plastic flow and rail material fatigue to the value of rail deflection.…”

Section: Review Of the Literaturementioning

confidence: 99%

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Mechanism of the Sleeper-Ballast Dynamic Impact in Void Zones

Sysyn¹,

Przybyłowicz²,

Nabochenko³

et al. 2021

Preprint

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Unsupported sleepers or void zones in ballasted tracks are one of the most recent and frequent track failures. The void failures have the property of intensive development that, without timely maintenance measures, can cause the appearance of cost-expensive local instabilities like subgrade damages. The reason of the intensive void development lies in the mechanics of the sleeper and ballast bed interaction. The particularity of the interaction is a dynamic impact that occur due to void closure. Additionally, void zones cause inhomogeneous ballast pressure distribution between the void zone and fully supported neighbour zones. The present paper is devoted studying the mechanism of the sleeper-ballast dynamic impact in the void zone. The results of experimental in-situ measurements of rail deflections showed the significant impact accelerations in the zone even for light-weight slow vehicles. A simple 3-beam numerical model of track and rolling stock interaction has shown the similar to the experimental measurements dynamic interaction. Moreover, the model shows that the sleeper accelerations are more than 3 times higher than the corresponding wheel accelerations and the impact point appear before the wheel enters the impact point. The analysis of ballast loadings shows the specific impact behaviour in combination with the quasistatic part that is different for void and neighbour zones, which are characterised with high ballast pre-stressed conditions. The analysis of void sizes influence demonstrate that the impact loadings, wheel and sleeper maximal accelerations appear at certain void depth after which the values decrease. The ballast quasistatic loading analysis indicates more than twice increase of the ballast loading in neighbour zones for long voids and almost full quasistatic unloading for short length voids. However, the used imitation model cannot explain the nature of the dynamic impact. The mechanism of the void impact is clearly explained by the analytic solution using a simple clamped beam. A simplified analytical expression of the void impact velocity shows that it is linearly related to the wheel speed and loading. The comparison to the numerically simulated impact velocities shows a good agreement and the existence of the void depth with the maximal impact. An estimation of the long-term influences for the cases of normal sleeper loading, high ballast pre-stress and quasistatic loading in the neighbour zones and high impact inside the void are performed.

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Section: Numerical Simulation Of the Dynamic Impactmentioning

confidence: 99%

Section: Review Of the Literaturementioning

confidence: 99%

Mechanism of the Sleeper-Ballast Dynamic Impact in Void Zones

Sysyn¹,

Przybyłowicz²,

Nabochenko³

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…When the friction between the wheel and the rail was high (e.g.,

), the cyclic plasticity at the crack tip increased significantly, and the cyclic plastic zone at the crack tip of a large angle crack (e.g.,

, where

is the angle between the rail crack and the train−wheel running direction) was significantly larger than that at the crack tip of a small angle crack (e.g.,

). Elsayed et al [ 9 ] used an elastic−plastic finite−element framework to investigate the response of rail material, and cracks initiated at the rail surface knowing that the simulated friction coefficient between wheel and rail is 0.35 and the applied wheel load is 110 kN. Additionally, 15 mm depth is enough to study the nonlinear characteristics of rail materials.…”

Section: Introductionmentioning

confidence: 99%

Influence of Stress Intensity Factor on Rail Fatigue Crack Propagation by Finite Element Method

et al. 2021

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Wheel rail rolling contact fatigue is a very common form of damage, which can lead to uneven rail treads, railhead nuclear damage, etc. Therefore, ANSYS software was used to establish a three-dimensional wheel–rail contact model and analyze the effects of several main characteristics, such as the rail crack length and crack propagation angle, on the fatigue crack intensity factor during crack propagation. The main findings were as follows: (1) With the rail crack length increasing, the position where the crack propagated by mode I moved from the inner edge of the wheel–rail contact spot to the outer edge. When the crack propagated to 0.3–0.5 mm, it propagated to the rail surface, causing the rail material to peel or fall off and other damage. (2) When the crack propagation angle was less than 30°, the cracks were mainly mode II cracks. When the angle was between 30 and 70°, the cracks were mode I–II cracks. When the angle was more than 70°, the cracks were mainly mode I cracks. When the crack propagation angle was 60°, the equivalent stress intensity factor reached the maximum, and the rail cracks propagated the fastest.

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