Rail Head Wear Research Articles

Analysis of the impact of rail head wear on railway superstructure stability

Continuous welded rail track (CWR) is a superstructure construction of the railway that withstands significant compressive forces from the longitudinal extension of the rails due to temperature changes, ensuring the safe railway operation. The applicable for the Bulgarian railway system methodology for determining the critical compressive force at which the CWR loses stability has been examined. Different types of rails with their respective design parameters, important for the force calculation, have been taken into consideration. The considered design parameters, as moment of inertia and sectional modulus of the rails, change during operation due to the rail head wear. The aim of the article is to examine specific examples of railway tracks on curves, analyzing the impact of the changed operational design parameters of the rail on the stability of the track. The operational and geometric parameters of the railway track have been considered.

Effect of rail cant on stress distribution

The rail cant is an important geometry parameter and is commonly monitored to ensure railway safety and comfort conditions. Understanding the influence of cant variation on the performance of railway components is extremely important to define the tolerance limits of the track and adequacy of maintenance plans. There are numerous rail cant patterns on railways, 1:40, 1:30, 1:20. However, the optimal rail cant to reduce the stress and wear of rail head not been extensively studied. This work performs an analysis of the effect of the rail cant on the rail head stress distribution. To investigate stress and strain in rail head, a Finite Element Model with Ansys software was used. For the analysis was considered a 136RE rail, axle load of 32 ton and AAR-1B wheel profile. The rail cant was varied in 0, 1:20 and 1:40. The results show that the stress in rail and wheel increases with the rail cant. The maximum stress occurred in the condition with rail cant of 1:20. The variation of cant from 0 to 1:20 results in a decrease of approximately 9% in maximum stress, ranging from 947 MPa to 867 MPa. The wheel/rail contact in cant zero condition occurred close to the transition of the wheel tread and the beginning of flange root, resulting in a dynamic instability in the wheelset. In addition to higher contact stress, increases the propensity for the hutting phenomenon, which can accelerate rail and wheel wear

Прогнозування зносу головок залізничних рейок в процесі експлуатації

Прогнозування зносу головок залізничних рейок в процесі експлуатації

Mathematical model of the formation and development of wave-shaped rail wear when an electric locomotive operates in the traction mode in tangent sections of the track

The problem of wave-shaped rail wear is highly relevant for rail transport. The paper presents a mathematical model of the formation and development of wave-shaped rail wear. The task of estimating vertical wear of the rail head under the axles of electric locomotives passing in the traction mode is considered. A technique has been developed that allows building chain of calculations that determine the formation and development of a wave-shaped rail head wear. A specific calculation example is given, illustrating the process of propagation of a wave-shaped wear from the source of its formation in the direction of train motion. An example of the calculation allows drawing the following conclusions:1. Wave-shaped wear primarily occurs when the shock interaction of the wheel of an electric locomotive moving in the traction mode and a rail thread having imperfections of the rolling surface. Such imperfections, among others, may be a joint with a significant gap or a “step down” in the direction of the locomotive, as well as a welded joint with defect 46.3-4.2. Wavelength of the wave-shaped rail wear, its configuration and amplitude of the fundamental tone are determined mainly by joint oscillations of the wheel-motor unit of the locomotive and the track infrastructure in the field of high-frequency oscillations (120 – 180 Hz).3. Multivariate calculations showed that in steady state, the distribution speed of wave-shaped rail wear in the direction of train motion (as a function of the number of axles of electric locomotives passed in traction mode) is directly proportional to the vertical load at the wheel and rail contact in the slip zone 0≤Q≤F/(2nψk), is inversely proportional to wear resistance C and significantly depends on the parameters of the undercarriage of the electric train and the track superstructure.

Effect of head wear and lateral forces on underhead radius crack propagation

This paper investigated the effect of rail head wear (HW) and lateral forces on underhead radius stress conditions and resulting stress intensity factors (SIFs) of a long transverse crack. The occurrence of tension spikes at the underhead radius of the rail as a result of localised vertical and lateral bending of the head-on-web was significantly exacerbated with increasing rail HW. The extended finite element method (X-FEM) modelling, which had previously been validated by comparison with in-track measurements to verify the prediction of tension spikes, was used to model a single rail on discrete elastic foundations. SIFs along the crack front were parametrically evaluated in terms of changes in the contact patch offset (CPO), the ( L/ V) ratio of lateral ( L) to vertical ( V) loads, the rail HW, and crack size and shape. The X-FEM results revealed that for a long transverse crack, extending the crack length to the underhead radius position results in higher SIFs across the underhead radius as a result of tensile bending stresses. These higher SIFs can contribute to a massively higher crack growth rate at this location, as was evidenced by the crack growth morphology at the underhead radius.

Fatigue Analysis of the Rail Underhead Radius under High Axle Load Conditions

An evaluation of the potential risk of fatigue damage at the rail underhead radius (UHR) due to the occurrence of a short duration tensile stress peak, as a wheel passes over, has been examined. The tensile stress peak is mainly due to the localised bending of the rail head-on-web and its magnitude is associated with the contact position, lateral and vertical forces and rail head wear (HW). The stresses at the underhead radius have been explored using the finite element method (FEM). The Dang Van (DV) criterion, implemented as a customised computer programme, was used to identify the fatigue damage at the UHR. Fatigue behaviour under heavy haul conditions was compared for heat-treated low alloy, euctectoid and hypereutectoid rail grades in order to predict allowable rail head wear limits.

Development of autonomous ACFM rail inspection techniques

Rail tracks are subjected to high contact stresses leading to wear and fatigue. With increased axle weight and faster trains, there is a need for routine inspection of the rails. In order to improve punctuality and reliability of track rail inspection, intelligent systems and robotics can be employed. In this research, supported through the FP7 INTERAIL project, a robotic system is being developed for the detection and characterisation of rolling contact fatigue (RCF) defects on in-service track rails using alternating current field measurement (ACFM) techniques. The autonomous inspection system consists of a mechanised trolley, an FS02N Kawasaki robot arm and a commercially available AMIGO ACFM system, supplied by TSC Inspection Systems. The ACFM probe is used to both detect (as the trolley moves at a controlled speed with the sensor in a fixed position) and characterise (whilst the trolley is stationary using the robot arm to survey the rail head) RCF cracks. Results show that the ACFM sensor can detect RCF defects even at significant (approx 4 mm) lift-off; however, if lift-off exceeds 4 mm (for example due to rail-head wear), the data acquired may not be easily exploited to characterise the defects. This paper presents the results obtained based on the work carried out to date.

Simulation of wear on a rough rail using a time-domain wheel–track interaction model

This paper presents results from simulations of railhead wear due to initial sinusoidal and broad-band roughness using a time-domain wheel–track vertical interaction model integrated with a three-dimensional wheel–rail contact model. As typical roughness wavelengths are short and frequencies are high compared with vehicle body motions, the vehicle is simplified to an unsprung wheel mass. The rail is modelled as a Timoshenko beam discretely supported by pads, sleepers and ballast. The wheel–rail contact in the interaction model is modelled with a non-linear Hertzian contact spring. The obtained wheel–rail forces are then incorporated into the three-dimensional contact model to calculate wear over the railhead. The wheel–rail contact is modelled as non-Hertzian and non-steady based on the Variational Method [G. Xie, S.D. Iwnicki, Calculation of wear on a corrugated rail using a three-dimensional contact model, in: Proceedings of the Seventh International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Brisbane, Australia, Materials Australia, 2006] and the wear is assumed to be proportional to the friction work. Cases of both a free and a driven wheel with a constant torque are considered. The phase angles between dynamic wheel–rail force and roughness are examined and wear is found to be almost in-phase with roughness and therefore, no roughness growth is predicted by the model as presented in its current form. Although clearly in contradiction to reality where roughness grows under certain conditions this work leads to interesting question about why roughness growth is predicted by a simple contact model but not when complexity is increased to include non-Hertzian and non-steady contact conditions.

Calculation of wear on a corrugated rail using a three-dimensional contact model

This paper presents the results from simulations of railhead wear using a three-dimensional contact model. The wheel/rail contact is modelled as non-Hertzian and non-steady based on the Variational Method [J.J. Kalker, Three-Dimensional Elastic Bodies in Rolling Contact, Kluwer Academic Publishers, 1990] and the wear is assumed to be proportional to the frictional work. A wheel rolling over initial sinusoidal roughnesses is considered and when constant values of normal force and creepage are used, it is found that the maximum wear occurs at positions close to the crest of the initial wavelength and therefore roughness is not predicted to grow. A range of prescribed dynamic normal forces were then used to investigate the relationship between wear and dynamic force but again, no corrugation growth mechanism was revealed. Wear calculations using both Hertzian and non-Hertzian contact are compared and the significance of the non-Hertzian effects on the wear calculation is shown.

Contact-impact stress analysis of rail joint region using the dynamic finite element method

The finite element code ANSYS/LS-DYNA is used to simulate the wheel/rail contact-impact behavior at rail joint region. The implicit and explicit finite element methods have been couple to analyze wheel/rail impact process. In the FE simulation, a material model with linear kinematic hardening was used. The influences of axle load and train speed on contact forces, the stresses and strains in the railhead are investigated in detail. From obtained results, it is found that the axle load has more great effect on the above parameters during impacting at the constant speed. However, the effect of train speed is relatively weak. The study provides a method and useful datum for the further research on fatigue and wear of railhead and improving the rail joint mode.

Wheel flange/rail head wear simulation

The difficulties and expenses involved in field experiments on wheel-rail system wear forced researchers to use, whenever possible, laboratory tests. The major problem in laboratory tests is how to transfer the results obtained to the real wheel-rail system. Modeling of the wear process between wheel flange and side face of a rail head is studied and discussed. It is noted that the laboratory tests with rolling-lateral sliding better simulates wheel flange and rail head wear. Four wear modes, referred to as mild, severe, heavy and catastrophic, have been identified in the laboratory tests. The heavy wear mode has not been identified before. The catastrophie wear mode has been observed at the lateral creepage of 5%. The wear modes that occur in worn wheel flanges and in side-worn rails have been found to correlate with those found on the rollers during laboratory tests. The boundaries of wear modes in terms of product of maximum contact pressure and creep value were defined. The hypothesis of wear mechanisms responsible for wear processes was suggested.

Rail head corrugation growth predictions based on non-linear high frequency vehicle/track interaction

The aim of this paper is to calculate the rail head wear caused by a wheelset rolling over short-wavelength longitudinal irregularities on the rail. Two different computer models for the dynamic vehicle/track interaction are compared. The simplified theories for the wheel/rail contact mechanics used in those programs are verified against the exact theory for the case of a driven locomotive wheel on tangent track. Shift of contact point and the distribution of wear within the contact area are found to be important. The non-linear development of the rail head profile caused by millions of wheelset passages is also presented.