Rail Gage Face Research Articles

Development of an optical sensing system for the detection of lubricity conditions on the rail gage face

ABSTRACT A novel optical sensing device that uses laser-induced fluorescence to detect the lubricity condition of the rail gage-face is evaluated. By analysing the fluorescence properties of eight commonly used gage-face greases used by the U.S. Class I railroads, we observed that the emitted fluorescence of the grease when exposed to ultraviolet (UV) light of different wavelengths can be used for detecting their presence. This observation is used to develop a non-contacting optical sensing device that uses two 405 nm lasers, a fluorescence detector, and a fluorescent bandpass filter, which are optimized for the fluorescence spectra of the greases. Two sensing devices are installed on a robotic rail cart, one on each side, to simultaneously detect the lubricity conditions on the rails over extended distances. After extensive evaluations using both laboratory and field testing, it is confirmed that the optical sensing system can accurately detect the presence of the gage-face grease through the fluorescence intensity or intensity variance, even when there are small quantities of grease in relatively thin layers. Furthermore, the test results indicate a high level of repeatability and efficiency in detecting the spatial distribution of grease along the rail.

Analysis of the causes of severe side wear of the high rail on metro curves by numerical simulation and field investigation

Two of the Shanghai metro lines suffered from severe side wear on the high rail, not only in sharp curves but also in large curves, and the service life of some rails on sharp curves was reduced by approximately 50% compared with the last rail replacement. Features and evolution rules for the rail side wear and the wheel flange wear were determined by field measurements and long-term monitoring. A rail wear prediction model, verified in our previous work, is used to reveal the influence of factors on rail wear. The results indicate that the poor lubrication condition at the rail gauge face is the main cause of severe side wear of the high rail, and the use of wheel profiles with low conicity and the loss of profile curvature of low rail profiles caused by the untimely maintenance also increase the side wear of the high rail. The service life of the high rail could be greatly extended by some countermeasures, such as repairing the worn shape of the low rail and repairing/improving the wayside lubrication system.

Understanding and treatment of severe flange wear of metro train wheels

Urban rail transit usually contains many small radius curved tracks, and wheel flange wear is prominent, which greatly reduces the service life and increases the maintenance and replacement costs of wheelsets. Two metro lines in Shanghai of China had suffered from severe flange wear since 2017, and the flange wear rate increased gradually over the next three years. This paper presents the understanding and treatment of severe flange wear through field measurement and numerical simulation. The investigation results indicated that the key factors causing severe flange wear were poor rail gauge face lubrication, the use of a low conicity wheel profile for trains running on the two metro lines containing many small radius curved tracks, and the lack of timely maintenance of low rail profiles. Three countermeasures were proposed to mitigate wheel flange wear, which were evaluated through wheel–rail matching analysis and wheel wear prediction. Then, two countermeasures, i.e. improving rail gauge face lubrication and employing the LM-30 wheel profile, were verified through field tests.

Railway track irregularity and curvature estimation using doppler LIDAR fiber optics

The application of Doppler-based LIght Detection and Ranging (LIDAR) technology for determining track curvature and lateral irregularities, including alignment and gage variation, are investigated. The proposed method uses track measurements by two low-elevation, slightly tilted LIDAR sensors nominally pointed at the rail gage face on each track. The Doppler LIDAR lenses are installed with a slight forward angle to measure track speed in both longitudinal and lateral directions. The lateral speed measurements are processed for assessing the track gage and alignment variations, using a method that is based on the frequency bandwidth dissimilarities between the vehicle speed and track geometry irregularity. Using the results from an extensive series of tests with a body-mounted Doppler LIDAR system on-board a track geometry measurement railcar, the study indicates a close match between the LIDAR measurements and those made with existing sensors on-board the railcar. The field testing conducted during this study indicates that LIDAR sensors could provide a reliable, non-contact track monitoring instrument for field use in various weather and track conditions, potentially in a semi-autonomous or autonomous manner.

On the mechanism of squat formation on train rails – Part I: Origination

A phenomenological investigation of squat defects on rail grade R260Mn is performed. The surface-breaking crack pattern, which is either linear or branched (V-shaped), shows a typical position and orientation in the running band. Particular characteristics are asymmetry of this pattern, with the presence of a leading and a trailing branch, and crack reflection or deviation at the running band border. Bending tests reveal a 3D internal crack pattern, with a pair of crack planes or ‘wings’ enclosing a wedge at the surface. Microstructural analysis of the rail upper layer shows metallurgical principles of crack initiation: delamination and transverse fracture of white etching material at the surface. This analysis moreover reveals a 3D anisotropic texture of the upper layer under combined bi-directional tangential surface stresses. Mechanical interpretation of the crack morphology shows that the leading or single branch of the surface-breaking crack pattern is a shear-induced fatigue crack, following the anisotropic microstructure when growing into the rail. The trailing crack of a branched squat is explained as the result of a subsequent transverse, wedge-shaped brittle failure mechanism of the surface layer of the rail, developing within the actual elliptical Hertzian contact patch – or the envelope of potential contact ellipses at the leading crack position. It is driven by the transverse shear loading towards the rail gauge face.

Rail lubrication and its impact on the wheel/rail system

As the effectiveness of Transnet Freight Rail's current hi-rail lubrication strategy cannot be adequately quantified, an investigation into the level of surface protection between application cycles was initiated. Influencing factors such as the tracking performance of rolling stock, the number and type of locomotives and wagons in a train, axle load, train speed, and the coefficient of friction on the gauge face have, thus, been considered. After a brief literature review of international experiences with respect to friction management, a detailed description is given of the tests that were conducted by Transnet Freight Rail. Conclusions from these tests indicate that the increase in rail gauge face temperature on the high rail is dominated by the duration and the magnitude of the flange forces.

Effect of moderating friction of wheel/rail interface on vehicle/track dynamic behaviour

Lubrication in sharp curves has been commonly adopted so far to decrease the friction between wheel flange and rail gauge face following wear reduction and energy consumption. Also, lubrication is focused on its effect on decreasing the possibility of wheel flange climb derailment and squealing which is a kind of rolling noise. In addition, the lubrication between wheel tread and the top of low rail is studied to prevent low-rail corrugations in sharp curves. The lubricant supplied between the top of rail and wheel tread called “friction modifier” because of its traction characteristics, the relation between traction coefficient and slip ratio, modified to be suitable for refraining negative damping or sliding between wheel and rail has recently been developed. In this study, track site measurements were carried out to identify the effects of lubrication between wheel tread and the top of low rail, and between wheel flange and the gauge face of high rail on vehicle/track interaction excited by vehicle running in sharp curves such as lateral force and the angle of attack caused by a leading axle of a bogie. Also, based on the results measured at a track site, the adequacy of vehicle dynamic simulation model was verified. Then the measured results were investigated from the aspects of interacting forces between wheel and rail obtained by vehicle dynamic simulations, and the effect of lubrication on vehicle/track dynamic behaviour was evaluated with the focus placed on the coefficient of kinetic friction and the steering performance of bogie such as lateral force and the angle of attack. This paper describes the detailed arrangements and the results of track site measurements in a sharp curve whose radius was 160 m and vehicle dynamic simulation. As a result, the significant effect of the top of low-rail lubrication on improving vehicle/track dynamic behaviour was identified. Finally the advantage of a kind of friction modifier, called as “friction moderator” in this study, and its jetting device by which the friction moderator was supplied to wheel/rail interface the authors have been developing for the top of low-rail lubrication was discussed.

Development of Wheel/Rail Friction Moderating System (FRIMOS)

Lubrication on sharp curves has been commonly adopted as a method of reducing friction between the wheel flange and rail gauge face to minimize wear and energy consumption. Additionally, lubrication between the running surface of the low rail and wheel tread has recently been recognized as a significant factor in reducing the likelihood of low rail corrugation, squealing noise and rail gage face wear. This paper describes a frictionmoderating system (FRIMOS) for the interface between the top of the low rail and the wheel tread, consisting of a solid lubricant known as a friction moderator and a jetting device installed on the vehicle to apply the moderator to the wheel/rail interface.

Discussion on: “Optimality Properties and Driver Input Parameterization for Trail-braking Cornering”

Adverse wheel-rail contact geometry and flange lubrication have been implicated in a number of recent gage widening and rail rollover derailments. The underlying derailment mechanism is shown to be a loss of wheel set steering due to a reduction in wheel set rolling radius difference, leading to shear deformation of the truck and the generation of large lateral gage spreading forces. A series of theoretical analyses and field experiments have been conducted that demonstrate the loss of steering caused by the following wheel-rail contact conditions: 1.1. strong two-point contact between flanging wheels and rails;2.2. hollow wom wheel treads;3.3. heavy gage corner grinding on the rail;4.4. high rail gage face lubrication;5.5. dry railheads.Studies conducted at several gage widening and rail rollover derailment sites have shown that these conditions are not uncommon on North American railroads.

Tangential force variation due to the bogie direction reversal procedure

A range of tangential forces is generated within the contact patch when a wheelset moves on the rail. These forces are intensified when incorporating curved tracks and motored axle rail vehicles [Arrus, P., de Pater, A.D. and Meyers, P., 2002, The stationary motion of a one-axle vehicle along a circular curve with real rail and wheel profiles. Vehicle System Dynamics, 37(1), 29–58]. The wheelset is subject to flange contact if an unbalanced force remains in a curve towards the high rail gauge face. The resultant force in the transverse direction includes the lateral force, the radial force, and the creep forces in addition to the effect of the frequent wheelset displacement due to the kinematic oscillation [Iwnicki, S., 2003, Simulation of wheel–rail contact forces. Fatigue Fracture Engineering Material Structure, 26, 887–900]. This article has focused on a potential variation in some of the forces cited when the wheelset is subject to backward and forward movements. A severe wear rate observed within the wheel flange region in Iranian Railways was investigated by operating a test bogie on a curvaceous track. An obvious improvement in the wear rate and wear pattern of the wheels was attained when the second test bogie encountered a bogie direction reversal procedure. This enhancement is considered in this article from the force analysis standpoint.

Laboratory tests for seizure of rail and wheel steels

In the last decade side wear of rails and wheels was increasing in many countries. Topographic features of wearing surfaces of the rail gauge face and wheel flange lead to the assumption that seizure makes a heavy contribution to side wear especially at small radius curves. The exploration of seizure as a form (mode) of wear has been made. Two mechanisms of seizure designated as scoring and galling were observed in the laboratory tests. It is shown that the main peculiarity of scoring is local plastic deformation of both surfaces with formation of riders—hard movable centres consisting of two wedges with hardness ∼1.6 times greater than the basic metal. The main peculiarity of galling is plastic deformation of one surface only with formation of welding incrustation (protrusion) on the countersurface. An attempt was made to find the boundary of the scoring and galling area in the hardness–pressure–slippage–sliding velocity–environment space. Ways of counteracting side wear of rails and wheels following from the scoring mechanism of seizure are suggested.

Effects of wheel-rail contact geometry on wheel set steering forces

Adverse wheel-rail contact geometry and flange lubrication have been implicated in a number of recent gage widening and rail rollover derailments. The underlying derailment mechanism is shown to be a loss of wheel set steering due to a reduction in wheel set rolling radius difference, leading to shear deformation of the truck and the generation of large lateral gage spreading forces. A series of theoretical analyses and field experiments have been conducted that demonstrate the loss of steering caused by the following wheel-rail contact conditions: 1. 1. strong two-point contact between flanging wheels and rails; 2. 2. hollow wom wheel treads; 3. 3. heavy gage corner grinding on the rail; 4. 4. high rail gage face lubrication; 5. 5. dry railheads. Studies conducted at several gage widening and rail rollover derailment sites have shown that these conditions are not uncommon on North American railroads.