Railway Wheel Wear Research Articles

On the Polygonal Wear Evolution of Heavy-Haul Locomotive Wheels due to Wheel/Rail Flexibility and Its Mitigation Measures

Wheel polygonal wear can immensely worsen wheel/rail interactions and vibration performances of the train and track, and ultimately, lead to the shortening of service life of railway components. At present, wheel/rail medium- or high-frequency frictional interactions are perceived as an essential reason of the high-order polygonal wear of railway wheels, which are potentially resulted by the flexible deformations of the train/track system or other external excitations. In this work, the effect of wheel/rail flexibility on polygonal wear evolution of heavy-haul locomotive wheels is explored with aid of the long-term wheel polygonal wear evolution simulations, in which different flexible modeling of the heavy-haul wheel/rail coupled system is implemented. Further, the mitigation measures for the polygonal wear of heavy-haul locomotive wheels are discussed. The results point out that the evolution of polygonal wear of heavy-haul locomotive wheels can be veritably simulated with consideration of the flexible effect of both wheelset and rails. Execution of mixed-line operation of heavy-haul trains and application of multi-cut wheel re-profiling can effectively reduce the development of wheel polygonal wear. This research can provide a deep-going understanding of polygonal wear evolution mechanism of heavy-haul locomotive wheels and its mitigation measures.

Predicting railway wheel wear by calibrating existing wear models: Principle and application

The accuracy of physics-based wheel wear prediction approaches depends not only on the vehicle-track dynamics model but more importantly on the wear model. The currently available wear models, however, were developed for specific wheel/rail materials and under fixed operational conditions, and they need to be calibrated when used in new operational conditions. In this paper we introduce a data-driven approach into the physics-based approach to automatically calibrate the existing wear model so that it can be extended to a new operational scenario. Specifically, based on a one-year follow-up measurement data on the wheel profile evolution of a metro train commuting on a Guangdong metro line, we introduce radial basis function (RBF) and particle swarm optimization (PSO) to determine the boundary of each wear regime and the wear coefficient for each wear regime in the Archard-local model. Finally, we present a calibrated Archard-local model and then apply it to two cases. One application case shows that the calibrated model can be used for long-term wear prediction and another case shows that the calibrated model can be used to roughly estimate the wear evolution over the tread region of vehicles operating on other China metro lines.

A new DFT-based dynamic detection framework for polygonal wear state of railway wheel

Polygonal wear of railway wheels will accelerate the failure of critical structure. It is of great significance to monitor their state in service. However, affected by the frequently changed operating speed and track irregularity, the operation process of the vehicle is typically non-stationary. The traditional analyzing methods are not ideal for dealing with the non-stationary processes, causing the accurate detection of wheel polygon wear state very hard. This paper proposes a dynamic detection framework based on iterative modified discrete Fourier transform to solve the above problem. Firstly, extract the relatively stationary short-time signals from the original signal by setting appropriate stationarity test conditions. Secondly, obtain the wheel polygon's vibration frequency and period by taking the iterative calculation and analysis. Thirdly, truncate the extracted short-time signal again to get a new short- time signal representing an integer multiple of the wheel polygon's vibration period. Finally, combined with the wheel polygon's dynamic characteristics, take the frequency domain analysis to the new short-time signal and realize the accurate estimation of the wheel polygon wear state. The simulation and experiment results show that the detection framework can effectively eliminate the influence of non-stationary factors and better solve the inherent defects of traditional analysis methods.

Numerical calculation of wear in rolling contact based on the Archard equation: Effect of contact parameters and consideration of uncertainties

Wear in rolling contact is a complex phenomenon because it is multi-scale and multi-physical by nature and involves many strongly correlated parameters. It makes the numerical calculation of wear very challenging. In order to simulate wear, a better understanding of the influencing parameters involved in the wear calculation is of importance. This work presents a new numerical calculation of railway wheel wear based on Archard's equation combined with a spatial statistic approach called the Universal Kriging technique. The influence of factors, such as the contact mechanics model and the wear coefficient were studied through numerical experiments. The outcomes provide a new insight into the roles of the contact modelling and of the uncertainties of the wear coefficient in the numerical calculation of wear under various contact conditions. By considering the uncertainties of the wear coefficient, the approach provides a min.-max. range for wear estimation instead of a single deterministic value; furthermore, it can provide a detailed wear distribution over the contact patch for damage analysis. In combination with an accurate model of wheel-rail contact, this new wear model offers a more realistic wear prediction compared to the methods presently used for wheel wear estimation in railway vehicles.

The effect of railway wheel wear on reprofiling and service life

The aim of this study is to analyze how wheel wear affects the wheel reprofiling and service life and evaluate if these aspects can be improved by a new optimal wheel profile design. The NSGA-II multi-objective optimization algorithm was used to generate three optimal wheel profiles that are used alongside the current BRA profile for this analysis. After the optimization process, wear simulation was done to verify if the profiles performance will be maintained over time and to analyze how the worn profile shape affects reprofiling and service life. To quantify this, the worn profiles are used to simulate the reprofiling process in order to estimate the wheel's expected service life according to the wheels geometric tolerances. For this railway, an increase of at least 17% of service life can be expected by reducing the hollow wear maintenance limit from 3 mm to 2.5 mm while an increase of at least 29% can be expected from changing the limit from 3 mm to 2 mm.

Corrosion of worn out railway wheels

Purpose. It is necessary to study the conditions for the initiation of fatigue damages and the weakening effect of corrosion on the corrosion-fatigue wear of railway wheels. The aim of the work was to study the effect of the structure of wheel steel on the development of corrosion processes. Methods. To study the features of the development of corrosion damages in wheel steel the metal of worn wheels (1, 2; samples from the rolling surface, from the inner part of the rim body and from the disk) was used. Accelerated corrosion tests were carried out at room temperature in a special chamber in a humid atmosphere (relative humidity 80...83 %) containing 10 mg/m3 SO2, as well as NO and NO2, which is close to the effect of industrial atmospheres. Metallographic studies were carried out using a Neophot-21 microscope. Results. The features of wheel steel corrosion in different areas of worn out railway wheels are investigated. It is shown that the different corrosion rate of wheel steel is explained by its different structural state (degree of dispersion of pearlite, grain size, nature of the deformed structure). It was found that the rolling surface and the metal of the disc corroded faster than the metal from the center of the rim. Scientific novelty.The features of the mechanism and the rate of development of corrosion of wheel steel in different areas of worn out railway wheels during high-speed tests in an environment close to an industrial atmosphere are established. It is shown that the nature of the microstructure of wheel steel affects the corrosion rate. It is shown that in used wheels the rolling surface corroded faster than the metal from the central part of the rim, which is explained by the effect of stresses created by plastic deformation in a thin surface layer. It was found that the areas of the "white layer" on the rolling surface contribute to the slowdown of corrosion, which is associated with its ultradispersed structure. It was shown that the metal of the disk corroded faster than the metal from the central part of the rim due to the coarser ferrite-pearlite structure of the disk and the presence of ferritic banding.Practical significance.The use of the results obtained will allow developing anti-corrosion measures for railway wheels, which will prevent the formation of various types of defects during their operation.

IMPLEMENTATION OF MACHINE LEARNING TECHNIQUES FOR PROGNOSTICS FOR RAILWAY WHEEL FLANGE WEAR

Machine learning has become an immensely important technique for automatically extracting information from large data sets. By doing so, it has become a valuable tool in various industries. In this investigation, the use of machine learning techniques for the production of railway wheel prognostics was investigated. Metrorail’s railway wheel wear data was used as a case study for this investigation. The goal was to demonstrate how machine learning can used on the data generated by Metrorail’s routine operations. Three machine learning models were implemented: logistic regression, artificial neural networks, and random forest. The investigation showed that all three models provided prognoses with an accuracy of over 90 per cent, and had an area under curve (AUC) measurement exceeding 0.8. Random forest was the best performing model, with an AUC measurement of 0.897 and an accuracy of 93.5 per cent.

Numerical study of railway wheel wear on roller rigs

Numerical study of railway wheel wear on roller rigs

Study on wheel polygonization of a metro vehicle based on polygonal wear simulation

A long-term iterative wear model is proposed to predict the development of polygonal wear of railway wheels. To improve the simulation accuracy, the time step for numerical integration, wheel profile updating strategy and curve fitting methods are analysed. Then a metro vehicle with 8th to 9th order polygonal wheel is presented as a case study where a vehicle resonance speed leading to a peculiar growth of wheel polygonization is identified by simulation and validated through field tests. Based on the simulated polygonal wear evolutions and analyses on vehicle vibrations, the mechanism of wheel polygonization is explained. Finally, two new strategies to investigate wheel polygonization are proposed.

Use of the fatigue index to study rolling contact wear

Although both wear and fatigue are inevitably associated with the wheel/rail contact, they are normally studied as different phenomena and both are commonly considered excluding. Wear of railway wheels and rails is usually studied by relating wear rate to the Tγ or Tγ/A parameters or by plotting the so called “wear maps”, where different rolling parameters are related to the wear rate. On the other hand, fatigue in wheel/rail contact is mainly studied from the surface and subsurface stress or deformation fields and from the crack growth rate.However, one of the main causes of wear in rolling contact is the loss of material due to delamination processes that have their origin in the presence of surface fatigue cracks. So, if wear and fatigue are related, it should be possible to study both of them using the same method.In this paper, the fatigue index, based on the shakedown theory and used to predict the surface initiated fatigue of railway wheels, is proposed as a means to study the wear rate in rolling contact. The fatigue index is directly related to the apparition and growth of fatigue cracks at the surface and, thus, directly related to the peeling and spalling processes that constitute the severe and catastrophic wear mechanisms.The data collected from a series of twin-disc tests show that the wear rate correlates with the fatigue index following an exponential evolution independently of the normal load. Furthermore, a fatigue index around 0 marks the onset of severe wear.

Comparison of wear models for simulation of railway wheel polygonization

This paper presents a comparative study on the applicability of existing popular wear models in simulation of railway wheel polygonization. Four representative wear models developed by BRR (British Rail Research), KTH (Royal Institute of Technology), USFD (University of Sheffield), and Professor Zobory respectively, are selected for the comparison with consideration of global and local methods. All the wear models are converted to calculate the instantaneous wear of one contact patch. Uniform expression of the converted wear functions is derived analytically with the equivalent wear coefficient as a useful index to identify the proportional relationship among the wear models quantitatively. Several scenarios grouped by harmonic excitation and random excitation are adopted to assess the fluctuation of the instantaneous wear depth calculated by different wear models. The evolved polygonal wear around the wheel circumference is also compared among the wear models based on a developed prediction program. Simulation results show that all the wear models being investigated in this paper present a similar ability to reflect the fluctuation of the instantaneous wear under various circumstances. Specifically, all wear models can correctly reflect the frequency characteristics of the excitation in a general sense, and the fluctuation phase of the instantaneous wear is obtained with almost the same result among the wear models. There is a very good consistency of trend for all local wear models to simulate the evolved polygonal wear. The mean value and the fluctuation amplitude of the instantaneous wear, as well as the roughness level of the evolved polygonal wear, are all determined by the original wear coefficients used. Besides, the global method is not suitable for calculating the polygonal wear of railway wheels as some sharp points might be generated by the absolute operation for the global WI (Wear Index).

Effects of full-stops on shoe-braked railway wheel wear damage

The purpose of this work is to gain a better understanding of the complex damage phenomena taking place at the railway wheel/brake block interface due to thermo-mechanical loading. Initially, full-stop braking was studied using Finite Element (FE) simulations to estimate the temperature reached in the wheel rim. Experiments to reproduce wheel damage were conducted with a two-disc machine using test conditions that were based on the results of the FE simulations. Three different wheel steels were tested against the same cast iron shoe material. The evolution of the wheel disc damage was studied at various numbers of cycles under fixed contact pressure and sliding speed. The friction coefficient and the temperature on the wheel disc surface were measured during the tests. At the end of the experiments, the wheel disc was examined and characterized. Cross-sections were observed with an optical microscope and the hardness was measured as a function of the depth to investigate the damage mechanisms that occurred at surface and subsurface. Material transfer from the shoe specimen to the wheel specimen results in the formation of a discontinuous “third body” layer, and that layer plays a key role in the evolution of the wheel disc damage. When the transferred layer of brake material is worn away, detachment of steel from the wheel disc surface occurs, probably promoting the crack nucleation. In addition, wear debris from both disc materials promotes three-body abrasive wear of the wheel disc surface.

Advances in Iran railway wheel wear management: A practical approach for selection of wheel profile using numerical methods and comprehensive field tests

Owing to increases in route traffic, axle load, and incompatible combinations of wheel-rail profiles in freight wagons, the Iran railway network has encountered a tremendous increase in localized wheel flange wear. Thus, a strategy was applied to select a new wheel profile to improve wheel-rail interaction and decrease overall localized wheel flange wear. In this research, a practical method was applied for an optimal selection of a wheel profile to minimize wheel wear for three types of freight bogies commonly employed for freight open wagons, including the three-piece 18100, Y25, and H665 series. The research procedure to select the final candidates was based on a wear behaviour study of verified bogie vehicles’ numerical models in operation, as equipped with various wheel profiles via conventional wheel-rail wear models. Then, comprehensive field tests were conducted to monitor the flange wear depth and total wear rate of the final wheel profile candidates in operation conditions, from the aspects of one and multiple wheel-rail contact point distribution, wear rate, and stability of the worn wheel profile for 56,500 km. Eventually, the optimal wheel profile was recommended, in consideration of the population of each bogie type. Some technical and field study aspects of the work were also discussed.

Use of railway wheel wear and damage prediction tools to improve maintenance efficiency through the use of economic tyre turning

This paper investigates the wear rate and pattern for wheels turned with thin flanges using economic tyre turning. Economic tyre turning refers to the process of turning wheels to a profile that has the same tread shape but a thinner flange than the design case profile, allowing less material to be removed from the wheel diameter during re-profiling. Modern wheel lathes are typically capable of turning such profiles but the GB railway group standards do not currently permit their use. The paper demonstrates how the wheel profile damage model (WPDM) can be used, with a good degree of accuracy, to predict both the magnitude of wheel wear and the worn profile shape of the design and economic tyre turning re-profiled wheels for service mileages exceeding 100,000 miles. The WPDM simulations were run for two typical electric multiple units (one suburban and one intercity train fleet) and a two-axle freight wagon. Additionally, it discusses the calibration methodology used to adjust the wear coefficients contained within the Archard wear model to improve the accuracy of the WPDM simulation results for specific routes and vehicle types. Furthermore, this paper presents the findings of a trial of economic tyre turning on a fleet of intercity trains. The analysis is extended to predict the effect of using economic tyre turning on rail rolling contact fatigue for typical routes and operating conditions using a series of vehicle dynamic simulations. The analysis considers new 56E1 and 60E2 rails together with a selection of worn wheel. The research provides valuable evidence to support a future change to the standards which will allow train operators/maintainers to implement economic tyre turning policies.

Influence of non-metallic inclusions and products of corrosion on the wear of railway wheels tread

Formulation of the problem . It is of interest to investigate the effect of nonmetallic inclusions and corrosion products of wheel steel on the formation of wear particles on the tread of railway wheels. It is also necessary to identify the specifics of the interaction of wheel steel with the surrounding atmosphere during the operation of railway wheels. The purpose of the article is to study the mechanisms of formation of wear particles on the surface of rolling of railway wheels during operation. Methodology . The effect of inclusions and corrosion products on the mechanism of wear of railway wheels made of R7 steel, which worked for about 5 years under the passenger train, was studied. The wheels were removed from service due to the extreme wear of the rims. We studied the macrostructure and microstructure of wheel steel along the width of the rims. The research was carried out by several methods: metallographic (Neophot−21), electron microscopy (JSM−35). Findings . The features of the formation of wear particles near nonmetallic inclusions and corrosion products related to structural changes near the rolling surface of railway wheels as well as to the interaction of steel with the surrounding atmosphere during operation were investigated. The influence of various factors on the role of nonmetallic inclusions and corrosion products in the formation of wear particles is shown, which makes it possible to predict the nature of wear of the rolling surface of railway wheels under various operating conditions. Originality . The main sources and the mutual influence of various factors on the formation of wear particles near nonmetallic inclusions and corrosion products have been established, which makes it possible to predict the nature of wear of the rolling surface of railway wheels under various operating conditions. Practical value . The use of the obtained results will allow to develop methods and regimes of smelting of wheel steel, allowing to influence the size, composition, structure and distribution of non-metallic inclusions, as well as to develop anticorrosion measures in order to improve the reliability and durability of railway wheels.

Prediction of railway wheel wear and its influence on the vehicle dynamics in a specific operating sector of Indian railways network

In railway operations, wear prediction due to wheel-rail interaction is crucial for different aspects such as running stability, passenger safety and comfort, life cycle optimization and maintenance scheduling. In this article, wheel wear is estimated through co-simulation between multi-body vehicle dynamic model developed in Adams™ VI-Rail™ software and wear evolution model developed in MATLAB® software. Semi-Hertzian/STRIPES approach and modified Kalker's FASTSIM approach are used for calculating normal and tangential stresses, respectively. The contact patch obtained from dynamic analysis is discretized into strips and variations of contact angle and spin for each strip, although small, are taken into account. Archard's wear formulation is applied for each strip within the contact patch. The wheel profiles are smoothened and are updated at intervals for further dynamic analysis. This way, the outputs from dynamic analysis (contact patches, creep forces, etc.) are input to the wear evolution model and the outputs from the wear evolution model (worn wheel profiles) are fed to the dynamic analysis. The wear at the flange and tread portions of the wheels during the normal service condition in an operational track sector between two major rail stations in India, containing curved and straight portions, speed variation (acceleration and braking), and corresponding track configurations (super-elevation, irregularities, etc.) are estimated and the wheel re-profiling schedule was obtained. In addition, the influences of the various stages of wheel wear on the dynamic responses such as curving performance, critical speed and ride comfort of the railway vehicle on the simulated test track are evaluated to justify the maintenance/wheel re-profiling schedule.

TERMS OF ENSURING QUALITY OF THE RAILWAY WHEELS BUILT UP BY WELDING

Purpose. The paper assumes to set the basic laws in determining the structure and physical-mechanical properties of wheel steels during arc welding technology and to develop the recommendations for reconstruction of railway wheel wear surfaces that will improve the reliability and safety of traffic in terms of increasing operating loads. Methodology. To achieve this purpose the paper studied 1) the influence of operating loads on structural changes and properties of metal wheels; 2) the impact of arc welding on structural and phase composition and properties of the metal heat-affected zone, its resistance to brittle and slow fracture; 3) the impact of welded metal on the formation of the stress state of the welds and their resistance to formation cracks; 4) wear resistance of built up metal during friction-slip of the «wheel-rail» pair. Findings. The most intense zone of the rolling profile of freight railway wheels during operation is a place of transition from rolling surface to the ridge. Therefore, the wheel building up by welding requires first of all the increased resistance to brittle fracture of metal in this area. It is established that welding in the metal of the wheel heat-affected zone cause formation of the hardened bainite-martensite structures. The minimum metal cooling rate, at which the martensite start forming is 8°C / s (in the range of 600…500°C) when the content of carbon in steel is 0.58% and 2°C/s at 0.65% of carbon. It is shown that to increase resistance to cracking it is necessary to limit the cooling rate to 16.0°C/s when the carbon content is C < 0.60% and to 8.0°C / s when C = 0.60…0.65%. Under these conditions, the metal has rather high ability to mikroplastic deformation without cracking. It was founded that to improve the critical stress intensity factor К1С at brittle fracture it is necessary to provide conditions when welding would result in the built up structure that does not contain upper bainite and the martensite share does not exceed the number of lower bainite (ratio of M/Bn < 1). It is proved that exposure of wheels within 3.5-4.5 hours at 100°C after welding, during their slow cooling improves resistance to brittle fracture of metal heat-affected zone by 1.8-2.3 times. This is due to the removal of diffusion hydrogen from the metal and reduction of the ІІ type stress in the lath volume of bainite and martensite by 1.5. Originality. The author has developed the idea of the structural-phase changes that occur in the metal of railway wheels during arc welding. The relation between the carbon content in steel, cooling rate during welding and resistance to cracking and brittle fracture was found. The authors determined the influence of after-welding wheel cooling conditions on the metal properties. Practical value. Technological recommendations for railway freight wheel building up by welding were developed. Their application will improve quality of the railway wheels built up by welding, reliability and safety of traffic in conditions of growing operating loads.

Predicting railway wheel wear under uncertainty of wear coefficient, using universal kriging

Railway wheel wear prediction is essential for reliability and optimal maintenance strategies of railway systems. Indeed, an accurate wear prediction can have both economic and safety implications. In this paper we propose a novel methodology, based on Archard's equation and a local contact model, to forecast the volume of material worn and the corresponding wheel remaining useful life (RUL). A universal kriging estimate of the wear coefficient is embedded in our method. Exploiting the dependence of wear coefficient measurements with similar contact pressure and sliding speed, we construct a continuous wear coefficient map that proves to be more informative than the ones currently available in the literature. Moreover, this approach leads to an uncertainty analysis on the wear coefficient. As a consequence, we are able to construct wear prediction intervals that provide reasonable guidelines in practice.

Influence of polygonal wear of railway wheels on the wheel set axle stress

The coupled vehicle/track dynamic model with the flexible wheel set was developed to investigate the effects of polygonal wear on the dynamic stresses of the wheel set axle. In the model, the railway vehicle was modelled by the rigid multibody dynamics. The wheel set was established by the finite element method to analyse the high-frequency oscillation and dynamic stress of wheel set axle induced by the polygonal wear based on the modal stress recovery method. The slab track model was taken into account in which the rail was described by the Timoshenko beam and the three-dimensional solid finite element was employed to establish the concrete slab. Furthermore, the modal superposition method was adopted to calculate the dynamic response of the track. The wheel/rail normal forces and the tangent forces were, respectively, determined by the Hertz nonlinear contact theory and the Shen–Hedrick–Elkins model. Using the coupled vehicle/track dynamic model, the dynamic stresses of wheel set axle with consideration of the ideal polygonal wear and measured polygonal wear were investigated. The results show that the amplitude of wheel/rail normal forces and the dynamic stress of wheel set axle increase as the vehicle speeds rise. Moreover, the impact loads induced by the polygonal wear could excite the resonance of wheel set axle. In the resonance region, the amplitude of the dynamic stress for the wheel set axle would increase considerably comparing with the normal conditions.

The development of a crack propagation model for railway wheels and rails

AbstractRolling contact fatigue (RCF) and wear of railway wheels and rails are the main phenomena that affect their maintenance costs. When crack propagation and wear rates can be predicted, maintenance planning can be optimised, and cost‐effective measures can be developed. Several RCF models exist, but none which can be used in combination with vehicle dynamics simulations and can predict the actual crack depth. This study shows the development of a crack propagation model that can be applied for both railway wheels and rails. Two unknown material parameters in the model were calibrated against crack measurements in a curve on the Dutch railways over a period of 5 years. Two different RCF models were used to calculate the stress magnitudes for the propagation model. The propagation model can be used in combination with vehicle‐track dynamics simulations and shows promise in predicting the actual crack depth and/or surface length. Further research is needed to determine the model's validity for other operational conditions.