Wheel-rail Wear Research Articles

Dynamic wheel-rail interaction of a train crossing a turnout under traction/braking behaviour and research on rail wear of the turnout

In order to study the dynamic behaviour of a vehicle passing through turnouts under traction and braking conditions, as well as its influence on the wear of turnout rails, a high-speed vehicle-turnout rigid-flexible coupling dynamic model is established based on the coupling dynamic theory of vehicle and turnout, using China’s No. 18 high-speed turnout and CRH380 high-speed EMU as prototypes. The model is used to analyse wheel-rail creep characteristics, wheel-rail contact mechanics, and wheel-rail wear under traction and braking conditions. The results indicate that when a high-speed train passes through a turnout under traction or braking conditions, the longitudinal creepage of the wheel-rail will change due to the rotative speed difference generated by traction or braking. Furthermore, due to the existence of the lead curve, the longitudinal creep rate of the wheel-rail becomes even more complex when passing through the turnout in the diverging route. The calculations reveal that the traction behaviour of the train leads to a significant increase in wear at the front of the switch rail and nose rail, while the wear number of the switch rail in the heel of the frog after 6m increases significantly under braking conditions. The different impact characteristics of vehicle traction and braking conditions on turnout rail wear obtained in this study can provide guidance for optimizing and grinding the profiles of turnout rails at the throat of railway stations.

Wheel-rail wear characteristics of a modern tram passing curves with small radius

The wheel-rail wear was predicted for modern trams with independently rotating wheelset running on a groove-shaped rail. The tram vehicle-track coupled dynamics model, considering the wheel-rail multi-point contact, was developed using software UM to evaluate the dynamic responses of the vehicle and track. Hertz contact theory, the FastSim algorithm, and Archard material wear model were used to solve the normal contact stress, tangential contact stress, and wheel-ail wear, respectively. The wheel and rail profiles were updated when the wear depth reached to 0.1 mm. In calculation, the wheel and rail wear was calculated and analyzed separately. The results of groove rail and independently rotating wheelset wear predicted by this model coincided with relevant literature, which proved the effectiveness of this model. The wheel and rail wear characteristics of modern trams passing through curved tracks with small radii and the influence of wheel-rail friction coefficient on wheel and rail wear were calculated and analyzed using this model. The results show that the wheel and rail wear on the circular curve and the rear transition curve is more intense. The wheel wear is the most intense on circular curve while the rail wear is on the rear transition curve. The wear of inner and outer rails and wheels of wheelset one increases with the increase of wheel-rail friction coefficient while the wear of inner and outer wheels of wheelset three have no obvious change. The wear of the inner and outer rails is the most intense at the gauge corner position while is the lightest at the guard rail. The wear of wheelset one is more intense than that of wheelset three and the inner wheel wear is more intense than that of the outer wheel. The present analysis contributes to improve the life of tram wheel and rail and reduce the frequency of wheel-rail maintenance during operation.

Research on the influence of time-varying wear of wheel-rail profile on vehicle dynamic response

Employing a combination of field measurements and numerical simulations, this study initially evaluates the impact of simplifying wheel-rail profile wear on the calculation results of vehicle performance indicators. Subsequently, it investigates the influence of time-varying wear of wheel-rail profiles on the vehicle’s dynamic response, along with an analysis of change law in wheel wear depth and range under different wheel-rail profiles. The finding indicates that simplifying wheel-rail profile wear notably affect the accuracy of predicting wheel wear, with potential maximum prediction errors of up to 84 % compared to actual conditions. Furthermore, changes in the wheel-rail profile resulting from wear significantly impact the vehicle’s straight-line running performance and curve negotiation performance, particularly in the early and later stages of wheel-rail wear. Moreover, profiles in the mid-term wear stage significantly exacerbates wheel wear depth, demonstrating a maximum increase 4.33 times higher than that of the standard profile.

Impact of sand feed rate on the damage of railway wheel steels

The global railway industry plays a pivotal role in economic development, offering efficient transportation solutions. However, railways operating in desert environments face unique challenges due to windblown sand. This study investigates the influence of sand feed rates on wheel-rail wear in desert conditions. Experimental tests were conducted using a bidisc apparatus to simulate sand feed rates. Results indicate that low feed rates lead to spalling and pitting, while high rates increase abrasive and fatigue wear. A critical transition point at 0.4 g/min suggests sand-induced abrasion of wheel surfaces. Moreover, the research highlights the crucial role of sand feed rates not only in wear but also in surface roughness, further emphasizing the complex interplay between sand transport rates, adhesion, and wear mechanisms. These insights provide valuable guidance for mitigating wear-related challenges in desert railway operations and optimizing maintenance strategies.

The effectiveness of different wear indicators in quantifying wear on railway wheels of freight wagons

Railway infrastructure relies on the dynamic interaction between wheels and rails; thus, assessing wheel wear is a critical aspect of maintenance and safety. This paper focuses on the wheel–rail wear indicator T-gamma (Tγ). Amidst its use, it becomes apparent that Tγ, while valuable, fails to provide a comprehensive reflection of the actual material removal and actual contact format, which means that using only Tγ as a target for optimization of profiles is not ideal. In this work, three different freight wagons are evaluated: a meter-gauge and a broad-gauge heavy haul vehicles from South American railways, and a standard-gauge freight vehicle operated in Europe, with different axle loads and dissimilar new wheel/rail profiles. These vehicles are subjected to comprehensive multibody simulations on various tracks. The simulations aimed to elucidate the intricate relationship between different wear indicators: Tγ, wear index, material removal, and maximum wear depth, under diverse curves, non-compensated lateral accelerations (Anc), and speeds. Some findings showed a correlation of 0.96 between Tγ and wear depth and 0.82 between wear index and material removed for the outer wheel. From the results, the Tγ is better than the wear index to be used when analyzing wear depth while the wear index is more suited to foresee the material lost. The results also show the low influence of Anc on wear index and Tγ. By considering these factors together, the study aims to improve the understanding of wheel–rail wear by selecting the best wear analysis approaches based on the effectiveness of each parameter.

Effects of Lubricating Conditions on Wear Performance of U77MnCrH Rail

With the rapid development of railway towards being high speed and having heavy load capacity, the wheel–rail wear and rolling contact fatigue in the curve section with a small radius of freight have become the key problems in urban railways, which need to be solved urgently. The aims of this study were to compare the wear resistance with three different lubricating conditions on wheel–rail wear based on the wheel–rail rolling contact simulation tests. The wear loss, microhardness, and microstructure of the contacted surface of the rail were detected systematically. The results showed that the wear rates of rail were reduced by 71% for grease lubrication and 55% for solid lubrication, compared to those without lubrication. At the same time, the thickness of plastic deformation layer of rail samples were about 167 μm for the dry state, 138 μm for the solid lubrication state, and 128 μm for the oil lubrication state, respectively. It indicates that the thickness of the plastic deformation layer was significantly reduced under both grease and/or solid lubricating conditions. In addition, the microstructure of the deformation layer with two kinds of lubricated states was coarser and denser than that without lubricants. The average grain size of the deformation layer was approximately 0.22 μm under dry conditions and 0.32 μm under lubricated conditions. It also indicated that the changes in lubricants did not have a significant effect on the average grain size of the deformation layer. The results of the present study could provide theoretical reference for the development and design of lubricants used as rail materials.

The influence of asymmetric rail cant on rail corrugation in a small-radius curve section

A suitably designed rail cant can improve the wheel-rail alignment, effectively reduce the wheel-rail contact pressure and reduce the wheel-rail wear. However, the rail base cant has rarely been specifically designed for suppressing rail corrugation. Furthermore, no studies have yet been conducted on using different inner and outer rail cants in small-radius curve sections from the perspective of suppressing rail corrugations and wear. In this study, the growth rate index of rail corrugation is obtained by combining an impact hammer origin admittance test and a coupled vehicle-track multi-body dynamic model simulations. The wear depth of rail surface is obtained by combining a three-dimensional transient wheel-rail rolling contact model and Archard wear theory. From the overall perspective of preventing rail corrugation and slowing down rail wear, based on the multi-objective optimization using a particle swarm optimization algorithm, the optimal configuration of inner and outer rail cants in a small-radius curve section were determined as 1/22 and 1/40, respectively, which provided effective suppression of rail corrugation initiation and further development of rail wear.

Wheel profile optimization for intercity EMUs based on the Gaussian function correction method

Intercity EMUs are prone to wheel flange wear and tread wear due to the high operating speed and many small radius curved tracks. The problems caused by wheel wear have seriously affected the safety of high-speed railway operations in China. In this paper, based on the original LMA wheel profile, the Gaussian function correction (GFC) method is proposed to design the wheel profile. The GFC method mainly changes the root region of the wheel flange, to enhance the curve passing performance and reduce wheel wear of the vehicle. The optimal profile is optimized by the Kriging surrogate model (KSM) and the whale optimization algorithm (WOA). The wheel-rail contact characteristics, dynamic characteristics and the wheel wear of the wheel profiles before and after optimization are simulated and analyzed. The results show that the equivalent conicity of the optimized profile is reduced; the critical speed is increased by 9.3 km/h, the lateral ride index and comfort index of the vehicle are further reduced. The curve passing performance is also improved, the wheel-rail wear of the optimized profile is further reduced and the maximum wear depth of the wheels before and after optimization is 43.4e-9m and 34.1e-9m on the curved track with a radius of 500m, which is reduced by 21.43%. This method provides a reference and basis for wheel profile design and profile re-profiling of intercity EMUs.

Multiagent Reinforcement Learning for Active Guidance Control of Railway Vehicles with Independently Rotating Wheels

This paper presents a novel data-driven multiagent reinforcement learning (MARL) controller for enhancing the running stability of independently rotating wheels (IRW) and reducing wheel–rail wear. We base our active guidance controller on the multiagent deep deterministic policy gradient (MADDPG) algorithm. In this framework, each IRW controller is treated as an independent agent, facilitating localized control of individual wheelsets and reducing the complexity of the required observations. Furthermore, we enhance the MADDPG algorithm with prioritized experience replay (PER), resulting in the PER-MADDPG algorithm, which optimizes training convergence and stability by prioritizing informative experience samples. In this paper, we compare the PER-MADDPG algorithm against existing controllers, demonstrating the superior simulation performance of the proposed algorithm, particularly in terms of self-centering capability and curve-negotiation behavior, effectively reducing the wear number. We also develop a scaled IRW vehicle for active guidance experiments. The experimental results validate the enhanced running performance of IRW vehicles using our proposed controller.

Tribological and rheological performance of friction modifiers with different viscosities

Friction modifier (FM) in the rail/wheel applications is a special lubrication material that could be applied between the top of rail and the tread of wheel. The application of FM brings many benefits to the wheel-rail interface such as reducing noise, alleviating wheel-rail wear and mitigating corrugation. Viscosity is an important parameter to reflect fluid properties of FM materials. In this study, FM samples with different viscosities were prepared by changing the content of sodium carboxymethyl cellulose (CMC). The tribological and rheological performance of these FM samples were explored using the twin-disc testing machine and rotational rheometer. Furthermore, the relationship between the tribological and rheological results were tried to establish. The results showed that the increase in the content of CMC could increase the viscosity of FM and enhance the solid-like characteristic of FM, which could help FM reduce coefficient of adhesion (COA) level and wheel-rail damage. For the FM material developed in this study, the rational applying amount and the range of viscosity were about 15 μL/time and 200 Pa s to 400 Pa s, respectively, considering the factors of wheel-rail adhesion, wear, potential waste and pumping process in the practical application.

Optimisation design of grinding rail profile of metro lines for small radius curved track based on the GFC method: a case study

The rail side wear in small radius curved track of metro lines is a serious problem in railway maintenance, which reduces the curve passing performance and shortens the service life of the wheel and rail. To improve the vehicle's curve passing performance and reduce rail wear, a localized grinding profile design method for sharp curves was developed. The GFC profile generation method was used to generate the profiles for the curved track of the metro line. Then a metro vehicle-track dynamic model was established to calculate the wheel rail contact parameters, objectives and constraints. The profiles are optimized by the KSM-PSO optimization algorithm. Finally, a simulation analysis of the curve passing performance and wheel-rail wear of the optimized profile was carried out. When the metro vehicle passes through the curved track with a curve radius of 450m, the optimized rail profile can effectively reduce the wear of the rail, the wear of the high rail in the curved track is reduced by 20.18%. The localized rail grinding of the curved track can effectively reduce the rail side wear, the GQI index is also significantly improved. This study can guide the design of rail grinding profiles for the metro lines.

A Review of Wheel-Rail Contact Mechanics for Railway Vehicles

The dynamic behaviour of a railway vehicle is mainly depending on how the interaction of wheel and rail is taking place in running operation and what is the accuracy and efficiency of the applied contact models. Contact mechanics of railway vehicle is keyed with the history of the wheel-rail contact mechanics. For a designer of braking and traction control systems, it is essential to go through the fundamental knowledge of forces produced due to contact of wheel-rail and geometric constraints as well as moments to assess the wheel-rail wear and to evaluate the ride performance indices. This article gives a brief review to the evolution and present scenario of the previously published contact theories to get rid of the wheel-rail contact problems. The key theories which have most attention to solve normal contact problems are Hertzian contact theory as well as non-Hertzian contact theory, whereas, to tackle the problems related to tangential contact, linear as well as non-linear theories proposed by Kalker, theory proposed by Polach, FASTSIM, CONTACT etc are considered in this paper. This paper reviews the state-of-the-art of past studies based on experiments to study various contact models.

Experimental study on the effect of solid lubricants on wheel rail contact wear and surface hardness evolution

PurposeThe CL60 steel wheels of subway vehicles operating on specific lines require frequent refurbishment due to rapid wear and tear. Considering this issue, MoS2-based and graphite-based solid lubricants are used to reduce the wear rate of subway wheels and extend their service life.Design/methodology/approachUnder laboratory conditions, the effect of MoS2-based and graphite-based solid lubricants on the friction and wear performance of subway wheels and rails was evaluated using a modified GPM-60 wear testing machine.FindingsUnder laboratory conditions, MoS2-based solid lubricants have the best effect in reducing wheel/rail wear, compared to the control group without lubrication, at 2 × 105 revolutions, the total wheel-rail wear decreased by 95.07%. However, when three types of solid lubricants are used separately, the hardness evolution of the wheel-rail contact surface exhibits different characteristics.Practical implicationsThe research results provide important support for improving the lifespan of wheel and rail, extending the service cycle of wheel and rail, reducing the operating costs of subway systems, improving the safety of subway systems and providing wear reduction maintenance for other high wear mechanical components.Originality/valueThe experiment was conducted through the design and modification of a GPM-60 testing machine for wear testing. The experiment simulated the wheel-rail contact situation under actual subway operation and evaluated the effects of three different solid lubricants, MoS2-based and graphite-based, on the wear performance and surface hardening evolution of subway wheel-rail.

Active Steering Controller for Driven Independently Rotating Wheelset Vehicles Based on Deep Reinforcement Learning

This paper proposes an active steering controller for Driven Independently Rotating Wheelset (DIRW) vehicles based on deep reinforcement learning (DRL). For the two-axle railway vehicles equipped with Independently Rotating Wheelsets (IRWs), each wheel connected to a wheel-side motor, the Ape-X DDPG controller, an enhanced version of the Deep Deterministic Policy Gradient (DDPG) algorithm, is adopted. Incorporating Distributed Prioritized Experience Replay (DPER), Ape-X DDPG trains neural network function approximators to obtain a data-driven DIRW active steering controller. This controller is utilized to control the input torque of each wheel, aiming to improve the steering capability of IRWs. Simulation results indicate that compared to the existing model-based H∞ control algorithm and data-driven DDPG control algorithm, the Ape-X DDPG active steering controller demonstrates better curving steering performance and centering ability in straight tracks across different running conditions and significantly reduces wheel–rail wear. To validate the proposed algorithm’s efficacy in real vehicles, a 1:5 scale model of the DIRW vehicle and its digital twin dynamic model were designed and manufactured. The proposed control algorithm was deployed on the scale vehicle and subjected to active steering control experiments on a scaled track. The experimental results reveal that under the active steering control of the Ape-X DDPG controller, the steering performance of the DIRW scale model on both straight and curved tracks is significantly enhanced.

Dynamic interactions of tram-turnout coupling system in embedded turnout area

Embedded turnout is one of the key facilities in the embedded track network of modern tram systems. In this study, the damping performance and track stiffness of an embedded turnout are tested on site. A multi-rigid body dynamics model of the tram and a finite-element dynamics model of the embedded turnout are established, and the two models are coupled based on the wheel-rail contact theory for the turnout area. Next, the dynamic responses of the tram passing through the embedded turnout are analyzed. The results show that the embedded turnout has favorable damping performance. The high stiffness of variable section rails at the switch and frog would lead to an increase in the wheel-rail dynamic force. When the tram passes through the embedded turnout, the wheel-rail vertical force reaches maximum values of 106.3 and 35.2 kN at the frog and switch, respectively; the maximum wheel derailment coefficient and wheel weight reduction rate are 0.49 and 0.57, respectively, which are within the safety limit specified in the Standards; the maximum lateral and vertical vibration accelerations of the tram body are 0.38 and 0.71 m/s2, respectively, satisfying the comfort requirements; the wheel–rail wear work at the switch is greater than that at the frog.

An Indirect Identification Method for Train Basic Resistance Parameters

The train basic resistance characteristic is crucial for ATO performance. However, this characteristic is slow time-varying with wheel rail wear and fast time-varying with weather conditions. The parameters of train basic resistance are difficult to measure directly, usually only a set of empirical parameters can be obtained through repeated experiments. These factors result in an inconsistency between the model parameters in the ATO controller and the actual train basic resistance parameters (TBRP), leading to a decrease in the effectiveness of the model-based controller. Therefore, this paper proposes an indirect TBRP identification method based on speed trajectory fitting to improve the effectiveness of the TBRP for model-based ATO controllers. Firstly, the original TBRP identification problem is transformed into an optimization problem, which is to minimize the deviation between the actual speed trajectory and the model-calculated one. Then, the Newton’s method is used to accelerate the search for the best set of TBRPs with minimum deviation. Finally, case studies are used to verify the effectiveness of the proposed method.

Research on the effect of rail cant on the dynamic performance and wear characteristics of subway vehicles

The rail cant is a critical geometric parameter of the track, which plays a significant role in the vehicle dynamics performance and wheel wear characteristics. Regarding the abnormal rail cants on the test route, this study employs a combined approach of field measurements and numerical simulations to investigate the influence of deviations from the standard values of rail cants on the vehicle’s straight-line operating performance and wheel wear. Additionally, it analyzes the difference in the effects of asymmetric rail cant on the inner and outer wheel's curve negotiation performance and wear characteristics. The research demonstrates that for straight track sections, rail cants ranging from 1/30 to 1/10 significantly reduce the critical speed of the wheel-rail wear profile, thereby affecting the operational stability of the vehicles. Moreover, the wheel-rail wear profile more prone to significant wear depths when the rail cants are within the range of 1/30 to 1/10. For curved track sections, when the outer rail cant is stable at 1/40, the amplitude fluctuation of the inner rail cant has a more significant impact on the curve negotiation performance of the outer wheel. Specifically, when the inner rail cant is within the range of 1/60 to 1/50, the derailment coefficient and wheel-rail lateral forces of the outer wheel increase significantly, and they are directly proportional to the degree of wheel-rail wear. When the inner rail cant is 1/30, the wheel-rail profiles at different wear stages often exhibit optimal curve negotiation performance. Moreover, an inner rail cant of 1/30 tends to achieve smaller wear depths at various wear stages.

A framework of high-order wheel polygonal wear mitigation for China's high-speed trains

High-order wheel polygonal wear is a significant concern on China’s high-speed trains; thus far, no satisfactory solution to prevent polygonal wear has been provided. In this study, a simplified vehicle-track coupling dynamic model was established, and the frequency response functions (FRF) of the wheel-rail force were obtained under multiple wheelsets conditions. After integrating a wheel-rail wear model, the rail localized bending modes (RLBM) were recognized as critical factors for the amplitude-frequency and phase-frequency properties of the wheel-rail force response and further gave rise to the growth of high-order polygonal wear. Consequently, rail dynamic vibration absorbers (DVA) were introduced into the vehicle-track coupling dynamic model as single-degree-of-freedom rigid bodies arranged at equal intervals along the track. The influencing mechanism of rail DVAs on the rail localized bending resonance, as well as the resulting polygonal wear, was investigated in detail. Results suggested that the rail localized bending resonance could be easily suppressed when the tuned frequency of the rail DVAs approaches the resonance frequency. However, due to newly generated resonance peaks, the polygonal wear was observed to persist. The phase-frequency property of the wheel-rail force response is a determining contributor to the growth trend of polygonal wear; therefore, the rail-tuned DVA should be designed to force the phase lag out of the positive growth region, namely 90° to 270°. Our results indicated that a DVA with a tuned frequency of 450 Hz could effectively slow the development of high-order polygonal wear on China’s high-speed trains, and the shorter installation interval of rail DVAs improves the suppression effect. This study proposed a phase-based design rule for rail DVAs to achieve wheel-rail periodic wear mitigation.

A Review of Wheel-Rail Dynamic Behavior on Curved Tracks

With a speedy advancement in vehicle speed and transport capability, a huge challenge has been imposed to improve railway vehicle dynamic behaviour and track design to ensure the optimum performance of railway vehicles and tracks. To safely negotiate the vehicle speed on circular and transition curve tracks several aspects such as wheel-rail wear, smooth ride and vehicle stability need to be analysed. The investigators have paid great attention to exploring the compatibility among vehicle stability and curving ability, parametric analysis and optimization of curving performance, minimising the wheel-rail wear and curve squeal noise etc. The present paper focuses on reviewing these past efforts made by the researchers.

Speed Limit of Linear Induction Motor Subway Trains Running through 65 m Radius Curves on Yard Line

Linear induction motor (LIM) subway yard line often have very-small-radius curves and small turnouts with “S”-shaped curves in the middle. The lateral stability of the train is low, and wheel-climb (slipway) derailments often occur at a speed of 10 km/h. To study the derailment safety and speed limit of a linear motor subway train running through yard line, a coupling dynamic model of the train-track system is established, fully considering the driving characteristics of the linear motor, characteristics of the linear motor train, and track structure. The safety of train derailment is judged by the over-limit time of the derailment coefficient. Under the premise of a safe operation, the variations in the derailment coefficient, out-of-limit time, wheel unloading rate, and wheel-axle lateral force with the train running speed are studied. When the train runs at speeds below 25 km/h, for both new and worn rails, the derailment coefficient and lateral force of the wheel axle at each speed exceed the safety limits, and are less affected by changes in the speed. The duration of the derailment coefficient is within the safety limit because the speed of crossing the curve is low, and thus the train will not overturn and derail. Rail wear reduces the train derailment safety through the yard line, while the wheel wear improves the train derailment safety through the yard line. Considering the actual state of the yard line (wheel-rail wear, irregularity, etc.), the speed of the linear motor subway train running through the yard line should be limited to below 15 km/h.