Wheel-rail Interaction Research Articles

Optimizing Railway Tribology: A Systematic Review and Predictive Modeling of Twin-Disc Testing Parameters

Twin-disc testing is crucial for understanding wheel–rail interactions in railway systems, but the vast array of testing parameters and conditions makes data interpretation challenging. This review presents a comprehensive analysis of the twin-disc literature experimental data, focusing on how various parameters influence friction and wear characteristics under stationary contaminant conditions. We systematically collected and analyzed data from numerous studies, considering factors such as contact pressure, speed, material hardness, sliding speeds, adhesion, and a range of contaminants. This research showed inconsistent data reporting across different studies and statistical analyses revealed significant correlations between testing parameters and wear rates. For sand-contaminated tests, a correlation between particle size and flow rate was also highlighted. Based on these findings, we developed a simple predictive model for forecasting wear rates under varying conditions. This model achieved an adjusted R2 of 0.650, demonstrating its potential for optimizing railway component design and maintenance strategies. Our study provides a valuable resource for researchers and practitioners in railway engineering, offering insights into the complex tribological interactions in wheel–rail systems and a tool for predicting wear behavior.

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.

Research on the wheel wear and rolling contact fatigue of metro vehicle induced by the rail corrugation

The rail corrugation is a common disease on the track, which exacerbates the wheel-rail interaction and accelerates wheel wear and crack propagation. This study focuses on the wheel wear and rolling contact fatigue of metro vehicle under the rail corrugation. Firstly, the characteristics of the rail corrugation under service conditions are determined by the statistical analysis of the field data, and the rail corrugation is applied to the established vehicle-track coupled dynamics model. Then, the wear index and the work of friction force as indicators of wheel wear are studied. Finally, based on the Shakedown Map and the criterion of maximum amplitude of shear stress, the simulation analysis of wheel-rolling contact fatigue under the rail corrugation is carried out. The results show that the increases in superficial fatigue index and accumulated fatigue are 1.52 and 6.16 times in the wavelength range of 30-90 mm larger than those in the range of 90-210 mm, respectively. Furthermore, the cracks more easily occur 2-4 mm from the outer surface of wheel, and expand along the wheel tread.

Study on the effect of mitigation strategies for rail corrugation in metro lines

Rail corrugation appears as a periodic irregularity on the rail running surface that causes severe dynamic loads at the wheel-rail interface. These dynamic forces may generate ground-borne vibrations that propagate from the line to the surrounding buildings causing discomfort to residents. Rail grinding is the most used countermeasure for the mitigation of corrugation. However, this maintenance operation determines high operative costs if frequently performed and must be carefully scheduled. To this end, it is important to assess the effectiveness of other mitigation solutions that may prevent or slow down its growth. The main objective of this study is to investigate the formation of rail corrugation on a sharp curve of the Cityringen underground line in Copenhagen. A wheel-rail interaction model is developed in the frequency domain to identify the root causes of the problem on the specific curve and predict the corrugation wavelength. Once the accuracy of the model is tested against experimental observations on the reference curve, it is used to explore the effectiveness of different mitigation actions, such as the use of friction modifiers, the variation of the speed, track design and track gauge. The results indicate that friction modifiers and speed variation are the most effective measures.

The influence of elastic pads deterioration in the fastening system on the dynamic characteristics of the vehicle-turnout system

The deterioration of the elastic pads in the fastening system in high-speed turnout areas increases longitudinal stiffness irregularities along the track, posing potential hazards to wheel-rail impact and train running safety. This paper takes the frog area of No. 18 turnout as an example and constructs a vehicle-turnout rigid-flexible coupling model considering the detailed structure of the fastener elastic pads. By increasing the stiffness of the rubber pad under the tie plate to simulate the deterioration of the elastic pads in the turnout area, the study investigates the effects of deterioration location, degree, and number on the dynamic characteristics of the vehicle-turnout system, providing theoretical guidance for stiffness optimization and maintenance of the turnout area. The results indicate that: 1) the deterioration of the elastic pads significantly affects wheel-rail interaction and safety indicators, while having a minor effect on vehicle running stability; 2) the 95th sleeper (point rail with a top width of 60 mm) is identified as the most critical location for the deterioration of elastic pads; 3) comprehensively considering, the stiffness replacement limit for elastic pads in ballastless turnout areas can be set to twice the design stiffness, which is 50 kN/mm.

Sources for railway community noise modeling

For rail traffic, the wheel-rail interaction is one of the most important sources of noise, and is included in different ways in the noise calculation methods being used in Sweden today. However, if the rolling stock exhibit other noise sources it is not clear how they are handled by the different calculation methods. Recent measurements in Sweden of the newly refurbished 'X2' passenger trains indicate that cooling fan exhausts mounted high up on the driving unit radiate noise at levels corresponding to the wheel-rail noise at speeds of 200 km/h. The NMT96 calculation method currently used in Sweden represents the whole train as one line source per octave band, each placed at different heights. The newer Nord 2000 method, applies three sources at low heights for rolling noise and allows additional sources but without defining how to accommodate them. The Cnossos-EU method puts all potential exhaust and fan noise at the higher of two sources, at 4 m above the rail. None of the models define how to apply a source to just the locomotive as sound power is given per meter train or per rolling axis. The impact on noise exposure and mitigation is discussed in this paper.

Numerical simulation of the vibration response of the permafrost subgrade under harmonic irregularity in the Qinghai-Tibet Railway

Abstract Harmonic excitation can significantly increase the dynamic response of wheel-rail interactions when a train passes. In this study, based on the train-track vertical coupled dynamics model (ZL-TNTLM) and ABAQUS, a unified train-track-subgrade coupled dynamics model is established. Field measurement data corroborated its accuracy and reliability. The analysis focused on the dynamic response of the permafrost subgrade of the Qinghai-Tibet Railway (QTR) to harmonic excitation, including the track-sleeper force and vertical dynamic stress. This study examined the influences of the wavelength, wave depth, and railhead depression on the dynamic response of a subgrade. The results indicated that single-harmonic excitation amplifies the track-sleeper forces and the vertical dynamic stress in the subgrade, particularly near the harmonic centre. Additionally, axle load variations and seasonal thawing broaden the dynamic stress range on the subgrade, with harmonic excitation exacerbating this impact, thereby increasing the risk to the stability of the ice-rich permafrost layer. A decrease in wavelength and increase in wave depth result in a greater number of affected sleepers, intensifying the vertical vibrations of the subgrade, especially in the medium- and high-frequency ranges of vertical dynamic stress. Notably, wavelengths between 1 and 2 m significantly exacerbate the adverse effects on the ice-rich permafrost layer. Shorter wavelengths also induce higher-frequency vibrations. These findings offer valuable insights for the design, operation, and maintenance of permafrost subgrade systems under irregular excitation.

Dynamic responses of locomotive axle box bearings under varying operating conditions

Axle box bearings (ABBs) are a vital component of a railway locomotive, ensuring their reliable performance requires an in-depth understanding of their dynamic behaviour. This work theoretically derives a locomotive–track longitudinal–vertical coupled dynamics model that takes detailed dynamics of the ABBs into account. The model considers a number of complex interactions, such as non-linear contact and friction forces within the ABB, wheel–rail interactions, and track irregularities. The motions of ABB are coupled with the wheelset and bogie frame, allowing detailed investigation of the ABB dynamic behaviour during operation. The correctness of the proposed model is verified in both the time and frequency domains by comparing with field test. The dynamic characteristics of ABBs under varying operating conditions were comprehensively investigated. The results demonstrate that track irregularities have a non-negligible influence on the dynamic forces of the locomotive ABB. Furthermore, the axle load transfer occurs during loading conditions, which leads to significant differences in vertical and longitudinal dynamic interactions within the ABBs across wheelsets. It is clear that the operating conditions of the locomotive should be suitably considered in the dynamic assessment, operation, and maintenance of ABBs.

Evaluating the impact of rail surface roughness post-grinding: An experimental and elastoplastic modelling approach

Grinding is regularly conducted on railway tracks to prevent crack propagation and surface deterioration. However, grinding can introduce roughness on rail surfaces, potentially leading to stress and strain concentration that increase the likelihood of crack initiation. This paper proposes the utilization of surface roughness obtained by replicating the ground rail surface to assess its impact on train wheel-rail interactions. A novel approach which integrates the replicated roughness into an elastoplastic contact model, allows for a detailed assessment of its effects on contact pressure, and residual strain and stress distributions. The findings highlight the importance of considering surface roughness in predictive maintenance planning for railway infrastructure, as it can significantly influence the structural integrity and long-term performance of the track system.

Dynamic response of high-speed trains under uneven temperature fields of slab tracks on cable-stayed bridges

The temperature deformation of a long-span cable-stayed bridge (LSCSB) could significantly deteriorate the smoothness of rails, thereby affecting the dynamic behavior of high-speed trains (HSTs). In this paper, based on the thermal-fluid-structure coupling theory and vehicle-track coupling dynamics theory, an analysis method was proposed to explore the influence of temperature deformation of LSCSBs on the dynamic behavior of HSTs. The temperature deformation of LSCSBs within a day was analyzed, and the dynamic behavior of HSTs passing through the LSCSBs at different times was revealed. The results showed that on a summer day, the temperature deformation of LSCSBs varied significantly and rapidly, and the variation experienced a significant increase of 23.46% within just 2 h. Due to the influence of structural temperature deformation, the wheel-rail interaction, train safety, and passenger comfort changed noticeably. The construction temperature of the bridge and track decisively affected the dynamic behavior of the train. Therefore, it was crucial to construct the structure under suitable temperature conditions to prevent further exacerbation of the dynamic behavior of HSTs due to violent temperature differentials. In summary, the method proposed in this paper could contribute to a comprehensive and in-depth understanding of the operational characteristics of HSTs on LSCSBs.

The Noise Exposure of Urban Rail Transit Drivers: Hazard Classification, Assessment, and Mitigation Strategies

Prolonged exposure to high-intensity noise environments in urban rail transit systems can negatively impact the health and work efficiency of drivers. However, there is a lack of comprehensive understanding of the noise pattern and, therefore, effective mitigation strategies. To control the noise in urban rail transit systems, this study proposes a comprehensive noise assessment framework, including metrics such as average sound pressure level, peak sound pressure level, percentile sound pressure levels, dynamic range, main frequency component, and cumulative time energy to evaluate the noise characteristics. We also employ a density-based spatial clustering of applications with noise (DBSCAN) method to identify the noise patterns with the evaluation of their hazard to urban rail transit drivers. The results have revealed that: (1) The equivalent continuous sound pressure level (Leq) in the cab of Lanzhou Urban Rail Transit Line 1 averages 87.12 dB, with a standard deviation of 8.52 dB, which reveals a high noise intensity with substantial fluctuations. (2) Ten noise patterns were identified, with frequencies varying from 14.47 Hz to 69.70 Hz and Leq varying from 60 dB to 115 dB. (3) The major noise sources from these patterns are inferred to be the train’s mechanical systems, wheel–rail interaction, aerodynamic effects, and braking systems. Combined with the noise patterns and urban rail transit’s operation environment, this study proposes tailored mitigation strategies for applications aimed at protecting drivers’ hearing health, enhancing work efficiency, and ensuring driving safety.

Evolution Characteristics of Aluminum Thermal Weld Irregularity and Damage in Heavy-Haul Railway under Different Service Conditions

Aluminum thermal welding joints are widely used in the maintenance welding of heavy-haul railways due to their easy handling and high efficiency. However, due to their inherent welding characteristics, welding results in certain differences in the material’s physical properties at the welding zone compared to adjacent base materials, leading to the occurrence of short-wave irregularity under long-term wheel–rail interactive forces. In order to explore the evolution characteristics of weld irregularity, dynamic characteristics, and plastic deformation under long-term wheel–rail impact, a detailed tracking test was conducted on a normal aluminum weld, and the process from being put on the track to being damaged and replaced was evaluated. At the same time, a rigid–flexible coupling model was established for subsequent analysis, and plastic damage was analyzed using the finite element model. The results show that the service life of the weld can be divided into three different stages: the initial stage, the intermediate stage, and the damage stage. In the damage stage, a temporary separation occurred between the wheel and rail, leading to a sudden change in the wheel–rail interaction. The weight of 250 MT at the weld reached the repairment control limit. The concentration effect of equivalent plastic deformation was most serious at 2~5 mm below the rail head.

Investigation of the vibration isolation effect of composite vibration isolation walls on ground surface vibrations in deep tunnels of suburban railways

To investigate the vibration isolation effect of composite vibration isolation walls on surface vibrations in suburban railway deep tunnels under various influencing factors, an integrated numerical model of the train was initially developed. This model solved the wheel-rail interaction force and was applied to a three-dimensional volume coupling model of the track soil. Subsequently, the model's reliability was validated through comparison with measured data. Afterward, the vibration isolation effects of various types of EPS material vibration isolation walls were examined, with a focus on exploring the impact of thickness, material proportion, and relative positioning of the materials within the vibration isolation wall composed of EPS material and concrete. Research indicates that with an increase in the burial depth of a single material vibration isolation wall, its effective vibration isolation frequency range gradually widens. When the burial depth of the vibration isolation wall exceeds the tunnel burial depth, the vibration isolation effect is optimal. Composite vibration isolation walls, with thicknesses smaller than single-material vibration isolation walls, exhibit superior vibration isolation effects compared to their single-material counterparts. The effective vibration isolation frequency band of composite vibration isolation walls differs from that of single-material vibration isolation walls. Using the optimal-size vibration isolation wall of a single material as a composite vibration isolation wall enhances the vibration isolation effect of peak acceleration in the frequency domain by 16.58% and peak velocity by 16.95%. Moreover, frequency domain peak displacement experiences a 30.73% improvement in the vibration isolation effect.

Dynamic modelling and experimental validation of a dynamic track stabiliser vehicle–track spatially coupling dynamics system

A dynamic track stabiliser vehicle is an unconventional vehicle for maintaining the quality of ballasted tracks, and its dynamic performance has a significant impact on its working efficiency. For the first time, this paper proposes a comprehensive dynamic track stabiliser vehicle–track coupled vertical and lateral multi-body dynamics model based on classical vehicle–track coupling dynamics theory. In this model, detailed attention is given to the vertical, lateral, roll, yaw, and pitch motions of the components, including the vehicle body, bogies, wheelsets and stabilisers. The Shen–Hedrick–Elkins theory is employed to describe non-linear wheel–rail contact relationships between the bogie wheelsets and the rails, and three various methodologies are adopted to address complicated wheel–rail interaction problems between the stabiliser wheelsets and the rails. This comprehensive multi-body dynamics model enables a detailed investigation of the dynamic performance of the system under complex excitations, such as the lateral excitation of the stabilisers and vertical downward pressure exerted by hydraulic cylinders, especially the dynamic response of the stabilisers in the vibration environment of the complete vehicle. The dynamics model was fully validated by comparing its results with time- and frequency-domain data obtained from field tests. The results indicate that the model is capable of being used for analysis of the dynamic performance of dynamic track stabiliser vehicles.

Carbody sway behaviour of railway vehicles due to track irregularity from rail alternate side wear

AbstractTrack irregularity from rail alternate side wear is manifested as uneven rail wear waveforms alternating in the left and right rails with equal intervals, which will cause carbody sway behaviour of railway vehicles and greatly influences the passenger comfort. In this work, the carbody sway behaviour and mechanism due to track irregularity from rail alternate side wear and possible solutions to this issue were studied by the field testing and numerical calculation approaches. First, the carbody sway of an urban rail transit train is introduced with full-scale field tests, through which the rail alternate side wear is characterized and the formatted track irregularity are presented. Then, multibody vehicle dynamic models are developed to reproduce the carbody sway behaviour induced by the track irregularity from the rail alternate side wear. The creep forces acting on the wheel and rail are preliminarily discussed to study the influence of the carbody sway on the wear of the wheel flange and the rail corner. Finally, some potential solutions, e.g. improving the damping ratio of carbody rigid mode and rail grinding, are proposed to relieve this issue. It is concluded that an increased damping ratio of the carbody mode can alleviate the carbody sway and wheel–rail interactions, while properly maintaining track conditions can improve the vehicle performance.

Rail crack identification of in-service turnout through Bayesian inference

In-service railway turnout, suffering from multi-factor coupling of operational and environmental loadings and special wheel–rail interaction, is prone to structural damage. The paper aims to develop a Bayesian damage identification method for crack-alike damage of the turnout rail under uncertainties. It consists of three core parts, including a damage index (DI) constructed by the transformation of time–frequency components of responses for generating damage-sensitive relationships, Bayesian models describing the crack-sensitive relationships hidden in the members of the damage index, and a mechanism synthesizing individual assessment results associated with the different reference models for providing one quantitative solution. The abnormal change in the stable relationships derived from the index can reflect damage occurrence and severity. The Bayesian approach is adopted to model the relationships under uncertainties of in-service railway turnout. The models trained by using monitoring data of the turnout rail before being damaged serve as a reference for healthy state, and deviations of actual observations from model predictions may indicate the existence of damage. The synthesizing process helps to offer a more rational assessment result through the weighted summation of individual quantitative assessment results. Rail monitoring data of a railway turnout are acquired to examine the damage detection performance of the proposed method. By exempting loadings measurement and physical model derivation, this data-driven methodology is potentially capable of supporting the damage identification and quantitative assessment of other structures in railway engineering.

Dynamic characteristics of electromechanical coupling of body-suspended drive system for high-speed trains under wheel polygonal wear

Wheel polygonal wear can trigger intense wheel–rail interactions in railway vehicles, posing a significant threat to traffic safety. However, the mechanism and interaction of the influence of wheel polygonal wear on the electromechanical coupling characteristics of high-speed trains remain unclear. Therefore, this paper proposes a joint simulation modelling method that takes into account the integration of the electrical subsystem with the complete mechanical subsystem. A comprehensive analysis is conducted on the dynamic response of the high-speed train’s body-suspended drive system under a wide range of frequency excitations arising from harmonic torque, gear meshing, and wheel polygon wear. The results indicate that the electrical system generates a substantial amount of harmonic frequency components, resulting in a significant increase in the vibration of the train. The wheel polygon wear causes a broadening of the low-frequency resonance band, revealing a relatively prominent observation interval for the dynamic characteristics. Concurrently, it is discovered that the 23rd-order wheel polygon wear excites the system’s resonance frequency, and as the wavelength of the wheel polygon increases, the acceleration vibrations intensify progressively. Research reveals first the interaction of electrical system and mechanical system under wheel polygon wear, especially in the resonance gain characteristics under polygons and harmonic torques.

Impact of Train Formation on the Dynamic Responses and Operational Safety of High-Speed Trains under Non-Uniform Seismic Ground Motion

The study of dynamic responses and operational safety of high-speed trains under seismic excitation has increasingly relied on numerical simulation as the most effective and convenient research approach. The majority of studies only focus on single-car formation, and fewer utilize train models with actual standard formation, inevitably resulting in differences in dynamic characteristics of train models and simulation results. Furthermore, trains also have different standard formations in different countries and operating scenarios. Therefore, the influences of train formation on the dynamic responses and operational safety of trains under seismic action are investigated. Hence, a detailed train/vehicle–track coupled dynamics model was established to simulate trains under non-uniform seismic ground motion. Moreover, due to wheel–rail contact simulation being the key factor constraining simulation efficiency, based on the influence pattern of train formation, whether fewer train formations can achieve the same simulation accuracy as the 8-car standard formation is also explored in this paper considering seismic wave propagation effect. Results indicate that variation in train formation can influence the dynamic responses of a coupled system significantly from both the perspective of wheel–rail interaction and vehicle kinematic responses. Moreover, the 5-car formation model can better meet the accuracy requirement and significantly improve computational efficiency compared to 8-car formation model.

The low-frequency bandgap characteristics of phononic crystal isolators with multi-hole

A vibration isolator for a floating slab track, based on a locally resonant phononic crystal, has been designed to suppress vibrations caused by the wheel-rail interaction. In this isolator, a circular vibrator is connected to a connector through a rubber layer uniformly embedded in holes. The finite element method is utilized to compute the energy band structure and transmission loss of the vibration isolator, while the mechanism of bandgap is elucidated through the analysis of modes. The static stiffness and dynamic stiffness of the vibration isolator are calculated, which proves that the vibration isolator meets the requirements of engineering applications. The influence of the number of circular holes and the geometric parameters of the vibration isolator on the bandgap is examined. It is discovered that augmenting the number of holes and the hole diameter in the rubber layer leads to a decreased bandgap. A low-frequency locally resonant bandgap of 38.2–97.1 Hz and a relative bandgap bandwidth of 86.9 % are obtained by optimizing the vibration isolator. The vibration isolation performance of a floating slab track equipped with vibration isolators is analyzed and more robust vibration attenuation performance is obtained in the bandgap. The multi-hole phononic crystal vibration isolator is employed in floating slab tracks for rail transportation, effectively mitigating vibrations transmitted to tunnels, thus further minimizing the effects on the surrounding environment.

Research on the influence of random stiffness of the rubber tie plate on the coupled vehicle-turnout system based on the probability density evolution method

Track supporting stiffness plays a crucial role in the running quality of a vehicle crossing through a turnout. This paper mainly focuses on the influence of random stiffness of the rubber tie plate on the vehicle-turnout coupling system. The relevant random field is constructed via the number theoretical method (NTM). The coupled vehicle-turnout model with flexible rails is built via the modal superposition method. The probability density function (PDF) is obtained via the probability density evolution method (PDEM). Cases of normal distributions with various mean values of stiffness are compared to contrast the relevant impact on the dynamic wheel–rail interaction. Research results indicate that an increase of the stiffness of the rubber tie plate can abate the transverse sway of the vehicle and low down the wheel number. The target stiffness should be taken as 35 kN/mm and corresponding normal distribution with a confidence interval of plus and minus 5 kN/mm can be accepted. The discrepancy between the mean value and the relevant PDF contour clarify the importance and necessity for analysis of randomness. Research results of this paper can serve as the theoretical fundament of the track stiffness homogenisation of a turnout in the future.