Wheel Rail Research Articles

Comparative Study of Wheel–Rail Contact Impact Force for Jointed Rail and Continuous Welded Rail on Light-Rail Transit

In this study, the measured track impact factor induced by the wheel–rail contact impact force of each test section (two continuous welded rails on slab tracks and rail joint on a ballasted track) was compared with the design track impact factor under service conditions of a curved light-rail transit system. The measured track impact factor (TIF) was estimated from the measured dynamic wheel load and vertical rail displacement at each test section. In the case of the rail joint section, the rail joint was found to directly affect the track impact factor. Moreover, the dynamic wheel load fluctuation and vertical rail displacement were found to be significantly greater than those of the continuous welded rails (CWRs) on slab tracks. In addition, vertical rail displacements were measured by field measurement and finite element analysis (FEA) was conducted to simulate dynamic wheel load on the jointed rail. Using the field measurements, the rate of dynamic wheel load fluctuation and the TIF were calculated for the CWR and rail joint sections. Subsequently, the calculated TIF values were analytically validated through a comparison with the measured vertical rail displacement, the results of FEA, and the designed TIF for rail joints and CWRs. Finally, the TIF measured by field measurement was compared with the result predicted by FEA. The difference between the results of field measurements and FEA for vertical rail displacement was within approximately 4%.

STABILITY OF FREIGHT CARS UNDER THE ACTION OF COMPRESSIVE LONGITUDINAL FORCES

Purpose. The aim of the work is: a theoretical study of the car movement stability when exposed to longitudinal forces of a quasistatic nature; determination of analytical for estimating the longitudinal loading of cars in trains; the influence analysis of simultaneous action of certain factors on the value of longitudinal forces, at which the car movement stability is still preserved. Methodology. Assessment of the freight car stability when moving at different speeds along curved track sections was investigated using the analytical method. The most unfavorable schemes for applying compressive longitudinal forces in a vertical and horizontal plane are considered. Findings. Expressions are obtained for calculating the value of the car lift resistance coefficient by the longitudinal compressive force acting on the car as part of a freight train. The calculations were carried out in an empty and loaded state with a transverse run-up of the car body frame relative to the track axis in a guiding section of 50 mm in a curve of small radius taking into account the inertia forces from the unbalanced acceleration. Originality. In a theoretical study, the effect on the movement stability of quasistatic longitudinal compressive forces depending on the change in speed and the force value, as well as the effect of friction forces at the contact point of the wheel flange and rail and the eccentricity of fastening the tail of the automatic coupler, are considered. The influence of longitudinal compressive forces on the stability of freight rolling stock when moving in a curve of small radius with speeds up to a design value of 120 km/h is investigated. Practical value. The application of the results obtained by the above method will help to increase the stability of the freight rolling stock, which in turn will allow increasing the technical speed of train movement by removing some existing limits of permissible speeds. Using the described methodology for determining the car lift resistance coefficient will allow justifying the cause of wheel derailment, as well as to develop and put into practice the technical measures to prevent the lift of carriages, thrusts and shears of the track.

Influence of the temperature- and frequency-dependent dynamic properties of rail pads on the vibration characteristics of rails at low temperature

The dynamic properties of railway tracks and rail pads are significant for accurately predicting both the wheel–rail system vibration and rolling noise. The effect that the dynamic properties of rail pads have on the dynamic characteristics of railway tracks at extremely low temperatures was not adequately studied in previous research. In order to better predict the attenuation of the rail vibration, the viscoelastic dynamic properties of rail pads varying nonlinearly with temperature and frequency were first tested, in a wide temperature range (−60 ℃ to 20 ℃), and represented by the fractional derivative Zener model. Then, rail vibration and its attenuation characteristics were investigated by accounting for the frequency-dependent, temperature-dependent and frequency- and temperature-dependent properties, respectively. To be more specific, the frequency and amplitude of the rail first-order bending resonance and pinned–pinned resonance, as well as the rail decay rate were analyzed for the three cases. In conclusion, the study shows that the temperature/frequency-dependent properties of the rail pad have a significant effect on the first-order bending resonance of the rail, but no influence on the pinned–pinned resonance frequency. The rail decay rate indicates a clear increasing trend in the entire frequency domain with the decrease of temperature (especially below about −20 ℃). The frequency dependence mainly affects the vibration and its attenuation characteristics of the rail below about 400 Hz, which should not be ignored in the track dynamics modelling. Therefore, when the analyzed environmental temperature is below −20 ℃, the temperature dependence of rail pads should be considered.

Fine interrelation between track irregularities and vehicle responses: multi-scale time-dependent correlation analysis

Track irregularities are perhaps the main excitations of vehicle–track systems and cause dynamic wheel–rail responses, but track irregularities and vehicle responses do not always correspond to each other. In this study, the interrelations between track irregularities and vehicle responses in a multi-scale framework were investigated using measured data. Firstly, the track irregularity and vehicle response data were separated into modes on different time scales using multivariate empirical mode decomposition, and the energy distribution of each wavelength component was determined. Then, the local correlations between irregularity–response mode pairs were examined via time-dependent intrinsic correlation (TDIC) analysis. The irregularity–response interrelation was not always unique, but rather varied in both time scale and time domain, and positive–negative correlation reversals frequently occurred, causing a low overall correlation and coherence. TDIC analysis can elucidate the wavelengths and positions of track irregularities that affect vehicle responses.

Locomotive wheel polygonisation due to discrete irregularities: simulation and mechanism

Discrete irregularities are a common issue occurring on locomotive wheels. The wheel roughness measured in the field sites indicates that some wheels suffer from discrete wheel irregularities, such as wheel flats or local defect. Meanwhile, the wheels exhibit obvious polygonisation. A wheel wear model is present to study the influence of discrete wheel irregularities on locomotive wheel polygonisation, which consists of a flexible-rigid locomotive-track coupled dynamics model and a wear calculation model based on the frictional work of wheel–rail contact patch. A series of discrete irregularities with different wavelengths are taken as initial input of irregularities. The wheel–rail interaction and wheel polygonisation evolution process induced by discrete wheel irregularities are analysed. The simulation results indicate that discrete wheel irregularities can excite the structural elastic vibration of the wheelset, especially the wheel lateral vibration, which leads to oscillations of the lateral creepage and creep force in a certain frequency. Wheel polygonisation is formed finally resulting from the fluctuation of wheel–rail creepages and creep forces. The frequency-fixing mechanism of wheel polygonisation with wavelengths of 630 and 200 mm in 1/3 octave band are the coupling of parameter excitation of discrete sleeper support with P2 resonance and lower bending resonance of the wheelset, respectively.

Numerical simulation of rail surface-initiated rolling contact fatigue in the switch panel of railway turnouts

Considering the complex characteristics of the track structure in railway turnouts, it is difficult and also expensive to experimentally study rail damages; therefore, numerical methods are an effective alternative. This study presents a numerical method to simulate rail surface-initiated rolling contact fatigue in the switch panel of railway turnouts. This method includes simulation of the vehicle–turnout wheel–rail dynamic interaction, analysis of the wheel–rail multipoint non-Hertzian rolling contact that considers the relative motion between the switch and stock rails, and calculation of the accumulated rail surface-initiated rolling contact fatigue. The accumulated rail surface-initiated rolling contact fatigue after the vehicles passed a turnout switch panel 80 times (the average number of vehicles running on the Chinese high-speed railway lines per day) in the through route with facing move was simulated based on this procedure. The result showed that the maximum surface-initiated rolling contact fatigue damage of the switch rail and the stock rail was 1.57 × 10−2 and 0.62 × 10−2, respectively. Surface-initiated rolling contact fatigue in the switch rail mainly occurred at the gauge angle, and in the stock rail it mainly occurred at the center of the rail. In addition, the influence of track parameters (rail inclination, track gauge, and friction coefficient) is analyzed. The friction coefficient influenced the rail surface-initiated rolling contact fatigue. When the coefficient exceeded 0.3 in particular, the rail rolling contact fatigue damage increased sharply. Hence, suitable friction control measures should be taken during rail maintenance in order to mitigate the rail surface-initiated rolling contact fatigue damage, e.g. by keeping the wheel–rail friction coefficient below 0.3.

Research on Hunting Instability Monitoring System of High Speed Freight Bogie

High speed freight trains have become a new trend in international train operation, and many countries have studied the high speed freight trains. Therefore, it is necessary to carry out relevant safety monitoring research on high speed freight trains. According to the existing acceleration alarm devices for high speed trains and normal speed trains, and combined with the reality condition of high speed freight train, an empty train hunting alarm device is proposed. Through the simulation analysis of the hunting wavelength and acceleration of freight car, it is proposed that the wave filtering frequency should be controlled at 0-15Hz, and the recommended value of lateral alarm limit of frame lateral acceleration is 0.6g. Finally, the suggestion of axle box acceleration installation is put forward, which is installed in the middle position above the axle box to evaluate the wheel rail state. It can mainly evaluate the common wheel rail damage such as wheel polygon, wheel flat and corrugation of rail.

Study on fatigue of subway antenna beam

The dynamic fatigue life theory starts very late. As an important part of the subway, the antenna beam has played a great important role on the daily life of people. To study the fatigue properties of it, the relative researches are carried out. The finite element model is set up first. Then the mode analysis is carried out. After that, the rigid-flexible coupling dynamic model is set up. Finally, the reduction analysis continued. Through the experiment and simulation, the fatigue strength and vibration transition properties are analysed. Ploymax method is carried out for modal parameter identification, then the FE model could be verified to improve the accuracy. By setting up the rigid-flexible coupling dynamic model of the subway vehicle, then the modal parameters and experimental data are compared, the model is modified and verified. Considering the impact of wheel flat scar and rail gap, the vibration transmission characteristics of bogie system are studied. In the calculation of resonance fatigue dynamic stress, FFT method is used to solve the problem. The fatigue strength of antenna beam caused by the impact of rail gap and wheel flat scar is studied, and the requirements for safe service life of antenna beam is put forward.

Parallel co-simulation of locomotive wheel wear and rolling contact fatigue in a heavy haul train operational environment

Locomotive wheel wear and rolling contact fatigue simulations that consider both train dynamics and detailed traction control systems have not been reported. This paper developed a parallel co-simulation method to link an in-house longitudinal train dynamics simulator to a commercial software package named GENSYS. An advanced longitudinal train dynamics model, a traction control system model and a wheel–rail contact model were then incorporated into the simulation. Three wear calculation models (T-gamma model, USFD model and Archard model) and two rolling contact fatigue calculation models (T-gamma-based rolling contact fatigue model and shakedown-based rolling contact fatigue model) were implemented. A train with the configuration of 1 locomotive +54 wagons +1 locomotive +54 wagons was simulated. This paper shows that the simulation method is successful and can be used for such more detailed locomotive wheel wear and rolling contact fatigue calculations. Wear and rolling contact fatigue calculation results show that the wear numbers that were calculated using the T-gamma wear model and damage indexes that were calculated using the T-gamma-based rolling contact fatigue model were similar between the leading and remote locomotives. However, wear rates that were calculated using the USFD wear model, wear volumes that were calculated using the Archard model and fatigue indexes that were calculated using the shakedown-based rolling contact fatigue model have evident differences between the leading and remote locomotives. Maximum differences in these results were about 12, 18 and 34%, respectively.

Experimental Investigations on the Effects of Fatigue Crack in Urban Metro Welded Bogie Frame

The welded bogie frame is the critical safety part of the urban metro vehicle. This paper focuses on finding out the factors inducing the fatigue cracks initiated from the positioning block weld toe of metro bogie frame. Fracture morphology and metallographic analysis were conducted to identify the failure modes, and on-track tests about the dynamic stress at the positioning block weld toe and vibration acceleration were performed. The typical signals of dynamic stress and acceleration were analyzed from time and frequency domain. The relationship between wheel polygon, rail corrugation, running speed and dynamic stress in amplitude and frequency are investigated in details. Research results show that the micro cracks induced by welding at the weld toe of positioning block propagate to the spring sleeve under relatively high alternating dynamic stress, which is strongly influenced by the wheel polygon, rail corrugation and the train running speed.

Thermo-mechanical analysis of train wheel-rail contact using a novel finite-element model

PurposeThe purpose of this paper is to develop a novel method for analyzing wheel-rail (W-R) contact using thermo-mechanical measurements and study the effects of heating on the characteristics of W-R contact under different creepages.Design/methodology/approachThis study developed an implicit-explicit finite element (FE) model which could solve both partial slip and full sliding problems by setting different angular velocities on the wheels. Based on the model, four material types under six different creepages were simulated.FindingsThe results showed that frictional heating significantly affected the residual stress distribution under large creepage conditions. As creepage increased, the temperature of the wheel tread and rail head rose and the peak value was located at the trailing edge of the contact patch.Originality/valueThe proposed FE model could reduce computational time and thus cost to about one-third of the amount commonly found in previous literature. Compared to other studies, these results are in good agreement and offer a reasonable alternative method for analyzing W-R contact under various conditions.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2019-0298

Generation of airborne wear particles from the wheel–rail contact under wet conditions using a twin-disk rig

Electrical railways produce airborne wear particles (AWPs) in significant amounts from wheel–rail contact. Herein, the effects of wet conditions on the AWPs released from the wheel–rail contact under different normal loads were investigated using a twin-disk rig. A fast mobility particle sizer and an optical particle sizer were used to measure number concentrations (NCs) of AWPs. Analyses of NCs and particle size distribution were conducted. The findings suggest that significantly fewer AWPs are generated under wet conditions than under dry conditions. Marked differences were also seen in the size distribution peaks between wet and dry conditions: under dry conditions, the largest peak corresponded to fine particles, whereas under wet conditions, the largest peak corresponded to ultrafine particles. The generation trends of AWPs were different for dry and wet conditions: AWPs increased and then decreased after maximal NCs under dry condition; however, they increased and then remained nearly constant under wet conditions. The total amount of ultrafine, fine, and coarse particles increased with normal load under wet conditions, indicating that AWP generation is significantly influenced by the normal load. Furthermore, water can significantly reduce the amount of ultrafine, fine, and coarse particles generated from the wheel–rail contact.

Wheel–rail adhesion during torsional vibration of driven railway wheelsets

Stability verification of railway wheelsets in Germany can currently become a process difficult to plan. Besides standardised calculations, expensive and often time-consuming test ride measurements have to be conducted. In particular, determining the maximum dynamic torsional stresses resulting from torsional vibration of wheelsets is a frequently discussed topic. Neither an analytical nor an empirical model has been found yet to predict the named stresses. Actually, they are determined experimentally and the representativeness of the recorded maximum dynamic torque is assured statistically. However, statistical evaluation only deals with axle stresses (torque and bending) itself. The origin of torsional vibration, which is the wheel–rail contact point, is not considered for evaluation. Its conditions are typically described by wheel–rail adhesion characteristics, but normally the necessary quantities describing these characteristics are not measured or not measured in sufficient precision. Therefore, this article analyses high-resolution wheel–rail adhesion data that have been recorded additionally on regular test ride measurements. The analysis of these measurement data leads to the following two correlations: (1) Torsional vibration events occur at a certain ratio of adhesion change and slippage change. (2) Dynamic torque swings up within a characteristic time span.

Life cycle cost analysis for the top-of-rail friction-modifier application: A case study from the Swedish iron ore line

The application of top-of-rail friction modifiers (TOR-FMs) is claimed by their manufacturers as a well-established technique for minimising the damages in the wheel–rail interface. There are various methods for applying friction modifiers at the wheel–rail interface, among which stationary wayside systems are recommended by TOR-FM manufacturers when a distance of a few kilometres is to be covered. An on-board system is recommended when an area of many kilometres has to be covered and focus is more on particular trains. Trafikverket in Sweden is considering the implementation of the TOR-FM technology on the iron ore line. Directly implementing such technology can be inappropriate and expensive, because the life cycle cost of a TOR-FM system has never been assessed for the conditions of the iron ore line. In the present study, the life cycle cost is calculated for wayside and on-board application systems, by taking inputs from the research performed on iron ore line. The present research has taken the iron ore line as a case study, but the results will be applicable to other infrastructure with similar conditions. The results have shown that the wayside equipment is economically unfeasible for the iron ore line. In this case, the life cycle cost increases by 4% when the friction modifier is applied on all curves with a radius smaller than 550 m and by 19% when the friction modifier is applied on all curves with a radius smaller than 850 m. The on-board system used in this study is shown to be economically feasible, as it has a significantly lower operation and maintenance cost than the wayside equipment. The reduction in the maintenance (grinding and rail replacement) cost when the cost of the friction modifier application is added is 27% when the friction modifier is applied on curves with a radius smaller than 550 m and 23% when the friction modifier is applied on curves with a radius smaller than 850 m.

Computational fluid dynamics–discrete element method simulation of locomotive sanders

Locomotive sanders are used to optimize the traction between the train wheels and the railhead by spraying sand into the interface. It has been previously shown that a large fraction of sand sprayed by the sanders does not make it through the wheel–rail nip, leading to sand wastage and thereby increasing the cost and refilling effort. In this study, pneumatic conveying of sand through the wheel–rail nip is numerically modeled through coupled computational fluid dynamics and discrete element method simulations. The gas phase, discrete phase, and coupled two-phase flows are separately validated against the literature, and the parameters affecting the deposition of sand into the nip are analyzed to determine their impact on sander efficiency. The aerodynamics associated with the particle-laden jet play a critical role in optimizing the amount of sand going through the wheel–rail interface, with the particle velocities being directly correlated with the sander efficiency. Particle–geometry interactions (e.g. particle bouncing) are found to have a negligible effect on the deposition. In the absence of crosswinds, it is recommended to employ particles with a smaller Stokes number to enhance the sander efficiency. A larger airflow rate through the nozzle is also recommended. Crosswinds strongly and adversely affect sander efficiency. The effects of crosswinds can be mitigated by reducing the nip–nozzle distance and using coarser particles.

Complex vibration analysis of railway vehicle with tread conicity variation

This paper investigates the influence of tread conicity variation on hunting dynamical changing features for railway vehicle. Nonlinear contact force between wheels and rail is estimated by Vermeulen–Johnson creep force law. And a piecewise linear function is employed to appropriate the collision between wheel flange and rail. Hunting asymmetrical motions are analyzed by lateral bifurcation behaviors between maximum and minimum of car body lateral displacement. The result shows that the critical speed decreases with the increase in tread conicity, while the speed gap between linear and nonlinear speeds is narrowing. Compared with wheelsets, lateral amplitudes of the bogies are vulnerable to the tread conicity and decrease gradually. Besides, more asymmetrical motions are put into consideration with regard to tread conicity variation. Similarly, one asymmetrical behavior with small amplitude difference originates from the same chaotic attractor at both sides. And small interactive amplitude jumps in two sides at chaotic or periodic occasions are revealed. Distinguishingly, the other new asymmetrical type is found at a certain tread conicity that amplitudes of the hunting motion in positive and reverse directions no longer coincide and go away in opposite directions when the tread conicity increases to a certain value. And this particular asymmetrical motion disappears with further growth of tread conicity.

Coupled dynamic behaviour of a transmission system with gear eccentricities for a high-speed train

The transmission system of a motor car directly affects the operating reliability and running safety of a high-speed train. This study examines the coupled torsion vibration responses of a transmission system in a vehicle–track vibration environment. It considers the time-varying mesh stiffness, nonlinear damping characteristics, wheel flexible deformation and wheel–rail interactions. The results are compared to those of previous works as a means of validation. Then, the dynamic characteristics of the transmission system and its coupling effects are investigated along with gear eccentricity, which describes the torsional vibration properties in the vehicle–track coupled system more comprehensively. The results show that the traction torque and gear eccentricity affect the gear meshing, vibration amplitudes and frequency multiplication of the transmission system during the vehicle acceleration process. The eccentricity, especially of the pinion, has a great effect on vibration in the transmission system at high-speed ranges. Also, the dynamic responses of the wheels of the same motor car wheelset are different under traction conditions, which should not be neglected when assessing the torsional dynamic performance. The model provides a useful source of reference for the design and condition monitoring of traction systems for high-speed trains.

Numerical prediction of rail wear development in high-speed railway turnouts

Wear of rails in turnouts is a common problem during the operation of high-speed railways. It can seriously affect the running safety of trains and the service lives of wheels and turnout rails. In this study, a numerical prediction model for rail wear development in high-speed railway turnouts was established. According to the material wear theory developed by Archard, the wear depth distribution in the wheel–rail contact patch was calculated based on a vehicle–turnout coupling dynamics simulation and wheel–rail rolling contact analysis. For the dynamics model, various components of the vehicle and complex nonlinear interactions between the components were simulated in detail to guarantee consistency with reality. The combination relationship of the switch and stock rails and the irregular and variable cross-sections of the rails in the switch panel of the turnout were considered. Spatial interpolation was used to achieve three-dimensional transitions between adjacent irregular cross-sections to model the compromised rails in the turnout. In addition, the stiffness and damping characteristics of the track in the turnout zone were taken into account. The rail wear rates for every characteristic section of the switch panel were calculated by the superposition model for rail profile wear. An adaptive-step algorithm was adopted in the iterative computations to update the rail profiles for every characteristic section position, which could reduce the cumulative errors and effectively improve the stability and reliability of the numerical model. Finally, case studies were conducted to investigate the wear developments of the switch and stock rails of high-speed turnouts using the developed model. In addition, the rail wear status of turnouts in the Shanghai–Nanjing high-speed railway was measured. The numerical prediction results are consistent with those of the actual situations in the field, verifying the rationality of the established model. This work shows the potential for guiding the maintenance and optimal design of turnouts and improving the understanding of the formation mechanism and influencing factors of rail wear in turnouts.

Study on the Origin of Rail Corrugation at a Long Downhill Braking Section Based on Friction-Excited Oscillation

This article studies a special rail corrugation phenomenon occurring at a braking section of Shenzhen Metro Line 3 based on friction-excited oscillation. The rail corrugation is strongly related to the braking operation: when the braking operation was canceled, the corrugation did not appear again after being ground. In this article, a new viewpoint that the corrugation originates from the unstable vibration of the wheel–rail–brake shoe braking system is put forward. To test this point of view, a finite element model composed of two wheelsets with a brake shoe braking system and two rails for complex modal analysis was established. Parameter sensitivity analysis was carried out to develop some measures to suppress rail corrugation. The results show that rail corrugation at the long downhill braking section originates from the unstable vibration at about 430 Hz of the wheel–rail–brake shoe braking system. The corrugation wavelength predicted by the finite model is about 55 mm, which shows good agreement with the on-site data. The results of parameter sensitivity analysis show that the influence of the coverage angle of the brake shoe on the rail corrugation is significant. The possibility of the rail corrugation and its progression speed increase significantly with a decrease in the coverage angle of the brake shoe. To suppress the rail corrugation, the coverage angle should not be less than 48° when designing the brake shoe structure. The influence of the installation position of the brake shoe on the rail corrugation is also obvious. The position of the brake shoe with a pressure angle of 8° can restrain rail corrugation to the greatest extent. The contact state between the brake shoe and wheel tread has little influence on rail corrugation. In practice, the brake shoe should be in full contact with the tread.

Vehicle–track interaction with consideration of rail irregularities at three-dimensional space

Modelling of vehicle–track interaction has long been a hot and interesting topic. In multibody dynamics based on force-equilibrium methods, Hertzian contact and creep theories have been applied in vehicle–track model constructions. In another aspect, the complementarity-based methods have also been widely used in establishing vehicle–track interaction, but still having drawbacks on characterization of wheel–rail contact geometry/creepage in three-dimensional space. In this study, we draw essences from methodologies of refined wheel–rail coupling models and energy-variational principle, and a model for vehicle–track three-dimensional interactions with inclusion of rail irregularity excitations is newly developed. This model possesses high accuracy compared with Hertzian contact, FastSim, and vehicle–track coupled model in the middle-low frequency domain, and also, the advantages in computational stability are possessed. In this model, the unevenness of rail irregularities at the three-dimensional space is preliminarily considered by taking a hypothesis of normal distribution and accordingly, the wheel–rail three-dimensional constraint equations are presented. Extensively, a series of numerical examples are shown to verify the effectiveness and engineering practicability of this model. Besides, the influence of rail three-dimensional irregularities on the dynamic performance of vehicle–track systems is further explored, which shows when the trochoid of the wheel–rail contact points changes rapidly, the additional inertial effects brought out by rail irregularities might exert great influence on wheel–rail forces.