Wheel Rail Research Articles

Efficient time–frequency approach for prediction of subway train-induced tunnel and ground vibrations

In this paper, an efficient time–frequency approach is presented for the prediction of subway train-induced tunnel and ground vibrations. The proposed approach involves two steps. In the first step, a time domain simulation of the vehicle–track subsystem is used to determine the track–tunnel interaction forces and, in the second step, the resulting forces are then applied to a 2.5 D FEM–PML model of the tunnel–soil system. There are two main aspects to the novelty and contribution of this work: First, the errors of the linearized Hertzian wheel–rail contact models in the calculation of the track–tunnel interaction forces are quantified by a comparison with the nonlinear Hertzian contact model. The results show that the relative errors are less than 2%. Second, an efficient time–frequency analysis framework is proposed, including the use of a strongly coupled model in the time domain solution and a 2.5 D FEM–PML model in the frequency–wavenumber domain solution. Finally, the accuracy and efficiency of the proposed approach are verified by comparison with a time-dependent 3 D approach, where three types of soil, i.e. soft, medium, and hard, are considered.

Parametric Study of Track Support Structure to Minimize the Occurrence Possibility of Rail Corrugation

Changing the track support structure is an effective method to suppress or eliminate rail corrugation in practical engineering. Rail corrugation on small-radius curves with booted short sleepers is the main research object in the present paper. A relevant finite element model of the wheelset-track system supported by booted short sleepers is built combined with the dynamic analysis of the vehicle-track system. The effects of various parameters of booted short sleeper structure on the wheel–rail friction-induced vibration are investigated by complex eigenvalue analysis. Considering the interaction of multiple parameters in the booted short sleeper structure, the multi-parameter fitting equation forecasting the possibility of rail corrugation is obtained using the least squares algorithm. Results show that wheel–rail friction-induced oscillation is a contributing factor in the formation of rail corrugation. Controlling wheel–rail friction-induced oscillation with a frequency of about 300 Hz is beneficial to suppress the possibility of rail corrugation in sections with booted short sleepers. Lower fastener stiffness or greater vertical fastener damping make it less likely that rail corrugation will occur. Rail corrugation is not generated when the vertical stiffness of the fastener is controlled below 20 MN/m in the booted short sleeper.

A 3-D numerical simulation of fatigue crack growth in an alumino thermite welded UIC60 rail joint under different loading conditions

In this article, a UIC60 rail AT weldment with appropriate rail and weld geometry on two-parent rail tracks as per Indian Railways is analysed separately under vertical and lateral loads, applying FEM. Stresses in an alumino-thermite welded rail is measured using finite element analysis. The results of operating condition on the development of fatigue cracks in rail welds are investigated. A 3-D elastoplastic material basis analysis has performed on a CAD assembly model for this purpose. A wheel-rail track model is used to simulate for the allocation of high stresses field in the weldment on the rail under intense service conditions for the welded straight track. Damage mechanics approaches are also used to assess the stress allocation on weld and wheel interaction along with the influence on fatigue lifecycle. The crack's variables like of displacement and stress intensity factors (SIFs) are calculated at crack tip in finite element model to measure crack propagation patterns and the rate of growth, considering two crack and its comparison for different modes. Also the trapped fluid condition due to weather and its influence on crack has been discussed. As friction rate of the contact area between rail weld and wheels increases, formation of crack 1 initiates, and the growth of crack-2 accelerates. Friction of contact patch and the fracture surface have opposite effects on fatigue life. Wet-lubrication are useful for crack friction reduction and can be used as a catalytic factor for SIF on mode II, but this liquid may flow into crack-1 and creates wedge effect. The SIF of opening mode in crack-1 abruptly rises as a result the crack's spread-up, and the fracture becomes deeper. Increasing friction force reduces slip on the fracture crack surfaces, thus reduction in crack propagation. Fracture mechanics fundamentals are used to find the growth of fatigue cracks in weld zone. To measure the progress rate of fatigue crack and SIFs, updated Paris model is used with ANSYS academic.

Reducing the nanoparticles generated at the wheel\u2013rail contact by applying tap water lubricant at subway train operational velocities

The formation characteristics and the reduction of nanoparticles emitted from wheel–rail contacts at subway-train velocities of 73, 90, and 113 km/h under dry and water-lubricated conditions (using tap water) were studied using a twin-disk rig. The resulting number concentration (NC) of ultrafine and fine particles increased with train velocity under both conditions. Particle generation varied with slip rate under both conditions in both the particle categories. Furthermore, the formation characteristics at 113 km/h under dry conditions showed a notable deviation from those under water-lubricated conditions in three aspects: (i) The maximum NC of ultrafine particles was higher than that of fine particles, (ii) the predominant peak diameter was in the ultrafine particles category, and (iii) the proportion of ultrafine particles was much higher than those of the fine particles. Applying water decreased the NC of ultrafine and fine particles significantly at all tested velocities (by 54–69% and 87–91%, respectively). Adding water increased the NC of particles ≤ 35 nm in diameter, possibly owing to the increase in water vapor and mineral crystals from tap water. Overall, this study provides a reference for researchers aiming to minimize nanoparticle formation at the wheel–rail contacts by applying a lubricant.

Failure analysis and fatigue life prediction of high-speed rail clips based on DIC technique

With the development of rail transportation, the fatigue failure of rail clips has become an issue, which affects the operational safety of trains. In this study, reasons for the fatigue failure of rail clips were investigated to improve their service life. A digital image correlation (DIC) technique was conducted to obtain strain fields, vibration modes, and natural frequencies of a rail clip. The strain and displacement of a rail clip under dynamic cyclic loading were also obtained. A fastener system refinement model was developed to analyze the static, dynamic, and modal responses of the clip. The experimental tests and modal simulation results were mutually verified. The fatigue life was analyzed based on the verified FE model. The results revealed that the maximum strain and minimum fatigue life occur at the heel of the clip, in good agreement with the actual fracture position. As the amplitude and frequency of dynamic cyclic load increased, the fatigue life of the clip decreased sharply. Moreover, the normal wheel–rail force accompanied by high-frequency rail corrugations accelerated crack initiation and reduced the fatigue life. The findings of this study provide guidance for improving the service life of rail clips.

Field Measurement Analysis and Control Measures Evaluation of Metro Vehicle Noise Caused by Rail Corrugation

The noise caused by rail corrugation seriously affects the operation quality of metro vehicles. In this work, the rail corrugation, interior noise and wheel–rail noise of a metro line were tested, and the test results were compared with those after two kinds of treatments. The results show that rail corrugation is the main cause of the abnormal interior noise. The interior noise in many sections exceeds the limit, where clear rail corrugations from 31.5~63 mm are found. When the train passes through the rail corrugation section, the interior noise shows a clear increase, and the maximum increase is higher than 25 dB(A). After increasing the lateral stiffness of the track and rail grinding, the interior noise is reduced by 11.4 dB(A). After a long renovation time, the interior noise is effectively equal to that when the renovation was completed. The research results of this work can provide a reference for rail corrugation treatment and noise control.

On the modelling of normal wheel-rail contact for high-frequency vehicle–track dynamics analyses

ABSTRACT A transient wheel–rail rolling contact (RC) model and a vehicle–track coupled dynamics (CD) model are separately developed for a Hertzian contact in elasticity to calculate normal wheel–rail interactions at high frequencies. Short-wave irregularities with a wavelength of 20 ~ 400 mm are considered for a speed of 50 ~ 500 km/h. Results of 180 cases show that contact forces predicted by the CD model are significantly different from those by the RC model, suggesting that ignored or greatly simplified structural and wheel-rail flexibilities, transient effects, finite contact patch, etc. in the CD approach, play important roles in high-frequency interactions. Using the RC predictions as reference, a modified non-linear Hertzian spring is developed to improve the accuracy of the CD model. Such a modification provides references for determination of contact spring and contact filter effect at high frequencies, even though not applicable in a direct way.

Gearless Track-Friendly Metro with Guided Independently Rotating Wheels

Track–vehicle severe interaction on track with small curve radius results in rail wear and corrugation, and wheel polygonization, which drain considerable resources for rail grinding and wheels re-profiling in metro lines. To reduce the damage caused by track-vehicle severe interaction, the paper analyzes the reasons leading to rail wear and then proposes an architecture of a metro vehicle with independently rotating wheels driven directly by permanent magnet synchronous motors. The architecture is axle guidance, offered by passive linkages, which ensures that all axles are oriented radially, while control strategy was kept as simple as possible, identifying only two basic traction conditions. The concept is first discussed and then validated through a comprehensive set of running dynamics simulation performed with a multibody software to evaluate rail wear and rolling contact fatigue in traction/braking, coasting with different cant deficiency/excess conditions. The multibody dynamics simulation shows that the proposed architecture is virtually capable of avoiding both wear and rolling contact fatigue damages, and achieves the highest possible track friendliness. The concept of the proposed architecture is a track-fiendly metro architecture and could be a good reference for reducing rail-track interaction damages and maintainace cost.

Feasibility investigation of rail monitoring by wheel-mounted acoustic emission technology using two-dimensional analytical contact acoustic nonlinearity model

In an attempt to analyze the feasibility of a rail monitoring scheme with a wheel-mounted acoustic emission measurement method, a two-dimensional analytical spring model was proposed to interpret the interactions between acoustic waves and stationary wheel–rail contact interfaces. The spring model represents the coupling strength of the interfaces with their stiffness. It accommodates the environmental information of contact stiffness and the acoustic source information, such as the feature frequency and the incident angle in the analysis of interface transmissibility. The fractal dimension of the interface is introduced into the spring model to interpret the effect of the axle load on the interface stiffness and the variation in transmissibility. Discrete Rayleigh integration is further combined to obtain the directivity of the interface and estimate the acoustic field intensity in the entire wheel. A wheel–rail contact rig was designed to simulate the actual contact conditions in a railway. Experimental data acquired from this test rig were utilized to validate the model, with regard to the interfacial stiffness in normal incidence and amplitudes of the transmitted waves in oblique incidence. After verifying the reliability of the model, the acoustic field intensity in the wheel was visualized under the assumed environmental conditions. Finally, a discussion is presented to determine a proper angular separation for the wheel-mounted sensor system, and substantiate the feasibility of the system.

Model Updating of a Freight Wagon Based on Dynamic Tests under Different Loading Scenarios

This article presents an efficient methodology for the calibration of a numerical model of a Sgnss freight railway wagon based on experimental modal parameters, namely natural frequencies and mode shapes. Dynamic tests were performed for two distinct static loading configurations, tare weight and current operational overload, under demanding test conditions, particularly during an unloading operation of the train and without disturbing its tight operational schedule. These conditions impose restrictions to the tests, especially regarding the test duration, sensor positioning and system excitation. The experimental setups involve the use of several high-sensitivity accelerometers strategically distributed along with the vehicle platform and bogies in the vertical direction. The modal identification was performed with the application of the enhanced frequency-domain decomposition (EFDD) method, allowing the estimation of 10 natural frequencies and mode shapes associated with structural movements of the wagon platform, which in some cases are coupled with rigid body movements. A detailed 3D FE model of the freight wagon was developed including the platform, bogies, wheelsets, primary suspensions and wheel–rail interface. The model calibration was performed sequentially, first with the unloaded wagon model and then with the loaded wagon model, resorting to an iterative method based on a genetic algorithm. The calibration process allowed the obtainment of the optimal values of eight numerical parameters, including a double estimation of the vertical stiffness of the primary suspensions under the unloaded and loaded static configurations. The results demonstrate that the primary suspensions present an elastic/almost elastic behaviour. The comparison of experimental and numerical responses before and after calibration revealed significant improvements in the numerical models and a very good correlation between the experimental and numerical responses after calibration.

Study on the Effect of the Modeling Method of Railway Fastener on Rail Corrugation Prediction Model

Taking the typical corrugation phenomenon on a curved track in a metro line as the research object, the modeling method of railway fastener in the friction self-excited vibration model of a wheel–rail system is studied in this article. Firstly, according to the difference of the track support structure in the actual metro line, finite element models of the leading wheel–track system under different track forms, including the short sleeper with a DTVI2 fastener, the shock-absorbing track with a Cologne egg damping fastener, and the ladder sleeper track with a DTIII2 fastener, were established. The rail corrugation on a curved track with a small radius with three different sleepers is studied through complex eigenvalue analysis. In addition, the difference in rail corrugation finite element prediction model with a spring–damper pair model, solid-connected model, and solid-connectmodel is studied. The stability and vibration characteristics of a wheel–rail system with different tracks are studied by complex eigenvalue analysis. The research shows that the frictional self-excited vibration of a wheelset–track system occurs under saturated creep force, and the deformation caused by unstable vibration mainly occurs in the low rail and inner wheel, which can explain why the rail corrugation of a curved track with a small radius mainly occurs in the low rail. Compared with the spring–damper pair fastener model, the calculation result using the solid element fastener model (the solid-connected model and the solid-contact model) is closer to the measured data of the rail corrugation of the curved line with a small radius on the site. Of the two solid element fastener models, the latter is significantly more accurate than the former in predicting rail corrugation on the metro lines.

An improved finite element model for three-dimensional wheel–rail rolling contact

A three-dimensional wheel–rail rolling contact model (3D WRRCM) developed using the explicit finite element method (FEM) can be used to analyze the dynamic performances of wheelsets and tracks while considering the wheelset rotation and translation, as well as the real wheel–rail contact mechanism. When using the FEM with static initialisation (traditional model), the first step is to calculate the static wheel–rail displacement, strain, and stress when applying axle loading on the wheel and neglecting the wheelset rotation and translation. Then, using these results as the initial conditions, the dynamic wheel–rail displacement, strain, and stress are calculated while considering the wheelset rotation and translation by adopting the explicit dynamic solution method. However, obtaining a solution using this traditional method is time consuming, and the solution can be divergent because of the impulse produced by the suddenly increasing wheelset rotation when proceeding from the initial condition to the dynamic. The optimised method developed in this study can solve this problem. A comparison of the results from the traditional and optimised methods reveals that in the optimised method, the softer initial impulse effectively shortens the track length needed for the calculation and improves the solution efficiency.

Resonance of railway vehicles induced by floating-slab tracks: mechanism and countermeasures

For a railway vehicle moving over a series of floating-slab (FS) tracks with identical spans at a constant speed, track-induced resonance on the railway vehicle could occur when any of the frequencies of the FS track coincides with any of those implied by the wheel loads. Under this condition, the wheel–rail interaction will be aggravated and the ride comfort of railway vehicles will be deteriorated. This paper presents an experimental and numerical investigation of the mechanism and countermeasures for the resonant response of a metro vehicle induced by eccentric wheels travelling on FS tracks. The characteristics of the resonant response of the metro vehicle are revealed through the field tracking tests. A vehicle–track model considering the FS tracks and eccentric wheels is developed to analyse the resonant mechanism. Several countermeasures, including optimal design of FS track structure and elimination of wheel eccentric wear, are proposed to restrain the resonant vibration. The results show that the resonance caused by the eccentric wheels moving over FS tracks is the root causes for the ride comfort reduction of the metro vehicle. The field tests validate that re-profiling eccentric wheels can significantly eliminate the resonance phenomenon and enhance vehicle dynamics performances.

Study of rail-wheel contact problem by analytical and numerical approaches

This study presents the rail wheel contact problems under normal and tangential categories. Both analytical and numerical approaches were used for modelling, where the analytical approach assumed elliptical contact patches based on the Hertz theory. In the numerical approach, 3D finite element models were used to investigate non-elliptical contact patches. The only elastic material model was considered in the case of Hertz theory. However, in the case of finite element analysis, both elastic and elastoplastic material models were used to simulate the material's behavior under the applied load. The elastoplastic material model was used to determine the amount of stress at which the plastic deformation starts, which enables determining the rail wheel's critical load. The commercial software ABAQUS was employed for 3D modeling and contact stress analysis. The study shows maximum stress at 3 mm from the rail wheel contact surface when the maximum load of 85 kN is applied. This initiates the cracks in the subsurface and causes the portion of the rail wheel to break off in the form of spalling after a certain time.

Numerical Simulation and Parametric Analysis of Fatigue Crack in UIC60 Rail Thermite Welded Joint

The mechanism of rail-wheel contact is the most essential field of study in railway engineering since it requires extensive application expertise, diagnostic skills, and a trustworthy analysis technique. In this research the fatigue life of a UIC60 rail AT weld under vertical load and its parametric effect has been studied, and for that a three-dimensional elastic-plastic finite element model is created using ANSYS space-claim software, and then finite element method is employed to analyse the full-scale model of wheel-track and weld system with realistic three-dimensional solution. Model assembly components include axle, wheel, and thermite-welded rail. Simulation of contact between wheel and UIC60 rail weld with crack on weld at angles of 30 and 60 degrees with different coefficients of friction between the weld wheel contact and between crack surfaces was carried out under vertical loadings. In general, the Hertz contact theory assumptions are taken into consideration throughout the analysis, and the impacts on fatigue life are given by using damage mechanics method. The results of the wheel/weld fatigue crack analysis have been displayed to demonstrate the influence of different parameters on the fatigue life of cracks. The purpose of this study is to identify and safeguard the rail against failure, as well as to ensure the safety of passengers and to reduce the cost of maintaining the rail system.

In situ evaluation of contact stiffness in a slip interface with different roughness conditions using ultrasound reflectometry

Understanding the dynamic condition of the interface between a railway wheel and rail is important to reduce the risks and consider the effectiveness of countermeasures for tribological problems. Traditionally the difficulty in obtaining accurate non-destructive interfacial measurements has hindered systematic experimental investigations. Recently, an ultrasound reflectometry technique has been developed as a direct observation method of a rolling–sliding interface; however, the topography dependence under the high contact pressures in a wheel–rail contact has not been clarified. For this reason, a novel in situ measurement of the contact stiffness using ultrasound reflectometry was carried out for three different levels of roughness. A contact pressure equivalent to that in a wheel–rail interface was achieved by using a high-pressure torsion test approach. The dynamic change of contact stiffness with slip was measured using ultrasound and the influence of roughness was investigated. The measured changes were validated using a newly developed numerical simulation, and mechanisms to explain the observed behaviour were proposed in terms of fracture and plastic deformation of the asperity bonds. These findings could help in understanding the traction characteristics for different roughness conditions and also assist in understanding damage mechanisms better, such as wear and rolling contact fatigue.

Experimental research on vibration and noise of rail conveyor

Rail Conveyor is a highly energy-efficient and cost-effective bulk material transportation system, which merges the benefits of both belt conveyor technology and railway. Reducing vibration and noise is a key problem in the design of rail conveyor system, which has great social and economic significance for the realization of green environmental protection and sustainable development of bulk materials transportation. This article describes the field experimental test of vibration and noise. The vibration acceleration of rail conveyor was tested under different belt speed and different carriage spacing and different wheel materials of support carriage, and the noise of rail conveyor was tested under different belt speed and different test distance. Experimental results and analysis show that: With the increase of belt speed, the vibration and noise of wheel and rail of rail conveyor increase greatly, and the wheel rail vibration and noise decrease with the increase of the distance between the support carriages, and the wheel material has a great influence on the vibration.

Estimation of fatigue life parameters of an Alumino Thermic weld on UIC60 rail joint using LEFM

At wheel track contact point, the high stress concentration, poor weld quality, and heterogeneity of weld material are the main factors that cause fatigue crack on any rail weld. Railway network agencies are concerned about the safety of the railway track when it comes to detecting and fixing weld faults to avoid vehicle derailment and loss of lives. This study analysed a numerical simulation of fatigue crack and its evolution under loaded service condition. A 3-D CAD wheel rail weld assembly model was built to study an AT welded joint under fatigue, and for stress concentration factor (SIF) calculation. The results are found by inserting a semi elliptical crack on the rail weld head surface with ANSYS, and then numerical simulation has been performed to get the different three modes of SIF at rail weld crack. The analysis findings data was recorded with critical fracture parameters of SIFs and its number of cycles to failure using LEFM technique and respective results have been plotted. With ANSYS the stress intensity on a crack will be resulted. By using numerical method, the critical crack size and number of cycle load with fatigue life of rail would be determined. The numbers of rail weld inspection per year has been determine by using the maximum number of cycle. The aim of this paper is to develop an effective inspection and maintenance frequency based on rolling contact surfaces crack propagation analyse. This will help to prevent the occurrence of rail failure by taking the required action at the right time, and extend the rail life expectancy, reduce the rail maintenance work and its cost.

Analyzing behaviour of a rail wheel assembly with alumino thermite weldment with modal analysis simulations in ANSYS

The Free vibration response of the Railway track is an important area in the design of the Rail and its joints to improve the ride comfort of the passengers. In this study, the rail weld considered is alumino thermite weldment used in majority of Indian Railways network. This paper aims at the study of the vibration response of rail wheel assembly having an AT weld on as a rail joint subjected to free vibration and to find the Natural frequencies of vibration and mode shapes. The geometric model of rail and weldment with wheel and axle components is modelled using Space-claim which is a part of ANSYS package and analysed using numerical simulation package ANSYS 2020 Workbench. In this work, free vibration analysis or modal analysis of the rail weld is carried out to extract the first few modes of vibration. The Natural frequencies obtained along with the corresponding mode shapes of the rail weldment show that they are within the permissible range specified by the standards of railway department also for better ride comfort of the passenger.

Full-scale test and numerical simulation of wheelset-gear box vibration excited by wheel polygon wear and track irregularity

The wheelset-gear box of high-speed train is the typical unsprung mass serving in the complex excitation environment. To investigate the independent and compounded influences of wheelset out-of-roundness, wheel polygon wear and track irregularity on the vibration performance of wheelset-gearbox system, the 1:1 high-frequency excitation test based on the rolling test rig is carried out within the speeds of 100 ∼ 500 km/h. The corresponding multi-body dynamic model is established and validated. The detailed wheel-wheel contact relations are discussed. The research results indicate that the test rig dynamic model can capture the vibration amplitude and main frequency characteristics well, especially for the vibration below 1000 Hz. For the wheelset-gearbox system without track excitation, its vibration energy is basically concentrated in the resonance region of test object. At higher speeds, the vibrations induced by wheelset and motor rotation gradually become dominant. Under excitation of the grinded polygon wear in rail wheel, the multiple-frequency vibration almost determines the system vibration level within the test speed ranges, whilst the vibration induced by the wheelset and motor rotation plays an important role only at the speed above 300 km/h. In comparison, the high-speed track random irregularity contributes very small vibration magnitude. For the axle box, the vibration amplitude composition ratios led by the excitations of wheelset out-of-roundness, rail wheel polygon wear and track irregularity are around 26.7%, 48.3% and 25% correspondingly. And for the gear box, the composition ratios reach 38.46%, 32.05% and 29.49% respectively. The wheel polygon wear has been the main excitation source in the high-frequency vibration of wheelset system, followed by the wheelset 1st-order out of round and track irregularity in sequence.