The Wheel-rail adhesion is essential for safe and stable vehicle operation. Since the beginning of railway construction, many railway researchers and engineers have been actively involved in the ...study of this railway-specific issue. Most studies to date have focused on the various factors influencing the adhesion characteristics and quantifying the extent of their influence. This paper gives an overview of experimental and theoretical studies on evaluating wheel-rail adhesion characteristics under conditions where different third-body materials are interposed between wheel and rail and describes further challenges and research directions in the field of adhesion for the future.
•The influences of various contaminations between wheel and rail have been assessed.•Third-body material has a significant influence on the wheel/rail adhesion coefficient.•The adhesion coefficient decreases in the order of dry, wet, oil, wet leaf, and dry leaf.•Alumina particles, sand, and traction gel have the effect of increasing adhesion.
The modelling and the reduction of wear due to wheel–rail interaction is a fundamental aspect in the railway field, mainly correlated to running stability and safety, maintenance interventions and ...costs. In this work the authors present two innovative wheel profiles, specifically designed with the aim of improving the wear and stability behaviour of the standard ORE S1002 wheel profile matched with the UIC60 rail profile canted at 1/20rad, which represents the wheel–rail combination adopted in Italian railway line.
The two wheel profiles, conventionally named CD1 and DR2, have been developed by the authors in collaboration with Trenitalia S.p.A. The CD1 wheel profile has been designed with the purpose of spreading the contact points in the flange zone on a larger area in order to reduce wear phenomena and having a constant equivalent conicity for small lateral displacements of the wheelset with respect to the centred position in the track. The DR2 wheel profile is instead designed in order to guarantee the same kinematic characteristics of the matching formed by ORE S1002 wheel profile and UIC60 rail profile with laying angle αp equal to 1/40rad, widely common in European railways and characterized by good performances in both wear and kinematic behaviour.
Wheel profiles evolution has been calculated through a wear model developed and validated by the authors in previous works with experimental data relative to the Italian Aosta-Pre Saint Didier railway line. This model comprises two mutually interactive units: a vehicle model for the dynamic simulations and a model for the wear assessment. The whole model is based on a discrete process: each discrete step consists in one dynamic simulation and one profile update by means of the wear model while, within the discrete step, the profiles are supposed to be constant. The choice of an appropriate step is crucial in terms of precision and computational effort: the particular strategy adopted in the current work has been chosen for its capacity in representing the non-linear wear evolution and for the low computational time required.
In the present research the investigated trainset is the passenger vehicle ALSTOM ALn 501 “Minuetto”, which is usually equipped with the standard ORE S1002 wheel profile and UIC60 rail profile canted at 1/20rad in Italian railways. The entire model has been simulated on a virtual track specifically developed to represent a statistical description of the whole Italian line. The data necessary to build the virtual track and the vehicle model were provided by Trenitalia S.p.A. and Rete Ferroviaria Italiana (RFI). Both the innovative wheel profiles developed in this research activity for the UIC60 rail with cant 1/20rad have proven to work fine in terms of resistance to wear if compared with the old ORE S1002 wheel profile.
► Design of two innovative wheel profiles with high wear and stability performance. ► Development of an innovative model for the wear prediction at the wheel–rail interface. ► Multibody models and an innovative wheel–rail contact model have been used to study the dynamics of the vehicle. ► The performances of standard and new profiles have been compared to each other on the whole Italian railway net.
Generally, the equivalent conicity function (ECF) is denoted by equivalent conicity at 3mm (λ
3mm
) and a Nonlinearity Parameter (NP). NP describes the nonlinearity of the ECF and its influence on a ...vehicle design is explored thoroughly, however, NP's role in vehicle and track maintenance is not researched yet. This paper investigates the influence of track maintenance actions on vehicle dynamics with help of NP vs λ
3mm
scatter plots of ECF database. The ECF database is constructed by combining measured worn wheel and rail profile pairs of the Swedish high-speed vehicle and rail network, respectively. The ECF database revealed an inverse relationship between λ
3mm
and NP, i.e., NP is negative for larger λ
3mm
values. The combination of negative NP and high λ
3mm
causes reduction in the vehicle's nonlinear critical speed and vehicle often exhibit the unstable running on the Swedish rail network. Thus, the occurrence of ECF with negative NP and high λ
3mm
is undersirable and the undesirable ECF can be converted into desirable ECF by grinding the rail, which converts ECF's into positive NP and low λ
3mm
combinations. Thus, the NP parameter along with the λ
3mm
must be considered in track maintenance decisions.
Wheel profile wear (WPW), out-of-roundness (OOR), and wheel diameter difference (WDD) are three common types of damage to subway wheels, and each has its own set of operational restrictions. However, ...in the actual operation, the same wheel is frequently accompanied by multiple forms of damage and the various forms of damage interact with each other. Considering the characteristics of this damage, this paper aims to investigate the influence law and characteristics of wheel coupling damage on the vehicle dynamic performance, as well as the differences in the vehicle performance response caused by the two main coupling conditions, namely, OOR coupling WDD and WPW coupling WDD. The results reveal that the vehicle performance reaction generated by WPW coupled with WDD is more substantial than the vehicle performance response caused by OOR combined with WDD. Furthermore, while the wheel coupling damage deteriorated several of the vehicle dynamic performance indicators, it also enhanced some of the performance parameters during vehicle operation to some extent. The experiments demonstrate that the presence of WDD minimises the peak of wheel/rail lateral force caused by OOR and suppresses the deterioration of the ride comfort index caused by the rise of WPW.
To improve the handling and maneuverability of four-wheel steer (4WS) and in-wheel motor driven electric vehicle (EV) in which the mechanical properties of tires are unknown, an optimal coordinated ...control combining active rear wheel steering (ARS) and direct yaw moment control (DYC) in the form of active drive torque distribution is proposed. By designing a new type of particle filter (PF), the online identification of unknown tire model is realized and its uncertainties and road surface disturbances are both considered. The constraints of vehicle motions tracking ideal values are derived according to the estimated tire lateral forces with Lyapunov stability theory. And then based on the thought of backstepping and optimization, the drive torque distribution method and the rear wheel steer strategy are obtained aiming at minimizing tire load and control inputs, which also take the effective working range of in-wheel motor into account. Finally, the validity and practicability of overall controller are verified through the simulation of Carsim and Matlab/Simulink. The proposed control strategy lays a theoretical foundation for the integration and optimization of 4WS EVs driven by in-wheel motors.
•Statistical approach for assessment of probability of rail break due to wheel–rail impact loading.•Multi-dimensional stochastic parameter space including detector and field test data.•Meta-models ...based on poly-harmonic splines to reduce computational cost of analysis.
A simulation procedure to predict the probability of rail break due to a measured wheel load spectrum is presented. The load distribution includes a representative proportion of high-magnitude dynamic loads generated by out-of-round wheels. Linear elastic fracture mechanics is applied to determine the stress intensities of pre-existing rail head cracks in a continuously welded rail subjected to combined bending and temperature loading. Rail bending moments are evaluated using a validated time-domain model of dynamic vehicle–track interaction. The considered multi-dimensional stochastic parameter space includes field test data of dynamic loads from a wheel impact load detector and crack depths from eddy current data. Meta-models based on poly-harmonic splines are applied to reduce the computational cost of the analysis. Supported by the extensive field test data, the simulation procedure is demonstrated by investigating the influences of freight traffic type, track support stiffness and rail temperature on the probability of a rail break initiated at a pre-existing rail head crack.
Wheel flat is a form of wheel tread defect that reduces the service life and running safety of trains and tracks. Based on the multi-body system dynamics theory, a rigid-flexible vehicle-turnout ...dynamic coupling modelwas established, and the wheel diameter-varying flat simulation method used to create wheel flat models of different sizes. The most unfavourable phase of flats on the wheels of a vehicle crossing a turnout was studied by scanning and calculating the phase of the flats. The influence of flat size and vehicle speed on a vehicle with flats crossing a turnout was also analyzed. The results show that, compared with a normal wheel crossing a turnout and a wheel flat acting on the interval rail, a wheel flat acting on the wheel load transition of the frog area will excite greater vertical wheel-rail forces and vertical axle box vibration acceleration; in the turnout area, the main frequency band of the vertical vibration acceleration of the axle box is 550-800 Hz, which is rarely affected by the size of flats or the speed of the vehicle. The third-order bending mode of the wheel is excited when the wheel transits from the wing rail to the point rail.
Wheel acoustic roughness of one metro line in China shows that the wheel polygonal wear (WPW) on both sides of the wheelset is asymmetrical. The dominant harmonics of the left and right wheels are ...12–13, but with large differences in acoustic roughness levels. To analyse the causes of the asymmetrical WPW (AWPW), an investigation of the acoustic roughness of the wheels and rails and a modal analysis of the wheelset–track system are carried out. In addition, a long-term wear model considering the flexibility of the wheelset and track is established to provide insight into the initiation and evolution of the AWPW. The results of the experiments and simulations show that the natural asymmetric vibration mode in the wheelset–track system with a frequency of 83 Hz is the main cause of WPW, which can be excited on sharp curves. The difference between the lengths of the left and right curved tracks with small radius is the cause of AWPW. The residual WPW after reprofiling and rail corrugation with a wavelength of about 200 mm are the main sources of excitation for the asymmetric natural vibration.
•The features of wheel polygonal wear on one of the metro lines in China were measured.•A wheel polygonal wear prediction model considering the asymmetric vibration of the wheelset in curving is proposed.•The wheel polygonal wear is primarily caused by the wheelset–track system's natural asymmetric vibration mode at 83 Hz.•The reasons of the asymmetric wheel polygonal wear are revealed.
•A wheel defect detection methodology is proposed using Bayesian dynamic model.•The proposed approach enables probabilistic estimation of damage extent and uncertainty.•The proposed approach enables ...change-point detection in time series.•The proposed approach detects wheel defects in a real-time manner.•Real-world monitoring data are used to demonstrate the proposed methodology.
High-speed rail (HSR) is being developed in Asian and European countries to satisfy the rapidly growing demand for intercity services and to shore up economic growth. The rapid growth of HSR, however, has posed great challenges regarding operation safety, reliability and ride comfort. Irregular wheel defects can induce high-magnitude impact forces hindering safety and ride comfort of HSR and may also cause damage to rail tracks and vehicles. The focus of this study is to develop a real-time defect detection methodology based on Bayesian dynamic linear model (DLM) enabling to detect potentially defective wheels in real time. The proposed methodology embraces logics for (i) prognosis, (ii) potential outlier detection, (iii) identification of change occurrence (change-point detection), and (iv) quantification of damage extent and uncertainty. Relying on the strain monitoring data acquired from high-speed train bogies, the Bayesian DLM for characterizing the actual stress ranges is established, by which one-step forecast distribution is elicited before proceeding to the next observation. The detection of change-point is executed by comparing the routine model (forecast distribution generated by the Bayesian DLM) and an alternative model (the mean value is shifted by a prescribed offset) to determine which better fits the actual observation. If the comparison results are in favor of the alternative model, it is claimed that a potential change has occurred. Whether such an observation is an outlier or the beginning of a genuine change (change-point), three metrics (i.e., Bayes factor, maximum cumulative Bayes factor and run length) are performed for further identification. Once a change-point is confirmed, Bayesian hypothesis testing is conducted for the purpose of damage extent assessment and uncertainty quantification. A severe change, if identified, implies that the quality of train wheels has suffered from a significant alteration due to defects. In the case study, two cases making use of strain monitoring data acquired by fiber Bragg grating (FBG) sensors affixed on bogies are illustrated to verify the performance of the proposed methodology for real-time wheel defect detection of in-service high-speed trains.
High-order polygonal wear wheels have been detected on metro express train operating on one metro line in China, which cause fatigue failures of steel coil springs in the primary suspension. A series ...of tests and theory analysis were conducted to figure out the mechanism of wheel high-order polygonal wear. The wheel out-of-roundness (OOR) measurement results show that the wheels exhibit polygonal wear with 12-14 harmonics, which are very different from other metro train wheels reported in the literature. The investigation results indicate that the first bending vibration of the wheelset is the root cause of wheel high-order polygonal wear. Rail corrugation with a wavelength of 200 mm in the 1/3-octave band on sharply curved tracks is the main excitation source of the first bending vibration of the wheelset. The formation process and key influencing factors of wheel high-order polygonal wear are analysed in detail. Three measures are suggested to mitigate the formation of wheel high-order polygonal wear.
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