Wheel Rail Research Articles

Evaluation of Dynamics of a Freight Wagon Model with Viscous Damping

The aim of this work was to perform a simulation analysis of the dynamics of a freight wagon with a variant vibration damping: dry friction and viscous damping. The following mathematical models of the damping characteristics are presented: the Maxwell model and the Kolsch model. The differences among the types of damping were first analyzed based on the dynamic responses of the 1 DOF model. Simulation studies were then carried out in a VI-Rail environment with the use of S-curved track models comprising short straight sections connecting the curves. The track models differed in the values of curve radii, cant, and length, which made it possible to run at different speeds. The multibody model of the vehicle represents a typical two-axle freight wagon. The dynamics of the wagon model were investigated for two states: empty and laden. Standard kinematic and dynamic values were compared in order to investigate if the nature of the damping has a significant impact on the dynamic properties of a freight wagon. The analysis of the simulation study showed that replacing dry friction damping with the viscous one can generally reduce forces acting on the wheel–rail contact, which, in turn, can be related to improving the running behavior of wagons while reducing the negative impact on the track.

Effects of Wheel Flats on Vibration and Stress Response of the Wheel-Rail System in High-Speed Trains

With the advancement of high-speed and lightweight vehicles, the occurrence of wheel tread wear, including wheel flats, has escalated. The resulting impact loads on axle-end components and the dynamic response of the axle cannot be overlooked. On-track tests were conducted on wheel flats to obtain wheel-rail forces, axle box vibration accelerations, and axle stresses during service. Time–frequency analysis was employed to uncover patterns of variation with speed. Additionally, a dynamic model of the high-speed train–track system was developed to replicate test conditions, investigating the characteristics of wheel–rail loads and structural elastic vibrations under high-frequency excitation for various flat sizes and higher operating speeds. The findings reveal that under wheel flats, the time-domain response of the wheel–rail system exhibits periodic impacts, while the frequency-domain shows high-frequency energy comprising multiple harmonics of the wheel rotation frequency. Wheel–rail forces, axle box vibration accelerations, and axle stresses exhibit inflection points with increasing speed, particularly within the 120–160 km/h range. In the high-frequency domain, axle stresses display characteristic frequencies that remain unchanged with speed, attributed to the coupled vertical bending vibration modes of the wheel–rail system. These research results offer foundational support for predicting fatigue damage to axle-end components, assessing axle stress, and establishing tolerances for tread defect limits.

Research on the Wheel Wear and Rolling Contact Fatigue of Metro Vehicle Induced by Rail Corrugation

Rail corrugation is a common characteristic of track wear and exacerbates wheel–rail interaction and accelerates wheel wear and crack propagation. This study focuses on wheel wear and rolling contact fatigue of a metro vehicle under rail corrugation. Firstly, the characteristics of rail corrugation under service conditions are determined by statistical analysis of field data, and 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, a simulation analysis of wheel rolling contact fatigue under rail corrugation is carried out. The results show that the increases in superficial fatigue index and accumulated fatigue are respectively 1.52 and 6.16 times in the wavelength range of 30 to 90 mm larger than those in the range of 90 to 210 mm. Furthermore, the cracks more easily occur 2 to 4 mm from the outer surface of wheel and expand along the wheel tread.

Analysis of 3k Experiments Applied to Railway Braking: Influence of Contaminants and Train Speed

The presence of contaminants influences braking efficiency in the railway system because it alters the adhesion at the wheel–rail interface. It is essential to study this phenomenon, as contaminants reduce the friction between wheels and rails, which impacts braking and transport safety. In addition, these contaminants increase the risk of derailments. The objective of the research was to determine the impact of different contaminants and operating speeds on the critical braking system’s responses. Using the 3k full factorial experimental design methodology, with analysis of variance (ANOVA) and linear and quadratic regressions, visualized using surface graphs, the effects of three operating conditions were studied: clean rails, with sand and sawdust, and driving the train at three operating speeds. These conditions gave rise to variations in braking distances, maximum creep, wheel slip times, and maximum peaks of electric current when braking in each experiment. The tests were carried out on the straight section of a β-shaped track and a railway vehicle, designed at a scale of 1:20. The analysis reveals that the braking distance increases significantly with surface roughness (clean track < sawdust < sand). At 0.75 m/s, the sawdust track reduces braking distance by 21% compared with the clean track; at 1.00 m/s, the reduction is 19%; and at 1.30 m/s, it is 35%.

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.

Experimental investigation of wheel rail adhesion under leaf contamination conditions

ABSTRACT In order to investigate the adhesion degradation caused by leaves and the adhesion improvement behaviour under wheel sliding conditions, a novel circumferential wheel/ring based rolling contact test rig was used in this paper. The leaves were meticulously distributed across the ring-shaped rail surface to closely mimic real-world track conditions, facilitating adhesion testing under scenarios involving leaf pulp, green leaves, soaked fallen leaves, and different species of leaves. The results indicate that leaves can induce adhesion values as low as 0.05, with no significant discrepancy observed in the low adhesion values caused by different leaf species. In addition, the study shows that the low adhesion surface formed by leaves is not static, the sliding action of the wheels can effectively remove the black substance layer formed by leaf debris on the rail surface, with the cleaning effect becoming more pronounced with increasing speed and axle load. Finally, based on the experimental results, this paper proposes characteristic parameters for the Polach wheel-rail adhesion formula under leaf contamination conditions, and develops an empirical formula for adhesion improvement.

Development of hunting oscillation detection algorithm for railway vehicles by using accelerometers

In this study, an algorithm was developed to detect hunting oscillation in railway vehicles using only accelerometers. Typically, the wheel profile of most railway vehicles has a conical shape, causing inherent hunting oscillation. The critical speed at which hunting oscillation occurs is determined by the wheel profile, rail profile, and dynamic characteristics of the railway vehicles. Hunting oscillation significantly impairs ride comfort, reduces running stability, and increases the risk of accidents such as derailment. Therefore, if hunting oscillation occurs during railway operation, it must be detected, and a deceleration procedure should be applied immediately to ensure dynamic stability. The detection algorithm in this study is based on the geometric behavior of the bogie. It utilizes longitudinal and lateral acceleration data from accelerometers installed on the upper frame of the bogie above the axle boxes. The algorithm processes the acceleration data to obtain the hunting oscillation frequency and harmonics, integrating all this data to calculate the Index of Hunting Oscillation. Validation was performed through simulations using a standard electric train model, confirming the algorithm’s effectiveness. Additionally, tests on actual bogies using a roller rig validated the algorithm’s performance in detecting hunting oscillation effectively.

Adaptive robust constraint-following control method for improving carbody hunting stability of high-speed trains

The low-frequency carbody hunting motion of high-speed trains (HSTs) frequently occurs due to the complex operating environment and deterioration of wheel–rail contact conditions. It not only affects ride comfort but also poses a risk of derailment safety accidents for HSTs. In such scenarios, traditional passive suspension systems struggle to ensure satisfactory dynamic performance of HSTs. However, active suspension systems can offer an effective solution. To enhance the low-frequency carbody hunting stability and environmental adaptability of HSTs, this study proposes a novel adaptive robust displacement inequality constraint following control (AICFC) method for active suspension utilising the beneficial nonlinearity inspired by bio-inspired structures (BIS). The effectiveness of the proposed AICFC-BIS method is validated through numerical simulations comparing it with other control strategies. Simulation results show that the AICFC-BIS method can effectively suppress low-frequency carbody hunting motion and improve the dynamic performance of HSTs. Compared with conventional passive suspensions and other active suspensions, HSTs equipped with AICFC-BIS active suspension exhibit significantly reduced operational safety risk and improved ride comfort indices while being energy efficient.

Oновлення парку рухомого складу українських залізниць з орієнтацією на інтеграцію в європейські транспортні мережі

The strategic aim of further development of the Ukrainian railways is rolling stock and infrastructure renewal to meet the demands of the Ukrainian economy, including a rapid integration into the European transport service. The paper presents the results of recent studies conducted at the Department of Statistical Dynamics and Multidimensional Mechanical System Dynamics, the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, with the aim to solve important problems in the development of the Ukrainian railway transport. The studies were aimed at developing scientifically substantiated decisions on Ukrainian rolling stock renewal oriented at integration into the European railway networks. To do this, a cycle of theoretical and experimental studies was conducted at the department. Consideration was given to the problem of wheel–rail contact pair improvement by identifying a wheel profile that would offer an acceptable car ride performance and acceptable conditions of car–rail interaction both on the Ukrainian and the European railways and reduce vehicle and rail wear. The car ride performance of an articulated passenger train was simulated mathematically for its motion at different speeds along a track of arbitrary alignment and profile, and the effect of different car and track parameters on the ride performance was estimated. Energy-absorbing devices were developed to increase the passive safety of a speedy locomotive-hauled passenger train and a multiple-unit train in emergency collisions with obstacles according to the Ukrainian Standard DSTU EN 15227. Service loads on the load-bearing components of swap-body freight cars were estimated, and recommendations were developed on fasteners that would provide safe transportation of various freights in swap-body cars. Based on the results of the studies, a number of design solutions were proposed for Ukrainian railway vehicle components. Their implementation will offer a sizeable economic benefit, increase the train speed and safety, improve the vehicle–track interaction, and facilitate the formation of an up-to-date home railway complex and its integration into the European railway networks.

Research on wheel–rail impact dynamics due to combined rail weld irregularities and polygonal wheel effects considering 3D contact geometry

The geometric irregularities of rail welds and polygonal wheels are common defects observed in high-speed railways, leading to the generation of high-frequency impact forces and vibrations in the wheel–rail contact system. This research establishes a novel vehicle-track coupled dynamic model that incorporates a 3D wheel–rail contact model using meshing grid and conjugate gradient methods to study the high-magnitude wheel–rail impact forces caused by rail weld irregularities and polygonal wheel combinations. The primary objective of this study is to develop a precise 3D contact model that incorporates the actual geometry of wheel and rail surface irregularities into the calculation of vehicle-track dynamic interactions. The study evaluates the effects of 3D rail weld irregularities and polygonal wheels on wheel–rail dynamic interaction by comparing results with those obtained from a conventional vehicle-track coupled model that considers a 2D contact model. The results show that the lengths and depths of polygonal wheels and rail weld irregularities, as well as vehicle speeds, significantly increase the wheel/rail dynamic impact forces. The results also indicate that the widening of irregularities not only significantly affects the wheel–rail contact force but also has an important influence on the contact stiffness.

Effect of Thermal Load Caused by Tread Braking on Crack Propagation in Railway Wheels on Long Downhill Ramps

To investigate the propagation behavior of thermal cracks on the wheel tread under the conditions of long downhill ramps, a three-dimensional finite element model of a 1/16 wheel, including an initial thermal crack, was developed using the finite element software ANSYS 17.0. The loading scenarios considered include mechanical wheel–rail loads, both with and without the superposition of thermal wheel–brake shoe friction loads. The virtual crack closure method (VCCM) is employed to analyze the variations in stress intensity factors (SIFs) for Modes I, II, and III (KI, KII, and KIII) at the 0°, mid, and 90° positions along the crack tip. The simulation results show that temperature is a critical factor for the propagation of thermal cracks. Among the SIFs, KII (Mode II) is larger than KI (Mode I) and KIII (Mode III). Specifically, the thermal load on the wheel tread during braking contributes up to 23.83% to KII when the wheel tread reaches the martensitic phase transition temperature due to brake failure. These results are consistent with the observed radial propagation of thermal cracks in wheel treads under operational conditions.

Theoretical Study of the Wear of a Reduced-Diameter Wheel for Freight Wagons, Based on Its Diameter

This paper presents the development of a numerical analysis model designed to estimate the lifespan of reduced-diameter wheels used in freight wagons based on their diameter, under quasi-static conditions. These wheels are increasingly being used in combined transport applications, where they are installed in various bogie configurations and subjected to different operational environments. However, due to the unique characteristics of reduced-diameter wheels, their lifespan has been scarcely studied. To accurately build this model, an in-depth investigation of the rolling phenomenon was required, addressing key issues in the track–vehicle interaction and establishing relationships between these factors. After constructing the rail–wheel interaction model, it was applied to calculate the lifespan of wheels with standard, medium, and reduced diameters under identical conditions for comparison. This approach makes it possible to determine the lifespan of reduced-diameter wheels relative to standard ones, as well as to observe how lifespan changes with wheel diameter, and it is observed how lifespan diminishes non-linearly with decreasing diameters. The underlying reasons for this variation are explained through a comprehensive understanding of the rolling phenomenon, enabled by the full analysis.

Диагностика системы взаимодействия железнодорожного пути и подвижного состава по параметрам комфорта езды и эквивалентной конусности

Purpose: to identify the influence of the geometric parameters of wheel sets and rail track on the smoothness of the ride and the level of passenger comfort for an automated diagnostic system. Methods: statistical methods were used to conduct the research. Sampling and analysis of statistical observation data made it possible to identify existing approaches to assessing the levels of interaction of the wheel-rail system at different speeds. The track sections grouped into rows along pickets were assessed in terms of passenger ride comfort and equivalent conicity. Materials used in the public domain and official websites, as well as research by the authors. Results: a list of factors influencing the conditions of interaction between highspeed rolling stock and the railway track has been identified. Data were obtained for indicators of ride comfort and equivalent conicity for the St. Petersburg — Moscow line along pickets at actual realizable speeds. Practical importance: the possibility of using remote measurement diagnostics to determine the geometric parameters of wheelsets and rails and the geometric parameters of the rail track has been determined. Suggestions for improving the qualitative assessment of the interaction of the wheel-rail system are recommended.

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.

A new insight into the macroscopical cause of wheel rolling contact fatigue on Y25 wagons – axle box longitudinal guidance deviation

Wheel rolling contact fatigue (RCF) is a tricky issue for the railway industry. It is recently reported that the wheel RCF on Y25 bogies is more severe compared to other bogies with similar primary suspension structures. The axle box longitudinal guidance deviation (ALGD) could be a reason for the wheel RCF according to field observations. In this paper, a Y25 wagon dynamics model is firstly established and validated. The ALGD is modelled using non-linear force elements. The wheel damage function is used for RCF evaluation. Then, effects of ALGDs on force balances of wheelsets are preliminarily analysed in a quasi-static state. Four different scenarios for ALGDs are simulated and corresponding wear numbers are calculated. It proves that the wheelset lateral displacement, wheel‒rail contact forces, and RCF index will dramatically increase with the ALGD value. Potential wheel‒rail contact zones for the bogies with ALGDs are basically consisted with the recorded wheel RCF zones. Finally, maintenance suggestions are proposed according to the wheelbase deviation. The ALGD threshold should be 1.0 and 2.75 mm for the prevention on wheel RCF and wear, respectively. The results of this paper may provide a new insight into the macroscopical cause of wheel RCF on Y25 bogies.

Finite element analyses of rail head cracks: Predicting direction and rate of rolling contact fatigue crack growth

A numerical framework in 3D for predicting crack growth direction and rate in a rail head is presented. An inclined semi-circular surface-breaking gauge corner crack with frictionless crack faces is incorporated into a 60E1 rail model. The investigated load scenarios are wheel–rail contact, rail bending, thermal loading, and combinations of these. The crack growth direction is predicted using an accumulative vector crack tip displacement criterion, and Paris-type equations are employed to estimate crack growth rates. Results are evaluated along the crack front for varying crack radii and crack plane inclinations. Under the combined load cases and in the presence of tractive forces, the crack is generally predicted to go deeper into the rail than under pure contact. Crack growth rates for the combined load cases are higher than (but still close to) that for pure contact. A tractive force will increase growth rates for smaller cracks, whereas a steeper (45°) inclination will decrease the growth rate under the studied conditions as compared to a shallower (25°) inclination. Results should be of use for rail maintenance planning where deeper cracks require more machining efforts.

Investigation on fatigue parameters in railway wheels using a critical plane model

The contact areas between rail and wheel are critical in determining the performance of rail vehicles. Analyzing the mechanics, materials, tribology, and geometry of the interface is important to understand the contact damage mechanisms, fatigue parameter and fatigue life. Developing a simplified and novel approach to predict crack initiation and fatigue life is key for investigating contact fatigue of rail wheel interaction. This study aims to investigate rolling contact fatigue (RCF) cracks and fatigue life in railroad wheels using Finite Element Model (FEM). Using a proper material model that accounts for plastic shakedown, ratchetting, and cyclic hardening for both the rail and wheel materials, the FEM model is analyzed with the help of Abaqus 2020 tool. The submodelling technique was implemented to reduce computation demand. Stress and strain history outputs extracted from the submodel (at 0 mm, 1.3 mm, 2.6 mm, and 3.6 mm depths) were used to predict critical plane orientation, crack initiation and fatigue life using critical plane models. The orientation of critical (crack) plane was found using a novel MATLAB algorithm by searching for a plane with maximum fatigue parameter (FPmax). The investigation reveals that the location of maximum damage is the subsurface and the crack angles fall within the range of (0°, 40°), (62°, 123°) and (143°, 180°) with a 5 % margin and at a depth of 2.6 mm below the wheel surface. The determined fatigue crack initiation and life at this specific location were 6178 and 7174 cycles, respectively. Predicting the critical zone which is susceptible to shorter crack initiation and fatigue life is a crucial to prevent wheel failure.

DEM modelling of surface indentations caused by granular materials: application to wheel–rail sanding

The presented surface indentation model is one step towards building a DEM model for wheel–rail sanding. In railways, so-called low-adhesion conditions can cause problems in traction and braking, and sanding is used to overcome this problem. Sand grains are blasted towards wheel–rail contact, fracture repeatedly as they enter the nip and are drawn into the contact and then increase adhesion. Research on this topic has mostly been experimental, but focussed on adhesion enhancement measurement. Thus, physical mechanisms increasing the adhesion are not well understood. Previous works involved experiments and DEM modelling of single sand grain crushing tests under realistic wheel–rail contact pressures of 900 MPa, focusing on sand fragment spread and formation of clusters of solidified fragments. In the experiments, indents in the compressing steel plates were also observed, which are also observed on wheel and rail surfaces in railway operation. These are now modelled by adapting an existing surface indentation model from literature to the case of surface indentations caused by granular materials. Two test cases are studied, and experimental spherical indentation tests for model parametrisation are presented. In a proof of concept, the mentioned single sand grain crushing tests under 900 MPa pressure are simulated including the surface indentation model. This work contributes to DEM modelling of wheel–rail sanding, which is believed to be a good approach to deepen the understanding of adhesion increasing mechanisms under sanded conditions.

A comprehensive wheel–rail contact model incorporating sand fragments and its application in vehicle braking simulation

Increasing the wheel–rail adhesion coefficient by spreading sand grains to the wheel–rail interface is a common approach to improve the traction and braking efficiency of trains. To simulate this process accurately, two highlights are presented in this paper. Firstly, this paper proposes a wheel–rail contact model considering sand fragments, a third body, based on the non-Hertzian theory, which includes a random sand-grain generator and a sand crushing model. The proposed wheel–rail model is used to analyze the wheel–rail adhesion state after sand grains enter the wheel–rail contact interface. How sand particles change the distribution of normal force and tangential force to affect the wheel–rail adhesion is clarified and, in addition, the influence of the parameters of sand fragments on the wheel–rail adhesion coefficient is given. Secondly, a vehicle system dynamics model considering sanding and wheel slip protection (WSP) control is developed to analyze the effect of sanding on braking distance and wheel slip during braking processes. The wheel–rail contact model and the vehicle system dynamics model presented in this paper can support the study of more effective sanding and adhesion enhancement devices.

The Wheel–Rail Contact Force for a Heavy-Load Train Can Be Measured Using a Collaborative Calibration Algorithm

The wheel–rail contact force is a crucial indicator for ensuring the secure operation of a heavy-load train. However, obtaining the real-time wheel–rail contact force of a heavy-load train is a challenging task as, due to safety considerations, it is not possible to install instrumented wheelsets on heavy-load trains. This work presents a novel approach to quantify the wheel–rail contact force of a heavy-load train, utilizing a cooperative calibration methodology. First, a ground measurement platform for the wheel–rail contact force of a heavy-load train is constructed on a selected rail section. The railway inspection car’s wheel–rail contact force measurement system is fine-tuned using a multilayer perceptron calibration approach, and the ground platform then uses the results to fine-tune the railway inspection car’s examined wheelset. Second, based on actual measured data on the wheel–rail contact force of a heavy-load train, and using the golden jackal optimization algorithm, the multilayer perceptron correction approach is employed to create a data relationship mapping model. This model correlates the corrected data on the wheel–rail contact force obtained from the railway inspection car with the wheel–rail contact force of a heavy-haul train with an axle load of 25 tons, and the precision of the mapping is guaranteed. Finally, by combining the wheel–rail contact force correction method for the railway inspection car and the contact force mapping model between the railway inspection car and the heavy-load train, collaborative calibration of the wheel–rail contact force of the heavy-load train is realized. The experimental results under two working conditions show that this method can realize high-precision, real-time measurement of the wheel–rail contact force of a heavy-load train. For the working condition of a straight-line section, the calibration error was within 1.593 kN, and the MAPE was 0.105%; for the working condition of a curved-line section, the calibration error was 2.344 kN, and the RMSE was 184.72 N.