Wheel Rail Research Articles

Effects of various laser cladding materials on the tribological properties of damaged wheel treads under various temperatures and humidities

Laser cladding technology is used to repair damaged wheels and plays an important role in prolonging their service life. Additionally, the temperature and humidity of the environment have important effects on the operation of the repaired wheels. In this study, widely used 316L and 420 stainless steel alloy powders were selected as cladding materials, and three environmental conditions (25℃-RH60%, 50℃-RH60%, and 50℃-RH90%) were set according to changes in temperature and humidity in different areas of China. Friction and wear tests were performed under different temperature and humidity conditions on a damaged wheel after local repair by laser cladding. The results clearly show that there are demarcated equiaxed and directional columnar grain regions in the 316L cladding, whereas there are uniform plate and strip martensite structures in the 420 cladding, which are well formed by the metallurgical bonding of the wheel substrate. From 25℃-RH60% to 50℃-RH90%, the friction coefficient, plastic deformation thickness, and wear rate of the wheel–rail tended to decrease. However, the wear rates of the 420-coated wheels increased as the environmental conditions increased from 25°C-RH60% and 50°C-RH60%, and the wear rates of the corresponding rail samples remained high. The main forms of surface damage are fatigue cracks and material spalling. With increasing temperature and humidity, the damage to the bonding zone between the cladding and substrate surface decreases. The damage to the cladding profile is caused mainly by cracks at different angles and spalling pits. In the 25°C-RH60% environment, cracks initiate in the profile of the bonding zone and propagate along the plastic rheological line to the interior of the material. In comparison, the locally repaired wheel with 316L stainless steel alloy powder as the laser cladding material has better tribological properties and is more suitable for repairing damaged wheels.

Parameter influence analysis and optimization of wheel–rail creepage characteristics in high-speed railway curves

Parameter influence analysis and optimization of wheel–rail creepage characteristics in high-speed railway curves

Development of a Scaled-Down Test Rig for Wheel–Rail Contact Thermal Experiments Using Optical Sensors

Abstract Rail–wheel contact measurement is crucial for several reasons. First and foremost, it directly affects the safety of passengers, crew, and the general public. Accurate measurements help identify irregularities in wheel–rail contact, such as wheel defects, wear, or track anomalies, which can lead to derailments or accidents if left unaddressed. An inventive technique for measuring the temperatures at rail–wheel contact at various speeds is presented in this research. The novel approach uses a 1:5 scaled-down test rig model of a wheel and rail with a fiber Bragg grating (FBG) sensor to combine the experimental and finite element analysis simulation to determine the rail–wheel contact temperature. By employing the various data acquisition and data analysis techniques, rail–wheel contact temperature at different speeds ranging between 10 kmph and 40 kmph was determined 1538.735–1538.831 nm with a center wavelength of 1538.438 nm. The results illustrate the possibilities of the downsized test rig with experimental observations at varying speeds by examining the benefits of FBG sensors over traditional sensors. The experimental results are used to determine the equivalent wavelength shift. FBG sensor design and simulation are done with the grating modulation depth (MOD) optical tool. For this temperature range and Bragg's wavelength of 1538.438 nm, the sensitivity of fiber Bragg grating is observed to be 13.6 pm/°C.

Measurement of dynamic characteristics of a steel-spring floating slab track and a monolithic roadbed track in a subway tunnel

ABSTRACT Dynamic characteristics including wheel–rail interactions and vibration-damping effects of a steel-spring floating slab track were measured and compared with those of a monolithic roadbed track. These two tracks are in the same subway tunnel, and with similar conditions. Measuring results show that the vertical and transverse wheel-rail forces on the floating slab track were separately 8% and 47% larger than those on the monolithic roadbed track. Due to the increased quasi-static wheel-rail forces, vertical and transverse rail deformations on the floating slab track were separately 2.5 and 4 times larger than those of the monolithic roadbed track. Based on the measured acceleration vibration levels, the vertical and transverse vibrations of the tunnel wall of floating slab track were 5 dB smaller than those of the monolithic roadbed track. Meanwhile, the vibrations of the floating slab were 10 dB larger than those of the monolithic roadbed. Therefore, the floating slab effectively blocked vertical and transverse energy transmissions. Based on the measured frequency-division vibration levels, vertical and transverse resonant vibrations of the tunnel wall of floating slab track were 15–22 dB smaller than those of monolithic roadbed track. However, low-frequency wheel-rail forces increased vibrations from 1 to 20 hz, which may have a negative influence on soil ground vibrations.

Runability Analysis of the New Storstrøm Bridge Due to Wind Action and Ship Impacts

In the process of designing long span bridges, runability analysis plays an important role. In fact, it deals with the assessment of the impact on the structure’s response and train running safety of external factors such as environmental actions, like wind and earthquake, or catastrophic events like ship impact. Runability analysis involves a combination of local aspects (e.g. wheel–rail interaction) with global and local bridge dynamic response. In this respect, runability analysis represents a complex task to be tackled and requires adequate modelling. The present work proposes a runability study to be performed on the New Storstrøm Bridge, which is currently under construction in Denmark connecting Zealand with Falster. In this numerical analysis. two scenarios have been considered separately: ship impact on the bridge’s superstructure and wind action on a rail vehicle, using both the “Chinese hat” and stochastic turbulent wind formulations. The outcomes of this study clearly show that, even when threshold values were locally reached in terms of train running safety, a close examination of the local wheel–rail contact condition helps in defining the expected evolution of the dynamics of the train and thus documenting a higher safety level than indicated by the basic requirements.

CFD–DEM modelling of particle entrainment in wheel–rail interface: a parametric study on particle characteristics

Abstract To mitigate and alleviate low wheel–rail adhesion, a train-borne system is utilised to deposit sand particles into the wheel–rail interface via a jet of compressed air in a process called rail-sanding. Britain Rail Safety and Standards Board introduced guidelines on the sand particles’ shape, size, and uniformity which needs to be adhered to for rail-sanding. To further investigate these guidelines and help improve them, this research presents a parametric study on the particle characteristics that affect the rail-sanding process including density, size and size distribution, coefficient of uniformity, and shape, utilising a coupled computational fluid dynamics–discrete element method (CFD–DEM) model. The efficiency of rail-sanding is estimated for each case study and compared to the benchmark to optimise the sand characteristics for rail-sanding. It is concluded that particle size distribution (within the accepted range) has an insignificant effect on the efficiency while increasing particle size or the coefficient of uniformity decreases the efficiency. Particle shape is shown to highly affect the efficiency for flat, compact and elongated particles compared to the spherical shape. The current numerical model is capable of accurately predicting the trends in the efficiency compared to the actual values obtained from full-scale experiments.

Modelling and application of yaw damper with frequency-selective damping on railway vehicles

In this study, a new mechanical yaw damper with frequency-selective damping (FSD) is investigated. The structure principle, modelling and simulation of the damper and its core component, the frequency-selective damping valve, are elaborated. Compared with the conventional damper, the static and dynamic characteristics of the FSD damper have been tested in the experimental bench, and the damping variation rate is proposed to evaluate the damping force variation. A physical parameter model of the yaw damper is established by using the AMESim software, and the simulation accuracy has been verified by comparing the simulated results with the experimental ones. A detailed analysis has been performed for the influence of key parameters of the FSD valve on the mechanical characteristics of the FSD damper. Finally, through the AMESim/Simpack co-simulation method, the dynamic performances of a high-speed locomotive equipped with the FSD yaw damper have been simulated. The results indicate that the FSD yaw damper improves the adaptive stability of railway vehicles in different wheel–rail matching states. In addition, the dynamic performance of the vehicle can be improved when passing through the turnout and narrow curves.

Fatigue Crack Propagation Analysis of Rail Surface Under Mixed Initial Crack Patterns

Prolonged rolling contact fatigue between wheels and rails results in the formation of surface cracks on the rail and accurately analyzing the crack expansion behavior is essential to ensuring the safe operation of the train. Drawing upon the principles of fracture mechanics and finite element theory, this study establishes a finite element model of wheel–rail rolling contact that incorporates the presence of cracks. The method utilizes an interaction integral to calculate the stress intensity factors at the leading edge of the crack; then, the Paris formula is used to solve the crack spreading rate. It systematically examines the effects of the initial crack angle, the coefficient of friction of wheels to rails, and crack size on the behavior of fatigue crack propagation. The results indicate that the cracks primarily extend in the depth direction of the rail, transforming the semi-circular surface cracks into elliptical cracks with the major axis oriented along the rail’s width. Crack propagation is primarily driven by model II and III composite crack propagation, with their expansion rates influenced by operating conditions. In contrast, mode-I expansion is less sensitive to these conditions. Under single-variable loading conditions, a smaller initial crack angle results in a faster crack growth rate. Increasing crack length accelerates crack growth, while a higher friction coefficient inhibits it.

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.