Wheel-rail Contact Research Articles

Investigation on Aerodynamic Fluid–Structure Coupling Vibration of 160 km/h EMU Tail in Single-Track Tunnels

Recently, the phenomenon of tail-sustained swaying of the 160[Formula: see text]km/h EMU in single-track tunnels has gained much attention, especially for the rear-powered vehicle. This phenomenon is investigated from the perspective of aerodynamic fluid–structure coupling vibration in this study. The aerodynamics simulation model of the train in tunnels and the multi-body dynamics model of the rear-powered vehicle were respectively established through the software of XFlow and Simpack, and then the fluid–structure coupling vibration was simulated by using real-time data dynamic exchange between the two models. Moreover, the carbody’s vibration acceleration and the aerodynamic loads acting on the carbody under various wheel–rail contact geometrical conditions were discussed. Finally, the train tail swaying in field was tested, and the dominant frequencies were analyzed. The results show that the periodic aerodynamic loads and the frequency locking effect caused by the coupled vibration are the main factors for ride comfort deterioration. The violent vibration caused by fluid–structure coupling is named vortex-induced vibration (VIV) in some industries such as bridge and submarine pipeline. For the vehicle in this work, with the decrease of equivalent conicity in wheel–rail contact, the amplitude of carbody swaying increases owing to the carbody hunting, which enhances the fluid–structure coupling vibration, and further deteriorates the ride comfort. The swaying of the carbody is dominated by the vehicle hunting frequency, and the improvement of vehicle lateral stability can weaken this phenomenon.

Deterministic Stress Intensity Factor of a Railway Axle under Adverse Running Condition

Although railway axles are a crucial part of railway vehicles, they are susceptible to long-term failure because of repeated loads. The aim of this research is to investigate the stress intensity factor (SIF) of a surface elliptical crack on a high-speed railway axle under various operating conditions. The study employs numerical analysis to explore the impact of press-fitting, rotary bending, stable and adverse running conditions on the SIF solutions. The main findings demonstrate that adverse running conditions, such as the press-fitting force, asymmetric vehicle weight, lateral force and wheel-rail contact force, can significantly increase the SIF values and result in axle failure. The press-fitting effect and rotary bending also have a significant impact on the SIF values, highlighting their importance in the railway axle design and analysis. The outcome of this research emphasizes the significance of accurately estimating SIF values to ensure the safe and reliable performance of railway axles in adverse operating conditions.

Профіль ободу коліс вантажного вагона з перспективними візками для умов спільної експлуатації на українських і європейських залізницях

To solve the important problem of speeding up the integration of Ukraine into the European railway transportation, an interest has recently grown in the introduction of automatic car transfer from one track gauge to another using gauge-changeable wheelsets, thus dispensing with truck exchange or transshipment and thereby significantly shortening the delivery time. However, the combined operation of trains on the Ukrainian (1,520 mm gauge) and European (1,435 mm gauge) railways calls for the compatibility of the wheel-rail contact pair on both railways: R65 rails and a cant of 1/20 in Ukraine and UIC60 rails and a cant of 1/40 in Europe. The goal of this work is to develop a wheel profile for a freight car with prospective 18-7020 trucks for combined operation on the Ukrainian and European railways and predict the ride performance of a car with that wheel profile and its dynamic interaction with rails on both railways. An investigation was conducted into the wheel?rail interaction indices and the ride performance of a freight car with prospective 18-7020 trucks and wheels with existing profiles. It was shown that it is expedient to develop a new wheel profile to improve the service compatibility of the Ukrainian and European networks. A number of new wheel profiles were constructed, the efficiency of each profile in terms of dynamic stability at service speeds and wheel flange wear on the Ukrainian and European railways was calculated, and a compromise profile, ITM-73ES, was chosen. It was shown that the use of the chosen profile in a car with 18-7020 trucks will offer a high dynamic performance and improved indices of wheel?rail interaction for both truck gauges.

Analysis of the wheel-rail dynamic response characteristics and damage to the fixed frog of the No. 3 tram turnout

The tram No. 3 turnout fixed frog uses a variation in the depth of the flange groove so that the wheel rolls over the frog area in a continuous flange bearing. This method of travelling over the turnout requires the wheel load to transition back and forth between the tread and the flange, resulting in wheel-rail impact, which in turn affects service life. In order to investigate its service characteristics, this paper has established a transient wheel-rail rolling contact finite element model for the No. 3 turnout fixed frog. The macroscopic dynamic response and microscopic wheel-rail contact solution as the tram passes through the turnout at different axle weights and speeds are analysed in detail, and the changing patterns of wear and fatigue damage are investigated. The research shows that rail wear is particularly severe in the wheel flange bearing area, approximately 1.6 times greater than in the tread bearing area. In addition, when tram speeds are reduced to 15 km/h, there is a significant reduction in wheel-rail impact and wear, thereby improving ride smoothness and safety. The results of this study are of great significance to the operation and maintenance of the No.3 fixed frog turnout.

Output-only estimation of lateral wheel-rail contact forces and track irregularities

The contact between the wheel and the rail heavily affects the dynamic behaviour of railway vehicles and their running safety. The real-time knowledge of wheel-rail contact forces is tricky due to the several running conditions of the train and the combined tribological and wear characteristics of wheels and rails. Furthermore, their measurement and that of track irregularities, sensitive to the harshness of the wheel-rail contact, require dedicated sensors. Therefore, the development of strategies for estimating wheel-rail contact features is essential to perform the condition monitoring of rails to improve the safety related to the entire railway system. A nonlinear model-based estimation procedure, based on a Central Difference Kalman Filter, is proposed in this work to estimate the lateral wheel-rail contact forces and moments, including the identification of lateral track irregularities in the estimation process related to rails. Furthermore, the developed estimation technique can be used as a tool to monitor continuously the track conditions through in-service railway vehicles, coupled with the possibility to improve the effectiveness of control systems onboard them by estimating wheel-rail contact interactions through a model-based estimator, which is fed by measurements obtained by the typical set of sensors adopted for condition monitoring purposes on railway vehicles.

An approach for the creep-curve assessment using a new rail tribometer

The friction properties of the wheel-rail contact are characterized by a coefficient of traction (CoT), which can be affected by many contaminants. Numerous devices for assessing CoT are available; however, only a small number of them are capable of recording creep curves. This work introduced a rail-mounted tribometer that uses controlled changes in braking torque on a measuring wheel to induce creep in the contact. A methodology for assessing creep curve parameters was proposed, utilizing both analytical and numerical models of the contact. The experiments were performed both in the field and in the laboratory to investigate the effect of railhead conditions under various contact pressures and to track the evolution of the CoT during a measurement.

Research on fatigue evaluation method of high-speed train axle based on axle box acceleration

As a key safety component of the high-speed train, fatigue fracture of the axle would lead to major accidents such as derailment or overturning. The complexity of the axle dynamic stress test seriously enhances the difficulty of axle fatigue damage analysis. In this paper, the dynamic stress test of the high-speed train axle was carried out, the axle box acceleration was monitored on-track during the test, and the relationship between the axle stress spectrum and acceleration was analyzed on-track. The results show that the relationships between the axle equivalent stresses and the Root Mean Square (RMS) values of the axle box vertical acceleration and lateral acceleration exhibit a strong joint probability density distribution. The concept of the virtual surface density of wheel-rail contact is also proposed to realize the purpose of using axle box acceleration to deduce axle equivalent force. The results quantify the relationship between axle box acceleration and axle equivalent force, provide a new method for predicting the axle damage using the acceleration RMS values, and open up a new approach for structural health monitoring of high-speed train axles.

Flanging, squeal and corrugation-induced noise: Insights from recent measurement campaigns at interconnected tight curves

High noise events at tight curves often comprise of squeal, flanging and corrugation-induced noise. All noise types have the potential to cause annoyance at sensitive receivers in close proximity to the rail line. The presence of squeal, flanging and other high noise events at three interconnected sharp passenger curves on the metropolitan network in Sydney, New South Wales is investigated in the context of measured parameters. Rail and noise parameters were measured at ten locations in 2021, with a repeat of the measurements undertaken at three locations in 2022. Differences in high noise events were analysed and quantified to understand the underlying causes of curving noise in this area. The role of the wheel-rail interface contact conditions, train type, rail roughness, friction and speed is investigated to provide insights into the mechanisms leading to curving noise events at this site.

DEM simulation of single sand grain crushing in sanded wheel–rail contacts

In railways, low adhesion conditions lead to problems in braking and traction. Sanding increases adhesion by blasting sand grains towards the wheel–rail contact. Which physical mechanisms increase adhesion during sanding is poorly understood, as research in this field has been almost exclusively experimental. This work is the first step in developing a DEM model describing the sanding process. Previous experimental studies involve single grain crushing tests focusing on initial breakage and repeated breakage under realistic wheel–rail contact pressures of 900 MPa. Tests on two types of rail sand under dry and wet contact conditions, showed different spread of fragments as well as the formation of clusters of solidified fragments at high stresses. The developed DEM model captures the observed behaviour for both types of sand, and both contact conditions. Combining experimental research and DEM modelling aims to improve the understanding of adhesion increasing mechanisms in sanded wheel–rail contacts.

Mindlin cracked plates modelling and implementation in train-track coupled dynamics

Nowadays, the widely constructed ballastless track in high-speed railways will inevitably suffer from localized damage cracks induced by complicate environmental effects, which would change its designed dynamic performance under train dynamic loads and further affect its service life and durability. To this end, a semi-analytical approach of the in-plane and the out of plane forced vibration for Mindlin plates with a side crack are derived, and is further implemented into the train-track coupled dynamic (TTCD) system which comprehensively considering nonlinear wheel-rail contact and 3D spatial flexibility of the cracked track slab. The dynamic partial differential equation of the cracked slab is derived by Hamilton principle and discretized by Galerkin method. Then the eigenvalues and forced vibrations of the cracked slabs for both in-plane and flexural vibrations are tackled utilizing a set of powerful trigonometric modified by special corner function, which can effectively explain the singularity of stress at the crack tip and the discontinuity of deformation on both sides of the crack. The eigenvalue analysis and mode shapes of the cracked plate mode in free boundary condition are compared with the finite element method to verify its accuracy. Meanwhile, the reliability of the proposed dynamics model is verified by comparing with the responses predicted by the co-simulation technology. Finally, the discrepancies of dynamic responses of the track slab with or without a side crack are analyzed, and the effects of various operation speeds and support stiffness on the dynamic behaviour of both slabs are revealed. Results indicates that the track slab with a side crack has significant distinctions on the slab dynamic signals in both time and frequency domains, and the amplitude amplification phenomenon occurs in some specific areas compared with the intact slab; The type-Ⅱ stress intensity factor (SIF) is more sensitive to train speeds, while the support stiffness is highly correlated to all types of SIFs. This work may contribute to the scientific maintenance and health monitoring of high-speed railway tracks.

Effect of rail profile wear on vehicle operation performance in high-speed line

PurposeWith the continuous increase in the operating speed of high-speed trains, the wear and tear of rails on high-speed lines has also gradually deteriorated. At present, the phenomenon of asymmetric wear of rails in high-speed lines is relatively serious. This paper aims to analyze the effect of three typical rail profile wear on vehicle operation performance.Design/methodology/approachTo solve this problem, by analyzing the wheel-rail contact relationship and establishing a vehicle dynamics model, the influence of worn typical rail profiles on the vehicle’s dynamic performance and carbody abnormal vibration is analyzed. Additionally, the effect of worn rail profiles on wheel wear is analyzed using a wear model.FindingsThe results showed that, compared to the standard rail profile, the three typical wear rail profiles show an increase in normal contact stress. The ride and safety indexes of the three rail profiles also increased compared with the CHN60 profile. The rail Profile 3 does not affect carbody vibration, while Profile 1 and Profile 2 can cause hunting vibrations of the carbody, with the main vibration frequencies around 7 Hz. The wheel wear depths under three typical rail profiles are 1.185 mm, 1.11 mm and 1.058 mm.Originality/valueThe effect of the measured typical rail profiles on the vehicle’s performance is analyzed, particularly in terms of abnormal vibrations and wheel wear. This analysis can provide guidance for the long-term maintenance of the rail system.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2023-0270/

Suppression of carbody hunting for a locomotive caused by low wheel–rail contact conicity by optimising yaw damper location

This study addresses the issue of carbody hunting in an electric locomotive induced by low wheel-rail contact conicity. The main objective is to mitigate this unstable motion by optimising the location of yaw dampers while ensuring bogie stability under high conicity conditions. A field test was first conducted to observe the carbody hunting behaviour, and a detailed locomotive dynamics model was then developed and validated using experimental data. The impact of yaw damper locations on locomotive stability was investigated, taking into consideration different carbody modes. The findings reveal the mechanism behind the deterioration of carbody stability due to the yaw damper installation angle and two installation layouts were proposed to enhance the carbody stability. Comparisons were then made with traditional solutions using both linear and nonlinear analysis, and experimental validation confirmed the effectiveness of the optimised yaw damper locations in improving carbody stability. This research highlights the importance of optimising the yaw damper's location to suppress carbody hunting, providing valuable insights for railway engineers and offering a promising solution for enhancing stability in high-speed train.

Influence of rail side lubrication and slip rate dependent effects upon the corrugation on the metro small curve track

For investigating the rail corrugation characteristics of metro small curve track under the combined effect of rail side lubrication and slip rate dependence, by developing a three-dimensional vehicle-track coupling numerical model, the wheel-rail (WR) contact stick-slip (SS) characteristics under different transition areas of rail side lubrication in the presence of corrugation were analyzed. Meantime, on the basis of considering the friction slip rate dependence, the SS vibration characteristics under different rail side lubrication conditions were further analyzed to understand the effect mechanism of rail surface friction characteristics on corrugation. The results show that, when there is rail side lubrication, both inner and outer WR systems have the possibility for SS vibration, and the longitudinal SS vibration intensity is greater than the transverse SS vibration intensity; the SS vibration intensity of the inner WR system is greater than that of the outer WR system, indicating that the inner rail is more susceptible to corrugation and the corrugation is more acute. With the expansion of the rail side lubrication range, the standard deviations of longitudinal and transverse adhesion coefficients decrease, illustrating that the expansion of the lubrication range can reduce the SS vibration intensity of WR system. When the co-effects of rail side lubrication and slip rate dependence are considered, the increase of the rail side lubrication range leads to the increase of standard deviations of adhesion coefficients, which may be related to the enhancement of slip effect induced by the increase of the lubrication range. The introduction of slip rate dependent effect can reduce the standard deviation of the WR adhesion coefficient, which demonstrates that the slip rate dependent effect can ease the degree of SS vibration of WR system, thus reducing the probability of corrugation occurrence caused by the SS vibration.

Investigation of dynamic gauge widening in small radius curves and its impact on lateral wheel-rail contact forces

In this paper, the lateral interaction between a rail vehicle and the track is investigated during cases of an occurrence of dynamic gauge widening. This is composed of the nominal track gauge, wear of the rail profiles and track widening due to wheel-rail forces on sections of curved track. A multibody simulation model is used to investigate the various influencing parameters. This model not only analyses the single rail’s lateral displacement but also tilting. Furthermore, the simulation of rail pads with adjustable stiffnesses is enabled. The resulting different contact points between the wheel and rail are represented, affecting the wheel-rail contact forces. The results reveal that changes in contact geometry caused by rail tilting depend strongly on the specific wheel and rail profiles. This is illustrated by comparing a new rail profile with a heavily worn rail profile. Particular attention is also paid to the distinction between leading and trailing wheelsets. Finally, the model is validated using measured wheel-rail forces and rail head movement, as measured on the track. A better understanding of dynamic track widening can improve the running behaviour of the wheelset on small radius curves, help protect against derailment and reduce wear on the wheel and rail.

Impact of wheel profile evolution on the lateral motion characteristics of a high-speed vehicle navigating through turnout

The wheel-rail contact asymmetry on the left and right sides of the wheelset while navigating high-speed vehicles through turnouts can lead to lateral motion of the wheelset, ultimately resulting in substantial vibrations in the vehicle system. This study employs the trace method to examine the changing pattern of the wheel-rail equivalent conicity in the turnout area as the wheel profile evolves. A coupled system dynamics model containing flexible turnouts is established. Specifically, the model examines the lateral position of wheel-rail contact points, the lateral motion of the wheelset, and the lateral vibration acceleration of the vehicle system. The study indicates that the lateral motion characteristics of high-speed trains passing through turnouts are influenced by the degree of wheel wear. When the wheels are slightly worn (for mileage below or equal to 100,000 km), the lateral dynamic responses of the vehicle system are affected by the inherent structure of the turnout. When the wheels are severely worn (for mileage above or equal to 150,000 km), the lateral dynamic response of the vehicle system is no longer affected by the inherent structure of the turnout.

Effect of Cyclic Loading on the Surface Microstructure Evolution in the Pearlitic Rail

The effects of cyclic loading on the surface microstructure evolution of different contact locations in a used pearlitic rail were studied. Microstructures were analyzed using Scanning Electron Microscopy (SEM). Meanwhile, grain boundaries and crystallographic orientations were explored via Electron Backscatter Diffraction (EBSD). At last, wheel–rail contact probabilities and forces were calculated using rail profiles. The results indicate that the side wear region located in the gauge face was 71.5% in the high-angle grain boundaries (HAGBs) fraction, 0.88 in the Kernel Average Misorientation (KAM) value, 36% in the recrystallization (REX) fraction, and had a predominant orientation in grains. The rolling contact fatigue (RCF) region situated at the gauge corner was 66.3% in the HAGBs fraction, 0.92 in the KAM value, 33% in the REX fraction, and was mis-orientated in grains. The region located at the edge of the running band was 60.7% in the low-angle grain boundaries (LAGBs) fraction, 0.97 in the KAM value, 12% in the REX fraction, and was mis-orientated in grains. Continuous dynamic recrystallization (cDRX) took place in wear and RCF regions during the cyclic rolling contact loading, creating ultra-fine grains with a transformation from LAGBs to HAGBs, lower KAM values, and more REX. Grains oriented along [111] parallel to the vertical direction in the wear region were influenced by the dominant normal force, while grains in the RCF region were non-oriented, which was attributed to large lateral and vertical forces of similar magnitudes.

Experimental Study and Phenomenological Laws of Some Nonlinear Behaviours of the Wheel–Rail Contact Associated with the Deshunting Phenomenon

A widely used technique for locating the position of a train during its journey involves electrical detection: on a section of track, the train closes (“shunts”) a circuit dedicated to its location via its wheels and axles. The quality of the wheel–rail contact is therefore particularly important for signalling management and traffic control. In this paper, we show that the current flowing through the track circuit induces a permanent modification and a nonlinear, frequency-dependent behaviour of the electrical contact. We propose an analytical expression that describes the evolution of the measured voltage as a function of current and frequency for these nonlinear behaviours. This behavioural law was obtained using experimental measurements on a real train and could therefore be integrated into a global model describing the track system.

Evolution of microscopic characteristics of rolling contact fatigue coexisting with wear of U75V rail

During the damage and defects related to rolling contact fatigue (RCF), together with wear occurring at the rail surface, the microscopic characteristics of the rail material change with the accumulation of wheel cycles. To find the relationship between rail material characteristics and RCF damage under wheel-rail contact situations, a series of twin-disc rolling-sliding tests, based on real wheel-rail contact situations at a radius of 80 mm rail profile, was established for a heavy-haul railway in China. The microscale characteristics of the rail disc contact surface was researched, including crack, wear, roughness, and hardness of the U75V rail with different load cycles. The results show that the damage mechanism of RCF and wear alternately dominates the rail disc surface at the microscale, taking a certain cycle as a boundary which makes the RCF crack number and wear rate have opposite evolutionary trends. The above factors also affect the wear at the surface rail discs, alternating between fatigue and adhesion. Meanwhile, increasing the surface micro-hardness leads to a decrease in the relative wear rate and an increase in the roughness, length and number of RCF cracks. The plastic deformation layers, including the severely deformed layer (SDL) and the transition layer (TL), almost maintain the same thickness and the dynamic equilibrium increases during the cycles. Two kinds of cracks are initiated and propagated at the rail disc surface, one at the SDL and the other at the junction of SDL and TL. The number of each kind of crack depends on the SDL thickness.

Effectiveness of Tap Water in Reducing the Generation of Ultrafine Wear Particles from the Wheel-Rail Contact by Eliminating the Water Vapor Effect.

This study aimed to assess the impact of tap water application on reducing the generation of ultrafine particles from the wheel-rail contact using a twin-disk rig under dry and wet conditions, with train velocities of 45 and 80 km/h. A small amount of 0.3 L/min tap water was applied at the wheel-rail contact, and a diffusion dryer was used to eliminate water vapor. The Fast Mobility Particle Sizer measured the number concentration (NC) of nano-sized wear particles in the range of 6 to 560 nm. The tap water application method effectively reduced the NC of ultrafine and fine particles by 67-72% and 86-88%, respectively. Positive reduction rates were observed for all diameters at 45 km/h and for most diameters, except for approximately 70 nm and 80 nm, at 80 km/h. Even with a small amount of water, this approach successfully decreased nano-sized wear particle generation. However, the potential influence of mineral crystals in tap water on NC requires further investigation. Overall, this method shows promise for enhancing air quality and public health by mitigating nano-sized wear particle generation in subway systems.

Optimisation design of grinding rail profile of metro lines for small radius curved track based on the GFC method: a case study

The rail side wear in small radius curved track of metro lines is a serious problem in railway maintenance, which reduces the curve passing performance and shortens the service life of the wheel and rail. To improve the vehicle's curve passing performance and reduce rail wear, a localized grinding profile design method for sharp curves was developed. The GFC profile generation method was used to generate the profiles for the curved track of the metro line. Then a metro vehicle-track dynamic model was established to calculate the wheel rail contact parameters, objectives and constraints. The profiles are optimized by the KSM-PSO optimization algorithm. Finally, a simulation analysis of the curve passing performance and wheel-rail wear of the optimized profile was carried out. When the metro vehicle passes through the curved track with a curve radius of 450m, the optimized rail profile can effectively reduce the wear of the rail, the wear of the high rail in the curved track is reduced by 20.18%. The localized rail grinding of the curved track can effectively reduce the rail side wear, the GQI index is also significantly improved. This study can guide the design of rail grinding profiles for the metro lines.