Wheel Rail Research Articles

An implicit 3D corotational formulation for frictional contact dynamics of beams against rigid surfaces using discrete signed distance fields

The interaction of beam-like structures against surfaces is a challenging problem with applications in engineering (wheel–rail contact, pipeline–soil interaction, ropes sliding on the seabed) and in medical applications such as surgical planning and training (catheter navigation, aneurysm coiling, stent deployment). This contact problem is traditionally solved using Total Lagrangian beam formulations, which interact against Lagrangian triangulated surfaces. Overall, the computational speed is affected, due to the nonlinearities of the beam formulation and, as well as due to the expensive search algorithms, required to find the close point projection. In the search towards an efficient beam to surface contact algorithm, this paper explores the combined use of (1) a corotational beam formulation, where the motion of the beam element is decomposed in rigid body and pure deformational parts and (2) an implicit description of the surface by means of discrete signed distance fields (SDF), which can be seen as a Lagrangian beam immersed within an Eulerian (rigid) solid. To do so, a previously reported implicit corotational formulation for beam dynamics is modified to account for frictional contact, by means of a penalty term. The new contributions are fully linearized to update the tangent operator and the system is integrated in time by means of the HHT-α method. Overall, a consistent implicit contact dynamics formulation is provided. A SDF, defined in a voxel-type grid, is used to represent implicitly the surface geometry. The SDF values and derivatives are computed at the Lagrangian point of integration of the beam by means of an efficient tensor product of compact, high order, 1D Kernels, as widely used in immersed Fluid–Structure Interaction techniques. A wide variety of validation tests are presented which prove the accuracy and robustness of the proposed algorithm.

МЕТАЛЛОПЛАКИРОВАНИЕ РАБОЧИХ ПОВЕРХНОСТЕЙ ТРЕНИЯ ПАРЫ “КОЛЕСО — РЕЛЬС” МЕТАЛЛОПЛАКИРОВАНИЕ РАБОЧИХ ПОВЕРХНОСТЕЙ ТРЕНИЯ ПАРЫ “КОЛЕСО — РЕЛЬС”

МЕТАЛЛОПЛАКИРОВАНИЕ РАБОЧИХ ПОВЕРХНОСТЕЙ ТРЕНИЯ ПАРЫ “КОЛЕСО — РЕЛЬС” МЕТАЛЛОПЛАКИРОВАНИЕ РАБОЧИХ ПОВЕРХНОСТЕЙ ТРЕНИЯ ПАРЫ “КОЛЕСО — РЕЛЬС”

Wheel–rail stochastic dynamics and rail wear analysis of small radius curved sections of a tram line based on generalized probability density evolution

Compared with ordinary railways, the curve radius of tram lines tends to be smaller, with minimum values of only 30 m. Therefore, wheel–rail interaction is more intense and complicated in sections of small radius tram line curves. Using a stochastic variable sample set based on a generalized probability density evolution method, the stochastic variable–spectrum representation method was used to generate a time-domain sample set of stochastic track irregularities. By inputting the stochastic set of track irregularities into a tram-track coupled dynamic system model, the stochastic dynamic response of the coupled dynamic system can be obtained. Moreover, by substituting the stochastic dynamic system response into the generalized probability density evolution formula, the process of probability density evolution of each evaluation index can be obtained by the finite difference method. Finally, the dynamic response of the tram-track coupled dynamic system can be evaluated by the probability distribution of each index. By setting a series of specific groove rail wear values, a tram-track coupled dynamic analysis was carried out, and compared with the specification requirements, vehicle safety limits under different wear values were obtained. This research has great engineering value for guiding the routine maintenance of small radius curve sections of trams.

Geospatial and temporal data mining to combine railway low adhesion and rail defect data

Rolling contact fatigue (RCF) damage to rails and low adhesion at the rail–wheel interface remain significant problems in maintaining railway performance, fully utilising network capacity and reducing running costs. A novel approach has been developed to understand these problems through analysis of data on RCF and low-adhesion incidents from the UK rail network. This augments understanding of specific mechanisms such as the roles of rail plasticity in crack initiation and environmental moisture levels in low adhesion, which have not given sufficient information to prevent these problems to date. A moving-window filtering technique and temporal and geospatial approaches were used to identify correlations between sites of low rail–wheel adhesion subject to transient sliding contact, crack initiation and underbridge locations where vertical and lateral track stiffness typically change rapidly. The analysis showed that a high density of otherwise unexpected RCF defects occurred close to underbridges and that there was a strong correlation between momentary slides during braking and RCF sites. The temporal analysis indicated that, although concentrated in the autumn period, 55–60% of transient low-adhesion incidents occur outside that period, with the highest risk in the very early morning.

Simulation of vertical dynamic vehicle–track interaction using a three-dimensional slab track model

When improving track design, a better understanding of the track’s damage modes is needed, and the railway industry is then dependent on the availability of accurate simulations of the dynamic vehicle–track interaction. In the present study, the vertical dynamic interaction between a travelling railway vehicle and a slab track is simulated in the time domain by using an extended state-space vector approach. A three-dimensional slab track model is launched where the rails are modelled using Rayleigh–Timoshenko beam elements and the concrete panel and roadbed are represented by using either shell or solid finite elements. From the parameterised track model, which is developed in Abaqus using Python scripts, the system matrices are exported to Matlab where the simulation of the dynamic vehicle–track interaction is performed. A complex-valued modal superposition technique is employed, which reduces the computational cost of the simulation. In a post-processing step, calculated wheel–rail contact forces from the dynamic analysis are used as input to the Abaqus track model where various track responses are evaluated. In particular, the time history of principal stresses is determined at critical locations in the concrete panel. Also the influence of the speed of the vehicle on the wheel–rail contact forces, and the influence of a transverse culvert below the track (modelled as a local increase of the foundation bedding modulus) on the track stiffness variation at the rail level, are investigated. A mesh convergence study for a range of track responses has been conducted including investigations of when to use linear or quadratic elements and shell or solid elements. Finally, the presented three-dimensional models have been compared to an alternative two-dimensional model to determine in what situations a two-dimensional model is sufficient.

Wheel profile optimisation for mitigating flange wear on metro wheels and verification through wear prediction

Metro trains often encounter the problem of wheel flange wear when they pass through sharp curves, especially for the poor wheel–rail profile matching or lack of lubrication, evidently increasing the maintenance and replacement costs for wheelsets and rails. Based on the field investigation and numerical simulation, the cause of severe flange wear of the original S1002 wheel profile on a Chinese metro line is analysed. An optimised wheel profile is proposed according to the rolling radius difference (RRD) for improving vehicle curving performance and mitigating wheel flange wear. A wheel wear prediction model is developed by combining the metro vehicle dynamics model considering multipoint contact with the long-term wear simulation model, and then validated with the field measurement results. The performance of the optimised wheel profile is evaluated numerically. The results indicate that the root cause of the wheel flange wear is the improper matching of wheel and rail profiles. The optimised wheel profile generally proves to perform better in terms of wheel–rail contact geometry, mechanical properties, vehicle running stability, curving negotiation and wear performance. The wheel flange thickness loss of the optimised wheel profile is decreased by 55.7% compared with that of S1002 profile.

Optimizing rail profiles to improve metro vehicle-rail dynamic performance considering worn wheel profiles and curved tracks

The LM wheel profile and profile of Chinese 60 kg/m rail (LM&CHN60) are commonly used in the Chinese metro. However, the poor matching between wheel and rail profiles as well as the instability of the vehicle often occur on some curved sections due to wear. Therefore, it is necessary to design compatible rail profiles for the worn wheel profiles as a replacement for the old rail in these sections. This paper first presents the analysis of using the worn wheel and rail profiles as well as LM&CHN60 with a three-dimensional vehicle-track coupled model. Then, an optimization of the rail profiles for the worn wheel profiles is implemented in terms of both worn and unworn profiles, which is not only to improve the stability of the vehicle but also to minimize the rail wear by taking the curve performance into consideration. An inverse design method is proposed for rail profile design to improve the wheel–rail contact properties. Then, the wear of the optimized rail profiles is calculated with two types of track, which is the basis for selecting the optimal profile of a specific curve. Furthermore, the evaluation of the vehicle-track dynamic behavior with optimum rail profiles is also performed by comparison with the worn rail profiles. The entire design process is completed in a procedure programmed in MATLAB. The application of the optimized rail profiles significantly slows down the growth rate of rail wear. Additionally, the maintenance intervals for rail reprofiling have been doubled.

Optimization of ER8 and 42CrMo4 Steel Rail Wheel for Road–Rail Vehicles

Railway track maintenance services aim to shorten the time of removing failures on the railways. One of the most important element that shorten the repair time is the quick access to the failure site with an appropriate equipment. The use of road-rail vehicles is becoming increasingly important in this field. In this type of constructions, it is possible to use proven road vehicles such as self-propelled machines or trucks running on wheels with tires. Equipping these vehicles with a parallel rail drive system allows for quick access to the failure site using both roads and railways. Steel rail wheels of road-rail vehicles are designed for specific applications. Since the total weight of vehicle is a crucial parameter for roadworthiness, the effort is made to minimize the mass of rail wheels. The wheel under consideration is mounted directly on the hydraulic motor. This method of assembly is structurally convenient, as no shafts or intermediate couplings are required. On the other hand, it results in strict requirements for the wheel geometry and can cause significant stress concentration. Therefore, the problem of wheel geometry optimization is discussed. Consideration is given to the use of ER8 steel for railway application and 42CrMo4 high-strength steel. Finite element analysis within Ansys software and various optimization tools and methods, such as random tool, subproblem approximation method and first-order method are applied. The obtained results allow to minimize the rail wheel mass with respect to the used material. Moreover, computational demands and methods leading to the best results are compared.

Metal Plating of Friction Surfaces of the “Wheel–Rail” Pair

It is shown that in conditions of significant increase of railway transport speeds, requirements for the safety of the friction–mechanical “wheel–rail” subsystem are increased. In order to solve the above problem, a method is proposed for metal plating “wheel–rail” friction surfaces by applying thin films of soft metal, for example, aluminum, with different values of hardness, on surfaces of rolling wheels and wheel ridges of locomotives. On the basis of quantum-chemical calculations, it has been proved that metal plating of the friction surfaces of the “wheel–rail” system provides a chemical bond between wheel steel and aluminum and the formation of a strong protective film. The performed bench tests of the “wheel–rail” model friction subsystem by methods of tribospectration identification of friction processes and dynamic monitoring of changes in elastic-dissipative bonds confirmed the formation of stable dynamic bonds in friction contact. The results of the research formed the basis of the creation of the algorithm of axial control of “wheel–rail” interaction processes at realization of forces of longitudinal and transverse creep, as well as at optimization of modes of vibrodynamic metal plating working surfaces of other tribosystems, of vehicles operating in heavy load–speed conditions of operation.

Finite Element based Crash and Impact Analyses of a Newly Developed Road Cum Rail Vehicle

"The two most significant engineering steps required in developing a good quality vehicle is crash and structural analysis in the field of automobile design. Simulating the crashworthiness of the vehicle is a significant step to design automobiles of the present age and automotive industry has probably the widest application of such simulations. Crash simulation is a virtual representation of a destructive crash test of a vehicle and its components using computer-aided analysis software to examine the level of safety of the vehicle and its occupants by analysing the level and nature of impact stresses occurring in the component and the magnitude and nature of the deformation happening in the cosmponent during a crash situation. In the current study, a road cum rail vehicle is designed. The main purpose of the vehicle is to clean the rail track. Since the vehicle will be used on the live rail track so it is very important to know the dynamic behaviour of the vehicle during crash or impact. The dynamic behaviour of complete vehicle chassis with four rail wheel and for rubber wheel in contact with rails and moving at 60 km/hr is simulated under frontal crash. Further, 10g frontal impact and the 5g rear impact are also applied on the developed vehicle chassis at rest to investigate its dynamic behaviour"

Application and Experimental Validation of a Multibody Model with Weakly Coupled Lateral and Vertical Dynamics to a Scaled Railway Vehicle.

In this paper, a multibody dynamic model of a railway vehicle that assumes that vertical and lateral dynamics are weakly coupled, has been experimentally validated using an instrumented scaled vehicle running on a 5-inch-wide experimental track. The proposed linearised model treats the vertical and lateral dynamics of the multibody system almost independently, being coupled exclusively by the suspension forces. Several experiments have been carried out at the scaled railroad facilities at the University of Seville in order to test and validate the simulation model under different working conditions. The scaled vehicle used in the experiments is a bogie instrumented with various sensors that register the accelerations and angular velocities of the vehicle, its forward velocity, its position along the track, and the wheel–rail contact forces in the front wheelset. The obtained results demonstrate how the proposed computational model correctly reproduces the dynamics of the real mechanical system in an efficient computational manner.

The refined strength calculation and optimization of the inner geometry of cylindrical bearing units

Closed bearing units for railway rolling stock shall operate over 800,000 km or during 8 years of operating life (and, in the near future, 1 million km and 10 years) without any maintenance. In order to achieve such high operational indicators, it is necessary, already at the design stage of closed bearing units, to ensure almost absence of wear during the entire specified operating life. This paper reports the results of the optimal design of the elements in the internal geometry of closed bearings based on refined mathematical models using an example of the cylindrical axlebox bearing unit DUPLEX for 1520 gauge rolling stock. The chosen principal mathematical model was a geometrically nonlinear contact problem from the theory of elasticity, which was solved using a finite element method. An original non-linear finite-element model of the multi-contact problem has been developed, taking into consideration the contact deformations rail‒wheel, the deformation of a wheel-set axis, the deformation of the axlebox and bearing rings during contact with all rollers. The model makes it possible to clarify the distribution of loads in the circumferential direction and, accordingly, the maximum load on a roller. The same model could be used, among other things, to analyze the wear of a wheel flange and the effect of gap difference on the bearing wear. A mathematical model and an objective function have been constructed to optimize the profile of a roller (crown, the generatrix of the lateral surface of rotation) considering the accumulation of damage as a result of the irregular loading the roller surface points due to contacts with both the outer and inner rings. The shapes of the roller's face and the ring's operating flange have been optimized that are in contact in the axial direction, which has helped establish that the anthropologically shaped convex face of the roller and the concave flange of the ring are optimal. To simplify the structure technologically, a variant with a conical surface of the flange with the optimal camber value has been accepted instead of the concave flange of the ring

Research on coupled vibration of wheel–rail beam system in the high-speed quayside container crane

This article presents a method to achieve the vibration response of wheel–rail beam system on the container crane and to reduce the vibration and improve the trolley speed. To investigate the coupled vibration of a trolley–beam dynamic system, the governing equation is excited to obtain the interaction during the trolley travel on the beam at high speed. We studied the wheel–rail beam system in the container crane and as the structure of the container crane is huge, its beam span is more than 80 m long, the trolley runs on the large elastic beam, the beam deformation will have a significant impact on the structure. The dynamic load produced by the trolley acts on the elastic rail of the beam, which makes major deformation and vibration of the beam. To achieve the procedure of large steel structure on coupling vibration response on the container crane, the model of trolley–beam coupling of large-span elasticity beam with finite element methods and using multi-body dynamic simulation is built. Analysis of trolley–beam coupling is made based on the crawl impact of trolley. We found that the trolley with the elastic wire rope has a real-time dynamic loading effect and it changes the coupled vibration features in the operation. Via analysis on crane vibration of different trolley speed and simulation, the actual artificial frame wave is obtained. The excitation response amplitude by horizontal load has been obtained and it has great effect on the transmissibility performance of the container crane. This study shows that the vibration of the wheel–rail beam system cannot be neglected when increasing the trolley speed on the crane. The vibration response features of partial impact on ground point are done when trolley is running. The measures had been found to reduce the vibration of the container crane operating at high speed.

A framework combining pseudo-excitation method and two-and-a-half-dimensional finite element method for random ground vibrations induced by high-speed trains

A framework is developed in this article to predict the nonstationary random ground vibrations induced by high-speed trains, by combining the pseudo-excitation method with the two-and-a-half-dimensional finite element method. This development contains two steps. First, the power spectral density of the wheel–rail dynamic force is accurately obtained through the combination of the pseudo-excitation method and a vehicle–slab-track–ground theoretical model. Second, the nonstationary random ground vibrations are efficiently solved by combining the pseudo-excitation method and the two-and-a-half-dimensional finite element method, where the power spectral density of the wheel–rail dynamic force obtained in the former step is used to constitute the pseudo-loads. In the numerical examples, the accuracy and efficiency of the proposed approach are validated through the comparison to the fast three-dimensional random method for train–track–soil system developed previously. The results show that the proposed approach can predict the train-induced random ground vibrations with sufficient accuracy and has three-to-five times increase in efficiency in comparison to the fast three-dimensional random method.

Characteristics and toxicological effects of commuter exposure to black carbon and metal components of fine particles (PM2.5) in Hong Kong

Epidemiological studies have demonstrated significant associations between traffic-related air pollution and adverse health outcomes. Personal exposure to fine particles (PM2.5) in transport microenvironments and their toxicological properties remain to be investigated. Commuter exposures were investigated in public transport systems (including the buses and Mass Transit Railway (MTR)) along two sampling routes in Hong Kong. Real-time sampling for PM2.5 and black carbon (BC), along with integrated PM2.5 sampling, were performed during the warm and cold season of 2016–2017, respectively. Commuter exposure to BC during 3-hour commuting time exhibited a wider range, from 3.4 to 4.6 μg/m3 on the bus and 5.5 to 8.7 μg/m3 in MTR cabin (p < .05). PM2.5 mass and major chemical constituents (including organic carbon (OC), elemental carbon (EC), and metals) were analyzed. Cytotoxicity, including cellular reactive oxygen species (ROS) production, was determined in addition to acellular ROS generation. PM2.5 treatment promoted the ROS generation in a concentration-dependent manner. Consistent diurnal variations were observed for commuter exposure to BC and PM2.5 components, along with cellular and acellular ROS generation, which marked with two peaks during the morning (08:00–11:00) and evening rush hours (17:30–20:30). Commuter exposures in the MTR system were characterized by higher levels of PM2.5 and elemental components (e.g., Ca, Cr, Fe, Zn, Ba) compared to riding the bus, along with higher cellular and acellular ROS production (p < .01). These metals were attributed to different sources: rail tracks, wheels, brakes, and crustal origin. Weak to moderate associations were shown for the analyzed transition metals with PM2.5-induced cell viability and cellular ROS. Multiple linear regression analysis revealed that Ni, Zn, Mn, Fe, Ti, and Co attributed to cytotoxicity and ROS generation. These findings underscore the importance of commuter exposures and their toxic effects, urging effective mitigating strategies to protect human health.

Long-term rail profile damage in a railway crossing: Field measurements and numerical simulations

Railway crossings are subjected to a severe load environment leading to a degradation of rail profiles due to wear and accumulated plastic deformation. This damage is the result of the high magnitudes of contact pressure and traction generated in the wheel–rail contact during each wheel transition between wing rail and crossing nose. An extensive measurement campaign has been carried out at a test site in Austria in a particularly severely loaded crossing manufactured from an explosion depth hardened (EDH) manganese steel grade. For an accumulated traffic load of 65 Mega-Gross-Tonnes (MGT), the evolution of profile degradation for 16 cross-sections along the crossing rail has been recorded on multiple occasions. The results from the measurement campaign are used to validate a previously presented multidisciplinary and iterative simulation methodology for the prediction of long-term rail damage. It is shown that the predicted rail profile degradation exceeds the measured degradation for some of the cross-sections but generally a good qualitative agreement is observed. Possible reasons for the higher predicted damage are the uncertain distribution of traffic at the test site and differences in material properties between the crossing in the field and the test specimens used for calibration of the cyclic plasticity model. The influence of the frequency of updating the rail profiles in the iterative simulation methodology, and the compromise between computational cost and the number of load cases accounted for in the applied load sequence, are addressed.

Field Tests on Eco-Friendly Railway Precast Concrete Slab

This study focuses on evaluating the field performance of a newly developed eco-friendly precast concrete slab track structure for railway/subway systems in Seoul, South Korea. Although Ballasted railway track structures are one of the most common track structures in the railway industry, they have some drawbacks including higher maintenance cost, un-uniform supports, and a high level of noise and vibration. However, a ballastless (slab-based) track structure system requires less maintenance and uniform support conditions, as well as several ballastless structure systems developed for high-speed trains. The Seoul Metro subway in South Korea has developed a ballastless reinforced concrete (RC) slab railway system using a type of conventional concrete. This study presents a ballastless precast concrete slab using a newly developed eco-friendly concrete, which can significantly improve structural performances and the manufacturability of a railway track structure system. This study evaluates the field performance of the eco-friendly concrete slab system deployed in one of the existing tunnel sections of the Seoul Metro subway system. A total of 10 m long slab sections including a 5 m long eco-friendly “ballasted track to slab track (B2S)” panels section and a 5 m long conventional B2S panels section are installed and monitored side by side. Field tests are performed to measure the level of noise, vibration, dynamic wheel load, rail displacement, and rail stress. The field measurements from the eco-friendly B2S section are compared to those of the conventional reinforced concrete slab track systems. The results show that the performance of the new B2S system using the eco-friendly concrete is comparable and/or superior to the conventional system.

Mapping relationship between dynamic responses of high-speed trains and additional bridge deformations

Deformations of high-speed railways accumulate over time and affect the geometry of the track, thus affecting the running safety of trains. This article proposes a new method to map the relationship between dynamic responses of high-speed trains and additional bridge deformations. A train–track–bridge coupled model is established to determine relationship between the dynamic responses (e.g. accelerations and wheel–rail forces) of the high-speed trains and the track deformations caused by bridge pier settlement, girder end rotation, and girder camber. The dynamic responses are correlated with the track deformation. The mapping relationship between bridge deformations and running safety of trains is determined. To satisfy the requirements of safety and riding comfort, the suggested upper thresholds of pier settlement, girder end rotation, and girder camber are 22.6 mm, 0.92‰ rad, and 17.2 mm, respectively. This study provides a method that is convenient for engineers in evaluation and maintenance of high-speed railway bridges.

A railway local degraded adhesion model including variable friction, energy dissipation and adhesion recovery

The modelling of the wheel–rail contact is fundamental in the railway field since the contact forces directly affect vehicle dynamics, wear, safety and maintenance. In this context, the development of a realistic adhesion model able to describe degraded adhesion conditions is still an open problem because of the complex non-linear behaviour of the adhesion coefficient. To face this problem, in this work an innovative degraded adhesion model has been developed taking into account important phenomena like large sliding at the contact interface, the consequent energy dissipation and the adhesion recovery caused by the cleaning effect on the rail due to the friction forces. The new approach, based on FASTSIM algorithm and Polach theory, is numerically very efficient and has been specifically designed for multibody applications. The developed model has been validated through the comparison with experimental data related to suitable braking manoeuvres.

Nonsmooth Dynamics of a Gear–Wheelset System of Railway Vehicles Under Traction/Braking Conditions

Abstract Gear–wheelset system is a crucial substructure in railway vehicles which affects the operation safety and system reliability, especially in the process of traction and braking conditions. Unlike the general gear transmission system, the gear–wheelset system of railway vehicles operates under an environment with several nonsmooth factors; therefore, it is necessary to analyze the nonsmooth dynamics of the gear–wheelset system for understanding dynamic characteristics better. Herein, a planar dynamic model of the gear–wheelset system of railway vehicles considering motor-driving torque, braking torque, wheel–rail nonlinear interaction forces, nonlinear meshing damping, and piecewise continuous time-varying meshing stiffness is proposed. Then, the proposed model is validated by a simpack model using wheelset's longitudinal velocity. Subsequently, two numerical simulations were performed to reveal the nonsmooth dynamic characteristics under traction and braking conditions. The simulation results indicate that the dynamic stationary point exists in nonsmooth dynamics under traction and braking conditions, which is a critical boundary for transiting any state to a dynamic equilibrium. Besides, the results exhibit the inseparable relationship between time-frequency dynamic characteristics, slip velocity, and wheel–rail nonlinear interaction forces. The effects of harmonic torque under traction conditions and compound braking behavior under braking conditions significantly affect these dynamic characteristics. Additionally, sufficient driving torque can increase the proportion of forward contact and improve the smoothness of the rotation, and the intermittent gear contact phenomenon occurs alternately and frequently in the traction condition. Conversely, only reverse contact occurs in the braking condition.