Wheel Rail Research Articles

TRACK CIRCUITS INTERFERENCE RESISTANCE INCREASE UNDER THE TRACTION CURRENT INFLUENCE

Purpose. The aim of the work is to increase the electromagnetic compatibility of track circuits with the traction power supply system of railways under the influence of reverse traction current disturbances. Conducting research and analysis of the causes of malfunctions of rail circuits on electrified sections of the railway, existing means and methods of increasing the interference resistance of track circuits and ensuring the electromagnetic compatibility of signaling, centralization and blocking devices with the traction power supply system, and the development of effective technical solutions for normalizing the operation and rail circuits in the conditions influence of traction current interference. Conducting a study of the electromagnetic characteristics of the DT-1-150 track choke-transformer in normal mode and under the influence of external factors on the magnetic system. Methods. During the research, methods of comparative analysis, theories of electric and magnetic circuits, methods of spectral analysis of signals, as well as mathematical, schematic and physical modeling were used. Findings. Situations in which the traction current significantly affects the operation of the rail wheel equipment have been analyzed in the work. The effect of the traction current constant component on the normal operation mode of the track circuits is considered. The coefficients value of the choke-transformer DT-1-150 with traction current asymmetry was determined. A comparative analysis of resistance to reverse traction current disturbances of track receivers of station rail wheels used at the docking station was conducted. The principle-structural scheme of the protective unit for blocking the leakage of direct traction current interference on the section of alternating current traction was developed. The scientific novelty. The scientific novelty of the work consists in identifying and justifying the causes of some specific failures of track circuit; in confirming the integral effect of choke-transformer steel core saturation, created by the constant component of the traction current in the railway power supply system. Practical significance. Based on the conducted research, the interference resistance of the 25 Hz track circuit with the DSSH-16 track relay and DT-06-500S was confirmed. A protective valve block was developed, which prevents the flow of the first periods of the largest amplitude transient current in the track circuit its protects and ensures, thereby, normal operation of track circuit.

Research on the Influence of Wheel Tread Defects on Rolling Contact Fatigue

With the rapid development of high-speed trains, local rolling contact fatigue caused by special local defect damage forms has become more prominent. This article takes circular defects as the research object, adopts the Jiang Sehitoglu multi-axis fatigue damage criterion based on the critical plane method, establishes a finite element model of wheel tread circular defects, and studies the influence of wheel tread circular defects on wheel rail rolling contact fatigue. Based on finite element analysis to obtain fatigue damage parameters, an improved PSO-BP neural network was used to establish a neural network prediction model for fatigue damage parameters, and the feasibility of the model was demonstrated. The research results show that the main influencing factors on the rolling contact fatigue life of wheel tread defects are shear stress and shear strain; The fatigue damage parameter is maximum at the edge of the wheel tread defect; As the defect distribution moves from the center to both sides, the contact stress and damage parameters gradually decrease; As the depth of the defect increases to the size of the radius, the contact stress and damage parameters first increase and then decrease; As the diameter of the defect increases, the contact stress and damage parameters increase, but the amplitude change gradually tends to stabilize with the increase of the defect diameter. The neural network prediction results indicate that all predicted samples are within a reasonable range, and this neural network model can provide a reference for predicting fatigue damage of wheel tread.

Numerical Simulation Study on the Hydrothermal Characteristics and Dynamic Response of the Embankment–Bridge Transition Zone in Cold Regions

The chain reaction of bridge abutment structure caused by frost heave of the embankment–bridge transition zone filler in cold regions has a great impact on the smoothness of railway lines, which will bring great challenges to the normal operation, safety, and maintenance of rail transit in cold regions under the action of long-term dynamic load. In this paper, the hydrothermal model and dynamic analysis model of the embankment–bridge transition zone are established, and the frost heave deformation rule and dynamic response characteristics of the embankment–bridge transition zone under frost heave conditions are studied. The results show that the effect of the bridge abutment structure on vertical frost heave is mainly concentrated in the range of the bridge abutment, and the vertical frost heave near the abutment is much smaller than other parts away from the abutment. The dynamic response and wheel–rail contact force of the embankment–bridge transition zone are significantly different under non-frost heave and frost heave conditions. Frost heave may cause a higher risk of derailment. This study provides a scientific reference for the design, construction, and safe operation and maintenance of embankment–bridge transition zones in cold regions, and has certain practical engineering significance.

The Two-Parameter Bifurcation and Evolution of Hunting Motion for a Bogie System

The complex service environment of railway vehicles leads to changes in the wheel–rail adhesion coefficient, and the decrease in critical speed may lead to hunting instability. This paper aims to reveal the diversity of periodic hunting motion patterns and the internal correlation relationship with wheel–rail impact velocities after the hunting instability of a bogie system. A nonlinear, non-smooth lateral dynamic model of a bogie system with 7 degrees of freedom is constructed. The wheel–rail contact relations and the piecewise smooth flange forces are the main nonlinear, non-smooth factors in the system. Based on Poincaré mapping and the two-parameter co-simulation theory, hunting motion modes and existence regions are obtained in the parameter plane consisting of running speed v and the wheel–rail adhesion coefficient μ. Three-dimensional cloud maps of the maximum lateral wheel–rail impact velocity are obtained, and the correlation with the hunting motion pattern is analyzed. The coexistence of periodic hunting motions is further revealed based on combined bifurcation diagrams and multi-initial value phase diagrams. The results show that grazing bifurcation causes the number of wheel–rail impacts to increase at a low-speed range. Periodic hunting motion with period number n = 1 has smaller lateral wheel–rail impact velocities, whereas chaotic motion induces more severe wheel–rail impacts. Subharmonic periodic hunting motion windows within the speed range of chaotic motion, pitchfork bifurcation, and jump bifurcation are the primary forms that induce the coexistence of periodic motion.

Dynamic response analysis of high-speed train gearboxes excited by wheel out-of-round: experiment and simulation

Due to the special characteristics of rail vehicles, wheel–rail excitation has always had a huge impact on the stable operation of the vehicle system and the dynamic performance of each component structure. This paper takes high-speed train gearbox as the research object and establishes a rigid-flexible coupling dynamics model and analyses the dynamic response and fatigue damage of the gearbox under the excitation of wheel flat and wheel polygon. Combined with the analysis of test data from the gear transmission testrig and actual line operation of high-speed trains, it shows that high-speed train gearboxes are different from those applied in other fields, where the gear meshing excitation is no longer its main excitation source, but the wheel–rail excitation instead. The comparison analysis between the wheel flat and wheel polygon conditions indicates that the response of the gearbox to the wheel flat excitation is similar to the operational modal test and is capable of causing multi-order modal vibration of the gearbox. The effect of the wheel polygon on the gearbox is similar to that of single-frequency excitation, which lead to certain order modal resonance in the gearbox under frequency coupling situations. The impact of both conditions on gear box fatigue damage increases with the vehicle operating speed.

Inverse wheel–rail contact force and crossing irregularity identification from measured sleeper accelerations – A model-based Green's function approach

A novel model-based method for railway Crossing Panel Condition Monitoring (CPCM) is presented. Based on sleeper accelerations measured during wheel crossing transitions and knowledge of the crossing panel design, it is shown that it is possible to identify the ballast stiffness properties, vertical wheel–rail contact forces and vertical relative wheel–rail displacement trajectories (crossing irregularities) in the crossing panel. The method uses a multibody dynamics simulation model with a finite element representation of the track structure for evaluation of the dynamic interaction between vehicle and crossing panel. Considering the low-frequency domain where the sleeper response is not significantly affected by the influence of the irregularity due to the designed (and current state of the) crossing and wing rail geometry, the ballast condition is identified via a calibration of the distribution of ballast stiffness in the finite element model. This enables ballast stiffness identification without a priori knowledge of the crossing geometry. From the reconstructed track displacements, the wheel–rail contact forces are identified by solving an inverse problem formulated using the Green's Kernel Function Method (GKFM) that provides a direct link between the track excitation forces and the track response. Further, the irregularity induced by the crossing and wing rail geometry is estimated by taking the difference between the wheel and rail displacements during the crossing transition computed from the identified wheel–rail contact forces. By monitoring the evolving irregularity, the degradation of the crossing rails over time can be assessed. The method is verified and validated using concurrently measured sleeper accelerations and laser scanned crossing geometries from six crossing panels in situ.

Analysis of corrugation development on a Tianjin metro straight line focusing on wheel-rail contact mechanics

The development features of corrugation on the straight track metro line are studied to find the root cause of corrugation. Firstly, the measured corrugation characteristics on the line are investigated and a three-dimensional wheel-rail (WR) rolling contact finite element (FE) model is constructed. Then, the WR stick-slip (SS) characteristics, WR contact and rail wear are analyzed to understand the evolution process of corrugation from the micro transient point of view. Finally, combined with a system stability analysis, the development trend of corrugation is characterized from the macro perspective. The results show that the WR contact has a significant SS variation under the corrugation condition, which promotes the initial corrugation to develop further. For the fixed node in the contact area on the rail surface, the maximum stress and strain of the section where it is located will gradually transfer from the subsurface to the surface with the wheel running, so the damage prone position will also form first on the subsurface and gradually transfer to the surface. This shows from the micro viewpoint that the formation of wave crest/trough in the corrugation section is a bottom-up process of damage accumulation. The corresponding frequency of 648 Hz of the unstable vibration mode in the WR system is close to the passing frequency of 656 Hz of measured corrugation, demonstrating that the initial corrugation will tend to intensify with the wheel running.

Mechanism of rail corrugation formation on metro curves with a type of floating-slab track

ABSTRACT A steel spring floating-slab track (SSFST) capable of mitigating railway-induced vibrations has been widely used in a metro line in Beijing. In sharp curves with radii of less than 500 m, severe corrugation with wavelengths of about 125–200 mm and passing frequencies of 70–80 Hz occurred on low rails. Field measurements and numerical simulations were used to investigate the cause of the corrugation. The results show that the wavelength of corrugation is related to the speed of the vehicle and the corrugation passing frequency is a fixed frequency. The formation of the rail corrugation in the sharp curves does not depend on the torsional and bending resonances of wheelsets and P2 resonance. The wheel–rail vertical fluctuating force at frequencies of 67–75 Hz arises easily under a broadband excitation of the rail irregularity due to the vertical bending of the rail and the floating slab relative to the subgrade. The numerical simulations show that the corrugation with dominant wavelengths of 160–200 mm initiates when the vehicle passes over the irregularity. The simulation results are consistent with the field test results. The corrugation occurs on SSFST as a result of the vertical bending of the entire track, driven by a wavelength-fixing mechanism.

Carbody hunting behaviour of high speed vehicles in low effective conicity of wheel-rail contact

In the past, bogie hunting instability garnered more attention due to its potential for causing serious safety issues. However, with the rise in high-speed vehicle speeds and operational mileage, the concerns arising from carbody hunting can no longer be overlooked. This article investigates the causes and solutions for low-frequency carbody swaying under low effective conicity in wheel-rail contact, employing a combination of experimental and numerical techniques. Initially, the study involves an in-depth analysis of time-domain signals from lateral and vertical accelerations of the carbody and bogie frame during a high-speed train field-test. The carbody vibration mode resulting from carbody hunting displays a swaying motion at a frequency of 1.5 Hz. Subsequently, a dynamic system model of the high-speed vehicle was established and the suspension mode of the model were verified. The frequency of the carbody upper sway motion is determined to be 1.39 Hz. Low effective conicity is induced when grinding wheel match with new rail or new wheel match with grinding rail. Under this low effective conicity, the hunting frequency of the vehicle is around 1.5 Hz, close to the frequency of the carbody upper sway motion. The coincidence of the hunting frequency and the upper sway motion frequency leads to the low-frequency swaying of the carbody. At last, the effects of wheel profiles, rail profiles and suspension parameters on the carbody hunting have been studied. The study demonstrates that addressing low-frequency carbody swaying can be achieved through targeted rail grinding. This process involves modifying the rail profile while ensuring careful grinding of the rail inner corner. Furthermore, it has been confirmed in the article that replacing suitable yaw dampers is also effective.

An efficient 3D finite element procedure for simulating wheel–rail cyclic contact and ratcheting

Various models for simulating rail ratcheting behaviour were developed to study rolling contact fatigue (RCF) damage in rails. However, limitations remain in terms of the accuracy of wheel–rail contact modelling and computational efficiency of the cyclic loading simulation. This study developed an efficient 3D finite element (FE) procedure to simulate ratcheting in rails subjected to numerous load cycles. The procedure simulates a wheel rolling repeatedly over a rail section with updated stress–strain states, enabling automatically executed cyclic loading simulation given a predefined number of cycles. To ensure the accuracy of the contact modelling, the effect of meshing schemes on subsurface stress distribution was examined. In addition, the FE contact model with the selected meshing scheme, which balances accuracy and computational efficiency, was verified against the widely accepted CONTACT program. Subsequently, a non-linear kinematic hardening (NLKH) steel material was used in the FE model for ratcheting simulations with up to 100 wheel-loading cycles. The rail surface and subsurface stress states were replicated under partial-slip wheel–rail rolling contact conditions with traction coefficients of 0.10, 0.20 and 0.35, respectively. The ratcheting behaviour was extensively analysed in terms of plastic deformation, contact patch evolution, and ratcheting rates. The simulated plastic deformation was found to alter the contact geometry and thus contact stresses, which in turn affect further accumulation of plastic deformation and subsequent ratcheting strains. These findings highlighted the importance of considering the interplay between the rail ratcheting behaviour of the rail and evolving contact conditions for predicting ratcheting and RCF damage in rails.

Investigation on the causes of rail corrugation in high-speed railways based on the wheel–rail transient rolling contact model and wear model

This work investigated the causes of rail corrugation in a high-speed railway. A three-dimensional (3D) finite element (FE) model of the vehicle-track system (VTS) and a rail wear prediction model were developed. The 3D FE model was employed to study the dynamic interactions of the VTS excited by rail welds with varying wavelengths. The wear model calculates the wear depth on rail surface based on the Archard’s theory. The frequency response analysis and modal analysis were implemented to identify the vibration modes relevant to the corrugation. The phase relationship between the initial corrugation and the resulting dynamic wear was discussed. The vertical vibration at 543 Hz of the track was found to be responsible for the initiation of the studied corrugation. The excitation from the rail welds is one of the necessary conditions for the formation of this type of corrugation. The evolution of the phase shift of the dynamic wear with respect to the existing corrugation indicates that the corrugation caused by the rail welds is self-limited and the corrugation will stabilize at a certain value. The corrugation will translate on the rail surface due to a leading phase angle of the dynamic wear relative to the corrugation geometry.

Investigating the wheel–rail dynamic response of transition system of concrete slab and ballasted tracks through train–track interaction model

Investigating the wheel–rail dynamic response of transition system of concrete slab and ballasted tracks through train–track interaction model

Coupling effect of track irregularity and wheel–rail contact conicity on carbody swaying of a metro vehicle: an experimental investigation

A carbody swaying with low frequency of about 2 Hz occurs during vehicles with linear induction motors (LIM) running in shallow curve and straight sections on a China metro line, which significantly deteriorates the ride comfort of passengers. A series of field tests were carried out to identify the main cause and possible solutions. During the tests, the vibration characteristics, dynamic performance, wheel–rail contact condition and track condition were analysed. The test results show that the abnormal carbody swaying is a manifestation of a frequency coupled resonance between the track excitation frequency, bogie hunting frequency and carbody modal frequency at the operating speed. The periodic excitation of the track is the periodic track alignment irregularity with a wavelength of 11–13 m, which is caused by rail surface wear during long-term operation. The carbody swaying can be suppressed by reprofiling the wheel tread to LMA and optimising the suspension parameters.

Influence of P2 resonance of metro wheel–rail system on fatigue failure of rail fastening clips

ABSTRACT Fatigue fracture of rail fastening clips is a common failure in metro. In order to clarify the prevailing factors, on-site experiments and simulations are conducted on a metro line in China to reveal the relationship between wheel–rail resonance and the failure of fastening clips. To reveal the failure mechanism of the fastening clip in the installed state, a vehicle–track coupled dynamics model is created together with a refined finite element model of the fastening system. Rail irregularities are measured to account for the actual track excitations. The results show that both the wheel–rail force and the rail displacement increase significantly when the excitation frequency of the rail corrugation is close to the P2 resonant frequency of the vehicle–track system. At the P2 resonance frequency, the drastic increase in the amplitude of stress cycles of the clip leads to a significant reduction in the fatigue life of the clip. To remedy this situation, the influence of different corrugation depths on the fatigue life of the clip is investigated and a limit value for rail grinding is proposed, which takes into account the rail corrugation and the vehicle speed on the line under investigation to ensure the operating condition of the rail fastening system. The comparison between the dynamic behaviour and the fatigue life of the fastening clips before and after rail grinding shows that timely rail grinding can extend the life of the clip and ensure the safe operation of the train.

Smart inspection of rail wheels with matrix arrays

Rail wheels are one of the most safety critical safety components of rolling stock. Any failure can lead to catastrophic events resulting in high material damage and personal injury or even fatalities. Therefore, international railway standards require non-destructive inspection by means of ultrasound testing (UT) on a regular basis. Due to increasing distances, loads and speeds there are increasing demands on the precision and the scope of testing. However, the inspection of train wheels is complicated due to the large variety of wheel geometries and the further influence of different milage. Moreover, extended inspection areas up to a full body inspection define many different defect positions, which are to some part difficult to access. This article describes industrial solutions, which allow the full-body inspection of train wheels including face, flange, web and tread for volumetric defects (from 2mm diameter) and surface cracks (from 5 mm length and 1 mm depth). In the latest upgrade, these systems can be now equipped with matrix probes. At the beginning of the article basic principles and general probe configurations will be discussed. The main part of this article is then dedicated to highlight the positive impact of the implementation of matrix probes. Besides a reduction of the form factor due to the decreased number of probes, matrix probes allow a direct coupling check thus fundamentally amending the existing state-of-the-art. Other advantages refer to improved settings for a higher reliability of the system. Finally, it is outlined in which way matrix probes provide additional functionalities to extend the current state-of-the-art towards a smart inspection.

Research on the influence of random stiffness of the rubber tie plate on the coupled vehicle-turnout system based on the probability density evolution method

Track supporting stiffness plays a crucial role in the running quality of a vehicle crossing through a turnout. This paper mainly focuses on the influence of random stiffness of the rubber tie plate on the vehicle-turnout coupling system. The relevant random field is constructed via the number theoretical method (NTM). The coupled vehicle-turnout model with flexible rails is built via the modal superposition method. The probability density function (PDF) is obtained via the probability density evolution method (PDEM). Cases of normal distributions with various mean values of stiffness are compared to contrast the relevant impact on the dynamic wheel–rail interaction. Research results indicate that an increase of the stiffness of the rubber tie plate can abate the transverse sway of the vehicle and low down the wheel number. The target stiffness should be taken as 35 kN/mm and corresponding normal distribution with a confidence interval of plus and minus 5 kN/mm can be accepted. The discrepancy between the mean value and the relevant PDF contour clarify the importance and necessity for analysis of randomness. Research results of this paper can serve as the theoretical fundament of the track stiffness homogenisation of a turnout in the future.

Research on the influence of flexible wheelset rotation effect on wheel rail contact force

PurposeUnder the high-speed operating conditions, the effects of wheelset elastic deformation on the wheel rail dynamic forces will become more notable compared to the low-speed condition. In order to meet different analysis requirements and selecting appropriate models to analyzing the wheel rail interaction, it is crucial to understand the influence of wheelset flexibility on the wheel-rail dynamics under different speeds and track excitations condition.Design/methodology/approachThe wheel rail contact points solving method and vehicle dynamics equations considering wheelset flexibility in the trajectory body coordinate system were investigated in this paper. As for the wheel-rail contact forces, which is a particular force element in vehicle multibody system, a method for calculating the Jacobian matrix of the wheel-rail contact force is proposed to better couple the wheel-rail contact force calculation with the vehicle dynamics response calculation. Based on the flexible wheelset modeling approach in this paper, two vehicle dynamic models considering the wheelset as both elastic and rigid bodies are established, two kinds of track excitations, namely normal measured track irregularities and short-wave irregularities are used, wheel-rail geometric contact characteristic and wheel-rail contact forces in both time and frequency domains are compared with the two models in order to study the influence of flexible wheelset rotation effect on wheel rail contact force.FindingsUnder normal track irregularity excitations, the amplitudes of vertical, longitudinal and lateral forces computed by the flexible wheelset model are smaller than those of the rigid wheelset model, and the virtual penetration and equivalent contact patch are also slightly smaller. For the flexible wheelset model, the wheel rail longitudinal and lateral creepages will also decrease. The higher the vehicle speed, the larger the differences in wheel-rail forces computed by the flexible and rigid wheelset model. Under track short-wave irregularity excitations, the vertical force amplitude computed by the flexible wheelset is also smaller than that of the rigid wheelset. However, unlike the excitation case of measured track irregularity, under short-wave excitations, for the speed within the range of 200 to 350 km/h, the difference in the amplitude of the vertical force between the flexible and rigid wheelset models gradually decreases as the speed increase. This is partly due to the contribution of wheelset’s elastic vibration under short-wave excitations. For low-frequency wheel-rail force analysis problems at speeds of 350 km/h and above, as well as high-frequency wheel-rail interaction analysis problems under various speed conditions, the flexible wheelset model will give results agrees better with the reality.Originality/valueThis study provides reference for the modeling method of the flexible wheelset and the coupling method of wheel-rail contact force to the vehicle multibody dynamics system. Furthermore, by comparative research, the influence of wheelset flexibility and rotation on wheel-rail dynamic behavior are obtained, which is useful to the application scope of rigid and flexible wheelset models.

Dynamic Response Study of Overhead Contact System Portal Structure Based on Vehicle–Track–Bridge Coupled Vibration

In light of the rapid development of electrified railways, the safety and stability of train operations, as well as the catenary’s interaction with current quality, have garnered widespread attention. Electrified train operation with additional track irregularities serves as a principal excitation source within the vehicle–bridge–catenary system, significantly influencing the vibration characteristics of the system. Addressing the aforementioned issues, we first established the vehicle–track dynamics model and the bridge–catenary finite element model based on the principles of coupled dynamics of the vehicle–track system. These models are interconnected using dynamic forces between the wheel and rail. Subsequently, within the vehicle–track coupled system, track random irregularities are introduced as input excitations for the coupled model, and the dynamic response of the system is simulated and solved. Then, the obtained wheel–rail forces are applied to the bridge–catenary coupled system finite element model in the form of time-varying moving load forces. Finally, the dynamic response characteristics of the catenary portal structure under different conditions are determined. Meanwhile, a study on the vibration characteristics of the truss-type pillar portal structure was conducted, and the results were compared with those of existing models. The results indicate that the vertical and lateral forces between the vehicle and track are positively correlated with the speed and irregularity amplitude. Response values such as the derailment coefficient and wheel load reduction rate are within the specified range of relevant standards. The low-order natural resonant frequency of the truss-type pillar structure has, on average, increased by 0.86 compared to the existing pillar structure, which signifies improved stability. Furthermore, under various conditions, the average reductions in maximum displacement and stress response of this pillar structure are 13.2% and 14.19%, respectively, in comparison to the existing pillar structure, rendering it more suitable for practical engineering applications.

Online assessment of train hunting stability by monitoring dynamic wheel–rail displacement: why and how?

Online assessment of train hunting stability by monitoring dynamic wheel–rail displacement: why and how?

Development of a wheel wear prediction model considering the interaction of abrasive block–wheel and wheel–rail

A reliable model for predicting wheel wear that considers the interaction between an abrasive block and a wheel as well as the contact between the wheel and rail is developed. First, a wheel wear prediction model that integrates vehicle system dynamics and the Archard wear model for wheel–rail interactions is developed. The wheel wear prediction procedure is validated using measured wheel profiles without the influence of abrasive blocks. Second, a new wheel wear prediction model that integrates the previously validated wheel wear prediction model, a finite element method, and a modified Archard wear model for abrasive block–wheel interactions is developed. The new method for predicting wheel wear is validated using the measured data with acting abrasive blocks. The results show that the tread wear rate due to wheel–rail contact is approximately 0.057 mm/104 km and that the tread wear rate due to abrasive block–wheel and wheel–rail contact is approximately 0.070 mm/104 km at a continuous air pressure of 3.0 bar.