Rail Side Research Articles

Analysis of Wheel Wear and Wheel-Rail Dynamic Characteristics of High-Speed Trains under Braking Conditions

When high-speed trains operate under braking conditions, the wheel-rail interaction increases significantly, which can lead to more serious wear problems. To analyze the evolution of wheel wear and the dynamic characteristics of wheel-rail under braking conditions, this paper first carries out long-term monitoring of the service state of wheel-rail during the operation period. The study analyzed the matching characteristics of the measured wheel-rail profile and calibrated the wear model by using the collected data. The resulting wear prediction model was then used to examine the wheel wear characteristics under braking conditions. The research results indicate that during the operation period, the wheel experiences tread concave wear within a range of ±20 mm of the rolling circle, at a rate of approximately 0.05 mm per 10,000 km. Meanwhile, the rail experiences top surface wear at a natural rate of about 0.09 mm per year. Concave wear causes the contact point of the wheel-rail to appear in two zones, resulting in a sudden change of contact geometric parameters. The concave worn wheel and rail with a 60 N profile have better matching compared to the 60 rail profile. Increasing the braking torque and wheel-rail friction coefficient will significantly increase the wheel wear depth on straight sections. On small-radius curve sections, rail side lubrication can significantly reduce high rail side wheel flange wear. A worn concave wheel can lead to unfavorable wheel-rail contact geometry characteristics and increase low-frequency components in the vehicle’s lateral dynamic response.

Research on wheel-rail dynamic interaction of high-speed railway under low adhesion condition

Due to the inherent openness of the wheel-rail system, the wheel-rail interface is subject to the influence of a third medium, resulting in a low adhesion state. This study investigates the dynamic interaction between the wheel and rail under low adhesion conditions through the development of a numerical model employing anti-skid control strategies and infinite long track simulation technology. The model's validity is established by comparing its calculations with data from both the multi-body dynamics software UM and field tests. The numerical simulations uncover that the implementation of rail side lubrication significantly reduces longitudinal creep forces, thereby diminishing the wheelset's steering capabilities. Furthermore, it induces a notable increase in lateral wheel-rail interaction, consequently lowering safety indicators in vehicle operations. Rail side lubrication is found to substantially reduce rail side wear, resulting in an approximate 60% decrease in the maximum wear depth. Comprehensive friction control on the rail surface concurrently mitigates rail side and top surface wear. In instances of local low adhesion on both sides, the wheelset experiences pronounced stick-slip vibrations, leading to a deterioration in the longitudinal dynamic performance between the wheel and rail. Unilateral low adhesion situations prompt noticeable yawing and shaking motions within the low adhesion zone, resulting in evident lateral impact phenomena. Upon re-entering the normal adhesion zone from the low adhesion zone, the rail wear index experiences a significant peak, which means that the rails in this area are prone to severe local wear or fatigue.

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.

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.

Wear and RCF problems of metro wheel/rail systems: Phenomena, causes and countermeasures in China

Wear and rolling contact fatigue (RCF) problems observed on metro wheel/rail systems in China in the last 15 years are summarized and explained from the aspects of phenomena, causes, and validated countermeasures. Presented wheel/rail wear in the lateral direction includes wheel flange wear, rail side wear, and abnormal wear of wheels such as differential, hollow, groove, and channel wear. As for irregular wear on wheel and rail running surfaces, the focus is on four and two important cases for wheel and rail, respectively, i.e., low-order wheel polygonal wear, high-order wheel polygonal wear, wheel stochastic out-of-roundness (OOR), wheel corrugation, short-pitch rail corrugation on the tracks with resilient and conventional fasteners, and rail corrugation on damping sleeper tracks. Finally, some unusual RCF problems occurring on wheel and rail surfaces are presented.

Wayside wheelset lateral motion detection and vehicle hunting instability evaluation

Wheel profile wear, or bogie suspension failure will result in hunting instability of the vehicle system which will lead to dramatic changes in the lateral motion of the wheelset. The occurrence of hunting instability will worsen the ride performance of the vehicle or even cause the danger of wheelset derailment. Thus, the in-time and effective detection of wheelset lateral motion is very important for the vehicle hunting stability evaluation. By installing a certain amount of displacement sensors on the rail side along the track and detecting the distance between the wheel and rail when the wheelset passing by, the lateral displacements of the wheelset in measuring points can be obtained. The detection method of wheelset lateral motion by the wayside is studied, which includes the measuring principle, structure design, sensor installation, data acquisition and data analysis, and the application of the method to on-site detection for typical instability cases are demonstrated. At the same time, innovate on the existing on-board hunting instability monitoring method, proposed an evaluation method of hunting instability for wayside lateral movement monitoring system. The results show that: installing 20 eddy current sensors on both sides of the straight track to measure the lateral displacement of the wheelset can meet the requirement of detecting the vehicle hunting instability. At the same time, analyzing the measurement data and fitting the maximum value of the signal collected by each sensor can obtain the lateral trajectory of the wheelset. The wheelset lateral displacement can be used to monitor the occurrence of vehicle hunting instability if periodic motion is detected. The amplitude of the motion can determine the hunting instability level, and the frequency can be used to describe the wheel wear level and calculate the wheel/rail contact equivalent conicity. This method is able to provide a reliable data support for the vehicle operation safety. The proposed monitoring method and monitoring index are also of reference value to the development of other wayside hunting instability monitoring systems.

Analysis of the causes of severe side wear of the high rail on metro curves by numerical simulation and field investigation

Two of the Shanghai metro lines suffered from severe side wear on the high rail, not only in sharp curves but also in large curves, and the service life of some rails on sharp curves was reduced by approximately 50% compared with the last rail replacement. Features and evolution rules for the rail side wear and the wheel flange wear were determined by field measurements and long-term monitoring. A rail wear prediction model, verified in our previous work, is used to reveal the influence of factors on rail wear. The results indicate that the poor lubrication condition at the rail gauge face is the main cause of severe side wear of the high rail, and the use of wheel profiles with low conicity and the loss of profile curvature of low rail profiles caused by the untimely maintenance also increase the side wear of the high rail. The service life of the high rail could be greatly extended by some countermeasures, such as repairing the worn shape of the low rail and repairing/improving the wayside lubrication system.

Thermal–Mechanical Coupling Analysis of Wheel–Rail Sliding Friction under Two-Point Contact Conditions

The generation of wheel–rail-sliding frictional heat is often accompanied by transverse displacement of a wheel. To study the thermal problem of wheel–rail sliding friction at two-point contact, this paper uses an LM tread wheel and a 60 kg·m−1 rail as examples. A thermal–mechanical-coupled finite-element model of equal proportion wheel–rail sliding is established. A direct-coupling method is used to analyze the thermal–mechanical coupling of the wheel–rail interface under sliding contact. This model considers the temperature-dependent material properties and boundary conditions, such as thermal convection and thermal dissipation, in the process of nonstationary frictional-heat conduction. Firstly, the effects of different sliding speeds, axle loads, and contact modes on the temperature and stress fields of the contact area are analyzed. Then, the lubrication and cooling effects of friction modifiers on the rail top and rail gauge angle are compared. The results show that, at a sliding speed of 2 m/s and an axle load of 30 t under a sliding condition of 200 mm, on the top and side of the rail, the temperatures at the contact patch centers are 813 °C and 547.7 °C, respectively. Under different operating conditions, the rail-side temperature is 55–75% of that of the temperature at the rail top, and the rail-side contact and friction stress values are 76–96% of those at the rail top. This indicates that frictional thermal damage on the rail side cannot be ignored. With a lower sliding speed, the thermal response of the two contact patches is closer. The impact of axle load on the frictional temperature and stress on the rail side is more critical than the sliding speed. The optimal lubrication choice is overall lubrication, which can decrease the rail top temperature by 47.2% and frictional stress by 56.2%, as well as decreasing the rail side temperature by 70.3% and frictional stress by 77.4%.

Random analysis of dynamic wheel–rail interactions in the switch panel of a turnout with geometric tolerances based on the probability density evolution method

During train operation, the geometric tolerance in a turnout can be very random, posing a challenge for traditional deterministic vehicle-turnout coupling studies and for daily maintenance. In light of the above situation, a coupled vehicle-switch panel model with random geometric tolerances is proposed. These tolerances result from the discrepancy in relative height difference of rail tops between the straight switch rail and the curved stock rail, and from the gap between the straight switch rail and the curved stock rail in the closure part. The model takes rail flexibility into consideration. The probability density evolution method (PDEM) is applied to capture the resultant probability density function (PDF) of dynamic wheel–rail interactions. The Monte Carlo method is employed for verification of results obtained from the PDEM. The results show that stronger randomness of the vertical wheel force is induced compared with that of the lateral wheel force. The probabilistic range of the vertical wheel force is found to be around 50 kN on the straight switch rail side. Given the largest maximum mean value of rail displacement, it is found that the part of the straight switch rail with a top width of 40 mm requires significant attention.

Prediction of rail profile evolution on metro curved tracks: wear model and validation

ABSTRACT Rail side wear is typically encountered in metro lines (particularly on sharp curves). A reliable rail wear prediction model to evaluate the evolution of the rail profile should be developed. In this study, a rail wear prediction model for a metro line is established. The vehicle system dynamics model is implemented in the SIMPACK software, which considers the actual operating conditions of the metro line. The results show that using the original Tγ/A wear rate function to calculate rail wear may yield some deviations, which necessitates a modification of the wear model based on the measured results of rail wear. Because the hardness of high and low rails on curved tracks changes after work hardening, different correction coefficients must be adopted for the wear rate function of each rail. The rail wear evolution and worn profiles are consistent with the field measurement results when using a modified wear function.

Side Wear Prediction of a Subway Outer Rail on Small Radius Curves Based on System Dynamics of Discrete Supported Track

When a subway train runs on a small radius curve, it causes serious side wear of the outer rail, and a large number of the outer rails of the curve are replaced frequently due to excessive side wear. This paper proposes three prediction models based on the response surface methodology (RSM), support vector machine (SVM), and the relative vector machine (RVM) to estimate the remaining useful life (RUL) of a metro outer rail at a small radius curve determined by rail side wear. In these proposed models, the directly measurable parameters, including various track geometries, axle loads, and primary suspension stiffnesses related to vehicle types, are taken into account. These parameters are proposed from the side wear mechanism and subjected to the method of global sensitivity analysis to rank them in order of importance. The rail side wear for various scenarios is calculated through a numerical simulation model of the vehicle‐unballasted track and Specht friction wear. Furthermore, with the help of simulation experiments and field cases, the prediction performances of three different prediction models are analyzed in detail. The comparison indicates that the predictive model based on RVM is superior in the prediction of RUL based on rail wear. The findings presented in this paper can provide certain reference values for infrastructure managers (IMs).

Analysis of Rail Corrugation Characteristics on High-Speed Rail Based on Transient Finite Element Method

By using the transient finite element method, a three-dimensional wheelset-track coupled rolling contact model for high-speed rail is established, and the rationality and effectiveness of the model are verified by field measurements. Next, the wheel-rail contact stress states and relative slip characteristics are calculated and analyzed to reveal the cause of inner rail corrugation. Then, the vertical vibration acceleration of the rail/wheel is taken as the output variable to study the dynamic responses of the wheelset-track system. Finally, the parameter sensitivity analysis is carried out. The results show that the maximum normal/tangential contact stress between the inner wheel and inner rail is greater than that between outer wheel and outer rail due to the unbalanced load of inner rail caused by the excess superelevation of track structure, which indicates that the unbalanced load of the inner rail may aggravate the development of rail wear, and the rationality of the model established in this paper is verified. The wheel-rail relative slip region on the inner rail side appears periodically, and the distance between the two adjacent slip regions is close to the characteristic wavelength of the measured inner rail corrugation, which illustrates that the periodic variation of slip regions on the inner rail surface plays an important role in the formation of rail corrugation, and the validity of the model is verified. The periodic distribution of wheel-rail relative slip regions on the outer rail surface is not obvious, demonstrating that the outer rail tends to form uniform wear, which is consistent with the fact that the outer rail corrugation is slight in the measured section. The wheelset-track system has been in the process of unstable continuous oscillation in the analysis interval, combined with the analysis results of the wheel-rail relative slip characteristics, it can be concluded that the unstable self-excited vibration of wheelset-track system under the condition of tangential contact force reaching saturation is the main cause of rail corrugation. The dominant characteristic frequencies of vertical vibration accelerations of rail and wheel are all 561 Hz, the corresponding characteristic wavelength (148 mm) is close to the distance (150 mm) between the calculated adjacent slip regions, and is also close to the characteristic wavelengths (125 mm and 160 mm) of inner rail corrugation, which shows that the resonance phenomenon occurs in the wheelset-track system at the above frequency, thus leading to the increase of dynamic responses of wheelset-track system. The fastener vertical stiffness and wheel-rail coefficient of friction have significant effect on the development of rail corrugation, and the running speed determines the occurrence probability of inner/outer rail corrugation by affecting the track superelevation state.

전기 철도차량 차륜 정비에 따른 레일 변형 특성 분석

In order to measure the deformation of the rail according to the operation of the railway vehicle, a strain gauge measurement method under various conditions was used. As a result of measuring strain at the upper, middle and lower positions of the rail, the optimal position of the strain gauge was the lower part of the rail side. The part where the deformation of the rail occurred the most was the upper part of the side. But considering the durability and installation safety of the strain gauge, the lower part where the second largest deformation occurred was considered to be the most suitable. As a result of measuring rail deformation by installing strain gauges at short and long distances, almost all rail deformations were reduced before and after wheel tread maintenance compared to maintenance.

Automation of the Road Gate Operations Process at the Container Terminal—A Case Study of DCT Gdańsk SA

The future increased terminal capacity will result in more container movement through the road complex and rail siding, which are one of the most critical areas (potential bottlenecks) in the container terminal. Truck turnaround time is one of the major factors that customers take into account while deciding how many container volumes they will handle through the container terminal. To enable to optimize increased traffic with future container terminal development, as well as increase gates throughput, and as a consequence, encourage more volume and increase customer satisfaction, Deepwater Container Terminal Gdańsk SA plans to reorganize and automatize the gate operation process. Gate automation includes supply, installation, commissioning, implementation, and maintenance of software and hardware that would allow automatizing the handling of trucks at container terminal gates by using OCR (optical camera recognition) technology, LPR (license plate recognition) systems and self-service kiosk for truck drivers.

Investigating high rail side wear in urban transit track through numerical simulation and field monitoring

One of the major track issues in urban rail transit is the rail side wear, especially at the high rail on sharp curves. The mechanism of rail side wear is very complex and has not been fully understood. This study attempts to characterize the progressive development of high rail side wear in a transit track with heavy traffic. A numerical vehicle-track model is developed based on multi-body dynamics and the modified Archard wear formula and is used to perform a parametric analysis. The side wear development trend observed in the field is in good agreement with the results calculated from the numerical mode. According to the results obtained from this study, the side wear during the life-cycle of the high rail can be approximately characterized into three stages: 1) Stage I, rail wear initiates at the gauge side corner; 2) Stage II, side wear propagates linearly; 3) Stage III, side wear propagates exponentially. The parametric analysis suggests that three maintenance activities may ease the development rate of the high rail side wear in Stage III. These include increasing the rail inclination, adjusting the track gauge on time, and restoring the rail profile of the low rail.

Experimental Assessment of Time-Limited Operation and Rectification of a Bridge Crane.

This paper describes a problem related to a casting bridge crane with a combined load of 200/50/12.5 t and a span of 18.6 m, working in a heavy metallurgical operation. Due to the specific stress of the structure after its long-term operation, longitudinal fillet welds between the upper flange and the web of the main box beam on the rail side of the 200 t trolley were irreparably damaged. As a result, the cross-section of the main beam had opened, thereby substantially reducing its strength and stiffness. This resulted in a disproportionate increase and undesirable redistribution of stresses in the beam and, at the same time, an increase in the probability of acute fatigue or the loss of stability of the elastic beam shape. Therefore, the rectification of the damaged load-bearing structure was carried out by specific structural modifications. Critical load-bearing elements were subjected to complicated strength and fatigue life analyses before and after rectification. These analyses were supported by experimental measurements. The applied modifications resulted in a partial strengthening of the lifting device with the possibility of its further operation, but only in a limited mode, with a limited period of operation with a time limit of 2 years and a reduced total load capacity of 150 t. The applied methods are also applicable for the fatigue analysis of load-bearing elements and equipment for bridge, gantry and tower cranes, crane tracks, road and railway bridges and support structures under machinery and other devices with a dominant transverse and rotating effect.

Influence of Armature Movement Velocity on the Magnetic Field Distribution and Current Density Distribution in Railgun

In a railgun, the velocity of the armature has an important effect on the magnetic field distribution and current density distribution of the launch system. However, the calculation models established by scholars were mostly models under static conditions. They could not effectively reflect the velocity skin effect (VSE). This article uses the finite-element softwares COMSOL and LS-DYNA to establish a calculation model that considers the influence of the armature movement velocity on the magnetic field distribution and current density distribution. The calculation results show that when considering the armature movement, the magnetic field distribution of the rail side is very different from the static calculation result. Under the influence of the VSE, the current of the armature/rail (A/R) interface is mainly concentrated on the end of the armature's tail. When considering the armature movement, the values of maximum current density of the rail side doubled. Also, as the armature velocity increases, its range of influence also increases. However, it tends to saturate after reaching a certain velocity. Considering the influence of the armature velocity on the magnetic field distribution and current density distribution can make our results closer to the actual launch situation.

Design and Study of Intensive Track Laying System for Single Hole and Double Road in Open Cut Station

This paper takes Qingdao subway station as an example, considers reducing the cycle of track laying on the whole line, and adds rails and wells under the existing envelope structure. The single-track row of wells and a double-line entrance to the crossing are proposed. The analytical calculations and numerical simulation methods were used to check the mechanical condition of the station envelope and the main structure of the station under the rails. The research results show that the track laying base can be laid out in the enclosed open excavation station, and a series of problems such as land occupation coordination have been solved, and the period benefit is significant. This scheme can ensure the structural safety before the entrance of the rail row well is closed, and the position of the rail side frame below the middle plate of the station satisfies the requirements of the laying limit. This method has a novel design idea, has high application and promotion value, and provides a good reference for the design and construction of open-cut subway stations.

Effects of train driving modes and the rail foundation structure on the rail side wear in small-radius curves

Rails are one of the main elements of the upper structure of the railway track. The safety and smoothness of the movement of mobile units depends on their reliable operation. During operation, various defects and damages occur in the rails that can directly threaten the safety of traffic. These defects and damages have different causes and development mechanisms, which depend on many operational factors. Studying the causes of the appearance and development of defects in rails is one of the main tasks to increase the uptime of the railway. The rail side wear continues to be one of the basic reasons for removing rails from the rail track. Earlier studies have demonstrated an apparent effect of unbalanced acceleration, rail track parameters and geometrical irregularities (including bond ones) on rail wear. Mostly, the process is typical for small-radius curves the total length of which in Ukrainian railway network is rather great. The article presents the findings of numerical research into vehicle/track interaction under such operational conditions with consideration of existing and prospective structures of rail fastenings. The authors have concluded that train driving modes and rail foundation structure influence the rate of rail head side wear in small-radius curves on the rail track.

Application of plasma surface quenching to reduce rail side wear

Hardening of the side surface of the rail head with the use of optical and electron microscopy is studied. Results of industrial tests are given. Plasma hardening of the side surface of the rail allows one to obtain a favorable structure of the surface hardened layer (mixture of troostite, bainite and martensite) with a hardness of 450-830 HV and a thickness of the quenched layer of 2.5-3 mm. Thus, this significantly increases the service life of the rails due to the 2-3-time decrease in the wear rate of the side surface of the rail. The developed unit for plasma surface hardening of the rail allows performing qualitative surface hardening in width, depth and hardness of the surface layer of the metal. This equipment can be recommended for further pilot-industrial plasma surface hardening of the rail side surface in the conditions of the East Siberian Railway.