Rail Cross-section Research Articles

Research on ultrasonic guided wave-based high-speed turnout switch rail base flaw detection

Turnout switch rail fracture detection is currently a serious issue in the field of railway transportation. Guided wave detection, a non-destructive testing method, is a good way of studying this issue and looking for a suitable solution. For this paper, a guided wave mode and an excitation position were selected based on the phase velocity dispersion curve and the wave structure. After this, a model was devised for the turnout switch area using the finite element (FE) method. This model considered the straight switch rail, curved stock rail, bolt hole, spacer block, and sub-rail foundation, and verifies the validity of the simulation model through the experiment. The propagation characteristics of guided waves in the switch rail were then simulated in different fracturing states by means of a 30-kHz excitation applied vertically to the rail base. The results showed that a single mode of the guided wave could be generated by this excitation method, showing that it could be used as an effective means for fracture detection. The growth rate of the root-mean-square (RMS) value of the time-domain acceleration signal could then be analysed to identify the state of fracture in the straight switch rail. This discrimination method is suitable for finding fractures parallel to the rail cross-section with a width of 5 mm or more at the bottom of the straight switch rail.

Predicting the wear on the non-working side of the rail profile registration method and its validation

Abstract Rail cross-section profile detection can assess the wear and tear of measured rails, providing crucial references for railway maintenance and upkeep. It is challenging to use the conventional method to register only the profile of rail head detection accurately. After the rail edge adjustment in some conventional railways, it becomes difficult to determine the base point of rail profile registration. Due to the wear of non-working edge of rail, a rail profile registration method is proposed. Firstly, a wear prediction model based on the generalized regression neural network is constructed by optimizing smoothing parameters through ten-fold cross-validation to achieve the optimal values. This model predicts the wear values on the non-working rail edge, providing reliable coordinates for two wear points as alignment reference points. Secondly, an initial alignment between the measured profile and the target profile is achieved using the nearest point iterative algorithm, which ensures that both profiles are in the same region and oriented similarly. Thirdly, the weight is assigned to the wear measurement points based on their respective wear values. The predicted positions of wear points are applied for calculating the translation and rotation parameters. These parameters could align the measured profile and facilitate the final profile alignment. Lastly, the experimental profiles under rail adjustment conditions were registered, verifying the accuracy of the proposed method. The research results indicate that under rail adjustment conditions, the mean squared error (MSE) between the calculated and actual values of lateral wear is 0.094 mm2, which is lower than the MSE from manual measurements. The calculated lateral wear value for experimental profiles achieved high alignment and calculation accuracy. This method can be applied in practical projects, providing an effective solution for rail head profile alignment and serving as a reference for profile alignment on the non-working rail edge with incomplete measurement data.

Microstructure gradients across the white etching and transition layers of a heavy haul pearlitic steel

This study delves into the frequent surface cracking observed in severely damaged pearlitic carbon steel rails, a phenomenon often attributed to the challenging characteristics of the white etching layer (WEL) formed during railway operations. To explore this issue, a severely damaged rail cross-section featuring a substantial WEL layer measuring 600 μm in depth was analyzed. The WEL's size was initially determined through optical microscopy and characterized via nano-hardness testing, which revealed an impressive hardness of up to 12 GPa. High-energy synchrotron X-ray diffraction (HESXRD) analysis was employed to uncover the crystalline structure diversity gradient that resulted from railway use. The results unveiled that cumulative high-temperature surface damage leads to the formation of both the WEL and a transitional layer. Within this transitional layer, a gradual reduction in retained austenite is observed, coupled with an increase in the presence of cementite and ferrite as one approaches the base metal. Remarkably, very shallow depths from the surface display tempered martensite characteristics, characterized by high nanohardness, lower dislocation density, and an initially smaller, then increasing austenite fraction. The use of site-resolved synchrotron radiation diffraction at different depths from the surface to the interior of the damaged rail cross-section allowed a unique insight into the phase transformations, microstrain developments, and compositional evolution.

Study on train running safety in railway switches and sharp curves considering wheel wear evolution

Train derailments are frequently reported during the long-term operation of the freight wagons. With this consideration, this paper aims to combine 3D quasi-static derailment analysis, dynamic simulation and reliability assessment to systematically investigate the running safety in railway switches and sharp curves considering the evolution of wheel flange wear (WFW). Firstly, an efficient and accurate wheel-rail contact geometry algorithm has been proposed to considering the large wheelset yaw angle and the variable rail cross-sections during derailment. Then a freight wagon-track (switch) dynamic interaction model is developed for derailment simulation. Finally, the Kriging method is presented to represent the dynamic responses of the derailment coefficient and wheel load reduction rate (WLRR) when consider the randomness of the input variables. The results show that severe WFW can significantly reduce the derailment limit. The WLRR in the switch exhibits strong nonlinearity with the input parameters. The probability of exceeding the limit of derailment coefficient in a sharp curve is greater than the probability of exceeding the limit of WLRR. This work provides a comprehensive understanding of the running safety and derailment behaviour in switches and sharp curves with the evolution of WFW, contributing to enhanced safety and efficiency in rail transportation.

Design, Analysis, and Optimization of Off-Highway Rear Dump Truck Chassis Frame Rail Profile Using Design Exploration and Finite Element Analysis Technique

<div>During mining material hauling, the chassis frame structure of rear dump trucks is subjected to fatigue loading due to uneven road conditions. This loading often leads to crack propagation in the frame rails, necessitating the determination of stresses in the critical zone during the design stage to ensure structural integrity. In this study, a computer-aided engineering (CAE) methodology is employed to size and select the rectangular profile cross section of the chassis frame rail. A detailed design investigation of the chassis frame is conducted to assess its load resistance, structural flexibility, and weld joint fatigue life under critical stresses arising from combined bending and torsion loads. The optimization process aims to determine the optimal rail size and material thickness, striking a balance between minimizing mass and maximizing structural reliability. By achieving this, the risk of major structural failures during the transportation of large payloads can be significantly reduced. To address the demand for extended structural life and reduced chassis frame weight, the frame rail cross section is optimized using a multi-objective genetic algorithm (MOGA) implemented within the ANSYS software package. This optimization process is facilitated by utilizing design exploration studies and finite element analysis (FEA) techniques to understand how stress affects the chassis frame of a vehicle when it is subjected to combined bending and torsion load case. To do this, the research study used a combination of analytical calculations, mathematical modeling, and design exploration studies.</div> <div>The research findings highlight the effectiveness of combining empirical approaches with modern CAE tools, enabling engineers to design and analyze complex structures with optimized sizes and weights suitable for off-highway mining applications.</div> <div>Through the utilization of this integrated approach, significant advancements can be made in enhancing the structural performance and efficiency of chassis frame structures in the demanding off-highway mining industry.</div>

Understanding the behaviour of magnetic field distribution of railgun under transient conditions using finite element method

The magnetic field distribution in the rails is a crucial factor in comprehending railgun behaviour. The projectile's rapid movement has a significant impact on the magnetic field. If the dispersion of the magnetic field conclusions regarding the conductors are known suitable methods can be used to sketch the magnetic field distribution. The railgun operates on the premise that a high current flow through the rails and armature will create a strong magnetic field. As a result, before designing magnetic shielding, it is necessary to study the features of the magnetic field distribution. The shape of rail and armature cross section is very essential in rail gun design as it determines the magnetic field distribution over rail and armature. The rail gun geometries with rectangular, convex and concave rail cross-sections are compared and simulated using finite element method (FEM). This method is used to determine the magnetic field distribution over rail and armature by sweeping armature position for different rail cross sections. It is observed that for the different rail/armature shapes like rectangular, convex and concave shapes, the C shaped convex armature possesses strong magnetic fields with minimum current density concentration at the throat and trailing end of the armature. From simulation, it can be shown that the magnetic flux density is a descending function of the central angle. The electromagnetic (EM) rail gun launching mechanism was therefore proven to be compatible with the circular concave armature.

Theoretical and Experimental Research on the Influence and Optimization Method of the 60N Profile in Turnout

This research elucidates the influence of the 60N rail profile on the dynamic interaction between wheel and rail, and the dynamic performance within the turnout. The influence of the 60N profile on the long-term service efficiency of turnouts was scrutinized. Subsequently, an optimization approach for the 60–60N rail combination profile was suggested. The main conclusions are as follows: (1) During the passage in the main direction, the 60N rail profile enhances driving stability and mitigates the progression of wear. However, it causes focalized wheel–rail contact on the rail head and escalates contact stress. (2) During the passage in the branch direction, the 60N rail profile amplifies the lateral dynamic force and rail wear rate in the closure panel, engendering two-point contact and increased contact stress. (3) In the early stage of field service of turnouts, a robust correlation exists between the contact band and the rail profile. In the fragile cross-section of the point rail, the contact band of the 60N rail profile turnout fully occupies the rail head, potentially causing stress concentration on the non-working edge position. By the stable service period, the wheel–rail contact band is mainly influenced by total weight. (4) An optimization method for the 60–60N combination profile was proposed with the corresponding machining tool profile designed. This strategy can avoid the profile transition before and after the turnout, reduce field maintenance workload, enhance running stability of straight passage through the turnout, and preclude fatigue damage in the weak cross-sections of the point rail.

Оптико-электронная система для оперативного контроля прямолинейности железнодорожных рельсов

The paper considers principles of operation of the optical electronic devices designed for operational high-precision control of the railway rails rolling surface straightness. It provides a description of the functional scheme proposed by the authors of the optical electronic devices of the triangulation type with structured illumination, where the rolling surface straightness is assessed based on analyzing the images of the rail cross sections registered by a linear camera. A technical solution is proposed that could significantly increase control and reliability of its results, as well as ensure image registration of the rail cross sections, where the distance between them is not exceeding 1 mm with the measurement car speed of 180 km/h. Mathematical expressions were obtained to study the optical electronic devices proposed scheme influence on the threshold sensitivity of control over the points' position along the rail rolling surface. To reduce the control results error, methods of the coordinates' subpixel refinement of the structured illuminated peaks registered coordinates were used. In the course of numerical experiments, the error root-mean-square deviation dependence in measuring the rail surface points' coordinates on the signal-to-noise ratio and the structured illumination peaks width values was studied. Requirements are formulated to components of the triangular type optical electronic devices, which could be introduced in design and development of the high-precision equipment for operational control of the railway track rolling stock straightness

Three-Dimensional Measurement of Full Profile of Steel Rail Cross-Section Based on Line-Structured Light

The wear condition of steel rails directly affects the safety of railway operations. Line-structured-light visual measurement technology is used for online measurement of rail wear due to its ability to achieve high-precision dynamic measurements. However, in dynamic measurements, the random deviation of the measurement plane caused by the vibration of the railcar results in changes in the actual measured rail profile relative to its cross-sectional profile, ultimately leading to measurement deviations. To address these issues, this paper proposes a method for three-dimensional measurement of steel rail cross-sectional profiles based on binocular line-structured light. Firstly, calibrated dual cameras are used to simultaneously capture the profiles of both sides of the steel rail in the same world coordinate system, forming the complete rail profile. Then, considering that the wear at the rail waist is zero in actual operation, the coordinate of the circle center on both sides of the rail waist are connected to form feature vectors. The measured steel rail profile is aligned with the corresponding feature vectors of the standard steel rail model to achieve initial registration; next, the rail profile that has completed the preliminary matching is accurately matched with the target model based on the iterative closest point (ICP) algorithm. Finally, by comparing the projected complete rail profile onto the rail cross-sectional plane with the standard 3D rail model, the amount of wear on the railhead can be obtained. The experimental results indicate that the proposed line-structured-light measurement method for the complete rail profile, when compared to the measurements obtained from the rail wear gauge, exhibits smaller mean absolute deviation (MAD) and root mean square error (RMSE) for both the vertical and lateral dimensions. The MAD values for the vertical and lateral measurements are 0.009 mm and 0.039 mm, respectively, while the RMSE values are 0.011 mm and 0.048 mm. The MAD and RMSE values for the vertical and lateral wear measurements are lower than those obtained using the standard two-dimensional rail profile measurement method. Furthermore, it effectively eliminates the impact of vibrations during the dynamic measurement process, showcasing its practical engineering application value.

Refined nonlinear fractional derivative model of vehicle-track coupling dynamics

The coupled vehicle-track system (CVTS) dynamics have been extensively investigated for decades. However, the calculation accuracy of prevailing vehicle-track coupling models needs to be improved in the high frequency range due to the inappropriate model simplification and neglect of material nonlinearity. In this study, we propose a refined numerical model of the CVTS that considers the nonlinear properties of the railpads and primary suspension using the fraction derivative Zener model. Furthermore, we more realistically simulate the wheelset, rail and railpad configuration with the elastic axle, solid finite element and surface-support models, respectively, and improve the computation efficiency by employing the mode superposition method. The results demonstrate that the refined CVTS model is more accurate than the classical model in simulating vehicle-track coupling dynamics above 2 kHz. In particular, there are significant differences in the dynamic response of the elastic wheelset model compared to the rigid model over a broad frequency range, with an 11% difference in the bogie acceleration response at the first dominant frequency. When the railpads are modeled using the surface-support model, the rail acceleration differences exceed 41% near 1 kHz and 44% near 2650 Hz, compared to the point-support model. Additionally, the rail response at various locations across the rail cross section can be calculated using the finite element method in this refined model. Overall. the proposed CVTS model provides high accuracy and efficiency for random vibration analysis, especially in the high frequency domain.

Effect of active cooling on the thermal effect of electromagnetic rail under single launch mode

In order to investigate the influence of active cooling on the rail thermal effect of electromagnetic gun under single launch mode, characteristics of the peak temperature, cross-section current density and temperature distribution, axial temperature distribution of rail with and without active cooling are simulated. In addition, the time-varying characteristics of the rail axial temperature distribution, the temperature time-varying characteristic in different temperature parts on the rail and the influence of the cooling water flow velocity on the temperature in different temperature parts are experimentally studied. The results show that during the launch, there is almost no difference between the rail peak temperature and its location with and without active cooling, and the peak temperature is basically located at the initial position of the armature. Without active cooling, the rail axial temperature distribution shows a trend of higher at the gun tail and lower at the gun muzzle. The current density and temperature distribution of rail cross-section show a trend of higher on the rail inner side and lower on the rail outer side, and the diffusion of heat lags behind the diffusion of current. Under the action of active cooling, the rail peak temperature will move to the muzzle along the armature moving direction, and there is a “thermal inversion” phenomenon. The rail cross-section temperature drops faster, and the lowest temperature region appears near the middle cooling channel. Active cooling has different effects on rail temperature in different temperature parts. In the high-temperature part, the rail temperature decreases monotonically with the increase of cooling water flow velocity, increasing the water velocity can accelerate the decline of rail temperature. In the middle-temperature parts, the variation trend of rail temperature is different with different water flow velocities. At low water velocity, the rail temperature increases gradually. When the water flow velocity is greater than 0.75 m/s, the phenomenon of “thermal inversion” will occur. i.e., the rail temperature increases first and then decreases. In the low-temperature part, “thermal inversion” will occur at different flow velocities, that is, the rail temperature increases first and then decreases. When the water flow velocity is greater than 1.0 m/s, the improvement of rail cooling effect will no longer be obvious. It is suggested that the appropriate water flow velocity is 0.75–1.0 m/s under the present experimental conditions.

A Novel Technique for Dynamic Analysis of an Electromagnetic Rail Launcher using FEM Coupled with Simplorer

The performance of a rail gun depends on the current density distribution over the rail and armature as it determines the force that accelerates the projectile of the rail gun. A finite element method (FEM) coupled with Simplorer was developed to model and study the performance of the rail gun. The rail gun was modeled using an ANSYS eddy current field solver to determine the current density distribution and equivalent rail gun circuit for the given rail gun geometry. The armature velocity was then calculated using Simplorer by coupling the obtained equivalent rail gun circuit and exciting the rails using a capacitor-based pulsed power supply (PPS) system. The FEM coupled with Simplorer method was verified by numerical calculations for the rectangular rails and also with other researchers’ value, and that showed a good agreement between the results. Further, the current density distribution over rails and armature and velocity of the armature was calculated for different rail cross sections such as circular concave, circular convex, rectangular concave, rectangular convex, T-shaped concave, and T-shaped convex with a C-shaped armature. It was observed that the circular convex rail gun with C-shaped armature showed minimum current density distribution and gives a higher value of armature velocity compared with other rail gun structures. Thus, the circular convex armature was found to be suitable for the electromagnetic (EM) rail gun launchingsystem.

Investigation on the Spatial-Temporal Distribution of Electromagnetic Gun Rail Temperature in Single and Continuous Launch Modes

In order to study the spatial-temporal distribution characteristics of electromagnetic rail gun temperature, based on moving grid processing method and mod function method, a 3-D geometric model of electromagnetic rail gun under single launch mode, a 2-D geometric model of electromagnetic rail gun under continuous-fire mode, and the corresponding transient electromagnetic field-temperature field coupling model are established by using the finite element analysis software COMSOL Multiphysics, and the temperature spatial-temporal distribution characteristics in the rail-armature contact area, cross section of rail, and along the rail axis is simulated under single launch and continuous launch. The results show that, under the conditions of single launch and natural cooling, the high temperature area in the rail-armature contact surface is located at the rear of the armature due to the skin effect. The temperature distribution along the axial inner side of rail tends to be higher near the tail and lower near the muzzle, it increases with time, but the peak temperature does not exceed the melting point of copper. Under the continuous launch and natural cooling, after five launches, the peak temperature of the rail increases to 709 °C, which is close to the melting point of copper. Continued launching will cause rapid accumulation of heat in the rail and a rapid increase of peak temperature, resulting in shortened life of the launcher and even launch failure. Therefore, without active cooling measures, the electromagnetic rail gun cannot be used in actual combat. The results of the study are an important guide for the design and thermal management of the cooling system of electromagnetic rail gun.

Smart Railway Traffic Monitoring Using Fiber Bragg Grating Strain Gauges.

There is today ample evidence that fiber Bragg gratings (FBGs) distributed along a railway track can provide robust axle counting and bring numerous assets compared to competing technologies in this practical environment. This work brings two relevant originalities with respect to the state-of-the-art solutions. First, a study of the strain distribution in the rail cross-section is performed to determine the sensitivity according to the charge and the position on the rail. Secondly, the technology is deployed along the rail track as a smart object where the sensor head is composed of four FBG wavelength-division-multiplexed in a single telecommunication-grade optical fiber and interrogated by a miniaturized read-out device. Two FBGs ensure the detection of the train direction and another two bring the required redundancy to reach a safety integrity level (SIL) 4. The read-out unit has been specifically developed for the application and contains a vertical-cavity surface-emitting laser (VCSEL) and a photodiode driven by a high-speed microprocessor unit that processes the data and communicates the useful information, i.e., the number of axles. On-field tests confirm that the proposed approach makes the installation process easier while it democratizes the technology.

Influence study of rail geometry and track properties on railway rolling noise

Wheel/rail interaction generates an excitation due to the roughness present on the surface of both components that produces vibration and consequently rolling noise. In this work, the railway track properties that most influence rolling noise are identified and this influence is analysed to reduce noise emission. The acoustic calculation methodology consists of characterizing the wheel using finite element techniques and the track using periodic structure theory. The influence of the track properties on the sound radiation is analysed by means of statistical techniques applied to the acoustic power results of different track configurations. To achieve this, the rail cross-section geometry is parameterized and numerous simulations are carried out by modifying these geometric parameters and the viscoelastic properties of the track components. Considering the contribution of the wheel, rail and sleeper, the results obtained indicate that the total radiation can be reduced by up to 7.4 dB(A) through an optimal combination of the track design parameters, compared to the worst combination found. In particular, the rail pad stiffness is shown to be the most influential parameter in the sound radiation.

Numerical Study on Propagative Waves in a Periodically Supported Rail Using Periodic Structure Theory

This paper presents the numerical study on propagative waves in a periodically supported rail below 6000 Hz. A periodic rail model, which considers the effects of both the periodic supports and the rail cross section deformation, has been established based on the periodic structure theory and the finite element method. Two selection approaches are proposed to obtain the concerned dispersion curves from the original calculation results of dispersion relations. The differences between the dispersion curves of different support conditions are studied. The propagative waves corresponding to the dispersion curves are identified by the wave modes. The influences of periodic supports on wave modes in pass bands are revealed. Further, the stop band behaviors are investigated in terms of the bounding frequencies, the standing wave characteristics, and the cross-sectional modes. The results show that eight propagative waves with distinct modes exist in a periodically supported rail below 6000 Hz. The differences between the dispersion curves of periodically and continuously supported rails are not obvious, apart from the stop band behaviors. All the bounding-frequency modes of the stop bands are associated with the standing waves. Two bounding-frequency modes of the same stop band can be regarded as two identical standing waves with the longitudinal translation of the quarter-wavelength, one of which is the so-called pinned-pinned resonance.

Analysis of subsurface layer formation on a pearlitic rail under heavy haul conditions: Spalling characterization

The depth of rolling contact fatigue (RCF) defects in railways plays a significant role in the rail lifetime, affecting rail maintenance procedures due to the amount of material to be removed from the railhead. Therefore, a precise characterization of the damaged rail is needed to define the optimal material removal. In the present study, an ex-service and damaged rail that contained defects due to RCF was investigated in detail. The microstructural characterization was conducted on particular sites using optical microscopy (OM), scanning electron microscopy (SEM), SEM with focused ion beam (SEM-FIB), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Three layers were identified at the rail cross section: a white etching layer (WEL) was the topmost layer and comprised martensite; a transitional layer (TL) with martensite and retained austenite was identified below the WEL; followed by a severely plastically deformed layer with refined grains and a large number of high-angle boundaries (HABs) and elongated pearlite colonies. In this last region, {111} and {110} were common crystallographic orientations. A gradual decrease in the hardness was observed along these layers. The WEL achieved a hardness value of 12 GPa, while the TL had an average value of 8 GPa, and measurements on the plastically deformed layer indicated a hardness of 6 GPa. The observed microstructural transformation suggests that thermal loading led to a thermally produced WEL (TP-WEL). The brittle nature of the WEL and the surface shear deformation and high levels of stress promoted the nucleation of surface cracks and propagation of them through the WEL. The presence of the different metallurgical phases in the TL promoted a change of crack orientation, leading to material detachment.

THE INFLUENCE OF THE NUMBER AND POSITION OF DOWELS ON THE BENDING MOMENT CAPACITY OF HEAT-TREATED WOOD DOWEL JOINTS

In this work, the influence of the number of dowels and the option to place the dowels in the cross section of part on the bending moment capacity of heat-treated wood dowel joints was analysed. The joints, which were made of heat-treated ash, were tested by means of a universal testing machine.The ultimate failure load and the moment arms were used to figure out the bending moment capacity of the joints loaded in compression or in tension. The number of dowels affected the tensile strength of the L-shaped heat-treated wood joints. The modality to place the dowels in the cross section of rail, namely, in collinearity or in a triangular shape, did not significantly affect the strength of the heat-treated wood dowel joints.

Determination of temperature stresses in CWR based on measured rail surface temperatures

The main aim of conducted research is determination of temperature stresses due to the uneven temperature distribution in CWR. This paper presents a methodology for determination of temperature stresses in CWR based on (1) measurement system developed by the authors for measurement of rail surface temperatures, and (2) coupled transient thermal-stress analysis for simulation of rail temperature field and corresponding stresses. The main advantages of the proposed methodology are high sensitivity to the small temperature variations, taking into account the effect of thermal inertia, as well as measurement of single input parameter - rail surface temperature. The obtained experimental results showed lower rail temperatures in sleeper zones and rail foot along CWR, which emphasize the effect of heat transfer between rail and sleeper, as well as rail foot and ballast. These effects of heat transfer directly influence the decrease of temperature stresses in the mentioned zones of CWR. The maximum values of simulated temperature stresses are up to 16% less in the centre of gravity of railhead, up to 9.8% less in the centre of gravity of rail foot, and up to 0.2% less in the centre of gravity of rail web, compared to the common engineering calculation. In addition, the maximum value of simulated temperature force, based on temperature stresses in the rail cross-section, was up to 5.3% less than the value obtained in the common engineering calculation.

Current Distribution in Railgun Rails Through Barycenter Filament Model

In this article, we present a novel measurement method to estimate the current distribution in electromagnetic rail launchers. A loop array is magnetically coupled with the railgun to reconstruct the current barycenter position, from which we can argue on the current distribution through the rail cross section. After describing the adopted measurement procedure, we present the results of an experimental analysis performed using the NGL60 rail launcher at the laboratories of the French-German Research Institute of Saint-Louis (ISL). We also compare the experimental results with finite-element simulations, and we show the agreement during the current pulse transient. Finally, we provide a measurement uncertainty analysis performed using Monte Carlo method.