Rail Track Research Articles

Nonlinear autoregression-based non-destructive evaluation approach for railway tracks using an ultrasonic fiber bragg grating array

The safe operation of railway systems relies on rapid and accurate non-destructive damage detection and evaluation techniques to help rule out potential threats brought by rail track damages. In this paper, an innovative fiber Bragg grating (FBG) array-based sensing system is developed for rail defect inspection by integrating the ultrasonic testing technology, and a nonlinear autoregressive neural network with exogenous inputs (NARX) is proposed for rail damage detection based on measured ultrasonic signals. The developed sensing system can realize the high-speed and multiplexed ultrasonic signals demodulation. The NARX is proposed to process the ultrasonic signals obtained by the developed sensing system, and a specified probabilistic damage sensitive feature (DSF) is tailored to indicate rail health status, derived from the probability density function (PDF) of NARX prediction errors. To verify the proposed sensing system and damage identification algorithm, experimental studies considering four rail conditions (i.e., intact, cracked, bump, and welded conditions) are conducted in this study. First, baseline NARX models are priorly trained using ultrasonic signals acquired on an intact rail segment; then, DSFs corresponding to each condition are calculated enabling effective rail damage diagnosis. To optimize the training parameters of NARX models, three different training functions are utilized to select the most appropriate parameters that are sensitive to rail damages. Last, large-scale testing is conducted, further proving the applicability and reliability of the proposed rail damage evaluation approach. Through this study, it is suggested that integrating high-performance sensing technologies with effective data processing tools would maximumly enable efficient and robust non-destructive testing, especially on important infrastructures such as rails.

Rail Wear Evolution on Small-Radius Curves under Mixed Traffic Conditions, In-Field Investigations

This paper’s aim is to assess the rail wear evolution of railway tracks under mixed traffic conditions for sharp curves. Field investigations were conducted over a period of five years, at 800 points on a rail track, for two curves that underwent maintenance interventions: sleeper and rail replacements during measurements. Lateral and vertical wear measurements were monitored with mechanical instruments, and Prokon and Sap simulations were performed in order to determine the bearing capacity of the rail at different stages of wear. The results obtained after five years of investigation show wear speed propagation on the outer rail of small-radius curves as well as the bending moments and admissible stress variation. At more than 18% of the studied points, lateral wear exceeded the maximum admissible limit, showing a faster propagation speed on the outer rail compared to the vertical wear rate.

Evaluation of strength of intermediate supports of string rail track structure at uSky center in Sharjah (UAE)

The paper presents strength analysis of the general arrangement and units of intermediate supports of the string rail track structure at the uSky Center in Sharjah (UAE).
 Aim: Strength analysis of intermediate supports under the impact of a complex of loads from the track structure, vehicle and wind load.
 Methods: The calculation was performed using the finite element method using Midas Gen and ANSYS programs.
 Results: Analysis of the calculation results showed sufficient reliability of all elements of the intermediate supports.

Entrapment and extraction of wheelchairs at flange gaps with and without flange gap fillers at pedestrian railway crossings

Purpose Where pedestrian crossings meet rail tracks, a flange gap allows the train wheel flanges to pass. This gap can be hazardous for wheelchair users as castor wheels may become trapped. While compressible gap fillers can eliminate the flange gap, fillers are subject to wear, pose a derailment hazard to light rail vehicles and can strip grease from passing wheels. These issues could be mitigated by partially filling the flange gap with a compressible filler. The aim was to investigate the risk of entrapment and ease of extraction of wheelchair castors from flange gaps fully and partially filled with compressible fillers, and assess ride quality. Materials and methods Entrapment risk and ease of extraction for four wheelchairs were tested at various crossing angles with flange gap fillers. Twelve wheelchair users tested ease of extraction and ride quality for partially and fully filled flange gaps. Results It was found that risk of entrapment is low if a standards-compliant crossing with open flange gaps is traversed in a straight line. However, castors can become trapped if the user alters direction to avoid an obstacle or if the crossing surface is uneven. Once trapped, castors are extremely difficult to remove without external assistance. Conclusions Flange gap fillers that reduce the gap to 10 mm or less eliminate entrapment while retaining acceptable ride quality. Filling flange gaps or leaving a residual gap depth of less than 10 mm is the best option to eliminate risk of entrapment and ensure good ride quality for wheelchair users. IMPLICATIONS FOR REHABILITATION Rail crossings flange gaps pose an entrapment hazard for wheelchair users Partial or complete flange gap fillers may reduce entrapment but require research Rehabilitation professionals need to educate wheelchair users on techniques to cross flange gaps safely Consumers and health professionals can consult rail operators to partially fill flange gaps

A full 3D reconstruction of rail tracks using a camera array

This research addresses limitations found in existing 3D track reconstruction studies, which often focus solely on specific rail sections or encounter deployment challenges with rolling stock. To address this challenge, we propose an innovative solution: a rolling-stock embedded arch camera array scanning system. The system includes a semi-circumferential focusing vision array, an arch camera holder, and a Computer Numerical Control machine to simulate track traverse. We propose an optimal configuration that balances accuracy, full rail coverage, and modelling efficiency. Sensitivity analysis demonstrates a reconstruction accuracy within 0.4 mm when compared to Lidar-generated ground truth models. Two real-world experiments validate the system's effectiveness following essential data preprocessing. This integrated technique, when combined with rail rolling stocks and robotic maintenance platforms, facilitates swift, unmanned, and highly accurate track reconstruction and surveying.

A Study on the Influence of Steel Structures in Concrete Subgrades on the Detection of Subgrade Distresses by Ground-Penetrating Radar

The detection of subgrade distresses in ballastless track railways poses a formidable challenge due to the presence of steel interference caused by the unique characteristics of high-speed rail track slabs and the dense arrangement of the steel reinforcement mesh within them. Here, we aim to examine the influence of varying distribution patterns of steel reinforcement in ballastless tracks on the detection of subgrade distresses using ground-penetrating radar. Through a combination of on-site testing and forward modeling, this paper analyzes the interference of steel reinforcement on the detection of voids beneath the steel using electromagnetic waves. The research findings reveal that incident electromagnetic waves from the ground-penetrating radar experience attenuation near steel reinforcements, with only a fraction able to penetrate the surface layer and propagate into the subsurface through interstitial gaps between the reinforcing bars. Furthermore, this influence diminishes as the spacing between the reinforcing bars increases and the bar diameter decreases. When steel bars are distributed on the upper and lower layers, the detection results of the lower void are most significantly influenced by the interlocking of the steel bars in the two layers. These research results can offer theoretical and technical support for the detection of ailments in high-speed railway subgrades.

Investigation of the Most Positions Affected in Rail Track When the Modulus of Elasticity of the Ballast Layer is Changed

Abstract The railway is one of the cheapest methods to transport people and heavy goods. It is safer than highways. In Iraq, many railways connect the south country with the middle and north, which are old, damaged, and need to continued maintenance. Iraq needs to construct new lines of the rail track with low-cost, less maintenance, and highly stable structure, which requires understanding the behavior of rail track under train loads and the pattern of distribution of deformations, stresses, and strains inside the body of rail track and know the layer which more effected by changing the strength of ballast layer by change modulus of elasticity of it. This paper investigates the influence of modulus of elasticity of the ballast layer on the behavior of railways and the positions of deformation, stresses, and strains in the rail track which is most affected by the change in the modulus of elasticity and the value of the effect. The finite element approach was considered in this study using Abaqus Ver. 6.14-4 program. The investigation outcomes displayed that when the ballast layer’s modulus of elasticity E increase by 100 MPa, the value of deformation in the rail track is affected in all layers, and the value of decreased is 6.8 % for rail, 6.9 % for ballast, and 6.7 % for the sub-ballast layer. Therefore the strain of the sub-ballast layer is affected by the change modulus of elasticity of the ballast layer more than other ballast and subgrade. Also, the result shows that stresses in the rail are the only part of the rail track affected by the change in the ballast layer’s modulus of elasticity E, while the other layers are unaffected. So the increase in E of the ballast layer affects the layer beneath it, which is the sub-ballast layer.

Analysis of the impact of rail head wear on railway superstructure stability

Continuous welded rail track (CWR) is a superstructure construction of the railway that withstands significant compressive forces from the longitudinal extension of the rails due to temperature changes, ensuring the safe railway operation. The applicable for the Bulgarian railway system methodology for determining the critical compressive force at which the CWR loses stability has been examined. Different types of rails with their respective design parameters, important for the force calculation, have been taken into consideration. The considered design parameters, as moment of inertia and sectional modulus of the rails, change during operation due to the rail head wear. The aim of the article is to examine specific examples of railway tracks on curves, analyzing the impact of the changed operational design parameters of the rail on the stability of the track. The operational and geometric parameters of the railway track have been considered.

Analysis on crack propagation of CRTS III slab ballastless track under temperature loads and freeze–thaw deterioration

In seasonal frozen region, the Chinese Rail Track System (CRTS) III slab track is subject to temperature loads and freeze–thaw deterioration, which may lead to further expansion of microcracks in track slabs. Mechanical parameters of track structure materials after freeze–thaw cycles are obtained through the experimental tests in this study. A finite element model of CRTS III slab track on subgrade section is then established by ABAQUS. Based on fracture mechanics theory, the types of cracks generated in track slabs under temperature loads and freeze–thaw deterioration, and crack expansion law are analyzed by using extended finite element method. The results show that under temperature loads, the expanded cracks in track slab are mainly Mode Ⅰ - Opening mode. There is the possibility of expansion for transverse cracks with larger size on the upper surface of track slab under negative temperature gradient load. Vertical capillary cracks at the location where track slab is bonded to self-compacting concrete are more likely to expand. Freeze-thaw deterioration will reduce the difference between the SIFs of cracks and fracture toughness of track slab material, which has a certain promotion effect on crack expansion.

A comparative study of geosynthetically reinforced earth foundations in multi-utility transportation infrastructure for high-speed railways

A high-quality railway track resting on an excellent foundation is required to support high-speed railway transportation. The foundations of high-speed railway tracks are generally constructed on the lifted embankment with the improved ground using different reinforcement agents like geosynthetics and rigid lateral support. The present study performed dynamic finite element simulations on a ballasted rail track laid over a geosynthetically reinforced embankment with and without facing wall support. Three foundation geometries were analyzed to examine the effect of facing wall support and geosynthetics on the lateral resistance of the foundation. An area loaded with a constant pressure was moved at a constant speed, causing the load motion at different speeds in the 90–360 km/h range. Different parameters were calculated at node paths to help understand the lateral effect of moving load. The results showed that the lateral resistance based on nodal acceleration and velocity increased with facing wall support in the range of 40%–57%. Any increment over the minimum facing wall thickness of 300 mm does not significantly increase lateral resistance. Geosynthetics provided a vital function in the foundations with a less bulk volume of soil and increased the lateral resistance by 10%.

Typification of Projects for Development of High-Speed Rail

The emerging demand for improving consumer parameters of rail passenger transport leads to the need to build a dedicated railway infrastructure for passenger trains with speeds exceeding in some sections 250 km/h. The high capital intensity of dedicated infrastructure development projects imposes significant restrictions on their scope and financial feasibility. The geographically determined location of urban agglomerations in European and Asian countries has led to formation of many approaches to the routing of lines for high-speed passenger transportation.The projects for development of dedicated high-speed railways being developed in various countries differ in their technical, technological, and operational characteristics. The use of different approaches has led to different efficiency of the passenger traffic, expressed in the demand of passengers for transportation.A structural analysis of existing high-speed transportation projects allowed revealing general patterns of their development. By the number of operational tasks arising with regard to movement of trains, the phases of traffic development were divided into linear, tree­like and network stages. Thus, when moving from the linear structure of a high-speed rail, an additional problem arises of trains passing from the main track to the secondary one. The transition to the network stage can result in emergence of parallel passages rail tracks between urban agglomerations.To generalise the experience of operating high-speed systems in the world, the article describes the developed method that allows comparing different projects for organising high-speed rail with each other. The comparison is made according to the main characteristics of traffic: travel time between separation points, the traffic speed, the total length of the railway line. Identification of the patterns inherent in various projects for development of high-speed rail will make it possible to compare their technological parameters, to identify the scope of rational use of high-speed lines and areas of competition with other core types of transport.

The Impact of Anisotropic Properties of the Rail Track Superstructure on the Parameters of Dynamic Settlement of Bridge Approaches

Numerous artificial structures, bridges, overpasses, tubes, channels, chutes are operated on railway networks. Artificial structures are considered to have a longer life cycle and thus will need during it overhaul and reconstruction with the use of modern technology. Currently, there is an increase in axial load and traffic speed, the makes even more relevant the solution of tasks referring to dynamic impact of trains on artificial structures and superstructure. See the features of construction and maintenance of rail track sections at the approaches to bridges, the respective problems merit special consideration.The research which results are presented in the article was dedicated to the impact of the anisotropy of the track superstructure on the parameters of the dynamic settlement of sections of transitional stiffness located at the approaches to bridges and built using bottomless box culverts.The research proposed to model the railway track within the transitional section as a set of flat elements of constant thickness, while each of them is regarded as a anisotropic plate supported by deformable foundation with its own deformability rates. By setting boundary conditions for individual fragments of the track structure and varying the anisotropy coefficients that determine the ratio of mechanical characteristics in different directions of anisotropy, it is possible to select necessary rail track stiffness rates for a section at bridge approaches, that paves the way to further research on structural features of designing and arrangement of those structures.

A Review on Composite Railways Sleepers; Recent Developments, Limitations & Future Perspectives

The current review on a number of composite railway sleeper technologies have been developed, there are still few places where they are used in rail tracks. This report thoroughly examines recent advancements in composite sleepers and discusses the major obstacles to their broad adoption and use. Currently, there are a variety of composite sleeper technologies on the market, ranging from those made of recycled plastic that have few or no fibers to those that have a lot of fibers. Although recycled plastic sleepers are inexpensive, employing them poses significant difficulties because to their poor stiffness, strength, and dynamic qualities, which are frequently incompatible with those of timber. The exorbitant cost of high-fibre sleepers, on the other hand, prevents their widespread use. Further limiting their use is the lack of information on the historical long-term performance of these new and alternative materials. This research also presents potential design strategies for resolving the obstacles to the use and adoption of composite sleeper technologies.

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

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

Comparison of regenerative braking energy recovery of a DC third rail system under various operating conditions

Conducting simulations prior to real-world testing is essential for the planning and development of rail systems. However, accurately representing the train trajectory characteristics resulting from the railway power system and the dynamic load changes based on the train position can be challenging. The power exchange between trains and the fluctuating rail resistance between them add to the computational complexity. Given these challenges, the aim of this study is to develop a comprehensive model of DC third rail systems based on the operational requirements and parameters of the MRT Line 2 Malaysia. Moreover, the simulation method should be adaptable to investigate potential energy savings through regenerative braking systems, thereby maximizing the energy efficiency of electric railways. This study outlines the development of a framework that models the power flow within an electric rail network using a specific case study example. A simulation is presented with 15 trains operating on a double rail track to validate the model for multiple train operations. Notably, the simulation methodology developed in this research is unique compared to other approaches found in relevant literature. It integrates both the power system and train trajectory, incorporating actual system information from a practical DC third rail system to generate precise trajectory outcomes. The results show that implementing a regenerative braking energy recovery system in all traction power substations (TPSSs) has the potential to achieve significant electrical energy savings of up to 55.75% for the entire system.

NanoDet Model with Adaptively Weighted Loss for Real-time Railroad Inspection

Monitoring the railroad’s components is crucial to maintaining the safety of railway operations. This article proposes a novel, compact computational vision system that works on edge devices, designed to provide precise, instantaneous assessments of rail tracks. This model reconfigures the teacher-student guidance system inherent in NanoDet by incorporating an innovative adaptively weighted loss (AWL) in the learning phase. The AWL assesses the caliber of the teacher and student models, establishes the weightage of the student's loss, and dynamically adjusts their loss contributions, directing the learning procedure towards effective knowledge transfer and direction. In comparison with cutting-edge models, our AWL-NanoDet boasts a minuscule model size of less than 2 MB and a computational expense of 1.52 G FLOPs, delivering a processing time of less than 14 ms per frame (evaluated on Nvidia’s AGX Orin). Compared to the original NanoDet, it also significantly enhances the model's accuracy by nearly 6.2%, facilitating extremely precise, instantaneous recognition of rail track elements.

ІСТОРИЧНІ ОСОБЛИВОСТІ ФОРМУВАННЯ ОДЕСЬКИХ ВОКЗАЛІВ

The historical features of the formation of Odessa railway stations are considered. It was discovered that the history of railway construction in Ukraine began in 1854 with the construction of a railway branch from Odessa to Parkan, which was the beginning of the rich history of the Odessa railway and railway stations. There were 5 stations in total: "Freight" – a warehouse station and a large station (1865); "Odessa-Main" railway station (first – 1884, existing – 1944 – 1952); "Odessa-Port" railway station (1907 – 1910); Kuyalnytsky station (1873); "Odessa- Passenger" railway station (1914). And a few more temporary and auxiliary ones: "Narkhoz" Station (1944); Station "Odessa-Mala" (1903); Station "Odessa-East" (1970). One of the main achievements of the research is the discovery and study of the formation of the "Bread Town" – on the outskirts of the city of Odessa at the beginning of the 20th century, which was a large warehouse complex, where a dense building of warehouses, warehouses and shopping areas was formed between the railway tracks. The remnants of the Bread Town quarter setting are now city blocks, retaining working rail tracks only at the edges. In the realities of the present time, the importance of the Ukrainian railway and its role in the development of the economy and the process of restoration of the affected cities and territories were revealed. And also the question of the need to reform the structure of the railways arose acutely: the cargo and passenger flow, connected with military realities, increased many times and forced to change the main modes of transportation. It turned out that the new reality requires greater adaptability from the transport infrastructure.

Early detection of thermal instability in railway tracks using piezo-coupled structural signatures

Rail accidents caused by rail track derailments have been a growing concern due to repetitive thermal changes resulting from high temperature stresses in rails due to rail traction and environmental thermal variation. This leads to thermal buckling, which can result in catastrophic failure. Structural health monitoring (SHM) using the electromechanical impedance (EMI) technique has emerged as a promising technology to detect structural deterioration and its severity before it leads to failure. This study used piezoelectric sensors to collect piezo-coupled structural signatures of different rail-joint bars for high-temperature repetitive thermal cycles, which were then analyzed using an impedance analyzer. The results show that the piezo-coupled signatures could identify structural changes, and the damage metric, could be employed for continuous monitoring of structural rail defects due to excessive thermal stress and residual strain. The method also derived piezo-equivalent structural parameters, such as mass, stiffness, and damping, which were very satisfactory in detecting significant changes and consequent damage. Overall, this study presents a pre-emptive experimental method that can see thermal deterioration and instability in rails and rail joints, thereby reducing the risk of rail accidents caused by derailments.

A data-driven hybrid approach to generate synthetic data for unavailable damage scenarios in welded rails for ultrasonic guided wave monitoring

Developing reliable ultrasonic-guided wave monitoring systems requires a significant amount of inspection data for each application scenario. Experimental investigations are fundamental but require a long period and are costly, especially for real-life testing. This is exacerbated by a lack of experimental data that includes damage. In some guided wave applications, such as pipelines, it is possible to introduce artificial damage and perform lab experiments on the test structure. However, in rail track applications, laboratory experiments are either not possible or meaningful. The generation of synthetic data using modelling capabilities thus becomes increasingly important. This paper presents a variational autoencoder (VAE)-based deep learning approach for generating synthetic ultrasonic inspection data for welded railway tracks. The primary aim is to use a VAE model to generate synthetic data containing damage signatures at specified positions along the length of a rail track. The VAE is trained to encode an input damage-free baseline signal and decode to reconstruct an inspection signal with damage by adding a damage signature on either side of the transducer by specifying the distance to the damage signature as an additional variable in the latent space. The training data was produced from a physics-based model that computes virtual experimental response signals using the semi-analytical finite element and the traditional finite element procedures. The VAE reconstructed response signals containing damage signatures were almost identical to the original target signals simulated using the physics-based model. The VAE was able to capture the complex features in the signals resulting from the interaction of multiple propagating modes in a multi-discontinuous waveguide. The VAE model successfully generated synthetic inspection data by fusing reflections from welds with the reflection from a crack model at specified distances from the transducer on either the right or left side. In some cases, the VAE did not exactly reconstruct the peak amplitude of the reflections. This study demonstrated the potential and highlighted the benefit of using a VAE to generate synthetic data with damage signatures as opposed to using superposition to fuse the damage-free responses containing reflections from welds with a damage signature. The results show that it is possible to generate realistic inspection data for unavailable damage scenarios.

Validation of a railway rolling noise model on a system with slab track and resilient wheels

This study investigates rolling noise emissions using an analytical model of the Seattle Sound Transit Light Rail system developed using Train Noise Expert (TNE) software. Measurements of track frequency response, decay rate, rail and wheel roughness were used to determine model input parameters. Wheel modal test results were used to characterize the wheels. Wayside noise and track vibration measurements during revenue service train passbys were used to experimentally validate the model. The average difference between measured and predicted overall passby LAeq noise at a position immediately adjacent to the track was 0.1 dBA (average from four scenarios, i.e. two surface track sites with two train types). Inspection of the predicted versus measured noise spectra indicates the model does not exactly match the measured spectrum in every frequency band, however the correlation with overall spectrum shape is good in the frequency bands that contribute most to the overall A-weighted level. It is concluded that the model provides an accurate representation of the most relevant physical rolling noise factors and is reliable with resilient wheels and light rail vehicles on ballast and slab track.