Rail Fastening Research Articles

Features of the influence of intermediate rail fastenings on the operational durability of rails

Heat-strengthened rails of the R65 type are the main type of rails used on the railway network of Russian Railways. Reducing the number of cropped and acutely defective rails is possible due to the rational use of the design features of intermediate rail fasteners and their current content.The article presents study results of the stiffness influence of intermediate fasteners on the operational durability of rails. The general statistics of the use of various types of intermediate rail fastenings on the network of Russian railways is considered. The main results of previously published studies on the effect of the stiffness of intermediate rail fasteners on the accumulation of contact fatigue damage in rails are briefly presented.Calculations of the accumulation of contact-fatigue damages in rails, carried out by the authors, are based on the data on the vertical and horizontal transverse stiffness of intermediate rail fastenings obtained from the results of bench tests. Calculations of the accumulation of contact-fatigue damage were carried out using the “Universal Mechanism” software package. In the process of modeling, four types of intermediate rail fasteners were considered: ARS-4, ZhBR-65Sh, ZhBR-65PShM and W-30. Calculation results were obtained for a curve with a radius of 650 m on a continuous welded track section.

Research and application of automatic detection of rail fastener damage

Research and application of automatic detection of rail fastener damage

Improved indirect measurement of the dynamic stiffness of a rail fastener and its dependence on load and frequency

The dynamic stiffness of rail fasteners has a significant effect on the noise radiated by the rails as well as the vibration transmitted to the underlying structures, such as bridges, tunnels or track at grade. This study investigates the load- and frequency-dependence of a WJ-2A fastener which is commonly used in urban rail transit systems in China. This is a two-stage fastener with a rail pad and a baseplate pad separated by a steel plate. Results are obtained using the indirect measurement method in the frequency range 30 to 1000 Hz. The dynamic stiffness of the individual components is investigated as well as that of the whole fastener system and the combined stiffness of the components is verified by comparison with the whole fastener system. A numerical model of the test rig is used to provide understanding of various artefacts that are observed in the measurements and corrections are proposed to minimise their effects on the measured results. These allow for the differences between the response at the measurement positions and at the ideal positions at the interfaces between the fastener system and the rig. The stiffness magnitude of the rail pad, baseplate pad, and whole fastener system increases strongly with increasing static preload and increases weakly with increasing frequency; it is important to take these effects into account in prediction models for noise and vibration. The damping loss factors are not strongly dependent on preload or frequency. To describe the frequency-dependence, a fractional derivative Kelvin-Voigt (FDKV) model is introduced and is fitted to the dynamic stiffness with the help of a genetic algorithm method. The dynamic stiffness of the whole fastener system is influenced by both the rail pad and the lower baseplate pad. It is important to take account of both of them, as well as the internal resonance of the baseplate assembly which appears at around 1 kHz.

Testing research on frequency-dependent characteristics of dynamic stiffness and damping for high-speed railway fastener

In this paper, the Vossloh W300 fastener currently used in China's high-speed railway is taken as the research object. Combined with the requirements of ISO 10846 series standards and the knowledge of the author, to the best of the authors knowledge, the first high-frequency dynamic stiffness test system for elastic elements of rail fastener has been successfully developed and built. By taking the influence of preloading into consideration, the vertical and lateral dynamic frequency-dependent stiffness and loss factor of high-speed railway W300 fastener at 5~1250 Hz were obtained through the 1:1 test model coupling test method for the first time. Referring to the prediction method of high-speed railway wheel-rail vibration and noise, and factoring in the high-speed rotating, the infinite length of plate track structure and high-speed movement of sound source to wheels, the Kelvin - Voigt simulation sub-model of fastening system was added to predict and analyze the difference between the total sound pressure levels of the wheel and rail that is relative to the standard point under the constant stiffness and frequency-dependent stiffness of fastener. The results indicate that the frequency-dependent characteristics of fastener stiffness have significant impact on the spectrum of wheel-rail interaction forces, total sound pressure levels of rail and wheel-rail. The total sound pressure level of the wheel-rail relative to standard point, which factors in the frequency-dependent stiffness of fastener was approximately reduced 2.6 dB, that is, the frequency-dependent stiffness of fastener can rectify the overestimation of wheel-rail sound pressure level by stiffness coefficient.

Study on mechanical behaviours of rail fasteners and effects on seismic performance of urban rail viaduct

The mechanical properties of rail fasteners play a key role in rail-structure interaction of urban rail viaduct. To reduce vibration and noise, the damping materials such as rubber cushion pads are used as the assemble parts of the rail fasteners in urban rail viaduct. The use of the damping materials causes the mechanical behaviours of rail fasteners to be different from the traditional ones whose longitudinal stiffness can be simplified as linear elastic, elastic–plastic or bilinear models. It is important to capture the mechanical behaviours of the rail fastener for accurately predicting the nonlinear seismic response of urban rail viaduct. In this paper, the quasi-static and dynamic cyclic tests of three kinds of commonly used rail fasteners (Type WJ-2A, Type DTIII2, and Type ZX-3) in China urban rail transit were conducted to explore the mechanical behaviours of rail fasteners. On this basis, the Hardin-Drnevich model is used to simulate the nonlinear behaviours of rail fasteners. Analysis results showed that the Hardin-Drnevich model could describe the quasi-static and dynamic cyclic response of Type WJ-2A and Type DTIII2 rail fasteners with reasonable accuracy, while its prediction accuracy for Type ZX-3 rail fasteners are relatively lower than others. Moreover, the Hardin-Drnevich model can predict the nonlinear dynamic response of Type WJ-2A fastener under earthquake loading very well. The calibrated parameters of Hardin-Drnevich model were used to the rail fasteners in the nonlinear seismic response analysis of the practical urban rail viaduct, and that were compared with that using idealized elastic–plastic model of the rail fastener. Comparison results demonstrated that, the mechanical constitutive relations of the rail fastener have obvious effects on the seismic performance of rail viaduct, and the effects are more distinct in the longitudinal direction than in the transversal direction.

An accurate method for fast assessment of under slab mats (USM) performance in ballastless track structures

The paper is devoted to testing, modelling and performance assessment of vibration isolation products applied in ballastless track structures. In the first part of the paper, results of laboratory tests of vibration isolation products, such as under slab mats (USM) and under block pads (UBP) are summarised. On their basis, the Fractional Zener Model (FZM) is calibrated and it is shown that the model properly covers the stiffness and damping characteristics of tested materials in a wide frequency range. Then, results of the finite element analysis performed in a frequency domain using the Abaqus code are presented, taking into account the frequency-dependent material characteristics. The analysis concerned a ballastless track structure with a discrete system of rail fastening (embedded block system – EBS) laid on USM. The proposed approach was compared with the simplified one, in which the frequency-dependence of material properties is neglected. The presented modelling methodology, based on outcomes of laboratory tests, makes it possible to compare various vibration isolation systems in a short time. Consequently, it can be considered as a useful engineering tool.

Influence of the Applied Measurement Methodology on the Results of Geometric Measurements of the SB4 Spring Clips

The article presents the results of measurements of the “b” dimension of the SB4 spring clips carried out using three measurement methods that differ in the method and width of the base plate contact. The results obtained are presented and the uncertainty of measurement for each method is estimated. Attention was paid to the issues of the obtained dispersion of the value of the “b” dimension. The tolerated dimensions are discussed. The proposed measurement methods can help to identify shape mismatches of spring clips. Keywords: rail fastening, spring clip, dimensional measurements, clamping force

CLAMPING FORCE OF INTERMEDIATE FASTENERS AND THEIR DETERMINATION

The article considers the main type of intermediate rail fastening used on the railways of Uzbekistan. The elastic characteristics of various types of terminals are presented, as well as a developed measuring device that allows you to evaluate the force of pressing the terminals on the sole of the rail under operating conditions.

Supervised Machine Learning Approach for Detecting Missing Clamps in Rail Fastening System from Differential Eddy Current Measurements

The rail fastening system forms an integral part of rail tracks, as it maintains the rail in a fixed position, upholding the track stability and track gauge. Hence, it becomes necessary to monitor their conditions periodically to ensure safe and reliable operation of the railway. Inspection is normally carried out manually by trained operators or by employing 2-D visual inspection methods. However, these methods have drawbacks when visibility is minimal and are found to be expensive and time consuming. In the previous study, the authors proposed a train-based differential eddy current sensor system that uses the principle of electromagnetic induction for inspecting the railway fastening system that can overcome the above-mentioned challenges. The sensor system includes two individual differential eddy current sensors with a driving field frequency of 18 kHz and 27 kHz respectively. This study analyses the performance of a machine learning algorithm for detecting and analysing missing clamps within the fastening system, measured using a train-based differential eddy current sensor. The data required for the study was collected from field measurements carried out along a heavy haul railway line in the north of Sweden, using the train-based differential eddy current sensor system. Six classification algorithms are tested in this study and the best performing model achieved a precision and recall of 96.64% and 95.52% respectively. The results from the study shows that the performance of the machine learning algorithms improved when features from both the driving channels were used simultaneously to represent the fasteners. The best performing algorithm also maintained a good balance between the precision and recall scores during the test stage.

Dynamic performance evaluation of rail fastening system based on a refined vehicle-track coupled dynamics model

Damage of rail fastening system often occurs due to severe vehicle-track dynamic interactions. To evaluate the dynamic performance of the rail fastening system subject to dynamic interactions between vehicle and track, a refined vehicle-track coupled dynamics model involving an elaborated model of rail fastening clip (RFC) is developed in this work. Firstly, the RFC model is established based on the mode superposition method by which the difficulty in deducing dynamics equation due to the complex shape of RFC can be easily resolved. Then, the mode shape vectors and natural frequencies of RFC which required by the mode superposition method are obtained through a numerical modal analysis, and verified by a modal test. Finally, through the contact relationship between RFC and rail, the RFC model is implemented into the vehicle-track coupled dynamics model. The reliability of the proposed model is supported by a field test data, and the dynamic performances of rail fastening systems along the track subject to vehicle-track dynamic interactions can be efficiently and effectively evaluated. By applying the proposed model, the influences of rail corrugations, vehicle speeds, and rail pad stiffness on dynamic performances of the rail fastening system are evaluated in detail.

Effect of the Depth of Decarburized Layer in SKL15 Tension Clamp on Fatigue Strength

The surface of a quenched and tempered spring steel may have a decarburized layer from which the carbon component has been reduced. The fatigue strength of the decarburized layer is low compared to the base metal, which can easily develop fatigue cracks. Recently, fatigue failure was reported in the tension clamp (SKL 15) of the DFF-300 rail fastening system during use on one urban transit route in South Korea. As a result of measuring the depth of the decarburized layer of the SKL 15 tension clamp where the fatigue failure occurred, a decarburized layer thinner than the manufacturer’s maximum allowable decarburized layer was found in one of the eight tension clamps. To check the depth of the decarburized layer where the fatigue crack may have initiated, the decarburized layer was assumed to be the initial crack, and fatigue crack initiation was assessed based on the linear elastic fracture mechanics. The manufacturer’s maximum allowable decarburized layer depth of 0.2 mm may result in fatigue cracks.

Influence of the Testing Procedure on the Value of the Impact Attenuation of Rail Fastening Systems: an Experimental Study

Railway superstructure components are subject to impact forces caused by irregularities in the rail and wheel or variations in the support stiffness. These imperfections lead to the premature and accelerated deterioration of the track and increase maintenance costs. Generally, to mitigate these dynamic loads, elastomeric rail pads are interposed between rails and sleepers. For each track section, the pad choice is made according to its stiffness, impact attenuation and cost. In this experimental study, eight types of rail pads were characterized using two procedures from EN 13146–3. The results revealed that the rail pad material and geometry affect the impact attenuation ability of the pad and the testing procedure affect the results. It was found that the preload applied is one of the parameters that most affects the impact attenuation value. Appling a preload of 50 kN during the impact attenuation test, which is suggested by the standard, affected this parameter by ranging from between ~2 and ~ 20, depending on the rail pad. Based on these results it is considered that EN 13146–3 should be updated.

Sensitivity study of vibration responses on vehicle body to typical damages of ballastless track structures

A method is proposed to investigate the sensitivity of the vibration responses on vehicle body to typical damages of ballastless track structures based on a coupled rigid vehicle body and flexible track model. Firstly, a coupled rigid vehicle body and flexible track model is established by combining SIMPACK and ANSYS software, and the reasonableness of the model is verified by coupling analysis. And then, the sensitivity of the vibration signals from different parts of the vehicle body to the typical damages of the ballastless track is investigated by simulating several typical damages on the flexible track model, and the feasibility of inversion of track damage based on the responses on vehicle body is investigated. The results show that a reasonable coupled vehicle-track model can be established by combining the finite element and multi-body dynamics method. The changes in the vibration responses of the vehicle body can reflect the typical track damages such as the loosening of rail fasteners, the debonding of CA mortar layer and cracks in track plate. The wheel-set axle box is the optimal location for installing vertical vibration sensors.

Vibration-based damage detection of rail fastener using fully convolutional networks

The rail fastener plays an important role in supporting the rail and isolating the train-track system vibrations. Its damage detection is therefore an inevitable part in railway maintenance to ensure the system performance. Recently, deep learning techniques are widely applied to structural health monitoring, including damage detection of the rail fastener based on visions. However, the vision-based detection is mainly limited to visible damages. To address this limitation, this work presents a vibration-based detection method by introducing the fully convolutional network (FCN) to identify invisible damages of fasteners. Firstly, three damage categories are defined and five damage degrees are equivalently represented by modifying the stiffness and damping coefficients of target fasteners. Then, a vehicle-track vertically coupled dynamics model with variable vehicle speeds is established to obtain axle box accelerations (ABAs) under excitations of fastener damage and track irregularity. Finally, a fastener damage detection network is designed based on the FCN architecture to predict damage degrees by inputting the ABA, the track irregularity and the vehicle speed simultaneously. The detection performance is estimated and the network robustness to noise is analysed. The results show that the proposed method is capable of achieving accurate, real-time and robust identification of the fastener damage.

Semantic-Segmentation-Based Rail Fastener State Recognition Algorithm

Rail fastener status recognition and detection are key steps in the inspection of the rail area status and function of real engineering projects. With the development of and widespread interest in image processing techniques and deep learning theory, detection methods that combine the two have yielded promising results in practical detection applications. In this paper, a semantic-segmentation-based algorithm for the state recognition of rail fasteners is proposed. On the one hand, we propose a functional area location and annotation method based on a salient detection model and construct a novel slab-fastclip-type rail fastener dataset. On the other hand, we propose a semantic-segmentation-framework-based model for rail fastener detection, where we detect and classify rail fastener states by combining the pyramid scene analysis network (PSPNet) and vector geometry measurements. Experimental results prove the validity and superiority of the proposed method, which can be introduced into practical engineering projects.

Assembly Strength Tests of SB4-type Spring Clips

The article discusses the results of assembly strength tests carried out on SB4-type spring clips. Increases in the “b” and “f ” dimensions were observed and the tests were extended to include measurements performed after ten and fifteen assemblies and disassemblies of the spring clip. Special emphasis has been placed on the ability to interpret the obtained results of the clip’s measured clamping force in relation to the applied measurement methodology. Keywords: rail fastening, spring clip, dimensional measurements, assembly strength test, clamping force

ANALYSING ACOUSTIC PROPERTIES OF A SUBWAY TRACK

This paper describes laboratory measurement of acoustic properties of subway track samples, with the main focus on the change of the basic material of selected components of a rail fastening system. They were identical in shape, the only difference was in the material used. A suitable methodology based on measuring the acoustic response to mechanical shock was developed for laboratory measurements. The measured data was assessed with an appropriate mathematical apparatus based on signal analysis methods in the time and frequency domain. Based on the tests performed, the acoustic properties of the structures examined were deter

Numerical Study on Track–Bridge Interaction of Integral Railway Rigid-Frame Bridge

Track–bridge interaction (TBI) is an increasingly essential consideration for the design and operation of railway bridges, especially for the innovative bridge structure systems that constantly spring up over the years. This paper focuses on the characteristics of additional forces in continuous welded rails (CWRs) on the 3 × 70 m integral rigid-frame bridge of the Fuzhou–Xiamen High-Speed Railway, which is a novel high-speed railway (HSR) bridge structure system in China. The differential equations of rail stress and displacement are first investigated and an integrative analysis model comprising of rail, track, bridge and piers is then established. Secondly, the characteristics of representative additional forces are illustrated and the influences of different design parameters are discussed in detail. Furthermore, suitable rail fasteners, optimal layout schemes of adjacent bridges and reasonable stiffness of piers are also studied. The results indicate that the additional expansion force accounts for the largest proportion of additional forces in integral rigid-frame bridges and that resistance reduction obviously weakens the various additional forces caused by the TBI effect, while the broken gap of the rail increases greatly. Small resistance fasteners are recommended to be applied onto this new type of HSR line as these provide reductions in additional stresses of CWRs compared to WJ-8 fasteners. The additional rail stresses after adopting an adjacent span scheme of 4 × 32 m simply supported beams are less than the corresponding stresses in other schemes. The results also show that there is a strong correlation between the minimum threshold value of the pier stiffness and the longitudinal resistance of HSR lines for the integral rigid-frame bridge. This work could serve as a valuable reference for detailed design and safety evaluation of integral rigid-frame bridges.

Analytical Elastic Modeling of Rail and Fastener Longitudinal Response

The rail fastening system plays a critical role in maintaining proper railroad track geometry by transferring vertical, lateral, and longitudinal forces from the rails to crossties. Broken spikes in elastic fastening systems have been linked to inadequate transfer of longitudinal loads, posing a safety risk for timber crosstie ballasted track. Longitudinal track demand caused by passing trains has been investigated in previous research, but the magnitude and distribution of longitudinal fastener loads is not well understood or documented. To address these track component failures and improve fastener design, this paper presents a validated analytical model that estimates longitudinal rail seat loads, advancing current formulations to focus specifically on the rail seat. The validated method was used to quantify the distribution and magnitude of longitudinal loads in both the rail and fastening system caused by passing trains. Further, this paper quantifies the effect of track stiffness, number of powered locomotives, and wheel spacing on these distributions and magnitudes. This information provides valuable insight into the specific type of spike failures that have led to at least ten derailments and the requirement of manual walking inspections on multiple North American heavy axle load railroads as detailed in this paper. Further, this method can be used to quantify the longitudinal fastener loads for different track conditions to advance the mechanistic-empirical track design philosophy for elastic fastening systems.

Effectiveness of Intermediate Rail Fastenings on the Railway Sections of Siberia

Being one of the important elements of the track superstructure, rail fastenings substantially determine the operational reliability of the rail track and the conditions for its interaction with the rolling stock. The reliability of rail fastenings affects the life cycle cost of the track superstructure. Nowadays, the most common types of rail fastenings on the weldless track are ZBR-65 and ARS-4, and the most promising for difficult operating conditions is ZBR-65PShM. In the conditions of increasing overhaul times, a special task is to identify the optimal type of intermediate rail fastening, which will ensure the stability of the rail track throughout the overhaul cycle with the least amount of labor. It is proposed to use the results of assessing the condition of the rail track with measuring cars, in particular, deviations of the 2nd degree (not requiring speed limits) as a criterion for assessing effectiveness. The assessment was made taking into account the cargo intensity and line plan. The article presents the results of assessing the probability of failure-free operation of rail fastenings for types ZBR-Sh, ZBR-PShM, ARS. Using statistics, particular failures are identified for the elements considered rail fastenings. It has been established that the highest probability of failure-free operation is accounted for by the fastening type ZBR-PShM, and the smallest - by ARS. On the basis of the obtained indicators of the fastening reliability, their durability and current maintenance costs, the most rational area of their application is proposed depending on the line plan and cargo intensity.