Rail Joints Research Articles

Use of operational track dynamics logger measurement data on Norwegian railway tracks to analyze rail joints and rail welding degradation

Since 2022, the Bane Nor Measurement train is equipped with a TDL (Track Dynamics logger) designed by SD&M - France. The TDL captures, by means of 4 triaxial accelerometers on the bearings of a bogie and 4 water resistant microphones, both the forces and noise emission generated by the complete Norwegian railway network, automatically and without need for any user interaction. The acquired data (0-20kHz) is processed towards parameters usable for noise mitigation and maintenance planning, and both raw and processed data are transferred through a 4G/5G connection to a dedicated cloud repository. In Norway, about 4000 kilometers of tracks are covered by the TDL, recording parameters for protection of the infrastructure (rails, sleepers, ballast), for troubleshooting annoyance of citizens (noise, vibrations), and for verification of maintenance activities (grinding, tamping, switches, etc.). Roughness spectra (1-50 cm wavelengths), squat detection, and railpad damping properties are some examples of parameters that can be extracted from the data. Here we will focus mainly on detection or rail defects such as squats, studs, and weldings, by applying advanced signal processing such as band filtering, wavelets, and specific issue-detection algorithms. A comparison can be made with other measurement techniques, e.g., laser scanning or high-speed photography.

Damage behaviour of rail flash-butt welding joints under controlled impact kinetic energy

Rail welded joints are a critical component of seamless railway tracks, and they are essential for maintaining the continuity and smoothness of the tracks. However, they also represent weak points in the entire track, which makes these areas susceptible to frequent damage and rail breaks. This study employs an impact wear testing platform with controlled energy to compare and analyse the impact wear characteristics of three different locations (i.e., weld zone, heat-affected zone and base material) on the U75VG flash-butt welding joint. Results indicate significant differences in material properties, such as hardness and microstructure, within different zones of the flash welded rail joints, which leads to varying impact damage behaviours. The heat-affected zones, which are located on both sides of the weld zone, exhibit the weakest ability to resist impact deformation. Thus, these areas are the most vulnerable in the entire welded rail joint and are prone to damages, such as squat. In general, damage in different zones of the welded joint gradually evolves from plastic deformation and local pitting into fatigue wear with delamination as the main failure mechanism, while the surface of the heat-affected zone tends to develop an oxide debris layer. The distinct damages observed in different zones of the welded joint pose challenges to the problem of track irregularities. This study offers a theoretical framework for predicting the evolution of damage in welded joints.

Peculiarities of fracture of welded joints of railway rails of oxygen-converter K76F steel

Peculiarities of fracture of welded joints of railway rails of oxygen-converter K76F steel

Research on long term tracking of centralized power EMU wheel wear and vibration performance

The centralized power EMU is a new type of passenger transportation equipment for ordinary-speed railways in China, which can greatly improve the efficiency of ordinary-speed railway passenger transportation and improve passenger travel conditions. This paper conducts long-term dynamic tracking experiments on this new type of railway passenger car, studying the evolution laws of wheel wear, axle box vibration, bogie frame vibration, and car body vibration during long-term service, and analyzing typical vehicle dynamics phenomena that occur in long-term tracking experiments. Various studies have shown that the vehicle can maintain good lateral stationarity throughout the entire wheel reprofile cycle, and the growth rate of equivalent conicity gradually slows down as the mileage increases; However, when the mileage after wheel reprofiling is large, harmonic vibration may occur in individual sections of the frame, leading to abnormal vibration of the control car body at 10 Hz. The vertical vibration of the axle box will significantly increase at the rail joint, and its 70 Hz vibration is transmitted to the frame through the experiment suspension, stimulating the bending mode of the crossbeam of the frame, resulting in a more obvious 70 Hz vibration in the vertical direction of the frame. The RMS of the axle box, frame, and body sleeper does not show significant changes with the rise in mileage following wheel reprofiling.

FMEA, monitoring, retrofit and redesign of insulated rail joints

Insulated rail joints (IRJ) are a fundamental component of railway signalling that ensure train protection using “track circuits”. A track circuit is a section of line delimited by rail joints electrically insulated, powered at one end with an electric power supply to establish a different voltage that is checked at the other end with a so-called “track circuit relay”. When the section is short-circuited by an axle the relay drops, and the section is defined as “occupied”. IRJ are subjected to continuous and dangerous failures as they represent a singularity in the rail continuity. Continuous battering produces the classical train impact noise while damage in the rail accumulates until the IRJ fails with extremely unpleasant consequences. The paper discusses the main failure modes of an IRJ starting from a historical perspective, showing how an appropriate failure analysis would have prevented a catastrophic accident that recently occurred in Italy. Several countermeasures are shown and a completely new IRJ potentially completely solving the issue is introduced.

Effect of normalizing treatments on microstructure and electrochemical corrosion properties of U75V-welded joints in an acidic environment

Corrosion poses a significant threat to the structural integrity of steel rails, especially in an acidic environment. In this study, we evaluate the corrosion properties of U75V-welded joints using potentiodynamic polarization curves, electrochemical impedance measurements, and corrosion morphology studies under simulated acidic conditions. Compared to non-normalized joints, the normalized joints exhibit a higher self-corrosion current (4.65 × 10−5 A/cm2) and a more negative self-corrosion potential (−0.56919 mV). The smaller and more uniform grain size obtained after normalizing provides multiple active sites on the surface for polarization reactions. Furthermore, owing to significant erosion caused on the rail surface by the acidic solutions, normalizing treatment enhances the passivation effects on the surface, resulting in increased corrosion resistance (221.96 Ω cm2). Our findings provide insights into the impact of normalizing treatments on the corrosion mechanism of U75V rail joints under acidic conditions.

Thermal cycles and microstructure of the flash butt welded joints of 110G13L and K76F steel rails through 08Xh18N10T steel insert

Thermal cycles and microstructure of the flash butt welded joints of 110G13L and K76F steel rails through 08Xh18N10T steel insert

Vibration characteristics of subway turnout area during vehicle deceleration and assessment of the model accuracy

Frog gaps and rail joints produces intricate wheel-rail contact conditions within subway turnouts, which results in intense vibrations. This study describes vibration tests conducted on several typical cross-sections of a turnout, which aimed at understanding the vibration transfer characteristics of typical section in turnout area. To separation the vibration signals from each carriage, wavelet analysis and peak detection algorithms were utilized. Using a 2D kernel density algorithm, representative data from the carriages were clustered, effectively isolating the influence of interference data. A coupled vehicle-turnout-tunnel-soil vibration analysis model was established, combining multiple spatial and temporal scales and the accuracy of its prediction was evaluated by comparing the calculated results to statistical test results.The test results indicate that when the train decelerated through the turnout, there was a significant variation in the vibrations of different train carriages, with a 13 dB difference in the total rail vibration levels. The rail joints and frog gap present in the turnout resulted in high vibration level in the tunnel walls. The main frequency of tunnel wall vibration in the frog gap section was 63 Hz, and the total vibration level was 84.9 dB. The accuracy of vibration response prediction was evaluated by comparing the calculated results to statistical test results using probability density functions, and the model errors were maintained within 10 % of the test data. The presented vibration testing and modelling results of vibration propagation characteristics in various directions for the subway turnout area will provide a foundation for selecting vibration mitigation measures.

Wheel flat detection by using the angular domain synchronous averaging method and axle box acceleration: Simulation and experiment

Wheel flats (WFs) can generate periodic impact forces and aggravate the wheel-rail interaction. Therefore, the early detection of WFs is significant for railway operators to lower the maintenance cost. In this work, the angular domain synchronous averaging (ADSA) method is employed to detect WFs on railway vehicles since it can handle the non-stationary vibration process of rotating machines by processing the vibration data in the angular domain. Furthermore, the short-time irregular impulses, such as those caused by crossings and rail joints, can be attenuated by using synchronous averaging technology. The periodic impact caused by WFs can be easily observed in the polar coordinate using the ADSA method, which is verified by one multibody system (MBS) simulation and one field experiment. Besides, the sensitivity of this method to various flat dimensions and multiple flats is also studied in the MBS simulation.

Influence of different factors on the value of the rail wear rate

The article deals with the study of the influence of train operating modes on the uphill and downhill sections with radii less than 450 m, as well as the influence of railway superstructure design in curved sections on the wear rate of rolling stock wheel flanges and rails. The aim of the research is to reduce the wear that occurs between the wheel flanges of the rolling stock and the rails. Rail joints have been found to be the main shock source in the dynamic interaction between the railway and the rolling stock. There is unstable motion within the transition curves and at the joints of the curved rail on the curved track sections. This is accompanied by abrupt lateral rail wear in the joint area between the trailing and facing rails in the direction of train movement. It has been found that reducing the weight of the trains leads to a reduction in intensive lateral rail wear on curved track sections and can reach the following percentages: in curves with a radius of up to 300 m: up to 33% uphill, up to 55% downhill; in curves with a radius of 300 m to 450 m: up to 32.9% uphill, up to 26.3% downhill; in curves with a radius of 450 m: up to 3.2% uphill, up to 17.6% downhill. On the uphill and downhill sections, reducing the height and adjusting to the speed limit in percentage gives a positive result from 4.7% to 53.59%.

Analysis of reliability of a prefabricated conductive rail joint in context of heavy traffic

In this paper, the calculation of reliability indicators has been carried out in the article for two configurations of a prefabricated conductive rail joint: with fish plates, a welded and bypass connector, and a spring rail bond. The sections of the track where the probability of failure of the prefabricated conductive rail joint is increasing are identified. The destabilizing factors influencing the onset of failure of a prefabricated conductive rail joint earlier than the calculated values of the durability indicators are considered. A model for evaluating the reliability of the second configuration of a prefabricated conductive rail joint based on the Markov analytical model has been developed, and such reliability indicators have been calculated as the probability of its being in working condition, as well as the probability of failure of the prefabricated conductive rail joint due to the inoperability of the fish plates and the spring rail bond. The features of the configuration of a prefabricated conductive rail joint with a spring rail bond are taken into account, which consist in the fact that in order to eliminate the failure due to the inoperability of the spring rail bond, it is necessary to remove the fish plates.

Experimental Study of Static and Dynamic Loading Effects on Guided Wave-Based Intelligent Monitoring of Welded Rail Joints

Experimental Study of Static and Dynamic Loading Effects on Guided Wave-Based Intelligent Monitoring of Welded Rail Joints

Monitoring of Insulated Rail Joints Based on Gap Value Measurement

AbstractThe monitoring of an IRJ would allow targeted maintenance to be carried out, reducing the problems caused by its potential failures. The authors present the results of a test field investigation, that involved the installation of seven longitudinal displacement sensors that continuously record the gap value of insulated rail joints (IRJs). The monitoring of an IRJ would allow targeted maintenance to be carried out, reducing the problems caused by its potential failures. The studied monitoring system was installed in a station of the suburban railway line within the metropolitan city of Bologna (Italy). Analysis of low-and high-frequency recordings was performed. In particular, low-frequency acquisition was used to fit a statistical predictive model that detects a deviation from a standard behaviour and may evidence anomalies. For the high-frequency acquisitions (registered during train passage) some representative quantities, that can provide macroscopic indicators of loss of joint stiffness, were computed. Although gap measurement alone is not exhaustive for identifying all possible failure scenarios, the data acquired by these monitoring devices can represent a possible immediate monitoring solution, based on already available instrumentation, to provide user-friendly predictive analysis systems aiming at improving the railway maintenance.

Production Improvement of Rail Joint by Industrial Engineering Techniques: Case Study of Rail Joint Production

The aim of this research is to improve the rail joint production performance together with appropriate personnel selection process for after-improvement work. The investigation and improvement are done in two levels: process level and activity level. At process level, improvement is done at the bottleneck process using why-why analysis approach along with Eliminate-Combine-Rearrange-Simplify (ECRS) principle. Next, production activity is studied through multiple-activities chart to determine the maximum number of machines which workers can handle. In order to establish staff selection criteria, proper capability for each task is determined by applying Analytical Hierarchy Process to obtain weights for each criterion. The results are reduction of operations processes from 9 stages to 8 stages and personnel reduction from 5 workers to 2 workers. Those two staffs are chosen based on weights for essential tasks, which are 0.340 for machine setting adjustment, 0.367 for product quality test, 0.178 for communication, and 0.115 for read ability to the drawings. Besides that, such improvement can reduce the average percentage of the idle time from 63.56 to 34.65 or a decrease 16.54 percentage but reduce the percentage of machine work rate from 76.16 to 63.56 or a decrease 16.54 percentage.

Effect of different gaps in the conductor rail joints on the current-carrying wear performance of carbon skateboards/conductive rail contact

The interconnection of the conductive rail for intercity trains involves multiple sections of steel rails. The presence of gaps in the joints between these steel rails greatly impacts the efficacy of current transmission in collector–conductor rail systems. A total of nine joints with different inclined angles and widths were devised to investigate the influencing characteristics of gaps on the current–carrying friction of carbon skateboards/conductive rail contact. The nine joints were tested by using a pin-disc current–carrying friction tester to evaluate the wear performance of different contact pairs. The findings indicated that the presence of gaps in conductor rail joints resulted in a decrease in the coefficient of friction, but an increase in the electrical contact resistance. Furthermore, these gaps substantially impacted the wear rate of carbon skateboards. Specifically, when the gap width was 1.5 mm, the influence of the inclined angle of the gaps on the electrical contact resistance diminished. Additionally, the gap characterized by a width of 0.5 mm and an inclined angle of 90° exhibited a comparatively reduced influence on the wear performance of the contact pairs.

<b>Test Method for Loading Tracks Composed of a Single Set of Rail Fastening Systems for Rail Joints</b>

<b>Test Method for Loading Tracks Composed of a Single Set of Rail Fastening Systems for Rail Joints</b>

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.

An Algorithm for Monitoring the Transient Resistance of a Prefabricated Conductive Rail Joint

An Algorithm for Monitoring the Transient Resistance of a Prefabricated Conductive Rail Joint

Stress increases in crane runway girders due to rail joints

AbstractVertically acting wheel loads from overhead bridge cranes and potential additional horizontal crane loads induce two types of stresses in crane runway girders: i) global stresses due to bi‐axial bending and torsion and ii) local stresses which mainly affect the girder's web. The latter typically represent one of the most decisive criteria for the fatigue design check of welded girders and are the focus of this paper. Crane rails with foot flange are typically connected to the top flange with rail clips. These clips maintain the position of the rail in vertical and horizontal transverse direction, but they generally allow for longitudinal movement of the rail. Rails with foot flange are used with and without elastomeric bearing pads between the rail and the top flange of the girder. The local stresses in the webs of crane runway girders are strongly affected by discontinuities of the crane rails. Such discontinuities can originate from unplanned rail cracks as well as planned rail expansion joints. The current mechanical models for concentric as well as eccentric wheel loading in relevant design standards assume continuous crane rails. However, rail joints are expected to significantly increase the local stresses in the region beneath rail joints. The present paper focuses on the impact of rail joints on the local stresses in crane runway girders. The research activities comprise experimental tests as well as finite element calculations. The aim of the investigations is to develop a better understanding of the mechanical behaviour in order to avoid future fatigue damage due to an unexpected increase of local stresses at a rail joint.

Structural condition assessment based strain-stress behaviour for railway welded rail joint using rosette fibre Bragg grating optical sensor

The rail provides a medium for trains to operate along and a support system for the cargo trains to carry. Proper caution should be exercised when handling the thermite welded rail, as it can be vulnerable to damage and failure if not properly maintained. The thermite welded rail joint experiences the greatest amount of train impact and has the least material rigidity. However, measuring the deformation or strain that occurs on a rail is difficult as limitation of the strain gauge itself and challenges to perform the measurement on site due to surroundings. A rectangular rosette Fibre Bragg Grating (FBG) sensor setup was mounted on the web surface of the rail to obtain three distinct strain directions, in order to measure and monitor the direct strain on the thermite welded rail joint. The location for the FBG sensor setup is determined by the presence of visible defects and the production of load sounds when the railway passes through specific locations on the rail track. The FBG sensor's wavelength signal displays three distinct patterns for each strain direction and is used to compare the results between the thermite welded joint and the smooth base rail structure. The wavelength signal exhibits tensional strain, compressional strain and tensional and compressional strain in combination. The principal strain and principal stress are examined between four different locations. The strain value obtained from FBG sensors show instability and variations, which can be attributed to factors such as the dynamic wheel-rail interaction and the condition of the rail structure. Therefore, the FBG sensors are proven to be acceptable in rail track condition assessment based on direct strain measurement for running rail track applications.