Insulated Rail Joints Research Articles

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.

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.

Design, wheel-rail interaction and testing of an innovative reinforced smooth transition insulated rail joint

Insulated Railway Joints (IRJ) fail mainly because of repeated shocks in the end post region, characterized by a largely reduced stiffness, causing loss of insulation (lipping), star cracks in the fishbolt holes and eventually broken rails leading to possible derailments. Laboratory tests to qualify IRJs are inadequate as they do not replicate impact loads. An innovative, reinforced joint named ABJ, made of forged shallow depth switch rails with a long, inclined cut and a thick reinforcing steel baseplate is introduced in the paper. It doesn’t show a dip angle in the transition area, resulting in smooth wheel-rail transition forces preventing rail damage, impact noise, vibrations and ballast deterioration. It is designed to be laid on standard sleepers and it can be installed on standard track. An innovative cable routing allows plain and continuous tamping operations optimizing track behaviour and degradation in the long term. Impact noise typical of rail joints is eliminated and the estimated life is theoretically infinite. The paper describes the static and dynamic behaviour of the ABJ as well as the wheel-rail interaction obtained by numerical simulations and a partial full-scale validation of the new joint.

Evaluation of railhead material damage of insulated rail joints due to cyclic wheel loadings

Although insulated rail joints (IRJs) are important railway track components and, because of their low bending rigidity, a dynamic wheel impact results as wheels pass over them. Proper attention is needed to address this problem. Focussing on this point, a 3D finite element analysis (FEA) is carried out on IRJs to evaluate on damage analysis of sub-surface railhead material for endpost materials: fiberglass (fb), nylon 66 (ny), and polytetrafluoroethylene (ptfe). A cyclic vertical wheel load up to a total of 2000 cycles in non-Hertzian pressure form is applied at the wheel/rail contact patch on an IRJ. The residual longitudinal stress damage parameter is considered to rank the endpost material based on sub-surface railhead damage. It exhibits a new pattern described as ‘vertical flat type’ for a depth up to 8 mm initially and, as the cyclic loading increases, the vertical flat pattern damage changes to an ‘inclined flat type’ pattern.

Research and Analysis on Contact Resistance of Wheel and Insulated Rail Joint in High-Speed Railway Stations

Insulated rail joint (IRJ) as one of the components of the track circuit will be burned once the electric arc is generated when the train wheel passes through the insulated rail joint and the track circuit occurs the red-light band fault, which has a great impact on the safety of the train. Reducing the voltage at both ends of the insulated rail joint can effectively prevent the occurrence of electric arc. Clarifying the wheel-IRJ contact resistance is the basis for analyzing the voltage of wheel-IRJ. The effective apparent contact area of the wheel-IRJ contact was derived through the mathematical relation. Considering the surface roughness parameters, based on the electrical contact theory and the Greenwood-Williamson (GW) model, the mathematical models of the wheel-IRJ contact resistance and current density were established, and their influencing factors were analyzed. The results show that the contact resistance increased first and then decreased. The influences of load, roughness of the contact interface, and electric arc heat on the contact resistance were greater. Considering the influencing factors of contact resistance and current density, corresponding protective measures were proposed to reduce the potential difference at both ends of the insulated rail joint.

Insulated rail joint (IRJ) contact characterisation-an ultrasonic reflectometry approach for a cross-material interface

Vehicle–track interaction at insulated rail joints (IRJs) plays a significant role in the wear evolvement and damage of the IRJ components. It is, however, challenging to characterise the contact conditions within the region non-destructively and accurately using experimental tools, especially when the IRJ contact involves both wheel–rail and wheel–endpost contact pairs. This study presents an ultrasonic technique to monitor and characterise static IRJ contacts in a non-invasive manner. The proposed ultrasonic reflectometry technique can realise high-resolution visualisation of contact patch and contact pressure distribution for both wheel–rail contact and wheel–endpost contact, by striking a beam of focused ultrasonic signals at the contact interface. Different data post-processing strategies are applied for the two types of contacts and a deconvolution algorithm is applied to rectify the measurements near the rail–endpost boundary. The ultrasonic measurements are verified through finite element simulations and the results show good agreement with each other in terms of both contact area and contact pressure level. It is expected that the proposed ultrasonic approach can be a reliable tool to assist in revealing the contact behaviour of IRJs more profoundly.

Bonded insulated rail joint monitoring using gap opening variation with fibre optic sensors: analytical validation and limits

The monitoring of bonded insulated joints makes it possible to overcome the limits dictated by cyclical scheduled maintenance, helping the infrastructure manager to anticipate the formation of possible failures. A field monitoring system that measures the joint gap opening variation was investigated, using optical fibres with Bragg gratings placed at the head of the two adjacent jointed rails. Through the application of the Zimmermann analytical model, a first quantitative validation of the data recorded by the monitoring systems measuring the joint gap opening variation was proposed. Based on the different types of failure of a bonded insulated joint, the debonded of insulating element of the joint was identified as a typical condition. Starting from this through a finite element analysis, some characteristic limitations of these monitoring systems were identified by assuming four different bonding scenarios.

Numerical investigation of the transient wheel-rail impact behaviour in high-speed turnouts caused by a bonded insulated rail joint

Bonded insulated rail joints (Bonded IRJ) are essential to insulate rails and ensure normal operation of track-circuit signalling. Therefore, bonded IRJs cannot be replaced by the continuously welded joints and are widely existing in high-speed turnouts, by which the wheel-joint impact has been severely threatening the ride safety and comfort. Few researchers are concerned about how the damaged bonded IRJ deteriorates the wheel-rail contact behaviour in high-speed turnouts. To this end, this paper proposed a transient wheel-rail impact model based on the actual irregularities. Results show two different wheel-rail impact modes. The concave shape of the irregularities will induce the discrepancy of impact position when the running speed varies, thus the increase in speed causes the peak wheel-rail force to decrease in downward impact mode as opposed to upward impact. Besides, wheel-joint impact induces greater contact stress and area of contact patches in the vicinity of the end-post, contributing to wider light bands which are consistent with the on-situ conditions. Therefore, the proposed wheel-bonded IRJ impact model can provide guidance in the research of RCF and wear on bonded IRJ, explore the forming reason of the depression and provide a valuable reference for maintenance or damage detection of bonded IRJ.

Evaluating Short-Wave Effects in Railway Track Using the Rail Surface Signal

Condition assessment and maintenance planning of railway infrastructure is a prerequisite for safe and reliable train operation. As the loads are constantly increasing, condition assessment of the track must also be further developed. Existing methods can describe the condition of the track well in many cases, but they will reach their limits with faster deterioration processes and shorter time windows for inspection and maintenance, both associated with higher loads. This development can only be countered with an increased understanding of the system and the associated better planning of component specific measures. Among others, short-wave effects of the track need to be considered. The aim of this paper is to demonstrate the possibility of describing short-wave effects with an already existing data source. Insulated rail joints, welding joints, switch components, but also rail corrugation of different wavelengths and squat can be detected, evaluated and monitored by a measuring system based on optical distance meters. These assets and wear phenomena form essential parts of track asset management, but still are not described sufficiently by established methods. Although the so-called rail surface measurement system has been installed on the main Austrian measuring car for years, its full potential could not be exploited due to insufficient positioning accuracy. The method presented in this paper intends to change that. This allows for a holistic assessment of track condition when planning maintenance activities.

Critical analysis of RCF rail defects classification

The paper presents a brief review of the rail defect coding systems, which were recommended by the International Union of Railways during the period from 1959 to today. The recommended classification and numbering of RCF rail defects, defined in the document IRS 70712 from 2018, were critically analysed. In addition, harmonisation of European standards and IRS 70712 was found necessary by the authors. The paper points out that appropriate attention was paid neither to the combination of several types of RCF rail defects nor to the occurrence of these defects in the sensitive track zones such as switches, crossings, expansion joints, and insulated rail joints. Authors propose that Infrastructure Managers should supplement the Handbook of rail defects with RCF defects that occur on the railway network under their control. Moreover, the authors present the experience regarding RCF defects on the Serbian railway network.

INVESTIGATION OF THE GLUED INSULATED RAIL JOINTS APPLIED TO CWR TRACKS

This article summarizes the research results related to our own conducted extensive laboratory tests of polymer composite and steel fishplated glued insulated rail joints (GIRJs), namely axial tensile tests as well as vertical static and dynamic tests. The investigation dealt with the examination of GIRJs assembled with steel and special glass-fiber reinforced plastic (polymer composite) fishplates, both of them for CWR railway tracks (i.e. so-called gapless tracks or, in other words, railway tracks with continuously welded rails). The exact rail joint types were MTH-P and MTH-AP, consistently. The MTH P types have been commonly applied for many years in the CWR tracks in Europe, mainly in Hungary. The MTH-AP rail joints consist of fishplates that are produced by the APATECH factory (Russia). They are made of a fiberglass-amplified polymer composite material at high pressure and controlled temperature. This solution can eliminate electrical fishplate lock and early fatigue failures just as it can ensure adequate electrical insulation. The advantage of such rail joints can be that they are probably able to ensure the substitution of the glued insulated rail joints with relatively expensive steel fishplates currently applied by railway companies, e.g. Hungarian State Railways (MÁV). The aim of the mentioned research summarized in this paper is to formulate recommendations on technical applicability and on the technological instructions that are useful in everyday railway operation practice on the basis of the measurements and tests carried out on rail joints in laboratory.

FEA of mechanical behaviour of insulated rail joints due to vertical cyclic wheel loadings

Insulated rail joints (IRJs), safety critical components of railway track, are used to locate trains and broken rails using electrical signalling systems. The bending rigidity of the rail at an IRJ is only 2/3rds that of continuous rail. As a result, stress singularity problems occur at IRJs which therefore degrade faster compared to the continuous rail. Both railhead top surface and sub-surface damage occurs and accelerates the initiation of cracks. Head hardened rails are used to overcome these problems.A thorough study addresses the damage pattern in the railhead sub-surface using a 3D finite element analysis (FEA) employing vertical wheel loadings considering three endpost materials: fibre glass (fb), nylon 66 (ny) and polytetrafluoroethylene (ptfe). A new damage parameter, the vertical residual stress component, is proposed to assess new patterns of railhead damage considering plastic deformation. To rank the influential stress related damage parameters, two other parameters are also considered, namely residual von-Mises and longitudinal stress components. Of these, the residual von-Mises stress component is more prominent with regard to the top surface and sub-surface damage, whereas the longitudinal stress component is responsible for top surface material damage. From these damage patterns, a progressive change in the hardness distribution of railhead material can evolve.

Wheel-rail impact at an insulated rail joint in an embedded rail system

With dynamic behaviour different from that of traditional discretely supported tracks, continuously supported embedded rail systems (ERSs) have been increasingly used in railway bridges, level crossings, trams, and high-speed lines. However, studies on ERSs have been limited, and none of them have addressed the wheel-rail impact-induced dynamic response, although wheel-rail impact is a main cause of ERS degradation. This paper studies, numerically and experimentally, the wheel-rail impact at an insulated rail joint (IRJ) used in the ERS. As a weak spot of the track, the IRJ results in discontinuities in the track support stiffness and wheel-rail contact geometry. This study first develops an explicit finite element model to simulate the vibration responses of the IRJ in the ERS when excited by a hammer and passing wheel loads. The simulated dynamic behaviours (represented by the hammer-excitation frequency response function) at a frequency up to 5 kHz and a wheel-rail impact vibration frequency up to 10 kHz are then validated with a field hammer test and a train pass-by measurement, respectively. Both the experimental study and numerical modelling reveals that the major frequencies of the impact vibration at the IRJ in the ERS depend mainly on geometric irregularities in the IRJ region and the train speed, rather than on the resonances of the track structure, as in the case of the discretely supported IRJ. This finding is meaningful to the engineering practice because it indicates a continuously supported IRJ in the ERS is more impact resistant, especially when the IRJ geometry is adequately maintained, e.g. by timely grinding.

Field test and numerical analysis of Insulated rail joints in heavy-haul railway

Insulated rail joints (IRJs) are widely used in heavy-haul lines, owing to they are safety critical components of track circuit. However, the IRJs breaks the continuity of the rail, making rail more vulnerable to damage under the long-term wheel-rail interaction. In order to study the performance of IRJs, field investigation and tests were carried out at new IRJ and damaged IRJ. At the same time, a 3D coupling model of heavy haul train-IRJ was established for the further analysis. The result shows that in regards to rail-surface regularity, the new IRJ and the damaged IRJ exhibits convex joint and concave joint respectively. IRJs will gradually turn to concave and dipped in the vicinity of end-post under long-term wheel-rail impact. Since there is a vertical rail displacement difference on both sides of the end-post between the two IRJs, causing the wheel-rail interaction has two different impact modes, of which one is downward height difference impact and the other is upward height difference impact. In normal speed, the impact caused by the damaged IRJ is larger than the new IRJ does and it leads to a severer damage to the whole track. The displacement of sleeper at the damaged IRJ is 7.6 times larger than at the new IRJ due to the void between the sleeper and the ballast. The transfer function of displacement from rail to sleeper at the new IRJ is between 0 and 0.4, while the damaged IRJ is between 0.42 and 6.1. The transfer function can be used as a vital index to evaluate the IRJ service state. With the increase of speed, the displacement of rail and sleeper at the two IRJs increases correspondingly. For the sake of decreasing the occurrence of fatigue damage and plastic deformation of rail and plate as much as possible, the maximum depth of concave should be reined within 0.55 mm.

Finite Element Analysis of a Fishplate Rail Joint in Extreme Environment Condition

Railways are very efficient mode of transportation. Speed limits of the railways and loads they carry are increasing rapidly. Due to some advantages, the insulated rail joints are still the part of a rail-track system. However, a high rate of failure of joints puts the railway track at risk. Therefore, a detailed study of these joints is required. In this paper, a three-dimensional finite element model of rail-fishplate joint is created using Abaqus - a finite element method-based software. Stresses in fishplate and bolts due to wheel impact are analysed by coupling implicit and explicit methods. It is found that bolts are a critical part of a joint due to stresses and vibrations to which they are subjected. The large number of stresses and vibration can result into loosening of bolts.

Quantification of sub-surface railhead material damage due to composite endpost materials of insulated rail joints for cyclic wheel loadings

This study focusses on a 3D finite element analysis to investigate damage of sub-surface railhead material at insulated rail joints (IRJs) considering different composite endpost materials (fibreglass, nylon 66 and polytetrafluoroethylene). At the wheel/rail contact patch on IRJs, vertical wheel impacts up to a total of 2000 cycles are applied. Damage parameters exhibit a vertical flat type damage pattern for a depth up to 8 mm initially and, as the cyclic loading increases, the flat damage pattern changes to a horizontal bell-shape pattern. The results indicate that fibreglass is a better endpost material to control sub-surface railhead material damage.

FEM Modelling Possibilities of Glued Insulated Rail Joints for CWR Tracks

In this paper the authors detail the possibilities of modelling of finite element method (FEM) of glued insulated rail joints which are applied in railway tracks with continuously welded rails (CWR). A lot of laboratory tests (static and dynamic 3-point bending tests, axial pulling tests) were executed on glued insulated rail joints, the specimens were related to three different rail profiles applied in Hungary: MÁV 48.5; 54E1 (UIC54), 60E1 (UIC60), respectively. The static bending tests with many bay length values were conducted, before and after dynamic (fatigue) tests. 2-D beam models were made in FEM software using semi-rigid hinge as the simplified connection of fishplated glued insulated rail joint. The FEM models were calibrated and then validated with the static vertical displacement values in the middle-bay position measured in laboratory. The model validation was conducted with two methods.

SUPPLEMENTARY LABORATORY INVESTIGATIONS OF MODERN PLASTIC-POLYMER FISHPLATES FOR RAIL JOINTS

Purpose. The authors’ goal is to determine the behavior of insulated rail joints with polymer-composite fishplates without glueing in the consideration of dynamic loadings regarding to own laboratory tests. In this paper they introduce the applied measurement opportunities. Methodology. Dynamic (fatigue) bending tests were performed by insulated rail joints assembled with plastic-polymer fishplates. The special laboratory measurements are related to digital picture/video measurement technique and assessment method executed by GOM hardware and software, as well as computer tomography according to laboratory bending tests. Findings. In previous papers the authors published the results of glued-insulated rail joints, in this period they continued their research with the investigation of rail joints with plastic-polymer fishplates without glueing. They tested two different types of rail fishplates made of plastic-polymer material. For the rail joints with fishplates but without glueing, the authors applied special measurement techniques by GOM products (Tritop, Aramis) that enable high precision digital measurement techniques with spectacular visualization results. The computer tomography records ensure the opportunity to be able to receive information about inner crackings and faults of plastic-polymer fishplates, with also high precision measurements. The assessment method has to be developed for these specific measurement methodologies to be able to compare the results and define scientific statements. Originality. Up to now any researcher and research group have been dealing with insulated rail joints with special plastic-polymer fishplates without glueing applied mentioned special techniques, no one determined the exact deterioration process of these joints, as well as the crack growing phenomenon in the cross section of the fishplates. Practical value. The research team of the authors had the possibility to see into the details of glass-fibre reinforced resin bonded plastic fishplates during laboratory tests, as well as they publish timely information in the consideration of their laboratory tests’ results. This result can be applied in railway engineering at all stages: design, construction, maintenance&operation in the future.

On the railhead material damage of insulated rail joints: Is it by ratchetting or alternating plasticity?

Railhead becomes severely stressed due to localised contact loadings. This is more critical in the vicinity of endposts of an insulated rail joint. Popular IRJ endpost materials are fibreglass (fb), polytetrafluoroethylene (ptfe) and nylon66 (ny). A 3D finite element analysis is carried out to study stress distributions in railhead material near the endposts. The progressive damage parameter, von Mises stress and other residual stress and strain plots indicate that plastic deformation and material degradation occur at sub-surface levels of the railhead material. Although fb and ptfe are better endpost materials than ny, ny displays superior performance over the other two.

LABORATORY TEST RESULTS OF GLUED INSULATED RAIL JOINTS ASSEMBLED WITH TRADITIONAL STEEL AND FIBRE-GLASS REINFORCED RESIN-BONDED FISHPLATES

Purpose. The authors’ aim is to evaluate more precisely the deterioration process of glued insulated rail joints with polimer-composite and steel fishplates regarding to own laboratory tests. Methodology. The laboratory tests were executed by three-point static and three-point dynamic (fatigue) bending tests’ measurement results related to glued insulated rail joints with fibre-glass reinforced polymer-composite fishplates (brand: APATECH). During the research the static three-point bending tests were performed on rail joints assembled with three different rail profiles (MÁV48, 54E1 (UIC54) and 60E1 (UIC60)) with three specimens, measured on 13 different support bay values before fatigue test, as well as after 3.5 million loading cycles (the degradations process was checked after every 0.5 million cycles) on polymer-composite and steel fishplated rail joints. Findings. The investigation of fiber-glass reinforced and steel fishplated rail joints (three-point static and dynamic bending laboratory tests) are in progress. Considering to them, the mechanical deterioration processes were able to be determined by measurements of deflection values compared to original ones (i.e. before fatigue tests). The differences can be pointed out by analysis of measurement results related to both types of glued insulated rail joints (steel and polymer-composite fishplated ones). Originality. The goal of this research is to investigate the application of this new type of glued insulated rail joint and to determine the ultimate lifetime of the investigated rail joints, e.g. how much time they can be safely held in the railway track without damage. In the international literature no one has investigated this field of glued insulated rail joints. Practical value. The fibre glass reinforced resin-bonded fishplated glued insulated rail joints and ‘control’ steel fishplated glued insulated rail joints were built into railway line (between Kelenföld and Hegyeshalom state border) in Hungary at three different locations. In this article the investigation of deterioration process of glued-insulated rail joints and steel fishplated glued insulated rail joints are demonstrated only by laboratory bending tests.