Broken Rail Research Articles

고전압임펄스궤도회로(HVITC)와 AF 궤도회로간의 간섭에 대한 연구

Two types of track circuits are used in high speed railway car depots: one is High Voltage Impulse Track Circuit(HVITC); the other is AF track circuit. HVITC detects train occupation of blocks and broken rail; the AF track circuit is used for train onboard control system pretesting before departure. This testing is used to transmit train control information through the AF track circuit. The two systems are switched in turns for testing. We propose a system in which the AF track circuit is replaced by a loop cable that is installed on the inside rail; as such, engineers do not need to switch the systems. In cases in which the two systems run simultaneously, mutual interference may occur. In this paper, we identified this mutual interference by modeling of the two circuits.

The effects of fastening strength on the variation in stress-free temperature in continuous welded rail

Continuous welded rail (CWR) is a fundamental component of any modern track structure and has several advantages over former types of rail joining processes. The reduction in maintenance and related costs has become the most attractive property of CWR although careful monitoring and maintenance of CWR is essential to ensure safe train operations. Management of the stress-free temperature (SFT) of any section of CWR in order to prevent rail breaks and lateral buckling that could lead to derailments is a vital duty of the track maintenance team. Variations in the SFT are influenced by a number of external factors. This paper describes experimental field and laboratory tests carried out to investigate to what extent the fastening strength influences the variation in SFT in CWR track on Fist fastenings and two types of pads. The research established a nonlinear relationship between clamping force and rail movement through the fasteners as well as a strongly linear relationship between clamping force and the variation in SFT. It is also demonstrated that although the friction coefficient of the pad has an influence on rail movement through the fastener, the primary factor influencing SFT variations is the clip force. This paper concludes by quantifying the relationship between clamping force and the expected variation in SFT with clear guidelines on the management of the SFT in CWR.

Statistical Temporal Analysis of Freight Train Derailment Rates in the United States

Safety is the top priority for every rail system in the world. A widely used measure for rail safety is the accident rate, which is the number of train accidents normalized by traffic exposure. Of interest in rail safety research is understanding the temporal trend of accident rates, the significant factors affecting the trend, and how to predict accident rates. This paper uses a negative binomial regression model to present a statistical analysis of U.S. Class I railroad freight train derailment rates on main tracks by year and accident cause for 2000 to 2012. The accident and traffic data used in the analysis come from FRA. The analysis led to several observations. There is a significant temporal decline in freight train derailment rate (-5.9% per year). The rate of change in accident rate varied by accident cause. Rates of freight train derailment caused by broken rails or welds and track geometry defects declined by 6% and 5% annually, respectively; the rate of derailment caused by bearing failure decreased by 11% annually; and rate of derailment caused by train handling errors fell by 7% annually. The regression model is used to project train derailment rates by accident causes and can be used to evaluate the safety benefit of potential accident prevention strategies. This research provides policy makers and practitioners with a statistical method for analyzing the temporal trend of train accident rate for development of rail safety policy and practice.

3F24 ANALYSIS INTO THE STATE OF RAIL CORROSION ACCORDING TO TRACK STRUCTURE IN SUBWAY TUNNELS(Condition Monitoring-Infrastructure)

Tokyo Metro Co., Ltd. has 9 lines; total length of the lines is 195.1kilometer. The total length of tunnels is 166.5km, 85% of all lines. Then, rail corrosion occurs in some part of the tunnel and rail brakes happen due to the corrosion in some cases.For the purpose of prevention of rail break, we investigated fully the rail corrosion on the site for 3 years, from 2011 to 2013, by visual inspection and palpation. The investigation section was selected the places where were recognized the existence of many rail corrosion exist.For identifying section where rail corrosion easily occurs, we made a rail corrosion occurring map. In the map, results of the investigation for rail corrosion and data of the rail exchanges are visualized at 25m intervals. Moreover, we set a score of each rail corrosion and summed up scores in the 25m section. Precisely, a point system of rail corrosion state was made. Using the data, we confirmed influence of difference between inner rail and outer rail, between straight line and curved line, and distance between rail and concrete bed on rail corrosion. For all data, following knowledge were cleared. 1. When distance between rail and concrete bed is large, occurrence of rail corrosion is restrained. 2. Rail corrosion easily occur on rail straight line or inner rail with small distance between rail and concrete bed, and placed near river. We have to exchange rails periodically under the condition.

Optimization of Ultrasonic Rail-Defect Inspection for Improving Railway Transportation Safety and Efficiency

Broken rails are the most frequent cause of freight-train derailments in the United States. Consequently, reducing their occurrence is a high priority for the rail industry and the U.S. Federal Railroad Administration. Current practice is to periodically inspect rails to detect defects using nondestructive technology such as ultrasonic inspection. Determining the optimal rail inspection frequency is critical to efficient use of infrastructure management resources and maximizing the beneficial impact on safety. Minimization of derailment risk, costs of inspection vehicle operation, rail defect repair, and corresponding train delay are all affected by rail inspection frequency. However, no prior research has incorporated all of these factors into a single integrated framework. The objective of this paper is to develop an analytical model to address the trade-offs among various factors related to rail defect inspection frequency, so as to maximize railroad safety and efficiency. The analysis shows that the optimal inspection frequency will vary with traffic density, rail age, inspection technology reliability, and other factors. The optimization model provides a tool that can be used to aid development of better-informed, more effective infrastructure management and accident prevention policies and practices.

Long-term monitoring of steel railway bridge interaction with continuous welded rail

The continuous welded rail (CWR) is nowadays standardly used on almost all modern railway bridges. However, its placement results in an interaction between CWR and the structure, which brings not only longitudinal forces on the substructure, but also significant additional stresses in the rail. These stresses can result either in the rail break, or in a track buckling. Unfortunately, input parameters for performing a numerical analysis are hardly accessible and they vary significantly in different sources. Because of that, an extensive long-time monitoring of the rail–bridge interaction was performed on a bridge with an unusual combination of ballasted track, direct fastening and a barrier in the ballast. The paper presents the results of the monitoring and shows the analysis and evaluation of formulas, defining the fastening nonlinear stiffness of track to the bridge connection. The influence of the temperature on the ballast stiffness is also analysed.

The Application of Laser-EMAT Technique Used to Testing Defect in Rail

Nondestructive test systems are increasingly applied in the industrial context for their strong potentialities in improving and standardizing quality control. Especially in the service stage of rail, early detection of nucleus defects in the rail can avoid the broken rail accident. The aim of present work is to propose a kind of non-contact nondestructive testing method based on the laser and electro-magnetic acoustic transducer techniques, which is suitable to inspect the nucleus defects. This paper describes the testing system, principle and signal processing. The result shows the relative error of testing nucleus defects is about 3.24 %.

Development of a unified railway track stability management tool to enhance track safety

Track buckling is a serious problem for railways. High longitudinal rail stresses contribute to problems such as track buckling, rail joint failure, rail breakage and failure of turnouts. The direct and indirect costs of track buckling problems are very high. The influences of rail temperature, stress-free temperature (SFT) and lateral misalignment of track on track buckling need comprehensive investigation. In this paper, an experimental design comprising strain gauges, thermocouples and rail stress sensors has been implemented on the Queensland Rail heavy haul 60 kg/m rail network. A new creep measurement technique using internal rail stress has been developed. The changes in rail neutral temperature due to the variation of actual rail temperature and the occurrence of rail creep in straight and curved track is quantified. Modes of differences of SFT in the two rails at a location, and of SFT in straight track and in curved track are discussed. The relationship of SFT to rail temperature is also presented. Daily variation in rail temperature due to ambient air temperature is presented. Field trials showed that SFT can vary by 2–3 ℃ during the day. Based on this finding and the derivation of an equation for change of SFT, an improvement in utilising rail creep measurements for assessing track condition has resulted. This finding suggests that it is possible to determine the SFT throughout a day rather than just a single SFT value. This paper also presents a simple track stability management tool that is based on two major parameters, namely rail stress and track resistance. Each parameter in the tool has been given three levels of value to determine the required preventive measures. Overall, the tool decides the need for speed restriction during hot weather based on the quantified parameters from the field trials and rail standards.

실시간 모니터링을 통한 레일절손 검지에 관한 연구

Train accidents can be directly connected to fatal accidents-collision, derailment, Fire, railway crossing accidents-resulting in tremendous human casualties. First of all, the railway derailment is not only related to most of railway accidents but also it can lead to much more catastrophic accompanying train overtured than other factors. Therefore, it is most important factor to ensure railway safety. some foreign countries have applied to the detector machines(e.g., ultrasonic detector car, sleep mode, current detector, optical sensing, optical fiber). Since it was developed in order to prevent train from being derailed. In korea, the existing track method has been used to monitor rail condition using track circuit. However, we found out it impossible for Communication Based Train Control system(CBTC), recent technology to detect rail condition using balise(data transmission devices) without no track circuit. For this reason, it is needed instantly to develop real-time monitoring system used to detect broken rails. Firstly, this paper presents domestic and international statues analysis of rail breaks technology. Secondly, the composition and the characteristics of the real-time monitoring system. Finally, the evidence that this system could assumed the location and type of broken rails was proved by the experiment of prototype and operation line tests. We concluded that this system can detect rail break section in which error span exist within<TEX>${\pm}1m$</TEX>.

Experimental studies on the performance of rail joints with modified wheel/railhead contact

Rail joints are provided with a gap to account for thermal movement and to maintain electrical insulation for the control of signals and/or broken rail detection circuits. The gap in the rail joint is regarded as a source of significant problems for the rail industry since it leads to a very short rail service life compared with other track components due to the various, and difficult to predict, failure modes – thus increasing the risk for train operations. Many attempts to improve the life of rail joints have led to a large number of patents around the world; notable attempts include strengthening through larger-sized joint bars, an increased number of bolts and the use of high yield materials. Unfortunately, no design to date has shown the ability to prolong the life of the rail joints to values close to those for continuously welded rail (CWR). This paper reports the results of a fundamental study that has revealed that the wheel contact at the free edge of the railhead is a major problem since it generates a singularity in the contact pressure and railhead stresses. A design was therefore developed using an optimisation framework that prevents wheel contact at the railhead edge. Finite element modelling of the design has shown that the contact pressure and railhead stress singularities are eliminated, thus increasing the potential to work as effectively as a CWR that does not have a geometric gap. An experimental validation of the finite element results is presented through an innovative non-contact measurement of strains. Some practical issues related to grinding rails to the optimal design are also discussed.

A Bayesian network to evaluate underground rails maintenance strategies in an automation context

Reliability analysis has become an integral part of system design and operation. This is especially true for systems performing critical tasks, such as mass transportation systems. This explains the numerous advances in the field of reliability modeling. More recently, some studies involving the use of Bayesian networks have been proven relevant to represent complex systems and perform reliability studies. In previous works, a generic methodology was introduced for developing a decision support tool to evaluate complex systems maintenance strategies. This article deals with development of such a decision tool dedicated to the maintenance of Paris metro rails. Indeed, owing to fulfillment of high-performance levels of safety and availability (the latter being especially critical at peak hours), operators need to estimate, hour by hour their ability to prevent or to detect broken rails. To address this problem, a decision support tool was developed, the aim of this article is to evaluate, compare and optimize various operating and maintenance strategies.

Service Condition of Railroad Corridors around the Insulated Rail Joints

AbstractRailroad corridors contain a large number of insulated rail joints (IRJs) that act as elements (critical to safety) in the circuitries of signaling and broken rail identification systems. IRJs are regarded as sources of excitation for the passage of loaded wheels that lead to high-impact forces. These forces in turn cause dips, cross levels, and twists to the railroad geometry in close proximity to the sections that contain IRJs, in addition to local damage to the railhead of the IRJs. Therefore, a systematic monitoring of IRJs in railroads is prudent to mitigate the potential risk of their sudden failure (e.g., broken tie plates) as a consequence of rail traffic. This paper presents a simple method of periodic recording of images using time-lapse photography and total station surveying measurements to understand the ongoing deterioration of IRJs and their surroundings. Over a 500-day period, data were collected to examine the trends in narrowing of the joint gap that is attributable to plastic de...

Guided Wave Inspection and Monitoring of Railway Track

Cost-effective NDE of the vast length of aging railway track around the world remains a challenge for the community. Continuously welded rail is installed in tension but temperature changes can result in rail buckling if the initial tension is insufficient or fatigue cracks and ultimately rail breaks if the initial tension is excessive. The NDE challenge therefore includes both the detection of defects and the measurement of axial stress. Since continuously welded railway lines may be thought of as one-dimensional elastic waveguides, they are natural candidates for guided wave ultrasound, which offers the potential to interrogate a large length of rail from a single position. Guided waves have been proposed as a means of detecting the axial stress in rails to prevent buckling and also as a means of detecting complete breakage and cracks prior to breakage. This paper reviews the approaches used and the modeling methods available to support the development of nondestructive inspection and monitoring systems. Possibilities for future systems are also discussed.

Analysis of Causes of Major Train Derailment and Their Effect on Accident Rates

Analysis of the causes of train accidents is critical for rational allocation of resources to reduce accident occurrence in the most cost-effective manner possible. Train derailment data from the FRA rail equipment accident database for the interval 2001 to 2010 were analyzed for each track type, with accounting for frequency of occurrence by cause and number of cars derailed. Statistical analyses were conducted to examine the effects of accident cause, type of track, and derailment speed. The analysis showed that broken rails or welds were the leading derailment cause on main, yard, and siding tracks. By contrast to accident causes on main tracks, bearing failures and broken wheels were not among the top accident causes on yard or siding tracks. Instead, human factor–related causes such as improper use of switches and violation of switching rules were more prevalent. In all speed ranges, broken rails or welds were the leading cause of derailments; however, the relative frequency of the next most common accident types differed substantially for lower-versus higher-speed derailments. In general, at derailment speeds below 10 mph, certain track and human factor causes—such as improper train handling, braking operations, and improper use of switches—dominated. At derailment speeds above 25 mph, those causes were nearly absent and were replaced by equipment causes, such as bearing failure, broken wheel, and axle and journal defects. These results represent the first step in a systematic process of quantitative risk analysis of railroad freight train safety, with an ultimate objective of optimizing safety improvement and more cost-effective risk management.

Safety assessment of underground vehicles passing over highly resilient curved tracks in the presence of a broken rail

Vehicle–track interaction for a new resilient slab track designed to reduce noise and vibration levels was analysed, in order to assess the derailment risk on a curved track when encountering a broken rail. Sensitivity of the rail support spacing of the relative position of the rail breakage between two adjacent rail supports and of running speed were analysed for two different elasticities of the rail fastening system. In none of the cases analysed was observed an appreciable difference between either of the elastic systems. As was expected, the most unfavourable situations were those with greater rail support spacing and those with greater distance from the breakage to the nearest rail support, although in none of the simulations performed did a derailment occur when running over the broken rail. When varying the running speed, the most favourable condition was obtained for an intermediate speed, due to the superposition of two antagonistic effects.

Stable Analysis of CWR Track by its Vibration Characteristics

Stress contained in rails, mainly due to thermally-induced expansion and contraction, results in large longitudinal loads which lead to broken rails and track buckling. According to the beam bending theory of structural dynamics with a consideration of the influence of axial load, a CWR track model is developed in the present study to be used for extensive buckling analysis of CWR tracks. The model discusses CWR track vibration characteristics with a length of unsupported rail subjected to the longitudinal force due to fluctuation of temperature. From the result, it can be gotten that the critical point of the temperature which may cause the rail have the danger of unstable. This model would help to evaluated and measure the real temperature in rail by analyzing the dynamic response of CWR track.

고속철도 레일 표면 결함 관리기준에 관한 연구

레일 표면 결함이 발생할 경우 매우 높은 충격하중이 발생하여 레일 피로 진전 또는 레일 파단에 이를 수 있고 레일이 파단될 경우 열차탈선 등 대형 사고가 발생할 수 있으므로 레일 결함부에 대한 관리기준의 정립이 매우 중요하다. 본 연구에서는 차량-궤도 동적 상호작용 해석 프로그램을 이용하여, 실제 고속철도 자갈궤도에서 결함이 발생한 43개 지점에서 측정된 레일요철을 입력값으로 하여, 요철 깊이에 따른 충격 윤중과 레일 휨응력을 산정하였다. 궤도틀림을 감안하여 윤중 및 레일 휨응력의 한계값을 설정하고, 해석결과로부터 얻은 윤중 및 레일 휨응력 최대값과 결함 깊이 및 폭과의 상관관계를 분석함으로써 레일 표면 결함부에 대한 관리기준을 제시하였다. 분석 결과, 허용할 수 있는 요철 깊이는 충격 윤중에 의하여 발생할 수 있는 레일 두부의 소성 변형을 방지하기 위하여 관리되어야 하며, 엄격한 조건을 평가할 경우 그 값은 0.2mm 정도가 적당함을 알 수 있었다. The rail surface defects can cause the high impact load on the track and lead to the progress of the rail fatigue damage and the rail break. In case of the rail break, there is a great deal of risk for derailment, and thus the maintenance criteria for the rail surface defects are of great importance. In this study, using the dynamic train-track interaction analysis program, the impact wheel loads and rail bending stresses according to the depths of the surface defects have been calculated with the input data of the rail surface irregularities measured at 43 spots with surface defects in the ballasted track of high-speed railway. Considering the irregularity of track geometry, the allowable limits of wheel load and rail bending stress have been set, and the maintenance criteria for the rail surface defects was suggested by analyzing the relationship of the maximum values of wheel load and rail bending stress versus depth and width of rail surface defect. The analysis results suggest that the allowable depth of the surface defect is determined approximately 0.2mm from the limit of the impact wheel load.

Using standard adhesion tests to characterize performance of material system options for insulated rail joints

Insulated joints (IJs) are often required every few kilometres along railway tracks for signal blocks and rail break detection; practical experience has shown that their life is often a fraction of the life of other track elements on some rail lines subjected to high tonnage freight. This article reports findings from a project conducted to study different bond systems consisting of various combinations of adhesives, fibrous insulators, and rail surface treatments that were of potential interest for increasing the service life of IJs for rail applications. The study was performed in parallel with a finite-element analysis and did not focus on testing real IJs but rather on common adhesion test specimens such as the single lap joint and double cantilever beam configurations. The aim of using these specimens was to simulate potential load and environmental conditions on standard test specimens that were less expensive and easier to construct, test, and analyse. The main goal of the project was to compare a number of combinations of potential IJ components through an extensive test programme. The results highlighted several possible combinations that may warrant further study as actual IJ prototypes. In particular, several material combinations involving materials not currently used by IJ vendors had higher overall performances when compared to currently used combinations, although the extension of improved test specimen performance to actual IJ configurations and service conditions may not follow.

Influences of Rail Expansion Joint on Jointless Turnout on Ballasted Continuous Beam Bridge

Based on turnout/bridge interaction principle and finite element method (FEM), an integrated turnout/beam/pier model of jointless turnout on ballasted track was established to analyze the influences of expansion joint on stress and deformation of the turnout. The results are concluded as follows: whether the rail expansion joint is set in front of or behind the turnout, expansion additional force of stock rail will be reduced greatly at the end of the beam; so do the expansion displacement of switch rail and nose rail, the stress of displacement restrictor and spacer block, rail break gap and the longitudinal force of one rail after the other rail broke. But when the expansion joint is set in front of the turnout, the pier’s longitudinal force of continuous beam bridge and the simply supported beam bridge (within the expansion range of the device) increase greatly. When the device is close to the turnout, longitudinal relative displacement of the stock rail to the girder also increases a lot. By comparison, it is more favorable to set the expansion joint behind the turnout, or to set the device at the both ends of the continuous beam, or to set the device at the ends of continuous beam rather than in the center of the span.

On-site investigation and analysis of flaking damage leading to rail break

▶ Occurrence of the flaking damage and its relationship with the wear of rail under oil lubrication operation was investigated. ▶ The occurrence rate of the flaking damage was high at gauge corner side of high rail in moderate curves. ▶ The balance between the wear and the accumulation of micro-strain or fatigue was a key to occur the flaking damage. In order to know the relationship between the occurrence of flaking leading to the rail breakage and wear of the rail, on-site investigations and analysis of the broken rail were carried out. As a result, it was found out that the occurrence rate of the flaking damage was high at gauge corner side of high rail in moderate curves with radius from 800 m to 1800 m. It was also found that the rail wear in the section where lubrication was applied was about a half of that in the section without lubrication. Moreover, it was found that flaking damage was generated on the running surface or in the close vicinity of the surface of rail head under the condition of repeated loading of shear and tangential forces caused by the rolling contact with wheels. It could be assumed that the balance between the wear and the accumulation of micro-strain or fatigue was a key to occur the flaking damage.