Broken Rail Research Articles

Recognition of track defects through measured acceleration - part 2

For an optimized maintenance strategy, the early detection of track defects is necessary. Mounted sensors (e.g. acceleration sensors) on in-service trains are very suitable for track monitoring. With the continuous measurement of axle-box acceleration, short wavelength defects can be identified. For example, these defects can be rail breaks or cracks (i.e. rail defects), or local instabilities. Local instabilities can reduce the track quality in a short period of time. For an efficient data analysis of the acceleration signal and classification of different track defects, the development of appropriate methods is necessary. Therefore, a track-vehicle scale model was built to generate acceleration data for typical types of failures. With the generated dataset, developed algorithms for pattern recognition can be easily tested. In the second part of this research, three models created by the supervised learning method are trained and tested for the detection of the local instability in the vertical acceleration signal. The model A is trained with 78 laps and uses a manual classification. The chosen classifier for the model is a bagged tree algorithm implemented in the software MATLAB. The developed models distinguished between no failure, rail defect and local instability. For the training process of the model, the measured acceleration is treated statistically (e.g. Root-mean-square, Standard deviation, Spectral peaks and power). Subsequently test data for different scenarios is generated and used in the prediction model. With this model the track defects in the track-vehicle scale model are detected and classified very reliably. In contrast to existing methods, a machine learning approach is used for the non-destructive detection of the local instability. The results of the model are also improved by the model B and C by using 139 laps as training data, an automatic classification and an optimization of the statistics. The knowledge gained, can be used for acceleration data from in­service trains in regular operation, by adapting the developed model.

Investigating the Effect of Some Train and Track Parameters on Contact-impact Forces in the Vicinity of a Rail Breakage

Broken rails or welds are the main causes of derailment in railway networks. Therefore, a wheel-rail interaction model, which precisely estimates contact-impact forces in the presence of broken rails, can have a significant effect on derailment risk reduction. This paper attempts to present contact-impact forces in the vicinity of broken rails by employing a detailed 3D finite element model. The model is verified using a field test carried out on a ballasted railway track. Effects of train speed, gap length, axle load and railpad and ballast characteristics are studied on rail-wheel contact forces as well as on railpad and ballast forces. Results suggest that increasing the train speed from 60 km/h to 110 km/h would increase dynamic impact force from 2.46 to 4.11. It is also observed that increasing axle load results in an increase in the wheel-rail impact forces and in railpad and ballast forces, while leading to a reduced dynamic impact factor. Furthermore, investigating the effect of the track parameters demonstrates that ballast stiffness is the most important characteristic of the track, which has a reverse effect on dynamic impact forces. Moreover, unloading length increase and consequently derailment risk increase is highly sensitive to increasing train speed.

Quantitative causal analysis of mainline passenger train accidents in the United States

The need for shared freight and passenger rail corridors in the United States is increasing due to the growing demand for regional and intercity passenger transport. Several researches have been conducted on reducing the risk of freight train accidents, but little research has been done on the risk of passenger train accidents. The accident rates of passenger trains have declined in the past two decades; however, faster and more frequent passenger train services require even higher safety standards, and therefore further reduction to the risk of passenger train accidents is needed. The research presented in this paper analyzed the passenger train accidents in the United States using the Federal Railroad Administration train accident database to understand the trend of passenger train accident rates, the frequency and severity of different types of accidents, and to explore the major factors that cause them. Derailments and collisions were identified as the most significant types of passenger train accidents, and track failures and human factors, respectively, were the primary causes of those accidents. Accidents caused due to human factors and train operations such as train speed violations and failure to obey signals are often high-consequence accidents and therefore pose the greatest risk. Higher risk infrastructure-related factors include track geometry defects and broken rails or welds. This study on passenger train accidents provides a solid foundation for further research on improving the safety of passenger rail and shared-use rail corridors.

Crack formation within a Hadfield manganese steel crossing nose

Switches and crossings in rail networks suffer from complex loading which may induce severe damage and defects, including formation of cracks that can result in rail breakage. This paper focuses on the microstructure and crack network in a damaged Hadfield manganese steel crossing nose. The extent of deformation has been quantified by hardness measurements, optical microscopy and scanning electron microscopy (SEM) including electron back scattering diffraction (EBSD). It is found that the wheel contact causes high deformation hardness of over 600 HV, around three times that of the base material, and the strain hardening extends up to a depth of about 10 mm from the running surface. Microscopy indicates the deformation microstructure is composed of bands of both deformation twins and deformation induced dislocation boundaries. The complex crack network within the nose of the crossing has been investigated using 3D X-ray tomography, where both surface and subsurface cracks are detected with the majority of the cracks originating from the surface. The crack network has been related to the observed deformation microstructure and it has been found that although the hardening and the deformation of the Hadfield manganese steel is quite different from that of commonly used pearlitic rail steels, the crack morphologies are found to be quite similar for the two materials.

State-of-the-art review of bridges under rail transit loading

A state-of-the-art review on the global behaviour of bridges under rail transit loading is presented. Of interest is a synthesis of recent technical findings that can bridge the gap between research and practice. The literature review revealed that structural responses have been evaluated and finite-element and analytical models developed. Identification techniques appear to be useful to extract the dynamic characteristics of rail bridges. Impact increases static load in conjunction with dynamic amplification; however, it tends to converge with train speed. The impact force of a wheel–track system is affected by train weight and speed, rail irregularities and rail type. A number of parameters are associated with rail break. The occurrence of rail breaks increases dynamic load allowance and could cause train derailment. Longitudinal forces induced by thermal loading are another important factor in understanding rail–structure interaction. Contrary to highway bridges, limited effort has been made for railway bridges in terms of reliability investigations and the calibration of load and resistance factors. Scarce information is available on bridge responses associated with light rail trains. Several transit agencies have developed design guidelines using their own live load models. A standard live load model for light rail transit is required to achieve uniform design outcomes.

Prediction of RCF clustered cracks dimensions using an ACFM sensor and influence of crack length and vertical angle

ABSTRACTRolling contact fatigue (RCF) cracks are the predominant reason for rail grinding maintenance and replacement on all types of railway system, as they can potentially cause rail break if not removed. To avoid excessive material removal, accurate crack sizing is required. Alternating current field measurement has been used as an electromagnetic method for RCF crack sizing, incorporating with modelling results for single RCF cracks with large vertical angles (>30°). No study using this knowledge to size shallow angled crack clusters has yet been reported. A novel method, the pocket length compensation method, is proposed to determine the length and depth of RCF cracks with shallow vertical angles. For shallow crack clusters, vertical angle predictions are close to the measured values with a deviation of less than 13.6%. Errors in crack pocket length prediction are greatly reduced when the pocket length compensation was included. The predicted vertical depth using the approach developed for clustered angled cracks is accurate with errors <8.3%, which compares to errors of up to 60% if the single RCF crack approach is used and errors of up to 21.4% if a non-compensated prediction for crack clusters is used.

FATIGUE LIFE ANALYSIS OF RAIL-WELDS USING LINEAR ELASTIC FRACTURE MECHANICS

The initiation and growth of fatigue cracking is mainly due to high stress concentration, heterogeneity and poor quality of weld. The detection and rectification of such weld defects are major concerns of rail network managers to reduce potential risk of rail breaks and derailments. To estimate the fatigue life of welded joints and to analyze the progress of fatigue cracks, a fracture mechanics-based analysis and fatigue models were developed using Finite Element Analysis. The initial flaw is obtained from a sample weld using ultrasonic flaw detecting machine test. Linear Elastic Fracture Mechanics (LEFM) approach based on the Paris law was applied to determine critical crack size and the number of cycles to failure using FRANC3D software. The inspection interval of rail welds before fracture (failure) was suggested based on reliability and life cycle analysis that correspond with minimum overall cost and frequency interval. It is recommended that fracture-based models in combination with reliability analyses can be a sustainable infrastructure decision-making algorithm.

Peridynamic Analysis of Rail Squats

Rail surface defects are a serious concern for railway infrastructure managers all around the world. They lead to poor ride quality due to excess vibration and noise; in rare cases, they can result in a broken rail and a train derailment. Defects are typically classified as ‘rail studs’ when they initiate from the white etching layer, and ‘rail squats’ when they initiate from rolling contact fatigue. This paper presents a novel investigation into rail squat initiation and growth simulations using peridynamic theory. To the best of the authors’ knowledge, no other comprehensive study of rail squats has been carried out using this approach. Peridynamics are well-suited for fracture problems, because, contrary to continuum mechanics, they do not use partial-differential equations. Instead, peridynamics use integral equations that are defined even when discontinuities (cracks, etc.) are present in the displacement field. In this study, a novel application of peridynamics to rail squats is verified against a finite element solution, and the obtained simulation results are compared with in situ rail squat measurements. Some new insights can be drawn from the results. The outcome exhibits that the simulated cracks initiate and grow unsymmetrically, as expected and reported in the field. Based on this new insight, it is apparent that peridynamic modelling is well-applicable to fatigue crack modeling in rails. Surprisingly, limitations to the peridynamic analysis code have also been discovered. Future work requires finding an adequate solution to the matter-interpenetration problem.

Comparison of Linear and Nonlinear Behavior of Track Elements in Contact-Impact Models

Existence of short wave length irregularities and discontinuities in the rail, such as corrugation, isolated rail joints, crossings and rail breakage, result in impact forces and an increase in wheel-rail contact force. Extreme forces in such could result in non-linear behavior of ballast and pads, and as a result, employing common linear models mihgt over/under estimate contact forces. A 3D model of wheel and rail is developed in this paper, and by considering rail breakage, validity of linear models and considering non-linear behavior of materials are studied. Wheel-rail interactions are studied for two common pads with high stiffness (HDPE) and low stiffness (Studded) for speeds of 20 to 160 km/h. Three behavioral patterns are considered for the developed 3D model: linear pad and ballast (LP-LB), nonlinear pad and linear ballast (NLP, LB), and nonlinear pad and ballast (NLP, NLB), and results are compared. According to the results, for HDPE pads and impact forces of up to 30 tons, linear model for material could estimate acceptable results. Yet for studded pads, linear model estimates forces that are comparably less than those estimated by non-linear model. Moreover employing NLP-LB model overestimates pad and wheel-rail contact forces by a rather small margin, compared to those estimated by NLP-NLB model, and hence, could be a suitable replacement for it. It is also observed that in order to have a reliable estimate of ballast forces, using non-linear ballast models are mandatory, and neither LP-LB nor NLP-LB could be acceptable replacements.

On the task of allocating investment to facilities preventing unauthorized movement of road vehicles across level crossings for various statistical criteria

Aim. Railway transportation is affected by a whole range of transportation incidents, both related to rolling stock, i. e. vehicle-to-vehicle collisions, derailments, broken cast parts of bogies, etc. , and infrastructure, i. e. broken rail, fires at railway stations and terminals, broken catenary, etc. Among the above incidents, collisions at level crossings are the most likely to cause a public response, as collisions between trains and road vehicles often cause multiple deaths that are reported in national media, which entails significant reputational damage for JSC RZD. Additionally, collisions often cause derailment of vehicles, which may cause deaths and major environmental disasters, if dangerous chemical products are transported. Beside the reputational damage, collisions at level crossings cause significant expenditure related to the repair of damaged infrastructure and rolling stock, as well as damage caused by trains idling due to maintenance machines operation at the location of incident. That brings up the issue of optimal allocation of investment to facilities preventing unauthorized movement of road vehicles across level crossings (hereinafter referred to as protection systems). This problem is of relevance, as replacing level crossings with tunnels and viaducts is not going fast and does not imply the eventual elimination of all level crossing. Hence is the requirement for rational allocation of funds to the installation of protection systems over the extensive railway network. Given the above, the aim of this paper is to develop decision-making guidelines for the reduction of the number of transportation incidents in terms of statistical criteria, i. e. quantile and probabilistic. Methods . The paper uses methods of deterministic equivalent, of equivalent transformations, of the probability theory, of optimization . Results. The problem of maximizing the probability of no incidents is reduced to integer linear programming. For the problem of minimizing the maximum number of incidents guaranteed at the given level of dependability, a suboptimal solution of the initial problem of quantile optimization is suggested that is obtained by solving the integer linear programming problem through the replacement of binomially distributed random values with Poisson values. Conclusions. The examined models not only allow developing an optimal strategy with guaranteed characteristics, but also demonstrate the sufficiency or insufficiency of the investment funds allocated to the improvement of level crossing safety. Decision-making must be ruled by the quantile criterion, as the probability of not a single incident occurring may seem to be high, yet the probability of one, two, three or more incidents occurring may be unacceptable. The quantile criterion does not have this disadvantage and allows evaluating the number of transportation incidents guaranteed at the specified level of dependability.

Advanced monitoring of rail breakage in double-track railway lines by means of PCA techniques

This work describes a classifier designed to identify rail breakages in double-track railway lines, completing the electronic equipment carried out by authors. The main objective of this proposal is to guarantee the integrity of tracks before the railway traffic starts working. In addition, it facilitates maintenance tasks providing information about possible breakages. The detection of breakages is based on the analysis of eight currents provided by the electronic equipment, one per rail, at the ends of the section (emitting and receiving nodes). The imbalance that occurs among the value of these currents implies that there is at least a breakage in the track section under analysis. This analysis is conducted according to three phases. The first one identifies whether there is a breakage, and, in that case, the damaged track is identified. The second phase provides information about which rail is broken (internal, external or both of them) in the previously identified track. Finally, if there is only one breakage, the third phase estimates its most likely zone along the track section. This situation is considered as a classification problem, and solved by means of the Principal Component Analysis technique. This means that a significant number of measurements is required for every breakage pattern (types of breakages) to be considered. Due to the difficulty of having real data, the proposal has been validated using an 8km-long double-track hardware simulator specially designed by the authors, with specific localizations for breakages.

Canadian main track derailment trends, 2001 to 2014

The Transportation Safety Board of Canada (TSB) maintains the Rail Occurrence Database System (RODS). This database contains information on all types of rail occurrences including derailments that must be reported by all Canadian railway operators. This paper analyzes the derailments that occurred on Canadian main track network between 2001 and 2014. The results from the analysis show that between 2001 and 2014 there was an overall decreasing trend in the number and intensity of main track derailments, derailments involving dangerous goods cars, and the number of derailments resulting in the release of dangerous goods. The RODS data was further analyzed to evaluate the frequency of the differing causes of derailments and the severity of the resulting incidents. The most common and severe derailment causes resulted from rail breaks, track geometry, and environmental conditions. Derailment velocity was also found to have an impact on the severity, with higher velocities resulting in a greater number of derailed rolling stock.

Longitudinal rail weld geometry control and assessment criteria

Abstract This study covers the parametric variations of vehicle and track characteristics to inform on the requirements for an optimum and yet pragmatic control of longitudinal rail weld profile. A statistical study has been carried out using a large set of measured weld profiles (arbitrary mix of flash butt welds and aluminothermic welds) in order to establish relationships between degradation mechanisms and the longitudinal geometry of the finished weld. The potential benefits which would be expected from improved controls over the welded profile, with respect to not only rail running surface damage but also susceptibility to rail breaks and ballast degradation, are demonstrated. Finally, recommendations for the review of the geometric controls of finished weld geometry in the relevant Euro Norms are made.

A Big Data Analysis Approach for Rail Failure Risk Assessment.

Railway infrastructure monitoring is a vital task to ensure rail transportation safety. A rail failure could result in not only a considerable impact on train delays and maintenance costs, but also on safety of passengers. In this article, the aim is to assess the risk of a rail failure by analyzing a type of rail surface defect called squats that are detected automatically among the huge number of records from video cameras. We propose an image processing approach for automatic detection of squats, especially severe types that are prone to rail breaks. We measure the visual length of the squats and use them to model the failure risk. For the assessment of the rail failure risk, we estimate the probability of rail failure based on the growth of squats. Moreover, we perform severity and crack growth analyses to consider the impact of rail traffic loads on defects in three different growth scenarios. The failure risk estimations are provided for several samples of squats with different crack growth lengths on a busy rail track of the Dutch railway network. The results illustrate the practicality and efficiency of the proposed approach.

Detector of Electrical Discontinuity of Rails in Double-Track Railway Lines: Electronic System and Measurement Methodology

This paper describes the design, measurement methodology, and experimental validation of an electronic system for monitoring the electrical discontinuity in rails of double-track railway lines in order to detect the rail breakage. The electronic system is based on an emitter node and on the two receiver nodes. The three nodes, together with the four rails to be analyzed, constitute the electrical circuits, whose currents are measured in both the emission and reception nodes. These nodes can communicate through a data network between them, as well as with a remote center that controls and synchronizes the electronic systems along the railway line. The electronic subsystem associated with the emitter node transmits an encoded signal to the rails, modulated by an 800-Hz carrier. A set of eight currents are measured, one per rail at each end of the section defined between the emitter and the receiver, with a maximum length of 7 km. The evaluation of electrical discontinuities in each section is carried out by means of the relative imbalances that can appear between the eight measured currents, according to possible breakages. The method of measurement is characterized by a high immunity to noise. The results presented here are based on a railway line prototype, which implements the electrical propagation models and coupling between the four rails in the double track. This model allows the proposed electronic system and measurement methodology to be successfully verified.

Контроль температурно-напряженного состояния рельсовых плетей, выброса, разрыва и угона железнодорожного бесстыкового пути при помощи бализы

Контроль температурно-напряженного состояния рельсовых плетей, выброса, разрыва и угона железнодорожного бесстыкового пути при помощи бализы

Broken rails: the privatisation of Estonian railways

Based on the experience of Estonian railways, this article argues that the privatisation of monopolistic infrastructure is economically wasteful and politically divisive. In 2000–2001, Estonia sold the passenger carrier and a portion of the track to domestic businessmen posing as a British strategic investor, and the main freight carrier and most of the track to an American-led consortium. The passenger carrier continued to receive government subsidies but closed several rail lines, which led to protests by passengers. The freight carrier earned large profits from the transit of Russian oil to Europe, but invested its money in buying used American locomotives, rather than rebuilding the track. Both companies laid off about half of their workforce, provoking the first private-sector strike in Estonia since the collapse of Communism. In 2006, a new government bought back the freight services and track at more than twice the sale price, an expensive lesson in the perils of privatisation.

Risk-Based Optimization of Rail Defect Inspection Frequency for Petroleum Crude Oil Transportation

The rapid expansion of production of North American petroleum crude oil from shale has led to a significant increase in rail transport of crude oil. Broken rails are frequent causes of train accidents. Ultrasonic rail defect inspection is widely used to prevent train accidents caused by broken rails, thereby reducing the hazardous materials transportation risk. This paper describes a new methodology to estimate unit-train crude oil transportation risk by the frequency of location-specific rail defect inspection. The risk model was used to develop a Pareto optimization model that determines the frequency of segment-specific rail defect inspection to reduce the total-route risk in a cost-effective manner. A numerical case study was developed to illustrate the application of the risk analysis and optimization models. This research is intended to provide new methods and information to assist the railroad industry in optimizing investment in infrastructure improvement, thereby mitigating the risk of rail transport of crude oil and other hazardous materials.

Measures Against Electrolytic Rail Corrosion in Tokyo Metro Subway Tunnels

Tokyo Metro Co., Ltd. is operating nine railroad lines (195.1 km) forming a network mainly consisting of subways in Tokyo, the capital of Japan. Good maintenance of tracks is essential to the safety of passengers. However, rail breakage due to electrolytic rail corrosion is occurring in some underground spaces. Rail corrosion occur frequently in subway tunnel due to underground water leakage. For some place, we have to change rails every a half year. So it is big problem for underground space. We have been examining electrolytic rail corrosion for three years. By producing maps of places prone to electrolytic rail corrosion, divided into 25-m sections, we analyzed track conditions and identified the causative factors of electrolytic corrosion depending on track conditions. In addition, we focused our attention on chemical approaches to the prevention of electrolytic corrosion. First, we conducted chemical analyses of samples of electrolytic corrosion products and samples of water collected from the environment where electrolytic corrosion occurred. The results suggested that akaganeite, which forms in the high Cl– concentration in underground spaces. promoted the loss of rail strength. Next, we examined the effectiveness of the sacrificial metal method in delaying electrolytic corrosion. The use of zinc, a metal with higher ionizing tendency than iron, in the form of adhesive tape attached to steel surfaces, was effective in delaying electrolytic rail corrosion. This report discusses the details of the conventional physical approach relying on rail replacement planning and the chemical approach to the prevention of electrolytic corrosion with some insight into future developments.

Investigation of Continuously Welded Rail of Ballastless Longitudinal Stress Distribution of Rail Break

Abstract A three-dimensional ballastless track model was established using a finite element method to simulate the rail condition before and after rail break. The distribution of the rail longitudinal stress was analyzed under certain thermal stress. In addition, experiments were also conducted in order to validate the simulation results using rail longitudinal stress test equipment. It was found that the simulation results agreed reasonably well with the experimental results. The tests show that the simulation results could correctly predict the longitudinal stress distribution in the rail. Finally, rail longitudinal stress distributions under different thermal stress were calculated using this model; this is helpful for future application to determine when and where there may be a rail break.