Rail Geometry Research Articles

Systematic Literature Review on Data-Driven Models for Predictive Maintenance of Railway Track: Implications in Geotechnical Engineering

Conventional planning of maintenance and renewal work for railway track is based on heuristics and simple scheduling. The railway industry is now collecting a large amount of data with the fast-paced development of sensor technologies. These data sets carry information about the conditions of various components in railway track. Since just before the beginning of the 21st century, data-driven models have been used in the predictive maintenance of railway track. This study presents a systematic literature review of data-driven models applied in the predictive maintenance of railway track. A taxonomy to classify the existing literature based on types of models and types of applications is provided. It is found that applying the deep learning methods, unsupervised methods, and ensemble methods are the new trends for predictive maintenance of railway track. Rail geometry irregularity, rail head defect, and missing rail components detection were the top three most commonly considered issues within the application of data-driven models. Prediction of rail breaks has received increasing attention in the last four years. Among these data-driven model applications, the collected data types are the most critical factors which affect selecting suitable models. Finally, this study discusses upcoming challenges in the predictive maintenance of railway track.

Observed failures at railway turnouts: Failure analysis, possible causes and links to current and future research

Railway turnouts are a necessary part of railway infrastructure, used throughout the network to direct trains to the desired path, thus ensuring the smooth running of every train. Their reliability and availability is therefore an essential element for the efficiency of the entire network. However, the combination of movable parts, some of which with reducing cross sections and structural integrity, discontinuities in the rail geometry and variability in the system support stiffness leads to high failure rates compared with plain line track and to very high maintenance and renewal costs. In this paper, the database of failures occurred in the GB network between 2011 and 2017 has been statistically investigated with the support of free-text analysis techniques to interrogate the comments provided by the on-track maintenance staff. The key failures and possible causes have been identified for both the switch and crossing panels as well as areas for future research to support the development of the next generation of switches and crossings.

Estimating Exceedance Probabilities of Railway Bridge Vibrations in the Presence of Random Rail Irregularities

This contribution addresses the estimation of exceedance probabilities of the dynamic random response of railway bridges subjected to high-speed trains in the presence of random rail irregularities. The random nature of the irregular rail track is described by a spatial ergodic stochastic process, and consequently the dynamic bridge response becomes a stochastic process in time with generally unknown distributions. Using numerical simulation methods, the response thresholds for bridge deflection and acceleration are estimated to obtain small exceedance probabilities. Combining these limits with the response at perfect rail geometry provides an estimate of the dynamic response amplification due to random rail irregularities. This is in line with the semi-probabilistic safety concept of modern civil engineering, where critical response thresholds for structures are associated with small exceedance probabilities. It is shown that modeling the maximum bridge deflection as a normally distributed random variable with parameters fitted to the results of a Monte Carlo simulation with small sample size is a computationally efficient approach for estimating the amplified deflection. In contrast, the random maximum bridge acceleration is better captured by a lognormal distribution. As an efficient alternative, the subset simulation method provides accurate predictions for very small exceedance probabilities. If the amplitudes of the rail irregularities at discrete spatial coordinates along the rail axis are considered as random variables, the stability of subset simulation increases.

Fractal analysis of high speed rail geometry data: A case study of Ankara-Eskişehir high speed rail

Abstract By considering railway track geometry as a fractal pattern, the irregularity of the track geometry can be expressed numerically with the help of fractal dimensions. In this study, a novel algorithm based on ruler method has been developed and a program was written to determine the fractal dimensions of railway track geometry graphs. Four different fractal dimensions of DR1, DR2, DR3, and DR4 were proposed to determine the geometric irregularity of the railway track by using the data of Ankara-Eskisehir High-Speed Railway track. DR1 and DR2 were used to quantify short wavelength irregularities while DR3 and DR4 were used to quantify medium wavelength irregularities. At the end of the study, the relationship between fractal dimensions and standard deviation values, which is the quality indicator according to EN 13848-6, was investigated. According to this, there is a strong relationship between the DR3 and the standard deviation.

Optimization of a Convex Rail Design for Electromagnetic Launchers

A rail geometry with a convex cross section instead of a rectangular one provides a higher contact area, uniform current density, and less transition on the contact surface, and it increases the performance in electromagnetic launchers. In addition, the design of convex rails should be considered together with armature structure, the distance between rails, rail length, and parasitic masses that all have an influence on the overall efficiency and armature/rail transition. A novel complete rail and launch package optimization method is presented in this article. In the first part of this article, the optimum convex rail cross sections for five different separation values are found to obtain uniform current density distribution on rail cross section. For this part, a transient finite element (FE) model in 2-D is developed to calculate the current density distribution and combined with a real-coded genetic algorithm (GA). Then, the armature and sabot petal masses are calculated for each optimized rail geometry and each separation values. In the second part, the efficiency of each optimum design with different separation values is evaluated by a transient 3-D FE model with transient solver taking the calculated armature and sabot petal masses into account. Finally, the length of the rails of the final design is investigated for the transition phenomena. It is observed that 48-mm rail separation with 12.9- and 21-mm elliptical cross-sectional parameters has the highest exit velocity (2355 m/s) for 400-g projectile with uniform current density at inner rail surfaces.

Influence of Filleting and Tapering of Rails on Railgun Parameters

The geometry of rails and armature is one of the most important parameters considered while designing a railgun. Optimized designs reduce the unnecessary loss of energy in the railgun, thus imparting higher kinetic energy to the projectile. This article proposes a new filleted and tapered rail geometry for a railgun and analyzes the improvements obtained by the geometry change with the existing conventional railgun geometry. A pulse-forming network consisting of cable resistances is designed to input the same energy in to the conventional and new railgun geometries. An electromagnetic-mechanical coupled analysis is performed using LS-DYNA to determine the parameters of the railguns. Breech voltages and breech energy are calculated to determine the barrel efficiency and total system efficiency. Compared to conventional electromagnetic railgun (EMRG), the new railgun results in a 3% larger Lorentz force, 9.2% greater exit velocity, and an improved barrel efficiency and total system efficiency.

The role of stiffness variation in switches and crossings: Comparison of vehicle–track interaction models with field measurements

The performance of switches and crossings compared with plain line is complicated by the presence of movable parts, changing rail geometry and non-uniformities in the composite and/or trackbed stiffness. These features lead to complex vehicle–track interactions and higher maintenance costs. The trackbed stiffness is the least well-controlled engineering property. A greater variability in trackbed stiffness leads to higher differential trackbed settlement and associated poorer track quality. At switches and crossings, changes in trackbed stiffness are exacerbated by changing rail properties which also contribute to changes in the overall composite track stiffness. This work focuses on the role of variations in stiffness on the performance of switches and crossings. Field measurements of bearer displacement were carried out using geophones at a switch and crossing equipped with under sleeper pads. The vehicle–switch and crossing interaction was modelled using a multi-body system and finite element method. The trackbed stiffness along the whole of the switch and crossing was inferred using the measurements of track deflections in an iterative back-calculation taking account of changing rail properties. It is shown that not including the variation in trackbed/composite stiffness leads to significant under/overestimates of the wheel–rail contact forces. Under sleeper pads are shown to reduce absolute maximum loads, but may increase the variation in deflection.

Experimental and numerical investigations of rail behaviour under compressive force on ballastless track systems

Aiming to verify the behaviour of ballastless track systems under high compressive rail forces occurring in the vicinity of bridge joints due to track bridge interaction, numerical and experimental studies are described in this paper. At first, a short summary of background information on the allowable rail stresses under compressive force on ballasted track systems is presented. Subsequently, a numerical pre-study for ballastless systems is performed. The unfavourable imperfection cases and loading procedures in transverse direction for experimental tests are determined. Based on these results, two rails are experimentally tested to achieve practical results. To ensure safety and reliability of the system, a specific testing program and a measurement concept are developed. Main testing results including the rail geometry, deformation and stress development are compared and discussed. Additionally, numerical models to evaluate the rail behaviour are improved and verified. A good consistency between the finite element model and the testing results could be achieved. The performed investigations give a scientific basis in order to increase the allowable rail compressive stresses in comparison with the existing values in the codes. A higher allowable rail stress considerably improves the design conditions for long railway bridges.

Analysis of a Tramcar Ride when Passing a Point Frog and when Entering Small Radius Arc by Specific Rail Geometry

In urban railway environments, in many respects, the problem of tramcars passing small radius arches appears to be topical. In this regard, the authors proposed that the wheelsets should be complemented on the outer side of the wheels with a second tread of a lower radius, intended exclusively for ride in arches of the track with a radius which the conventional wheelsets cannot even theoretically pass without creep (subject of patent application a201701589). The complemented wheel tread enters into operation (or out of action) as a result of passing over a specially shaped rail located in the intersections before and behind the small radius arc. In this process, there is a change in the wheel-rail contact location - similar to what is commonly used when riding on a facing rail located in the immediate vicinity of the point frog. The paper deals with the comparison of these two cases based on a simulation analysis of vehicle ride in the calculation program.

Spark channel dynamics in railgun switches in unipolar and oscillatory discharges

AbstractSpark gaps are often used to commute energy in the discharge of a capacitive storage to a load. In some applications, a unipolar pulse is not feasible, and an oscillatory (underdamped sinusoidal) regime must be realized for the discharge of the capacitor bank. Spark gaps, which were developed for unipolar discharge, cannot be directly employed in an under-damped (oscillatory) regime since at the transition of the current through zero, the spark channel could stop motion and ignite in the following half period. This work has two main objectives: (i) To develop and test a simulation model of spark channel motion in linear rail geometry, which must be valid for both the oscillatory and unipolar regimes of capacitor bank discharge; and (ii) to investigate arc motion and electrode heating, depending on the current and charge transfer, over a wide range of operation. A self-consistent treatment of plasma motion and electrode heating (taking into account the radiation of a plasma channel) is applied in the present paper, and it is shown that radiation can significantly impact on the temperature of the electrodes. Electrode ablation and the temperature dependence of the main thermal parameters are also taken into account. Stainless steel (Cr/Ni/Ti 18/10/0.6÷0.8), copper (Cu), chromium (Cr), tungsten (W), and molybdenum (Mo) are used here as electrode materials since these materials are widely used for the manufacture of electrodes. The results of numerical calculations are compared with experimental results, and conditions are defined for reduced electrode erosion.

Investigation of Rail Deformation and Stress Wave Propagation in the ISL-NGL60 Railgun

Railgun performance requires a low-resistance electric gliding contact between the rails and the armature. The electromagnetic forces, which accelerate the launch package (0.7 to 3 kg mass) up to more than 2000 m/s, are acting on the rails as repulsive forces. Therefore, the rails of the NGL60 electromagnetic gun, with caliber 60 $\times$ 60 mm2, are held in their position by an arrangement of discrete steel bolts, further by beams and plates made of glass fiber reinforced plastic, as well as by stiffening metal plates. The highly dynamic electromagnetic forces generate stress waves and elastic rail deformation that might contribute to contact transition between the rails and the armature. If the rail deformation enters the plastic domain, the rail geometry may be altered in an unfavorable way for subsequent shots. For our numerical investigation, we used the multiphysics finite-element computation code LS-DYNA to simulate a railgun projectile launch with a moving armature by injecting an electric current into the rails. It is therefore possible to study the dynamic deformations during the launch and get insight in the dynamic stress states. The material models for the rails and for the armature take into account elastic-plastic stress-strain behavior as well as strain rate sensitivity. We expect to simulate launch dynamics with higher accuracy than previously presented models with a nonmoving armature. The principal objective of the study is to show that this procedure is capable of effectively optimizing the structural behavior of the rails inside the barrel.

Analysis of a tram car ride when passing point frog and when entering curve by specific rail geometry

In urban railway environments, the problem of tramcars passing small radius arches appears to be topical. In this regard, the authors proposed that the wheelsets should be complemented on the outer side of the wheels with a second tread of a lower radius, intended exclusively for ride in arches of the track with a radius which the conventional wheelsets cannot even theoretically pass without creep. The complemented wheel tread enters into operation (or out of action) as a result of passing over a specially shaped rail located in the intersections before and behind the small radius arc. In this process, there is a change in the wheel-rail contact location similar to what is commonly used when riding on a facing rail located in the immediate vicinity of the point frog. The paper deals with the comparison of these two cases based on a simulation analysis of vehicle ride. It can be evaluated, that changing the contact point when entering the arc by means of the proposed rails takes place in a more favourable way. It is possible to assume nearly 4 times longer service life of the proposed shaped rail than the one of a frog point.

An analytical solution to the mapping relationship between bridge structures vertical deformation and rail deformation of high-speed railway

This paper describes a study of the mapping relationship between the vertical deformation of bridge structures and rail deformation of high-speed railway, taking the interlayer interactions of the bridge subgrade CRTS II ballastless slab track system (HSRBST) into account. The differential equations and natural boundary conditions of the mapping relationship between the vertical deformation of bridge structures and rail deformation were deduced according to the principle of stationary potential energy. Then an analytical model for such relationship was proposed. Both the analytical method proposed in this paper and the finite element numerical method were used to calculate the rail deformations under three typical deformations of bridge structures and the evolution of rail geometry under these circumstances was analyzed. It was shown that numerical and analytical calculation results are well agreed with each other, demonstrating the effectiveness of the analytical model proposed in this paper. The mapping coefficient between bridge structure deformation and rail deformation showed a nonlinear increase with increasing amplitude of the bridge structure deformation. The rail deformation showed an obvious feature; with the increase of bridge span and fastener stiffness, the curve of rail deformation became gentler, the track irregularity wavelength became longer, and the performance of the rail at following the bridge structure deformation was stronger.

Numerical simulation of spark channel dynamics in railgun switches

Discharge of a capacitive storage on a load with unipolar pulse is employed for pumping of powerful lasers and also for feeding of electromagnetic launchers, and pulsed high magnetic field facilities. Spark gaps are often used to commute energy on a load. In some applications unipolar pulse is not feasible and oscillatory regime (underdamped sinusoidal) has to be realized for the capacitor bank discharge. Spark gaps, developed for unipolar discharge, cannot directly be employed in under-damped (oscillatory) regime, because at current transition through zero the arc channel could stop motion and ignite at initial place on the following half period. Two main objectives were pursued in this work: 1. develop and test simulation model of a the spark channel motion in linear rail geometry for the oscillatory regime of capacitor bank discharge; 2. Investigate arc motion and electrodes heating depending on the current and charge transfer in wide operation range.

Optimisation of support stiffness at railway crossings

ABSTRACTTurnouts are a key element of the railway system. They are also the part of the system with the highest number of degradation modes and associated failures. There are a number of reasons for this, including high dynamic loads resulting from non-uniform rail geometry and track support stiffness. The main aim of this study is to propose a methodology to optimise the pad stiffness along a crossing panel in order to achieve a decrease in the indicators of the most common failure modes. A three-dimensional vehicle/track interaction model has been established, considering a detailed description of the crossing panel support structure. A genetic algorithm has been applied to two main types of constructions, namely direct and indirect fixing, to find the optimum combinations of resilient pad characteristics for various cases of travelling direction, travelling speed and support conditions.

On the overriding issue of train front end collision in rail vehicle dynamics

ABSTRACTA three-dimensional dynamic model of crashed vehicles coupled with moving tracks is developed to research the dynamic behaviour of the train front end collision on tangent tracks. The three-dimensional dynamic model consists of a crashed vehicle model, moving track models, a simple wheel–rail contact model, a velocity-based coupler model and the model of energy absorption and anti-climbing devices. The vector method dealing with the nonlinear wheel–rail geometry is put forward in the paper. The developed model is applicable in the scope that central collisions occur on tangent tracks at low speeds. The examples of the vehicle impacting with a rigid wall and the train front end collision are carried out to obtain the dynamic responses of vehicles. The overriding issue is studied on the basis of the wheel rise in train collisions. The results show that the second bogie of the first colliding vehicle possesses the maximal wheel rise. The wheel rise increases with the increase of vehicles. However, the number of vehicles has tiny influence on the overriding in train collisions at low speeds. On the contrary, the impact speed has significant influence on the overriding in train collisions. The wheel rise increases rapidly if the impact speed is close to the critical speed of overriding. The large wheel rise is principally generated by the great coupler force related to the rigid impact in the axial direction.

Control Measurements of Crane Rails Performed by Terrestrial Laser Scanning

This article presents a method for measuring the geometry of crane rails with terrestrial laser scanning (TLS). Two sets of crane rails were divided into segments, their planes were adjusted, and the characteristic rail lines were defined. We used their profiles to define the positional and altitude deviations of the rails, the span and height difference between the two rails, and we also verified that they complied with the Eurocode 3 standard. We tested the method on crane rails at the hydroelectric power plant in Krško and the thermal power plant in Brestanica. We used two scanning techniques: “pure” TLS (Riegel VZ-400) and “hybrid” TLS (Leica MS50) scanning. This article’s original contribution lies in the detailed presentation of the computations used to define the characteristic lines of the rails without using the numeric procedures from existing software packages. We also analysed the influence of segment length and point density on the rail geometry results, and compared the two laser scanning techniques. We also compared the results obtained by terrestrial laser scanning with the results obtained from the classic polar method, which served as a reference point for its precision.

Simulation of the Motion of Charged Particles in an Ablative Pulsed Plasma Thruster at the Initial Stage of the Discharge

A basic scheme of an ablation pulsed plasma thruster with rail geometry and a side feed of the propellant bar is considered. For such geometry, a theoretical description of the initial stage of the vacuum discharge, which would serve to explain the experimental results, does not exist. It was demonstrated experimentally that the configuration of the discharge channel depends essentially on the initial stage of discharge. A model of the motion of charged particles in the inhomogeneous electric and magnetic fields was developed. Due to the low plasma density at the initial stage of discharge, the model of the charged particles motion in electric and magnetic fields is described well by differential equations.

A multi-criteria methodology to evaluate the optimal location of a multifunctional railway portal on the railway network

The installation of a multifunctional railway portal (or TCCS – Train Conformity Check system) can contribute to improve the safety of a railway infrastructure. The TCCS can detect the conformity of the trains traveling along the tracks, and can transfer the status information to a main traffic control center. This paper proposes a methodological approach based on Analytic Hierarchy Process (AHP) to evaluate the optimal locations to install a TCCS on a railway section. The eligibility and ranking of the potential sites have been defined with respect to constraints related to the rail line track layout and geometry, the TCCS technological features, and the required safety distance allowing the train to stop. The proposed approach has been applied to a real case study on the Italian railway.

Electromechanical Performance of Rails With Different Cross-Sectional Shapes in Railgun

Railgun is a kind of electromagnetic launcher that can accelerate masses in the range from milligrams to tens of kilograms to velocities more than several kilometers per second. The cross-sectional area's moment of inertia is one of the most important mechanical properties of the rails, affecting the critical velocity and launch performance. The current distribution in the railgun determines its efficiency and contact performance of rail/armature sliding. Factors that affect the electromechanical performance of the rails include geometry and material. To improve the electromechanical performance, two types of rails with convex and concave cross sections are designed by adding and removing arch forms to/from the conventional flat rails. Modified C-shaped armatures are constructed for each rail geometry. This paper presents the results on mechanical performance on the basis of structural analysis and current distribution from coupled EM-structural simulations. The results show that the moments of inertia of convex and concave rails are larger than those of flat rails for a given cross-sectional area and rail width, but the differences in mechanical performance among the three geometries are not significant, and the advantage of rails with larger moments of inertia for a given cross-sectional area is limited. The inductance gradient of the flat railgun is larger than those of the others, and the concave railgun has the smallest; consequently, the concave railgun is the least efficient. Compared with the flat and concave rails, the current density of the convex rail is smaller at the bore-side rail surface, but greater at the contact interface, especially at the trailing edge of the armature.