Rail Geometry Research Articles

Laser Scan Compression for Rail Inspection

The automation of rail track inspection addresses key issues in railway transportation, notably reducing maintenance costs and improving safety. However, it presents numerous technical challenges, including sensor selection, calibration, data acquisition, defect detection, and storage. This paper introduces a compression method tailored for laser triangulation scanners, which are crucial for scanning the entire rail track, including the rails, rail fasteners, sleepers, and ballast, and capturing rail profiles for geometry measurement. The compression technique capitalizes on the regularity of rail track data and the sensors’ limited measurement range and resolution. By transforming scans, they can be stored using widely available image compression formats, such as PNG. This method achieved a compression ratio of 7.5 for rail scans used in the rail geometry computation and maintained rail gauge reproducibility. For the scans employed in defect detection, a compression ratio of 5.6 was attained without visibly compromising the scan quality. Lossless compression resulted in compression ratios of 5.1 for the rail geometry computation scans and 3.8 for the rail track inspection scans.

Evaluation of a permanent SHM system performance in detecting damage scenarios considering runnability thresholds

Due to an increasing number of bridges approaching the end of their design lives, there is a growing interest by the infrastructure managers on monitoring systems able to provide information on the service capability of structures. Focusing, in particular, on railway bridges, serviceability is related to both structural serviceability and runnability, where the first is related to the structural capability of the bridge, while the second is related to the constraints on rail geometry. In this work the authors present an investigation of the capability of a permanent monitoring system to detect the presence of damages that would lead to an exceedance of the structural threshold values imposed by runnability norms. The target structure is a double-span Warren truss railway bridge, located in Italy, designed in 1946 and currently instrumented with a permanent monitoring system. The latter performs dynamic, quasi-static and static measurements, with sensors ranging from velocimeters to end displacement transducers and clinometers. Thanks to a FE model of the actual structure, a set of damage scenarios can be simulated, defining the damage entities that lead to the exceedance of thresholds imposed by norms in terms of runability assessment. As a result, the installed sensors mesh was found to distinguish such critical structural conditions as well as lower entity damage scenarios. The paper discusses the capability of different sensor configurations and monitoring strategies (“dynamic”, “static”, etc) to detect such damage scenarios, in terms both of “early warning” capability and of minimum time required to detect the anomaly. The same approach can be extended to the analysis with respect to structural serviceability limits.

Embedding Kalker's variational theory into railway vehicle system dynamics and its efficiency improvement

The wheel–rail contact plays a vital role in railway transportation, hence an accurate wheel–rail contact model is the key to the simulation of railway vehicle dynamics. Though Kalker's variational theory is the canon, fewer works try to embed it into railway vehicle dynamics, mainly due to the computational efficiency problem and the complex wheel–rail geometry processing. This paper proposes a wheel–rail geometry processing method to embed KVT into railway vehicle multi-body dynamics based on the trajectory coordinate formulation, which conveniently introduces the wheel–rail contact surface pair for tracking the potential contact areas. After this prior detection, coarse detection is performed to narrow the range of penetrated elements. Multiple contact patches can also be identified based on the connection topology of discrete elements of wheel–rail surfaces. Thus, Kalker's variational theory can be used on each separate patch for local contact evaluation. An initial prediction method for the contact status is embedded in the multi-body dynamics simulation to accelerate the solution of Kalker's variational problem, in which the tractions with contact divisions obtained from the neighbouring system states are selected as the iterative initial value. The importance of predicting the contact tractions and demarcation for the convergence of the iteration is revealed. The proposed method is fully demonstrated by the Manchester contact benchmark and simulations of a railway vehicle passing through a curved track. As an advantage of embedding Kalker's variational theory, the precise traction pattern is obtained simultaneously along with the vehicle dynamics simulation, and the influencing mechanism of the track geometry on the vehicle system is analysed. The improvement of solution efficiency is also verified in simulations.

Influence of multi-layer laser cladding depositions and rail curvature on residual stress in light rail components

Rapid deterioration of critical rail components due to wear and fatigue is a significant challenge faced by the railway industry. Laser cladding has been applied to straight and curved light rail substrates which are particularly prone to these methods of degradation using a Stellite 21 hardfacing alloy. The influence of multi-layer cladding depositions, grinding-based finishing procedures and substrate rail grade on residual stress was analyzed using non-destructive neutron diffraction techniques. As cladding is a thermal process, microstructural changes from the heat inputs can result in a high internal stress state which reduces the loading capacity whilst a high hardness increases the likelihood of brittle failure. Stellite laser cladding depositions were found to result in low tensile residual stresses within the cladding layer, which become compressive in the heat affected zone (HAZ). Repeated thermal inputs from multi-layer cladding depositions did not negatively impact the hardness or microstructure after double layer laser cladding and increased the residual stress to 100 MPa at the cladding surface after grinding. Laser cladding on a curved rail substrate also produced increased internal stress after cladding due to higher strains resulting from the rail geometry but remained below the yield limit of the cladding and substrate material. These outcomes were compared to current literature indicating this critical combination of low internal strain and a cladding and HAZ hardness complementing the substrate material is difficult to achieve. Therefore, ensuring laser cladding is compatible with a variety of light rail components is essential in developing viable maintenance techniques to recondition critical railway infrastructure to avoid disruptive replacement procedures.

Phenomenology of High-Current Discharge in N2 and He at Medium Pressures between Two Electrodes of Rail Geometry

Phenomenology of High-Current Discharge in N2 and He at Medium Pressures between Two Electrodes of Rail Geometry

Rail configuration for lateral particle transport across intact co-flows: effect of wall and rail geometry on liquid and particle transport.

Layer-by-Layer coating technology is of great importance for many applications of microparticles whereby exposure of the particles to various reagents is needed. Mutual contamination of the reagents during this process is a key challenge, and this undesired effect should be avoided. Here we introduce a device that provides subsequent exposure of particles to various liquids and minimizes mixing of the liquids at the same time. The key element of the device is a rail (groove) at the bottom of a microfluidic channel. The rail forms an angle (between 0 and 90 degrees) and thus enables passive transport of particles through the intact co-flows of the different fluids. To avoid the undesirable effect of reagent stream mixing, internal walls are introduced to separate the different flows. Various designs of the proposed device are considered, and their performance is experimentally analyzed.

Analysis of the Main Factors Affecting the Current Density and Temperature of Electromagnetic Rail

In order to study the influence of different factors on the electromagnetic rail temperature, under the condition of control variables, the variation of current density and temperature in the rail are simulated by COMSOL simulation software under different input current, current waveform, rail geometry, and material. The calculation results show that the peak value of input current has little effect on the distribution of rail current density and temperature, but has a significant effect on the maximum current density and maximum temperature rise on the rail. Shortening the rising time of the input current can quickly increase the armature speed and the rail temperature, but the change of current waveform has little effect on the maximum current density, maximum temperature, and friction heat. Rail conductivity, height, width, armature diameter, and length are negatively correlated with rail maximum current density and maximum temperature. The research conclusion has a certain guiding significance for optimizing the structure design of electromagnetic rail gun and controlling electromagnetic launch conditions.

Rail gage-based risk detection Using iPhone 12 pro

Federal Railroad Administration strictly regulates the inspection frequency of all track classes to ensure timely identification of rail defects including irregular gage which is a devastating rail geometry defect. Conventional rail inspection methods are both costly and labor-intensive, whereas existing novel technologies can be expensive and mostly focus on a specific inspection area, e.g. vertical alignment. iPhone 12 Pro was introduced to the public recently with a low-cost, low-resolution light detection and ranging (LiDAR) sensor that is purposed for better photography and virtual reality. Thanks to its portability and computational capacity, iPhone 12 Pro can potentially be used as a portable solution for irregular gage inspection, whose capacity and feasibility are unknown. This study first investigated the capability of the iPhone 12 Pro in calculating unloaded rail gages by its embedded LiDAR sensor. The results showed that uncalibrated raw gage values measured by the iPhone 12 Pro LiDAR sensor were systematically lower than the ground-truth values. The proposed method in this study then introduced logistic regression to calibrate the measured values through balancing the prediction performance and the efficiency, followed by validations using a Gaussian process classifier. The results show that the proposed method correctly identified all 39 high-risk locations with 227 false alarmed locations. The proposed method with the iPhone 12 Pro LiDAR sensor could potentially narrow down the possible “high-risk” gage sections and may result in a significant reduction in the field inspection workload by 48%.

Suspension parameters design for robust and adaptive lateral stability of high-speed train

An adequate hunting stability margin is required through the optimisation and matching of bogie suspension parameters for high-speed trains. Moreover, the dynamics design is particularly important for the robust lateral stability to adapt to wheel–rail wear and track deformation. The hunting stability margin of vehicles, as well as the wheel–rail contact state adaptability should be taken into account. In this regard, the robust hunting stability Pareto optimisation of bogie suspension parameters for different wheel–rail wear stages is executed. A method for the centralised optimisation of key bogie suspension parameters based on vehicle lateral robust stability is presented, and the principle of two typical parameters matching for high-speed vehicles is summarised. In addition, in order to make the vehicle automatically adapt to different wheel–rail geometry contact states without any sensors and control systems, a new idea of frequency-dependent stiffness (SDF) of yaw damper is proposed to ensure the lateral stability margin especially in extreme wheel–rail contact states, which is verified through the vehicle linear system stability and ride comfort comparative analysis. Finally, the adaptive stabilisation mechanism of the vehicle with the frequency-dependent stiffness of yaw damper is clarified.

Influence study of rail geometry and track properties on railway rolling noise

Wheel/rail interaction generates an excitation due to the roughness present on the surface of both components that produces vibration and consequently rolling noise. In this work, the railway track properties that most influence rolling noise are identified and this influence is analysed to reduce noise emission. The acoustic calculation methodology consists of characterizing the wheel using finite element techniques and the track using periodic structure theory. The influence of the track properties on the sound radiation is analysed by means of statistical techniques applied to the acoustic power results of different track configurations. To achieve this, the rail cross-section geometry is parameterized and numerous simulations are carried out by modifying these geometric parameters and the viscoelastic properties of the track components. Considering the contribution of the wheel, rail and sleeper, the results obtained indicate that the total radiation can be reduced by up to 7.4 dB(A) through an optimal combination of the track design parameters, compared to the worst combination found. In particular, the rail pad stiffness is shown to be the most influential parameter in the sound radiation.

Railway track availability modelling with opportunistic maintenance practice

The geometry of railway track must be maintained within certain standards in order to provide a highly available network, as well as good ride comfort and safety for all rail users. Modelling is well utilised as part of asset management tools in exploring the effectiveness of different rail geometry maintenance strategies. By considering the rail route as an entire system – in contrast to a track section in isolation – a more effective maintenance strategy can be developed, including the deployment of opportunistic maintenance practice. This study presents a Coloured Petri Net model of railway track degradation, inspection, and maintenance planning and delivery, for an entire route of track sections. Opportunistic maintenance is introduced through a novel search transition function, which groups interventions based on local adjacency. Testing explores the availability and maintenance demands expected when following a series of different management strategies. This is extended to testing under heatwave conditions, a known disrupter to track geometry maintenance delivery. Simulation results show that in following an opportunistic strategy, greater availability can be achieved on the modelled rail line. Further, resilience to the heatwave disruptions can be achieved by selecting the correct maintenance strategy parameters. This asset management tool can provide guidance on management strategies for a full route of track sections as a combined system.

Study on Effect of Rail Filet Radius in Electromagnetic Railgun

Enhancing the inductance gradient of an electromagnetic railgun (EMRG) directly translates to an improvement in the force on the projectile. Fileting the rails on one side is one of the ways to improve the inductance gradient. This work focuses on the effects of filet arc radius on different parameters of inductance gradient, current density distribution, magnetic flux density, barrel efficiency, breech energy, and critical velocity. The performance of rails with filet arc radius of 2, 4, and 6 mm are compared with the conventional cuboid shape rail geometry. Dynamic field distributions are analyzed by simulating the designed systems in LS-DYNA. A magneto-static analysis is performed using Ansys-Maxwell to determine the magnetic flux density produced behind the armature. It is observed that there is an increase in the flux density and barrel efficiency when filet radius increases. An improvement of 3.81% is observed in the flux density and the barrel efficiency improved from 24% in conventional rails to 27% in rails with a filet radius of 6 mm.

On the issue of improving the methodology for confirming maximum safe (design) speed of freight railcars

The article provides the analysis of regulatory documents and scientific publications concerning the design speed of rolling stock. The material is provided from the perspective of a methodological approach to establishing the design speed at the level of the maximum value achieved during dynamic and strength tests and track impact tests of the object that meets requirements of technical documentation. Values of strength and dynamic properties of cars obtained during tests performed in track sections with characteristics established in test methods should comply with requirements of regulatory documents. At the same time, during the operation of car running gear, rail geometry and track superstructure, basically have a state that is different from that in which tests were performed. Proceeding from this, in order to ensure traffic safety in operation, permissible speeds are set for tracks of various states and structures. Thus, for freight cars with three-piece bogies, the maximum speed, especially when empty, is limited due to the deterioration of its dynamic properties associated with change in the operation of design parameters and characteristics of bogie elements as well as its rigidity couplings. Due to the deterioration of dynamic properties , the design speed cannot be implemented, including on the track that meets requirements of test methods, on which it was initially confirmed. The maximum permissible speeds of freight cars that are acceptable from the safety point of view are traditionally established based on the results of tests performed since the middle of the last century. When applying innovative freight cars with bogies of a new design, to assess traffic safety, it will be necessary to carry out a large number of tests and to gain operating experience, during which it is necessary to estimate the influence of various factors on traffic safety. In fact, it is necessary to repeat tests to set running speeds, but in a short time, which is very cost-intensive. Based on the foregoing, in order to eliminate the risks associated with safety violation, to confirm the design speed and in order to reduce costs when applying new rolling stock, a full-scale virtual method has been proposed that provides the use of a computer simulation, in which the design speed specified in the technical documentation is set at the stage of rolling stock development, taking into account the operational variability of car running gear and the track state.

Investigations on the influence of prestressed concrete creep on train-track-bridge system

In response to long-term operation of prestressed concrete railway bridges, the girder body will arch because of creep, which may influence the running stability of high-speed trains. Usually, the deformation of the rail-bridge system under the creep effect is calculated by a finite element model with the rail geometry deformation input as additional irregularity. The original irregularity is superimposed to the coupled system of the train and bridge to calculate the dynamic response of the system. However, such a strategy is time-consuming and cannot accurately integrate the uncertainty of the original rail irregularity. This paper presents an analytical formula for predicting the rail deformation caused by concrete creep. The rail deformation caused by the bridge upper arch can be quickly predicted by the creep amplitude of the bridge. The creep deformation of the rail is applied as an irregularity excitation to the train-track-bridge coupled system (TTBCS). In addition to creep irregularities, original random irregularities also exist on the track. The Karhunen-Loéve expansion method is adopted to represent the random track irregularity that considers creep deformation. The results achieve good agreement with the initial samples. Subsequently, the TTBCS model is established to analyze the dynamic responses of different train speeds and different bridge creep deformations using a stochastic dynamic analysis method. This method achieves very high agreement with the Monte Carlo method, and the error rate of the mean bridge displacement calculated by both methods under the same working conditions was only 0.0351%. Finally, the upper probability limit value of the creep of the bridge is put forward: at a speed of a high-speed train of 350 km/h, the creep upper arch limit is only 7 mm. These probability limits at different train speeds have guiding significance for the design, maintenance, and repair of the actual medium–high-speed railway concrete supported beam bridge.

Research on the Prediction of Geometric Irregularity of Railway Track Based on BP Neural Network

Traditional data analysis methods and methods are difficult to effectively mine and analyze a large number of Rail Geometry state data, which makes the value of data cannot be fully utilized and played. Based on this, this paper first analyses the characteristics of railway track geometric irregularity, then studies the BP neural network prediction method and steps of railway track geometric irregularity, and gives its prediction effect.

Efficient 3d finite element modeling of cyclic elasto-plastic rolling contact

Railway rails accumulate large plastic deformations due to cyclic rolling contact loading. The plastic deformations alter the rail geometry, affect material behavior, and cause crack formation and growth. The complex interactions between these phenomena require high fidelity simulations to be understood. 3d finite element simulations are accurate, but their computational cost limits the possible number of simulated cycles. We propose a cyclic finite element simulation in which the wheel and rail remain in contact throughout the simulation. It uses periodic boundary conditions, shadow elements, and model reductions. Compared to previous work, it is 25 times faster. The method is available as an open-source plugin to Abaqus, enabling other researchers to study rolling contact loading coupled with large plastic deformations.

Detection of Rail Geometry Irregularities Using Point Cloud Data from Terrestrial Laser Scanner (Study Case: Curve No. 106, Railroad between Cipatat-Tagogapu, Indonesia)

Geometry railroad irregularities can disrupt safety of the train that passes through it and the comfort of train users. In geometric inspection of rail, it requires reliable accuracy from survey data. Terrestrial Laser Scanner (TLS) offers the advantage of obtaining accurate measurements of objects or 3D model. This study aims to examine irregularities of widening gauge and cant rail in curve no. 106, railroad between Station Cipatat – Station Tagogapu based on Minister of Transportation Regulation No. 60 of 2012. The 3D rail model from the point cloud TLS can be used to extract changes of the gauge and height differences with the help of cross- sections. Extraction of gauge and height differences is carried out per 1 meter and given numbering. The results of both gauge and height differences are adjusted to the type of track from the results of the design of the curve, then compared with the value of the standard widening gauge and cant based on the Minister of Transportation Regulation No. 60 of 2012. The result extraction of the rail gauge in curve no. 106, shows the highest irregularities of widening gauge on the gauge number 24 with deviation value +0,017 m. The results of obtaining height differences rail extraction at curve no. 106, shows the highest irregularities of rail cant on the height differences number 15 and 16 with deviation value +0,022 m.

Assessment and prediction of high speed railway bridge long-term deformation based on track geometry inspection big data

This paper proposes a low-cost, data-driven approach to assess and predict bridge deformation using track inspection big data, which is primarily used for assessing track conditions. Firstly, a Bridge Deformation Assessment model with a sophisticated signal processing process is introduced to manipulate track geometry inspection data for extracting bridge-related components. Secondly, a Bridge Dynamical Deformation index (BDD index) is defined to quantify bridge deformation based on track geometry inspection data. Thirdly, the Temperature-Time-Deformation model (TTD model) is established to describe bridge deformation with respect to ambient temperature and length of service time of the bridge. Three types of TTD equations are proposed, including exponential-, hyperbolic- and linear-TTD equations. Fourthly, a track geometry inspection dataset over 2.6 years involving 563 bridge spans is applied as a case study. It is found that the BDD index changes with ambient temperature by 0.02 mm/°C on average, and increases with time by 0.2 mm/year during the 2.6-year period. Furthermore, a prediction on the amount of increase of the BDD index over the following 3 years is given with a 95% confidence level. It is expected that BDD index will increase by 0.5 mm in 2 years and 0.7 mm in 3 years according to the TTD model. Finally, the model uncertainty is discussed from data aspect and model aspect. The methods in this paper are of reference value for research topics on bridge condition evolution, rail geometry degradation and prediction-based infrastructure maintenance.

Estimating the wheel lateral position of a mechatronic railway running gear with nonlinear wheel–rail geometry

The “Next Generation Train” (NGT) is a double-deck high speed train concept in light-weight design that has been established as a technical and project framework in which the German Aerospace Center gathers its long-term railway vehicle research. To reduce wheel and rail wear and to enhance the passenger capacity, a mechatronic running gear with independently rotating wheels (IRW) is a key vehicle component under research. This running gear requires an advanced control of the lateral dynamics in order to fully exploit its potential in minimizing wear and noise, but this relies on information on its lateral position relative to the track. In daily railway operation it is difficult to directly measure this displacement of the wheel-pair. However, according to previous work it is possible to design an appropriate observer to estimate the lateral position, but its estimation accuracy highly depends on the chosen sensor configuration. Nevertheless, it was shown that the lateral dynamics of the running were not completely reproduced by the system description especially at suddenly changing directions in the movement of the IRW. In this work the system description is complemented by a nonlinear description of the wheel–rail geometry. Therefore, an observability analysis and an observer synthesis to estimate the lateral position for the nonlinear system of the 1:5 scaled hardware running gear is carried out. For validation purposes an extended Kalman filter with the U-D formalism is implemented at the real-time environment of the testbed and the estimation accuracy of the observer configurations is compared.

Matrix coupled model for the vehicle–track interaction analysis featured to the railway crossing

This paper presents a matrix coupled model for the vehicle–track interaction analysis with the crossing panel taken into account. In this model, the wheel–rail contact is assumed to be elastic and solved by the mathematical matrix formulations. Specifically, the determination of the two-point contact during the transition of the wheel load in the crossing panel is demonstrated. To improve the efficiency while ensuring the accuracy in the simulation, a time step size varying solution is applied in the model. The performance of the crossing is validated using field measurement results and simulation results from other numerical methods. The comparable results proved that the model is capable to catch the main features of the wheel–rail interaction in the crossing panel. Moreover, the effect of track irregularities on the vehicle–track interaction is analysed. The simulation results indicate that track irregularities mainly affect wheel–rail interaction in the regular track. In the crossing panel, the variation of the rail geometry plays a dominant role in the wheel–crossing interaction rather than the track irregularity. This study contributes to the perfection of the current model for the vehicle–track interaction analysis and will help to provide more comprehensive guidance for the design, construction and maintenance of the railway track.