Rail Head Research Articles

Ultrasonic SH guided wave detection of the defects of switch rails with 3D finite element method

A switch rail is an important part of the high-speed railway system, but it is highly susceptible to defects during service, which threat traffic safety. A switch rail has an asymmetric variable cross-section structure, which makes it challenging to detect its defects with ultrasonic testing. In this study, the finite element model of switch rails and the ultrasonic SH guided wave detection of groove defects were explored. The three-dimensional finite element model of switch rails with the same sizes used under working conditions was established. Furthermore, the influences of grid division method, switch mechanism setting method, and root end variable cross-section grid type on guided wave propagation in the model were analyzed in detail. The switch rail model was experimentally validated. The ultrasonic SH guided wave detection of the defects at the rail head and rail bottom was successfully realized and the echo signals from other special structures of switch rail were also obtained. The finite element model calibrated with experimental results could be used to simulate guided wave detection at any location with any defect. The calibrated model could optimize the switch rail guided wave detection scheme and guide signal identification. The study provides an important basis for the inspection and monitoring of switch rails.

Analysis of the Relationship between Rail Cant and Track Gauge Based on the Data Obtained by Track Recording Cars

The increase in the service life of track superstructure has always been an important task since this allows reduction in the cost of repairs and current maintenance of the track.The objective of the work is to determine the mutual influence of the rail cant and the track gauge based on the results of measurements carried out by track recording cars, as well as their impact on the stress-strain state of the rail. The analysis was based on statistical and the finite element methods. Using statistical methods, it was determined that the rail cant and track gauge values do not have a normal distribution and have a weak feedback. The reasons were explained in the conclusions.To determine with the finite element method contact stresses in the rail head on the track sections available in the sample, with different combinations of rail cant and track gauge, a model with full geometric similarity was developed.The results obtained from the calculations demonstrate that the deviation of the cant within the range from 1/15 to 1/30 leads to an increase in stresses by more than 20 %, while changing the track gauge has a weak effect on the stress-strain state of the rail head. The maximum increase in contact stresses, at the analysed section, was 97 %, with a cant of 1/990 and a track gauge of 1526 mm.The growth of contact stresses leads to the formation of fatigue cracks and, as a consequence, to the defects and then to replacement of the rail. To increase the service life of the rails, it is recommended to monitor the condition of fasteners and compliance with the technology of current maintenance works, as well as to reconsider tolerance of the deviation of the cant both upward and downward.

Studying the transfer mechanisms of water based top-of-rail products in a wheel/rail interaction

The railway industry uses top-of-rail products to control and manage the friction in the wheel/rail interface to help ensure efficient train operations and reduce wheel and rail damage. A product is typically applied from a wayside applicator that pumps a puddle onto the rail head where a passing wheel will pick it up and then transfer it down the track. The aim of this study was to study the transfer mechanisms of water-based top-of-rail friction modifiers (TOR-FMs) and how they are linked to the friction conditions in the wheel/rail interface. The transfer mechanisms were split into three parts: pick-up, carry-on and consumption. Pick-up looks at how the product transfers from the puddle on the rail to a wheel tread, whereas the carry-on mechanism relates to the product transfer back to the wheel. Consumption focuses on the removal rate of the product layer from the wheel or rail. A full-scale rig and twin disc machine were chosen to perform the tests because each rig could give different insights into understanding the product transfer mechanisms. Two products were tested of similar formulation. Results show that there are differences in the transfer and friction between the two products despite them being relatively similar. The test methods developed can clearly resolve differences between varying product types, which could be useful for product development studies or approvals work. The outcomes could also be used to develop a model of transfer/consumption.

Effect of rail cant on stress distribution

The rail cant is an important geometry parameter and is commonly monitored to ensure railway safety and comfort conditions. Understanding the influence of cant variation on the performance of railway components is extremely important to define the tolerance limits of the track and adequacy of maintenance plans. There are numerous rail cant patterns on railways, 1:40, 1:30, 1:20. However, the optimal rail cant to reduce the stress and wear of rail head not been extensively studied. This work performs an analysis of the effect of the rail cant on the rail head stress distribution. To investigate stress and strain in rail head, a Finite Element Model with Ansys software was used. For the analysis was considered a 136RE rail, axle load of 32 ton and AAR-1B wheel profile. The rail cant was varied in 0, 1:20 and 1:40. The results show that the stress in rail and wheel increases with the rail cant. The maximum stress occurred in the condition with rail cant of 1:20. The variation of cant from 0 to 1:20 results in a decrease of approximately 9% in maximum stress, ranging from 947 MPa to 867 MPa. The wheel/rail contact in cant zero condition occurred close to the transition of the wheel tread and the beginning of flange root, resulting in a dynamic instability in the wheelset. In addition to higher contact stress, increases the propensity for the hutting phenomenon, which can accelerate rail and wheel wear

Experimental determination of vibration conductivity by rocket sled structural elements in high-speed track tests of aircraft equipment

The development of new ballistic-type aircraft is characterized primarily by improved aerodynamic characteristics and higher speed limits. Ground track testing of aviation and rocket technology is a stage whose task is to confirm the efficiency and effectiveness of new developments. Track tests make it possible to simulate real loads, they are simpler and much cheaper than flight tests. Experimental installation "Rocket rail track 3500" of Scientific Test Range of Aviation Systems named after L. K. Safronov is constantly being upgraded in order to conduct track tests of products at a speed greater than 3M. The experimental setup includes a two-rail track, made on a special foundation, which excludes unacceptable rail deflection with a mass of up to 3000 kg. The rail track has an acceleration section with an angle of attack 2500 m long and a deceleration section. A tray filled with water is made on the braking section between the track rails. It is designed for hydrodynamic braking to a complete stop of the rocket sled with stored equipment. The movable rocket track sled is made of a massive steel plate to which three cross beams are welded. The front and rear beams end with axles on which sliding supports are pivotally mounted. On the rear and middle beams there are lodgements for fastening rocket engines of solid fuel. Depending on the required test speed, from one to five motors can be placed on the cradles. The test object is usually mounted on the front and middle beams along the axis of the sled and fixed in a cantilever, with the head part extended forward. The design of the supports - shoes is made to encircle the rail head in such a way that it provides sliding contact along the upper plane of the rail head, and in the event of a lifting force exceeding the weight of the sled at high speeds, it keeps the structure from free flight by contacting the lower surface of the rail head. Track high-speed tests of special equipment objects are always accompanied by intense vibration and shock effects of structural elements. Due to the desire to conduct track testing of products at a faster rate, it becomes necessary to reduce the level of dynamic loads and eliminate resonant interactions. The article presents an algorithm and methodology! for statistical processing of random signals of three-axis vibration acceleration sensors installed on the shoes of the rocket track sled and on the fairing of the test object. Due to the placement of registration data storage devices on the sled, experimental vibration data were stored when testing the product at a speed of more than IM. The autocorrelation functions of the signals of vibration accelerations of sensors placed on various elements of the rocket sled, the functions of mutual correlation of the corresponding signals, the density of the amplitude spectra, the density of the power spectra and the transfer functions that characterize the dynamic conductivity of vibrations from the shoes sliding along the rail guides to the test object were determined.

Algorithm for simulation of vibration effects during track tests of aircraft and missile technology

Track high-speed ground tests of products of aviation and rocket technology make it possible to experimentally confirm the aerodynamic and strength characteristics of new aircraft or their components. Experimental installation Rocket rail track 3500, located on the territory of the Federal State Enterprise Scientific Test Range of Aviation Systems named after L. K. Safronov (FKP GkNIPAS named after L.K. Safronov), is a complex hydro-gas-dynamic engineering structure. The main part of this installation is a rail track placed on a special concrete base, which is based on piles to eliminate the influence of viscoelastic ground vibrations. Between the rails, taking into account the profile of the track, a hydrodynamic multi-level tray is made, designed for hydraulic braking of the stored track sled. The movable rocket track sled rests on slip shoes covering the top rail head. On the track sleigh, solid propellant rocket engines and the object of study are placed. The article describes the approach to the calculation of determining the dynamic loads acting on the elastic structure of the track sled with the test object. The design is represented by a schematic spatial model of elastic beams in the form of rods, plates, pipes with equivalent mass and stiffness, interconnected by elastic links. A model of non-stationary aerodynamic forces is formulated taking into account viscosity for numerical calculations of the flow around the sled structure. Programs have been developed and modeling of the aerodynamic interaction in the case of a supersonic air flow around the structure of a rocket sled has been carried out. The results of vibrational accelerations of elements, components of the sled and the test object, depending on the speed of movement, were obtained by calculation. The forms and frequencies of natural free vibrations of the sled structure are determined, and the densities of the vibration acceleration spectra are calculated.

Portray rail head surface crack 3D contour through image analysis and morphology reconstruction

Rail head spalling and fractures are strongly correlated with fatigue crack propagation. Fatigue cracks typically form along evolving surfaces, but their propagation paths are not accurately described by idealized semi-elliptical crack morphology. This study aims to capture the true three-dimensional shape of fatigue cracks during initiation and propagation. New mathematical and physical models, based on reconstructed 3D cracks, are proposed to predict rail crack propagation at various service stages. The analysis reveals that the crack propagation path in the 2D lateral rail section approximates a quadratic parabola or circular curve, and the 3D crack morphology is similar to a partial spherical surface with a curvature radius of approximately 18.5 mm. The three-dimensional crack morphology remains consistent within a small rail range. The reconstruction model proposed in this study can predict internal crack propagation on the rail head surface, assisting in track inspection, maintenance, and repair.

Quantitative detection of rail head internal hole defects based on laser ultrasonic bulk wave and optimized variational mode decomposition algorithm

This paper proposes a quantitative rail head internal defect detection method combining mode conversion and time-of-flight based on the theory of laser ultrasonic bulk wave scattering and diffraction. The interaction between laser ultrasonic bulk wave and rail internal hole defects is modeled using finite element simulation, and the modal conversion of bulk wave encountered defects is investigated. The feasibility of localization and the quantitative method are both confirmed. Simultaneously, an Optimized Variational Modal Decomposition (OP-VMD) method is proposed to solve the problem of low SNR of bulkwave signals and to facilitate multi-mode wave discrimination. This method can extract the defect diffraction Shear Wave (S) signal from complex ultrasonic signals. Finally, experiments are performed on the defects of artificial internal holes in rail heads with varying burial depths and sizes. The experimental results show that the method can not only detect but also quantify the defects of internal holes in rail heads. The location relative errors are within 3%, and the quantitative relative errors are within 7%.

Мокрій Т. Ф., Малишева І. Ю. , Лапіна Л. Г., Пасічник С. С. Взаємодія з рейками коліс пасажирського вагона з новим профілем ободу ІТМ-73EP в криволі-нійних ділянках колії

Speeding up the integration of Ukraine into the European railway transportation is an important task in the current development of the Ukrainian railway transport. Currently, the most effective way to travel across borders between countries with different track gauges is the use of gauge-changeable wheelsets. Continuous traffic on the Ukrainian (1520 mm gauge) and European (1435 mm gauge) railways calls not only for gauge changing facilities, but also for the compatibility of the wheel-rail contact pair on both railways: R65 rails and a cant of 1/20 in Ukraine and UIC60 rails and a cant of 1/40 in Europe. At the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, a new wear-resistant wheel profile, ITM-73ER, was proposed. As predicted, its use in passenger cars will offer dynamic stability and a high dynamic performance throughout the range of operating speeds on the Ukrainian and European railways and acceptable indices of wheel – unworn rail interaction on both railways. In service, the shapes of the wheel and rail contact surfaces change due to wear, especially in curves. Because the Ukrainian and European railways mostly use wheel and rail profiles of their own, the use of the new wheel profile may impair the wheel–rail interaction process, enhance wheel flange wear, and shorten the wheel life. The goal of this work is to study the effect of the in-service rail head shape change in curves of the Ukrainian and European railways on the wheel–rail interaction indices of a passenger car with ITM-73ER profile wheels. The head shapes of outer rails of the Ukrainian and European railways’ circular curves were predicted for a side flange wear changing from 0 to 8 mm in 2 mm increments. The calculations were made for two circular curves of radius 300 m with UIC60 rails and a cant of 1/40 (Europe) and R65 rails and a cant of 1/20 (Ukraine). To speed up the prediction, it was assumed that the curves were traveled by four-axle fully loaded freight cars, which maximizes the rail wear. The freight car wheels were assumed to be unworn and machined to the S1002 profile (for the European railways) and to the standard profile specified by the Ukrainian State Standard GOST 10791:2016 (for the Ukrainian railways). Using the computed head shapes of R65 and UIC60 rails differing in wear degree, a study was conducted into their effect on the wheel–rail pair strain and stress field and the dynamic indices of car–track interaction for passenger cars with ITM73-ER profile wheels negotiating a circular curve of radius 300 m. It was shown that the use of the ITM-73ER wheel profile in passenger cars will offer improved indices of car–track interaction, for worn rails too, both on the Ukrainian railways and in the combined operation on the Ukrainian and European railways.

Experimental and Numerical Visualisation of Subsurface Rail Deformation in a Full-Scale Wheel–Rail Test Rig

To tackle the problem of various types of rail damage, such as rolling contact fatigue (RCF) or wear, a profound knowledge of the occurring mechanisms is necessary. This paper presents a newly developed full-scale test rig experiment that involves inserting softer pins into the rail head. These tests help deepen our understanding of shear deformation in rail steels. Furthermore, a finite element (FE) simulation approach is introduced that can be related to the test rig experiments. With these experiments, in combination with the FE simulation, valuable information regarding the plastic deformation can be obtained. This methodology allows predictions regarding a rail’s material behaviour during cyclic wheel loading. Moreover, it enables an effective and rapid qualitative material assessment, reducing the costs of expensive and time-consuming experiments.

A Review of NDT Methods for Wheel Burn Detection on Rails.

Wheel burn can affect the wheel-rail contact state and ride quality. With long-term operation, it can cause rail head spalling or transverse cracking, which will lead to rail breakage. By analyzing the relevant literature on wheel burn, this paper reviews the characteristics, mechanism of formation, crack extension, and NDT methods of wheel burn. The results are as follows: Thermal-induced, plastic-deformation-induced, and thermomechanical-induced mechanisms have been proposed by researchers; among them, the thermomechanical-induced wheel burn mechanism is more probable and convincing. Initially, the wheel burns appear as an elliptical or strip-shaped white etching layer with or without deformation on the running surface of the rails. In the latter stages of development, this may cause cracks, spalling, etc. Magnetic Flux Leakage Testing, Magnetic Barkhausen Noise Testing, Eddy Current Testing, Acoustic Emission Testing, and Infrared Thermography Testing can identify the white etching layer, and surface and near-surface cracks. Automatic Visual Testing can detect the white etching layer, surface cracks, spalling, and indentation, but cannot detect the depth of rail defects. Axle Box Acceleration Measurement can be used to detect severe wheel burn with deformation.

Analysis of Traction Coefficient Subject to Rail Cleaning Effect Based on Tribomachine Measurements

The proper representation of friction contact conditions between each wheel and the rail is necessary to accurately model the behaviour of a heavy haul locomotive since friction conditions at the wheel-rail interface affect the locomotive’s dynamic performance under traction and braking conditions. In normal operations, a phenomenon commonly known as rail cleaning effect occurs. The rail cleaning effect causes increased friction coefficients between the following wheel treads and the rail head. The wheel-rail interaction causes the third body layer to be partly or wholly eliminated from the surfaces in contact and generates new layer. An experimental analysis of the changes in friction coefficients under simulated locomotive wheel-rail contact conditions, in terms of contact pressure and slip, is presented in this paper. For this study, data processing equations are presented to obtain the experimental traction coefficient and slip. Furthermore, the rail cleaning effect is examined under different slip conditions. The experiment shows the traction coefficient increases for a given number of cycles until reaching a steady value, demonstrating that the rail cleaning effect is measurable in various slip conditions on a twin disc machine.

Squat Detection and Estimation for Railway Switches and Crossings Utilising Unsupervised Machine Learning

Switches and crossings (S&Cs) are also known as turnouts or railway points. They are important assets in railway infrastructures and a defect in such a critical asset might lead to a long delay for the railway network and decrease the quality of service. A squat is a common rail head defect for S&Cs and needs to be detected and monitored as early as possible to avoid costly emergent maintenance activities and enhance both the reliability and availability of the railway system. Squats on the switchblade could even potentially cause the blade to break and cause a derailment. This study presented a method to collect and process vibration data at the point machine with accelerometers on three axes to extract useful features. The two most important features, the number of peaks and the total power, were found. Three different unsupervised machine learning algorithms were applied to cluster the data. The results showed that the presented method could provide promising features. The k-means and the agglomerative hierarchical clustering methods are suitable for this data set. The density-based spatial clustering of applications with noise (DBSCAN) encounters some challenges.

A rail defect detection system based on laser Doppler vibrometer measurements

This paper aims at introducing a non-contact rail damage detection system based on laser Doppler vibrometer (LDV) measurements. Specifically, the system consists of two LDVs mounted on a rail car, to record the waves induced on the rail head by random rail-wheel interaction forces.The developed damage detection framework associated with the system is based on a multivariate analysis that combines damage features which are based on the relative change in amplitude of the LDV signals that are caused by both reflected and transmitted waves. In this study, the damage detection system is introduced and validated through field tests which were carried out at the Transportation Technology Center (TTC) in Pueblo, CO. In these tests, a rail car installed with the damage detection system traveled over a track that consisted of a discontinuity in the rail (i.e., welded joint) at different speeds up to 48 km/h (30mph). Results show that the proposed system can identify the rail segment in which the propagating waves on the rail head are affected by the presence of the welded joint.

Power Calculation of Anti-Driveaway Crane Device from Eccentric and Wedge Mechanisms

To carry out a power calculation of the anti-driveaway device (AD) of lifting cranes operating in the open air, it is necessary to know the conditions that ensure their reliable stop and fixation on rails, as well as kinematic parameters, namely, the speed and acceleration of cranes when they move along the rails under the influence of the wind force. The considered AD for stopping cranes driven away by the force of the wind uses a tong gripper driven by an eccentric mechanism.The paper presents the calculation of the forces arising during the operation of the tong gripper, considering the possibilities of various types of friction on the contact surfaces both in the absence of lubrication and in its presence. The calculations of the eccentric mechanism as one of the fundamental mechanisms of the anti-driveaway crane device are presented in the paper. The stronger the wind force, the more due to the kinematic connection of the two mechanisms, when turning the eccentric mechanism, the pressure of the tong mechanism increases on the side faces of the head of the crane rail. The constructive solution of the AD excludes any actions of the personnel and makes it automatic.

TECHNOLOGY OF RESURFACING MN-STEELS USED TO MANUFACTURE RAILS

The track components that are the most heavily loaded from the axles of train units are the switch components and rail crossing parts. These parts can be refurbished by welding on suitable types of additional materials. Parts made of high-alloyed Mn-steel (Hadfield steels) need to meet specific conditions for their welding. For the experiment, ESAB OK Tubrodur 14.71 and ESAB OK Tubrodur 15.65 materials were used. The results show the feasibility of appropriate procedures under specific conditions due to the occurrence of metallurgical defects affecting the safety of operation on railway and tram lines. The aim of the experiment was to perform and assess the properties of two types of austenitic welds of different chemical composition on the rail head and rail grooves with the same welding parameters.

Analysis of ultrasonic nonlinearity for bolt hole crack detection in rail joints by wavelet packet decomposition

This paper proposes a crack detection method for rail joint screw holes based on the ultrasonic nonlinearity. Experimental and numerical studies are conducted to validate the performance of the proposed approach. The ultrasonic signals excited and received at the rail head are processed by spectral analysis and Wavelet Packet Decomposition (WPD). The third harmonic can be clearly observed from the spectrum analysis, which is supposed to be the nonlinearity of structures. Further, WPD is used to decompose the frequency components of the received signals. A damage index (DI) is defined based on the energy percentage of the energy in the WPD node containing the third harmonic with respect to the total energy of the received signal. It is found that the DI relating to the third harmonic increases with an approximately linear relationship when the crack grows bigger. It can provide a basis for the crack detection and quantification for the rail joint screw holes. A finite element model of the experimentally tested rail is also developed and numerical studies are conducted to verify the ultrasonic nonlinearity in the rail structure. Numerical results have the same trend with the experimental results, which verifies the effectiveness of the proposed method for crack detection in rail joints based on the high order ultrasonic nonlinear harmonics.

The effect of the wavelength of lateral track geometry irregularities on the response measurable by an instrumented freight wagon

Condition monitoring of railway track geometry using instrumented in-service vehicles has been the subject of extensive research aimed at replacing or enhancing the data provided by dedicated track recording vehicles. Lateral track irregularities present difficulties compared to vertical irregularities due to the lateral clearance between the wheel flanges and the rail head. Wheelsets don’t necessarily follow the lateral trajectory of the track. Simulations of a freight wagon with three-piece bogies negotiating both discrete and cyclic lateral track irregularities showed that the resulting lateral displacements were highly dependent on the wavelength of the irregularities. The wheel/rail profiles also had a significant effect whilst the effect of speed was relatively minor. These findings highlight the complexities of identifying exceedances of track geometry standards using only inertial sensors on instrumented freight wagons.

Dynamic Analysis of the High Speed Train–Track Spatial Nonlinear Coupling System Under Track Irregularity Excitation

Track irregularity is the main factor that affects the safety and comfort of high-speed railway. It is important to study the influence of the track irregularity on the safety service of high speed train–track coupling system. In this paper, a vehicle–track spatial nonlinear coupled system dynamics model is developed with FEM. The model includes vehicle subsystem and track subsystem, which are coupled by wheel–rail interface. The vehicle subsystem is a 31-DOF spatial vehicle model, and the track subsystem is a three-dimensional slab track model composed of the rail, rail pad and track slab. Considering wheel tread profile and rail head profile, the wheel–rail spatial contact geometry relationship is established, and the “Trace method” and the “Minimum distance method” are used to search for wheel–rail contact points. Considering the nonlinear contact between the wheel and the rail, a numerical approach is presented, where the “Trace method” is embedded into the algorithm for solving the vehicle–track nonlinear coupling dynamics equation by cross iteration, realizing searching the wheel–rail contact points and solving the vehicle–track nonlinear coupling equation simultaneously, which greatly improves the efficiency of numerical analysis. As application examples, the dynamic responses of a high speed train–track spatial nonlinear coupled system excited by the track V-shaped local profile irregularity and the track torsional irregularity are analyzed. The results show that the algorithm is effective in solving the vehicle–track spatial nonlinear coupled system dynamics problem, and the track irregularity has significant influence on the dynamic response of vehicle and track structure.

Orbital friction welding of steel bars – heat generation and process modelling

Welding of rails in the field is usually associated with a large heat input, which results in a large heat-affected zone (HAZ), which in turn may impair the welded rail head and decrease its service life. An innovative orbital friction welding (OFW) process with an intermediate eccentrically oscillating disk is proposed, and a demonstrator has been constructed. This enables welding of rails, which have a non-symmetric cross-sectional area and must be stationary during welding. The process is characterized by low heat input, creating a narrow HAZ, and low welding deformations. A thermo-mechanical finite element model is developed to determine suitable process parameters to create a narrow HAZ. A phenomenological model for heat generation during friction welding is developed for pearlitic rail steel with parameters calibrated from rotary friction welding experiments on pipes. The temperature dependence of the friction coefficient in the interface is established. Pilot tests with the demonstrator OFW machine on bars with a quadratic cross section showed that preheating will be required to guarantee a fully pearlitic weld zone. This was verified by the simulations of the thermo-mechanical finite element model.