Rail Web Research Articles

Simulation analysis of high-speed turnout point rail switching force considering influence of external locking device

This study simulates the complete switching process of a turnout and presents an accurate method for calculating the turnout switching force. By establishing an analysis model for the turnout switching of high-speed turnout elastic flexible single-leg point rail No.18 while considering the effects of external locking devices, the actual switching force time-history curve is obtained. Simultaneously, the model is validated with experimental data from the field. Based on this model, the effects of different factors on the switching force of the point rail are calculated and analyzed. The research results show that the external locking device optimizes the stress state of the locking lever, and the switching force acting on the locking lever is much smaller than that on the point rail web. Foreign matter clearly increases the switching force, which is not conducive to the locking of the point rail. When the foreign matter size reaches 3 mm, the switching force of the point rail increases sharply, which causes the switching force to exceed the limit. Overall, the point rail switching force is proportional to the start time difference of each traction point; therefore, the maximum action time difference should be controlled within 0.7 s.

Determination of temperature stresses in CWR based on measured rail surface temperatures

The main aim of conducted research is determination of temperature stresses due to the uneven temperature distribution in CWR. This paper presents a methodology for determination of temperature stresses in CWR based on (1) measurement system developed by the authors for measurement of rail surface temperatures, and (2) coupled transient thermal-stress analysis for simulation of rail temperature field and corresponding stresses. The main advantages of the proposed methodology are high sensitivity to the small temperature variations, taking into account the effect of thermal inertia, as well as measurement of single input parameter - rail surface temperature. The obtained experimental results showed lower rail temperatures in sleeper zones and rail foot along CWR, which emphasize the effect of heat transfer between rail and sleeper, as well as rail foot and ballast. These effects of heat transfer directly influence the decrease of temperature stresses in the mentioned zones of CWR. The maximum values of simulated temperature stresses are up to 16% less in the centre of gravity of railhead, up to 9.8% less in the centre of gravity of rail foot, and up to 0.2% less in the centre of gravity of rail web, compared to the common engineering calculation. In addition, the maximum value of simulated temperature force, based on temperature stresses in the rail cross-section, was up to 5.3% less than the value obtained in the common engineering calculation.

Deep Learning-Based Acoustic Emission Scheme for Nondestructive Localization of Cracks in Train Rails under a Load.

This research proposes a nondestructive single-sensor acoustic emission (AE) scheme for the detection and localization of cracks in steel rail under loads. In the operation, AE signals were captured by the AE sensor and converted into digital signal data by AE data acquisition module. The digital data were denoised to remove ambient and wheel/rail contact noises, and the denoised data were processed and classified to localize cracks in the steel rail using a deep learning algorithmic model. The AE signals of pencil lead break at the head, web, and foot of steel rail were used to train and test the algorithmic model. In training and testing the algorithm, the AE signals were divided into two groupings (150 and 300 AE signals) and the classification accuracy compared. The deep learning-based AE scheme was also implemented onsite to detect cracks in the steel rail. The total accuracy (average F1 score) under the first and second groupings were 86.6% and 96.6%, and that of the onsite experiment was 77.33%. The novelty of this research lies in the use of a single AE sensor and AE signal-based deep learning algorithm to efficiently detect and localize cracks in the steel rail, unlike existing AE crack-localization technology that relies on two or more sensors and human interpretation.

Extraction of Least‐Dispersive Ultrasonic Guided Wave Mode in Rail Track Based on Floquet‐Bloch Theory

Ultrasonic guided wave (UGW) has shown great potential in the field of structural health monitoring of rail tracks due to its long‐range capability and full cross section coverage. However, the practical application of UGW has been hindered by the complicated signal interpretation because of the natures of multiple modes and dispersion. Therefore, it is desirable that the effective UGW modes with high excitability and least dispersion can be identified and extracted for practical applications. In this paper, a numerical study on the guided wave propagation was carried out on a standard rail with 56E1 profile. Firstly, Floquet‐Bloch theory was applied to obtain the dispersion curves of guided wave in a rail. Then, a 3D FE model was built to investigate the UGW propagation along the rail within the frequency range of 0–120 kHz. Wavenumber‐frequency analysis method was applied to decompose and identify the propagating UGW modes. With a carefully designed 2D bandpass filter, a specific mode W0 was extracted in the wavenumber‐frequency domain. Finally, a frequency band sweep technique was also proposed to get the optimal frequency band to achieve a pure and least‐dispersive UGW mode along the rail web. The proposed method provides an effective way to extract efficient UGW modes to assess the integrity of the rail track, as well as other waveguides with complex geometry.

Status of nondestructive control of transport function metal products at JSC EVRAZ NTMK

Achievements in the area of automated ultrasonic control of quality of rails, solid-rolled wheels and tyres, wheels magnetic powder crack detection, carried out at JSC EVRAZ NTMK. The 100% nondestructive control is accomplished by automated control in series at two ultrasonic facilities RWI-01 and four facilities УМКК-1 of magnetic powder control, installed into the exit control line in the wheel-tyre shop. Diagram of location, converters displacement and control operations in the process of control at the facility RWI-01 presented, as well as the structural diagram of the facility УМКК-1. The automated ultrasonic control of rough tyres is made in the tyres control line of the wheel-tyre shop at the facility УКБ-1Д. The facility enables to control internal defects of tyres in radial, axis and circular directions of radiation. Possibilities of the facility УКБ-1Д software were shown. Nondestructive control of railway rails is made at two facilities, comprising the automated control line of the rail and structural shop. The УКР-64Э facility of automated ultrasonic rails control is intended to reveal defects in the area of head, web and middle part of rail foot by pulse echo-method with a immersion acoustic contact. The diagram of rail P65 at the facility УКР-64Э control presented. To reveal defects of the macrostructure in the area of rail head and web by mirror-shadow method, an ultrasonic noncontact electromagnetic-acoustic facility is used. It was noted, that implementation of the 100% nondestructive control into the technology of rolled stuff production enabled to increase the quality of products supplied to customers and to increase their competiveness.

A new wayside method for measuring and evaluating wheel-rail contact forces and positions

Wheel-rail contact forces affect the safety, stability, economy and smooth running of the railway system. Measuring these forces and their positions remains a challenge due to the coupling interference of strain signals under multi-loading scenarios. This paper proposes a new wayside method to measure the magnitudes and positions of the lateral and vertical contact forces. Theoretical formulations for the contact forces and their positions with respect to the vertical strain sum and difference at rail web sides, are derived by the results of finite element analysis (FEA). A subtle strain gauge configuration is designed to measure the sum and difference of strains precisely. The robustness of the formulas is confirmed through extra FEA and the proposed method is validated by laboratory tests. The developed method provides an accurate and economic option for monitoring the wheel-rail contact status.

Residual stresses in thermite welded rails: significance of additional forging

The aluminothermic welding (ATW) process is the most commonly used welding process for welding rails (track) in the field. The large amount of weld metal added in the ATW process may result in a wide uneven surface zone on the rail head, which may, in rare cases, lead to irregularities in wear and plastic deformation due to high dynamic wheel-rail forces as wheels pass. The present paper studies the introduction of additional forging to the ATW process, intended to reduce the width of the zone affected by the heat input, while not creating a more detrimental residual stress field. Simulations using a novel thermo-mechanical FE model of the ATW process show that addition of a forging pressure leads to a somewhat smaller width of the zone affected by heat. This is also found in a metallurgical examination, showing that this zone (weld metal and heat-affected zone) is fully pearlitic. Only marginal differences are found in the residual stress field when additional forging is applied. In both cases, large tensile residual stresses are found in the rail web at the weld. Additional forging may increase the risk of hot cracking due to an increase in plastic strains within the welded area.

Examination of Rail Dampers with Respect to Noise and Vibration Mitigation

Nowadays there are more and more possibilities to mitigate noise and vibration emitted by railway transport to the lower levels. Among them, rail dampers with highly viscous properties placed on the rail web, fixed with adhesives or other methods, appeared as a new element in the railway superstructure. The elements are applied to reduce noise and vibration by transforming the vibration energy of the rail web into heat, through their large internal friction. Many companies produce rail web elements and apply them with success abroad. Domestic manufacturers have already appeared in Hungary; however, the installation of these elements is still very limited. This publication is intended to introduce the rail dampers and to demonstrate their efficiency through laboratory and field measurements. Experimental modal analysis was used during the laboratory test to determine the eigenfrequencies, the damping factors and the mode shapes of an experimental rail section, thus analyzing the vibration damping and noise reduction effect of the elements. Field measurements were also carried out at a segment installed with rail web elements in Hungary and its vicinity, under standardized conditions. By averaging measured noise level values for various types of trains, comparable noise reduction of the investigated rail web element can be achieved. The laboratory and field test results confirmed that the rail web elements can be suitable for rolling noise reduction and vibration damping in most of the cases. The results of the measurements provide guidance and information for future development of the elements.

Correlation between Rail Vibration and Sound Radiation Using a Hammer Impact

When the track structure is subject to certain excitation, the vibration characteristics and sound radiation characteristics will show certain correlation with each other. However, the study on finding the direct relationship between rail vibration and radiated sound is very limited. In this paper, the correlation between the rail vibration and radiated sound pressure under a hammer impact was investigated with a full-scale track slab. The rail acceleration, rail surface sound pressure and radiated sound pressure nearby at the rail web and rail foot were measured and analyzed in frequency domain. The transfer function, coherence function were obtained to reveal the relevance between each pair of input and output signals. Finally, by choosing rail vibration acceleration and surface sound pressure as input excitation and choosing the surface sound pressure and the sound pressure in near field as output response successively, the transfer function and the transmission loss for each pair of input and output were analyzed and compared to reveal the signal transmission in different frequency ranges.

Dynamics of Rolling Stock Wheels and Track Interaction in Areas of Welded Rail Joints Crush

Finite element models of a rail crushed in a welded joint area and fixed on an elastic damping foundation and a car wheel have been developed. An algorithm has been developed to calculate quasistatic and impact forces during a wheel rolling at different speeds. Experimental studies have been carried out to determine vertical forces in the crushed area of the welded joint at a depth of 1.8 mm using the strain measurement method on the rail web neutral axis.

Influence of welding on microstructure and strength of rail steel

In this study, metallurgical and mechanical aspects of cold flash butt welded rail joints were investigated. The relationship between the material characteristics and the distance to the fusion line were evaluated. Significant changes observed in grain size as it ranges 2–8 according to ASTM E 112. Hardness tests conducted and the average results of the rail head, web, and foot were recorded. According to the results, three different zones were identified including the fusion line, recrystallization zone, and transition areas. Tensile properties and strength characteristics have been investigated for the specified zones separately. Obtained experimental values were used as input parameters for the developed finite element model (FEM) to calculate stress distribution. The welded rail was subjected to realistic wheel load and stress distributions in weld were evaluated. The developed model has also been validated by comparing the theoretically obtained stress values with the experimental ones under various loading conditions.

On the fatigue improvement of railways superstructure components due to cold expansion – Part I: Experimental analysis

The fatigue strength improvement of materials and structures has always been the subject of studies, as a consequence of the rapid development of technologies and strictive safety requirements. In the railway field the fatigue resistance problem is thoroughly studied due to high transportation safety standard. Fatigue cracking is a major issue, in particular at rail-end-bolt holes. Cold Expansion is a common technique to induce beneficial residual compressive stresses around the holes, with the aim to improve the fatigue life of the rail. This paper is the first of a two part-series dealing with the study of the residual stress-strain field induced by the cold expansion process around rail-end-bolt holes. In Part I of this series, a contribution to better understanding the whole strain field distribution arising around rail-end-bolt holes during and after cold expansion is presented. Strains were experimentally measured using both electrical strain gauges and 2D-Digital Image Correlation. Contrary to common literature, strain-time history during the entire cold expansion process was investigated, in order to capture the highly non-linear elasto-plastic response of the material; the results of this study has been used in Part II of this series for the validation of the finite element model described there. The cold expansion process was applied to three rail holes, having equal nominal diameter. At first, the experimental results concerning each expanded hole are analysed. Then, all the results are compared, in order to evaluate the repeatability: - of the measurements; - of the Cold Expansion process; - of the adopted experimental technique, and, above all, to extrapolate the distribution of the hoop and radial residual strains as a function of the distance from the hole edge. At the end, results obtained by strain gauges and 2D-Digital Image Correlation are compared: a good agreement is found on the central flat surface of the rail web, which guarantees the availability of a robust and valuable highly non-linear reference result that has been used for the validation of the finite element model presented in Part II of this series.

Wireless Localization of Spallings in Switch-Rails With Guided Waves Based on a Time–Frequency Method

Guided waves have been studied for monitoring defects on switch-rails. However, few researchers study monitoring of spallings. Previous studies on switch-rail damage detection are not suitable for this kind of damage at the edge of the rail web. In addition, wired configurations have the challenges of power supply and more cost. This paper proposes a time-frequency analysis based algorithm that is used to locate spallings. The algorithm is verified through an improved wireless based structural health monitoring (SHM) platform. The excitation frequency of 108 kHz is chosen as a compromise between larger wave velocity differences and smaller detectable damage sizes. A total of 4 piezoelectric (PZT) devices make up one actuator-sensor array. 2 PZT devices are placed at 2 sides of the rail web and both of them have the same excitation direction. The other 2 devices are mounted at the top of the rail web to measure spalling induced waves according to the cloud charts. The arrival time, frequency, and wave velocity features of the main modes in transmission and reflection waves are extracted. Then these parameters are substituted in the proposed algorithm to predict the spalling location. Simulation and epoxy bonding based experimental results show that the proposed method can identify a 15 mm length spalling at different locations. Finally, attention is paid to the mode identification errors that influence spalling localization. The effects of curvature on guided waves in switch-rails are analyzed and considered to be the cause of the errors.

Rail foot flaw detection based on a laser induced ultrasonic guided wave method

With the advancements in Railway Engineering in non-destructive testing technologies, a system for the fast detection of rail flaws at earliest stage is in huge demand. Such a system could result in savings in maintenance and would have less operational impact. Most of the research work in this area has been carried out for the defects in rail head and web, while defects in rail foot, which are difficult to access are responsible for derailments and accidents. This research work is focusing on detecting rail foot flaws using non-destructive, non-contact laser induced ultrasonic guided wave-based technique. This paper presents a conceptual technique based on finite element simulations of the propagation of laser induced ultrasonic guided waves to detect cracks in the rail foot. The simulations are performed at different frequencies and varying sensor positions to identify the best suited frequency and sensor location on locomotive for reliable defect detection.

An Ultrasonic Guided Wave Mode Selection and Excitation Method in Rail Defect Detection

Different guided wave mode has different sensitivity to the defects of rail head, rail web and rail base in the detection of rail defects using ultrasonic guided wave. A novel guided wave mode selection and excitation method is proposed, which is effective for detection and positioning of the three parts of rail defects. Firstly, the mode shape data in a CHN60 rail is obtained at the frequency of 35 kHz based on SAFE method. The guided wave modes are selected, combining the strain energy distribution diagrams with the phase velocity dispersion curves of modes, which are sensitive to the defects of the rail head, rail web and rail base. Then, the optimal excitation direction and excitation node of the modes are calculated with the mode shape matrix. Phase control and time delay technology are employed to achieve the expected modes enhancement and interferential modes suppression. Finally, ANSYS is used to excite the specific modes and detect defects in different rail parts to validate the proposed methods. The results show that the expected modes are well acquired. The selected specific modes are sensitive to the defects of different positions and the positioning error is small enough for the maintenance staff to accept.

Rail defect inspection based on coupled structural–acoustic analysis

The inspection of rail defects is of importance in high-speed railway operation and maintenance. As a highly efficient method for both nondestructive testing and structural health monitoring of the rail, ultrasonic guided waves (UGWs) inspection provide increased sensitivity to smaller defects. These advantages can be fully exploited only if the complexities of UGWs propagation between the medium of air and rail are unveiled and managed for the given inspection method. The development and validation of modeling procedure for the rail based on coupled structural–acoustic model is presented in this paper. Acoustic–structure interaction between air and rail is simulated based on COMSOL Multiphysics software. The transient response and natural characteristics of UGWs in the rail was computed and predicted. Moreover, the displacement distribution of UGWs in the defective rail and nondefective rail are analyzed both in time and frequency domain. A feasible method for detecting small defects in the rail is proposed in the paper. The results indicated that a defect of 8 mm in rail head can be inspected effectively using UGWs with frequencies of 40 kHz and above. And for small defects in rail web, the X-crystallographic direction ultrasonic transducer should be chosen for inspection.

A new strain gauge configuration on the rail web to decouple the wheel–rail lateral contact force from wayside measurement

The simultaneous presence of bending moments and torques produced by the lateral and vertical contact forces between the wheel and the rail generates a complex strain state on the rail surface, which makes it difficult to identify the strain signals produced purely from the lateral contact force. In this study, a new strain gauge configuration is proposed to decouple strain signals of the wheel–rail lateral contact force from wayside measurements by analyzing the bending strains on the rail web using a full Wheatstone bridge. For this purpose, a finite element modeling of the wheel–rail contact is performed to analyze the bending strains on the rail web and to optimize two instrumented sections for eight electric resistance strain gauges. Laboratory testing is also used to examine the installation scheme of the strain gauges at the two optimal instrumented sections. A good agreement is observed between the experimental data and the simulation results. Strain signals are evenly distributed for about 10 cm in the middle region between the two optimal instrumented sections and only account for the lateral contact force.

Effect of Track Configuration and Loading Conditions on Vertical Wheel Load Measurements using the Differential Shear Approach

Measurement of vertical wheel loads on railroad tracks using strain gauges mounted on the rail web is common practice. This measurement approach makes use of the differential shear concept that the difference in shear force between two points along a beam equals the magnitude of the vertical load applied between those two locations. Although the applicability of this concept is easy to verify for simple beams, its validity for field applications under different track configurations including support and loading conditions is relatively unexplored. Findings are presented from an ongoing research effort that has utilized numerical models to assess the effects of different track and loading configurations on vertical wheel load measurements using the differential shear approach. The underlying theory behind this measurement approach is first introduced, and different scenarios are compared using a simple one-dimensional model. This is followed by detailed analysis of the effects of different vertical, lateral, and axial loading combinations on the measured shear strain values. Finally, a three-dimensional finite element model is used to study the dependence of the measured wheel loads and calibration approaches on track support conditions. Findings from the analyses clearly establish the applicability of this measurement approach across different scenarios observed in railroad tracks.

Determining transverse ten-sions in the rail web depending on dynamic loadings at approaches to bridges

Determining transverse ten-sions in the rail web depending on dynamic loadings at approaches to bridges

Understanding track substructure behavior: Field instrumentation data analysis and development of numerical models

Abstract Numerous studies have targeted using numerical modeling, field instrumentation, or combinations of both to gain insight into track substructure behavior under loading. In-depth understanding of track substructure behavior serving both passenger and freight trains is critical to developing suitable design and maintenance/rehabilitation methods to ensure adequate performance under loading. This manuscript presents findings from a recently completed study involving advanced instrumentation and numerical modeling to investigate track substructure-related issues at several problematic railroad bridge approaches in the United States. Multi-Depth Deflectometers (MDDs) were installed to measure transient as well as plastic deformations experienced by track substructure layers under loading. Strain gauges were installed on the rail web to measure the vertical wheel loads applied during train passage. Data from the field instrumentation was used to make inferences regarding the relative contributions of different substructure layers towards the differential movement problem. A 3-D Finite Element (FE) model was developed to further understand the behavior of the instrumented locations, and was calibrated using the field instrumentation data. An elastic layered track analysis program, GEOTRACK, was first used to iteratively backcalculate individual track substructure layer moduli from the field measurements; these backcalculated modulus values were subsequently used in the FE model to predict track response under transient loading conditions. Modulus values estimated for the ballast layer were found to be significantly affected by the presence of gaps at the tie-ballast interface at track transitions. Once validated, the model was further modified to match transient displacement results acquired in the field using a quasi-static moving load approach. Good agreement was found between the model predictions and field instrumentation results. Development of advanced numerical models augmented by field instrumentation data can facilitate the design and maintenance of well-performing track structures.