Rail Head Research Articles

Mechanisms of hardening of heavy-loaded rails made of hypereutectoid steel during long-term operation

Using transmission electron microscopy methods, the structural-phase states and defective substructure were studied at distances of 0; 2 and 10 mm from the surface along the central axis and rounding radius of rails head fillet. Differentially hardened long rails of the DT400IK category made of hypereutectoid steel have been studied after operation on the Trans-Baikal Railway (passed tonnage equal to 234.7 million tons gross). It has been established that steel strength characteristics are determined by certain physical mechanisms. A qualitative assessment of the contributions from crystal lattice friction, solidsolution strengthening, strengthening of the pearlite component, incoherent cementite particles, grain boundaries and subboundaries, dislocation substructure and internal stress fields was carried out, and their hierarchy was established. A quantitative assessment of the additive yield strength of steel in different directions was carried out depending on the distance from the rolling surface. It is shown that the main mechanisms of strengthening are strengthening by incoherent particles, long-range stress fields and substructural strengthening. The additive yield strength on the fillet surface is significantly greater than on the rolling surface of the head along the central axis.

Application of Surface Ultrasonic Waves for Detection of Contact Fatigue Cracks in the Rail Surface

The integrity and durability of rails plays a key role in train safety. However, the interaction of the rail head surface with the wheels of the rolling stock leads to high damage to these areas. The surface of the rail head is subject to the greatest damage, in which fatigue cracks develop on the surface with subsequent development. Timely detection of fatigue cracks in the rolling surface is possible using the ultrasonic technique using surface waves. To do this, the work investigated the sensitivity of a surface ultrasonic wave to obstacles in the surface of rails in the form of extended grooves, notches of finite length and known depth, as well as real cracks. The studies were carried out using the pulse-echo method at frequencies of 1.25, 1.8, 2.5, 4 MHz. Research has shown that surface waves are sensitive to surface fatigue cracks. The amplitude of the reflected pulses depends on the wavelength and the depth of crack propagation. The influence of the distance to fatigue cracks and the orientation angle of the transducer relative to the rail axis on the sensitivity of the surface wave to these defects was also studied. The results obtained allow us to conclude that the use of surface ultrasonic waves makes it possible to detect fatigue cracks in the crack surface. Thus, the use of the pulse-echo technique and surface wave converters makes it possible to detect contact fatigue cracks in the rail head, which can be used to eliminate them in a timely manner. The determination of their depth by amplitude is influenced by many factors, which are difficult to take into account in real conditions.

An efficient numerical model for the sound radiation from a supported rail

In this work, the sound radiation of a supported rail is investigated using a numerical 2.5D Finite Element model that is coupled with a 2.5D Boundary Element model. The vibration of the track is modelled by coupling the infinite rail to an equivalent continuous double-layer support and is used as input for calculating the consequent sound radiation. An interpolation method that allows for a quick solution of the boundary element calculations is proposed and validated by comparison with an analytical solution, showing differences less than 0.1 dB. The assembled model is used for calculating the sound radiation from the rail in terms of sound power per unit squared force applied to the rail head in vertical and lateral directions for three different rail configurations. The transfer functions obtained can be used in rolling noise calculations. The proposed interpolation method allows calculations that are more than 100 times faster than the regular procedure for the case considered.

Long Short-Term Memory Autoencoder for Anomaly Detection in Rails Using Laser Doppler Vibrometer Measurements

Abstract This study presents an application of Long Short-Term Memory Autoencoder (LSTM AE) for the detection of broken rails based on laser Doppler Vibrometer (LDV) measurements. This work is part of an ongoing project aimed at developing a non-contact damage detection system using LDV measurements. The damage detection system consists of two laser Doppler vibrometers (LDV) mounted on a moving rail car to measure vibrations induced on the rail head. Field tests were carried out at the Transportation Technology Center (TTC) in Pueblo, CO, to collect the vibrational data. This study focused on the detection of broken rails. To simulate the reflected and transmitted waves induced by the broken rail, a welded joint was used. The data was collected from moving LDV measurements, in which the train was operating at three different speeds: 16km/h (10mph), 32km/h (20mph), and 48km/h (30mph). After obtaining the data, filtering and signal processing were applied to obtain the signal features in time and frequency domains. Next, correlation analysis and principal component analysis were carried out for feature selection and dimension reduction to determine the input used to train and test the LSTM AE model. In this study, the LSTM AE models were trained based on different data sets for anomaly detection. Consequently, an automatic anomaly detection approach for anomaly detection based on the LSTM AE model was evaluated. The results show that the LSTM AE model can efficiently detect the anomaly based on the selected features at three different speeds.

Finite element analyses of rail head cracks: Predicting direction and rate of rolling contact fatigue crack growth

A numerical framework in 3D for predicting crack growth direction and rate in a rail head is presented. An inclined semi-circular surface-breaking gauge corner crack with frictionless crack faces is incorporated into a 60E1 rail model. The investigated load scenarios are wheel–rail contact, rail bending, thermal loading, and combinations of these. The crack growth direction is predicted using an accumulative vector crack tip displacement criterion, and Paris-type equations are employed to estimate crack growth rates. Results are evaluated along the crack front for varying crack radii and crack plane inclinations. Under the combined load cases and in the presence of tractive forces, the crack is generally predicted to go deeper into the rail than under pure contact. Crack growth rates for the combined load cases are higher than (but still close to) that for pure contact. A tractive force will increase growth rates for smaller cracks, whereas a steeper (45°) inclination will decrease the growth rate under the studied conditions as compared to a shallower (25°) inclination. Results should be of use for rail maintenance planning where deeper cracks require more machining efforts.

Physics of hardening of the rolling surface of rail head from hypereutectoid steel after operation

In Russia, with its extensive railway system, for more than 5 years, special-purpose rails of increased wear resistance and contact endu­rance of the DH400RK category were produced from steel with a carbon content >0.8 %. On the head rolling surface of differentially hardened long rails made of hypereutectoid steel after long-term operation, transmission electron microscopy methods revealed the morphological components of the structure: lamellar pearlite, fragmented pearlite, destroyed lamellar pearlite, globular pearlite, completely destroyed pearlite, subgrain structure. The contribution of hardening due to: lattice friction, solid solution hardening, pearlite hardening, incoherent cementite particles, grain boundaries and subboundaries, dislocation substructure and internal stress fields were quantified. A hierarchy of these mechanisms was made and it was noted that for the fillet surface of the rail head, the main hardening mechanism is hardening by incoherent particles, as well as mechanisms caused by internal long-range (local) stresses, internal shear stresses (“forests” of dislocations) and substructural hardening. For the rolling surface along the central axis of the rail head, the main role in hardening belongs to long-range stress fields (especially its elastic component), hardening by incoherent particles and substructural hardening. Taking into account the volume fractions of the morphological components and their yield strength, the additive yield strength on the head rolling surface in the center and on the fillet was determined: 7950 and 2218 MPa, respectively. The paper presents a physical interpretation of the difference in values of the additive yield strength on the rolling surface of the rail head in the center and on the fillet.

Evolution Characteristics of Aluminum Thermal Weld Irregularity and Damage in Heavy-Haul Railway under Different Service Conditions

Aluminum thermal welding joints are widely used in the maintenance welding of heavy-haul railways due to their easy handling and high efficiency. However, due to their inherent welding characteristics, welding results in certain differences in the material’s physical properties at the welding zone compared to adjacent base materials, leading to the occurrence of short-wave irregularity under long-term wheel–rail interactive forces. In order to explore the evolution characteristics of weld irregularity, dynamic characteristics, and plastic deformation under long-term wheel–rail impact, a detailed tracking test was conducted on a normal aluminum weld, and the process from being put on the track to being damaged and replaced was evaluated. At the same time, a rigid–flexible coupling model was established for subsequent analysis, and plastic damage was analyzed using the finite element model. The results show that the service life of the weld can be divided into three different stages: the initial stage, the intermediate stage, and the damage stage. In the damage stage, a temporary separation occurred between the wheel and rail, leading to a sudden change in the wheel–rail interaction. The weight of 250 MT at the weld reached the repairment control limit. The concentration effect of equivalent plastic deformation was most serious at 2~5 mm below the rail head.

Predicting the wear on the non-working side of the rail profile registration method and its validation

Abstract Rail cross-section profile detection can assess the wear and tear of measured rails, providing crucial references for railway maintenance and upkeep. It is challenging to use the conventional method to register only the profile of rail head detection accurately. After the rail edge adjustment in some conventional railways, it becomes difficult to determine the base point of rail profile registration. Due to the wear of non-working edge of rail, a rail profile registration method is proposed. Firstly, a wear prediction model based on the generalized regression neural network is constructed by optimizing smoothing parameters through ten-fold cross-validation to achieve the optimal values. This model predicts the wear values on the non-working rail edge, providing reliable coordinates for two wear points as alignment reference points. Secondly, an initial alignment between the measured profile and the target profile is achieved using the nearest point iterative algorithm, which ensures that both profiles are in the same region and oriented similarly. Thirdly, the weight is assigned to the wear measurement points based on their respective wear values. The predicted positions of wear points are applied for calculating the translation and rotation parameters. These parameters could align the measured profile and facilitate the final profile alignment. Lastly, the experimental profiles under rail adjustment conditions were registered, verifying the accuracy of the proposed method. The research results indicate that under rail adjustment conditions, the mean squared error (MSE) between the calculated and actual values of lateral wear is 0.094 mm2, which is lower than the MSE from manual measurements. The calculated lateral wear value for experimental profiles achieved high alignment and calculation accuracy. This method can be applied in practical projects, providing an effective solution for rail head profile alignment and serving as a reference for profile alignment on the non-working rail edge with incomplete measurement data.

Fatigue Crack Characteristics in Gradient Predeformed Pearlitic Steel under Multiaxial Loading

Rolling contact fatigue of railway rails not only severely deforms the surface material near the rail head, but also induces an anisotropy in the mechanical behavior due to work hardening and alignment of the microstructure along the shear direction. Cracks typically initiate in this region and propagate along the aligned microstructure. The fatigue behavior of rails is evaluated under uniaxial loading in the undeformed material state. However, this is not representative of the contact loading condition and material performance after years of service. Herein, the nonproportional multiaxial fatigue of as‐received and biaxially predeformed pearlitic rail steel R260 is investigated. Four material states are investigated, corresponding to the microstructure found at different depths from the severely deformed surface material at the rail head. A starting notch is machined by electrical discharge machining to control crack initiation and allow for comparable surface crack propagation measurements. The crack path is found to be strongly influenced by the degree of predeformation while the early surface crack propagation rate is found to be similar for all material states.

Ultrasonic dynamic plane wave imaging for high-speed railway inspection

The detection of internal defects within railway tracks stands as a critical aspect of ensuring transport security, given its potential to precipitate severe accidents. Phased array ultrasonic testing methods have gained extensive usage in rail inspection owing to their remarkable precision and expansive coverage. Traditional ultrasonic inspection techniques typically require either a fixed relative position between the transducer and the specimens or a gentle movement of the transducer to beamform. However, the unavoidable vibration stemming from the vehicle–rail coupled interactions often results in time-variant media, significantly impacting the beamforming. This paper presents a refined wavenumber-domain plane wave imaging technique tailored to enable real-time dynamic imaging, specifically accommodating the vertical vibrational movement of the transducer. Real-time calculation of the transmission focal law is achieved by numerical fitting. The wavenumber-domain technique is utilized to realize real-time accurately reconstructed images. The efficacy of the proposed method is assessed through simulations and experiments performed on a convex cylindrical specimen and a rail head sample, respectively. It can be seen that this approach can achieve a frame rate of 83.3 fps with a pipeline architecture in this study, demonstrating the capability to reconstruct images in vibrating environments, such as during the high-speed inspection of railways.

Research on the causes analysis and control methods of line defects in the head of hundred-meter rails

In response to the rail head line defect in the production process of hundred-meter rails, through inspection and analysis of rail tracks with line defects, theoretical calculations of rolling deformation, and on-site industrial trials, it is clarified that the rail head line defect is caused by defects such as cracks in the ingot corners, slab furnace marks, and scratches during rolling. Correspondingly, effective measures to reduce the occurrence of rail head line defects are proposed for each of the three defect causes.

Structural and dynamic assessment of a friction buffer stop

Under peculiar conditions railway braking system ca fail giving insufficient braking force during train ride or while standstill and buffer stops are used to avoid derailments at the end of railway tracks (dead tracks). Fixed stops are suitable only for quasi-static movements, while absorbing energy stops using hydraulic cylinders, friction shoes clamped on the rail head or a combination of both methods, are installed if crashes at higher speeds (about 25 km/h) are forecasted. Impact forces generated due to the interaction between train and buffer stops require a suitable design of the steel structure which is subjected to stress values depending on the braking performances of the buffer stop itself and a combined structural and dynamic analysis must be carried out to perform a proper design. Due to unavailability of detailed models and the uncertainties of the actual braking performances, the structure of currently available friction buffer stops is heavy and bulky, made of several steel profiles welded or bolted to each other. The paper describes an innovative and optimized design for friction buffer stops focusing on the dynamic analysis performed by Finite Element Method to assess the braking performances and structural strength of the buffer stop.

Rail Flaw Detection via Kolmogorov Entropy of Chaotic Oscillator Based on Ultrasonic Guided Waves.

Ultrasonic guided wave (UGW) inspection is an emerging non-destructive testing(NDT) technique for rail flaw detection, where weak UGW signals under strong noise backgrounds are difficult to detect. In this study, a UGW signal identification model based on a chaotic oscillator is established. The approach integrates the UGW response into the critical state of the Duffing system to serve as a disturbance control variable. By evaluating the system's motion state before and after introducing the UGW response, identification of UGW signals can be realized. Thus, the parameters defining the critical state of Duffing oscillators are determined by Ke. Moreover, an electromagnetic transducer was specifically devised to enable unidirectional excitation for UGWs targeted at both the rail base and rail head. Experimental studies showed that the proposed methodology effectively detected and located a 0.46 mm notch at the rail base and a 1.78 mm notch at the rail head. Furthermore, Ke was directly proportional to the notch size, which could be used as a quantitative index to characterize the rail flaw.

Automatic Detection of the Running Surface of Railway Tracks Based on Laser Profilometer Data and Supervised Machine Learning.

The measurement of the longitudinal rail profile is relevant to the condition monitoring of the rail infrastructure. The running surface is recognizable as a shiny metallic area on top of the rail head. The detection of the running surface is crucial for vehicle-based rail profile measurements, as well as for defect detection. This paper presents a methodology for the automatic detection of the running surface based on a laser profilometer. The detection of the running surface is performed based on the light reflected from the rail surface. Three rail surfaces with different surface conditions are considered. Supervised machine learning is applied to classify individual surface elements as part of the running surface. Detection by a linear support vector machine is performed with accuracy of >90%. The lateral position of the running surface and its width are calculated. The average deviation from the labeled widths varies between -1.2mm and 5.6mm. The proposed measurement approach could be installed on a train for the future onboard monitoring of the rail network.

Study on monitoring broken rails of heavy haul railway based on ultrasonic guided wave

Real-time monitoring of broken rails in heavy haul railways is crucial for ensuring the safe operation of railway lines. U78CrV steel is a common material used for heavy haul line rails in China. In this study, the semi-analytical finite element (SAFE) method is employed to calculate the dispersion curves and modal shapes of ultrasonic guided waves in U78CrV heavy steel rails. Guided wave modes that are suitable for detecting rail cracks across the entire cross-section are selected based on the total energy of each mode and the vibration energy in the rail head, web, and foot. The excitation method for the chosen mode is determined by analyzing the energy distribution of the mode shape on the rail surface. The ultrasonic guided wave (UGW) signal in the rail is analyzed using ANSYS three-dimensional finite element simulation. The group velocity of the primary mode in the guided wave signal is obtained through continuous wavelet transform to confirm the existence of the selected mode. It is validated that the selected mode can be excited by examining the similarity between the vibration shapes of a specific rail section and all modal vibration shapes obtained through SAFE. Through simulation and field verification, the guided wave mode selected and excited in this study demonstrates good sensitivity to cracks at the rail head, web, and foot, and it can propagate over distances exceeding 1 km in the rail. By detecting the reflected signal of the selected mode or the degree of attenuation of the transmitted wave, long-distance monitoring of broken rails in heavy-haul railway tracks can be achieved.

Актуализация методики учета аэродинамического воздействия от поездов на высокоскоростных железнодорожных магистралях

In the calculation of structures located near railway tracks (noise protection screens along the tracks, overpasses over high-speed railway lines (HSM) of deck elements with downhill driving, etc.), the aerodynamic effects of high-speed trains shall be considered. Objective: study of the aerodynamic impact of a moving high-speed train on structures and structures, Located in the immediate vicinity of the highspeed railway line with subsequent adjustment of the current regulatory framework for the design of TSM infrastructure facilities. Methods: mathematical modeling in a specialized software complex of computational hydrogas dynamics with experimental verification of the developed calculation models and subsequent analysis and generalization of the obtained results. Results: distribution patterns and aerodynamic intensities from a moving high-speed train for the two most characteristic design cases: impact on a vertical surface parallel to the track axis and on a horizontal surface, located above the axis of train movement. For the calculation cases under consideration, the intensity of the impact was related to parameters such as the distance to the structure from the path axis (for the vertical surface) and the height above the rail head (for the horizontal surface). Practical importance: the need Development of proposals for adjustment and addition of the current regulatory framework for the design of structures and structures included in the infrastructure of high-speed railway lines.

Multi-GPU parallel acceleration scheme for meshfree peridynamic simulations

Peridynamics (PD) using integral equations has unique advantages in modeling structural damage evolution, but the expensive computational and memory costs associated with the nonlocal nature of PD severely limit its engineering applications. This study presents a CUDA-based multi-GPU parallel scheme for meshfree PD simulation, which is compatible with dual-horizon PD supporting multiscale spatial discretization. Efficient utilization of computing resources across all available GPUs is achieved by rationalizing data structures across multiple GPUs and using the CUDA memory model. Using atomic operations to avoid computational dual-bond forces further improves code performance. The classical Kalthoff-Winkler experiment and compact-tensile fatigue test were first carried out using 3 NVIDIA Tesla T4 GPUs. Two examples showed that the proposed scheme significantly accelerates the PD model and that the acceleration enhances approximately linearly with the number of GPUs. The speedup of the PD interaction force computation reaches up to 560.7x. Compared to double-precision floating-point values, the GPU performs much better in handling single-precision values. Finally, a PD simulation of rail head heat conduction under moving heat sources with nearly 76 million particles was realized, demonstrating the potential of the proposed scheme to support large-scale PD simulations.

Examination of industrial safety of structures of the continuous casting Department of the open-hearth shop of the Taganrog Metallurgical Plant

The working draft of the main building of the department of continuous casting of billets (ONLZ) of the open-hearth shop of JSC Tagmet at the stage of "KM" was developed by the DKO of JSC UkrNIIPSK in 2000. Taking into account the design decisions taken and the need to ensure high reliability of structures arising from the specifics of metallurgical production (when installing a heavy duty crane (7K) with a lifting capacity of 225+63/20t at a significant height of the crane rail head – 27 m) in 2001, the customer (JSC Tagmet) decided to carry out an expert examination of design solutions for the main structures of the building frame and engaged the Central Research Institute of Building Structures named after V.A. Kucherenko, who, since 1995, has already conducted surveys of other workshops of the plant, built back in the XIX century, for this work. Then the correctness of the choice of sections and lengths of the elements of the main load-bearing structures was checked and the load-bearing capacity of these elements was assessed. The forces in the elements obtained as a result of carrying out a verification calculation on a computer with the refinement of the design scheme, the applied loads and the quality of steel used in the elements were used. The article presents the reasons for the conduct and results of the industrial safety examination carried out in 2011, a new department was put into operation by 2005, attached to the open-hearth shop.

Можливості підвищення безпеки руху рейкових екіпажів з колесами, що незалежно обертаються

One of the promising ways to achieve high speed and smooth running of rail vehicles during stable movement in straight sections of the track and to improve the characteristics of fitting the vehicles in a curve is the use of independently rotating wheels in their running parts. Such undercarriages are already becoming quite widespread, for example, in urban rail transport vehicles. But independently rotating wheels can rotate in a wheel pair around a common axis with different angular velocities. It follows that during their movement, longitudinal creep forces do not arise, which form the controlling moment and center the wheel pair in the rail track. This can lead to increased angles of attack of the wheels on the rails, increased lateral forces and accelerated wear of the wheels and rails. In turn, this increases the tendency of vehicles with independently rotating wheels to derail by rolling the flange onto the head of the rail. 
 The accumulated global experience of operating similar vehicles confirms this. To overcome the mentioned disadvantages of independently rotating wheels, a number of various technical solutions have been proposed. Some of them relate to ensuring the given elastic-dissipative characteristic of the torsional articulation of the wheels in a wheel pair. A promising direction is the improvement of the characteristics of the connections of wheel pairs with the bogye and bogyes with the vehicle body, the use of mechatronic systems for controlling the position of the wheel pairs in the horizontal plane for their radial installation in curved sections of the track. In this work, attention is paid to the issue of the use in the design of independently rotating wheels of a perspective design scheme that allows independent rotation of the wheel's support surface and its guide surface (flange). The question of the effect of changing the design scheme of the wheel on the safety of movement due to the roll-in of the ridge on the rail head was considered. 
 The influence of a promising design scheme of a wheel in comparison with a traditional design scheme of a wheel on the safety of driving down a rails was investigated. The peculiarities of the distribution of frictional forces in the ridge contact during movement along the rails of the wheels of both design schemes are analyzed. For a wheel of a traditional design scheme, the module and the direction of the friction force vector in the ridge contact are uniquely determined by the geometric characteristics of the contact between the wheel and the rail and the angular speed of the wheel rotation. At the same time, when the wheel of the prospective design scheme moves, the direction and module of the friction force vector of the ridge on the rail also depend on the ratio of the angular velocities of rotation of the supporting surface of the wheel and its guiding surface (flange) around the common axis. The obtained results allow us to draw a conclusion about the expediency of using a promising design scheme in independently rotating wheels to increase the safety of movement of rail vehicles.

In-situ assessment of the sound and vibration reduction performance of a new type of resilient wheel installed on a metro train

Based on a new type of resilient wheel installed on a linear motor subway train, a measurement campaign is devised to evaluate the effectiveness of the resilient wheel in reducing vibration and noise. For reference, the same series of tests are carried out on another train of the same type but fitted with conventional wheels. The measurements consist of the vibration and noise of various parts of the vehicle-track system which are used to investigate the sources of wheel-rail rolling noise, the acceleration of the axle boxes and the rail head, the noise inside the vehicle, and the noise close to the wheels. It is found that the interior noise levels in the driver’s cab and passenger car even when running on a curve with corrugated rails drop below the required limits when using the new type of resilient wheels. The axle box acceleration is used as an indication of the effectiveness of the resilient wheel in reducing the vibration to guarantee the reliability of the bogie frame. The vibration in the lateral direction is reduced considerably on both straight and curved tracks, while in the curve it has a greater decrease.