Turnout Areas Research Articles

The influence of elastic pads deterioration in the fastening system on the dynamic characteristics of the vehicle-turnout system

The deterioration of the elastic pads in the fastening system in high-speed turnout areas increases longitudinal stiffness irregularities along the track, posing potential hazards to wheel-rail impact and train running safety. This paper takes the frog area of No. 18 turnout as an example and constructs a vehicle-turnout rigid-flexible coupling model considering the detailed structure of the fastener elastic pads. By increasing the stiffness of the rubber pad under the tie plate to simulate the deterioration of the elastic pads in the turnout area, the study investigates the effects of deterioration location, degree, and number on the dynamic characteristics of the vehicle-turnout system, providing theoretical guidance for stiffness optimization and maintenance of the turnout area. The results indicate that: 1) the deterioration of the elastic pads significantly affects wheel-rail interaction and safety indicators, while having a minor effect on vehicle running stability; 2) the 95th sleeper (point rail with a top width of 60 mm) is identified as the most critical location for the deterioration of elastic pads; 3) comprehensively considering, the stiffness replacement limit for elastic pads in ballastless turnout areas can be set to twice the design stiffness, which is 50 kN/mm.

Переходные участки бесстыкового пути, примыкающие к стрелочным переводам

Purpose: consider the problem of interaction between turnouts and adjacent sections of a seamless railway track. Methods: statistical data analysis. Results: an analysis of the results of domestic and foreign studies has been carried out, which show that in such areas there is a jump with subsequent extrusion of material of less rigidity and an increase in the slope of the elastic unevenness, i. e., an undesirable phenomenon occurs — a shock wave. The impact force depends on the mass of the rolling stock and the speed of movement, the geometric evenness of the rail track and the chosen approaches to designing the transition zone as a whole. Jump and mainly occurs due to compression and pushing out of structural layers and materials of lower rigidity in the under-rail area. The impact force depends on the mass of the rolling stock and the speed of movement, the geometric evenness of the rail track and the chosen approaches to designing the transition zone as a whole. Jump and mainly occurs due to compression and pushing out of structural layers and materials of lower rigidity in the under-rail area. Shock waves caused by uneven rigidity of sections have negative consequences (the appearance of deviations in level, subsidence, distortions, increased intensity of rail wear, the appearance of rail defects), which increase the cost of maintenance of the railway track. An analysis of the accumulation of residual deformations has been carried out, which shows the systematic formation of geometric irregularities in adjacent areas in the turnout area. Practical importance: from the point of view of the design of the transition zone, the expected advantage will be the differentiation of structural materials and elements and their influence on achieving the optimal gradation of railway track rigidity in the vertical and horizontal (transverse, longitudinal directions), selection of the optimal ratio of the mechanical properties of individual elements of the superstructure structure. It should also be noted that it is necessary to conduct an additional feasibility study of the feasibility of constructing transition sections in the area where the track and switches meet, taking into account the operational features of individual railway lines.

Positioning method of track irregularities in high-speed turnout area based on multi-resolution analysis

The assessment and evaluation of complex track geometry parameters (TGP) in turnout areas present challenges for track recording cars due to uncertainties in their positioning on short sections. To obtain precise and reliable measured TGP in the turnout area, a multi-resolution technology based on maximal overlap discrete wavelet transform (MODWT) is used to perform multi-layer decomposition of the longitudinal level. By utilizing the zero-phase characteristic of MODWT, the TGP can be determined by aligning the decomposed weld spacings with their corresponding theoretical lengths. The positioning error is assessed through statistical analysis of measured TGP and numerical simulation using a virtual track inspection method. Finally, a 70 m length of TGP, including the entire turnout section, was extracted with a positioning error of no more than 1.5 m.

Advancement of data-driven SHM: A research paradigm on AE-based switch rail condition monitoring

The past ten years have witnessed the tremendous progress of structural health monitoring applications in civil infrastructures. This is particularly embodied in railway engineering. The increasing train speed brings greater challenges to safety and ride comfort, and the primary theme of maintenance has been gradually altered from offline inspection to online monitoring. Rail operators must get an in-time warning of potential structural defects before critical failure takes place. It is more favourable that the rail operators can take hold of the real-time status of the key components and infrastructures in railway systems. This paper summarizes a long-term research series by the authors’ research team on online monitoring of rail tracks at turnout areas utilizing acoustic emission-based sensing technique, and more importantly, successively advancing signal processing methods and data-driven analysing frameworks, covering Bayesian inference, convolutional neural networks, transfer learning and task similarity analysis. The proposed algorithms tackle noise interference brought by wheel-rail impacts, great uncertainties in an open environment, and insufficiency of monitoring data, and realize comprehensive monitoring of rail tracks in turnout areas from basic crack detection to regressive condition assessment step-by-step.

Numerical investigation of wheel-rail rolling contact characteristics and damage in a high-speed turnout switch panel under a large ramp

The damage pattern on a railway line under large ramp is more complicated than that of a standard railway line. In order to investigate the influence of the complex wheel-rail contact evolution in the turnout area on the service characteristics of the switch panel under a large ramp, this paper establishes an explicit FE model of the wheel-rail rolling contact on a 40‰ slope. The performance of a train crossing the turnout and the change in mesoscopic contact behavior is then analyzed under different operating conditions. The distribution rule for wear and fatigue damage to the switch rail under a large ramp is studied, with a regulation strategy proposed for improving the service performance of the switch rail based on the results. These show that there is an obvious cyclical incremental phenomenon on the mechanical behavior at the front end of the switch rail, with uneven abrasion distributed throughout the region. The increase in axle weight, speed and friction coefficient increases the stress concentration of the switch rail and exacerbates the damage. As the train passes through the switch panel, the service life of the switch rail can be significantly improved by reducing the traction.

Experiment and analysis of train-induced metro depot vibration

ABSTRACT Vibration induced by metro propagates to the building and affects people’s normal life and work, which has become a key factor restricting the development of over-track building. Relying on an over-track building project in Southwest China, vibration experiments are carried out in turnout area, parking area, over-track area and sensitive area of the metro depot. Acceleration and vibration level are selected as indicators to study the propagation law of vibration in depot structure and evaluate the impact of vibration on depot. The vibration amplification phenomenon of the over-track platform is studied and the functional relationship between the vibration amplification position and the wave velocity, frequency, and bearing column spacing is constructed. Results show that the vibrations of the turnout area are obviously greater than other areas, the maximum vibration is 100.3 dB on the rail. In the process of vibration propagating from the rail to the bearing column, the attenuation increases with the increase of distance, and the vibration is attenuated in the range of 1.25 Hz−200 Hz. The phenomenon of vibration amplification exists at the over-track platform, the maximum z-vibration level is amplified by 4.3 dB at most, which is considered to be caused by the vibration superposition in the depot structure. For the structure studied in this paper, the vibrations with frequencies of 10 Hz, 20 Hz, 31.5 Hz, and 63 Hz cause local vibration amplification of the floorslab, and the maximum position of vibration superposition is related to wave velocity, frequency and bearing column spacing.

Vibration characteristics of subway turnout area during vehicle deceleration and assessment of the model accuracy

Frog gaps and rail joints produces intricate wheel-rail contact conditions within subway turnouts, which results in intense vibrations. This study describes vibration tests conducted on several typical cross-sections of a turnout, which aimed at understanding the vibration transfer characteristics of typical section in turnout area. To separation the vibration signals from each carriage, wavelet analysis and peak detection algorithms were utilized. Using a 2D kernel density algorithm, representative data from the carriages were clustered, effectively isolating the influence of interference data. A coupled vehicle-turnout-tunnel-soil vibration analysis model was established, combining multiple spatial and temporal scales and the accuracy of its prediction was evaluated by comparing the calculated results to statistical test results.The test results indicate that when the train decelerated through the turnout, there was a significant variation in the vibrations of different train carriages, with a 13 dB difference in the total rail vibration levels. The rail joints and frog gap present in the turnout resulted in high vibration level in the tunnel walls. The main frequency of tunnel wall vibration in the frog gap section was 63 Hz, and the total vibration level was 84.9 dB. The accuracy of vibration response prediction was evaluated by comparing the calculated results to statistical test results using probability density functions, and the model errors were maintained within 10 % of the test data. The presented vibration testing and modelling results of vibration propagation characteristics in various directions for the subway turnout area will provide a foundation for selecting vibration mitigation measures.

An investigation into vibration transmission patterns within metro turnout areas utilizing the structural sound intensity method

Urban rail transit turnout areas are notorious for inducing elevated environmental vibrations due to the complex interactions between wheels, rails, and supporting infrastructure. This paper establishes a comprehensive vehicle-track-tunnel-soil coupled dynamic model of a train traversing a turnout region. The intricate vibration transmission mechanisms within the turnout are explored through numerical simulation and visualization of vibration energy flow pathways. The structural sound intensity method facilitates the directional characterization of both transverse and longitudinal elastic waves emanating from the wheel-rail contact zone. Results reveal distinct propagation patterns between the switch panel and crossing panel, with more pronounced low-frequency energy backflow occurring in the switch panel. The transverse wave is found to dominate the elevated lateral vibrations observed along the tunnel walls. Frequency domain analysis maps the variation in energy flow directionality across one-third octave bands. The findings align closely with field measurement outcomes, validating the capacity of the approach to identify vibration "hot spots." Overall, this research enhances the theoretical comprehension of the complex interplay between diverse factors influencing turnout vibration transmission dynamics. The visualization technique proves instrumental in elucidating the critical mechanisms underlying the exacerbated environmental impact within these structurally intricate domains. Practical insights are distilled regarding turnout design strategies, vibration monitoring, and control methodologies to facilitate the mitigation of detrimental vibration effects.

Impact of debonding between layers of ballastless turnouts on the vibration characteristics of the wheel-rail system

The mortar layer of the slab ballastless turnout is the weakest connecting part compared to the rest of the structure, meaning debonding between the turnout slab and the mortar layer is prone to occur under the dynamic load of a train. In order to study the impact of debonding on the vibration response of the wheel-rail system in the turnout area, a rigid-flexible vehicle-turnout coupled dynamic model that takes debonding into account was established based on the theory of vehicle-track coupled dynamics; the flexible deformation of the multi-rail and turnout slab was also included in the model. The impact of debonding on the wheel load transition and the vibration acceleration of the turnout structure and axle box were then analysed. The results show that: There are significant differences in the impact of different types of debonding on the vibration response of the vehicle-track coupled system. When the debonding height is less than the voiding limit, the impact of the debonding height is significant, while the vibration acceleration of the vehicle-turnout system remains basically unchanged once debonding height reaches the void limit.

Experimental study on structure-borne noise of vertical concrete noise barriers sitting on the ground

To investigate the relationship between the structure-borne noise and the vibration of vertical concrete noise barriers sitting on the roadside of the railway, the time-frequency characteristics of the accelerations and sound pressure level of the barrier slab under train crossing events were analyzed by in situ vibration and noise testing. The results show that (1) the vertical vibration level in the mainline area is approximately 94.7 dB, while it is approximately 104.4 dB in the turnout area, and the average increase effect of the vibration level is approximately 9.7 dB. (2) The sound pressure level of the structure-borne noise in the mainline area is approximately 66.4 dB(A), while it is approximately 70.0 dB(A) in the turnout area, and the average increase effect of the sound pressure level is approximately 3.6 dB(A). (3) The vibration is amplified significantly at approximately 40-60 Hz. In summary, the structure-borne noise of the barrier slab is affected by the forced vibration amplification of the barrier slab, and the sound and vertical vibration amplified analysis of the noise barrier under ground motion excitation caused by train operation brought out the related relationship between the vertical vibration and the structure-borne noise.

Investigation on the mechanism and measures of derailment of empty freight train passing a turnout in the diverging route

The derailment of railway vehicles at a turnout is a worldwide concern. However, the derailment of empty freight trains in the switch section of a turnout in the diverging route is rarely concerned. Therefore, in order to analyse the derailment mechanism of empty freight trains in the turnout switch area and to propose appropriate preventive measures, field investigation and dynamic simulation of the derailment are carried out on the basis of an empty freight train derailment in the turnout switch area of the diverging route. Firstly, the background of the derailment is presented and the potential influencing factors of the derailment are analysed according to the field investigation. Secondly, a detailed train-turnout dynamic model is established, taking into account the variable cross-sections of the turnout switch rail and the effect of the longitudinal coupler force. Thirdly, based on the model, the derailment mechanism of the empty freight train is revealed through theoretical analysis and simulation calculation. Finally, the effect of the potential derailment influencing factors is analysed and preventive measures are proposed to reduce the derailment risk of the empty freight train at the turnout switch area in the diverging route. The results indicate that this derailment is caused by the combined effect of the inherent structural characteristics of the switch, the large longitudinal coupler force, and the high wheel rail friction coefficient. The possibility of derailment can be reduced by reducing the longitudinal coupler force and the wheel rail friction coefficient. In addition, the installation of a guard rail in front of the turnout can effectively prevent empty freight train derailment in the turnout area.

Electromagnetic force behavior of superconducting bulks passing electromagnetic turnout

High temperature superconducting (HTS) Maglev is a promising technology owing to its excellent electromagnetic properties of non-control stability and frictionless. As a critical component of HTS Maglev, the turnout poses challenges due to the use of the permanent magnet guideways (PMGs) that are difficult to switch mechanically. With simple structure and rapid responsiveness, electromagnetic turnout has become an interesting research field of HTS Maglev. The electromagnetic turnout is designed to control the electromagnetic force of the HTS bulks by adjusting the magnetic field using an electromagnetic-permanent magnetic structure. However, the magnetic field generated by the combination of the electromagnet and the PMs inevitably differs from the magnetic field above the PMGs, affecting the electromagnetic force behavior of the HTS bulks. To guarantee optimal performance of the electromagnetic turnout, the variation process of the magnetic field peak above the turnout is analyzed. Furthermore, a three-dimensional superconducting model based on the H -formulation and motion equation is built to obtain the electromagnetic force of the HTS bulks passing the turnout. It’s concluded that higher cooling heights in the preparation and higher working heights in the turnout area are recommended to reduce the magnetic resistance and avoid the destabilizing effect. In addition, the smaller bulks experience greater resistance, and the longer bulks are prone to nodding, while the wider bulks are prone to shaking above the turnout. Properly matching HTS bulks with operating conditions improves electromagnetic force behavior and benefits HTS Maglev turnout passability.

Experimental study on the characteristics of vibration energy propagation in the subway turnout area

Due to the scarcity of urban land resources, the development model of building over rail transit has rapidly emerged. The turnouts near the train depots and stations have become significant sources of environmental vibrations. This paper employs on-site experimental methods to measure the vibration acceleration of rail, track slab, and tunnel wall at multiple sections in the turnout area when a subway train passes through. The vibration intensities at different sections of the turnout area are analyzed, and the vibration reduction effects of vibration isolation fasteners and steel-spring floating slabs in the turnout area under similar conditions are compared. Finally, an energy evaluation method is used to analyze the vibration propagation characteristics on the non-isolated turnout frog section. Obtained the propagation and attenuation characteristics of vibrations in different frequency bands in the turnout area based on on-site test data.

Impact of wheel profile evolution on the lateral motion characteristics of a high-speed vehicle navigating through turnout

The wheel-rail contact asymmetry on the left and right sides of the wheelset while navigating high-speed vehicles through turnouts can lead to lateral motion of the wheelset, ultimately resulting in substantial vibrations in the vehicle system. This study employs the trace method to examine the changing pattern of the wheel-rail equivalent conicity in the turnout area as the wheel profile evolves. A coupled system dynamics model containing flexible turnouts is established. Specifically, the model examines the lateral position of wheel-rail contact points, the lateral motion of the wheelset, and the lateral vibration acceleration of the vehicle system. The study indicates that the lateral motion characteristics of high-speed trains passing through turnouts are influenced by the degree of wheel wear. When the wheels are slightly worn (for mileage below or equal to 100,000 km), the lateral dynamic responses of the vehicle system are affected by the inherent structure of the turnout. When the wheels are severely worn (for mileage above or equal to 150,000 km), the lateral dynamic response of the vehicle system is no longer affected by the inherent structure of the turnout.

Train Distance Estimation in Turnout Area Based on Monocular Vision.

Train distance estimation in a turnout area is an important task for the autonomous driving of urban railway transit, since this function can assist trains in sensing the positions of other trains within the turnout area and prevent potential collision accidents. However, because of large incident angles on object surfaces and far distances, Lidar or stereo vision cannot provide satisfactory precision for such scenarios. In this paper, we propose a method for train distance estimation in a turnout area based on monocular vision: firstly, the side windows of trains in turnout areas are detected by instance segmentation based on YOLOv8; secondly, the vertical directions, the upper edges and lower edges of side windows of the train are extracted by feature extraction; finally, the distance to the target train is calculated with an appropriated pinhole camera model. The proposed method is validated by practical data captured from Hong Kong Metro Tsuen Wan Line. A dataset of 2477 images is built to train the instance segmentation neural network, and the network is able to attain an MIoU of 92.43% and a MPA of 97.47% for segmentation. The accuracy of train distance estimation is then evaluated in four typical turnout area scenarios with ground truth data from on-board Lidar. The experiment results indicate that the proposed method achieves a mean RMSE of 0.9523 m for train distance estimation in four typical turnout area scenarios, which is sufficient for determining the occupancy of crossover in turnout areas.

Diamagnetic Screening in the Electromagnetic Turnout Switch for a High-Temperature Superconducting Maglev System

Maglev systems represent a cutting-edge high-speed transport technology, and turnout switches play a critical role in the creation of a highly branched network. There are two common types of turnouts for high-temperature superconducting (HTS) Maglev systems: mechanical and electromagnetic. Due to the many advantages, an electromagnetic turnout is a better choice for a Maglev system than a mechanical one. However, there is a difference in the distribution of the magnetic field over the turnout area and the permanent magnetic track, which cannot meet the safety requirements of the Maglev system. This article proposes a modernized design of an electromagnetic switch based on previously proposed optimization solutions by placing a diamagnetic screen between two electromagnetic poles of an electromagnet, thereby reducing the scattering fluxes between them. The method of diamagnetic screening and experimental methodology are described in this article. The experiment was carried out using a three-dimensional magnetic field scanner to provide results on the distribution of the magnetic field and the increase in the magnetic induction value over the electromagnet poles. Thus, this article provides valuable suggestions for improving the design of the electromagnetic turnout of HTS Maglev systems. Moreover, the proposed method can be applied to any magnetic device or electric machine with an open magnetic circuit.

Experimental and simulation study on rail admittance characteristics in turnout area of urban rail transit

In order to study the dynamic performance of rail-track turnout more widely and deeply, this paper established a 3D refined model of turnout and calculated the condensation characteristics of rail-track through the application of harmonic load sweep frequency analysis. The relevant calculation results are verified by field experiments. It was found that the rail pin-pinned resonance mode in the stock rail and switch rail close position, and jacking block and heel block would be suppressed. The change of switch rail profile caused gradual variation of switch rail admittance characteristic, which showed as the low-frequency original point admittance gradually decreases in the frequency-spatial distribution. The special fastener system of guardrail has limited lateral constraint on the guide rail, resulting in the lateral pin-pinned resonance mode of the guide rail not being significantly observed in the measured results. At the same time, the variation of the vertical bending first-order frequency of the rail was analyzed to analyze the change of the vertical support stiffness in the switch zone. The reliability and shortage of the three-dimensional (3D) track model in the switch zone were also analyzed by comparing the experimental data with the model calculation results.

Dynamic interactions of tram-turnout coupling system in embedded turnout area

Embedded turnout is one of the key facilities in the embedded track network of modern tram systems. In this study, the damping performance and track stiffness of an embedded turnout are tested on site. A multi-rigid body dynamics model of the tram and a finite-element dynamics model of the embedded turnout are established, and the two models are coupled based on the wheel-rail contact theory for the turnout area. Next, the dynamic responses of the tram passing through the embedded turnout are analyzed. The results show that the embedded turnout has favorable damping performance. The high stiffness of variable section rails at the switch and frog would lead to an increase in the wheel-rail dynamic force. When the tram passes through the embedded turnout, the wheel-rail vertical force reaches maximum values of 106.3 and 35.2 kN at the frog and switch, respectively; the maximum wheel derailment coefficient and wheel weight reduction rate are 0.49 and 0.57, respectively, which are within the safety limit specified in the Standards; the maximum lateral and vertical vibration accelerations of the tram body are 0.38 and 0.71 m/s2, respectively, satisfying the comfort requirements; the wheel–rail wear work at the switch is greater than that at the frog.

Study on wear characteristics and authorized limits of switch rails of high-speed turnout

PurposeIt is quite universal for high-speed turnouts to be exposed to the wear of the stock rail of the switch rail during the service process. The wear will cause the change of railhead profile and the relative positions of the switch rail and the stock rail, which will directly affect the wheel–rail contact state and wheel load transition when a train passes the turnout and will further impose serious impacts on the safety and stability of train operation. The purpose of this paper is to provide suggestions for wear management of high-speed turnout.Design/methodology/approachThe actual wear characteristics of switch rails of high-speed turnouts in different guiding directions were studied based on the monitoring results on site; the authorized wear limits for the switch rails of high-speed turnout were studied through derailment risk analysis and switch rail strength analysis.FindingsThe results show that: the major factor for the service life of a curved switch rail is the lateral wear. The wear characteristics of the curved switch rail of a facing turnout are significantly different from those of a trailing turnout. To be specific, the lateral wear of the curved switch rail mainly occurs in the narrower section at its front end for a trailing turnout, but in the wider section at its rear end when for a facing turnout. The maximum lateral wear of a dismounted switch rail from a trailing turnout is found on the 15-mm wide section and is 3.9 mm, which does not reach the specified limit of 6 mm. For comparison, the lateral wear of a dismounted switch rail from a facing turnout is found from the 35-mm wide section to the full-width section and is greater than 7.5 mm, which exceeds the specified limit. Based on this, in addition to meeting the requirements of maintenance rules, the allowed wear of switch rails of high-speed turnout shall be so that the dangerous area with a tangent angle of wheel profile smaller than 43.6° will not contact the switch rail when the wheel is lifted by 2 mm. Accordingly, the lateral wear limit at the 5-mm wide section of the curved switch rail shall be reduced from 6 mm (as specified) to 3.5 mm.Originality/valueThe work in this paper is of reference significance to the research on the development law of rail wear in high-speed turnout area and the formulation of relevant standards.

Investigation of transient wheel-rail interaction and interface contact behaviour in movable-point crossing panel

The high-speed turnout is a key part of railway track infrastructure. A process of wheel-load transition and single-wheel/multi-track contact take place in the turnout area, causing significant wheel-rail interaction. Most high-speed turnouts include movable-point crossings. To investigate the wheel-rail transient rolling contact behaviour in movable-point crossings, a 3D finite element (FE) model of a wheelset rolling over a crossing was introduced. The actual geometrical profile of the wheel and the rails in turnouts, the nonlinear materials, the actual relative motion between the point/wing rail, and the moving postures of the wheelset were considered. The simulated mode shape was compared with the experimental mode shape to verify the wheel-rail coupling model. Precise frictional rolling contact solutions and dynamic response, including wheel-rail force, contact stress, equivalent stress, equivalent plastic strain, and stick-slip distribution of the contact patches, were all studied. After this, the parametric analysis of dynamic wheel-rail contact behaviour was carried out. The simulated results indicate that the proposed explicit finite element method can characterise wheel-rail coupled dynamic interaction and mesoscopic rolling contact behaviour well, and improve the understanding of wheel-rail contact behaviour in the movable-point crossing panel of the high-speed turnouts.