Track Vibration Research Articles

Methods for separating the noise produced by the wheels and track during a train pass-by

AbstractRolling noise is produced by vibration of the wheels and track, induced by their combined surface roughness. It is important to know the relative contributions of the different sources, as this affects noise control strategies as well as acceptance testing of new rolling stock. Three different techniques are described that aim to use pass-by measurements to separate the wheel and track components of rolling noise. One is based on the TWINS model, which is tuned to measured track vibration. The second is based on the advanced transfer path analysis method, which provides an entirely experimental assessment. The third is based on the pass-by analysis method in combination with static vibroacoustic transfer functions which are obtained using a reciprocity method. The development of these methods is described and comparisons between them are presented using the results from three experimental measurement campaigns. These covered a metro train, a regional train and a high-speed train at a range of speeds. The various methods agree reasonably well in terms of overall trends, with moderate agreement in the mid-frequency region, and less consistent results at low and high frequency.

Method for Predicting Environmental Vibration Impact of Existing Subway Lines and Its Practical Application

To predict accurately the impact of track vibrations caused by subway trains on adjacent buildings and address the problem of their excessive dynamic response, a method for predicting the environmental vibration impact of existing subway lines is proposed in this paper. A coupled numerical dynamical model of the train/track/tunnel system is established using the multi-scale method. Using field-measured soil vibration data, empirical formulas for soil frequency and material damping coefficient are calibrated. By combining the numerical model and the empirical formulas, buildings’ indoor vibrations and noise level can be assessed. At the same time, a solution to the problem of excessive vibration of buildings along a subway line is also proposed that optimizes the track fastener parameters. Field tests verified the accuracy of the prediction method and the effectiveness of the optimized track parameters. These research results provide a reference for predicting the vibration of buildings along subway lines and using the proposed preventive solutions.

A time-domain approach to predict sound radiation from track vibrations

With the intended shift of transport from road to railway, noise exposure due to railway noise will increase. Auralisation of the noise is a key tool for assessing noise perception beyond equivalent sound pressure levels. Researching the connection between, for example, track design parameters and perceived sound quality holds potential for perception-centered track design. A computationally efficient model is required to render the sound field generated by the track vibration. In this paper, using simulated time-domain surface velocities of a rail and sleepers as input, such a model is presented. The sound pressure signal in a position on the side of the track is efficiently predicted by convolving these velocities with precalculated acoustic transfer functions. For a typical ballasted track, the necessary spatial discretisation of the evaluated velocities is determined in a convergence study. Further, the required length of the finite section of the track to be included in the prediction is specified. Finally, pass-by signals generated by track vibration are demonstrated.

Numerical evaluation of rail track noise and vibration and components optimization

In the context of a project commissioned by the Swiss Federal Office for the Environment, an open-source modelling toolbox was developed to simulate and analyze rail tracks dynamics. In particular, a vibro-acoustic multi-sleeper model, which is based on advanced finite element modelling techniques, was used to investigate the effects of components properties on track noise and vibration. Considering changes around a reference construction (60E2 rail, SBB hard pad, B91 sleeper), parametric studies were performed on the dominant parameters identified for the acoustic and ballast protection performance indicators defined. The following sweet spot for the component properties of the track have been identified as using a rail pad of medium stiffness (1000 kN/mm at 1kHz, 300 kN/mm static stiffness) and high damping (at least 0.5) combined with soft Under Sleeper Pads (250 kN/mm). Based on the present models, such combination could provide both a significant noise reduction and a marked improvement in ballast protection compared to current track construction.

A novel double-arch piezoelectric energy harvester for capturing railway track vibration energy

This study introduces a novel piezoelectric stack energy harvester with a double-arched frame structure. This design effectively cushions impacts from track vibrations, thereby protecting the fragile piezoelectric stack made of brittle materials. The energy harvesting characteristics of the device are studied in detail through experiments and theoretical simulations. The harvester's output voltage depends on the external resistance and increases with higher resistance. The optimal resistance for the single X-direction piezoelectric stack is 340kΩ, which can output 0.519mW of power under a 3Hz frequency and an 8kN sinusoidal load. The Y-direction piezoelectric stack outputs 0.012mW, resulting in a total output of 1.050mW for the entire harvester. The output power of the harvester is positively correlated with the load vibration frequency, increasing rapidly for frequencies below 9Hz. The impact of load magnitude on the harvester's output shows a generally linear increase. In impact experiments, the single X-direction piezoelectric stack successfully lit 54 LEDs under a 5J energy impact, demonstrating the harvester's high power density and potential for practical applications.

Prediction of approaching trains based on H‐ranks of track vibration signals

AbstractThis paper introduces a method for forecasting the arrival of trains by analyzing track vibration signals. The proposed algorithms, based on H‐ranks of track vibration signals, can generate early alerts for approaching trains. These algorithms are robust to additive noise and environmental conditions. The theoretical foundation of the method involves the application of matrix operations to detect significant changes in vibration patterns, indicating an approaching train.

Picking up railway track vibration energy using a novel doughnut-shaped piezoelectric energy harvester

Railway transportation is essential for modern infrastructure, and ensuring safety through real-time monitoring of track conditions is critical. However, providing cost-effective and stable power for sensors in remote areas remains a challenge. This paper presents a novel doughnut-shaped piezoelectric energy harvester designed to address this issue. Under a sinusoidal excitation of 50N and 110Hz, the harvester achieves an output power of 0.047 mW, which increases linearly with load. At optimal resistance (230 kΩ) and a load of 3 kN at 7Hz, the output voltage reaches 37.61V, resulting in an output power of 7.23 mW. In track vibration conditions, the harvester produces an output power of 207.67 mW, making it suitable for Internet of Things (IoT) applications, such as powering acceleration and speed sensors to monitor train operations and ensure track safety.

Advances in research on the ballast bed stability on railway bridges

The rapid development of high-speed railway bridges in China has brought enormous challenges to the ballast bed stability on the bridge. With the increase in the bridge span, the bridge deformation under the temperature load increases gradually, as well as the stability difference of ballast bed between different regions. Moreover, the track vibration response under high-speed driving conditions is larger, which can easily cause differential settlement, flying ballast, and deterioration of the ballast bed, thereby affecting the bearing capacity and stability of the ballast bed. In view of this, this article summarizes relevant research work on a ballast bed on the bridge from the perspectives of the resistance, deformation, and acceleration response of the ballast bed. In addition, this study discusses the existing measures for improving the ballast bed stability on the bridge, including the optimization of the sleeper and ballast bed structures. Finally, the main issues that need to be addressed to improve the ballast bed stability on the bridge are pointed out, and ideas for future research on ballast beds on bridges with different spans and structures are proposed.

Rail pad damping characteristics in track vibration reduction evaluated through hammer tests and theoretical analysis

Although the majority of existing research addresses the stiffness characteristics of rail pads, the considerable impact of damping on vibration reduction underscores its significant research importance. In this study, the hammer test and theoretical calculation are both employed to assess the damping capacity across three rail pad types: prismatic (PRP), grooved (GRP), and mesh-type high-damping (MTHDRP). Through the hammer test, the MTHDRP notably surpassed GRP and PRP, achieving higher damping ratios by 51.40 % and 49.71 %, respectively, leading to significant vibration reductions in the track bed and rail. Comparison tests between three types of rail pads highlighted the enhanced performance of the MTHDRP, as it not only reduced vibration amplitudes and enhanced decay rates but also decreased vibration levels by 2−5 dB. Moreover, we established a refined finite element model of the fastener system and integrated it with the Logarithmic Decay Rate (LDR) method. Our findings demonstrate that this combination facilitates the calculation of the damping ratio of the rail pad. Furthermore, we conducted a comparative analysis between the LDR method and the envelope method, confirming its superior efficiency and reliability. Finally, the LDR method is used to predict the damping ratio of the rail pad with varying stiffness, showing that the softer the rail pad, the higher the corresponding damping ratio. Overall, our insights bridge the gap in theoretical calculations and experimental studies on rail pad damping characteristics, offering crucial guidance for rail pad selection in track vibration mitigation.

Floating slab track integrated with quasi-zero stiffness mechanism and dynamic vibration absorber for suppressing low-frequency vibration

Vibration amplification at the natural frequency of floating slab track (FST) remains a significant concern. This study integrates quasi-zero stiffness mechanisms combined with dynamic vibration absorbers (QZSDVA) into FST, resulting in a novel formulation of vibration reduction track (QZSDVA-based FST) to effectively suppress low-frequency track vibrations. The analytical expression for the dynamic response of the two-degree-of-freedom QZSDVA system is derived and subsequently validated through numerical approaches. Building on this, a vehicle-QZSDVA-based FST dynamic model is established and optimal parameters for DVA are identified guided by H ∞ optimisation. Further exploration highlights the capability of QZSDVA-based FST in significantly suppressing track vibrations and reducing the support force of the structure, without compromising running safety of subway train. Results emphasise that optimally tuned parameters enable QZSDVA-based FST to reduce low-frequency vibrations effectively, even with a minimal DVA mass. In comparison to alternative vibration reduction tracks, the proposed QZSDVA-based FST outperforms in suppressing low-frequency vibrations within the range of 6.3–16 Hz. This research offers an innovative solution to mitigate environmental vibrations induced by urban rail transit.

Fuzzy Neural Network Control for a Reaction Force Compensation Linear Motor Motion Stage

Technological progress and market expansion in the semiconductor industry require ultra-precise and high-speed processing and motion systems. However, even though reaction force compensation (RFC) linear motor motion stages help reduce the transmitted reaction force, the residual vibration of the movable magnet track after motion acts as a disturbance, affecting settling time and tracking performance. To address this issue, this study introduces a fuzzy neural network controller for an RFC linear motor motion stage. Since non-linear factors, such as frictional forces from guide rails, make it difficult to accurately model the system, a Nonlinear Autoregressive Neural Network (NARX) is used to identify the nonlinearity from displacement and servo control outputs. The fuzzy logic controller, which takes into account the error and error rate, is then combined with the inverse model controller of NARX. Finally, the fuzzy neural network controllers are integrated with the existing PIV (proportional-integral-velocity) control in feedforward configurations. The experiments demonstrate the potential performance improvements of the proposed approach over the PIV controllers.

Predictive-Cognitive Maintenance for Advanced Integrated railway Management

Railway systems play a vital role in modern transportation and Predictive-Cognitive Maintenance (PCM) has emerged as a transformative approach in the context of Advanced Integrated Railway Management for ensuring the safety, reliability, and efficiency of these systems. PCM leverages data analytics and machine learning to optimize railway system maintenance. This requires effective structural health monitoring (SHM) using low-cost sensor devices. This paper presents a prototype solar-powered wireless sensor node with a 3-axis MEMS accelerometer and energy-harvesting features for monitoring rail track vibrations. The node contains a microcontroller that runs embedded machine-learning models to preprocess the vibration data after train crossing. Abnormal vibrations, indicative of defects, were detected in real time using the TinyML inference at the edge. Instead of raw data, only the model results were wirelessly transmitted to a digital twin in the cloud. The digital twin aggregates data across the rail network for system-level assessment of the RUL and maintenance planning. This edge computing approach minimizes wireless transmission and cloud storage compared to raw sensor streaming. Embedded ML enables real-time damage detection, whereas the cloud digital twin enables system-level prognosis insights. The solar-powered platform enables long-term remote monitoring at low cost without wiring or battery changes. A full-scale physical model was used to validate the edge node prototypes against calculation models and wired accelerometers for impulse loads. The results demonstrate that these nodes can provide a sensor layer for cost-effective PCM in railway systems. In summary, this work proposes an edge computing and embedded ML approach for SHM that integrates cloud-based digital twins to enable the predictive-cognitive maintenance of railway infrastructure. Wireless nodes demonstrate potential for low-cost, convenient, and automated rail health monitoring.

Active mitigation of self-excited vibrations of a magnetic track brake

Active mitigation of self-excited vibrations of a magnetic track brake

Development of transition schemes and optimization measures between normal slab track and ladder-type sleeper track

Severe vibrations and deterioration of track system are often observed due to the sudden change in support stiffness between normal slab track (NST) and damping track. To improve the dynamic performance of both the train and track system when a train runs on the transition zone between the NST and the damping track, we focused on the ladder-type sleeper track (LS track) and developed several optimized transition schemes. Firstly, a train-LS track coupled dynamics mode is developed, and it was verified using field testing. Afterward, using the dynamic responses of train and track systems in the transition zone between the NST and the resilient-fastener slab track (RFS track) as a reference, the shortcomings of the traditional transition scheme are identified, and the optimal transition scheme is developed by comparison of the proposed multiple schemes. Finally, the device for suppressing track vibration (DSTV) is installed on the longitudinal sleeper to alleviate the vibration of the LS track and improve the overall stability of the vehicle and track system during the transition zone. The results indicate that the optimal transition scheme proposed in this study lead to significant improvements in the dynamic performance of both the vehicle and LS track.

Field measurement of track vibration induced by full-load and empty-load condition in curve section of underground metro line

In order to compare the differences in vibration before and after wheel re-profiling and assess the vibration impact of train under full-load and empty-load condition, the field vibration measurement was conducted on an underground metro track components (including rail, sleeper, and track-bed) by using a specific testing car. The results indicate that wheel re-profiling is effective in reducing track vibration, within the frequency range of 31.5–1250 Hz, the vibration acceleration levels of the track after wheel re-profiling were notably lower than those prior to re-profiling and the vibration acceleration levels of the rail, sleeper, and track-bed decrease by 4.7 dB, 6.6 dB, and 6.7 dB, respectively. In the frequency domain, the characteristic peak frequencies of the three track components, whether under full load or empty load, align closely with the frequencies associated with track irregularities. Full-load condition primarily affects the vibration acceleration at lower frequencies, with minor influence on higher frequencies. The vibration acceleration levels of all three track components are higher under full load than empty load. Additionally, under full-load condition, the transmission loss from the rail to the sleeper increases, while the transmission loss from the sleeper to the ballast remains nearly constant. The results of vibration acceleration levels obtained from routine vehicle operations validate the limited impact of axle load on track components vibration.

SMART RAIL SAFETY SYSTEM: MONITORING TRACK CONDITIONS AND PREVENTING DERAILMENTS

The proposed Railway Track Management System is designed to detect faults in railway tracks by continuously monitoring track vibrations using accelerometers installed along the track. These accelerometers measure the vibrations caused by passing trains and other environmental factors. When an abnormal vibration pattern indicative of a track fault is detected, the system triggers an alarm using a buzzer and displays a message on an LCD screen located at the control center. One of the key features of the Railway Track Management System is its ability to identify various types of track faults, including track misalignment, cracks, and loose fasteners, based on distinct vibration signatures. By leveraging advanced signal processing algorithms, the system can differentiate between nor- mal track vibrations and those caused by faults, thus minimizing false alarms. Upon detecting a fault, the Railway Track Management System provides real-time notifications to railway maintenance personnel, enabling prompt action to be taken to address the issue before it escalates. Additionally, the system logs and records fault data, allowing for detailed analysis and predictive maintenance planning Index Terms—Railway Tracks, IR sensor, NodeMCU , MAX30102,L298N Motor Driver

Sustainable Performance of Recycled Rubber and Mining Waste Utilized for Efficient Rail Infrastructure

AbstractUtilizing waste byproducts from mining industries and recycled rubber as alternate materials in railway tracks promotes sustainability of transportation infrastructure, while also increasing track longevity by reducing ballast degradation. This paper provides an overview of two such applications including (i) rubber-intermixed ballast stratum (RIBS) by replacing 10% ballast aggregates with granulated rubber particles with the particle sizes carefully selected according to Australian Standards, (ii) synthetic energy absorbing layer using a mixture of steel furnace slag, coal wash and rubber crumbs to replace traditional capping layer. These materials when tested using large-scale triaxial apparatus and field trials proved that tracks with waste materials performed better than the conventional ballasted tracks by reducing ballast breakage and exploiting the higher damping potential of these materials. Though the vertical deformations of the track slightly increased by using these materials albeit within the specified standards, the overall stability improved by reduced dilation and track vibrations. Increasing the life of ballast layer can lead to long-term cost benefits by saving millions of dollars in track maintenance and provide environment benefits through minimizing quarrying of natural rock aggregates and reducing the carbon footprint of mining industries.

Event-driven piezoelectric energy harvesting for railway field applications

Piezoelectric energy harvesters (PEHs) hold promises for revolutionizing railway structural health monitoring (SHM). However, the challenges of designing high-robust PEHs for handling complex and ever-shifting vibrations in practical railway scenarios remain formidable. Unlike conventional methods that align the fundamental frequency of the PEH with the dominant frequency of the vibration source, this study employs an event-driven enhancement method. This study commences by employing a high-fidelity dynamic model of the PEH and an advanced vehicle-track coupled dynamic model to evaluate energy harvesting efficiency across various railway scenarios. The vehicle-induced track vibrations are predicted across various train speeds, track structures, and track irregularities, considering 12 distinct vehicle-track conditions and totaling 3600 simulation datasets, each representing a specific event. We employ the particle swarm optimization (PSO) algorithm to identify optimal PEH designs for different events. To streamline this process, instead of offering one optimal solution for each event, we employ the K-means algorithm to cluster similar events. Subsequently, we choose the centroid design for each cluster as the representative solution for events within that cluster. This approach allows us to use a limited number of representative PEHs to effectively address most events across different clusters. Finally, we thoroughly examine and evaluate the dynamic responses of these representative designs to demonstrate their robust performance. This study explores PEH design optimization from a fresh perspective, bridging the gap between theoretical design and practical implementation in rail transportation systems.

Stresses in Saturated and Unsaturated Subgrade Layer Induced by Railway Track Vibration

The theoretical and practical studies of the cyclic loads resulting from the movement and passage of trains on the unsaturated subgrade to determine the effect of the degree of saturation and moisture content on the foundations and infrastructure of the railway lines, especially the settlement in the railway lines as a result of the development of the train loads. Thirty-six laboratory experiments were carried out using models that simulate a railway with nearly half the scale of the real one, using an iron box of (1.5 × 1.0 × 1.0) meters and a layer of clay soil with a thickness of 0.5 m representing the base layer, were constructed inside it. Above it, there is a layer of crushed stone representing a 0.2 m thick ballast, topped by a rail line of 0.8 m long installed on three sleeper beams with dimensions of 0.9 m (0.1 × 0.1 m). The subgrade layer has been constructed at different saturation degrees as follows: 100, 80, 70, and 60%. The tests were carried out using different load amplitudes and frequencies. These experiments investigated the effect of the subgrade degree of saturation on the value of the stresses generated on the surface and the middle (vertical and lateral stresses) and the settlement of the subgrade. In the case of unsaturated subgrade soil, an increase in load frequency has a clear effect on increasing the generated stresses in the subgrade layer, especially with lower saturation levels. However, the results and measurements of these experiments found that the load frequency almost had no effect on the values of the stresses generated on the surface and inside the subgrade layer with a 100% degree of saturation. The results of the investigation demonstrated that, while load frequency had a minimal effect on track-panel settlement, it increased with the load amplitude and subgrade soil saturation degree. The change of settlement of the track panel with the number of cycles has a high rate at the beginning; after a while from that, it decreases gradually until, after some value of the number of cycles, the settlement changes at a very low rate and gradually.

Experimental Monitoring of Dynamic Parameters of the Sub-Ballast Layers as a Prerequisite for a High-Quality and Sustainable Railway Line

Monitoring dynamic load transfer from train traffic to sub-ballast layers is crucial for verifying the reliability and safety of railway lines, assessing the design cost-effectiveness and achieving minimum environmental impact. For this purpose, measurements in labs, in situ or modeling the influence of dynamic loads on the immediate and long-term roadway quality are often performed using suitable software. The available test sections enabled monitoring of the dynamic loads and optimizing the critical spots where increased dynamic effects from railway traffic may occur. The subject of this paper is the calibration of the sensors installed in the different test sections of the trans-European corridor number V. As a result, the necessary input parameters for the subsequent numerical modeling of the dynamic effects on the track substructure and vibration propagation on the available sections of the upgraded railway line were obtained. The sensor calibration was carried out on the experimental field, part of the Experimental Basis of the Department of Railway Engineering and Track Management. As part of the calibration, the sensitivity of the sensors embedded in the track bed to the applied dynamic loads resulting from the impact effects of the lightweight deflectometer was assessed. The result of the calibration was the demonstration of sufficient sensitivity of the sensors and their suitability for implementation in an actual railway track structure, with the aim of obtaining relevant values of the response of the sub-ballast layers to dynamic loads and assessing the operational impacts on the sustainable environment. Also, the main result of the research was the possibility of using the theoretical–experimental route to optimize the layers of the railway body.