Vibration Of Railway Track Research Articles

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.

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.

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.

Analysis of bending waves and parametric influence on band gaps in periodic track structure

Vibration of railway tracks generated due to rail-wheel interaction is a key research concern. A rail with equally spaced supports can be regarded as a periodic structure. Such a structure possesses unique property of band gap because of that they act as vibro-acoustic filters. Here, the propagation behavior of vertical and lateral bending waves is studied in a periodic ballastless track structure. Bloch-Floquet theorem is used to formulate the dispersion relations for the propagation of two types of waves which is validated by corresponding finite element model. The results show coexistence of both resonance and Bragg type band gaps they are owing to locally resonant units and spatial periodicity in the track. Furthermore, the study also explores the impact of track parameters, such as pad stiffness and sleeper spacing, on the properties of these band gaps.

Design, modelling and testing of a compact piezoelectric transducer for railway track vibration energy harvesting

To enable wireless sensor networks to monitor rail infrastructures in real-time, a cost-effective power source is in need. This work presents the design, modelling and testing of a piezo stack energy harvester with frequency up-conversion mechanism for scavenging energy from railway track vibration. The proposed harvester is designed to meet railway track applications’ size, frequency, and stress requirements. A compact design integrating the inertial mass and the piezo stack transducer systems is used to enable the mechanical collision for realising the frequency up-conversion mechanism and ensure the size of the energy harvester is suitable for the limited space on the railway track. The frequency bandwidth of the energy harvester is broadened by utilizing the longitudinal and torsional oscillation of the designed plate springs which enable the system to have two adjacent natural frequencies. The mechanical transformer of the piezo stack transducer system is designed to achieve the required stress level under both the impact force caused by the collision motion and the inertial force generated by the random vibration of the rails. A finite element model (FEM) analysing the free vibration of the piezo stack transducer caused by the frequency up-conversion mechanism is developed to analyse the dynamic characteristics of the coupled system. Lab tests are carried out to validate the proposed FEM and evaluate the impact of different factors such as load resistance, acceleration, initial interval, plate spring, and pulse excitation on power generation. Experimental results show that the energy harvester has two resonant frequencies of 17 Hz and 20 Hz. The frequency up-conversion mechanism can convert this low-frequency vibration into the piezo stack transducer’s high resonant frequency vibration of 94 Hz. A maximum average power of 6.72 mW with a 1-mW-bandwidth of 15 Hz is obtained when actuated at 0.7 RMS g acceleration. • A piezo stack energy harvester for railway track vibration is designed, modelled and tested. • A compact design is proposed to enable the mechanical collision for realising the frequency up-conversion mechanism. • Two adjacent natural frequencies are achieved to broaden the frequency bandwidth. • The mechanical transformer is designed to achieve the required stress level under the impact force and inertial force. • A maximum average power of 6.72 mW with a 1-mW-bandwidth of 15 Hz is obtained when actuated at 0.7 RMS g acceleration.

Railway Track Vibration Analysis and Intelligent Recognition of Fastener Defects

AbstractThe rail fastener is an indispensable component used to connect the rail and sleepers in the track structure. Real‐time recognition of the fastener defects plays a vital role in ensuring the safe and stable operation of rail transit. In this paper, an intelligent and innovative method is proposed to detect the fastener defects including the invisible defects appearing as bolt loosening and the visible defects such as the worn or completely missing fasteners by using axle‐box vibration acceleration and deep learning network. First, the dynamical relation between the fastener defects and the axle‐box vibration acceleration is investigated by using the first principle and the vehicle–track dynamical model. Then a defects recognition network is built based on the deep convolution neural network for track fasteners by using the frequency spectrum images of the axle‐box vibration. The results show that the proposed method achieves a classification accuracy of 98.27%. Finally, the track section where the fasteners are most likely to be damaged is investigated, and rail corrugation is found to be a key factor that causes fastener fatigue.

Energy harvesting from railway slab-tracks with continuous slabs

This paper contributes to the literature and development of knowledge in the topic of energy harvesting by presenting the modelling and calculations of energy from vibration of railway tracks due to moving trains on floating-slab tracks with continuous slabs, considering both the quasi-static and dynamic effects. The floating-slab track is modelled as a double Euler–Bernoulli beam connected by continuous spring and damper elements. The dynamic excitation is accounted for by considering the un-sprung axles of a passing train with a number of coaches. The dynamic excitation is simulated using randomly generated unevenness from standard functions of power spectral density . The responses of rails’ beam and slab are calculated for different unevenness realizations, and then used as inputs for a base-excited single-degree-of-freedom system that models the harvester. The change in the harvested energy is investigated due to the change of natural frequency of the harvester, the change of condition of track and change of train’s velocity. The parameters used in this paper correspond to tracks and trains for Doha metro and unevenness information from the literature. The results show that more energy can be harvested by tuning the harvester’s natural frequency to the frequency of axle-track resonance. It is found that a maximum mean-energy can be harvested from the rails of 0.35 J/kg for a train moving at 100 km/h for a track with poor condition and this is obtained at the axle-track resonance frequency. For the same track condition, a reduction of about 55% and 61% is observed for train’s velocities of 70 km/h and 40 km/h, respectively. Using a track with medium and good conditions resulted in reduction of the mean harvested energy at the axle-track resonance by 73.5% and 99.9%, respectively.

Identification of Bending Modes of Vibration in Rails by a Laser Doppler Vibrometer on a Moving Platform

This paper introduces a method to identify the bending modes of vibration of railway tracks by using a laser Doppler vibrometer (LDV) mounted on a moving platform. Two sets of experiments were conducted at Transportation Technology Center Inc. (TTCI) in Pueblo Colorado, in order to validate the proposed method. First, the bending vibration modes were identified using the signals collected from a rail span (rail section between two consecutive sleepers) by accelerometers under moving car excitation. Then, vibration measurements from rail spans were obtained by using an LDV mounted on the moving railcar. All tests were carried out at four different rail car speeds: 8 km/h (5 mph), 16 km/h (10 mph), 35 km/h (22 mph), and 45 km/h (28 mph). To find LDV signal segments corresponding to rail spans, a novel approach based on the sleeper passing frequency is introduced. Comparison of the results from both sets of tests demonstrated good agreement for all speeds.

The equivalent dynamic stiffness of a visco-elastic half-space in interaction with a periodically supported beam under a moving load

A periodically supported beam on a visco-elastic half-space is considered to model the vibration of railway tracks. The viscosity of the half-space is assumed to be of the Kelvin-Voigt type. Making use of the concept of equivalent dynamic stiffness, the reaction of the half-space to the sleepers is replaced by a system of identical spring located under each sleeper. The frequency-dependent equivalent stiffness of the springs is a function of the phase shift of vibrations of neighbouring supports. The equivalent stiffness is derived analytically employing the contour integration technique, resulting in a comprehensive expression for different phase velocities of the waves in the beam with respect to the wave speeds of the half-space. Apart from the Rayleigh type surface wave (quasi-elastic wave), an extra visco-elastic surface wave may exist in a visco-elastic half-space depending on the parameters of the half-space and the frequency range. The existence of this second surface wave has not been addressed within the field of train-induced ground vibration. The importance of this wave for the equivalent stiffness is analysed. An effective method to determine the frequency range for the visco-elastic surface wave to exist is proposed.

Simulation of Power Generation from Vibration of Railway Track

Ethiopia has a small percentage of its population accessing electricity with some power utilized by its transportation sector; there are frequent power outages that slow down economic activities such as trade and railway transportation. From this previous statement, it is clear that the demand for energy is significantly increasing and there is too much dependability on the current energy source. With the development of sustainable energy technology in the world today, this problem can be alleviated, while utilizing component vibration in railway infrastructure. The aim of this study was to estimate energy generation potential from the vibration of a railway track induced by a passing train using a two degree of freedom oscillator. Data was collected; energy harvesting system was modeled and simulated. Based on the result, the system produces enough energy to power communication and signaling equipment on the track. The optimum parameters: mass of 1 kg, a spring stiffness of 6 N/m and a damping coefficient of 4 Ns/m of the energy harvester were determined using sensitivity analysis. The cumulative mechanical power harvested by the inter-city-125 train at a speed of 195 km/h was calculated to be 224.56 W. Therefore, the energy demand of the communication and signaling equipment of the train track can be achieved using vibration energy harvesting system by installing the number that meets the demand.

A semi-analytical beam model for the vibration of railway tracks

The high frequency dynamic behaviour of railway tracks, in both vertical and lateral directions, strongly affects the generation of rolling noise as well as other phenomena such as rail corrugation. An improved semi-analytical model of a beam on an elastic foundation is introduced that accounts for the coupling of the vertical and lateral vibration. The model includes the effects of cross-section asymmetry, shear deformation, rotational inertia and restrained warping. Consideration is given to the fact that the loads at the rail head, as well as those exerted by the railpads at the rail foot, may not act through the centroid of the section. The response is evaluated for a harmonic load and the solution is obtained in the wavenumber domain. Results are presented as dispersion curves for free and supported rails and are validated with the aid of a Finite Element (FE) and a waveguide finite element (WFE) model. Closed form expressions are derived for the forced response, and validated against the WFE model. Track mobilities and decay rates are presented to assess the potential implications for rolling noise and the influence of the various sources of vertical-lateral coupling. Comparison is also made with measured data. Overall, the model presented performs very well, especially for the lateral vibration, although it does not contain the high frequency cross-section deformation modes. The most significant effects on the response are shown to be the inclusion of torsion and foundation eccentricity, which mainly affect the lateral response.

Automatic flipping magnet type electromagnetic energy harvester

A new flipping magnet type electromagnetic energy harvester (EEH) suitable for scavenging energy from low frequency vibrations is presented in this Letter. The proposed EEH has a spherical permanent magnet (SPM), which is free to move inside a spherical bobbin that carries coils. Two cylindrical permanent magnets are employed to flip the SPM fast, even if the frequency of vibration source is low. This induces sufficient voltage in the coil to convert to dc and use. No such scheme has been reported so far and the existing EEHs give very low induced voltage for low frequency vibrations <5 Hz. Two versions of the new EEH prototypes, were built and tested. The peak-to-peak open circuit voltage of version-1 was 3.5 V and the power density was 445 µW/cm3 for a matched load of 52.5 Ω at 3.5 Hz vibration. The power density of the version-2 harvester was 538.6 µW/cm3. One of the applications of the proposed EEH is to harvest energy from railway tracks, for powering trackside monitoring sensors. The prototype developed generated up to 2.44 mW for an emulated railway track vibration in the range of 4 Hz, which is a considerable improvement compared with the existing EEHs.

Current state of practice in railway track vibration isolation: an Australian overview

Inevitably, train and track interaction generates a travelling source of noise and vibration along the railway corridor. Railway noise is generated in various forms and spectra. The undesirable railway sound and vibration include rolling noise, impact noise, curve noise, mechanical noise, airborne noise, wheel/rail noise, structure- and ground-borne noises. The noise that is carried through the vehicle body mainly affects ride quality, customer experience and structural integrity of the rolling stocks, whereas the vibration that is transmitted from the rails to the supporting structure of the track plays a main role in rapid track degradation and potentially affects the surrounding structures. This study highlights the practical guidelines for track vibration isolation resulting from the operation of railways. Its emphases are placed on the contemporary vibration mitigation methods used in existing and ageing railway infrastructures (the so-called ‘brown field project’). Its aim was to provide the overview and lessons learnt for the future development of new vibration isolation strategies in practice.

Influence of Preload and Nonlinearity of Railpads on Vibration of Railway Tracks under Stationary and Moving Harmonic Loads

In railway track dynamics, the stiffness and damping properties of railpads have a significant effect on track vibration, decay rates as well forces transmitted to the track supporting structure. Many studies have shown that railpads exhibit pronounced nonlinear behaviour, with preload and frequency dependent properties. This paper presents a three parameter railpad model, together with its differential equation of motion and the required model parameters obtained from experimental data. A time domain model of a rail discretely supported on these railpads is then formulated using the finite element method. The model is subjected to static and dynamic loading in order to study the effects of preload and frequency on its dynamic behaviour. Results are shown as time histories and frequency spectra for the track displacements and reaction forces for various preload levels. They emphasise the necessity of accounting for nonlinear behaviour based on the large disparities (up to 20 dB) observed between the linear and nonlinear cases for the parameters used in this study.

Design of a Bimorph Piezoelectric Energy Harvester for Railway Monitoring

Wireless sensor network is one of prospective methods for railway monitoring due to the long-term operation and low-maintenance performances. How to supply power to the wireless sensor nodes has drawn much attention recently. In railway monitoring, the idea of converting ambient vibration energy from vibration of railway track induced by passing trains to electric energy has made it a potential way for powering the wireless sensor nodes. In this paper, a bimorph cantilever piezoelectric energy harvester was designed based on a single degree-of-freedom model. Experimental test was also performed to validate the design. The first natural frequency of the bimorph piezoelectric energy harvester was decreased from 117.1 Hz to 65.2 Hz by adding 4 gram tip mass to the free end of the 8.6 gram energy harvester. In addition, the power generation of the piezoelectric energy harvester with 4 gram tip mass at resonant frequency was increased from 0.14 mW to 0.74 mW from <TEX>$2.06m/s^2$</TEX> base excitation compared to stand-alone piezoelectric energy harvester without tip mass.

Attenuating Railway Track Vibration by Rail Absorber for Noise Reduction

A promising means to increase the decay rate of vibration along the rail is using a rail absorber for noise reduction. Compound track models with the tuned rail absorber are used for investigation of the performance of the absorber on vibration reduction. Through analysis of the track dynamics with the rail absorber some guidelines are given on selection of the types and parameters for the rail absorber. It is found that a large active mass used in the absorber is beneficial to increase the decay rate of rail vibration. The effectiveness of the piecewise continuous absorber is moderate compared with the discrete absorber installed in the middle of sleeper span or at a sleeper. The most effective installation position for the discrete absorber is in the middle of sleeper span. Over high or over low loss factor of the damping material used in the absorber may degrade the vibration reduction performance.

Sensitivity analysis applied to a dynamic railroad model

An analytical method of analyzing sensitivity is presented. It is shown that in a special case, when the dynamical problem is described by differential equations (of any order) with constant coefficients, first and second order semilogarithmic (semirelative) sensitivity functions can be determined analytically. The method is applied to the practical problem of railway track vibration, with the intention of using it for the identification of railway track model parameters in the future. The railway track model is an infinite beam resting on multi-parameter viscoelastic subsoil.

Hodgson &amp; Hodgson Introduces RockBallast to the UK

Hodgson &amp; Hodgson Group Limited has been appointed sole distributor of RockDelta's innovative RockBallast railway track vibration control system

Hodgson &amp; Hodgson Introduces RockBallast to the UK

Hodgson &amp; Hodgson Group Limited has been appointed sole distributor of RockDelta's innovative RockBallast railway track vibration control system

軌道振動解析におけるレール頭頂面の凹凸形状の推定

軌道振動解析におけるレール頭頂面の凹凸形状の推定