Average Vibration Research Articles

Vibration Analysis of the Bow Bridge With and Without the Soil Foundation

Abstract. Earthquakes can impart the phenomenon of resonance, where the frequencies of seismic waves align with a bridge's natural frequency, causing amplification of vibrations that can lead to structural failures. Aiming to accurately predict potential vulnerabilities posed to the bridge when subjected to earthquakes, this research presents a vibration analysis of the Bow Bridge. Two models, which simulate the Bow Bridge with and without soil foundation, are conducted to investigate the bridges natural frequencies and mode shapes under soilless and soiled conditions. The research result shows that the average vibration frequency in a soiled environment is much lower than that in a non-soil environment, intuitively proving the mitigation of soil environment to bridges vibration frequencies. Based on the agreeable data output, this research demonstrates the feasibility of modeling in the prediction of practical construction.

A Super Vibration Drag Reduction System Based on Drilling Robot

Summary For directional or horizontal wells, friction between the drillstring and the borehole wall has become a significant factor in reducing the rate of penetration, leading to a decrease in weight on bit (WOB) and inefficient rock breaking. Generally, a larger amplitude yields a better oscillation effect. Conventional hydraulic oscillators rely on their inherent inertia to produce oscillating loads. However, the mass of the oscillating load provided by hydraulic oscillators is relatively small compared with the entire pipe string, resulting in limited oscillation amplitude that fails to effectively reduce friction and drag. To enhance the vibration effect and strength of the pipe string, in this article we propose the development of a novel hydraulic oscillation device that utilizes drilling robots for support. The relevant structure of the drilling robot has been designed, and a simulation wellbore experiment platform, based on the drilling robot, has been constructed. The simulation wellbore experiment based on different supporting conditions was completed. Through analysis of the collected experimental data, it has been observed that the axial and radial vibrations generated by the drilling robot are influenced by its supporting condition. The average acceleration amplitude and frequency of axial vibration without support are measured to be 0.37 m/s² and 8.2 Hz, respectively. In contrast, with supporting conditions, the average axial vibration acceleration amplitude increases to 0.63 m/s², and the frequency reaches 12.8 Hz. Consequently, the axial vibration intensity of the drilling robot is significantly higher when the drilling robot is supported. The average acceleration amplitude and frequency of radial vibration without support are 0.83 m/s² and 20.4 Hz, respectively. However, with supporting conditions, the average radial vibration acceleration amplitude drops to 0.43 m/s², and the frequency decreases to 12.2 Hz. The average axial vibration displacement amplitude of the supported drilling robot measures 50.2 mm, which is much greater than that of a typical hydraulic oscillator. Moreover, the WOB of the drilling robot with support is considerably higher compared with the unsupported drilling robot. By employing supporting conditions, the drilling robot can improve the transmission efficiency of drilling pressure and minimize the damage caused by radial vibration to downhole tools.

Investigating the effect of hot and cold polyurethane foam on reducing whole body vibration of forklift operators.

Vibration is one of the harmful factors for forklift drivers. The use of non- standard seats and not paying attention to how the seats are maintained can be affected by the amount of vibration transmitted to the person. This study investigates the amount of vibration transmitted from the forklift and the effect of different types of polyurethane foam in reducing the vibration transmitted from the forklift seat. This descriptive-analytical study was performed on 38 forklifts in 4 diesel models with the same weight class. The amount of vibration transmitted from forklift seats according to ISO2631 standard, taking into account the effect of various factors such as foam type (hot and cold), thickness (6-12 cm), load and year Function was measured. The amount of vibration caused by the forklift on the seat and under the seat was evaluated using ISO7096 standard. The average total vibration of the whole body in all foams in no-load mode is more than with load. The transmission vibration of cold polyurethane foam is less than that of hot polyurethane foam. With increasing thickness, the efficiency of cold polyurethane foam increases by 12 cm and in the loaded state 40.63% and in the unloaded state 49.58% in reducing the vibration transmitted to drivers. The results of this study show that cold foam has better effectiveness and efficiency than hot polyurethane foam. Also, the thicker the foam, the less vibration is transmitted to the driver.

Exploring Semi-Active TMD Performance on Lively Footbridges Considering Human–Structure Interaction in Vertical Direction

Human–Structure Interaction (HSI) can significantly influence the dynamic characteristics of pedestrian footbridges, particularly those distinguished by their lightness and slenderness. This study examines the performance of Tuned Mass Dampers (TMD) and Semi-Active Tuned Mass Dampers (STMD) on pedestrian footbridges when their modal parameters change due to the influence of HSI. For this purpose, a 30 m long simply-supported footbridge with linear mass values ranging from 200[Formula: see text]kg/m to 2[Formula: see text]000[Formula: see text]kg/m and a fundamental frequency varying from 1[Formula: see text]Hz to 5[Formula: see text]Hz has been considered. In addition, several pedestrian streams with different pedestrian densities have been used to assess the structural dynamic response. The analysis highlights that structural lightness and slenderness are critical factors in determining whether the incorporation of an HSI model is relevant to accurately predict the dynamic performance of the structure. The findings indicate that while TMDs can become ineffective due to shifts in natural frequencies caused by HSI, resulting in a degradation of vibration reduction from 70–75% to 40–45%, STMDs demonstrate a robust capability to adjust and cope with these frequency changes, maintaining a higher average vibration reduction of around 55–60%. Consequently, STMDs emerge as a necessary solution for very slender structures where HSI significantly alters the global frequency response. This study highlights the importance of considering HSI in the design and implementation of damping solutions to ensure optimal functionality and user comfort on lightweight pedestrian bridges.

The coupled band gap of longitudinal wave in metamaterial-based double-rod containing resonators

This study investigates the coupled band gap and vibration propagation characteristics of elastic waves in a metamaterial elastic double-rod system with attached periodic resonators. We derive the band gap structure and vibration attenuation equations of double-rod structure using the spectral element method, Bloch’s theorem, and the transfer matrix method. The validity of the coupled band gap is confirmed through forced vibration response analysis. Furthermore, we examine the effects of various parameters on the double-rod system, revealing that coupled band gaps exist with the average vibration attenuation rates of −50.23 dB for rod one and −47.87 dB for rod two, respectively. Remarkably, by adjusting the double-rod parameters, both the band gap frequency range and vibration attenuation ability of the coupled band gap can be adjusted to meet specific engineering requirements in low-frequency regions. This research contributes to developing continuous mechanical structures featuring coupled band gaps.

Increased atom-cavity coupling through cooling-induced atomic reorganization

The strong coupling of atoms to optical cavities can improve optical lattice clocks as the cavity enables metrologically useful collective atomic entanglement and high-fidelity measurement. To this end, it is necessary to cool the ensemble to suppress motional broadening, and advantageous to maximize and homogenize the atom-cavity coupling. We demonstrate resolved Raman sideband cooling via the cavity as a method that can simultaneously achieve both goals. In 200 ms of Raman sideband cooling, we cool Yb171 atoms to an average vibration number 〈nx〉=0.23(7) in the tightly binding direction, resulting in 93% optical π-pulse fidelity on the clock transition S01→P03. During cooling, the atoms self-organize into locations with maximal atom-cavity coupling, which will improve quantum metrology applications. Published by the American Physical Society 2024

Bandgap Calculation and Experimental Analysis of Piezoelectric Phononic Crystals Based on Partial Differential Equations.

Focusing on the bending wave characteristic of plate-shell structures, this paper derives the complex band curve of piezoelectric phononic crystal based on the equilibrium differential equation in the plane stress state using COMSOL PDE 6.2. To ascertain the computational model's accuracy, the computed complex band curve is then cross-validated against real band curves obtained through coupling simulations. Utilizing this model, this paper investigates the impact of structural and electrical parameters on the bandgap range and the attenuation coefficient in the bandgap. Results indicate that the larger surface areas of the piezoelectric sheet correspond to lower center bands in the bandgap, while increased thickness widens the attenuation coefficient range with increased peak values. Furthermore, the influence of inductance on the bandgap conforms to the variation law of the electrical LC resonance frequency, and increased resistance widens the attenuation coefficient range albeit with decreased peak values. The incorporation of negative capacitance significantly expands the low-frequency bandgap range. Visualized through vibration transfer simulations, the vibration-damping ability of the piezoelectric phononic crystal is demonstrated. Experimentally, this paper finds that two propagation modes of bending waves (symmetric and anti-symmetric) result in variable voltage amplitudes, and the average vibration of the system decreases by 4-5 dB within the range of 1710-1990 Hz. The comparison between experimental and model-generated data confirms the accuracy of the attenuation coefficient calculation model. This convergence between experimental and computational results emphasizes the validity and usefulness of the proposed model, and this paper provides theoretical support for the application of piezoelectric phononic crystals in the field of plate-shell vibration reduction.

Pickleball sounds: impact induced vibration and radiated sound

The rapid growth in popularity of pickleball and the ever-increasing number of pickleball courts has resulted in growing concerns about the effect of pickleball sounds on nearby neighbors. The vibration of the ball and paddle that is generated at impact, and which is the source of the radiated sound, was measured for different paddles as a function of frequency using an impact hammer instrumented with a force gage. Average vibration velocities over the paddle surface were generated that scale the radiated sound. Animations of paddle vibration were also generated. A paddles vibration level depends on its internal mechanical damping which was also measured. A performance metric is proposed where the paddles' sound levels are compared at the same "power" in terms of the change in momentum (velocity) of the pickleball on impact. Outdoor directivity measurements of the sound for a paddle were "dipole-like" in character with lower levels, by 10 dB or more, in the plane of the paddle compared to levels perpendicular to its face. The orientation of the courts may be important if the sound levels during play are quieter in the general direction along the nets.

Experimental Investigation of the Sensitivity of Forced Response to Cold Streaks in an Axial Turbine

In turbomachinery, geometric variances of the blades, due to manufacturing tolerances, deterioration over a lifetime, or blade repair, can influence overall aerodynamic performance as well as aeroelastic behaviour. In cooled turbine blades, such deviations may lead to streaks of high or low temperature. It has already been shown that hot streaks from the combustors lead to inhomogeneity in the flow path, resulting in increased blade dynamic stress. However, not only hot streaks but also cold streaks occur in modern aircraft engines due to deterioration-induced widening of cooling holes. This work investigates this effect in an experimental setup of a five-stage axial turbine. Cooling air is injected through the vane row of the fourth stage at midspan, and the vibration amplitudes of the blades in rotor stage five are measured with a tip-timing system. The highest injected mass flow rate is 2% of the total mass flow rate for a low-load operating point. The global turbine parameters change between the reference case without cooling air and the cold streak case. This change in operating conditions is compensated such that the corrected operating point is held constant throughout the measurements. It is shown that the cold streak is deflected in the direction of the hub and detected at 40% channel height behind the stator vane of the fifth stage. The averaged vibration amplitude over all blades increases by 20% for the cold streak case compared to the reference during low-load operating of the axial turbine. For operating points with higher loads, however, no increase in averaged vibration amplitude exceeding the measurement uncertainties is observed because the relative cooling mass flow rate is too low. It is shown that the cold streak only influences the pressure side and leads to a widening of the wake deficit. This is identified as the reason for the increased forcing on the blade. The conclusion is that an accurate prediction of the blade’s lifetime requires consideration of the cooling air within the design process and estimation of changes in cooling air mass flow rate throughout the blade’s lifetime.

Digital Simulation of Coupled Dynamic Characteristics of Open Rotor and Dynamic Balancing Test Research

An aero engine, as the core power equipment of the aircraft, enables safe and stable operation with a very high reliability index, and is an important guarantee in flight. The open rotor turbine engines (contra-rotating propeller) have stood out as a research hotspot for aviation power equipment in recent years due to their outstanding advantages of low fuel consumption, high airspeed, and strong propulsion efficiency. Aiming at the problems of vibration exceeding the standard generated by imbalance during the operation of the dual-rotor system of aircraft development, the difficulty of identifying the coupled vibration under the micro-differential speed condition, and the complexity of the dynamic characteristic law, a kind of numerical simulation of the dynamics based on the finite element technology is proposed, together with an experimental research method for the fast and accurate identification of the coupled vibration of the dual-rotor system. Based on the existing open rotor engine structure design to build a simulation test bed, establish a double rotor finite element simulation digital twin model, and analyze and calculate the typical working conditions of the dynamic characteristics of parameters. The advanced algorithm of double rotor coupling vibration signal identification is utilized to carry out decoupling and dynamic balancing experimental tests, comparing the simulation results with the measured data to verify the accuracy of the technical means. The results of the study show that the vibration suppression rate of the finite element calculation simulation test carried out for the simulated double rotor is 98%, and the average vibration reduction ratio of the actual field test at 850 rpm, 1000 rpm, and 3000 rpm is over 50%, which achieves a good dynamic balancing effect, and has the merit of practical engineering application.

Roly-poly inspired tribo-electromagnetic energy harvester toward sustainable ocean energy harvesting

With the increasing global population, the demand for energy has also risen significantly. However, the utilization of fossil fuels for the purpose of energy production has resulted in the release of carbon emissions, accelerating the global warming. Therefore, the demand for carbon-free and renewable energy sources, which can replace the fossil fuels, is growing. In this study, a roly-poly-structure-inspired hybridized energy generator (RPHG) is demonstrated by combining a roly-poly triboelectric nanogenerator with an electromagnetic generator. By utilizing the RPHG, multiple vibrations can be induced from an external force due to the recovering force originated by the roly-poly structure of the RPHG. Consequently, the RPHG is capable of harvesting multiple vibrations from a single input vibration. To optimize the electrical performance of the RPHG, the effects of the substrate shape and the number of polytetrafluoroethylene balls into the electrical output is investigated. Also, the effect of the center of gravity on the electrical output generated from the RPHG is theoretically and experimentally confirmed. As a result, the average vibration number is increased from 2.6 to 25.1 with the 20 polytetrafluoroethylene balls when the tilted substrate with a tilted angle of 170° is applied to the RPHG, compared to the electrical output is generated from the RPHG with a flat substrate. The synergistic effect of the hybridization is demonstrated by comparing the charging speeds of a capacitor and the RPHG shows the fastest speed for charging the capacitor. Furthermore, our RPHG generates 2.45 and 19.29 times higher electrical output than the roly-poly triboelectric nanogenerator (RP-TENG) and electromagnetic generator, respectively. The proposed RPHG demonstrates the 195% higher conversion efficiency in terms of energy compared to the power owing to its unique structure. Also, although the RP-TENG and TENG without roly-poly structure (NRP-TENG) generate similar electrical power, the RP-TENG generates 242% higher electrical energy than NRP-TENG, showing the great potential to harvest the mechanical energy due to the roly-poly structure. As an application, a self-powered ocean wave monitoring system is implemented using the RPHG and it successfully detects strong, calm, and gentle waves. These results show the great potential of the RPHG to harvest vibration and ocean wave energy. Hence, we expect our RPHG to be a promising energy-harvesting solution for generating carbon-free energy.

An analysis of vibration signals is conducted to monitor the condition of the clutch of a centrifugal pump, employing ISO 10816 standards

Vibration in the shaft of a centrifugal pump arises from various factors, including the spacing between clutches, belt thickness, width, and their positioning within the clutch assembly. Vibration serves as a vital diagnostic tool for assessing machinery, offering insights into both motion and translation. Understanding vibrations and analyzing corresponding data are essential for effective maintenance and troubleshooting protocols. By leveraging this knowledge, companies can mitigate downtime, enhance productivity, and extend the operational lifespan of their machinery. Vibration stems from cyclic forces acting upon machine components, triggering energy release within the structure and resulting in oscillations. Excessive vibration not only generates noise but also compromises pump performance and jeopardizes critical components, notably the shaft and bearings. The objective of this study is to monitor and analyze vibration in centrifugal pumps equipped with modified belt connections. Various configurations of belt thickness, width, distance, and positioning were explored. Real-time data was gathered using accelerometer sensors to capture X, Y, and Z-axis values, subsequently converted from analog to digital format. Among the configurations tested, the Outside-Inside belt positioning, with belt dimensions of 6.5mm thickness, 150mm width, and a 40mm distance, exhibited the lowest average vibration value at 8.72mm/s. However, according to ISO 10816 standards, this measurement falls within the unsatisfactory category, indicating the need for further refinement in pump design and maintenance practices.

Origami-Inspired Vibrotactile Actuator (OriVib): Design and Characterization.

The use of vibrotactile feedback, in place of a full-fledged force feedback experience, has recently received increased attention in haptic communities due to their clear advantages in terms of cost, expressiveness, and wearability. However, designers and engineers are required to trade off a number of technical challenges when designing vibrotactile actuators, including expressiveness (a wide band of actuation frequency), flexibility, and the complexity of the manufacturing process. To address these challenges, we present the design and characterization of an origami-inspired flexible vibrotactile actuator, named OriVib, with a tunable resonance frequency (expressiveness), an origami-inspired design (flexible, soft contact with the human body), and a streamlined manufacturing process (low-cost). Based on its characterization, the fabricated OriVib actuator with 54 mm diameter can produce up to 1.2 g vibration intensity where the vibration intensity increases linearly from 6-11 V input. The resonance frequency is tunable through the characteristic diameter (the resonance frequency decreases in an almost inversely proportional fashion as the diameter increases). As for the thermal signature, the OriVib actuator maintains its temperature below 38 oC when actuated within 6-8 V. In terms of repeatability, the OriVib maintained an average vibration intensity of 0.849 g (standard deviation 0.035 g) for at least 2 million cycles. These results validate the effectiveness of the OriVib actuator to offer an expressive, low-cost, and flexible vibrotactile actuator.

Comparative Analysis of Public Transportation Comfort in Addis Ababa: Objective and Subjective Performance Metrics

Passenger comfort significantly influences commuter satisfaction and mode preferences in urban transportation systems. To maintain competitiveness and attract more passengers, conducting continuous performance evaluations based on key performance indicators is commendable. Therefore, this study is aimed at conducting a mode‐wide comfort performance evaluation and comparisons to identify the strengths and weaknesses of respective mass transport alternatives found in Addis Ababa, Ethiopia. The study employs a comprehensive approach by integrating both subjective surveys and objective measurements on key comfort determinants, including in‐vehicle passenger loading, travel time, vibration, and sound, across five transport modes: minibus taxis, midi buses, PSETSE, Anbesa City Bus Service Enterprise (ACBE), and Sheger Mass Transport Enterprise (SMTE). Analysis of variance (ANOVA) reveals variations among transport modes, with minibus taxis emerging as the most comfortable, featuring a travel time of 1.7 min/km, 2.6 min/km during off‐peak and peak times of the day, respectively, and an average of 1.13 passengers per seat in both periods of the day. In contrast, midi buses are identified as the least comfortable, characterized by elevated noise production (77.46 and 80 dB) and an average vibration rating of 3.9 and 4.2 at peak and off‐peak periods of the day. Following midi buses, the ACBE exhibits the highest passenger loading and travel time (2.113 and 1.548 passengers per seat and takes 4.2 and 3.34 min) to cover 1 km during peak and off‐peak periods, respectively. The holistic evaluation demonstrates an average correlation of 81.75%, indicating a strong alignment between peak‐hour objective and subjective assessments. This could help commuters make relevant mode choice decisions and transport companies make market‐oriented decisions in this competitive environment.

Vibratory Impact of 3 Different Ambulance Suspension Systems on the Simulated Neonate and Health Care Provider During Normal Driving Conditions

ObjectivePatients and health care providers experience varying degrees of vibration during interfacility ground transport. The impact of vibration on term and preterm neonates may result in physiologic instability and increased risk of intracranial hemorrhage, whereas the impact on health care providers has been shown to include an increase in perceived and physiologic stress levels and may contribute to chronic back and neck pain. This study aimed to evaluate 3 common ambulance suspension systems and the corresponding vibratory impact produced during typical interfacility driving conditions on adult caregiver and neonatal patient mannequins. MethodsType 3 ambulances with air, liquid, and traditional suspensions were evaluated using various driving tests to simulate typical road conditions. Vibrations were measured using triaxial accelerometers placed on the chassis, upon the head of a seated caregiver mannequin in the ambulance bench seat, and the head of a neonatal mannequin supine and secured in an isolette. Data analysis included the average vibration frequency, root mean square values, and maximum vibration amplitudes. ResultsThe results showed that the supine neonatal mannequin experienced the highest vibration frequency and amplitude in the vertical (x) direction, whereas the adult caregiver mannequin experienced higher vibration frequencies in both parallel (y) and lateral (z) directions and the highest vibration amplitude in the y direction. The liquid suspension system consistently demonstrated the lowest vibration levels in all driving conditions and directions, whereas traditional suspension had the highest values. ConclusionThis study provides important insights into the vibrations incurred by simulated neonatal patients and health care providers during ambulance transport. The directional vibration frequency and amplitude differ between a neonatal mannequin and an adult mannequin when placed in typical positions with typical restraints during varied ambulance driving conditions. In all directional movements and driving conditions, a liquid suspension system decreases vibration frequency and amplitude more than air or traditional systems. The live patient and caregiver impact of these results should be further investigated.

Numerical analysis of the effect of trench on indoor vibration adjacent to railway ground line

By establishing a 3D finite element numerical simulation analysis model of railway-soil-trench-building, the accuracy of the simulation analysis model is verified using on-site measured data of surface vibration attenuation law. Install vibration isolation trenches with different depths at different locations between the building and the railway, and analyze and compare the impact of indoor vibration in different situations. The results indicate that; The surface vibration caused by railways attenuates rapidly around 30m~76m from the line, and then shows a slight amplification trend around 120m. The surface vibration near the railway is mainly concentrated in the range of 15-90Hz; The vibration reduction effect of trench on different indoor rooms in buildings varies greatly. By optimizing the parameters of trench, the average indoor vibration reduction effect can be close to 5dB, and the vibration reduction effect of trench at different positions varies greatly. The increase in trench from 6m to 12m increases the indoor vibration isolation effect.

Design and experiment of a soybean shaftless spiral seed discharge and seed delivery device

When the driven stubble-breaking and anti-blocking no-till planter operates in the Southwest China, the stubble-breaking blades will impact with the ground as they cut through the soil and straw stubble, causing the planter to vibrate. This results in poor performances of the seed discharge by seed discharger and the seed guide by the seed guide tube. Based on the principle of spiral conveying, a soybean shaftless spiral seed discharge and seed delivery device was designed. The optimum seed filling size and speed range of the spiral blade were obtained by analyzing the size, force, and motion of soybean seeds of "ZhongHuang 37". The quadratic regression orthogonal rotation test and response surface method were used to analyze the operating parameters of the shaftless spiral seed discharge and seed delivery device by joint EDEM (Discrete Element Method)-RecurDyn simulation. The optimum parameters were obtained: the spacing of spiral was 11.4 mm, spiral outer radius was 5.5 mm, spiral inner radius was 2.9 mm and rotation speed was 10.4 r·s−1. Based on simulation and optimization results, the device was trialed and its field performance was tested. The results showed that at a surface slope of 16.1°, an average surface flatness of 8.9 cm, an average planter vibration frequency of 75.2 Hz, and an average amplitude of 7.2 mm, the average seeding qualification index, multiple index, missing seeding index, and damage index of the shaftless spiral seed discharge and seed delivery device were 92.6%, 5.03%, 2.4% and 0.92%, respectively, which were in line with the local agronomic requirements. The designed soybean shaftless spiral seed discharge and seed delivery device meets the requirements of the quality of no-till seeding and can provide a reference for the design and improvement of seed discharger and seed guide tube under poor ground leveling and long-distance seed delivery conditions.

Hydrodynamic Response of a Large-Scale Mariculture Ship Based on Potential Flow Theory

The marine fishery will be the main form of the marine economy in the future. Simulating a hydrodynamic response under normal and extreme working conditions is the main means of structural analysis and design of a mariculture ship. In this paper, a simulation methodology is proposed based on potential flow theory, focusing on a semi-submersible large-scale mariculture ship with a rigid frame. Abaqus/Aqua 2020 software is used to establish a full-scale dynamic analysis model of the fishery. In the simulation, a nonlinear implicit integration method is applied, and the non-deterministic boundary conditions of the floating body are optimized using dynamic equilibrium principles. By varying the wave and flow conditions, the variations in mooring forces, vibration amplitudes, and average vibration values are analyzed. Furthermore, the dynamic changes in the overall spatial displacements of the fishery, characteristics of longitudinal and vertical oscillations, and mid-span deflections are analyzed. It is concluded that the mooring force is linearly correlated with the flow velocity, that a higher wave increases the longitudinal oscillation amplitude, and that a longer wave period leads to higher mooring forces and longitudinal heaving amplitude. These dynamic response and displacement results of the mariculture ship are expected to provide a basis for its design and safety assessment.

Prediction of low frequency vibration propagation from operating rail tunnels

Predicting the propagation of vibrations from rail tunnels is important for quantifying and mitigating the environmental impacts of operating railways. In the general case, vibrations propagating from rail tunnels are attenuated by material damping and geometric effects. Often these effects are aggregated in empirical or numerical models which offer little insight into the physical behaviors that are involved and may be limited in terms of their applicability according to frequency range and tunnel-receiver geometry. This paper examines the aspects of low frequency vibration propagation from rail tunnels that are of relevance to predicting tactile vibration impacts and the influence of operating railway vibrations on sensitive imaging equipment. Fundamental geometric considerations and numerical models are used to determine the influence of pseudo-static effects, source-receiver geometry, layered ground and material damping effects, and the relationship between average and maximum vibration levels that are dependent upon source-receiver distance.

Analysis of the Vibration Characteristics and Vibration Reduction Methods of Iron Core Reactor

Series iron core reactors are one of the most commonly used electrical equipments in power systems, which can limit short-circuit currents and suppress harmonic waves from capacitor banks. However, the vibration of the reactor will not only generate noise pollution but also diminish the service life of the reactor and jeopardize power system safety. In order to reduce the vibration noise in the core disc region of the reactor, the vibration characteristics of a core reactor are calculated by modifying the anisotropy parameters of the Young’s modulus of the core disc lamellar structure and introducing the core magnetostriction effect based on the simulation analysis method of electromagnetic and mechanical coupling. A detachable single-phase series core reactor model is established, and the validity of the simulation calculation is measured and verified. At the same time, from the perspective of improving the air gap size of the series core reactor and the arrangement of electrical steel sheets, the corresponding iron core vibration reduction scheme is given. The average vibration reduction in the reactor is about 11.6% after comprehensive improvement according to the vibration reduction scheme, which provides an effective method for realizing the vibration and noise reduction in the reactor.