Vibration Attenuation Characteristics Research Articles

Attenuation of blast-induced vibration on tunnel structures

The blast-induced vibration during excavation by drilling and blasting method has an important impact on the surrounding structures. In particular, with the development of tunnel engineering, the impact of blasting vibration on tunnel construction has attracted extensive attention. In this paper, the propagation attenuation characteristics of blast-induced vibration (PPV, peak particle velocity) on different tunnel structures were systematically studied based on the field monitoring data. Initially, the attenuation characteristics of blasting vibration PPV on lower bench surface, side wall of the excavated tunnel and the closely spaced adjacent tunnel were investigated. Subsequently, the capacity of several widely utilized empirical prediction equations to estimate the PPV on tunnel structures was examined, along with a comparative analysis of their prediction accuracies. The research findings indicate that it is feasible to predict the PPV on the tunnel structures by using empirical equations. The attenuation characteristics of blasting vibration PPV are different in different structures and directions. While the prediction accuracies of the empirical equations vary, the discrepancies are minimal. The principal variation among these equations lies in the site-specific coefficients k, β, λ, highlighting the differential impact of structural and directional considerations on the predictive efficacy. Based on the empirical equation and safe PPV provided by the blasting vibration safe standards on tunnels of China (GB6722-2014), and with considering the influence of all structures and directions, obtained the safe distance of blasting vibration in the tested tunnel project should be larger than 20.28∼18.31 m, 18.31∼161.16 m and 16.16∼13.75 m for blasting vibration frequency located in ≤ 10 Hz, 10-50 Hz and > 50 Hz.

Low frequency vibration reduction bandgap characteristics and engineering application of phononic-like crystal metaconcrete material

Metaconcrete, as a new type of composite material with vibration attenuation characteristics, is formed by replacing traditional coarse aggregates with a heavy metal core wrapped with an elastic soft coating and mixing with cement mortar. However, due to the high bandgap frequency and narrow bandgap width, it is greatly limited in the engineering application of low frequency vibration control. In order to broaden the range and number of elastic wave bandgap of metaconcrete materials and solve the problem of low frequency vibration, a novel three-component cement-based phononic-like crystal model is proposed based on local resonance theory, and phononic-like crystal metaconcrete vibration reduction material is developed accordingly. Secondly, the band structure, bandgap mechanism, and frequency response function of the phononic-like crystal metaconcrete are calculated and analyzed, and indoor tests of the phononic-like crystal metaconcrete are conducted. Finally, a phononic-like crystal metaconcrete subway track bed is prepared using the developed phononic-like crystal metaconcrete material, and applied to the practical subway engineerings to solve the low frequency vibration problem generated during subway operation. The results show that the phononic-like crystal metaconcrete opens 6 low frequency bandgaps in the frequency range of 200 Hz, and the attenuation values are mostly above 10 dB in the frequency range of the bandgap, and the attenuation effect is good. Meanwhile, the on-site monitoring results show that the phononic-like crystal metaconcrete subway track bed has good low frequency vibration reduction effect in the 200 Hz frequency range. The maximum value of the one-third octave insertion loss of the tunnel wall is 13.22 dB, the maximum vertical Z-vibration level difference of the tunnel wall is 5.052 dB, and the maximum vertical frequency division vibration level difference of the tunnel wall is 5.926 dB. The maximum value of the vertical frequency division vibration level difference in the frequency range of 4–200 Hz is 13.87 dB, and the average value is 5.74 dB. The relevant research results of this paper provide a new technical approach to solve the problem of low frequency vibration in subway engineering and other engineering construction, breaking through the traditional vibration reduction control technology of civil engineering structures, and providing new idea and method for long-term vibration reduction and application of engineering structures.

The Vibration Attenuation Characteristics of Dynamic Vibration Absorbers Array for Tuned and Mistuned Bladed Disk

Abstract Dynamic vibration absorbers array (DVAA) is a newly developed and promising technique for vibration attenuation of integrally bladed disk (blisk) by mounting underneath the disk. In this paper, the vibration attenuation characteristics and energy dissipation mechanism of DVAA for tuned and mistuned blisk are parametrically studied, where the viscous and frictional damping are both considered. The lumped parameter model of a blisk is employed for the convenience of parametrical study. Analytical power flow formulas within the blisk–DVAA system are derived to characterize the dynamic interaction between blisk and DVAA. Four typical modes of a blisk with different nodal diameters and deformation characteristics are selected to evaluate the performance of DVAA. Then, the effects of the mass ratio, the frequency ratio and the damping ratio of DVAA on the vibration of tuned and mistuned blisk are addressed. Numerical results show that a light DVAA can significantly mitigate the resonant amplitudes of the tuned and mistuned blisk. Such damper is effective for the modes with different modal characteristics and can provide robust vibration attenuation performance against random mistuning.

Experimental study on vibration suppression for robotic milling using an MRE absorber

During the robotic milling process, vibration is one of the main factors that affect the machining accuracy and surface quality due to the low stiffness of the robot structure. Intelligent material, magneto-rheological elastomer (MRE), owns the features of adjustable stiffness, reversible and fast response, has been gradually used for vibration suppression. Therefore, to suppress the forced vibration for robotic milling, this paper used the principle of vibration absorption and combined it with MRE material to design a snubber. A series of excitation and milling experiments were carried out to evaluate its vibration attenuation characteristics. In the excitation experiment, sine signals with frequencies of 40 Hz, 42.02 Hz and 60 Hz with the same amplitude of 5 N were applied to the MRE absorber. In the milling experiment, the dominant frequencies under speeds of 800 RPM, 840 RPM and 1200 RPM were analyzed first. Then, the vibration mitigation characteristics of the MRE absorber during robotic milling of aluminum alloy were explored by adjusting the current. Experimental results showed that under the action of MRE absorber, the acceleration responses are suppressed effectively. In detail, after tuning the current, the amplitude and the root mean square of vibration acceleration in three directions of sinusoidal excitation could be suppressed by more than 19.23% and 7.35% correspondingly. The power spectral density value of the peak frequency could be reduced by more than 69.13%. In milling experiments, the MRE absorber also achieved certain vibration absorption effects. Furthermore, the surface roughness of the workpiece was also fallen by more than 16.51% which provides support for further engineering application in the field of robotic milling. Undoubtedly, the absorber needs further optimization to achieve better vibration suppression ability and a larger working bandwidth.

Vibration Control of Fgm Thick Shells Using Higher Order Shear Deformation Theory

Analytical solutions of Functionally Graded Material (FGM) shells with embedded magnetostrictive layers are presented in this study. These magnetostrictive layers are used for the vibration suppression of the functionally graded shells. The higher order shear deformation theory (HSDT) is employed to study the vibration suppression characteristics. The exact solution for the FGM shell with simply supported boundary conditions is based on the Navier solution procedure. Negative velocity feedback control is used. The parametric effect of the location of the magnetostrictive layers, material properties, and control parameters on the suppression effect are investigated in detail. Higher order shear deformation theory has significant influence on prediction of vibration response of thick shells. Further, it is found that (i) the shortest vibration suppression time is achieved by placing the actuating layers farthest from the neutral plane (ii) the use of thinner smart material layers leads to better vibration attenuation characteristics, and (iii) the vibration suppression time is longer for a smaller value of the feedback control coefficient.

Vibration Control of Composite Thick Shells Using Magnetostrictive Material and Higher Order Shear Deformation Theory

Analytical solutions of laminated composite shells with embedded actuating layers are presented in this study. The actuating layers are used to control natural vibration of laminated composite shell panels. The first order shear deformation theory (FSDT) and higher order shear deformation theory (HSDT) for shells are used to represent the shell kinematics and equations of motion. The exact solution for symmetric laminated shells with embedded actuating layers under simply supported boundary conditions is obtained using the Navier solution procedure. Negative velocity feedback control is used. The parametric effect of the position of the magnetostrictive layers, material properties and control parameters on the vibration suppression are investigated in detail. It is found that (i) the shortest vibration suppression time is achieved by placing the actuating layers farthest from the neutral axis (ii) using thinner smart material layers leads to better vibration attenuation characteristics and, (iii) the vibration suppression time is longer for a lower value of the feedback control coefficient. For thicker shells HSDT predicts larger amplitude of vibration and longer vibration suppression time as compared to FSDT predictions.

Using Structural Intensity Approach to Study the Energy Attenuation in Metamaterial Plate

Metamaterials have been extensively studied because of their bandgap characteristics, which can be used in vibration isolation. Current studies on the effect of vibration attenuation in metamaterials mainly focus on vibration amplitude, velocity, and acceleration. The structure intensity is a more effective approach to evaluating vibration. In this study, the structural intensity method is adopted to describe the vibration suppression effect of elastic metamaterial plates. The energy flow density in the stop band and the passband in the metamaterial plate can be obtained, and the mechanism for the vibration blocking of the metamaterial plate in the stop band is revealed. The study demonstrates that the power flows around the vibration source, which is calculated by the loop integral of structure intensity around the vibration source, can be used to describe the attenuation and transmission characteristics of vibration.

Vibration attenuation characteristics of squeeze film dampers in spiral bevel gear systems

A central drive bevel gear system of aero-engines extracts power from a high-pressure rotor. The high speed of the high-pressure rotor aggravates the gear system's vibration. This work adopts squeeze film dampers (SFD) as damping devices to suppress excessive vibration of the spiral bevel gear rotor system. This paper establishes the general Reynolds equation of SFD and calculates the nonlinear oil-film force of SFD in real-time based on the finite element method. Besides, the finite element method and Timoshenko beam element are employed to model the flexible gear shaft. Then, the dynamic model of the spiral bevel gear system supported by SFDs is established, including the nonlinear oil-film force of SFD and time-varying meshing stiffness of the gear system. The dynamic response of the spiral bevel gear system is analyzed theoretically and experimentally to study the vibration attenuation characteristics of SFD. The findings indicate that SFD can effectively suppress the vibration amplitude of the system at high speeds. The theoretical analysis and experimental amplitude are within an order of magnitude, and the changing trend is consistent.

Investigation of the impact of environmental conditions on the vibration mitigation performance of typical commercial under ballast mat materials

The performance of under ballast mats (UBMs) in mitigating vibrations caused by regular rail traffic has been the subject of numerous studies. However, most of these studies have focused on the impact of design and material properties on the vibration attenuation characteristics of UBMs, with little attention paid to the influence of environmental factors such as temperature, freeze/thaw cycling, and weathering. In this paper, we present the results of an investigation into the effect of environmental conditions on the vibration mitigation performance of typical commercial UBM materials including rubber and closed cell polyurethane elastomer. We conducted controlled laboratory experiments in which we exposed UBM samples to a range of simulated environmental conditions. The results of these experiments were compared to the results of tests conducted under standard laboratory conditions to evaluate the impact of the environmental conditions on the vibration attenuation performance of the UBMs. The results of this investigation have important implications for the design and selection of UBMs for use in railway systems, particularly in regions with extreme environmental conditions.

Study on vibration characteristics of badminton racket embedded in acoustic black hole structure

According to the principle of acoustic black hole effect, a badminton racket design method of embedded one-dimensional acoustic black hole structure was proposed. Based on the finite element simulation analysis, the broadband vibration attenuation characteristics of one-dimensional acoustic black hole structure were studied. The results show that this structure can not only ensure the light quality of the system, but also achieve good vibration reduction effect. In the absence of damping, a small truncation can make the reflection coefficient increase rapidly, and the larger the truncation, the worse the vibration suppression effect. The combination form of one-dimensional acoustic black hole structure and damping material shows obvious formant suppression in the wide band range, and the larger the thickness of the damping layer and the closer the location of the damping layer to the tip, the more obvious the damping effect.

Investigation on band gap mechanism and vibration attenuation characteristics of cantilever-beam-type power-exponent prismatic phononic crystal plates

This study proposes a novel phononic crystal (NPC) configuration composed of power-exponent prismatic phononic crystal (EPC) and cantilever beams to address the vibration problem of the ship plate structure. Through the dispersion curve, it is found that NPC has complete flexural band gaps of low-, medium-, and high-frequency. The medium-frequency and high-frequency band gaps are the coupled band gaps induced by local resonance under the superimposition between the resonance of cantilever beams and the energy concentration effect in the primary structure. It is found that the addition of cantilever beam can make EPC produce low-frequency, and medium-frequency band gaps and broaden high-frequency band gap. Changing the parameters of the cantilever beam can adjust the low-, medium-, and high-frequency band gaps at the same time. Changing the parameters of the power index prism can adjust the medium-frequency and high-frequency band gap without changing the low-frequency band gap. The present simulation and model tests validated the above conclusions. Compared with the traditional embedded ABH model, NPC cannot weaken the structural strength with greater flexibility in application, suggesting broad application prospects in ship structure engineering. The present research results can support the vibration control of ship structures.

The time-frequency characteristics analysis and prediction of ground vibration near a subway station

This paper presents the time-frequency characteristics of ground vibrations near subway stations through field tests and analyses. More than 15 ground vibration measurement points are set up in the longitudinal and transverse directions of the track near a subway station. Overall, the ground vibration level (VLzmax) above the tunnel is approximately 73 dB on the border between the station and mainline, while it attenuates to 63 dB away from the tunnel by approximately 30 meters; the dominant frequency in the mainline area is approximately 63-80 Hz. The results in the longitudinal direction show that the ground vibration increases rapidly as the train drives away from the station because of the train speed growing, and VLzmax is less than 10 dB between the station and near the mainline area, while the dominant frequency in the mainline area is higher than that in the station area. The attenuation rate of the ground vibration in the transverse direction for the mainline area is faster than that for the station area. The power distribution law y=Ax^(-α) can describe the vibration attenuation characteristics, and its "peak and long tail effect" and "scale-free characteristics" can predict the vibration at any position by measuring two specified locations.

Analysis of longitudinal and torsional vibration of mining scraper conveyor under the over bending section working condition

Considering that the scraper will produce longitudinal and torsional pendulum vibration when passing through the bending section, and have a great influence on the motion characteristics of the scraper conveyor, this paper studies the longitudinal and torsional pendulum coupling vibration characteristics of the scraper conveyor under the working condition of over-bending section for the first time. Firstly, the simplified model of torsional pendulum vibration of scraper chain system is established based on Voigt model and point-by-point tension method. Then, the change law of scraper group vibration and chain tension under the condition of scraper bending is studied. Thirdly, through the influence area and attenuation characteristics of torsional pendulum vibration, the thumbnail model of torsional pendulum vibration is constructed. Finally, the longitudinal and torsional pendulum coupling vibration dynamic model of the scraper chain system is constructed based on the torsional pendulum vibration abbreviation model, and the overall longitudinal and torsional pendulum vibration characteristics of the scraper conveyor are studied when the scraper is over the bending section. The conclusion of this paper provides a theoretical basis for better understanding the operation characteristics of scraper conveyor in coal mine.

Influence of Dynamic Accuracy Constraints of Manipulator of Wafer Transmission Robot on Scheduling and Control of Single-Armed Cluster Tools

The wafer transfer robot is a key part of integrated circuit equipment which performs the transit of wafers precisely, quickly and steadily. The dynamic accuracy of the manipulator of the wafer transfer robot directly affects the quality of transferring and processing wafers and even the scheduling and control of the cluster tools. Thus, it is essential to study the influence of the dynamic accuracy of the manipulator of wafer transmission robots on the scheduling and control of cluster tools. In this paper, single-arm cluster tools are taken as the research object. The horizontal torsional vibration equations of the manipulator of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta $ </tex-math></inline-formula> robot are constructed, and the torsional vibration attenuation characteristics of the manipulator are analyzed. Based on the torsional vibration equations, the intrinsic relationships between the dynamic accuracy of the manipulator and the waiting times of the manipulator are explored when the manipulator loads and unloads the wafers. Then the two-stage approach is proposed for the scheduling and control of single-arm cluster tools. The first stage determines the minimum waiting times of the manipulator according to the intrinsic relationships between the dynamic accuracy of the manipulator and the waiting times of the manipulator when the manipulator is waiting for loading and unloading wafers in each processing module and load lock. The second stage achieves the scheduling optimization and control of single-arm cluster tools with dynamic accuracy constraints and wafer residency time constraints by establishing a mathematical programming model for the scheduling and control of single-arm cluster tools. Finally, illustrative examples are presented to analyze the influence of the dynamic accuracy of the manipulator on the scheduling and control of single-arm cluster tools.

Vibration attenuation characteristics of finite locally resonant meta beam: Theory and experiments

Dynamic vibration absorbers are of utmost importance in civil and mechanical engineering applications; however, their intricate mechanisms are always challenging for practical realization. This paper investigates the vibration suppression characteristics of a base-excited cantilever beam having a series of lumped masses and spring–mass resonator systems. Both analytical and experimental investigations are carried out to compare the transmittance of the dynamic displacement response of the entire system. In the analytical method, a single unit cell comprises an Euler Bernoulli beam attached by a lumped mass and a spring–mass resonator (SMR) system. The transfer matrix method establishes the force–displacement relationship between each unit cell. Furthermore, experiments were conducted by applying a monochromatic frequency to the beam and detecting transmitted vibrations at the beam and SMR systems. The experimental results are validated with the analytical results, providing essential confidence in our proposed methodology. Moreover, several parametric studies were also conducted to obtain the rationale for the variation in the number and location of SMR systems in the vibration characteristics of the entire system.

Enhancement of the vibration attenuation characteristics in local resonance metamaterial beams: Theory and experiment

Enhancing vibration isolation with local resonance metamaterials has attracted widespread attention due to the low-frequency band gap. However, the narrow band gaps limit its application. To improve vibration suppression properties over a wide frequency range under the constraints of space and mass in engineering, this paper presents the modeling techniques and design strategies for a local resonance elastic metamaterial beam with multiple resonators. The local resonance sub-system contains multi-degree-of-freedom resonators and is periodically mounted on the elastic beam. Two special cases, the elastic metamaterial beam with one-degree-of-freedom local resonator sub-system (1-DOF) and two-degree-of-freedom local resonator sub-system (2-DOF) are used to investigate the vibration attenuation characteristics in detail. Results are presented in the form of attenuation constant, which are calculated by the extended plane wave expansion (EPWE) method. The effects of frequency spacing, damping and mass ratio on the vibration attenuation characteristics of elastic metamaterial beams are comprehensively investigated. The results show that a wider and more stable attenuation range can be obtained by reasonably adjusting these three parameters. Finally, the comparison of experimental and simulation results demonstrates that the design strategies proposed in this paper can broaden the vibration attenuation regions. The theoretical approaches and design schemes can provide effective guidance for passive vibration control.

Band-stop characteristics of a nonlinear anti-resonant vibration isolator for low-frequency applications

In order to broaden the vibration attenuation bandwidth of passive isolation systems in low-frequency applications, a nonlinear anti-resonant vibration isolator was studied by coupling a lever-type vibration isolator with a nonlinear vibration absorber. By appropriately designing the structural parameters, a wider double-attenuation stop-band emerges from the coupling of the levered mass and the absorber mass. Theoretical results show that the bandwidth of the proposed NL-AVI is much wider than that of an existing lever-type vibration isolator. A parametric influence investigation shows that the transmissibility and width of the stop band can be flexibly designed with structural parameters. The cubic nonlinearity of the vibration absorber has the effect of shifting the anti-resonant frequency and the resonant peak to higher frequencies, thereby increasing the stop band width. The proposed nonlinear anti-resonant vibration isolator provides a distinctive mechanical mechanism for realizing a combination of band transmissibility and width in the vibration attenuation characteristics and has been successfully validated by experimental prototypes for their advantageous performance in low-frequency vibration isolation.

Analysis of flexural and torsional vibration band gaps in phononic crystal beam

Phononic crystals (PCs) play an important role in the reduction of vibration within a targeted frequency range. Most research of the one-dimensional PCs focuses on the properties or applications of the flexural band gaps; however, practically, the broadband environmental excitations also induce the torsional vibration. Hence, this paper studies a two-degrees-of-freedom local resonance (2DOF-LR) phononic crystal, which can both suppress the propagation of flexural and torsion waves in the same frequency range. To improve the computational efficiency, the Timoshenko theory with a modified transfer matrix (MTM) approach is used for flexural vibration band structure analysis. Through the finite element method (FEM), the vibration attenuation characteristics of the structure within the band gaps are verified. A comprehensive study is conducted to investigate the effects of geometric and material parameters on the attenuation characteristics of the phononic crystal. Finally, a prototype of the proposed phononic crystal is fabricated for the vibration experiment. It is worth noting that a novel experimental setup using the lever principle is designed in this paper to verify the torsional band gap. The frequency ranges of the experimental vibration attenuation match well with the numerical results.

Experimental investigation for novel hybrid journal bearing with hydrostatic squeeze film and metal mesh damper in series

PurposeThis study aims to present a novel hydrostatic squeeze film-metal mesh journal bearing (HS-MMJB), which uses both hydrostatic squeeze film damper (HSFD) and metal mesh damper (MMD), to suppress the vibration of rotor-bearing systems.Design/methodology/approachThe lubrication equations were introduced to calculate the dynamic characteristics of HS-MMJB, and the response analyses of rotor systems were carried out. Experiments were conducted to study the vibration reduction of a rotor system with HS-MMJB. In addition, experiments for different oil supply pressures in the HS-MMJB were conducted.FindingsThe theoretical and experimental results show that the HS-MMJB exhibits excellent damping and vibration attenuation characteristics. Moreover, the stability of the rotor system can be improved by controlling the oil supply pressure.Originality/valueThere is a dearth of research on vibration characteristics of rotor system support by journal bearing combining HSFD and MMD. Moreover, the active oil pressure control is implemented to improve the stability of rotor system.

Attenuation and propagation characteristics of railway load-induced vibration in a loess area

The long-term vibration caused by the operation of high-speed trains not only reduces the strength and stability of a roadbed but also affects infrastructure such as buildings along the line, resulting in a series of engineering–environmental problems. In this study, field tests were conducted to examine the ground vibrations caused by the operation of the Datong-Xi’an high-speed railway; three different line forms––viaducts, embankments, and embankment culverts––were considered. First, the propagation law and attenuation characteristics of environmental vibration caused by high-speed railways in typical loess areas were analyzed using time-domain and frequency-domain features. Second, based on the Bornitz model and combined with the measured data, the geometric attenuation coefficient and damping attenuation coefficient of the formula are discussed, and the optimized Bornitz model is used to predict the ground vibration caused by high-speed trains in a loess area. The results showed the following: (1) The ground vibration caused by high-speed train operation is a periodic excitation, and there is an obvious superimposition effect at the bogie of the train. The vertical vibration acceleration of the ground surface decays continuously as the distance from the vibration source increases. The dominant frequency also decreased with an increase in distance. (2) The geometric attenuation coefficient of the bridge and embankment sections decrease with an increase in the distance from the vibration source, and the overall attenuation is a power function. Different distances should be regarded as different types of vibration sources, and the damping attenuation coefficient differs at different measurement points. (3) The improved Bornitz model was used to predict ground vibrations caused by the operation of high-speed trains. A comparison with the measured data showed good agreement, explaining the amplification effect in the attenuation of ground vibration.