Vibration Isolation Effect Research Articles

Research on seismic performance of new bridge pier seismic reduction isolation system based on shaking table test

In view of the current poor seismic performance of bridges, this paper started with the vibration isolation and reduction mechanism of the bearing, and deduced the coordination relationship between the stress and the deformation of the bearing under the vibration isolation and vibration reduction working conditions. Combined with the shaking table test, the defect that the traditional rubber bearing has poor seismic isolation effect was analyzed. Based on this, a base-bearing double reduction system was proposed and its vibration reduction and isolation effect was compared with the traditional bearing. The shaking table test results showed that, compared with the traditional bearing, the proposed vibration reduction system had better energy dissipation effect and could weaken the apparent cracking damage of the pier under the action of earthquake. Under the 125 m/s2-750 m/s2 peak acceleration excitation of the EI-Centro wave, the proposed vibration reduction system could greatly reduce the displacement variation of the upper main beam by 20 %-47 %. Moreover, the results of dynamic amplification factor measured at the corresponding height of the two types of piers also verified that the proposed base-bearing double vibration reduction system had greater competitiveness when the peak acceleration of seismic waves was less than 500 m/s2.

Research on the three degrees of freedom hysteretic mechanical model of floating rafts

A floating raft is a complicated multilayer vibration isolation system, which is often simplified as a two-degree-of-freedom viscous damping system in analysis. In order to research the influences of the hysteretic damping and the raft flexibility on the vibration isolation effect, a three-degree of freedom hysteretic mechanical model of the floating raft is established, and the impedance method is adopted to deduce the model of the force transmissibility of the floating raft. The analytic calculation methods of force transmissibility are given aiming at the low-frequency range, the resonance range, and the high-frequency range, respectively. Finally, the influence rules of damping, mass, and stiffness on force transmissibility are analyzed aiming at the value range of parameters of most floating rafts. The main analysis conclusions are listed as follows: the analytic calculation equation for resonance frequency and resonance peak is accurate; the vibration isolation effect of the high frequency range is determined by the entire floating raft, the unconstrained raft, the inherent frequency of the equipment, the mass ratio between the raft and the equipment only; the hysteretic damping can reduce the force transmissibility at the place of the resonance frequency of the floating raft, which shall be maximized; the increase in the mass of the raft will reduce the force transmissibility during the frequency range above the inherent frequency of the equipment, but it will reduce the marginal benefit; the reduction in the stiffness of the isolator or the raft will reduce the force transmissibility during the frequency range above the inherent frequency of the equipment, and will increase the displacement of the equipment; with limited displacement, it is better to design the isolator and the raft according to the principle of equal stiffness.

Noise protection from diesel generator units in a residential construction territory

Introduction: The article deals with the issues of protection against noise and vibrations of engineering equipment, which spread into the residential area through ventilation shafts, and the problems of bringing noise to standards during the operation of diesel generators. The purpose of this work was the development and implementation of methods and means to reduce the vibration levels of the walls of the technological room in which the diesel generator set was installed. Materials and Methods: The article presents studies using computational and graphical and resonance and statistical methods. Measurements of the noise level from the operation of a diesel generator located on the site of the residential buildings under consideration, as well as in residential premises, were carried out. Results and Discussion: The estimated calculation showed that the noise levels on the territory do not meet the requirements of sanitary standards. The results of measurements of the sound pressure level before and after noise protection measures for an individual living space gave an assessment of the qualitative and quantitative ratio of the accepted and new types of measures and materials. Conclusions: The effectiveness of vibration isolation of engineering equipment depends on the applied vibration isolation scheme; the wrong choice of vibration isolation scheme can lead to an uncontrolled increase in the amplitude of vibrations of the foundation of engineering equipment. To eliminate low frequencies, it is necessary to install vibration isolating supports under the foundation of the diesel generator set.

Modeling analysis of a novel hybrid 6-DOF vibration isolation platform for sensitive instruments

The inevitable vibration caused by normal operation of the spacecraft in orbit will interfere sensitive instruments, such as space telescope, reconnaissance camera, space interferometer. Serious vibrations affect the accuracy and reliability of the sensitive instruments, even cause flight mission failed. This paper presents a hybrid 6-DOF vibration isolation platform (HVIP) with six degree-of-freedom for active vibration isolation of the space sensitive instruments. The HVIP is composed of three orthogonal vibration isolation module, which composed of the active piezoelectric actuator and passive rubber isolator. The dynamic model of the HVIP is established based Lagrange equation approach. Finally, the numerical simulations are performed to verify the vibration isolation effect of the HVIP.

Enhanced energy dissipation benefit of negative stiffness amplifying dampers

Negative-stiffness devices are of rapidly increasing interest for high-performance vibration control. With a tuning spring in series, the negative-stiffness device forms an enhancement mechanism for the dashpot, named the negative stiffness amplifying damper (NSAD), which is much more efficient in dissipating energy than the viscous damper alone. Based on the observed enhancement phenomenon, this study reveals the theoretical basis of the energy dissipation enhancement benefit by deriving the analytical enhanced energy dissipation formula. The basic concept and physical realization methods for the negative-stiffness device are introduced, based on which the mechanical models of NSAD and NSAD-equipped structures are established for dimensionless response analysis. Following a stochastic framework, the stochastic responses of the NSAD-equipped structure are solved in closed form. Correspondingly, simple and easy-to-understand equations are derived and denoted as the “enhanced energy dissipation formula” to quantify each component's contribution in the NSAD explicitly. Inspired by the formula, a design framework with two strategies is proposed for NSADs with a synthetic consideration of the energy dissipation enhancement mechanism and target control performance. Following the design principle, detailed design formulae are derived in a simple form. Finally, a design procedure is provided and applied to a series of design cases for illustration. The results show that the energy dissipation enhancement mechanism enables NSADs to offer improved energy dissipation efficiency over conventional dampers without sacrificing the vibration isolation effect or the excessive damping force. The analytical formula clearly explains the theoretical basis by quantifying the NSAD components’ contribution to the vibration control and energy dissipation enhancement effects. Based on this newly explained benefit, the design framework successively provides a high-efficiency energy dissipation device that fulfills its intended control performance. In addition, the easy-to-use design formulae are derived for the new design strategy to allow the direct design of NSADs.

Performance and Optimization of a Dual-Stage Vibration Isolation System Using Bio-Inspired Vibration Isolators

This paper thoroughly investigates the performance and multi-parameter optimization of a dual-stage vibration isolation system with bio-inspired isolators (BI-DSVI) under different base excitations. The dynamic equations of the BI-DSVI are derived. Then, the optimization problem is defined, where three types of base excitation (translation and rotations around the two horizontal axes) are studied. The optimization results show that the vibration transmissibility can be greatly reduced (more than 30 dB) by multi-parameter optimization, and an optimal configuration of structural parameters exists for the bio-inspired isolators. The effective vibration isolation bandwidth is significantly widened. Finally, the paper thoroughly discusses the influence of the structural parameters of the bio-inspired isolators and the base excitation types on the vibration isolation performance. The parameter studies provide useful guidelines for the application of the bio-inspired isolator in dual-stage vibration isolation.

Research on design and characteristic of a new type of air suspension system with magnetic negative quasi-zero stiffness

This paper designs a quasi-zero stiffness suspension with an air spring and a magnetic spring in parallel to improve the vehicle ride comfort. The proposed new suspension does not change the overall layout of the air suspension or affect the handling stability, reducing the system’s natural frequency by a sound vibration isolation effect for a low-frequency vibration and finally improving ride comfort. The feasibility of quasi-zero stiffness suspension is verified by mathematical modeling of air spring and magnetic spring, and reasonable structural parameters are set for the simulation experiment. The 1/4 vehicle model with two degrees of freedom is built in MATLAB / Simulink. Select body acceleration, suspension working space, and tire dynamic load as evaluation indexes to test the comfort performance of the proposed suspension. The result shows that the proposed new suspension has a noticeable effect on reducing the acceleration of the vehicle body and significantly improves the vehicle ride comfort.

Low coherency of wind induced seismic noise: implications for gravitational wave detection

Seismic noise poses challenges for gravitational wave detection. Effective vibration isolation and methods to subtract unshieldable Newtonian noise (NN) are examples. Seismic arrays offer one way to deal with these issues by making use of correlations between seismic ground measurements and noise inside the detector. In this paper we find that wind induced seismic noise is incoherent and our results show that it can dramatically reduce the projected low frequency sensitivity of future gravitational wave detectors. To quantify this, we measure the coherence length of wind induced seismic noise from 0.06–20 Hz in three distinct locations: close to a building, among tall trees and in shrubs. We show that wind induced seismic noise is ubiquitous and reduces the coherence lengths from several hundred meters to 2–40 m for 0.06–0.1 Hz, from 60 m to 3–16 m for 1.5–2.5 Hz and from 35 m to 1–16 m around 16.6 Hz in the study area. This leads to significant loss of velocity resolution of the array for primary microseism and 5 times worse NN cancellation by Wiener filtering at 2 Hz, while it may not pose additional limitation to NN cancellation between 10–20 Hz.

Horizontal hollow pipes used as vibration isolation barriers: Numerical modelling and design optimization

Open trenches are one of the most popular vibration isolation techniques used to reduce the transmission of ground vibrations. Despite several advantages of this systems for isolating ground vibrations, the major drawback is the geotechnical instability of the trenches. To solve this issue, the author have created a novel approach that involves filling the open trenches with hollow pipes in specific pattern. This is a novel method for mitigating ground vibrations by burying hollow pipes horizontally. Through the use of three-dimensional (3D) finite-element modeling, the effectiveness of such hollow pipes in decreasing ground vibrations generated by harmonic stress excitation on the ground surface was investigated. Compared to open trench barriers and in-filled trench, these pipe assemblages have been demonstrated to be highly successful in reducing ground vibration transmission while addressing issues of instability and enhancing vibration isolation efficiency. In PLAXIS3D, a dynamic numerical model is developed, and the results are validated against available solutions. Then, an optimized design technique for wave barriers is developed, and explore the effect of layered soil on vibration isolation effectiveness of hollow pipes.

Dynamic response and vibration isolation of pipes inside a utility tunnel passing through nonhomogeneous soil under seismic action

An unreasonable design of the pipe support between a utility tunnel and the pipe can result in a large deformation of internal pipes under seismic action. In this study, aiming at the seismic response problem of pipes inside a utility tunnel passing through nonhomogeneous soil, a shaking table test and a finite element simulation were conducted. First, the boundary effect caused by the laminated shear box was studied, and the influences of the pipe acceleration, longitudinal and transverse relative slippages, the form of the pipe support, and the pipe material on the pipe deformation were analyzed. Finally, the attenuation effect of the acceleration peak response of the internal pipes and the attenuation law of the energy transmitted to the pipes were obtained. The results showed that the attenuation degree of the energy transmitted to the pipes was more than 80%; the longitudinal relative slippage of the pipes caused by the high-amplitude segment of the input acceleration was generally significant; the vibration isolation effect of the side-wall angle steel support on the pipeline was stronger than those of other supports. This paper provides a basis for the seismic design of pipelines inside a utility tunnel.

Mitigation of subway-induced low-frequency vibrations using a wave impeding block

The effective control of low-frequency vibrations induced by subway operation remains a problem, but wave impeding blocks (WIBs) have the potential to solve this issue. To investigate the vibration isolation behavior of WIB under subway loading, this study established a coupled track-tunnel-ground-WIB model using the two-and-a-half dimensional finite element method (2.5D FE). The effect of bedrock on wave propagation was first revealed by analyzing the eigenfrequencies of the soil layer with a tunnel. It was found that the bedrock reduced ground-borne vibrations with a frequency lower than the cut-off frequency of the soil layer. Based on this observation, the vibration isolation behavior of the WIB with different locations, embedding depths, material types, and dimension parameters was analyzed in detail. The WIB located beneath the tunnel invert (near-field active vibration isolation) exhibits a completely different behavior than that beneath the ground surface (far-field passive vibration isolation). The former can reduce ground vibrations in the entire ground surface, whereas the latter only works in a limited region directly above the WIB. The far-field vibration isolation effect is not sensitive to the vibration frequency and embedding depth, but the WIB dimension and rigidity have a significant impact. The near-field vibration isolation effect is most significantly influenced by the embedding depth, followed by the material property and dimension parameter. The WIB installed beneath the tunnel invert with a thinner embedding depth and stiffer rigidity more effectively isolates low-frequency vibrations induced by the subway.

Vibration properties of a knee bio-inspired nonlinear isolation structure

Inspired that the knee joint of birds can buffer the impact and vibration from the foot, a novel vibration isolator constructed by the Knee-Like structure (KLS) is proposed in this paper. Considering that the bones and muscles are very different in material strength, the leg bones are described by rigid rods and the muscles around the knee joint are described by the elastic components. Simulating the construction of the whole leg, in the bionic isolation structure, there are three adjustable structural parameters, which correspond to the angles for ankle and knee, and the length of the thigh. According to the dynamic model, the effects of structural parameters on linear and nonlinear coefficients and the widths for effective isolation bands are illustrated. By the transmissibility curves for different structural parameters by the Harmonic Balance Method (HBM), it discovers that the KLS bionic isolator has optimum design for the knee angle, different from the existing nonlinear isolation structure as the structural parameters monotonously affect the width of isolation band. Then, the analytical solution including transient and steady states are solved by the Method of Multiple Scales (MMS). For different frequency band excitation, the order determinations of excitation and nonlinearity are different. The comparison between the analytical solution and numerical simulation shows that the MMS is applicable for the asymmetric nonlinear nonautonomous dynamic system, and describes the buffering process and steady states for the vibration. The analysis of the proposed KLS bionic isolator not only illustrates the significant vibration isolation effectiveness for ultralow frequency, but also gives the mechanical explanations for the biological phenomenon that the leg knee presents a specific angle for vibration buffering and isolation.

Theoretical study of S wave passing through a double-layer wave impeding block in the unsaturated soil

In foundation vibration control, the multi-layer isolation barrier has a good vibration isolation effect due to its ability to block the propagation of elastic waves multiple times. In this paper, using the double-layer wave impeding block(WIB) as an example, the calculation model of a double-layer WIB as a vibration isolation barrier in the unsaturated soil foundation is established. The analytical solution of the transmission/reflection amplitude ratio when the S wave passes through the double-layer WIB in the unsaturated soil foundation is calculated by using the Helmholtz vector decomposition theorem. In addition, the influence of parameters such as the wave impedance ratio, saturation, shear modulus and density on the vibration isolation performance of the WIB are analyzed by numerical examples. The results show that the wave impedance ratio, shear modulus and density of the WIB material have a significant influence on the transmission/reflection amplitude ratio. Saturation has little effect on the transmission/reflection amplitude ratio of P1 and S waves but has a great effect on the amplitude ratio of P2 and P3 waves. The best vibration isolation effect can be obtained by selecting the optimal wave impedance ratio and shear modulus of the double-layer WIB material.

Numerical evaluation of tire chips–filled trench barriers for effective vibration isolation

Ground vibrations induced by man-made sources like vibrating machinery, vehicular movement, traffic, construction activities involving pile driving, blasting, dynamic compaction, etc., are rising rapidly and may disrupt nearby sensitive equipment, distress, and damage sub-structures. Therefore, vibration isolation is necessary to mitigate ground-borne vibrations with suitable techniques in the present-day context. Trench barriers are one of the most efficient techniques when the other isolation techniques are inefficient at the source. Although the open trench barriers are the most efficient, their stability is still a significant concern. Hence, these trenches are generally filled with suitable absorbing materials such as sawdust, geofoam, and concrete. The present study has attempted to explore the feasibility of using shredded tire chips as an infill material by evaluating their performance using the finite element method. The performance of tire chips–filled trench barriers predicted using FE analysis is also compared with the performance of other common infill materials such as sawdust and geofoam. Numerical studies show that the vibration isolation efficiency and their performance are highly sensitive to the shear wave velocity of the soil and infill material density for infill trenches. The key findings of the study suggest that shredded tire chips can also be used as an infill material in trenches for reducing ground-borne vibrations, and its performance is comparable with geofoam-filled trenches.

Theoretical analysis of 2D meta-structure with inertia amplification

This study proposed a square-grid structure (SGS) attached with inertial amplification mechanisms (IAMs) to obtain a better vibration isolation effect with low frequency and wide band gaps. According to the different stiffness assumptions of the IAM connecting rods, the proposed meta-structure is defined as two different types, 10° of freedom (DOF) elastic system (E-IAM) and 2-DOF rigid system (R-IAM). The motion equations of the two systems are given based on Newton's motion theorem and Lagrange's theorem, respectively. Dispersion relations and motion modes of the infinite system are discussed to obtain lower and wider band gaps. Vibration transmission characteristics of 20 × 20 meta-structures are also conducted. For the E-IAM system, ultra-low frequency vibration isolation can be achieved when the stiffness ratio of the connecting rod is the same in both vertical and horizontal directions and less than the main spring. The approximate analytical expression of the dispersion curve of the R-IAM system is given. Because the denominator is always greater than 1, it is proved that the cut-off frequency of the R-IAM system is always lower than that of the SGS. For finite R-IAM structures, when the longitudinal stiffness is asymmetric in both directions, multiple local resonant band gaps can be obtained in the passband, which is very beneficial to vibration reduction.

Model-based design of a novel modular mounting system: Light, compact, and efficient

Two-stage mounting systems applied in ships are expected to be light in weight, compact in installation space, and efficient in vibration isolation performance at the same time, which largely increases the engineering complexity. In this paper, analytical models of a two-stage mounting system with flexible and rigid intermediate mass are proposed to compare the vibration isolation effectiveness (VIE) performance and the influences of system parameters with the rigid intermediate mass on VIE are introduced. Based on the analysis results, an integrated adjustable two-stage mounting module is designed. Compared to the traditional floating raft mounting system with flexible intermediate mass, this two-stage mounting module can be arranged in a more compact structure space with greatly reduced size and weight. Furthermore, a novel modular mounting system prototype is proposed and manufactured based on several two-stage mounting modules and real-time behavior monitoring and controlling subsystem. The testing results verify the compatibility of the module design and the behavior monitoring and controlling system. The modular mounting system also exhibits excellent VIE performance combined with the advantage of compact intermediate mass size, lightweight, and automatic behavior monitoring and controlling.

Theoretical study of P1 wave passing through a double-layer wave impeding block in the unsaturated soil

Based on the propagation theory of elastic waves in unsaturated porous medium and single-phase elastic medium, the calculation model of a double-layer wave impeding block (WIB) as vibration isolation barrier in unsaturated soil foundation is established. The analytical solution of the transmission/reflection amplitude ratio of P1 wave passing through a double-layer WIB in unsaturated soil foundation are derived by Helmholtz vector decomposition theorem. The influences of physical and mechanical parameters such as saturation, wave impedance ratio, density, and shear modulus on the vibration isolation effect of the double-layer WIB when P1 wave passing through the double-layer WIB in the unsaturated soil foundation are analyzed by parametric studies. The results show that the saturation has a small effect on the transmission/reflection coefficients of P1 and S waves and a significant effect on the transmission/reflection coefficients of P2 and P3 waves. The wave impedance ratio and the shear modulus and density of the double-layer WIB have a significant effect on the transmission/reflection coefficients. The optimal shear modulus and wave impedance ratio of the double-layer WIB can be selected to obtain the best vibration isolation effect, which provides theoretical guidance for the application of the double-layer WIB in the field of unsaturated ground vibration control.

Study on the optimal vibration isolation design and effect of composite multilayer wave impeding block in unsaturated soil

Study on the optimal vibration isolation design and effect of composite multilayer wave impeding block in unsaturated soil

Negative Poisson’s Ratio Re-Entrant Base Modeling and Vibration Isolation Performance Analysis

Negative Poisson’s ratio materials are increasingly used in the design of vibration isolation bases due to their unique tensile properties. In this paper, based on the expansion feature of the negative Poisson’s ratio re-entrant structure, the influence of the size of the re-entrant structure within a single structure was analyzed, and a honeycomb base was designed with a negative Poisson’s ratio re-entrant structure. A new modeling method for the honeycomb base is proposed. In the modeling process, the honeycomb base was analyzed according to its symmetry using the Lagrange equation for base modeling and the finite element consistent mass matrix was introduced to simplify the calculation. The vibration isolation performance of the honeycomb base was evaluated by vibration level difference. COMSOL software was used to simulate and analyze the cellular base in order to verify the correctness of the results obtained from numerical modeling. In conclusion, the honeycomb base had a vibration isolation effect on external excitation in the vertical direction of the base. Furthermore, the vibration isolation performance of the base was greatly related to the wall thickness and Poisson’s ratio of the re-entrant structure.

Investigations on the Band-Gap Characteristics of Variable Cross-Section Periodic Structure Support Made of Acrylonitrile-Butadiene-Styrene.

Based on the band gap theory of periodic structure, this article proposes a new variable cross-section periodic structure support made of acrylonitrile-butadiene-styrene. The band gap characteristics of the periodic structure support were studied experimentally. According to the basic theory of band gap calculation, two kinds of supports with the same installation size were designed, and they were manufactured by 3D printer. Then, the displacement–load curve and the vibration characteristic curves of the periodic structure support were obtained through simulation analysis. The band gap range of the two supports was measured by hammer excitation, and the accuracy of the finite element model was verified by comparison with the experiment results. Finally, the response curve of the periodic structure support with variable cross-section every 100 Hz was obtained by excitation of the shaker, which verified the vibration isolation effect of the measured band gap. The results show a band gap in the support of the variable cross-section periodic structure, compared with the support of the non-periodic structure. If the vibration frequency is within the band gap frequency, the vibration will be significantly attenuated.