Vibration Isolation Characteristics Research Articles

Vibration Isolation Performance of a Constrained Damping Base for a High-Pressure Plunger Pump

Based on the effect of damped shear deformation on energy dissipation, a new constrained damping base for a polymer injection platform deck is proposed to reduce the excessive vibrations caused when multiple plunger pumps are jointly operated. A model for analyzing the vibration response of an I-beam-constrained damping base for a polymer injection platform with multiple plunger pumps was established using Abaqus 6.14 software and compared with rigid base and traditional rubber vibration isolators in terms of its vibration isolation performance. Furthermore, the effects of the damping material’s loss factor, the thickness of the damping layer, and the number of expansion layers on the vibration isolation characteristics of the constrained damping base were explored. This study shows that, with an increase in the damping material’s loss factor, the thickness of the damping layer and the number of extended layers, the vibration isolation performance of the constrained damping base is gradually enhanced. When the damping material’s loss factor is 1.0, the thickness of the damping layer is 20 mm, and the number of extended layers is 3, the constrained damping base’s vibration damping effect is optimized, and its vibration isolation rate becomes as high as 46.63%, which can significantly reduce the vibration response of the polymer injection platform.

A Flexibly Function‐Oriented Assembly Mechanical Metamaterial

AbstractBased on the snap‐through instability, the pursuit for mechanical metamaterials with flexible functional applications and the ability to combine with information has been the Holy Grail for structural scientists. Here, the function/application‐oriented bistable unit motifs (UMs) are developed by an elaborately architectural design inspired by the hind leg of the frog in jumping, and a corresponding assembled strategy is proposed. Three functional applications derived from their progressive evolutions. The first is the construction of on‐demand assemblable mechanical curves, including multi‐stage vibration isolation, recoverable energy absorption, and energy dissipation along with integrated vibration isolation and energy dissipation characteristics. The second is the development of mechanic and temperature double pattern encryption strategy using bistability and shape memory programmability, resulting in 4n encryption and decryption modes for n‐bit encryption devices. Finally, five non‐volatile basic mechanical logic gates and a universal combinatorial half‐adder are built, affording guidance to unconventional computing devices with logic functions.

Vibration isolation characteristics of a rubber isolator in the deep water condition

Vibration isolation characteristics of a rubber isolator in the deep water condition

Vibration isolation characteristics of a novel composite flexible vibration-damping foundation

To address the challenge of low-frequency vibration in ships, we introduce a vibration isolation technique and a composite flexible vibration-damping foundation grounded in the principles of impedance equalization and the off-plane attenuation properties of surface waves. We utilize a fluid-structural coupling finite element method and experimental validation to analyze the effect of various properties of the liquid layer of the base. The results indicate that the composite foundation offers superior vibration isolation compared to traditional foundations across a frequency range of 10–500 Hz. Enhancements in the liquid’s viscosity and an increased layer thickness are found to significantly bolster the foundation’s ability to isolate vibrations. The relationship between liquid density and the vibration isolation performance of the base is not entirely positive. An increase in liquid density does provide some improvement to the vibration isolation performance at higher frequencies. Additionally, the presence of multiple liquid sacs within the foundation has a minimal influence on low-frequency isolation but proves to be increasingly beneficial at higher frequencies. Through this study, we aim to provide fresh perspectives and solutions for the attenuation and management of low-frequency vibrations in ships.

Low frequency vibration isolation characteristics and intelligent design method of hull grillage metastructures

In this paper, the wave propagation mechanics theoretical model of hull grillage metastructures with local resonators is established, and the intelligent design method of hull grillage metastructures is proposed based on deep learning. The flexural vibration isolation characteristics of periodic hull grillage structures and the proposed hull grillage metastructures are theoretically studied using the spectral element method. Numerical calculation and experimental tests of the flexural wave vibration transmission of hull grillage metastructures are conducted to validate the proposed theoretical model. In addition, the data set is constructed by using the wave mechanics theoretical model of hull grillage metastructures, and the forward prediction neural network model of vibration transmission characteristics as well as the inverse design neural network model of hull grillage metastructures are established. Results show that compared with periodic hull grillage structures, the proposed hull grillage metastructures possess significant low-frequency flexural wave vibration isolation characteristics which almost completely covers the low-frequency range from 27 Hz to 169 Hz. Both forward prediction and inverse design network models have good performance, which verifies the correctness of the intelligent design method based on deep learning, and provides a new direction for the structural design on demand of low-frequency vibration reduction of ship and offshore structures.

Origami-inspired quasi-zero stiffness metamaterials for low-frequency multi-direction vibration isolation

Multi-directional low-frequency vibration isolation is an unavoidable problem in many practical engineering scenarios. However, to date, most works are unable to achieve this goal, and those that can do so only to some degree, but their structure is complex and large, limiting the range of applications in practical engineering. Here, we propose a kind of quasi-zero stiffness (QZS) metamaterial constructed from a series of Kresling-pattern origami-inspired structures, whose simple topology with reasonable design parameters can obtain the expected QZS features. Moreover, the decoupling strategy adopted by the proposed QZS metamaterials allows for the independent motion of adjacent unit cells, resulting in an improvement in controllability and programmability. We demonstrate, both in simulations and experiments, the design process and the multi-directional low-frequency vibration isolation characteristics of the proposed QZS metamaterial. This study provides a method for realizing multi-directional low-frequency vibration isolation, expanding the application potential of QZS metamaterials for broader needs.

Vibration isolation characteristics of magnetorheological damper for the large wind turbine gearbox

ABSTRACT The gearbox vibration isolation theory in the large wind turbine transmission system is analyzed. The host frame is flexible, and the vibration isolation system is approximately equivalent to a two-degree-of-freedom system. According to large wind turbine gearbox isolation requirement, and a vibration isolation device of magnetorheological damper of the large wind turbine gearbox is designed, the magnetic field characteristics inside the magnetorheological damper are simulated and calculated by using COMSOL, when 0.5, 1, 1.5and 2 A currents are passed through the magnetorheological damper coil, the magnetic induction intensity of the damping gap and the output force of the magnetorheological damper are calculated, it can reach 1300N-5400N, which meets the gearbox vibration isolation requirements. It designed the on-off current control method of the magnetorheological damper. The prototype is tested on a certain type of offshore wind turbine, and the acceleration spectrum signals of the gearbox in the Z direction are collected under the working conditions of 990, 1200 and 2000 r/min. According to the collected data values, the vibration isolation characteristics of the designed magnetorheological damper are analyzed; the data show that the vibration level drop is about 20 dB, and the vibration isolation effect is good. By using the coherence coefficient method to process the measured data, the modified transfer function is obtained, which is consistent with the theoretical transfer function of the vibration model of two-degree-of-freedom system, so it is proved to be reasonable. The vibration isolation characteristics of rubber and the magnetorheological damper are compared at the rated speed, and it shows that the maximum vibration acceleration of the gearbox under the magnetorheological damper reduces from 0.375 m/s2 to 0.175 m/s2, which verify the damping effect of the magnetorheological damper.

Vibration Isolation Characteristics of Impedance-balanced Ship Equipment Foundation under Unbalanced Excitation

A new type of impedance-balanced ship equipment foundation structure based on the principle of impedance balancing using a “discontinuous panel-vibration isolation liquid layer-foundation structure” is proposed to solve the problem of poor low-frequency vibration isolation of the foundation under unbalanced excitation of shipboard equipment. Based on the finite element method, the influence of characteristic parameters of the foundation panel structure on its vibration reduction characteristics under unbalanced excitation is explored. The results show that the vibration isolation level of the impedance-balanced foundation is 10 dB higher than the traditional foundation in the low-frequency band of 10-500 Hz when subjected to combined excitation of concentrated force and moment. Increasing the thickness of the impedance-balanced foundation panel can enhance the isolation effect. Increasing the number of sub-panels can effectively reduce the vibration response of the foundation panel and enhance the isolation performance of the foundation. The connection stiffness between sub-panels has a small effect on the isolation performance of the foundation.

Adjustable indentation and vibration isolation performances of nacre-like metamaterial

ABSTRACT Along with the living environment, organisms have evolved structures that adapt to specific environments and have better mechanical properties. Bioinspired materials learn from nature and improve their mechanical properties by imitating the structure of living organisms. Based on the 4D printed shape memory polymer and the bioinspired design method, this research proposes a soft and hard phase hybrid bioinspired metamaterial with shape memory effect and programmable mechanical properties. Compared with traditional nacre-like materials, bioinspired materials have adjustable characteristics of mechanical properties, impact resistance, and low-frequency vibration isolation. First, based on the constitutive relation of SMP (Shape memory polymer) material and its numerical simulation, an intelligent bioinspired metamaterial is designed. Subsequently, the mechanical properties and vibration isolation behavior and adjustability performance of multi-scale bioinspired metamaterials are explained by experiments. Finally, the adjustable functional mechanism of the deformation and vibration isolation of the bioinspired metamaterial is described. The research of these bioinspired metamaterials has broad application prospects in the fields of impact protection and low-frequency vibration absorption.

Nonlinear dynamics of 1D meta-structure with inertia amplification

Considering the low-frequency vibration isolation properties of the inertial amplification mechanism (IAM) and the band gap of the periodic structure, this paper is concerned with the dynamic characteristics of the nonlinear inertial amplification mechanism (NIAM), theoretically. This study focused on the influence of nonlinearity on vibration isolation characteristics. Both analytical and numerical methods are adopted. Through the analysis of a basic NIAM element, nonlinear modes and complex phase motions are observed. The bifurcation property shows that complex motions (periodic, quasi-periodic, and chaotic) can be obtained by altering the exciting frequency for some intended goals, especially for vibration reduction. Analysis of the dispersion relation and the vibration transmissibility of the 1D periodic meta-structure composed of multiple NIAMS (NIAMMS) demonstrates its superiority with a decrease of 18.4% in the lower bound of the band gap, compared with a common 1D nonlinear periodic meta-structures. Furthermore, it is possible to obtain an ultra-low and ultra-wide nonlinear band gap by properly adjusting the parameters such as nonlinear stiffness, mass ratio, assembly angle, and damping.

Effective Frequency Range and Jump Behavior of Horizontal Quasi-Zero Stiffness Isolator

The quasi-zero stiffness (QZS) isolator shows excellent characteristics of low-frequency vibration isolation. However, the jump behavior caused by the strong nonlinearity is a primary reason for the failure of QZS isolators. In order to grasp the effective frequency range and failure mechanism of a horizontal QZS isolator comprehensively, the dynamics of the isolator were studied in the following two cases. In the first case, the isolator is subject to a base displacement excitation; in the second case, the isolator is installed on a linear structure that is subject to a harmonic force. The nonlinear algebraic equations describing the steady-state response of the two systems were derived via the complexification-averaging method, and the results obtained using the derived expressions were verified by comparing the results of the complexification-averaging method and the Runge–Kutta method. The effective frequency ranges of the isolator were then obtained, and the jump phenomena in the response amplitude induced by the strong nonlinearity of the isolator were analyzed. The results show that when the excitation amplitude is small, the vibration isolation system does not exhibit jumping behavior and the effective frequency range is relatively wide. With increases in the excitation amplitude, the system can exhibit jumping behavior when an additional impact load is considered, and this phenomenon leads to a narrowing of the effective frequency range. The characteristics of the jump phenomena produced in the two cases were analyzed, and the differences in the jump behaviors were elucidated. Furthermore, the effect of the isolator parameters on the effective frequency range was investigated.

A semi-active quasi-zero stiffness vibration isolator based on magnetorheological elastomer with a fast convergence switch control

Quasi-zero stiffness (QZS) isolators have attracted extensive attention due to their high-static–low-dynamic stiffness. The effectiveness of the traditional QZS (T-QZS) isolators to attenuate low-frequency vibration has been extensively studied. The T-QZS isolator, however, cannot usually provide satisfactory vibration mitigation performance under ultra-low frequency excitation. To tackle this challenge, we propose a semi-active QZS isolator featuring magnetorheological elastomer (SAQZS-MRE isolator). The prominent merit of the proposed design is that the applied MRE material can provide varying stiffness and damping to the proposed SAQZS-MRE isolator, making the isolator suitable for vibration isolation under wide-band low-frequency range. The dynamic viscoelasticity properties of the MRE are experimentally characterized, to formulate the dynamic modeling of the SAQZS-MRE isolator. The open-loop vibration isolation characteristics of the SAQZS-MRE isolator are assessed using the harmonic balance method (HBM). Subsequently, two semi-active control strategies including skyhook and fast convergence switch (FCS) are effectively utilized in the proposed SAQZS-MRE isolator to evaluate their closed-loop performance. The results demonstrate that the SAQZS-MRE isolator with FCS control can eliminate the resonance peak and reduce the initial isolation frequency. In the higher frequency range, it can also improve the vibration isolation performance compared with the SAQZS-MRE isolator with passive control.

Research on Vibration Absorption and Isolation Characteristics of Periodic Acoustic Black Hole Beam Resonators and their Enhancement

An acoustic black hole (ABH) resonator is regarded as an efficient approach for controlling vibration caused by flexural wave energy. In this paper, the beam models with periodic ABH beam resonators are designed. Both the vibration absorption and isolation performances are investigated. Theoretical models based on the Transfer Matrix Method are presented to evaluate the reflection coefficient, which is validated both by the semi-analytic method combined with the Finite Element Method (FEM) and the Impedance Matrix Method. Meanwhile, FEM models of periodic ABH beam resonators acting as the beam terminator and isolator are established and analyzed. The results show that the periodic ABH beam resonators are of a better vibration reduction performance in lower frequency and have wider bandgaps for lower reflection coefficient and higher transmission loss than the single wedge. Moreover, with the increasing number of periods, the advantages of the periodic ABH beam resonators in reducing vibration become more obvious. Through the complex plane and dynamic analyses, it shows that multimode coupling and meta-damping effect lead to superior performance since the enriched modal content is introduced by the periodic ABH beam structure. This effect is also verified by the experimental result. Besides, the study also reveals the paradoxical relationship between vibration absorption and isolation performances. Additionally, parametric studies are conducted to disclose the effects of structural parameters. Based on the analyses, two approaches are proposed to enhance the vibration reduction performances, including the composite beam resonators and compound beam resonators. This paper illustrates a promising vision for applying the periodic ABH beam resonators to various vibration control fields.

Bifurcation analysis and nonlinear dynamics of a rolling magnet multistable electromagnetic energy harvester

The objective of this study is to provide a rolling magnet multistable electromagnetic-induction energy harvester (RM-MEH) for scavenging energy from a wide frequency range. The RM-MEH designed based on a magnetic levitation rolling magnet possesses the merit of small damping. By clarifying the mechanics of the RM-MEH, the static bifurcation behavior is investigated and results demonstrate that monostable, bistable, and tristable configurations with different types of potentials can be obtained with proper parameters. Numerical simulations under sweep frequency excitation indicate that the monostable, bistable, and tristable configurations with proper potential functions achieve large-amplitude oscillation in a wide frequency range. Under constant frequency excitation, the nonlinear dynamics are analyzed utilizing the bifurcation diagram, phase orbit, and Poincaré map, and the multiple vibrational patterns are verified. Finally, the vibration isolation characteristics of the system are briefly discussed considering the electromagnetic force of the RM-MEH. In summary, the demonstration of the novel RM-MEH expands the approach to achieving multistable oscillation and provides a new way of thinking for designing nonlinear energy harvesters.

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.

Dual-functional hierarchical mechanical metamaterial for vibration insulation and energy absorption

In this study, the vibration isolation characteristics and crushing behaviors of novel hierarchical mechanical metamaterials are investigated. Numerical analyses are carried out for a class of mechanical metamaterials with different hierarchical configurations. The effects of the hierarchical configurations on the band gap distributions and energy absorption efficiency are carefully studied. The results indicate that the hierarchical configuration has remarkable potential in broadening the band gap and improving energy-absorbing efficiency. Moreover, the configuration (S3) with the best performance of vibration isolation and energy absorption among the proposed metamaterials is determined. The parameter analysis on S3 is further performed to analyze the effects of structural parameters on the band gap characteristics and crushing performance. Finally, multi-objective optimization is employed to seek optimal structural parameters of S3 for enhancing the gap-midgap ratio and the specific energy absorption, simultaneously. This study provides effective guidance for designing mechanical metamaterials with excellent vibration isolation capacity and energy absorption efficiency.

Research on the Vibration Isolation Characteristics of Floor Vibration Isolation Slab System under Train Operation

This study takes the vibration isolation measures of building floor vibrations induced by trains as the starting point and carries out both theoretical derivation and numerical simulation. A four-degree-of-freedom (DOF) multi-dimensional vibration isolation platform (VIP) dynamics model is established based on the theoretical research of single-level, single-degree-of-freedom vibration isolation systems. Under multi-point excitation, the model can deduce the horizontal and vertical vibration responses of the VIP system. A comprehensive analysis of the vibration isolation performance of the VIP system on the floor and how the variation of the parameters influences the performance of the vibration isolation systems are presented. Several variables, such as the thickness, stiffness, damping ratio, and the number of isolators of the VIP system, are theoretically found to have a significant impact on the vibration isolation effect of the floor VIP system. Empirical results show that the VIP system significantly affects the vibration isolation of the building floor induced by a train and has the best vibration isolation effect on the acceleration response and the worst vibration isolation effect on the displacement response.

The vibration isolation characteristics of torsion bar spring with negative stiffness structure

Nonlinear stiffness systems are an effective way to achieve low frequency vibration isolation. To improve the support capacity and ride comfort of nonlinear stiffness systems, this paper proposes a quasi-zero stiffness (QZS) vibration isolator composed of the torsion bar spring and negative stiffness structure (NSS) and investigates its vibration isolation characteristics. The influence of the system parameters on the static nonlinear stiffness peculiarities of the vibration isolator is delved. The motion equation of the isolator under the harmonic excitation from the base can be expressed as Helmholtz–Duffing equation due to an offset distance from zero stiffness point to the equilibrium position. The primary resonance response of the QZS system is approximately analytically predicted by Harmonic Balance Method (HBM). The absolute acceleration transmissibility of the QZS system considering the effect of excitation amplitude and system parameters is investigated and compared with the equivalent linear system to evaluate the isolation performance of the nonlinear system. Then, the numerical simulation is investigated and good agreement with theoretical analysis. The validity of the proposed model is verified by finite element method (FEM) and an experiment. Based on the numerical simulation and experiment results, the proposed nonlinear system possesses a better vibration isolation performance of heavy equipment in the low-frequency region.

Mechanical vibration effects in the biospeckle laser technique for portable equipment application in agriculture / Efeitos da vibração mecânica na técnica biospeckle laser para aplicação em equipamento portátil na agricultura

The biospeckle laser (BSL) is a technique developed based on the processing of optical interference patterns formed when a laser light strikes a biological surface. This non-destructive image processing technique is used to quantify the activity level of a sample. Since it is not always feasible to move biological samples to a laboratory to be analyzed, on-site application is necessary for the advancement of the technique. There are limitations in the use of the technique in the field, vibration interference is one of them. Aiming to understand the level of this interference as well as to propose ways to mitigate them, in this work it was developed a portable prototype for dynamic laser speckle (DLS) analysis that was subjected to experimental modal analysis and transmissibility tests. The prototype’s natural frequencies were obtained, and it was evaluated how the optical technique behaves when excited at these and other frequencies. It was discovered that BSL is more sensitive to low frequencies, close to 5 Hz. In the transmissibility tests, it was found that the isolator with the lower stiffness presented the best characteristics of vibration isolation for the proposed purposes, making possible the portability of the prototype from the isolation of ordinary external mechanical vibrations.

Vibration isolation properties of the nonlinear X-combined structure with a high-static and low-dynamic stiffness: Theory and experiment

A nonlinear X-combined structure is proposed and designed using an X-shaped structure (positive/negative stiffness mechanism) and two inclined springs (positive stiffness mechanism) to avoid existing negative stiffness and unstable factors and to improve vibration isolation characteristics. The mechanism possesses high-static and low-dynamic stiffness in a larger displacement range. In order to identify the coupling mechanism of the combination of two nonlinear mechanisms, its static and dynamic properties are investigated. The displacement transmissibility with multi-valued solutions is used to evaluate the vibration isolation of the combined structure. A new mathematical method is used to obtain a multi-valued analytical solution to the nonlinear equation of motion, which is then validated using the ADAMS software and the least square method (LSM). The novelty of this study is (a) the system has a very useful nonlinear stiffness with positive/quasi-zero/zero stiffness over the entire working range, and the quasi-zero stiffness (QZS) range is greater than that of an X-shaped structure; (b) compared to the existing nonlinear vibration isolator, such as three-spring systems and X-shaped structures, the proposed structure has the lower equivalent stiffness in the vibration isolation range, and the vibration isolation performance is better when each system has the same loading capacity; (c) the completed and accurate nonlinear solutions can more scientifically reflect the vibration isolation characteristics of the system; (d) the introduction of oblique springs into the X-shaped structure can make it easier to adjust the stiffness of the structure and use the tensile spring as the oblique spring, and the X-combined structure is easier to be designed and installed. This study shows that the proposed structure can provide excellent vibration isolation by combining two nonlinear mechanisms. These advantages are also confirmed by experiments and comparison with existing QZS isolators. This vibration isolation system will provide a new analytic method and innovative approach to the QZS isolator.