Vibration Isolation Characteristics Research Articles

Design of piezoelectric quasi— zero—stiffness metastructures for improved low—frequency vibration isolation

Abstract In this paper, a novel type of piezoelectric quasi–zero stiffness (QZS) metastructure is proposed and the improved vibration isolation performance is investigated. A piezoelectric QZS metastructure is composed of curved beams covered with piezoelectric macro–fiber composite patches, to which digital circuits are connected. Based on the principle of minimum potential energy and the mode superposition method, the constrain on the geometry and material parameters of the piezo–curved beams to achieve QZS is given. According to this design criterion, 1D, 2D and 3D piezoelectric QZS metastructures are designed, and their improved low–frequency vibration isolation characteristics are comprehensively analyzed through theoretical, numerical and experimental studies. It is demonstrated that by optimizing the parameters of the resonant transfer functions implemented in the digital circuits, high–level damping localized near the first resonant peak can be introduced into the curved beams. As a result, the resonant peaks of the metastructures can be reduced without compromising the isolation performance beyond those peaks.

Development of vibration isolation system for halls and report on sound insulation and vibration experiment

Rubber and polyurethane have been widely used as vibration isolation materials in halls and studios. In this project, we have developed a floor-mounted coil spring vibration isolator with improved vibration isolation and sound insulation characteristics, while keeping the installation height equivalent or lower than rubber and polyurethane. In this paper, we evaluate the vibration isolation performance of the developed device by measuring vibration transmission loss, and confirm that the device can suppress surging, which is a weak point of metal springs, while achieving a low natural frequency. The sound transmission loss measurement also confirmed that the floating slab incorporating the device has sufficient sound insulation performance, and these results indicate that the device can be applied to acoustic spaces such as concert halls, where quietness is required.

Tunable bandgaps in an elastic meta-plate with shape memory alloy springs

In this paper, a tunable metamaterial based on shape memory alloy springs is designed, which can achieve bandgap tuning by spring's unique shape memory effect. The variation mechanism of shear modulus and geometrical parameters of shape memory alloy springs is investigated by considering a detailed phase transition mechanism. For any specific temperatures, the energy band structure and frequency response spectrum of the metamaterial are calculated by numerical simulation. And the theoretical prediction models of bandgap boundary frequency and tuning range at different temperatures are established. The experimental test of vibration transmission of metamaterial is finally presented. The results show that (1) By varying the spring's shear modulus and height, the metamaterial exhibits excellent vibration isolation characteristics and bandgap tuning in low-frequency range of 124–226Hz. (2) The bandgap boundaries and tuning ranges can be predicted by the theoretical prediction model, which shows good agreement with both the simulation results and the experimental data. (3) By artificially designing shape memory alloy springs with larger shear modulus and wire radius, smaller helix radius and number of turns, the bandgap moves to higher frequencies. The current work can provide a reference for further engineering applications with the tunable elastic/acoustic metamaterials.

A locally resonant metamaterial and its application in vibration isolation: Experimental and numerical investigations

AbstractVibration isolation metamaterial barrier has been extensively studied in mitigating the damage induced by vibration, while a deeper understanding of the vibration isolation characteristics based on laboratory experiments is still lacking. In this work, a locally resonant metamaterial barrier is proposed, and a large‐scale laboratory experiment was first designed to investigate the isolation mechanism of the proposed metamaterial barrier. The metamaterial vibration isolation barrier is assembled by arraying 5 × 5 resonators. To better explain the observations in experiments and unveil the underlying isolation mechanism, COMSOL Multiphysics was also employed to simulate the laboratory experiment. Subsequently, the vibration isolation effect is quantitatively analyzed by analyzing the acceleration amplitude reduction spectrum (ARS) of the ground surface. The vibration isolation mechanism is discussed by monitoring the acceleration field around the metamaterial barrier. The results indicate that two significant locally resonant attenuation domains are observed, which are induced by the first‐order and second‐order vertical resonance frequencies of the metamaterial. Another experimental scheme that simultaneously monitored the acceleration of the mass block and the bottom of resonators was implemented to investigate vibration in the resonator. The vibration energy distribution on the mass block and the bottom of the resonator is found to depend significantly on the vibration frequency. When the frequency is lower than a certain frequency, the locally resonant is dominant. Otherwise, the geometric scattering is dominant. The vibration isolation mechanism of the locally resonance metamaterial was investigated by laboratory experiments and provided an effective solving path for isolating the low‐frequency vibration.

Dynamic characteristics of nonlinear vibration isolator for gas turbine

AbstractIn this study, a theoretical model of the vibration isolation system of the gas turbine is developed and numerically solved. A simplified finite element (FE) model was also established to determine the response under the shock load. The results of the FE model are used to verify the effectiveness of the theoretical model and the numerical solution. The influence of isolator stiffness, vibration isolator damping, and vibration isolator nonlinear stiffness coefficient on the shock response of the vibration isolation system is studied using the controlled‐variable method. These parameters (stiffness, damping, and nonlinear coefficient) enter into the shock resistance design of gas turbine vibration isolators.

Analytical analysis of vibration isolation characteristics of quasi-zero stiffness suspension backpack

Analytical analysis of vibration isolation characteristics of quasi-zero stiffness suspension backpack

A viscoelastic metamaterial beam for integrated vibration isolation and energy harvesting

Locally resonant metamaterials have low-frequency band gaps and the capability of converging vibratory energy in the band gaps at resonant cells. It has been demonstrated by several researchers that the dissipatioin of vibratory energy within the band gap can be improved by using viscoelastic materials. This paper designs an integrated viscoelastic metamaterial for energy harvesting and vibration isolation. The viscoelastic metamaterial is achieved by a viscoelastic beam periodically arrayed with spatial ball-pendulum nonlinear energy harvesters. The nonlinear resonator with an energy harvesting function is achieved by placing a free-rolling magnetic ball in a spherical cavity with an additional induction coil. The dynamic equations of viscoelastic metamaterials under transverse excitation are established, and the energy harvesting and vibration isolation characteristics within the dispersion relation of viscoelastic metamaterials are analyzed. The results show that the vibrations of the main body of the viscoelastic metamaterial beam are significantly suppressed in the frequency range of the local resonance band gap. At the same time, the elastic waves are limited in the nonlinear resonator with an energy harvesting function, which improves the energy output. Finally, an experimental platform of viscoelastic metamaterial vibration is established for validation purposes.

Low-frequency vibration bandgaps and deep learning-based intelligent design method of Y-shaped core sandwich metabeams

In this paper, the wave propagation mechanics theoretical model of Y-shaped core sandwich metabeams with local resonators is established based on the spectral element method, and the flexural wave bandgaps and vibration isolation characteristics are studied. The reliability of the theoretical model of Y-shaped core sandwich metabeams is verified by the finite element method and experiment. On this basis, a deep learning-based intelligent design method for predicting the vibration transmission characteristics and structure design of Y-shaped core sandwich metabeams is proposed. A dataset is created using the theoretical model of wave dynamics, and deep neural networks are constructed to forward prediction of transmission characteristics and intelligent design of Y-shaped core sandwich metabeams, respectively. Results indicate that the bandgap range of Y-shaped core sandwich metabeams is 2.5 times that of Y-shaped core sandwich beams, and the start frequency of bandgap is reduced by 578 Hz. The prediction of the transmission characteristic curve is in good agreement with the target, and the average relative error of intelligent design is below 3 %, which verifies the precision of the intelligent design method. The innovative, intelligent design method provides a novel way to realize engineering vibration reduction design of acoustic metamaterials rapidly.

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.