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Vibration isolation is one of the most efficient approaches to protecting host structures from harmful vibrations, especially in aerospace, mechanical, and architectural engineering, etc. Traditional linear vibration isolation is hard to meet the requirements of the loading capacity and isolation band simultaneously, which limits further engineering application, especially in the low-frequency range. In recent twenty years, the nonlinear vibration isolation technology has been widely investigated to broaden the vibration isolation band by exploiting beneficial nonlinearities. One of the most widely studied objects is the “three-spring” configured quasi-zero-stiffness (QZS) vibration isolator, which can realize the negative stiffness and high-static-low-dynamic stiffness (HSLDS) characteristics. The nonlinear vibration isolation with QZS can overcome the drawbacks of the linear one to achieve a better broadband vibration isolation performance. Due to the characteristics of fast response, strong stroke, nonlinearities, easy control, and low-cost, the nonlinear vibration with electromagnetic mechanisms has attracted attention. In this review, we focus on the basic theory, design methodology, nonlinear damping mechanism, and active control of electromagnetic QZS vibration isolators. Furthermore, we provide perspectives for further studies with electromagnetic devices to realize high-efficiency vibration isolation.

To investigate the vibration isolation effect of composite vibration isolation walls on surface vibrations in suburban railway deep tunnels under various influencing factors, an integrated numerical model of the train was initially developed. This model solved the wheel-rail interaction force and was applied to a three-dimensional volume coupling model of the track soil. Subsequently, the model's reliability was validated through comparison with measured data. Afterward, the vibration isolation effects of various types of EPS material vibration isolation walls were examined, with a focus on exploring the impact of thickness, material proportion, and relative positioning of the materials within the vibration isolation wall composed of EPS material and concrete. Research indicates that with an increase in the burial depth of a single material vibration isolation wall, its effective vibration isolation frequency range gradually widens. When the burial depth of the vibration isolation wall exceeds the tunnel burial depth, the vibration isolation effect is optimal. Composite vibration isolation walls, with thicknesses smaller than single-material vibration isolation walls, exhibit superior vibration isolation effects compared to their single-material counterparts. The effective vibration isolation frequency band of composite vibration isolation walls differs from that of single-material vibration isolation walls. Using the optimal-size vibration isolation wall of a single material as a composite vibration isolation wall enhances the vibration isolation effect of peak acceleration in the frequency domain by 16.58% and peak velocity by 16.95%. Moreover, frequency domain peak displacement experiences a 30.73% improvement in the vibration isolation effect.

In this paper, an archetypal aseismic system is proposed with 2-degree of freedom based on a smooth and discontinuous (SD) oscillator to avoid the failure of electric power system under the complex excitation of seismic waves. This model comprises two vibration isolation units for the orthogonal horizontal directions, and each of them admits the stable quasi-zero stiffness (SQZS) with a pair of inclined linear elastic springs. The equation of motion is formulated by using Lagrange equation, and the SQZS condition is obtained by optimizing the parameters of the system. The analysis shows that the system behaves a remarkable vibration isolation performance with low resonant frequency and a large stroke of SQZS interval. The experimental investigations are carried out to show a high sonsistency with the theoretical results, which demonstrates the improvement of aseismic behavior of the proposed model under the seismic wave.

A three‐magnet‐ring quasi‐zero stiffness (QZS‐TMR) isolator is designed to solve the problem of low‐frequency vibration isolation in the vertical direction of precision equipment. QZS‐TMR has both positive and negative stiffness structures. The positive stiffness structure consists of two mutually repelling magnetic rings and the negative stiffness structure consists of two magnetic rings nested within each other. By modulating the relative distance between positive and negative stiffness structures, the isolator can have QZS characteristics. Compared with other QZS isolators, the QZS‐TMR is compact and easy to manufacture. In addition, the working load of QZS‐TMR can be flexibly adjusted by varying the radial widths of the inner magnetic ring. In this paper, the static analysis of QZS‐TMR is carried out to guide the design, and the low‐frequency vibration isolation performance is studied. In addition, the experimental prototype of QZS‐TMR is designed and manufactured. The static and vibration isolation experiments are carried out on the prototype. The results show that the initial vibration isolation frequency of the experimental prototype is about 4 Hz. The results show an excellent low‐frequency vibration isolation effect, which is consistent with the theoretical research. This paper introduces a new approach to the design of the QZS isolator.

Linear compressors exhibit high compression efficiency and low noise characteristics, showcasing broad application prospects in various fields such as aerospace, medicine, household appliances, and more. However, due to the complexity of their structures and operation, the issue of vibration isolation in linear compressors has long been a research challenge within the industry. Addressing this challenge, this paper provides an overview of vibration isolation optimization methods for linear compressors. It delves into the discussion of different vibration sources in linear compressors and their respective measurement techniques. By integrating both single degree of freedom (SDOF) and multiple degree of freedom (MDOF) vibration isolation models, this paper describes both active and passive vibration isolation methods tailored to linear compressors. Furthermore, a feasible optimization approach is proposed. Finally, the paper offers insights into the developmental potential and feasibility of vibration energy recovery strategies.

This work aims to identify ways to achieve dynamic performances of a novel double‐layer vibration isolation system (DL‐VIS) capable of achieving multi‐directional isolation and extreme environmental adaptability. A forward modeling approach applicable to complex systems has been developed and analyses of nonlinear dynamic characteristics under different working conditions are performed. First, by integrating with constitutive models in terms of individual elastic elements and the connective relationships within the structure, multidirectional constitutive models for isolation devices are established. Further, the decomposition of linear and nonlinear stiffness components in different directions is performed using the Taylor expansion method. Subsequently, the dynamic response under sinusoidal sweep frequency loading is obtained using the related stiffnesses in the dynamic model and adopting the extended harmonic balance method. The effects of stiffness, damping, and a nonlinear stiffness gradient on the DL‐VIS response are thoroughly evaluated. Finally, the vibration isolation performance and nonlinear dynamics under different working conditions are examined, and the proposed dynamic model is experimentally validated. The results indicate that the response of DL‐VIS varies significantly under different working conditions, particularly under overload conditions. The nonlinear characteristics lead to wide‐band instability near the natural frequency and excellent vibration attenuation performance in multiple directions. The theoretical model agrees well with the experimental results in the nonresonant region and near the first resonant peak, which proves the prediction accuracy in the low‐frequency range. These findings provide robust theoretical and technical support for the design and performance optimization of isolation systems.

Based on the theory of single-phase elastic media and unsaturated porous media, the vibration isolation effect of double-layer wave impeding block (WIB) in the unsaturated soil foundation is investigated. Using the Fourier transform and Helmholtz vector decomposition, the calculation formula of the dynamic response of unsaturated ground subjected to a strip harmonic load on the ground surface is established. By analyzing the wave impedance ratio at the interface between the double-layer WIB and the unsaturated soil foundation on the vibration isolation effect of the double-layer WIB, the corresponding interlayer wave impedance ratio of the double-layer WIB with the best vibration isolation effect is selected. On this basis, the influence of load frequency, saturation, thickness, and embedded depth on the vibration isolation performance of the double-layer WIB is analyzed. The results show that the best vibration isolation effect of the double-layer WIB can be obtained by designing the wave impedance ratio at the intersection between the layers of the double-layer WIB. At the same thickness, the vibration isolation effect of the double-layer WIB is better than that of the homogeneous WIB. The double-layer WIB enhances the frequency width of homogeneous WIB vibration damping, which has a better vibration isolation effect on low-frequency, medium-frequency and high-frequency vibration (5 Hz <  f  < 70 Hz). When the thickness of double-layer WIB exceeds the critical thickness, the vibration isolation effect decreases with the increase in thickness. Soil saturation has a significant effect on the vibration isolation effect of the double-layer WIB, and the double-layer WIB can achieve a better vibration isolation effect at high saturation.

Based on single-phase elastic medium and unsaturated porous medium theory, the vibration isolation effect of double-layer wave impeding block (WIB) in unsaturated ground under an underground dynamic load is studied. The results show that the optimal vibration isolation effect can be obtained by designing the wave impedance ratio at the intersection between the layers of the double-layer WIB. In the case of the same thickness, the vibration isolation effect of the designed double-layer WIB is not only much better than that of the homogeneous WIB, but also improves the characteristic that the homogeneous WIB is only good at low frequency vibration isolation. Soil saturation has a significant effect on the vibration isolation effect of double-layer WIB in unsaturated soil foundation, and a better vibration isolation effect can be achieved in the case of lower saturation.

Vibrations from the power system can significantly affect the working performances (ocean observation) of autonomous underwater gliders (AUGs). In order to reduce the vibration transmission from vibration sources to the precision instruments in AUGs, single- and two-stage vibration isolator rings are designed in this paper. The dynamic models of the single- and two-stage vibration isolation of the AUG are presented. The force transmission ratio of the AUG is calculated in MATLAB code. The influences of the isolator and the structure stiffness are analyzed. The dynamic stiffness of the designed isolators, as an important design parameter, is calculated using the finite element method. The influence of the designed parameter on the dynamic stiffness of the rubber ring isolator is discussed. The coupled vibro-acoustic finite element method is used to analyze the vibration and acoustic response of an AUG with the single- and two-stage vibration isolators. The insertion loss is calculated in order to assess the vibration isolation performance of the single- and two-stage vibration isolators. The results from the dynamic models and the finite element models both show that the vibration isolation performance of the two-stage vibration isolator ring performs better than that of the single-stage vibration isolator ring.

To address low-frequency vibration isolation, an issue that engineers often face, this paper first studies the nonlinear energy transfer of a flexible plate, with arbitrary boundary, with the coupling of high-static-low-dynamic-stiffness (HSLDS) isolator. The nonlinear coupled dynamic equation was derived via the Lagrange method, and the improved Fourier series and Rayleigh–Ritz methods provide modal coefficients of the arbitrary boundary flexible plate with nonlinear vibration isolators. The Galerkin and harmonic balance methods approximate the frequency response functions of power flow for the coupled system. The numerical method, via direct integration of the dynamic equation, validates the analytical results of the frequency response functions. In addition, the finite element simulation, used here, validates the analytical results of the mode shapes for flexible plate. The experiment is carried out to validate the isolation performance of the nonlinear vibrator supported on a flexible plate. On these bases, increasing damping and controlling HSLDS can improve the low-frequency isolation efficiency, and nonlinear jumping-phenomena could disappear over a low-frequency range (either frequency overlap or frequency jump). Hence, a properly configured flexible plate could improve the bearing capacity and low-frequency isolation efficiency while avoiding frequency mistune. An explanation for these is offered in the article.