A quasi-zero-stiffness isolator with a shear-thinning viscous damper

Quasi-zero-stiffness(QZS) vibration isolators have been widely studied,because they show excellent high static and low dynamic stiffnesses and can effectively solve low-frequency and ultralow-frequency vibration. However, traditional QZS(T-QZS)vibration isolators usually adopt linear damping, owing to which achieving good isolation performance at both low and high frequencies is difficult. T-QZS isolators exhibit hardening stiffness characteristics, and their vibration isolation performance is e...     

Superharmonic resonance of the quasi-zero-stiffness vibration isolator and its effect on the isolation performance

Nonlinear Dynamics - Quasi-zero-stiffness (QZS) vibration isolator seeks better isolation performance by lowering the natural frequency while maintaining the same static load bearing capacity as...     

Performance analysis of a nonlinear inerter-based vibration isolator with inerter embedded in a linkage mechanism

This study presents an inerter-based nonlinear vibration isolator with geometrical nonlinearity created by configuring an inerter in a diamond-shaped linkage mechanism. The isolation performance of the proposed nonlinear isolator subjected to force or base-motion excitations is investigated. Both analytical and alternating frequency-time harmonic balance methods as well as numerical integration method are used to obtain the dynamic response. Beneficial performance of the nonlinear isolator is demonstrated by various performance indices including the force and displacement transmissibility as well as power flow variables. It is found that the use of the nonlinear inerter in the isolator can shift and bend the peaks of the transmissibility and time-averaged power flow to the low-frequency range, creating a larger frequency band of effective vibration isolation. It is also shown that the inertance-to-mass ratio and the initial distance of the nonlinear inerter can be effectively tailored to achieve reduced transmissibility and power transmission at interested frequencies. Anti-resonant peaks appear at specific frequency, creating near-zero energy transmission and significantly reducing vibration transmission to a base structure on which the proposed isolator is mounted.

     

On the dynamics of a vibration isolator with geometrically nonlinear inerter

Nonlinear Dynamics - The inerter is a two-terminal mechanical element that produces forces directly proportional to the relative acceleration between these terminals. The linear behaviour of this...     

A nonlinear vibration isolator supported on a flexible plate: analysis and experiment

Nonlinear Dynamics - 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...     

Accurate modeling and analysis of a typical nonlinear vibration isolator with quasi-zero stiffness

Nonlinear Dynamics - A typical quasi-zero stiffness (QZS) vibration isolator composed of two lateral springs and a vertical spring has been widely studied previously, aiming to widen the frequency...     

Cascaded quasi-zero stiffness nonlinear low-frequency vibration isolator inspired by human spine

Human motion induced vibration has very low frequency, ranging from 2 Hz to 5 Hz. Traditional vibration isolators are not effective in low-frequency regions due to the trade-off between the low natural frequency and the high load capacity. In this paper, inspired by the human spine, we propose a novel bionic human spine inspired quasi-zero stiffness (QZS) vibration isolator which consists of a cascaded multi-stage negative stiffness structure. The force and stiffness characteristics are investigated first, the dynamic model is established by Newton’s second law, and the isolation performance is analyzed by the harmonic balance method (HBM). Numerical results show that the bionic isolator can obtain better low-frequency isolation performance by increasing the number of negative structure stages, and reducing the damping values and external force values can obtain better low-frequency isolation performance. In comparison with the linear structure and existing traditional QZS isolator, the bionic spine isolator has better vibration isolation performance in low-frequency regions. It paves the way for the design of bionic ultra-low-frequency isolators and shows potential in many engineering applications.

     

Force and displacement transmissibility of a quasi-zero stiffness vibration isolator with geometric nonlinear damping

A geometric nonlinear damping is proposed and applied to a quasi-zero stiffness (QZS) vibration isolator with the purpose of improving the performance of low-frequency vibration isolation. The force, stiffness and damping characteristics of the system are presented first. The steady-state solutions of the QZS system are obtained based on the averaging method for both force and base excitations and further verified by numerical simulation. The force and displacement transmissibility of the QZS vibration isolator are then analysed. The results indicate that increasing the nonlinear damping can effectively suppress the force transmissibility in resonant region with the isolation performance in higher frequencies unaffected. In addition, the application of the nonlinear damping in the QZS vibration isolator can essentially eliminate the unbounded response for the base excitation. Finally, the equivalent damping ratio is defined and discussed from the viewpoint of vibration control.     

Nonlinear vibration of a slightly curved beam with quasi-zero-stiffness isolators

Nonlinear Dynamics - Bending vibration of isolated structures has always been neglected when the vibration isolation was studied. Isolated structures have usually been treated as discrete systems....     

A magneto-rheological elastomer vibration isolator for lightweight structures

Meccanica - Magneto-rheological elastomers (MRE), consisting of elastomeric matrix containing ferromagnetic particles, are a kind of smart material, whose mechanical properties are controllable via...     

A bio-inspired spider-like structure isolator for low-frequency vibration

This paper proposes a quasi-zero stiffness(QZS) isolator composed of a curved beam(as spider foot) and a linear spring(as spider muscle) inspired by the precise capturing ability of spiders in vibrating environments. The curved beam is simplified as an inclined horizontal spring, and a static analysis is carried out to explore the effects of different structural parameters on the stiffness performance of the QZS isolator. The finite element simulation analysis verifies that the QZS isolator can ...     

Dynamics and isolation properties for a pneumatic near-zero frequency vibration isolator with nonlinear stiffness and damping

Nonlinear Dynamics - Aiming to isolate disturbance vibration for heavy machines with low frequency, a novel hydro-pneumatic vibration isolator with high-static and low-dynamic (HSLD) stiffness is...     

Design of a metastructure for vibration isolation with quasi-zero-stiffness characteristics using bistable curved beam

Nonlinear Dynamics - This work designs and analyzes a metastructure-based vibration isolation model to improve small-scale equipment's isolation effectiveness under low-frequency excitations....     

Limb-inspired bionic quasi-zero stiffness vibration isolator

Acta Mechanica Sinica - Vibration reduction has always been one of hot and important topics in mechanical engineering, especially for the special measurement instrument. In this paper, a novel...     

A 6-DOF passive vibration isolator based on Stewart structure with X-shaped legs

By employing the nonlinear stiffness and damping characteristics of a bio-inspired X-shaped structure (XSS) with passive springs and the Stewart platform with six degrees of freedom, a passive 6-DOF vibration isolation platform is designed and experimentally studied for its vibration isolation performance. A three-layer asymmetrical XSS is adopted as legs to construct a passive Stewart platform. Because of the specially designed XSS, the stiffness and damping properties of the system can be adjusted by changing structural parameters and thus it is designable to achieve an excellent performance including excellent stability and high-static-low-dynamic-stiffness isolation effect in all six directions with satisfactory loading capacity in the vertical direction, without any active control. Analytical and extensive experimental analysis of static stiffness and vibration response of the system revealed that (a) the aXSS Stewart platform has very beneficial high static nonlinear stiffness which can provide sufficient loading capacity; (b) the platform can achieve very low dynamic stiffness in each direction without losing loading capacity; (c) both static and dynamic stiffness is adjustable and designable with structure parameters and very easy to implement in a pure passive manner.     

Identification of nonlinear anti-vibration isolator properties

Vibrations are classified among the major problems for engineering structures. Anti-vibration isolators are used to absorb vibration energy and minimise transmitted force which can cause damage. The isolator is modelled as a parallel combination of stiffness and damping elements. The main purpose of the model is to enable designers to predict the dynamic response of systems under different structural excitations and boundary conditions. A nonlinear identification method, discussed in this paper, aims to provide a tool for engineers to extract information about the nonlinear dynamic behaviour using measured data from experiments. The proposed method is demonstrated and validated with numerical simulations. Thus, this technique is applied to determine the nonlinear parameters of a commercial metal mesh isolator. Nonlinear stiffness and nonlinear damping can decrease with the increase in the amplitude of the base excitation. The softening behaviour of the mesh isolator is clearly visible.     

An active high-static-low-dynamic-stiffness vibration isolator with adjustable buckling beams: theory and experiment

High-static-low-dynamic-stiffness(HSLDS) vibration isolators with buckling beams have been widely used to isolate external vibrations. An active adjustable device composed of proportion integration(PI) active controllers and piezoelectric actuators is proposed for improving the negative stiffness stroke of buckling beams. A nonlinear output frequency response function is used to analyze the effect of the vibration reduction.The prototype of the active HSLDS device is built, and the verification ...     

A state-of-the-art review on low-frequency nonlinear vibration isolation with electromagnetic mechanisms

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.

     

Analysis and design of a novel and compact X-structured vibration isolation mount (X-Mount) with wider quasi-zero-stiffness range

Nonlinear Dynamics - Passive vibration isolation is always preferable in most engineering practices. To this aim, a novel, compact and passive vibration isolation mount is studied in this paper,...