An Improved Structural Analysis Method for Isolator with Quasi-Zero-Stiffness Characteristic

A typical quasi-zero-stiffness (QZS) vibration isolator consisting of a vertical spring and two oblique springs has been widely researched on its static and dynamic characteristics. A general criterion for determining structural parameters of QZS isolator is to achieve low nondimensional stiffness around the equilibrium position. However, lower nondimensional stiffness of linear isolator means lower isolation frequency, which may be invalid on QZS isolator. Because there is an implicit relationship between geometric parameter and stiffness ratio of QZS isolator, this study presents an improved optimization criterion for determining the optimal structural parameters of the typical QZS isolator. The optimization criterion is that the QZS isolator has the maximum displacement range around the equilibrium position without exceeding given natural frequency, rather than given nondimensional stiffness. The results show that isolator with these optimal parameters can achieve lower stiffness around the equilibrium position and better vibration isolation performance. Furthermore, an extended QZS isolator consisting of vertical spring with fixed stiffness and prestressed oblique springs is discussed to further improve stiffness characteristic. Better stiffness performance can be obtained when the prestressed oblique springs have softening stiffness and the exponent of the nonlinear stiffness is 2. Considering the existence of friction in practical application, the influence of friction on both static and dynamic characteristics is investigated. The analysis reveals that friction has little influence on its stiffness characteristic around the static equilibrium position and friction damping produced by friction affects the response amplitude and resonant frequency in dynamics.

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Design and analysis of a vibration isolation system with cam–roller–spring–rod mechanism

Journal of Vibration and Control ◽

10.1177/10775463211000516 ◽

2021 ◽

pp. 107754632110005

Author(s):

Yonglei Zhang ◽

Guo Wei ◽

Hao Wen ◽

Dongping Jin ◽

Haiyan Hu

Keyword(s):

Vibration Isolation ◽

Dynamic Stiffness ◽

Experimental Studies ◽

Excitation Amplitude ◽

Isolation System ◽

Vibration Isolation System ◽

Stiffness Characteristic ◽

Negative Stiffness Mechanism ◽

Isolation Systems ◽

Vibration Isolation Performance

The vibration isolation system using a pair of oblique springs or a spring-rod mechanism as a negative stiffness mechanism exhibits a high-static low-dynamic stiffness characteristic and a nonlinear jump phenomenon when the system damping is light and the excitation amplitude is large. It is possible to remove the jump via adjusting the end trajectories of the above springs or rods. To realize this idea, the article presents a vibration isolation system with a cam–roller–spring–rod mechanism and gives the detailed numerical and experimental studies on the effects of the above mechanism on the vibration isolation performance. The comparative studies demonstrate that the vibration isolation system proposed works well and outperforms some other vibration isolation systems.

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Design and Amplitude Dependence of Resonance Frequency of Origami-Inspired Vibration Isolators With Quasi-Zero-Stiffness Characteristic

Volume 7: 32nd Conference on Mechanical Vibration and Noise (VIB) ◽

10.1115/detc2020-22171 ◽

2020 ◽

Author(s):

Kouya Yamaguchi ◽

Sachiko Ishida

Keyword(s):

Vibration Isolation ◽

Amplitude Dependence ◽

Vibration Isolators ◽

Stiffness Characteristic ◽

Resonance Frequencies ◽

Tensile Forces ◽

Linear Spring ◽

Compression Springs ◽

Mechanical Elements ◽

Vibration Isolation Performance

Abstract This study aims to design two types of vibration isolators, with different spring mechanisms, using a foldable structure that is based on a cylinder torsional buckling pattern, and evaluate the vibration isolation performance of each design. Vibration isolation is achieved through nonlinear spring characteristics of the isolators, which have zero spring stiffness, achieved by attaching a linear spring to the foldable isolator structure. The two vibration isolators differ in the mechanical elements that constitute the foldable structure, which undergo tensile forces as the structure folds. For the first isolator, the mechanical elements are represented only by tension springs, which appropriately undergo tension. For the second isolator, the mechanical elements are designed so that embedded compression springs within the elements compress under tension, thus enabling the elements to work as tension springs. The excitation experiment results revealed that the different spring mechanisms produced equivalent resonance frequencies but different damping effects at the resonance and higher frequencies. When oscillations with multiple amplitudes were input, larger input amplitudes were found to correspond to lower resonance frequencies for both isolators. This trend contradicts that described in the nonlinear vibration theory modeled by the Duffing equation, and was determined to be caused by hysteresis of the spring phenomena in the vibration isolators.

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Static and Dynamic Characteristics of Resilient Mats for Vibration Isolation of Railway Tracks

Procedia Engineering ◽

10.1016/j.proeng.2016.08.122 ◽

2016 ◽

Vol 153 ◽

pp. 317-324 ◽

Cited By ~ 11

Author(s):

Cezary Kraśkiewicz ◽

Cezary Lipko ◽

Monika Płudowska ◽

Wojciech Oleksiewicz ◽

Artur Zbiciak

Keyword(s):

Dynamic Characteristics ◽

Vibration Isolation ◽

Static And Dynamic Characteristics ◽

Railway Tracks

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KNITTED MATERIALS CAPACITY FOR VIBRATION PROTECTION APPLICATIONS

TEXTEH Proceedings ◽

10.35530/tt.2019.01 ◽

2019 ◽

Vol 2019 ◽

pp. 6-9

Author(s):

MIRELA BLAGA ◽

Neculai-Eugen SEGHEDIN

Keyword(s):

Vibration Isolation ◽

Natural Frequencies ◽

Structural Parameters ◽

Free Vibrations ◽

Knitted Fabrics ◽

Vibration Absorption ◽

Spacer Fabric ◽

Sense Of Touch ◽

Vibration Isolation Performance ◽

Isolation Performance

The present work is a synthesis of the author’s previous research on weft and warp knitted fabrics response under dynamic stress and their capacity of vibration damping. The main objective of this research is to experimentally investigate the vibration behaviour of these fabrics with an existing testing method, in order to understand how the fabric structural parameters affect their vibration isolation performance. The authors have focused their interest on the knitted fabrics characterization through their natural frequencies, which were determined by employing the free vibrations method. The natural frequency is the rate at which an object vibrates when it is not disturbed by an outside force. A comparative fabrics analysis of the measured natural frequencies is performed and the main parameters of influence are discussed. An ideal knitted spacer fabric developed for anti-vibration purposes, should have the capacity of absorb energy efficiently, still having sufficient stiffness to avoid its collapse and an acceptable thickness in order to maintain a sense of touch and dexterity to complete the tasks. The preliminary results confirmed that knitted fabrics can be engineered and exploited as structures with vibration absorption capabilities.

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Dynamic Characteristics Research of Magneto-Rheological Fluid Engine Mount

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.752-753.913 ◽

2015 ◽

Vol 752-753 ◽

pp. 913-917

Author(s):

Gong Yu Pan ◽

Qian Qian Wang ◽

Xin Yang

Keyword(s):

Dynamic Characteristics ◽

Vibration Isolation ◽

Dynamic Stiffness ◽

Simulation Software ◽

New Type ◽

Engine Mount ◽

Magneto Rheological ◽

Stiffness And Damping ◽

Vibration Isolation Performance ◽

Isolation Performance

In order to improve the vibration isolation performance of engine mount, a new type of magneto-rheological semi-active mount with multiple inertia tracks is designed based on the existing magneto-rheological semi-active mount . The mechanical model is established according to the mount. The expression of the dynamic stiffness and damping lag angle is deduced, then the dynamic characteristics is simulated in the simulation software. At the same time, verify this model correct by the experiments.

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Analysis of static and dynamic characteristics of spiral-grooved gas journal bearings in high speed

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406219869751 ◽

2019 ◽

Vol 233 (19-20) ◽

pp. 6774-6792 ◽

Cited By ~ 1

Author(s):

Laiyun Song ◽

Kai Cheng ◽

Hui Ding ◽

Shijin Chen ◽

Qiang Gao

Keyword(s):

Dynamic Characteristics ◽

High Speed ◽

Load Capacity ◽

Structural Parameters ◽

Dynamic Stiffness ◽

Journal Bearings ◽

Linear Perturbation ◽

Static And Dynamic Characteristics ◽

Gas Bearings ◽

Spiral Grooves

The spiral grooves structures could promote load capacity and improve stability of the gas journal bearings working in high-speed condition. In this study, the unsteady Reynolds equation is solved by linear perturbation method and finite difference method in which the mesh of the groove region is specially treated. The static and dynamic characteristics of spiral grooves journal gas bearings are investigated in different working conditions and the pumping effect caused by spiral-groove structure is revealed and analyzed. Further, the influences of groove structural parameters on the dynamic stiffness and damping coefficients are studied and discussed, which provides guidelines for the design of the journal gas bearings with spiral grooves.

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Two-dimensional pressure control valve

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/095440620121500903 ◽

2001 ◽

Vol 215 (9) ◽

pp. 1031-1038 ◽

Cited By ~ 4

Author(s):

J Ruan ◽

R Burton ◽

P Ukrainetz ◽

Y. M. Xu

Keyword(s):

Dynamic Characteristics ◽

Structural Parameters ◽

Control Valve ◽

Response Speed ◽

Pressure Control ◽

Large Reynolds Number ◽

Two Dimensional ◽

Load Pressure ◽

Static And Dynamic Characteristics ◽

Pressure Control Valve

The two-dimensional pressure control valve is a piloted control valve which functions by using both linear and rotary motions of a single spool. A groove on the spool land, incorporating a sensing channel, forms the pilot stage to control the pressure of a spool chamber, while the load pressure is fed to the other spool chamber. To sustain the balance of the force across the spool, the load pressure must follow the change of pressure variation along the groove while the spool is in rotary motion. The geometric parameters of the groove and the spool-to-sleeve clearance have significant effects on both the static and dynamic characteristics of the valve. Increasing the sectional size of the groove results in a large Reynolds number and the static property of the valve thus changes from that of linearity owing to the entrance effect. The linearity of the static property is also affected by the leakage through the spool-to-sleeve clearance. The dynamic characteristics of the valve are dependent upon both the structural parameters and the tune constant of the load. The stability and dynamic response were investigated under different structural parameters and time constants of the load using both linear theory and simulation methods. Experiments were designed to obtain the static and dynamic characteristics of the valve and the leakage through the pilot. A balance should be made between the linearity of the static property and the response speed; it was found that both fairly linear static and desired dynamic characteristics could be simultaneously maintained for the two-dimensional pressure control valve.

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Study on dynamic characteristics of bio-inspired vibration isolation platform

Journal of Vibration and Control ◽

10.1177/1077546321993614 ◽

2021 ◽

pp. 107754632199361

Author(s):

Yong Song ◽

Chong Zhang ◽

Zhanlong Li ◽

Yue Li ◽

Jinyi Lian ◽

...

Keyword(s):

Dynamic Characteristics ◽

Periodic Motion ◽

Vibration Isolation ◽

Structural Parameters ◽

Body Movement ◽

Nonlinear Energy Sink ◽

The Body ◽

Object A ◽

Time Frequency ◽

Resonant Phenomenon

Inspired by the body movement of the kangaroo, a multi-degree-of-freedom vibration isolation platform containing three units, that is, a protected object, a nonlinear energy sink, and an X-shaped structure, has been modeled, and the differential equations of the system have been given in the form of uniform relative coordinates. Furthermore, the displacement transmissibility analysis and numerical calculation are supported by the method of harmonic balance and Runge–Kutta algorithm, which shows that (a) there are nonlinear behaviors and resonant phenomenon in the time–frequency response and (b) quasi-periodic motion may be a predictor of periodic steady-state response or strong resonance, and the displacement evolution before quasi-periodic motion may be used to distinguish the two phenomena. In addition, based on the numerical method, the system energy changes in a selected frequency are discussed. Finally, the correctness of the theoretical analysis is verified by simulation data in Adams. Taken together, these results demonstrate that the dynamic characteristics are adjustable and designable of structural parameters in a specific frequency band and can provide a useful way to reduce the amplitude of resonant peaks and improve the vibration isolation performance for practical engineering applications.

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