scholarly journals Design and Theoretical Analysis of High-Static-Low-Dynamic Stiffness Torsion Vibration Isolator Based on Oblique Springs

2021 ◽  
Vol 2101 (1) ◽  
pp. 012028
Author(s):  
Zhirong Yang ◽  
Lintao Li ◽  
Jiacheng Yao ◽  
Qingkai Wang
Keyword(s):  
Harmonic Balance ◽  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Vibration Isolator ◽  
Torsion Vibration ◽  
Low Frequency Vibration ◽  
Torsion Stiffness ◽  
Ihb Method ◽  
Peak Value

Abstract A torsion vibration isolator composed of oblique springs with high-static-low-dynamic stiffness (HSLDS) is proposed to attenuate the transmission of torsion vibration along the shipping shaft in this paper. It is good at in low frequency vibration isolation as it can significantly reduce the resonance frequency of the system with the same load capability. Firstly, the model of HSLDS torsion vibration isolator is introduced in this paper. Secondly, the non-dimensional torsion stiffness is formulated using mechanics theory, and the HSLDS characteristic of designed torsion vibration isolator is verified. Finally, the torque transmissibility is analyzed using the Increment Harmonic Balance (IHB) method, and the effects of the system parameters on it are analyzed. The results show that the resonant frequency increases accordingly as the stiffness ratio and the excitation torque are increased. However, the peak value of the torsion transmissibility is decreased as the damper ratio increasing.

On the Effects of Mistuning a Force-Excited System Containing a Quasi-Zero-Stiffness Vibration Isolator

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Ali Abolfathi ◽  
M. J. Brennan ◽  
T. P. Waters ◽  
B. Tang
Keyword(s):  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Vibration Isolator ◽  
Linear Vibration ◽  
Vibration Isolators ◽  
Zero Dynamic ◽  
Low Frequency Vibration ◽  
Excited System ◽  
Better Than

Nonlinear isolators with high-static-low-dynamic-stiffness have received considerable attention in the recent literature due to their performance benefits compared to linear vibration isolators. A quasi-zero-stiffness (QZS) isolator is a particular case of this type of isolator, which has a zero dynamic stiffness at the static equilibrium position. These types of isolators can be used to achieve very low frequency vibration isolation, but a drawback is that they have purely hardening stiffness behavior. If something occurs to destroy the symmetry of the system, for example, by an additional static load being applied to the isolator during operation, or by the incorrect mass being suspended on the isolator, then the isolator behavior will change dramatically. The question is whether this will be detrimental to the performance of the isolator and this is addressed in this paper. The analysis in this paper shows that although the asymmetry will degrade the performance of the isolator compared to the perfectly tuned case, it will still perform better than the corresponding linear isolator provided that the amplitude of excitation is not too large.

scholarly journals An Air Spring Vibration Isolator Based on a Negative-Stiffness Structure for Vehicle Seat

2021 ◽  
Vol 11 (23) ◽  
pp. 11539
Author(s):  
Cong Hung Nguyen ◽  
Cong Minh Ho ◽  
Kyoung Kwan Ahn
Keyword(s):  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Negative Stiffness ◽  
Vibration Isolator ◽  
Air Spring ◽  
Nonlinear Force ◽  
Mechanical Spring ◽  
Negative Stiffness Mechanism ◽  
Vehicle Seat

This research introduces an air spring vibration isolator system (ASVIS) based on a negative-stiffness structure (NSS) to improve the vehicle seat’s vibration isolation performance at low excitation frequencies. The main feature of the ASVIS consists of two symmetric bellows-type air springs which were designed on the basis of a negative stiffness mechanism. In addition, a crisscross structure with two straight bars was also used as the supporting legs to provide the nonlinear characteristics with NSS. Moreover, instead of using a vertical mechanical spring, a sleeve-type air spring was employed to provide positive stiffness. As a result, as the weight of the driver varies, the dynamic stiffness of the ASVIS can be easily adjusted and controlled. Next, the effects of the dimension parameters on the nonlinear force and nonlinear stiffness of ASVIS were analyzed. A design process for the ASVIS is provided based on the analytical results in order to achieve high static–low dynamic stiffness. Finally, numerical simulations were performed to evaluate the effectiveness of the ASVIS. The results obtained in this paper show that the values of the seat displacement of the ASVIS with NSS were reduced by 77.16% in comparison with those obtained with the traditional air spring isolator without NSS, which indicates that the design of the ASVIS isolator with NSS allows the effective isolation of vibrations in the low-frequency region.

scholarly journals Modeling a Mechanical Molecular Spring Isolator with High-Static-Low-Dynamic-Stiffness Properties

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Zhanyong Li ◽  
Qian Chen ◽  
Fengshou Gu ◽  
Andrew Ball
Keyword(s):  
Vibration Isolation ◽  
Dynamic Properties ◽  
Piecewise Linear ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Isolation System ◽  
Isolation Technique ◽  
Piston Cylinder ◽  
Low Frequency Vibration ◽  
Stiffness Model

A mechanical molecular spring isolator (MMSI) is proposed for the purpose of isolating the low-frequency vibration of a heavy payload. The MMSI is a passive vibration isolation technique mimicking molecular spring isolator characteristics of high-static-low-dynamic stiffness (HSLDS). An MMSI consists of a piston-cylinder container filled with the liquid and some hydraulic spring accumulators. The piston would support a lump of mass and be subjected to a specific external vibration excitation force. Those accumulators can get intercommunication by the liquid to produce the transformation from high static stiffness to low dynamic stiffness. The stiffness model of the MMSI with several identical accumulators is established based on the hydrostatic law. After that, some parameters that significantly influence the stiffness characteristics are studied. Results show that the stiffness property of this kind of MMSI demonstrates a piecewise linearity of three segments. It applies the averaging method to acquire amplitude-frequency and phase-frequency relationships of the piecewise linear vibration isolation system. An inevitable jump phenomenon may occur when the exciting force reaches the critical value. The vibration isolation performance is evaluated by energy transmissibility. Finally, an experimental prototype was designed to carry out quasi-static and dynamic experiments to verify the stiffness model and the dynamic properties as an HSLDS vibration isolator.

scholarly journals Research on a nonlinear quasi-zero stiffness vibration isolator with a vibration absorber

2020 ◽  
Vol 103 (3) ◽  
pp. 003685042094089
Author(s):  
Shao-Hua Li ◽  
Nan Liu ◽  
Hu Ding
Keyword(s):  
Frequency Response ◽  
Vibration Isolation ◽  
Low Frequency ◽  
Vibration Absorber ◽  
Vibration Isolator ◽  
Dynamic Vibration Absorber ◽  
Amplitude Frequency Response ◽  
Low Frequency Vibration ◽  
Response Equation ◽  
Negative Stiffness Mechanism

A negative stiffness mechanism consisting of a spring and cylinder is proposed, and a grounded dynamic vibration absorber is designed based on a quasi-zero stiffness vibration isolator to constitute the vibration isolator with a vibration absorber system. The range of parameters for attaining zero stiffness is derived from static analysis. The dynamic analysis of the vibration isolator with a vibration absorber system is carried out by a multiscale method, and the amplitude–frequency response equation of the system is obtained. The influence of different system parameters on the amplitude–frequency response is analyzed. The amplitude–frequency response of the quasi-zero stiffness vibration isolator is compared with that of the vibration isolator with a vibration absorber, and the linear and nonlinear analytical solutions of the vibration isolator with a vibration absorber system are also compared. The results show that the designed vibration isolator with a vibration absorber is an ideal choice for low-frequency vibration isolation, with no large resonance peak throughout the system and significantly improved reliability of the system.

The design of negative stiffness spring for precision vibration isolation using axially magnetized permanent magnet rings

2019 ◽  
Vol 25 (19-20) ◽  
pp. 2667-2677 ◽  
Author(s):  
Zhenhua Zhou ◽  
Shuhan Chen ◽  
Dun Xia ◽  
Jianjun He ◽  
Peng Zhang
Keyword(s):  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Design Procedure ◽  
Air Gap ◽  
Negative Stiffness ◽  
Linear Component ◽  
Vibration Isolator ◽  
Stiffness Characteristic ◽  
Isolation Performance

A negative stiffness element is always employed to generate high-static–low-dynamic stiffness characteristic of the vibration isolator, reduce the resonance frequency of the isolator, and improve the vibration isolation performance under low and ultra-low frequency excitation. In this paper, a new compact negative stiffness permanent magnetic spring (NSPMS) that is composed of two axial-magnetized permanent magnetic rings is proposed. An analytical expression of magnetic negative stiffness of the NSPMS is deduced by using the Coulombian model. After analyzing the effect of air-gap width, air-gap position, height difference between the inner ring and outer ring on the negative stiffness characteristic, a design procedure is proposed to realize the negative stiffness characteristic with a global minimum linear component and uniformity stiffness near the equilibrium position. Finally, an experimental prototype is developed to validate the effectiveness of the NSPMS. The experimental results show that combining a vibration isolator with the NSPMS in parallel can lower the natural frequency and improve the isolation performance of the isolator.

scholarly journals Dynamic characterization of controlled multi-channel semi-active magnetorheological fluid mount

2021 ◽  
Vol 12 (2) ◽  
pp. 751-764
Author(s):  
Zhihong Lin ◽  
Mingzhong Wu
Keyword(s):  
High Frequency ◽  
Optimization Design ◽  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Vehicle Model ◽  
Mr Fluid ◽  
Unbalanced Force ◽  
Low Frequency Vibration ◽  
Engine Mount

Abstract. In this paper, a novel structure of a controlled multi-channel semi-active magnetorheological (MR) fluid mount is proposed, including four controlled channels and one rate-dip channel. Firstly, the magnetic circuit analysis, rate-dip channel optimization design, and MR fluid mount damping analysis are given. Secondly, the mathematical model of the controlled multi-channel semi-active MR fluid mount is constructed. We analyze the effect of controlled multi-channel closing on the dynamic characteristics of the mounts and the effect of the presence or absence of the rate-dip channel on the low-frequency isolation of the mount. Finally, the controlled multi-channel semi-active MR fluid mount was applied to the 1/4 vehicle model (a model consisting of an engine, a single engine mount, a single suspension and a vehicle frame), with the transmissibility of the engine relative to the vehicle frame at low frequency and the transmissibility of the engine reciprocating unbalanced force to the vehicle frame magnitude at high frequency as the evaluation index. Numerical simulation shows the following points. (1) The controllable multi-channel semi-active MR fluid mount can achieve adjustable dynamic stiffness and damping with applied 2 A current to different channels. (2) With known external excitation source, applied currents to different controllable channels can achieve the minimum transmissibility and meet the mount wide-frequency vibration isolation requirement, while adding a rate-dip channel can improve the low-frequency vibration isolation performance of the MR fluid mount. (3) Switching and closing different controllable channels in the 1/4 vehicle model can achieve the minimum transmissibility of low-frequency engine vibrations relative to the vehicle frame and high-frequency engine vibrations reciprocating an unbalanced force to the vehicle frame. Therefore, the design of the controllable multi-channel semi-active MR fluid mount can meet the wide-frequency isolation.

scholarly journals Nonlinear Dynamic Study of Oscillation System Featuring Quasi-Zero and Asymmetric Stiffness

2021 ◽  
Author(s):  
Thanh Danh Le ◽  
Minh Ky Nguyen ◽  
Ngoc Yen Phuong Vo
Keyword(s):  
Vibration Isolation ◽  
Sliding Friction ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Force Model ◽  
Oscillation System ◽  
Time Dynamic ◽  
Bifurcation Phenomenon ◽  
Low Frequency Vibration ◽  
Approximate Polynomial

Abstract This paper will broaden our previous works about the asymmetric and quasi-zero stiffness oscillator named AQZSO. In this paper, the dynamic stiffness of the AQZSO will be investigated. Then, the condition for which the minimum dynamic stiffness is quasi-zero around the equilibrium position is also determined. By using Multi-Scale method, the fundamental resonance response of the AQZSO subjected to the vibrating base is analyzed, in which the dynamic stiffness is expressed as a fifth-order approximate polynomial through expanding Taylor series. The stability of the response is then found out via nonlinear Routh-Herwitz criterion. Moreover, because of existing the sliding friction between the cylinder and piston, the nonlinear and varying-time dynamic characteristics, the complex dynamic response of the AQZSO is the need for discovery by performing direct integration of the original dynamic equation through using 5th-order Runge-Kutta algorithm. In this work, the friction force model of cylinder will be identified through virtual prototyping technique and genetic algorithm. Additionally, the Poincáre map is also employed to analyze the bifurcation phenomenon, coexistence of multiple solutions. The traction basin of the period-1, period-2 and period-3 solution is determined, indicating that the attractor basin is influenced by the asymmetric of the stiffness curve. This research will offer a useful insight to design low frequency vibration isolation systems.

Comparative Testing on Ground Surface Vibration Caused by CRH Trains Running on Viaduct and Embankment

2011 ◽  
Vol 347-353 ◽  
pp. 349-353
Author(s):  
Kun Ming Mao ◽  
Guo Xing Chen ◽  
Yang Zhang ◽  
Xiao Xing Hong ◽  
Bin Ruan
Keyword(s):  
Vibration Isolation ◽  
Low Frequency ◽  
Ground Surface ◽  
Vibration Velocity ◽  
Attenuation Curve ◽  
Main Frequency ◽  
Vibration Intensity ◽  
Surface Vibration ◽  
Low Frequency Vibration ◽  
Peak Value

Based on the measurement of the vertical velocity of ground surface vibration caused by CRH trains running on viaduct and embankment of Hu-Ning Intercity Railway, the characteristics and propagation attenuation rules of the ground surface vibration of two routes are analyzed. The result shows that the main frequency of ground surface vibration caused by the CRH trains running is less than 80Hz, which belongs to low frequency vibration. The number of carriages has little effect on ground surface vibration intensity. The effect of train speed for 153km/h to 201km/h on ground surface vibration intensity has no obvious difference. With the increased distance between the ground surface and the track, the main frequency of ground surface vibration on viaduct decreases, and the attenuation curve of peak value of ground surface vibration velocity becomes smoother. However, the main frequency of ground surface vibration on embankment is nearly unchanged and the attenuation curve of peak value of ground surface vibration velocity has several rebound regions of the vibration. Ground surface vibration intensity of viaduct is higher than that of embankment. The drainage trench built beside the embankment has vibration isolation effect on ground surface vibration.

scholarly journals Research and Analysis of Quasi-Zero-Stiffness Isolator with Geometric Nonlinear Damping

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Qingguo Meng ◽  
Xuefeng Yang ◽  
Wei Li ◽  
En Lu ◽  
Lianchao Sheng
Keyword(s):  
Vibration Isolation ◽  
Low Frequency ◽  
Harmonic Balance Method ◽  
Nonlinear Damping ◽  
Vibration Isolator ◽  
Rehabilitation Robots ◽  
Geometric Nonlinear ◽  
Low Frequency Vibration ◽  
Linear Spring ◽  
The Relationship

This paper presents a novel quasi-zero-stiffness (QZS) isolator designed by combining a tension spring with a vertical linear spring. In order to improve the performance of low-frequency vibration isolation, geometric nonlinear damping is proposed and applied to a quasi-zero-stiffness (QZS) vibration isolator. Through the study of static characteristics first, the relationship between force displacement and stiffness displacement of the vibration isolation mechanism is established; it is concluded that the parameters of the mechanism have the characteristics of quasi-zero stiffness at the equilibrium position. The solutions of the QZS system are obtained based on the harmonic balance method (HBM). Then, the force transmissibility of the QZS vibration isolator is analyzed. And the results indicate that increasing the nonlinear damping can effectively suppress the transmissibility compared with the nonlinear damping system. Finally, this system is innovative for low-frequency vibration isolation of rehabilitation robots and other applications.

scholarly journals Methods for Measuring the Dynamic Stiffness of Resilient Rail Fastenings for Low Frequency Vibration Isolation of Railways, Their Problems and Possible Solutions

2005 ◽  
Vol 24 (2) ◽  
pp. 107-115 ◽  
Author(s):  
Chris Morison ◽  
Anbin Wang ◽  
Oliver Bewes
Keyword(s):  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Inertial Force ◽  
Transport Systems ◽  
Frequency Range ◽  
Low Frequency Vibration ◽  
Urban Rail ◽  
Low Stiffness ◽  
European Standards

Low frequency ground or structure-borne sound and vibration emission from urban rail transport systems can be greatly reduced by reducing the stiffness of the rail fastening. Estimates and models of the efficacy of such systems require accurate measurements of their dynamic stiffness over the frequency range of interest, and European Standards make recommendations for such measurements. This paper describes these methods and their shortcomings when applied to modern complete assemblies with low stiffness, one problem of which is the contribution of inertial forces at frequencies approaching and above the natural resonance of the system. This paper suggests a method for correcting for this inertial force, and tests this correction with the driving point method of dynamic stiffness measurement when applied to the Pandrol VANGUARD resilient rail fastening. The preliminary tests effectively triple the frequency range of valid measurements, a result which could be improved when applied to stiffer systems or with further improvements to the test equipment.

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