scholarly journals The Transmissibility of Vibration Isolators With a Nonlinear Antisymmetric Damping Characteristic

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Z. K. Peng ◽  
Z. Q. Lang ◽  
X. J. Jing ◽  
S. A. Billings ◽  
G. R. Tomlinson ◽  
...  
Keyword(s):  
Resonance Frequency ◽  
Frequency Region ◽  
Simulation Studies ◽  
Vibration Isolator ◽  
Linear Vibration ◽  
Output Frequency ◽  
Single Degree Of Freedom ◽  
Vibration Isolators ◽  
Single Degree ◽  
Force Transmissibility

In the present study, the concept of the output frequency response function, recently proposed by the authors, is applied to theoretically investigate the force transmissibility of single degree of freedom (SDOF) passive vibration isolators with a nonlinear antisymmetric damping characteristic. The results reveal that a nonlinear antisymmetric damping characteristic has almost no effect on the transmissibility of SDOF vibration isolators over the ranges of frequencies, which are much lower or higher than the isolator’s resonance frequency. On the other hand, the introduction of a nonlinear antisymmetric damping can significantly reduce the transmissibility of the vibration isolator over the resonance frequency region. The results indicate that nonlinear vibration isolators with an antisymmetric damping characteristic have great potential to overcome the dilemma encountered in the design of passive linear vibration isolators, that is, increasing the level of damping to reduce the transmissibility at the resonance could increase the transmissibility over the range of higher frequencies. These important theoretical conclusions are then verified by simulation studies.

scholarly journals Non-Linear Vibration Isolators with Unknown Excitation and Unmodelled Dynamics: Sliding Mode Active Control

2019 ◽  
Vol 9 (17) ◽  
pp. 3567 ◽  
Author(s):  
Zhang ◽  
Hu ◽  
Liu ◽  
Ouyang ◽  
Zhang
Keyword(s):  
Sliding Mode ◽  
Control Methods ◽  
Practical Application ◽  
Linear Vibration ◽  
Single Degree Of Freedom ◽  
Vibration Isolators ◽  
Single Degree ◽  
Non Linear ◽  
The One ◽  
Twisting Algorithm

For a class of single-degree-of-freedom non-linear passive vibration isolators with unknown excitation and unmodelled dynamics, two sliding mode control methods—a conventional one and the other using a super-twisting algorithm—were proposed to complement and improve the performances and the robustness of the passive isolators. The proposed control methods only require the estimation of the loading and measured velocities of the isolators. Numerical simulations for a non-linear isolator with quasi-zero stiffness demonstrated that both methods were effective and easy to implement, and the one using a super-twisting algorithm was more promising from the perspective of practical application.

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.

Force transmissibility characteristics of a pseudoelastic oscillator

2019 ◽  
Vol 31 (3) ◽  
pp. 349-363 ◽  
Author(s):  
Sebin Jose ◽  
Goutam Chakraborty ◽  
Ranjan Bhattacharyya
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Cooling Rate ◽  
Operating Conditions ◽  
Vibration Isolator ◽  
Resonant Frequencies ◽  
Single Degree Of Freedom ◽  
Thermomechanical Behaviour ◽  
Rigid Mass ◽  
Force Transmissibility

The force transmissibility characteristics of a passive vibration isolator in the form of shape memory alloy bar are investigated. The shape memory alloy bar, together with a rigid mass, constitutes a single-degree-of-freedom system. The force isolation ability of the oscillator is evaluated for both isothermal and convective environmental conditions. The transmissibility curve of an isothermal pseudoelastic oscillator displays single and double jumps depending upon the forcing amplitude. The shape memory alloy oscillator with coupled thermomechanical behaviour depends on the cooling rate near resonant frequencies. Increased cooling rate reduces both peak amplitude and the resonant frequency of the transmissibility curve. The force isolation provided by shape memory alloy oscillator is independent of the operating conditions.

Effectiveness of neoprene pad vibration isolators at high frequencies

2021 ◽  
Vol 263 (4) ◽  
pp. 2172-2183
Author(s):  
Jerry Lilly
Keyword(s):  
Natural Frequency ◽  
Insertion Loss ◽  
Dynamic Stiffness ◽  
Degree Of Freedom ◽  
Frequency Wave ◽  
Single Degree Of Freedom ◽  
High Frequencies ◽  
Vibration Isolators ◽  
Single Degree ◽  
Wide Range

The natural frequency, dynamic stiffness, and insertion loss of commercially available neoprene pad vibration isolators have been measured in a simple, single degree of freedom system over a wide range of pad loadings out to a maximum frequency of 10 kHz. The results reveal that dynamic stiffness can vary significantly with pad loading as well as the durometer of the material. It will also be shown that insertion loss follows the theoretical single degree of freedom curve only out to a frequency that is about 5 to 10 times the natural frequency, depending upon the pad durometer rating. Above that frequency wave resonances in the material cause the insertion loss to deteriorate significantly out to a frequency near 1 kHz, above which the insertion loss maintains a relatively constant value, again depending upon the pad durometer rating. In some instances the insertion loss values can approach 0 dB or even become negative at specific frequencies in the frequency region that is 10 to 20 times the natural frequency of the system.

Analysis of Frequency and Damping Ratio on the Shock Isolation Efficiency

2013 ◽  
Vol 791-793 ◽  
pp. 835-838
Author(s):  
Shi Jie Wu ◽  
Lin He ◽  
Xi Zhi Zhao
Keyword(s):  
Damping Ratio ◽  
Relative Displacement ◽  
Displacement Amplitude ◽  
Vibration Isolator ◽  
Isolation System ◽  
Single Degree Of Freedom ◽  
Absolute Acceleration ◽  
Single Degree ◽  
Acceleration Amplitude ◽  
Shock Isolation

The traditional shock isolation system is only designed in stiffness regardless of damping, which causes acute contradiction between absolute acceleration amplitude and relative displacement amplitude. Based on the single degree of freedom negative shock isolation system, numerical analysis demonstrates that relative little amplitude of absolute acceleration and relative displacement could be attained within a certain range of damping and frequency ratio. Selecting appropriate damping and stiffness of vibration isolator can resolve contradiction between absolute acceleration amplitude and relative displacement amplitude and consequently improve shock isolation efficiency.

Broadband Lg Magnitude

1987 ◽  
Vol 58 (4) ◽  
pp. 125-133 ◽  
Author(s):  
R. B. Herrmann
Keyword(s):  
Correction Term ◽  
Seismic Source ◽  
Degree Of Freedom ◽  
Source Spectrum ◽  
Simulation Studies ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Anelastic Attenuation ◽  
Definition Of ◽  
Insight Into

Abstract The application of the Nuttli (1973) definition of mbLg to observations with periods away from 1.0 seconds as suggested by Boore and Atkinson (1987) and Atkinson and Boore (1987) is studied with emphasis on observations in the 1.0 –10.0 second range and on single degree of freedom seismographs. Simulation studies indicate the efficacy of this usage, but also provides insight into the interrelated effects of the instrument, anelastic attenuation and the seismic source on observed amplitudes. In order to relate a broadband Lg magnitude to the source spectrum, a correction term must be applied to the mLg (f) relation of Herrmann and Kijko (1983).

Application of Viscoelastic Material for a Dynamic Damper

1986 ◽  
Vol 108 (3) ◽  
pp. 378-381 ◽  
Author(s):  
K. J. Kim ◽  
T. I. Yeo
Keyword(s):  
Resonance Frequency ◽  
Viscoelastic Material ◽  
Optimization Procedure ◽  
Degree Of Freedom ◽  
Primary System ◽  
Single Degree Of Freedom ◽  
Dynamic Damper ◽  
Single Degree ◽  
Mass Damper

An optimization procedure in the design of a viscoelastic dynamic damper is proposed for a single-degree-of-freedom primary system with the effects of prestrain taken into account. The performance is compared with that by a conventional spring-dashpot-mass damper. Applicability of the proposed procedure to a resonance-frequency-varying system is also shown.

Sensitivity of Jump Avoidance Condition of Piecewise Linear Vibration Isolator to Dynamical Parameters

2005 ◽  
Author(s):  
Sagar Deshpande ◽  
Sudhir Mehta ◽  
G. Nakhaie Jazar
Keyword(s):  
Piecewise Linear ◽  
System Response ◽  
Structural Constraints ◽  
Vibration Isolator ◽  
Linear Vibration ◽  
Vibration Isolators ◽  
Non Linear ◽  
Dynamical Parameters ◽  
Non Linear System ◽  
Stiffness And Damping

An adapted averaging method is employed to obtain an implicit function for frequency response of a bilinear vibration isolator system under steady state. This function is examined for jump-avoidance and a condition is derived which when met ensures that the undesirable phenomenon of ‘Jump’ does not occur and the system response is functional and unique. The jump avoidance and sensitivity of the condition are examined and investigated as the dynamic parameters vary. The results of this investigation can be directly employed in design of effective piecewise linear vibration isolators. A linear vibration system is defined as one in which the quantities of mass (or inertia), stiffness, and damping are linear in behavior and do not vary with time [1]. Although mathematical models employing a linear ordinary differential equation with constant coefficients portray a simple and manageable system for analytical scrutiny, in most cases they are an incomplete representation simplified for the sake of study. Most real physical vibration systems are more accurately depicted by non-linear governing equations, in which the non-linearity may stem from structural constraints causing a change in stiffness and damping characteristics, or from inherent non-linear behavior of internal springs and dampers. This paper focuses on a general form of such a non-linear system. This study of piecewise-linear systems will allow hazardous system behavior over operating frequency ranges to be gauged and controlled in order to avoid premature fatigue damage, and prolong the life of the system.

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