oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Lever mechanism for vibration isolation  [cached]
Kuinian Li,Mitchell Gohnert
Applied Technologies and Innovations , 2010,
Abstract: By introducing lever mechanism into the conventional vibration isolation system, new vibration isolation systems such as lever-damper isolator (LDI), lever-spring isolator (LSI) and lever-spring-mass isolator (LSMI) can be developed. The transmissibility of LDI, transmissibility of LSI and that of LSMI are obtained analytically. With numerical simulation, the vibration isolation performance of these systems and the effect of parameters on the performance are investigated. The results show that the performance of traditional vibration isolator can be improved by the introducing of lever mechanism. The results also show that the new systems have less constraint in design.
Research on Vibration Isolation Systems Used in Laser and Nanotechnologies  [cached]
Justinas Kunc?,Mindaugas Jurevi?ius
Science – Future of Lithuania , 2012,
Abstract: The paper discusses the efficiency of a vibration isolation system made of the optical table and two negative-stiffness tables and considers excitation referring to harmonic and nonharmonic methods in the frequency range of 0,2–110 Hz. The article reviews the types and sources of vibrations and types of vibration isolation systems, including those of negative-stiffness. The paper also presents the methodology of experimental tests and proposes research on vibration transmissibility. A composite system consisting of two vibration isolation table having negative stiffness and an air table has been tested. The results and conclusions of experimental analysis are suggested at the end of the article.Article in Lithuanian
考虑载荷变化的准零刚度隔振器动态特性
Dynamic Analysis of Quasi-Zero-Stiffness Vibration Isolator Considering Load Variation
 [PDF]

程春,李舜酩,王勇,江星星
- , 2017, DOI: 10.16450/j.cnki.issn.1004-6801.2017.04.017
Abstract: 为了研究载荷变化对准零刚度隔振器动态特性及隔振性能的影响,首先,分析具有分段非线性特性的准零刚度隔振器静力学特性;其次,引入光滑函数,应用增量谐波平衡法得到准零刚度隔振器的周期解,分析载荷与激励幅值对隔振器动态特性的影响;最后,定义准零刚度隔振器的力传递率,分析载荷与激励幅值对其隔振性能的影响。研究结果表明:当激励幅值较大时,载荷变化会导致响应的常数项在共振区附近出现交叉折叠的现象;载荷与激励幅值的变化会改变隔振系统的共振频率、传递率峰值以及有效隔振频带,但该准零刚度隔振器的隔振性能仍优于线性隔振器。
In order to investigate the effect of load variation on the quasi-zero-stiffness(QZS) vibration isolator, firstly, the statics of a QZS vibration isolator with piecewise nonlinear characteristic is analyzed. Then, the smoothing function is introduced here and the periodic solutions of the QZS vibration isolator are obtained using incremental harmonic balance(IHB) method. The effects of load and excitation amplitude on the dynamic characteristics are studied. Finally, the force transmissibility of the QZS vibration isolator is defined. And the effects of load and excitation amplitude on the isolation performance are investigated. The results show that the cross and folding phenomenon occurs in the constant term of the amplitude-frequency curves near the resonance region when the excitation amplitude is relatively large; The variations of load and excitation amplitude lead to the changes of resonance frequency, peak value of transmissibility and vibration isolation frequency band. However, the QZS vibration isolator still outperforms the corresponding linear counterpart.
Multi-Nested Pendula: a new concept for vibration isolation and its application to gravitational wave detectors  [PDF]
Odylio D. Aguiar,Marcio Constancio Jr
Physics , 2013,
Abstract: Adequate vibration isolation is of great importance for the design of any sensitive experiment measuring mechanical motions. The so-called multistage or multipole mechanical low pass filter is a common artifact used for the construction of highly effective vibration isolation. However, the problem with it is the vertical clearance needed inside the vacuum chambers for the construction of numerous, long pendulum stages necessary for effective horizontal vibration isolation. The purpose of this work is to introduce a new concept, called the multi-nested pendula concept, which solves this problem. The attenuation performance of an ideal multistage nested pendula filter is better than that of an ideal multistage common equal pendula filter by a factor of N^{N}, where N is the number of stages used, making this idea of a multi-nested pendula a very interesting one. The initial results (of stability and system resonances) measured for a prototype reinforce the viability of the practical implementation of such idea. A detailed study for the realization of a cryogenic and fully operational version to be used in LIGO is going to be done in a future study.
Design and research of chaotic vibration isolation system under the condition of small displacement
小位移条件下混沌隔振装置的设计与研究

Jiang Guo-Ping,Tao Wei-Jun,Huan Shi,Xiao Bo-qi,
蒋国平
,陶为俊,浣石,肖波齐

物理学报 , 2012,
Abstract: A chaotic vibration isolation device under the condition of small displacement is designed according to the chaotic vibration theory.The device can generate strong nonlinearity under small displacement. The linear part and the nonlinear part are completely separated. The overall stiffness, the ratio of linear term to nonlinear term can be easily adjusted. The engineering application scope of the device turns wider. The numerical simulation is carried out with specific parameters. The design is confirmed.
Fermion Resonances on a Thick Brane with a Piecewise Warp Factor  [PDF]
Hai-Tao Li,Yu-Xiao Liu,Zhen-Hua Zhao,Heng Guo
Physics , 2010, DOI: 10.1103/PhysRevD.83.045006
Abstract: In this paper, we mainly investigate the problems of resonances of massive KK fermions on a single scalar constructed thick brane with a piecewise warp factor matching smoothly. The distance between two boundaries and the other parameters are determined by one free parameter through three junction conditions. For the generalized Yukawa coupling $\eta\bar{\Psi}\phi^{k}\Psi$ with odd $k=1,3,5,...$, the mass eigenvalue $m$, width $\Gamma$, lifetime $\tau$, and maximal probability $P_{max}$ of fermion resonances are obtained. Our numerical calculations show that the brane without internal structure also favors the appearance of resonant states for both left- and right-handed fermions. The scalar-fermion coupling and the thickness of the brane influence the resonant behaviors of the massive KK fermions.
Numerical Analysis of Vibration Isolation Using Pile Rows against the Vibration due to Moving Loads in a Viscoelastic Medium  [PDF]
Bin Xu,Man-Qing Xu
International Journal of Engineering Mathematics , 2014, DOI: 10.1155/2014/810525
Abstract: A numerical method for evaluating the vertical vibration isolation effect of pile rows embedded in a viscoelastic half space subjected to a moving load is developed in this paper on the basis of the Cole-Cole model and Muki’s method. Based on the proposed method, the influence of various parameters on the vibration isolation effect of pile rows embedded in the viscoelastic half space is investigated numerically. 1. Introduction Vibration induced by railway traffic is a major concern for civil engineers as it causes annoyance to residents or even damage to adjacent structures. Generally, the effects of ground vibrations can be mitigated by two kinds of vibration isolation methods: the active and the passive vibration isolation methods. The active isolation system is often used to reduce the ground vibration near the source. It is usually installed either around the vibration source or at a close distance to the source. The passive isolation system, on the other hand, usually is far away from the source and surrounds the protected structure. Normally, there are two passive vibration isolation methods: the trench (open or infilled) isolation method and the pile (pile rows or sheet piles) isolation method. To date, many studies concerning vibration isolation using trenches or piles have been conducted. For example, Emad and Manolis [1] utilized the boundary element method (BEM) with constant elements to examine the efficiency of vibration reduction by open trench with a rectangular or a circular cross-section. Considering the coupling effects between the soil skeleton and underground water, Cao et al. [2] proposed an analytical model to investigate the screening efficiency of trenches to moving-load induced ground vibrations based on Biot’s dynamic poroelastic theory. Cai et al. [3] investigated the vibration isolation effect of pile rows embedded in a poroelastic medium by using the wave function expansion method. Kattis et al. [4, 5] used 3D BEM to calculate the screening effectiveness of a pile row in the frequency domain. Also, by means of the frequency domain BEM, the screening effectiveness of four types of circular piles in a row against the vibration due to a massless square foundation subjected to a harmonic vertical loading is studied by Tsai et al. [6]. Besides, by means of the fictitious pile method developed by Muki and Sternberg [7] and the direct superposition method, Lu et al. [8, 9] analyzed the vibration isolation effect of pile rows. It is noticed that previous studies concern the vibration isolation modelling in a generalized standard
Active Vibration Isolation System Based on Artificial Neural Network  [PDF]
Ibrahim M. Rida
Journal of Applied Sciences , 2004,
Abstract: Effective isolation of high precision instruments from disturbances is commonly achieved via active vibration isolation systems (AVIS). However, there are a number of problems associated with the operation of AVIS. One such a problem is due to fluctuations of the AVIS plant characteristics. As a result, displacements of the object are observed, which makes the isolation incomplete. This work proposes an artificial neural network (ANN) based control system whereby training data for the ANN is obtained from an improved optimal algorithm for AVIS. The performance of the proposed ANN based control system is investigated and results are compared to those obtained from analytical models. The results show insensitivity of the proposed ANN to the variation in plant`s time constant. Furthermore, the ANN procedure accomplished excellent vibration isolation compared with previous work. This work also shows that the use of a neural network does not require sophisticated adaptive methods
NONLINEAR DAMPING FOR VIBRATION ISOLATION AND CONTROL USING SEMI ACTIVE METHODS  [PDF]
Uchenna .H. Diala,Gloria .N. Ezeh
Academic Research International , 2012,
Abstract: This paper describes the semi active control of a single as well as two degree-of-freedom (sdof and 2dof) system with a magnetorheological (MR) damper. The investigation was done using a MATLAB/SIMULINK model. The objective of this paper is to present a comprehensive analysisof a SIMULINK model for a control strategy (using a Proportional-Integral Controller) to study the effect of a cubic viscous damping characteristic parameter on the transmissibility of sdof and 2dof vibration isolation systems. This research has substantial deductions for the analysis and design of viscously damped vibration isolators for a broad scope of engineering applications.
Vibration Isolation Design for the Micro-X Rocket Payload  [PDF]
Sarah N. T. Heine,Enectali Figueroa-Feliciano,John M. Rutherford,Patrick Wikus,Phil Oakley,Frederick S. Porter,Dan McCammon
Physics , 2013, DOI: 10.1007/s10909-013-1032-1
Abstract: Micro-X is a NASA-funded, sounding rocket-borne X-ray imaging spectrometer that will allow high precision measurements of velocity structure, ionization state and elemental composition of extended astrophysical systems. One of the biggest challenges in payload design is to maintain the temperature of the detectors during launch. There are several vibration damping stages to prevent energy transmission from the rocket skin to the detector stage, which causes heating during launch. Each stage should be more rigid than the outer stages to achieve vibrational isolation. We describe a major design effort to tune the resonance frequencies of these vibration isolation stages to reduce heating problems prior to the projected launch in the summer of 2014.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.