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Numerical Investigation of Geometrical Influence On Isolator Performance  [PDF]
Sridhar T,Chandrabose G,Thanigaiarasu S
International Journal on Theoretical and Applied Research in Mechanical Engineering , 2013,
Abstract: The three dimensional Reynolds Averaged Navier Stokes (RANS) Computational Fluid Dynamics analysis has been employed to study the influence of geometrical shape transition on performance of scramjet isolators. The pre-combustion shock train also called pseudo shock which appears in the subsonic combustion mode in dual mode scramjet isolator is analyzed in shape transitioned isolators. A square isolator and a shape transitioned square to circular isolator configurations having same length and cross sectional areas were considered. The simulations were carried on isolator geometries for inlet conditions of Mach 2 and unit Reynolds number of 12.4x106/m. The pressure rise due to heat addition in combustion chamber is modeled with back pressure 3.8 times higher than the inlet static pressure. The Numerical results match with the experimental data obtained from literature and with the waltrup and Billig correlation. The length of pseudo shock is compared in these isolators and it is found that it is shorter for square to circular configuration.
Identification of parameters for metal rubber isolator with hysteretic nonlinearity characteristics

Yan Hui,Jing Hong-Yuan,Liu Wen-Jian,AMUlannov,

物理学报 , 2009,
Abstract: The nonlinear dynamic characteristics of metal rubber isolator are studied and a dynamic model with parameters with physical meaning is developed in this paper. According to the experimental results from a setup with single degree of freedom, the identification method for related parameters is researched. The nonlinear function that describes the dynamic behavior of the system is converted to the series of linear functions by using energy method and least square method. The identification results show good agreement with the experimental results and explain the effect of parameters on the performance of isolators.
Experimental study on mechanical characteristics of the subway-using steel spring vibration isolator

HE Qinglie
, ZHU Shengyang, CAI Chengbiao, ZHANG Jiawei

- , 2016,
Abstract: 钢弹簧隔振器刚度与阻尼是影响浮置板轨道结构减振性能的重要参数。为明确钢弹簧隔振器力学特性,采用电液伺服式疲劳试验机对钢弹簧隔振器进行试验研究,分析加载频率、载荷幅值以及疲劳载荷次数对钢弹簧隔振器动刚度和损耗因子的影响。试验表明:当加载幅值不变时,隔振器动刚度和损耗因子随加载频率增加而增加;当加载频率不变时,隔振器动刚度及损耗因子随载荷幅值的增大而减小;随着疲劳加载次数的增加,隔振器动刚度和损耗因子逐渐减少;载荷幅值、加载频率以及疲劳加载次数对钢弹簧隔振器的动刚度和损耗因子的影响规律均可拟合为一个多项式关系。
Stiffness and damping of steel spring vibration isolator are important parameters which have significant influence on vibration damping performance of floating slab track structure. In order to clarify the mechanical characteristic of steel spring vibration isolator, the experimental study was conducted by using electro-hydraulic servo fatigue machine in this paper. The influence of loading frequency, the load amplitudes and accumulated times of fatigue loading on the stiffness of steel spring vibration isolator and damping factor were studied. The results show as follows: When the load amplitude is constant, the dynamic stiffness and the damping factor increase with increasing of loading frequency. When the loading frequency is constant, the dynamic stiffness and damping factor of vibration isolator decrease with increasing of load amplitudes. The dynamic stiffness and the damping factor decreases gradually with increasing the number of fatigue loading. The influence of loading frequency, load amplitudes and the accumulated times of fatigue loading on the characteristics of steel spring vibration isolator parameters can be fitted into a polynomial relationship, respectively
A Numerical Study on the Performance of Nonlinear Models of a Microvibration Isolator  [PDF]
Jie Wang,Shougen Zhao,Dafang Wu
Shock and Vibration , 2014, DOI: 10.1155/2014/531013
Abstract: A non-Newton fluid microvibration isolator is studied in this paper and several nonlinear models are firstly presented to characterize its vibration behaviors due to the complicated effects of internal structure, external excitation, and fluid property. On the basis of testing hysteretic loops, the generalized pattern search (GPS) algorithm of MATLAB optimization toolbox is used to identify the model parameters. With the use of the fourth-order Runge-Kutta method, the performance of these nonlinear models is further estimated. The results show that, in the cases of force excitation (FE), the generalized nonlinear model (GNM) and the complicated model (CM) can properly characterize the physical vibration in the frequency band of 5–20?Hz. However, in the frequency band of 30–200?Hz, the Maxwell model shows more excellent performance. After the application of orthogonal testing method, several important factors, for example, damping coefficient and flow index, are obtained; then a parametric analysis is carried out with the purpose of further studying the influences of nonlinear model parameters. It can be seen that only the GNM and CM can consider the above nonlinear effects in both the FE cases and the foundation displacement excitation (FDE) cases, but the CM is not convenient to use in practice. 1. Introduction In recent years, the international space technology has made a rapid development, which means that the categories, functions, and structural format of spacecraft are becoming increasingly various and complex [1]. In particular, the high resolution remote sensing satellites are one of the research hotspots of high precision spacecraft; for example, the American KH-13 surveillance satellite achieves an observational resolution of 0.05 meter, and the commercial remote sensing satellite GeoEye-1 launched in September 2008 acquires a resolution of 0.41 meter [2]. Due to the effects of bearing disturbance, static and dynamic imbalance of momentum/reaction wheels, the high frequency jitter may propagate to spacecraft body structure and then to optical payload; thus the image quality and the resolution performance will probably be affected seriously [3]. In order to satisfy the strict line-of-sight performance and stability requirements of high precision spacecraft, the amplitude of vibration should be reduced to the order of micrometers or even nanometers [4], and a commonly used method to solve this dilemma is inserting oil microvibration isolators between the jitter source and spacecraft or/and between the optical payload and spacecraft [5]. Since a
Excellent Performance of Earth Dams under Resonance Motion Using Isolator Damping Layer  [PDF]
Behrouz Gordan,Azlan Adnan
Shock and Vibration , 2014, DOI: 10.1155/2014/432760
Abstract: The effect of blanket layer using isolator damping layer (IDL) between river sand foundation and short embankment to remove damage under severe earthquake was investigated in the present study. In case of numerical analysis by ANSYS program, dominant frequency (DF) was computed by free vibration analysis. Soil mechanic tests for thirteen samples to design IDL formula were carried out. In terms of critical condition for earthquake effect such as resonance, five physical small models were tested using vibrator table under the dominant frequency with scale parameter 1/100. As a result, dam was significantly damaged without blanket layer IDL. In order to reduce damage, the best performance was observed using blanket layer (IDL) when this layer was expanded below the reservoir region. The reinforced thickness layer size is one-fourth of dam height. This method is a novel suggestion for earth dam design in seismic zone. 1. Introduction The dynamic assessment dramatically has been started in earth dams after the observation of some damages during the earthquake. In this domain, huge damage such as body cracks was recorded. Totally, this knowledge is correspondent to control dam behavior to avoid of failure process. Besides, earth dam construction is possible with respect to compaction process. Therefore, the consolidation settlement can be completely maximized at the end of construction. In terms of earthquake effect on dam response, the first phase of total settlement is related to the final displacement in the static state. Therefore, total settlement is the superposition of static and dynamic effect. According to literature review in this study, a few cases of data monitoring was just recorded [1–3]. Two cases such as the lack of data monitoring and technological development to provide computing program led to use of numeric method for dynamic analyzing. In the other words, the numerical analysis was commonly utilized in several studies to predict dynamic behavior during the earthquake [4–9]. In terms of analysis technique, two methods such as finite-element method (FEM) and finite-difference method (FDM) can be applied. Dynamic analysis of earth dam was carried out by using two techniques such as two-dimensional and three-dimensional [10–13]. To select, plane strain (2D) and plane stress (3D) depends on dam configuration and valley shape in order to distribute lateral strain [14]. In terms of reinforcement methods, some methods have been used to reinforce dam in order to improve dynamic behavior along the earthquake [15–19]. To verify results based on
Study on Optimal Placement of Piezoelectric Actuators for a Whole Spacecraft Vibration Isolator
Liu Fang,Fang Bo,Huang Wen-Hu
Research Journal of Applied Sciences, Engineering and Technology , 2012,
Abstract: Position of actuators plays an important role in active vibration control, which affects not only the performance of vibration control but also the stability of the whole system, especially for flexible structures. In this paper, dynamic sensitivity analysis method was used to derive an optimization criterion for Piezoelectric Stack Actuator (PSA), this criterion was only related to the dynamic characteristics of the structure itself and the features of disturbances, but was not affected by initial conditions and control methods. Then by using this criterion, optimal placement of the piezoelectric actuator of a Whole-Spacecraft Vibration Isolator (WSVI) was studied, and vibration control effect of random position and optimal position was compared; simulation results verified the validity of the criteria, and showed that the optimized location of actuator could greatly enhance the actuation efficiency and vibration control effect.
Characterization of an Electromagnetic Vibration Isolator  [PDF]
Naibiao Zhou, Kefu Liu
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2011, DOI: 10.4236/jemaa.2011.312079
Abstract: A novel vibration isolator is constructed by connecting a mechanical spring in parallel with a magnetic spring in order to achieve the property of high-static-low-dynamic stiffness (HSLDS). The HSLDS property of the isolator can be tuned off-line or on-line. This study focuses on the characterization of the isolator using a finite element based package. Firstly using the single physics solver, the stiffness behaviours of the mechanical and magnetic springs are determined, respectively. Then using the weakly coupled multi-physics method, the stiffness behaviours of the passive isolator and the semi-active isolator are investigated, respectively. With the found stiffness models, a nonlinear differential equation governing the dynamics of the isolator is solved using the time-dependent solver. The displacement transmissibility ratios of the isolator are obtained. The study confirms that the isolation region of the isolator can be widened through off-line or on-line tuning.
Performance Analysis of the Cooperate Seismic System of the InfillWall and Vibration Isolator Based on Finite Element Analysis (FEA)

- , 2018, DOI: 10.3969/j.issn.1000-0844.2018.05.891
Abstract: 隔震器与填充墙对建筑抗震性能有很大作用。为了探究填充墙布置形式及填充材料和隔震器协同作用对钢筋混凝土框架结构动力特性及抗震性能的影响,采用等效斜撑理论,对3种不同填充墙布置形式与隔震器协同作用的抗震系统方案进行对比分析,研究发现顶层不布置填充墙与隔震器协同抗震系统钢筋混凝土框架结构的抗震性能最佳。在此系统上分析了不同填充材料对钢筋混凝土框架结构抗震性能的影响,结果表明,加气混凝土砌块填充墙的钢筋混凝土框架结构抗震性能最好。
Vibration isolators and infill walls have great effects on the seismic performance of buildings. In order to explore the influence of the infill wall layout and material on the dynamic characteristics and seismic performance of the reinforced concrete (RC) frame structures, an equivalent model based on the equivalent brace theory was adopted to compare and analyze three anti-seismic system schemes of differing filled-wall arrangements with the cooperative work of a vibration isolator. It was found that the seismic performance of the RC frame structure is best with no infill wall on the top floor. On this basis, the effect of different filling materials on the seismic performance of RC frame structure was analyzed. The results showed that the seismic performance of the RC frame with aerated concrete block filled wall is best.
Dynamic Analysis of Quasi-Zero-Stiffness Vibration Isolator Considering Load Variation

- , 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.
Broadband Faraday Isolator  [PDF]
Michal Berent,Andon A. Rangelov,Nikolay V. Vitanov
Physics , 2012, DOI: 10.1364/JOSAA.30.000149
Abstract: Driving on an analogy with the technique of composite pulses in quantum physics, we propose a broadband Faraday rotator and thus a broadband optical isolator, which is composed of sequences of ordinary Faraday rotators and achromatic quarter-wave plates rotated at the predetermined angles.
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