scholarly journals Analysis and design of the power law damping based on the nonlinear vessel isolation system

2018 ◽  
Vol 10 (12) ◽  
pp. 168781401881719 ◽  
Author(s):  
You Wang ◽  
Xinghua Zhu ◽  
Rong Zheng ◽  
Zhe Tang ◽  
Bingbing Chen
Keyword(s):  
Resonant Frequency ◽  
Working Conditions ◽  
Power Law ◽  
Nonlinear Damping ◽  
Frequency Region ◽  
Isolation System ◽  
Analysis And Design ◽  
Force Transmissibility ◽  
Isolation Systems ◽  
Isolation Performance

In this study, the applications of the cubic power law damping in vessel isolation systems are investigated. The isolation performance is assessed using the force transmissibility of the vessel isolation system, which is simplified as a multiple-degree-of-freedom system with two parallel freedoms. The force transmissibilities of different working conditions faced in practice are discussed by applying the cubic power law damping on different positions of the vessel isolation system. Numerical results indicate that by adding the cubic power law damping to an appropriate position, the isolation system can not only suppress the force transmissibility over the resonant frequency region but also keep the force transmissibility unaffected at the nonresonant frequency region. Moreover, the design of the nonlinear vessel isolation system is discussed by finding the optimal nonlinear damping of the isolation system.

Beneficial performance of a quasi-zero stiffness vibration isolator with generalized geometric nonlinear damping

2020 ◽  
pp. 095745652097238
Author(s):  
Chun Cheng ◽  
Ran Ma ◽  
Yan Hu
Keyword(s):  
Damping Ratio ◽  
Nonlinear Damping ◽  
Vibration Isolator ◽  
Equivalent Damping ◽  
Frequency Responses ◽  
Geometric Nonlinear ◽  
Resonant Region ◽  
Force Transmissibility ◽  
Isolation Performance ◽  
Force And Displacement Transmissibility

Generalized geometric nonlinear damping based on the viscous damper with a non-negative velocity exponent is proposed to improve the isolation performance of a quasi-zero stiffness (QZS) vibration isolator in this paper. Firstly, the generalized geometric nonlinear damping characteristic is derived. Then, the amplitude-frequency responses of the QZS vibration isolator under force and base excitations are obtained, respectively, using the averaging method. Parametric analysis of the force and displacement transmissibility is conducted subsequently. At last, two phenomena are explained from the viewpoint of the equivalent damping ratio. The results show that decreasing the velocity exponent of the horizontal damper is beneficial to reduce the force transmissibility in the resonant region. For the case of base excitation, it is beneficial to select a smaller velocity exponent only when the nonlinear damping ratio is relatively large.

On the behavior and force transmissibility of a cable network isolator

2019 ◽  
Vol 25 (8) ◽  
pp. 1492-1504
Author(s):  
Yanhao Chen ◽  
Zhiyi Zhang
Keyword(s):  
Synthesis Methods ◽  
Isolation System ◽  
Cable Network ◽  
Modal Properties ◽  
Cable Networks ◽  
Vibration Transmissibility ◽  
New Type ◽  
Force Transmissibility ◽  
Isolation Performance ◽  
Important System

The cable network is being paid increased attention and has found application in practice as a new type of vibration isolator. Modal properties and isolation performance are important considerations for the widespread use of network isolators. In contrast with previous experiments on structural synthesis methods, this paper presents an analytical method to obtain the characteristic equation of a network structure. This method is extended to investigate the modal properties, forced vibration and vibration transmissibility of a network isolation system. In addition, the validity of these analytical modal solutions is verified by an independent finite element method. Modal properties and forced vibrations of cable networks with different configurations are examined. The important system parameters are identified and their effect on the system behavior is discussed.

Force transmissibility of floating raft systems with quasi-zero-stiffness isolators

2017 ◽  
Vol 24 (16) ◽  
pp. 3608-3616 ◽  
Author(s):  
Li Yingli ◽  
Xu Daolin
Keyword(s):  
Vibration Isolation ◽  
Damping Ratio ◽  
Low Frequency ◽  
Frequency Region ◽  
Mass Ratio ◽  
Isolation System ◽  
Floating Raft ◽  
Highly Nonlinear ◽  
Vibration Attenuation ◽  
Force Transmissibility

In view of the excellent performance of a single quasi-zero-stiffness (QZS) device in vibration attenuation, this paper presents a study on a vibration isolation floating raft system constructed with a double-layer QZS mechanism. A QZS device is a typical nonlinear isolator, hence the floating raft system is a coupled highly nonlinear isolation system. To understand the behaviors and its performance in vibration attenuation, an analytical approach is developed to describe the characteristics including the mathematical relationship between amplitude–frequency, force transmissibility, and the effects of the mass ratio and damping ratios on attenuation performance. The outcomes show that the two-degree-of-freedom QZS–QZS system is superior for vibration isolation when compared to the traditional linear system and the two other types of QZS systems. The effective vibration isolation frequency region of the QZS–QZS system is expanded to the low-frequency region by 72%. The QZS system is sensitive to the damping ratio, which decreases the resonance peak significantly. The mass ratio is a crucial design parameter in low-frequency vibration isolation design.

Sliding-Mode Control Algorithm for a Hard-Mounted Isolation System

2007 ◽  
Author(s):  
Yung-Peng Wang ◽  
Jen-Chieh Tsao
Keyword(s):  
Sliding Mode Control ◽  
Control Algorithm ◽  
Sliding Mode ◽  
Isolation System ◽  
Mode Control ◽  
Active Isolation ◽  
Ultra Precision ◽  
Passive Isolation ◽  
Isolation Systems ◽  
Isolation Performance

It is well known that the trend of current technology development is microscopic and ultra-precision, especially in the areas of semiconductor manufacturing, ultra-precision machining, MEMS, microbiology and nanotechnology. Hence, vibration becomes a significant problem in those fields. There are two types of vibration control techniques. One is passive isolation system; the other is active isolation system. Passive isolation system can provide better performance for higher frequencies. Active isolation system is used to improve the isolation performance for lower frequencies. However, passive isolation system has bad performance around the natural frequency. In addition, it cannot eliminate the effects of onboard disturbances. Therefore, active isolation system becomes the major technology in the applications of microvibration control for precision equipment. In practice, all active isolation systems are based upon a hybrid concept, combining a passive isolator for higher frequencies and a servo control system for lower frequencies. This combination allows for two significantly different configurations, which can be categorized as: soft-mounted isolation systems and hard-mounted isolation systems. The soft-mounted systems are inherently insensitive to resonance in the main structure below the isolators. Yet, they are sensitive to resonances in the isolated platform. The hard-mounted systems are extremely stiff and allows for large onboard disturbance forces without excessive motion. However, the major drawback with a hard-mounted system is that vibration isolation performance suffers from the passive-active compromise and is unable to come up to the optimal performance. In this paper, a sliding-mode control algorithm is developed for a hard-mounted isolation system with a piezoactuator. Based on the bounds of environmental vibrations and onboard disturbances, the sliding-mode control algorithm can make the hard-mounted isolation system achieve the optimal and robust performance of low vibration transmissibility and high stiffness. The results are verified by the numerical simulations.

Maxwell–Voigt and Maxwell Ladder Models for Multi-Degree-of-Freedom Elastomeric Isolation Systems

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Sudhir Kaul
Keyword(s):  
Degree Of Freedom ◽  
Isolation System ◽  
Practical Applications ◽  
Geometrical Properties ◽  
Analysis And Design ◽  
Proposed Model ◽  
Elastomeric Isolator ◽  
Isolation Systems ◽  
Three Degree Of Freedom ◽  
Ladder Models

This paper presents a model for an elastomeric isolation system consisting of a three degree-of-freedom (DOF) rigid body assembled to a frame through multiple isolators. Each elastomeric isolator is either represented by a Maxwell–Voigt (MV) model consisting of two Maxwell elements or by a Maxwell ladder (ML) model consisting of three Maxwell elements. The MV models and the ML models are characterized by using experimental data that are collected at multiple excitation frequencies. The characterized models are evaluated and used to simulate the performance of the isolation system. The models developed in this paper are capable of representing frequency-dependent behavior that is exhibited by elastomeric isolators and the overall isolation system. Furthermore, the proposed model is capable of directly associating the behavior of the isolation system with physical and geometrical properties of each isolator. The proposed model is expected to be a useful tool for the analysis and design optimization of elastomeric isolation systems. Most of the isolation systems in practical applications exhibit multiple DOF, this model will be particularly useful in such applications since it does not constrain motion to translation only. This is a shortcoming of the models in the current literature that the proposed model attempts to overcome.

Resonance Characteristics of Unidirectional Viscous and Coulomb-Damped Vibration Isolation Systems

1967 ◽  
Vol 89 (4) ◽  
pp. 729-740 ◽  
Author(s):  
Jerome E. Ruzicka
Keyword(s):  
Resonant Frequency ◽  
Vibration Isolation ◽  
Elementary Theory ◽  
Rate Of Change ◽  
Design Data ◽  
Isolation System ◽  
Extensive Evaluation ◽  
Wide Range ◽  
Isolation Systems ◽  
Damped Systems

Elementary vibration theory based on transfer response analyses of single-degree-of-freedom systems indicates that an increase in isolation system damping causes a decrease in resonant transmissibility. This theory further specifies that, for viscous-damped systems, an increase in damping decreases the resonant frequency whereas, for Coulomb-damped systems, an increase in damping increases the resonant frequency. It is frequently found in practice that an increase in damping may increase the resonant transmissibility and cause a change in resonant frequency opposite to that predicted by elementary theory. This paper presents a more extensive evaluation of the resonance characteristics of unidirectional vibration isolation systems, including the effects of directly coupled and elastically coupled damping elements. Mathematical models and absolute transmissibility characteristics of viscous and Coulomb-damped vibration isolation systems are discussed and resonance characteristics are analyzed in terms of the resonant frequency ratio, the resonant transmissibility, and the rate of change of these parameters with damping. Design data are presented graphically for parametric variations of stiffness and damping which are sufficiently broad to encompass a wide range of practical engineering problems.

Tuned Damping of an Air-Mounted Isolation System

2004 ◽  
Author(s):  
Reza Kashani ◽  
Kazim Mirza
Keyword(s):  
Resonant Frequency ◽  
High Frequency ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Isolation System ◽  
And Mathematics ◽  
High Level ◽  
Three Degree Of Freedom ◽  
Tuned Damper ◽  
Isolation Performance

Air mounts can provide the highest degree of isolation of any type vibration isolator. Soft-mounting, and thus high level of low-frequency isolation, with system natural frequency as low as 1 Hz can be achieved. Due to their construction, air mounts have negligible damping. Although, this almost undamped nature of air mounts enhances the high-frequency isolation, provisions should be made to address the lack of isolation resulting in excessive body displacements around the resonant frequencies, especially when the system is exposed to shock inputs. While the addition of viscous damping to the air mount is proposed in the literature but it is not recommended in most applications. This is because it deteriorates the mount’s high-frequency isolation performance. Instead, it would be highly desirable to add tuned damping to the mounted system at its resonant frequency (ies). The challenge in doing so, is realizing a damper tunable to a very low frequency and yet not be prohibitively large. A novel tuned damping mechanism is proposed in this paper. It adds damping to an air mount only at the resonant frequency (ies), via a bi-fluid Helmholtz resonator. In an illustrative example the mechanics and mathematics (modeling) of a one and three degree of freedom air mounted systems equipped with a tuned damper, as well as the tuning of such damper are discussed. The example also demonstrates the effectiveness of the air mount with the tuned damper.

Study on Characteristics and Effects of Seismic Isolation System of Vertically Utilized Coiled Springs

2007 ◽  
Author(s):  
Tsuyoshi Fukasawa ◽  
Akihiro Kinoshita ◽  
Satoshi Fujita
Keyword(s):  
Analytical Model ◽  
Seismic Isolation ◽  
304 Stainless Steel ◽  
Restoring Force ◽  
Isolation System ◽  
Static Tests ◽  
Coiled Spring ◽  
Isolation Systems ◽  
Seismic Isolation Systems ◽  
Isolation Performance

In recent years many structures employing seismic isolation systems have been constructed in Japan, the practical concern on the cost of seismic isolation systems has heightened. This paper describes the research and development of a new seismic isolation system using vertically utilized elastic and elasto-plastic coiled spring, and discusses analytical model for coiled spring. The basic concept of the earthquake isolation system that was constituted of bearing, restoration and damping elements is to realize cost effective design without any reduction in isolation performance. The restoration and damping elements of the isolation system were constituted by two types of coiled springs. The horizontal static tests were performed to evaluate the restoring characteristic and the mechanical model of elastic and elasto-plastic coiled spring. The restoration element of elastic coiled springs was made of using the two types of materials JIS SUP9 steel and JIS SUS 304 stainless steel. The elasto-plastic coiled springs of damping element also was made of using the two types of JIS SS 400 steel and JIS SWRM 17 steel. The characteristics of these coiled springs such as transverse stiffness and hysteretic damping and the validity of the analytical model were clarified through the static tests. Furthermore the response analyses based on the restoring force characteristics of experimental results were carried out to assess the isolation performance of this system.

Motion Analysis of Pendulum Type Isolation Systems During Earthquakes (Probabilistic Study of Isolation Performance of Base Isolated Structure Considering Characteristic Dispersion of Pendulum Type Isolation Systems)

2006 ◽  
Vol 129 (3) ◽  
pp. 507-515 ◽  
Author(s):  
Shigeki Okamura ◽  
Satoshi Fujita
Keyword(s):  
Linear Motion ◽  
Isolation System ◽  
Industrial Facilities ◽  
Probabilistic Study ◽  
Isolation Systems ◽  
Rubber Bearings ◽  
Friction Pendulum ◽  
Structural Engineers ◽  
Isolation Performance

Most of the base isolated buildings or structures are built on laminated rubber bearings in order to give them certain natural periods. This situation, however, also encourages structural engineers to research and develop nonrubber-type isolation systems such as linear motion bearing isolators and friction pendulum systems. It is considered that the nonrubber-type isolation systems can be applied to important industrial facilities, such as LNG tanks, boiler facilities, and so on, to refine their seismic reliabilities. This device of a nonrubber-type isolation system uses the energy loss associated with sliding to reduce the deleterious effects of earthquakes. However, when using nonrubber-type isolation systems with sliding in the atmosphere, long term durability of the systems must be taken into account. It may be difficult to maintain the friction coefficient of the system. In this paper, a stochastic study of the effect on rotational motion and isolation performance of two structures subjected to an earthquake with a friction pendulum bearing is analyzed with a Monte Carlo method.

The Effect of Stiffness and Loading Deviations in a Nonlinear Isolator Having Quasi Zero Stiffness and Geometrically Nonlinear Damping

2017 ◽  
Author(s):  
Ata Donmez ◽  
Ender Cigeroglu ◽  
Gokhan O. Ozgen
Keyword(s):  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Nonlinear Differential Equations ◽  
Harmonic Balance Method ◽  
Nonlinear Damping ◽  
Geometrically Nonlinear ◽  
Algebraic Equations ◽  
Isolation System ◽  
Highly Nonlinear ◽  
Isolation Performance

Static deflections due to static loadings limit the isolation performance of linear vibration isolation systems. Therefore, quasi-zero stiffness (QZS) mechanisms, i.e. nonlinear isolators with high static and low dynamic stiffness characteristic, are used to decrease the natural frequency of the isolation structure and improve the isolation performance of the system while having the same loading capacity. However, the resulting system is highly nonlinear and unstable solutions may as well occur. Although increasing the amount of linear viscous damping in the system reduces the nonlinearity, it has adverse effect on the isolation region. Geometrically nonlinear damping is effective when the response of the isolation system increases; hence, isolation region is unaffected. Combination of position depended nonlinear damping and QZS mechanism eliminates highly input depended response of QZS mechanism. In this study, a single degree of freedom system with a nonlinear isolator having QZS mechanism and geometrically nonlinear damping is considered. The nonlinear differential equations of motion of the isolation system are converted into a set of nonlinear algebraic equations by using harmonic balance method, which are solved by using Newton’s method with arc-length continuation. Several case studies are performed and the effect of stiffness and loading deviations on the isolation performance is studied.

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