Theoretical study of the effects of nonlinear viscous damping on vibration isolation of sdof systems
ABSTRACT The present study is concerned with the theoretical analysis of the effects of nonlinear viscous damping on vibration isolation of single degree of freedom (sdof) systems. The concept of the output frequency response function (OFRF) recently proposed by the authors is applied to study how the transmissibility of a sdof vibration isolator depends on the parameter of a cubic viscous damping characteristic. The theoretical analysis reveals that the cubic nonlinear viscous damping can produce an ideal vibration isolation such that only the resonant region is modified by the damping and the non-resonant regions remain unaffected, regardless of the levels of damping applied to the system. Simulation study results demonstrate the validity and engineering significance of the analysis. This research work has significant implications for the analysis and design of viscously damped vibration isolators for a wide range of practical applications.
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ABSTRACT: Micro-vibration caused by disturbance sources onboard spacecraft can severely degrade the working environment of sensitive payloads. Some notable vibration control methods have been developed particularly for the suppression or isolation of micro-vibration over recent decades. Usually, passive isolation techniques are deployed in aerospace engineering. Active isolators, however, are often proposed to deal with the low frequency vibration that is common in spacecraft. Active/passive hybrid isolation has also been effectively used in some spacecraft structures for a number of years. In semi-active isolation systems, the inherent structural performance can be adjusted to deal with variation in the aerospace environment. This latter approach is potentially one of the most practical isolation techniques for micro-vibration isolation tasks. Some emerging advanced vibration isolation methods that exploit the benefits of nonlinearity have also been reported in the literature. This represents an interesting and highly promising approach for solving some challenging problems in the area. This paper serves as a state-of-the-art review of the vibration isolation theory and/or methods which were developed, mainly over the last decade, specifically for or potentially could be used for, micro-vibration control.Mechanical Systems and Signal Processing 05/2015; 56. DOI:10.1016/j.ymssp.2014.10.007 · 1.91 Impact Factor
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ABSTRACT: With its variable stiffness, capability to provide friction damping by itself, and space-based adaptive performance, the disc spring, by replacing the cylindrical helical spring extensively, has found wide application in fields like aerospace, metallurgy, architecture, machinery and so on. For the nonlinear combination disc-spring vibration isolator, the mathematical model is established in this study on the basis of classical disc spring theories. The simulation results of the combination vibration isolator under simple harmonic excitation and the effects of damping ratio and different types of load on the vibration isolator are explored in depth, the findings of which help to lay a solid foundation for parameterization and serialization of the nonlinear combination disc-spring vibration isolator.02/2011; 211-212:40-47. DOI:10.4028/www.scientific.net/AMR.211-212.40
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ABSTRACT: It is essential to establish a dynamic model to predict and evaluate the dynamic performance of a nonlinear dry friction mounting system during design procedure, when it is impossible to carry out the test of prototype. Unlike the conventional ideal dry friction model where the direction of dry friction force is always considered to be opposite to that of relative velocity, a new equivalent resistance model of dry friction force is proposed based on the bilinear hysteretic model by introducing a parameterg γ in this work. The equivalent resistance contains spring force and damping force, whose direction is not opposite to that of relative velocity. Then, a dynamic model of the block foundation with nonlinear dry friction mounting system is established. When the equivalent resistance is applied to the dynamic model, its dynamic responses are obtained under common practical forms of press loads: rectangular pulse, half-sine pulse, and triangular pulse. Compared to experimental results, the dynamic responses based on the equivalent resistance model are more consistent with the simulation results based on the ideal dry friction model and the validity of the equivalent resistance model for the bilinear hysteretic model in this work is verified. Furthermore, the effect of the pulse shape and pulse duration on the dynamic responses of the block foundation with nonlinear dry friction mounting system is investigated.Journal of Mechanical Science and Technology 07/2014; 28(7):2535-2548. DOI:10.1007/s12206-014-0611-7 · 0.70 Impact Factor