Tuned dynamic absorber using non-linear stiffness

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Tuned dynamic absorber using non-linear stiffness

 

Author: Wong, Wai-lun
Title: Tuned dynamic absorber using non-linear stiffness
Degree: M.Phil.
Year: 2004
Subject: Hong Kong Polytechnic University -- Dissertations
Structural dynamics
Shock (Mechanics)
Vibration
Sorbents
Department: Dept. of Civil and Structural Engineering
Pages: xi, 191 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1749067
URI: http://theses.lib.polyu.edu.hk/handle/200/2019
Abstract: Undesirable excessive vibration due to structural resonance can be effectively reduced by either a dynamic vibration absorber or applying direct damping technique. However, linear absorber and damping are found not effective for complex practical cases. The aims of this project are (i) to optimize the performance of a dynamic vibration absorber with non-linear stiffness using a curved plate and (ii) to improve the non-linear damping coefficient of a non-viscous type air damper. Finally, their ability and feasibility are analyzed and compared. To reveal the damping and energy dissipation performance of a non-linear curved plate vibration absorber, the dynamic behavior of a curved plate is studied analytically. Softening spring and chaotic regions are found from the analytical solutions. Dynamic behavior of a two-degree-of-freedom using the non-linear softening spring absorber is then obtained through analytical formulations and numerical simulations. The amplitudes of the peak at lower frequencies are reduced and thus the suppression band-width is widened with small auxiliary damping while the curved plate undergoes softening spring vibration. Different combinations of system parameters are analyzed by the numerical integration method and an optimal design is obtained. The damping performance of the non-viscous type plate-air-plate air damper with non-linear damping coefficient is studied empirically. For a large air gap and small holes, the non-linearity of the damping vanished. The damping performance is improved by reducing the air gap thickness and enlarging the holes. After comparing the controllability, tuning complexity, installment feasibility and setup difficulties, the non-linear dynamic vibration absorber is found to be the more suitable choice.

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