• Title/Summary/Keyword: Damped vibration system

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Finite Element Vibration/Shock Analysis of Double Stage Elastic Mounting System with Viscoelastically Damped Foundation Structure (유한용소법을 이용한 점탄성 감쇠구조물이 포함된 2단 탄성마운트 시스템의 진동/충격응답 해석)

  • 정우진;류정수;배수룡;함일배
    • Journal of KSNVE
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    • v.10 no.3
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    • pp.508-516
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    • 2000
  • To study the possibility of F.E.M application to vibration and shock response of double stage elastic mounting system with complicated damped foundation structure like common-bed or raft in ships foundation structure model which has complicated damped sandwich cross-section is analyzed first. And then vibration responses experimental results and shock response of double stage elastic mounting system with complicated damped foundation structure like common-bed or raft in ships foundation structure model which adopts the above damped structure as intermediate foundation were compared. As a result it is found that F.E.M could be effectively used in analyzing the vibration and shock response of double and multi-stage elastic mounting system with complicated damped foundation structures.

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A Study on the Effects of Dual Dynamic Vibration Absorber for Damped Vibration System (감쇠진동계에 부착된 복합동흡진기의 효과에 관한 연구)

  • 안찬우;최석창;김동영
    • Journal of KSNVE
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    • v.7 no.6
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    • pp.1039-1048
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    • 1997
  • This paper describes the effects of dual dynamic vibration absorbers attached to a primary vibration system with damping. The efficiency of dual dynamic vibration absorbers was investigated with the height of amplitude ratio at the resonance frequency ratio of the damped vibration system according to mass ratio, natural frequency ratio and damping ratio. The variation of amplitude ratio related to frequency ratio of primary vibration system is verified experimentally and theoretically according to dual dynamic vibration systems using computer program designed to find mutual relationship between two absorbers.

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Optimum LCVA for suppressing harmonic vibration of damped structures

  • Shum, K.M.;Xu, Y.L.;Leung, H.Y.
    • Smart Structures and Systems
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    • v.20 no.4
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    • pp.461-472
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    • 2017
  • Explicit design formulae of liquid column vibration absorber (LCVA) for suppressing harmonic vibration of structures with small inherent structural damping are developed in this study. The developed design formulae are also applicable to the design of a tuned mass damper (TMD) and a tuned liquid column damper (TLCD) for damped structures under harmonic force excitation. The optimum parameters of LCVA for suppressing harmonic vibration of undamped structures are first derived. Numerical searching of the optimum parameters of tuned vibration absorber system for suppressing harmonic vibration of damped structure is conducted. Explicit formulae for these optimum parameters are then obtained by a series of curve fitting techniques. The analytical result shows that the control performance of TLCD for reducing harmonic vibration of undamped structure is always better than that of non-uniform LCVA for same mass and length ratios. As for the effects of structural damping on the optimum parameters, it is found that the optimum tuning ratio decreases and the optimum damping ratio increases as the structural damping is increased. Furthermore, the optimum head loss coefficient is inversely proportional to the amplitude of excitation force and increases as the structural damping is increased. Numerical verification of the developed explicit design expressions is also conducted and the developed expressions are demonstrated to be reasonably accurate for design purposes.

A Study on Optimal Multi-dynamic Absorber of Damped Linear Vibration System under the Harmonic Motion of the Base (기반의 조화운동을 받는 감쇠선형진동계의 최적 복합동흡진기에 관한 연구)

  • 안찬우;김동영;홍도관
    • Journal of KSNVE
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    • v.10 no.2
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    • pp.325-330
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    • 2000
  • A dynamic absorber is used to protect the primary vibration system under the steady-state harmonic disturbance. In a number of cases it appears expedient to install several absorbers of smaller masses instead of one. This may be due to the need of distribute the absorber's response along the construction, restrictions on the absorber's installation. So, we studied characteristics of the primary vibration system for the optimal natural frequency ratio and the optimal damping ratio of serial multi-dynamic absorber. Also we obtained the optimum values of the serial multi-dynamic absorber parameters using computer simulation for the damped primary vibration system. In designing multi-dynamic absorber, we presented for the optimal natural frequency and the optimal damping ratio of multi-dynamic absorbers.

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Dynamic Vibration Absorber Having Coil Springs and Oil Damper for a Damped Vibration System (감쇠진동계에 부착된 코일스프링과 오일댐퍼로 구성된 동흡진기)

  • Ahn, C.W.;Park, S.C.;Lee, H.B.
    • Journal of the Korean Society for Precision Engineering
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    • v.13 no.12
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    • pp.129-135
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    • 1996
  • This paper presents the effectiveness of the dynamic vibration absorber consisting of a single mass, coil springs and oil damper on the resonance freauency ratio and amplitude ratio for damped linear systems, that is, primary vibration system with damping. The effects of the dynamic vibration absorber are investigated numerically and experimentally for values of mass ratio, natural frequency ratio, and damping ratio. The experimental results show good agreement with calculated ones. As a result, the characteristics shown by the present work are useful in optimal tuning the dynamic vibration absorber in practice.

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Modified Modal Methods for Sensitivity Analysis of Asymmetric Damped System (비대칭 감쇠 시스템의 민감도 해석을 위한 개선된 모드법)

  • Moon, Yeong-Jong;Jo, Ji-Seong;Oh, Ju-Won;Lee, In-Won
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.11a
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    • pp.530-533
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    • 2004
  • It is well known that many real systems have asymmetric mass, damping and stiffness matrices. In this case, the method for calculating eigenpair sensitivity is different from that of symmetric system. To determine the derivatives of the eigenpairs in asymmetric damped case, a modal method was recently developed by Adhikari. When a dynamic system has many degrees of freedom, only a few lower modes are available, and because the higher modes should be truncated to use the modal method, the errors may become significant. In this paper a procedure for determining the sensitivities of the eigenpairs of asymmetric damped system using a few lowest set of modes is proposed. Numerical examples show that proposed method achieves better calculating efficiency and highly accurate results when a few modes are used.

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Vibration Control Performance Evaluation of Semi-active Outrigger Damper System (준능동 아웃리거 댐퍼시스템의 진동제어 성능평가)

  • Kim, Hyun-Su;Kang, Joo-Won
    • Journal of Korean Association for Spatial Structures
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    • v.15 no.4
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    • pp.81-89
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    • 2015
  • Damped outrigger systems have been proposed as a novel energy dissipation system to protect tall buildings from severe earthquakes and strong wind loads. In this study, semi-active damping devices such as magnetorheological (MR) dampers instead of passive dampers are installed vertically between the outrigger and perimeter columns to achieve large and adaptable energy dissipation. Control performance of semi-active outrigger damper system mainly depends on the control algorithm. Fuzzy logic control algorithm was used to generate command voltage sent to MR damper. Genetic algorithm was used to optimize the fuzzy logic controller. An artificial earthquake load was generated for numerical simulation. A simplified numerical model of damped outrigger system was developed. Based on numerical analyses, it has been shown that the semi-active damped outrigger system can effectively reduce both displacement and acceleration responses of the tall building in comparison with a passive outrigger damper system.

INFINITELY MANY HOMOCLINIC SOLUTIONS FOR DAMPED VIBRATION SYSTEMS WITH LOCALLY DEFINED POTENTIALS

  • Selmi, Wafa;Timoumi, Mohsen
    • Communications of the Korean Mathematical Society
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    • v.37 no.3
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    • pp.693-703
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    • 2022
  • In this paper, we are concerned with the existence of infinitely many fast homoclinic solutions for the following damped vibration system $$(1){\hspace{32}}{\ddot{u}}(t)+q(t){\dot{u}}(t)-L(t)u(t)+{\nabla}W(t,u(t))=0,\;{\forall}t{\in}{\mathbb{R}},$$ where q ∈ C(ℝ, ℝ), L ∈ C(ℝ, ${\mathbb{R}}^{N^2}$) is a symmetric and positive definite matix-valued function and W ∈ C1(ℝ×ℝN, ℝ). The novelty of this paper is that, assuming that L is bounded from below unnecessarily coercive at infinity, and W is only locally defined near the origin with respect to the second variable, we show that (1) possesses infinitely many homoclinic solutions via a variant symmetric mountain pass theorem.

Estimation of viscous and Coulomb damping from free-vibration data by a least-squares curve-fitting analysis

  • Slemp, Wesley C.H.;Hallauer, William L. Jr.;Kapania, Rakesh K.
    • Smart Structures and Systems
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    • v.4 no.3
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    • pp.279-290
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    • 2008
  • The modeling and parameter estimation of a damped one-degree-of-freedom mass-spring system is examined. This paper presents a method for estimating the system parameters (damping coefficients and natural frequency) from measured free-vibration motion of a system that is modeled to include both subcritical viscous damping and kinetic Coulomb friction. The method applies a commercially available least-squares curve-fitting software function to fit the known solution of the equations of motion to the measured response. The method was tested through numerical simulation, and it was applied to experimental data collected from a laboratory mass-spring apparatus. The mass of this apparatus translates on linear bearings, which are the primary source of light inherent damping. Results indicate that the curve-fitting method is effective and accurate for both perfect and noisy measurements from a lightly damped mass-spring system.