• Title/Summary/Keyword: Viscoelastic Damping

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Optimal Adherent Position of Viscoelastic Material for the Reduction of Sound Power Radiated from the Stiffened Plate (보강판의 방사소음저감을 위한 제진재의 최적 위치 선정)

  • Kim, Sa-Su;Jo, Dae-Seung;An, Ho-Il;Jeong, Sang-Min
    • Journal of Ocean Engineering and Technology
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    • v.12 no.2 s.28
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    • pp.22-32
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    • 1998
  • Many of steel structures having little internal damping consist of stiffened plates. In case that viscoelastic materials are adhered to the stiffened plates for the reduction of structure-borne noise, their effects are varied by the adhered position and dynamic characteristics of the structures as well as their material properties and adhered amount. In this paper, sound reduction effects of viscoelastic materials partially adhered to the different positions of a stiffened steel plate have been investigated by the measurement of vibratory velocity and sound intensity. The results show that optimal adherent positions of viscoelastic materials to reduce sound radiation power are the loop areas of modes.

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A Study on the improvement of damping and optimal design of beam flexure for the passive vibration isolator (수동형 음강성 저주파 제진기의 감쇠 성능 향상과 빔 유연체의 최적 설계에 관한 연구)

  • Lee, Gil-Yong;Chang, Hee-Doh;Park, Young-Ho;Park, In-Hwang;Han, Dong-Chul
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.189-195
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    • 2008
  • The vibration isolator system(VIS) which has very low natural frequency could be designed by applying an axial compressive force to the beam-column flexure(BCF). In this paper a new shape of the BCF is suggested. It has stepwise axially varying properties by viscoelastic damping layer. So it has internal structural damping by damping layer during deformation. First the analytic solution is obtained for the BCF. And its critical load, buckling mode, stiffness and stress distributions are investigated. Also the dynamic properties of the VIS consist of the damping layered BCF are studied. Finally the optimal design procedure of damping layered BCF for the VIS is suggested. The improved performance of suggested VIS is verified by some experiments.

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구속 감쇠 기법을 이용한 로터시스템 구조 감쇠 증대

  • Kim, Do-Hyung;Ko, Eun-Hee;Song, Keun-Woong;Kim, Seung-Ho
    • Aerospace Engineering and Technology
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    • v.4 no.1
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    • pp.9-17
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    • 2005
  • The aeroelastic stability enhancement of composite hingeless rotor system through the structural damping increase has been investigated. In order to increase structural damping of the rotor system, constrained layer damping (CLD) treatment is applied to the composite flexures. Modal analysis of composite flexures with attached viscoelastic and constraining layers are performed using MSC/NASTRAN, and the effectiveness of CLD treatments are validated through modal test. The composite flexures with CLD are applied to a hingeless rotor system. The rotor system is tested in hovering condition and it is shown that in-plane damping is increased by means of CLD treatments.

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A Study on Material Damping of the $0^0&90^0$ Laminated Composite Sandwich Cantilever Beam inserted with Viscoelastic layer (점탄성층을 삽입한 $0^0&90^0$ 섬유강화 복합재료의 감쇠계수에 대한 연구)

  • Yim, Jong-Hee;Seo, Yun-Jong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.11a
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    • pp.345-348
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    • 2004
  • In this paper it is to establish a comprehensive model for predicting damping in sandwich Laminated composites on the basis of strain energy method. In this model, the effect of transverse shear on the material damping has been considered with in-plane stresses. Results showed that the viscoelastic core thickness in the sandwich beam and the Length of a beam have a high impact on the material damping. The transverse shear appears to be highly influenced by the damping behavior in $0^0$ laminated sandwiched composites. However, it is Little influenced by that in $90^0$ laminated sandwiched composites.

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A Study on the Dynamic Test of Viscoelastic Material (점탄성 재료의 동적 특성 측정에 관한 연구)

  • Choi, Hyun;Park, Kun-Rok;Kim, Doo-Hoon;Lee, Sang-Jo
    • Journal of KSNVE
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    • v.7 no.6
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    • pp.937-943
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    • 1997
  • Viscoelastic materials have the characteristics of elasticity and viscosity. Unlike the metals which show negligible damping characteristics, the damping characteristic of viscoelastic materials like rubber mounts is very important in the analysis of the dynamic system. So there has been a great interest in measuring the damping characteristics of the material can be measured. One is the resonant method which loss factor can be measured only in the resonant frequency. The other is the nonresonant method. In this paper, the test procedure and the physical meaning of the impedance method are introduced. The impedance test results, the loss factor by the impedance method, are compared to the results of the resonant method including some recommendations in the experimental setup.

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Development and Characteristic Tests of Acrylic Rubber for Viscoelastic Dampers (점탄성 댐퍼용 아크릴 방진고무의 개발 및 특성시험)

  • Park, Jin-Il;Jeoung, Jeoung-Kyo;Park, Hae-Dong;Kim, Young-Chan;Kim, Doo-Hoon
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.722-727
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    • 2001
  • The dynamic characteristics of Viscoelastic(VE) damper are experimentally studied. An experimental test was carried out to study the effects of frequency on the damping and stiffness of VE damper. Various cyclic loading tests are conducted. A good agreement was achieved between the experimental results and analytical model proposed by Kasai et al. Also the damping of acrylic rubber is compared with that of PNR material. It was concluded that the damping value of acrylic rubber is higher than that of PNR material.

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Seismic fragility analysis of conventional and viscoelastically damped moment resisting frames

  • Guneyisi, Esra Mete;Sahin, Nazli Deniz
    • Earthquakes and Structures
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    • v.7 no.3
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    • pp.295-315
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    • 2014
  • This paper presents the results of an analytical study on seismic reliability of viscoelastically damped frame systems in comparison with that of conventional moment resisting frame systems. In order to exhibit the reliability of the frame systems with viscoelastic dampers, seismic reliability analyses were carried out for steel framed buildings, 5 and 12 storeys in height, designed as: (a) Case 1: Conventional moment resisting frame, (b) Case 2: Frame with viscoelastic dampers providing supplemental effective damping ratio of 10%, and (c) Case 3: Frame with viscoelastic dampers providing supplemental effective damping ratio of 20%. Nonlinear time history analyses were utilized to develop seismic fragility curves whilst monitoring various performance objectives. To obtain robust estimators of the seismic reliability, a database including 15 natural earthquake ground motion records with markedly different characteristics was employed in the fragility analysis. The results indicate that depending upon the supplemental effective damping ratio, frames designed with viscoelastic dampers have considerably lower annual probability of exceedance of performance limit states for structural components, showing up to a five-fold reduction in comparison to conventionally designed moment resisting frame system.

Vibration and Damping Characteristics of Viscoelastically Damped Sandwich Plates (점탄성층이 샌드위치된 복합적층판의 진동감쇠 특성)

  • 김재호;박태학;신현정
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.9
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    • pp.2252-2263
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    • 1993
  • The purpose of this study is to verify the vibration and damping characteristics of elastic-viscoelastic-elastic structures, theoretically and experimentally. The forth-order differential equations of motion are derived for the transverse vibration of three-layered plates with viscoelastic core layer. The equations consider both transverse displacements of the constraining layer and the bare base plate as variable and account for the effect of the transverse normal strain and the shear strain of viscoelastic core layer on the vibration of the plates. Finite difference analysis of the equations and experimental measurements are performed on the three-layered plates of completely free boundary condition. Comparative investigations on the theory and the results of direct frequency analysis of NASTRAN are carried out on the same structures.

Behavior of the Flexural Vibration Damping of a Sandwich Beam System with a Partially Inserted Viscoelastic Layer (점탄성층이 부분적으로 삽입된 샌드위치보의 횡진동 감쇠특성)

  • Park, Jin-Taek;Yu, Hyeong-Won;Jang, Seok-Won;Choe, Nak-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.2
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    • pp.225-233
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    • 2002
  • The flexural vibration characteristics of a sandwich beam system with a partially inserted viscoelastic layer have been quantitatively studied using a finite element analysis in combination with a sine-sweep test. Antisymmetric mode shapes of the flexural vibration were visualized by the holographic interferometry and agreed with those calculated by the finite element simulation. Effects of the beam thickness as well as the length and thickness of partial viscoelastic layers on the system loss factor(η$\_$s/) and resonant frequency($\omega$$\_$r/) were significantly large fur the symmetric and antisymmetric modes of the beam system.

Experimenal Study of Dynamic Characteristics of Brace-Typed Dampers using Vibration-resistant Rubbers (방진용 고무를 이용한 가새형 감쇠기의 진동 특성에 관한 실험 연구)

  • 민경원;김진구;조한묵;이성경;호경찬
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1998.04a
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    • pp.381-385
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    • 1998
  • Vibration-resistant rubbers, whose elastic and shear behaviors are similar to viscoelastic materials, are used to make brace-typed dampers to reduce the building vibration. Experimental study is carried out to find the vibration characteristics of the dampers installed in the building model. The natural frequencies and modal damping ratios are obtained from the free vibration test and Fourier analysis. Analytical model of the modal strain energy method are used to find the viscoelastic characteristics of the brace-typed dampers from the experimental results. Finally shaking table test is performed to find the response behavior of the building model under earthquake loading. The present experimental study shows that the brace-typed dampers have the behavior of viscoelastic dampers, which increase the modal damping ratios and viscoelastic characteristics.

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