• Title, Summary, Keyword: 점탄성층

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A study on the sliding rigid indentor over the viscoelastic layer supported by the elastic half-space (탄성체로 기대된 점잔성체층에서의 강성체의 운동해석)

  • Nam, J. W.
    • Journal of the korean Society of Automotive Engineers
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    • v.5 no.3
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    • pp.56-63
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    • 1983
  • 강성체로된 견인물체가 탄성무한경면으로 지지된 점탄성층 위를 미끄러져 갈 때 접촉구간에서의 압력분포와 마찰 특성을 고찰하였다. 즉, 접촉구간에서의 강성체의 모양과 압력분포에 관한 적분 방정식을 구하고, 점탄성층의 두께가 접촉구간에 비하여 충분히 두꺼울 때 압력분포와 마찰계 수의 근사해를 구하였다. 압력분포의 모양은 점탄성층의 물성을 표시하는 지수값, 즉 .alpha.<1/2, .alpha.=1/2, .alpha.>1/2에 따라서 크게 다르다. 한편, 수치해석에 의하면 마찰 계수에 대한 근 사해는 강성체의 미끄럼 속도, 점탄성 층의 두께, 탄성체의 영율 (E$_{o}$ )과 점탄성층의 시효 성탄성계수 (E$_{v}$ )의 차, 즉 E$_{o}$ /E$_{v}$ 에 따라 변화함을 알 수 있다. 즉, 탄성체가 점탄성층에 비하여 딱딱하면 할수록, 또 강성체 속도가 느리면 느릴수록 마찰계수는 작아진다. 그리고 불성의 지수(.alpha.)가 커지면 커질수록 근사해의 수렵 속도는 느려지게 되고 지 수(.alpha.)가 1에 가까워지면 점탄성층의 탄성효과는 점성효과에 비하여 거의 무시할 수 있으며 근사해는 의미가 없어지게 된다.

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Optimum Design of Viscoelastic Layered Beam to Minimize Flexural Vibration (굽힘진동 감쇠를 위한 점탄성 적층보의 최적 설계)

  • Sa-Soo Kim;Dae-Seung Cho;Min-Woo Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.1
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    • pp.90-98
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    • 1999
  • For the control of vibration and noise of metal structures having relatively low damping, viscoelastic materials are widely used and usually attached at metal structures with an additional constraining layer to secure them. The damping and elastic properties of structures having constrained viscoelastic material layers are dependent on not only temperature and frequency but also their thicknesses. Hence, optimal design of the thicknesses of viscoelastic and constraining layers for a certain base structure are very important to maximize their efficiency and to lighten their weight. In this study, the variation of loss factor of beams having a constrained viscoelastic layer according to the change of thickness has been carefully investigated. From these, optimal design method of the minimum thickness beam having a given loss factor is suggested and numerically verified for a real beam.

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Excitation and System Identification of a Full-Scale Five-Story Structure for the Application of Viscoelastic Dampers (점탄성 감쇠기 적용을 위한 실물크기 5층 건물의 가진 및 시스템 식별)

  • 민경원;이상현;김진구;이영철;이승준;최현훈
    • Journal of the Earthquake Engineering Society of Korea
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    • v.7 no.3
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    • pp.1-7
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    • 2003
  • Excitation and system identification are carried out for a full-scale five-story structure to obtain fundamental data which will be used for the design of viscoelastic dampers, The hybrid mass driver(HMD) installed on the fifth floor was employed as external exciter to provide excitation for the building, Each floor response was measured and processed to find out where and how the viscoelastic dampers are located and designed. The sine-sweep and white noise loadings were applied to the structure by the HMD to obtain dynamic characteristics such as natural frequencies, damping ratios, and modes, The identified building was experimentally investigated again with the designed viscoelastic dampers installed at inter-stories to obtain the response behavior in the companion paper.

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.

A Study on the Characteristics of Vibration Damping of a Beam with Inserted Viscoelastic Layer (점탄성층을 삽입한 3층 적층보의 진동감쇠특성에 관한 연구)

  • 박응순;박세만;박명균;박상규
    • Journal of KSNVE
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    • v.7 no.3
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    • pp.511-519
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    • 1997
  • For a number of years it has been known that flexural vibration in a beam and plate can be damped by the application of layer of damping (viscoelastic) material that is in turn constrained by a backing layer or foil. In this study, a quantitative analysis of damping of the sandwich beam has been performed by using impact test. The damping is characterized by the loss factor .etha. in which the damping is normalized by imaginary part of the complex bending stiffiness of the beam. Results show that the relative thickness of the sandwich beam gives more effect on the riatural-frequencies and loss factor than the variation of width does. It is also shown that the Ross-Kerwin-Ungar equation and impact test can be effectively used to identify the damping characteristic of the sandwich beam and viscoelastic material.

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Analysis of the Vibration Damping of a Single Lap Joint Beam with Partial Dampers (겹침이음부와 부분층댐퍼가 부착된 보의 진동감쇠해석)

  • 박정일;최낙삼
    • Composites Research
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    • v.12 no.2
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    • pp.26-35
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    • 1999
  • This paper presents the vibration damping characteristic of a single lap joint beam with partial dampers analyzed using the model strain energy method and the harmonic response analysis which were based on a finite element model. The two finite element analysis methods exhibited very similar results of the resonant frequency and system loss factor which were comparable to those by the theoretical analysis. Effects of the location of partial dampers and elastic moduli and thickness of their layers on the system loss factor were studied. The damping effects due to changes of modules and loss factor of the viscoelastic layer in lap joint and partial dampers were also studied. Consequently, the geometrical and material conditions at maximizing the system loss factor were suggested.

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Viscoelastic Stress Analysis of Adhesive-bonded Cylindrical by FEM (유한요소법을 이용한 원통체의 점탄성 응력 해석)

  • Park, Sung-Jin
    • Journal of the Society of Disaster Information
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    • v.15 no.2
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    • pp.259-267
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    • 2019
  • Purpose: In this paper adhesive-bonded cylindrical lap joints are analyzed by assuming that the adherends are elastic and the adhesive is linearly viscoelastic. Method: The distribution of the stresses in the adhensive is evaluated using the Finite Element Method. Nuverical examples for identical and different adherends bonded through a four parameter viscoelastic solid adhesive are illustrated. Results: The stress distribution in the adhesive layer with respect to time is shown. The stress distribution in the adhesive layer with respect to time is shown. The results are also shown that adherend thickness and elastic modulus give effect on the normalized stress. Conclusion: In this study, the stress distribution of the adhesive layer of the wrapped cylindrical body considering the viscoelasticity of the adhesive layer was numerically analyzed by using a four - element elastomer model.

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

  • 박진택;최낙삼
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.224-227
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    • 2000
  • Modal damping characteristics of the flexural vibration of a sandwich beam with paaially inserted viscoelastic layer have been quantitatively studied using the finite element analysis in combination with an experiment. 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 length and thickness of partial viscoelastic layers on the system loss factor($\mu$) and resonant frequency($\omega$) were considerably latge at both symmetric and antisymmetric modes of the sandwich beam.

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Optimal Viscoelastic Layered Dynamic Vibration Absorber (점탄성층을 갖는 내다지보형 동흡진기의 최적설계)

  • Im, Seong-Dae;Lee, Si-Bok
    • The Journal of the Acoustical Society of Korea
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    • v.8 no.1
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    • pp.31-37
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    • 1989
  • The effectiveness of using a composite beam with constrained visco-elastic layer as a dynamic vibration absorber is investigated. The performance of this absorber is evaluated in terms of displacement transmissibility when to a primary beam with built-in ends and compared to that of the uniform beam absorber. The results of analysis and design show that it is possible to suppress simultaneoulsy the peak transmissibilities at two or more resonance frequencies and the optimal parameters are located within the available viscoelastic material properties.

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지그재그 보요소를 이용한 응력해석 및 진동해석

  • Lee, Deog-Gyu
    • Aerospace Engineering and Technology
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    • v.3 no.2
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    • pp.149-159
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    • 2004
  • Dynamic analysis of laminated beams with a embedded damping layer under tensional and compressive axial load is investigated. Improved Layer-Wise Zig-Zag Beam Theory and Interdependent Kinematic Relation are incorporated to model the laminated beams with a damping layer and a corresponding beam zig-zag finite element is developed. Flexural frequencies and modal loss factors under tension or compression axial load are calculated based on Complex Eigenvalue Method. The effects of the axial tensional and compressive load on the frequencies and loss factors are discussed.

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