• 제목/요약/키워드: viscoelastic material

검색결과 368건 처리시간 0.021초

최적화 기법을 이용한 점탄성물질의 분수차 미분모델 물성계수 추정 (Identification of Fractional-derivative-model Parameters of Viscoelastic Materials Using an Optimization Technique)

  • 김선용;이두호
    • 한국소음진동공학회논문집
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    • 제16권12호
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    • pp.1192-1200
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    • 2006
  • Viscoelastic damping materials are widely used to reduce noise and vibration because of its low cost and easy implementation, for examples, on the body structure of passenger cars, air planes, electric appliances and ships. To design the damped structures, the material property such as elastic modulus and loss factor is essential information. The four-parameter fractional derivative model well describes the dynamic characteristics of the viscoelastic damping materials with respect to both frequency and temperature. However, the identification procedure of the four-parameter is very time-consuming one. In this study a new identification procedure of the four-parameters is proposed by using an FE model and a gradient-based numerical search algorithm. The identification procedure goes two sequential steps to make measured frequency response functions(FRF) coincident with simulated FRFs: the first one is a peak alignment step and the second one is an amplitude adjustment step. A numerical example shows that the proposed method is useful in identifying the viscoelastic material parameters of fractional derivative model.

Post-buckling analysis of sandwich FG porous cylindrical shells with a viscoelastic core

  • Foroutan, Kamran;Dai, Liming
    • Steel and Composite Structures
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    • 제45권3호
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    • pp.349-367
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    • 2022
  • In this research, an approach combining a semi-analytical method and an analytical method is presented to investigate the static and dynamic post-buckling behavior of the sandwich functionally graded (FG) porous cylindrical shells exposed to external pressure. The sandwich cylindrical shell considered is composed of a viscoelastic core and two FG porous (FGP) face layers. The viscoelastic core is made of Kelvin-Voigt-type material. The material properties of the FG porous face layer are considered continuous through each face thickness according to a porosity coefficient and a volume fraction index. Two types of sandwich FG porous viscoelastic cylindrical shells named Type A and Type B are considered in the research. Type A shell has the porosity evenly distributed across the thickness direction, and Type B has the porosity unevenly distributes across the thickness direction. The FG face layers are considered in two cases: outside metal surface, inside ceramic surface (OMS-ICS), and inside metal surface, outside ceramic surface (IMS-OCS). According to Donnell shell theory, von-Karman equation, and Galerkin's method, a discretized nonlinear governing equation is derived for analyzing the behavior of the shells. The explicit expressions for static and dynamic critical buckling loading are thus developed. To study the dynamic buckling of the shells, the governing equation is examined via a numerical approach implementing the fourth-order Runge-Kutta method. With a procedure presented by Budiansky-Roth, the critical load for dynamic post-buckling is obtained. The effects of various parameters, such as material and geometrical parameters, on the post-buckling behaviors are investigated.

A comprehensive computational approach to assess the influence of the material composition on vibration, bending and buckling response of FG beam lying on viscoelastic foundation

  • Brahim Laoud;Samir Benyoucef;Attia Bachiri;Rabbab Bachir Bouiadjra;Abdelouahed Tounsi;Mahmoud M Selim;Hosam A. Saad
    • Steel and Composite Structures
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    • 제52권1호
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    • pp.45-56
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    • 2024
  • This paper proposes an analytical solution for the free vibration, bending and buckling a functionally graded (FG) beam resting on viscoelastic foundation. The materials characteristics of the FG beam are considered to be varying across the thickness according several power law functions. The governing equations are found analytically using a quasi-3D model that contains undetermined integral forms and involves few unknowns to derive. Navier's method for simply supported beam is employed to solve the problem. Numerical examples are presented and studied to demonstrate the accuracy and effectiveness of the proposed model. Then, a detailed parametric study is presented in the form of tables and graphs to study and analyze the effects of the different parameters on the response of FG beams with different material compositions resting on a viscoelastic foundation.

점탄성 재료를 이용한 무힌지 로터 감쇠 증대 (Damping Enhancement of Hingeless Rotor System Using Viscoelastic Material)

  • 김도형;고은희;송근웅;이욱
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2004년도 추계학술대회논문집
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    • pp.637-640
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    • 2004
  • Structural damping enhancement of composite flexures and aeroelastic stability of a hingeless rotor system are investigated. Constrained layer damping (CLD) treatments are applied in order to increase structural damping of flexures. Material damping property of viscoelastic layer is modelled as complex modulus. Modal analysis of composite flexures with attached viscoelastic layers and constraining layers are performed using MSC/NASTRAN and the effects of CLD treatments are verified with the modal test results. The composite flexures with CLD are applied to a 4-bladed, 2-meter diameter, Froude-scaled, soft-in-plane hingeless rotor system. The aeroelastic stability is tested at hovering condition and the effects of CLD are investigated. It is shown that the CLD treatment effectively enhance the aeroelastic stability at hover.

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접촉 역학적 접근에 의한 점탄성/탄성, 점탄성/점탄성 재료간의 접합 에너지 측정 (A Measurement of Adhesion Energy between Viscoelastic/Elastic, Viscoelastic/Viscoelastic Materials Using Contact Mechanics Approach)

  • 이찬;엄윤용
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 춘계학술대회
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    • pp.1030-1035
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    • 2003
  • The nanoimprint lithography technology makes higher density of semiconductor device and larger capacity of storage media. In this technology the induced damage while detaching polymer pattern from mold should be minimized. In order to analyze the problem, the basic knowledge of adhesion between the polymer and the mold is required. In this study a contact experiment of polyisobutylene specimen with spherical steel tip and polyisobutylene bead tip was conducted using nano indenter. During the contact experiment with various loading rate under load control the contact behavior of viscoelastic material was measured, i.e., the load and displacement between the tip and the specimen were measured. The data was analyzed by HBK model to obtain the stress intensity factor of contact edge and the contact radius as a function of time. Also the adhesion energies between steel/polyisobutylene and polyisobutylene/polyisobutylene were obtained employing the analysis of the crack of viscoelastic material by Schapery.

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Nonlinear thermal vibration of FGM beams resting on nonlinear viscoelastic foundation

  • Alimoradzadeh, M.;Akbas, S.D.
    • Steel and Composite Structures
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    • 제44권4호
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    • pp.557-567
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    • 2022
  • Nonlinear free vibration analysis of a functionally graded beam resting on the nonlinear viscoelastic foundation is studied with uniform temperature rising. The non-linear strain-displacement relationship is considered in the finite strain theory. The governing nonlinear dynamic equation is derived based on the finite strain theory with using of Hamilton's principle. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The influences of temperature rising, material distribution parameter, nonlinear viscoelastic foundation parameters on the nonlinear free response and phase trajectory are investigated. In this paper, it is aimed that a contribution to the literature for nonlinear thermal vibration solutions of a functionally graded beam resting on the nonlinear viscoelastic foundation by using of multiple time scale method.

하이브리드 방법을 이용한 자동차 루프의 진동제어 (Hybrid Damping Treatment for Vibration control of an Automotive Roof using Viscoelastic and Piezoelectric material)

  • 나정기;문성진;김찬묵;강영규
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2004년도 추계학술대회논문집
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    • pp.994-998
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    • 2004
  • Hybrid method is used to suppress vibration of an automotive roof surface. The hybrid method proposed in this paper is implemented experimentally using both viscoelastic and piezoelectric material. The piezoelectric material is used to control the vibration of automotive structure for lower range of frequencies and the experiment of vibration control using viscoelastic material has been carried out suppress vibrations of high frequency range mark. At first the plate controlled by using hybrid method has been .implemented to verify the performance for suppressing vibration. Then the experiment has been applied to the automotive roof structure.

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Dynamic characteristics of viscoelastic nanobeams including cutouts

  • Rabab A. Shanab;Norhan A. Mohamed;Mohamed A. Eltaher;Alaa A. Abdelrahman
    • Advances in nano research
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    • 제14권1호
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    • pp.45-65
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    • 2023
  • This paper aimed to investigate the nonclassical size dependent free vibration behavior of regularly squared cutout viscoelastic nanobeams. The nonlocal strain gradient elasticity theory is modified and adopted to incorporate the viscoelasticity effect. The Kelvin Voigt viscoelastic model is adopted to model the linear viscoelastic constitutive response. To explore the influence of shear deformation effect due to cutout, both Euler Bernoulli and Timoshenko beams theories are considered. The Hamilton principle is utilized to derive the dynamic equations of motion incorporating viscoelasticity and size dependent effects. Closed form solutions for the resonant frequencies for both perforated Euler Bernoulli nanobeams (PEBNB) and perforated Timoshenko nanobeams (PTNB) are derived considering different boundary conditions. The developed procedure is verified by comparing the obtained results with the available results in the literature. Parametric studies are conducted to show the influence of the material damping, the perforation, the material and the geometrical parameters as well as the boundary and loading conditions on the dynamic behavior of viscoelastic perforated nanobeams. The proposed procedure and the obtained results are supportive in the analysis and design of perforated viscoelastic NEMS structures.

PARAMETER IDENTIFICATION FOR NONLINEAR VISCOELASTIC ROD USING MINIMAL DATA

  • Kim, Shi-Nuk
    • Journal of applied mathematics & informatics
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    • 제23권1_2호
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    • pp.461-470
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    • 2007
  • Parameter identification is studied in viscoelastic rods by solving an inverse problem numerically. The material properties of the rod, which appear in the constitutive relations, are recovered by optimizing an objective function constructed from reference strain data. The resulting inverse algorithm consists of an optimization algorithm coupled with a corresponding direct algorithm that computes the strain fields given a set of material properties. Numerical results are presented for two model inverse problems; (i)the effect of noise in the reference strain fields (ii) the effect of minimal reference data in space and/or time data.

다층 점탄성재료의 진동감쇠 특성에 관한 연구 (Vibration Damping Analysis of Multi-Layered Viscoelastic Material)

  • 윤영식;황동환;이상조
    • 소음진동
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    • 제4권4호
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    • pp.487-496
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    • 1994
  • Recently, the application of viscoelastic material in the field of vibration isolation has gradually increased due to its achievement in structural damping capacity, and many of the theoretical and experimental study has been carried out. In this study, the dynamic characteristics of the visoelastically supported cantilever beam, of which govering equation is based on the Bernoulli- Euler equation, is analyzed theoretically and experimentally. Expression for stiffness of multi-layered viscoelastic materal has been developed using variables such as frequency and number of layers, and further, based on this expression, damping characteristic of the beam is investigated with experimental verification.

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