• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1160-1166
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• 2007

In this study, a new slab system that adjoint precast slabs are connected each other by viscoelastic material is proposed and numerical analysis is performed to evaluate the effect of the slab system on the vibration and noise control. Substructuring is introduced to develope the equation of motion of the slab system and the optimal properties of viscoelastic material are calculated. For the performance evaluation of the new slab system, the sound power and acceleration of the slab are compared with those of two way slab and the slab which the viscoelastic material is not connected. Numerical results show that the sound power of the new slab system can be reduced an amount of 6dB.

• Structural Engineering and Mechanics
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• 제44권1호
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• pp.1-13
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• 2012

In this paper the dynamic behavior of a viscoelastic Timoshenko beam subjected to a concentrated moving load are studied analytically and numerically. The viscoelastic properties of the beam obey the linear standard model in shear and incompressible in bulk. The governing equation for Timoshenko beam theory is obtained in viscoelastic form using the correspondence principle. The analytical solution is based on the Fourier series and the numerical solution is performed with finite element method. The effects of the material properties and the load velocity are investigated on the responses by numerical and analytical methods. In addition, the results are compared with the Euler beam results.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2003년도 기술심포지움 논문집
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• pp.247-250
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• 2003

In this paper, the boundary element analysis of viscoelastic strain energy release ,ate G(t) for the cracked linear viscoelastic materials is attempted. This study proposes the G(t) equation and the calculating method of G(t) by time-domain boundary element analysis for the viscoelastic solids. The G(t) is defined as the derivative of the viscoelastic potential energy $\Pi(t)$ with respect to crack length a. Two example problems are presented to show the applicability of the proposed method to the analysis of the cracked linear viscoelastic solids. Numerical results of example problems show the accuracy and effectiveness of the proposed method.

• Interaction and multiscale mechanics
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• 제6권1호
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• pp.1-14
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• 2013

The aim of this paper is to study the propagation of torsional surface waves in non-homogeneous isotropic layer of finite thickness placed over a homogeneous viscoelastic half-space, when both density and rigidity of the non-homogeneous medium are assumed to vary exponentially with depth. The frequency equations are obtained by using simple method of separation of variables. Further, it is seen that when viscoelastic parameter and non-homogeneity parameter is neglected, the dispersion equation gives the dispersion equations of Love waves in homogeneous, elastic and isotropic layer placed over homogeneous viscoelastic medium. The problem has been solved numerically and the effects of various inhomogeneities of the medium on torsional waves have been illustrated graphically.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1672-1677
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• 2003

In this paper, the spectral element model is derived for the vibration and stability analyses of an axially moving viscoelastic beam subjected to axial tension. The viscoelastic material is represented by using a one-dimensional constitutive equation of hereditary integral type. The accuracy of the present spectral element model is first verified by comparing the eigenvalues obtained by the present spectral element model-based SEM with those obtained by the exact theory and the conventional FEM. The effects of viscoelasticity on the vibration and stability of an example moving viscoelastic beam are numerically investigated.

• 한국소음진동공학회논문집
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• 제21권1호
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• pp.9-17
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• 2011

In this paper, the general equation of motion of damped sandwich beam with multi-viscoelastic material layer was derived based on the equation presented by Mead and Markus. The viscoelastic layer, which has characteristics of complex shear modulus, was assumed to be dominantly under shear deformation. The equation of motion of n-layered damped sandwich beam in bending could be represented by (n+3)th order ordinary differential equation. Finite element model for the n-layered damped sandwich beam was formulated and programmed using higher order shape functions. Several numerical examples were implemented to show the effects of damped material.

• Steel and Composite Structures
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• 제37권1호
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• pp.51-73
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• 2020

The present paper investigates the simultaneous resonance behavior of spiral stiffened multilayer functionally graded (SSMFG) cylindrical shells with internal and external functionally graded stiffeners under the two-term large amplitude excitations. The structure is embedded within a generalized nonlinear viscoelastic foundation which is composed of a two-parameter Winkler-Pasternak foundation augmented by a Kelvin-Voigt viscoelastic model with a nonlinear cubic stiffness. The cylindrical shell has three layers consist of ceramic, FGM, and metal. The exterior layer of the cylindrical shell is rich ceramic while the interior layer is rich metal and the functionally graded material layer is located between these layers. With regard to classical shells theory, von-Kármán equation, and Hook law, the relations of stress-strain are derived for shell and stiffeners. The spiral stiffeners of the cylindrical shell are modeled according to the smeared stiffener technique. According to the Galerkin method, the discretized motion equation is obtained. The simultaneous resonance is obtained using the multiple scales method. Finally, the influences of different material and geometrical parameters on the system resonances are investigated comprehensively.

• 전산구조공학
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• 제10권2호
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• pp.131-138
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• 1997

이 논문에서는, 균일한 횡방향 인장변형률이 작용하는 조건에서 강체모재들을 결합하고 있는 점탄성 접착재층의 계면모서리에 발생하는 응력 특이성을 조사하고있다. Williams방법을 응용하여 라플라스 변형공간에서 특성방정식을 구하였고, 주어진 점탄성 모델에 대해서 변형공간에서의 특성방정식을 시간공간으로 해석적으로 전환하였다. 시간 공간에서의 특이차수는 수치적으로 계산하였다. 계면을 따라 발생하는 응력의 특성을 조사하는데 시간영역 경계요소법을 적용하였다. 수치해석 결과에 의하면, 특이차수는 시간이 경과함에 따라 커지는 반면에, 자유모서리 응력확대계수는 시간에 따라 이완되는 특성을 보여주고 있다.

• 유변학
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• 제11권1호
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• pp.9-17
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• 1999

본 연구에서는 페놀 수지/탄소섬유 복합재료가 상온에서부터 $400^{\circ}C$까지의 온도범위에서 유리 전이와 분해반응을 경험하면서 나타내는 점탄성 특징을 연구하였다. 가교 결합된 페놀메트릭스의 전형적인 유리전이에 따라 저장 탄성율(storage modulus)은 유리전이에 의하여 감소하였고 고무상태(rubbery state)에 도달함과 동시에 후경화 반응과 분해 반응 등을 포함하는 복합적인 고온반응에 의하여 증가하다가, 최대점을 보인 후 다시 감소하는 모습을 보였다. 유리전이 과정은 시간-온도 중첩원리에 따라 해석하였으나, 분해반응이 수반된 고온에서의 점탄성 특징은 저장 탄성율을 수직 및 수평 방향으로 이동시키어 마스터 커브를 완성 할 수 있었다. 이러한 실험적 결과를 토대로 아레니우스식과 Havriliak-Negami식에서 유추된 점탄성 모델을 이용하여 유리전이와 분해반응이 연속적으로 진행되는 과정을 정량적을 해석할 수 있었다. 이때의 완화시간은 유전이 과정을 통하여 감소하다가 고무상태에 이르러 최소값을 보여주고 이후로는 고온반응에 의하여 증가하는 모습을 보여주었다. 본 연구에서 제안된 점탄성 해석 방법은 반응이 수반된 열경화성 복합재료가 보여주는 점탄성 계수의 복잡한 거동을 온도와 주파수(frequency)에 따라 정확하게 묘사함으로서 이 모델링의 유용성을 증명 할 수 있었다.

• 한국해양공학회지
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• 제25권1호
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• pp.67-72
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• 2011

Offshore structures, such as a platform, a buoy, or a floating vessel, are exposed to several dynamic loads, and viscoelastic damping material is used to reduce the vibration of offshore structures. It is important to know the properties of viscoelastic materials because loss factor and Young's modulus of the viscoelastic damping material are dependent on frequency and temperature. In this study, an advanced technique for obtaining accurate loss factor and Young's modulus of the viscoelastic damping material is introduced based on a multi degree of freedom curve-fitting method and the RKU (Ross-Kerwin-Ungar) equations. The technique is based on a modified experimental procedure from ASTM E 756-04. Loss factor and Young's modulus of the viscoelastic damping material are measured for different temperatures by performing the test in a temperature-controlled vibration measurement room where temperature varies from 5 to 45 degrees Celsius.