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접촉 역학적 접근에 의한 점탄성/탄성, 점탄성/점탄성 재료간의 접합 에너지 측정
이찬(C. Lee),엄윤용(Y.Y. Earmme) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
The nanoimprint lithography technology makes higher density of semiconductor device and larger<br/> capacity of storage media. In this technology the induced damage while detaching polymer pattern from mold<br/> should be minimized. In order to analyze the problem, the basic knowledge of adhesion between the polymer<br/> and the mold is required. In this study a contact experiment of polyisobutylene specimen with spherical steel<br/> tip and polyisobutylene bead tip was conducted using nano indenter. During the contact experiment with<br/> various loading rate under load control the contact behavior of viscoelastic material was measured, i.e., the<br/> load and displacement between the tip and the specimen were measured. The data was analyzed by HBK<br/> model to obtain the stress intensity factor of contact edge and the contact radius as a function of time. Also the<br/> adhesion energies between steel/polyisobutylene and polyisobutylene/polyisobutylene were obtained<br/> employing the analysis of the crack of viscoelastic material by Schapery.
신효영(H. Shin),최승태(S. T. Choi),엄윤용(Y. Y. Earmme) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Elastic field in anisotropic/isotropic bimaterial due to a point force or a dislocation is obtained where the<br/> interface between the anisotropic and isotropic half spaces lies along x₂=0 . The stress in anisotropic<br/> material is expressed in terms of the analytic functions based on the Stroh formalism while that in isotropic<br/> material is expressed in terms of the Muskhelishvili potentials, with the singularity located either in the<br/> anisotropic or isotropic material. The solution technique is based on the analytic continuation of the analytic<br/> functions defined in the lower (or upper) half space into the upper (or lower) half space.
브리지 및 원형 금 박막의 기계적 물성 및 계면파괴인성치 측정
최우성(W.S. Choi),최승태(S.T. Choi),손상욱(S.U. Son),이승섭(S.S. Lee),양세영(S.Y. Yang),엄윤용(Y.Y. Earmme) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
In order to measure the mechanical properties of gold films on Si substrate, two types of specimens, i.e., bridged films and circular membranes, are manufactured. Using the wedge tip, the bridged films are indented so that the bridged gold films are pushed off, which is called as V-peel test. The load-deflection curves obtained by the V-peel tests are analyzed with the concept of geometrically nonlinear beam by using the minimum potential energy theory together with Ritz method. Young’s modulus and residual stress of the bridged gold films are obtained. Blister test is also conducted to measure the Young’s modulus and residual stress of the circular membrane specimens, of which deformation is measured by Twyman-green interferometer. By gradually increasing the applied pressure in the blister test, the interfacial fracture toughness between the gold film and Si substrate is measured.
다중스케일 모델링을 이용한 나노임프린트 리소그라피 전산모사
권성진(Sungjin Kwon),강지원(Jeewon Kang),김성엽(Sung Youb Kim),이윤섭(Yoon Sup Lee),엄윤용(Y.Y. Earmme),임세영(Seyoung Im) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Nano-Imprint Lithography(NIL) is a patterning technique at nano-size in limelight of requesting to reduce thespace between patterns. NIL is modeled under systematic multiscale consideration for a coarse grained molecular dynamics model. Force fields of a united atom model and a bead-spring model for the resin materials, obtained from fitting with the quantum mechanical solution, are employed for computation. The initial configuration of the polymer resin for UV nano imprinting is obtained from Monte Carlo simulation and the initial relaxation procedure. To simulate NIL process, we employ the Nose-Poincare thermostat for temperature controlled Molecular Dynamics (MD), which exhibits enhanced numerical stability even when the temperature fluctuation is large in the case of small number of particles system. Various aspects of NIL process from the mechanics view are discussed based on the numerical solution from the present multiscale modeling.
이종길,Johnson, William C.,엄윤용 대한금속재료학회(대한금속학회) 1978 대한금속·재료학회지 Vol.16 No.5
석출물과 관련되는 탄성변형과 탄성변형에너지를 요약 재검토하였다. 약 20년 전에 Eshelby의 획기적인 연구 결과가 발표된 후 이 문제에 관한 많은 진보가, 특히 이방성결정체를 중심으로 이루어져 왔다. 제일 먼저 이방성 결정고체내에 함유되고 있는 타원형의 석출물과 관련되는 탄성변형 에너지를 몇개의 대표적인 결과를 예를 들어 검토하고, 다음으로 정육면체와 같은 다른 형상을 갖는 석출물의 탄성변형이 어떻게 다른가를 고찰하였다. 두개의 구형상 석출물간에 작용하는 에너지를 실험적으로 관찰되고 있는 석출물의 질서적인 배열형상과 비교 논의하였다. 마지막으로 핵형성과정에서 어떻게 탄성변형 에너지가 영향을 주는가와 탄성변형이 소성적으로 이완이 가능할 때 어떻게 달라지는가를 검토하였다. The elastic strains and strain energies associated with precipitates are reviewed. Since the classical works of Eshelby were published almost two decades ago. there has been a rapid progress in understanding this interesting problem, especially in the anisotropic case. The elastic strain energy of inhomogenous ellipsoidal precipitates in anisotropic crystalline solids is discussed with some representative numerical results. The nature of the elastic strains associated with a non-ellipsoidal precipitate such as a cuboid is also described. The elastic interaction energy of two spherical precipitates in an anisotropic matrix is discussed in connection with some experimental observations of precipitate alignments. Finally, some of the results are applied to the homogeneous nucleation theory and plastic relaxation of the transformation stress is also briefly discussed.