• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1045-1050
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• 2007

Equations of motion of rotating cantilever curved beams are derived based on a dynamic modeling method developed in this paper. The Kane's method is employed to derive the equations of motion. Different from the classical linear modeling method which employs two cylindrical deformation variables, the present modeling method employs a non-cylindrical variable along with a cylindrical variable to describe the elastic deformation. The derived equations (governing the stretching and the bending motions) are coupled but linear. So they can be directly used for the vibration analysis. The coupling effect between the stretching and the bending motions which could not be considered in the conventional modeling method is considered in this modeling method. The natural frequencies of the rotating curved beams versus the rotating speed are calculated for various radii of curvature and hub radius ratios.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.28-32
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• 2007

Sufficient Conditions are proposed herein for analytically obtaining fully orthotropic (A16=A26=0, Bij=0, D16=D26=0) laminate stacking sequences together with a brief literature survey. A number of specially chosen anti-symmetric balanced stacking sequences are analytically studied, in which all coupling stiffnesses including B16 and B26 are identically zero. Those specially chosen anti-symmetric balanced stacking sequences are then arranged symmetrically with respect to the laminate mid-plane to obtain a number of symmetric stacking balanced stacking sequences of which the elastic stiffnesses are fully orthotropic.

• Coupled systems mechanics
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• v.2 no.4
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• pp.303-327
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• 2013

The coupled free vibration of flexible structures and on-board liquid in zero gravity space was analyzed, considering the spacecraft main body as a rigid mass, the flexible appendages as two elastic beams, and the on-board liquid as a "spring-mass" system. Using the Lagrangians of a rigid mass (spacecraft main body), "spring-mass" (liquid), and two beams (flexible appendages), as well as assuming symmetric motion of the system, we obtained the frequency equations of the coupled system by applying Rayleigh-Ritz method. Solving these frequency equations, which are governed by three system parameters, as an eigenvalue problem, we obtained the coupled natural frequencies and vibration modes. We define the parameter for evaluating the magnitudes of coupled motions of the added mass (liquid) and beam (appendages). It was found that when varying one system parameter, the frequency curves veer, vibration modes exchange, and the significant coupling occurs not in the region closest to the two frequency curves but in the two regions separate from that region.

• Structural Engineering and Mechanics
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• v.6 no.6
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• pp.613-632
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• 1998

A coupling system for a structure accelerating through a fluid is considered which is composed of the structure and the fluid in a finite surrounding volume. Based on the variational principle, the finite element equations of hydrodynamic pressure and structural elastic vibration are deduced. A numerical method is given for the dynamic character and response of the structure which takes the coupled fluid into account. The effect of axial inertial forces on the dynamic character and response of rapidly accelerating structures is also considered.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.1
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• pp.25-32
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• 1989

A finite element program for material nonlinear fracture analysis of reinforced concrete shell was developed. This method can be used to trace the load-displacement response and crack propagation through the elastic and inelastic ranges. A layered isoparametric flat finite element considering the coupling effect between the in-plane and the bending action was developed. Mindlin plate theory taking account of transverse shear deformation was used. The validity of the present program was proved by comparing the numerical results with Hedgren's experimental data.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.342-350
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• 1993

Experiments are performed to determine the dependence of torsional rigidity upon the cross-sectional area for specimens of dense polyurethane foam. Testing equipment was designed and fabricated in the laboratory to satisfy the experimental characteristics. Results show the increase of torsional rigidity compared to the expected value based on the conventional elasticity. And this can be explained that the consideration of the internal motions of constitutive particles predicts the elastic behavior of the material better.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.2
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• pp.135-142
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• 2008

Experimental studies on the aerodynamic coupling effect on natural frequencies, critical speed and flutter instability of rotating disks are investigated in this paper. The theoretical analysis uses a fluid-structure model where the aerodynamic effects are represented in terms of elastic, lift and damping and stiffness components. The experiments performed using a vacuum chamber and ASMO/DVD disks rotating in vacuum, open and enclosure in several gaps with stationary wall give three main results. One is that the aerodynamic effect by the surrounding air reduces the natural frequencies and critical speeds of the vibration modes. The second is that natural frequency of disks rotating in open air is larger than that in enclosure. Finally, it is shown that the disk vibration is reduced as the gap between the disk and the rigid wall decreases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.311-314
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• 1997

According to the development of industrial equipment such as semiconductor manufacturing machines, optical device, and precision machine tool, a high-precision translation system with wide range has been required. This paper describes a high-precision 2-axis translation system, which consists of microstage and global stage. In order to achieve the highresolution in the long range, some engineering techniques are used. Three linear guides with flexible coupling are adopted to reduce the motor vibration in the global stage. A simple elastic hinge structure activated by five PZT is applied to reduce the angular dev~atlon. As the result of combination of microstage and global stage associated with some engineering techniques, the 2-axis translation system can measure the 200 X 200 mrn range with the nanometer accuracy.

• The Korean Journal of Rheology
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• v.4 no.2
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• pp.107-115
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• 1992

전방향족 에스테르계 열방성 액정중합체(LCP) 벡트라(Vectra)와 폴리카보네이트 (PC)를 무게비 30/70으로 구성한 고분자 블렌드를 확장되는 다이를 통하여 압출한후 압출쉬 트의 탄성 및 점탄성 특성을 만능시험기(UTM)와 동적기계적 스펙트로터(RDS)를 이용하여 측정하였다. 블렌드의 기계적 특성은 기지재인 PC의 ductility에도 불구하고 순수 LCP보다 도 더 brittle하였다. 그러나 탄성률이나 인장강도 모두 PC보다 훨씬 높게 나타나 보강효과 가 확인되었다. 이러한 보강효과는 복합계 내부에서 스스로 형성된 직경 2~10$\mu$m 정도의 거대 섬유소 그리고 거대 섬유소는 다시 직경 0.05$\mu$m 정도의 미세섬유로서 구성된 형태학 적 특성으로 설명될수 있었다. 한편 블렌드의 점탄성 거동은 마치 entanglement coupling이 높은 계의 특성과 비슷하였으며 시편의 위치에 따른 특성변화는 관찰되지 않았고 순수산 LCP의 점탄성 특성과 아주 유사하였다.

• Korea-Australia Rheology Journal
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• v.11 no.4
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• pp.321-328
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• 1999

This paper discusses the rheology of complex interfaces comprised of amphiphilic materials that are susceptible to flow-induced orientation and deformation. The consequence of the coupling of the film micro-structure to flow leads to nonlinear rheology and surface fluid dynamics. Experimental methods designed to determine the mechanical rheological material functions of fluid-fluid interfaces as well as local, molecular and morphological responses are presented. These include a newly developed interfacial stress rheometer, flow ultraviolet dichroism, and Brewster-angle microscopy. These techniques are applied to a number of complex interfaces ranging from low molecular weight amphiphiles to polymer monolayers. Nonlinear flow phenomena ranging from two-dimensional nematic responses to highly elastic surface flows that manifest surface normal stress differences and elongational viscosities are described.