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임재혁(Jae Hyuk Lim),김경원(Kyung-Won Kim),김선원(Sun-Won Kim),김진희(Jin-Hee Kim),황도순(Do-Soon Hwang) 한국항공우주연구원 2010 항공우주산업기술동향 Vol.8 No.1
본 논문에서는 최근에 개발된 고해상도 지구관측위성의 본체 형상설계 동향에 대해 기술하고자 한다. 인공위성의 본체는 임무, 탑재체, 발사환경, 임무특성, 자세제어 및 추진시스템에 따라 다양한 형상을 갖는다. 또한 2000년대 들어서 시작된 위성영상의 상업화에 따른 영상수요의 증가는 고해상도 영상을 신속히 많이 획득할 수 있는 위성시스템을 요구하고 있다. 이러한 요구에 맞춰 위성의 본체는 가벼우면서도 안정적으로 탑재체를 지지할 수 있도록 설계되고 있으며, 이 중에 형상설계 변화를 본 논문에서 집중적으로 살펴본다. The goal of the paper is to discuss the recent trend of the configuration of high resolution LEO(Low Earth Orbit) EO(Earth Observation) satellites. The satellite configuration is decided by considering several factors such as mission, payloads, launch vehicle, propulsion and attitude control module. The advent of commercial companies selling satellite's images in 2000's requires additional changes of the satellite system to be capable of obtaining many high resolution images quickly. In order to meet customer's needs, the overall configuration of satellites is designed to be compact and stable without the loss of structural integrity and reliability. Among design changes, the configuration change of satellites is treated intensively in the paper.
임재혁(Jae Hyuk Lim),한만희(Man-Hee Han),이준연(Jun-Youn Lee),박정순(Jeong Soon Park),엄윤용(Youn Young Earmme),임세영(Seyoung Im) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Prediction of warpage and residual stress in semiconductor chip devices play an important role in chip design. However, there are a few uncertainties in warpage prediction due to unknown patterning material properties, and moisture effect on polymer film. To estimate patterning material properties, we adopt a composite plate analysis and experimental techniques. and measure the warpage of chip after drying at about 250℃ for 30min to remove moisture. In 100㎛, 80㎛ chip cases, finite element analysis result shows a good agreement with measured values, but for 50㎛ and 60㎛ chip cases, there exist a substantial deviation from the measured values due to local deformation from imperfection and defects inherently embedded in the patterning layer and nonuniform bonding between PIcoating and silicon.
임재혁(Jae Hyuk Lim),김경원(Kyung-Won Kim),김선원(Sun-Won Kim),황도순(Do-Soon Hwang) 한국항공우주연구원 2009 항공우주산업기술동향 Vol.7 No.2
항공우주산업과 관련된 항공기, 인공위성, 발사체 등의 구조체 개발을 위해서는 설계단계에서부터 해석 및 제작에 이르기까지 다양한 전산기술(CAD/CAE/CAM)이 널리 적용되고 있다. 이 중 구조해석을 위해서는 NASTRAN, ABAQUS, ANSYS와 같은 유한요소법에 기반을 둔 CAE 소프트웨어가 개발되어 산업현장에 널리 보급되어 있으며, 정적해석, 동적해석, 진동해석, 충돌해석 등 해석목적에 맞게 모듈화가 되어있다. 최근에는 해석알고리즘 및 컴퓨터성능의 발달에 힘입어 다중물리해석, 최적설계와 같은 난해하며 높은 계산량을 요구하는 문제의 적용과 및 다자유도문제의 해결이 진행되고 있는 추세이다. 본 논문에서는 항공우주산업분야에 주로 사용되는 구조해석 소프트웨어의 최신기술동향을 살펴본다. Computer Aided Engineering(CAE) technology as well as Design(CAD) and Manufacturing(CAM) have been widely adopted in the aerospace industry in order to develop the structure of airplanes, satellites and launch vehicles. Among them, CAE softwares based on finite element methods such as NASTRAN, ABAQUS and ANSYS have gained many engineers' interest in various industries such as automobiles, civils, aircraft and spacecraft. The softwares usually consist of several modules: Static, Dynamic, Vibration, Impact etc. that make analysis specific to meet the design goals of the structure systems. Recent enhancement in the computer hardwares and numerical algorithms enables us to perform complex analysis like multi-physics, optimum design. Also, they make it possible to deal with a large scale problem easily. This paper reviews structural analysis softwares in aerospace industry and gives a summary on its recent development.
국부적 비주기성을 갖는 이종재료의 해석을 위한 다절점 유한요소를 이용한 다중스케일 해석기법
임재혁(Jae Hyuk Lim),손동우(Dongwoo Sohn),임세영(Seyoung Im) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
We present a new multiscale method for locally-nonperiodic heterogeneous materials. By decomposing them into periodic part and nonperiodic part, multiscale finite element model is constructed in a straightforward manner. The periodic part is appropriately coarse-grained through homogenization process and the nonperiodic part is retained to capture the localizing phenomena of materials. For seamless transition from coarse scale meshes to fine scale meshes, we replace some elements consisting of the periodic part, in the vicinity of the nonperiodic part, by homogenized variable-node finite elements. To demonstrate the performance of the proposed method, several examples involving defects embedded in composite materials are given. It is shown that the proposed method have outstanding advantages over fully fine scale analysis in terms of computational costs without losing its accuracy.