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디지털 이미지를 이용한 알루미늄 원판의 열좌굴 현상 계측
구남서,김태렬 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.4
본 연구에서는 디지털 영상 상관 기법을 이용하여 티타늄 링 안에 놓여 있는 알루미늄 원판의 열좌굴 현상을 계측하였다. 알루미늄 열팽창계수가 티타늄의 열팽창계수보다 크기 때문에 알루미늄 원판은 온도가 상승하면서 일정한 온도에서 좌굴하게 된다. 구조물은 25℃부터 160℃ 까지 1℃/분의 속도로 가열하였으며 가열하는 동안 구조물 표면의 3차원 영상을 촬영하였고 그 이미지로 구조물의 3차원 변형을 계측하였다. 계측 결과의 정확성을 확인하기 위하여 유한요소법을 사용하여 구조물의 변형을 해석하였으며 계측한 결과와 해석한 결과가 일치한다는 것을 확인하였다. In this study, we investigated the thermal buckling behavior of a circular aluminum plate which is mounted in a titanium ring using a digital image correlation (DIC) technique. Due to the differences in the coefficients of thermal expansion (CTEs) between aluminum and titanium, the aluminum plate buckles at a certain temperature. We heated the structure from 25℃ up to 160℃ at 1℃/min heating rate. At the same time. we captured images of the structure to calculate the displacement using DIC. In order to verify the proposed measurement method. a finite element analysis of the structure was performed using ABAQUS software. The results of the DIC-based measurement and finite element analysis were found in good agreement.
구남서,레반르엉,안용산,유웅렬,황진옥,박종규 한국항공우주학회 2017 韓國航空宇宙學會誌 Vol.45 No.12
In this study, we performed the deployment test of shape memory polymer specimens for space antenna design. Poly(cyclootene) was cross-linked by dicumyl peroxide to make a PCO shape memory polymer. A miniature specimen with 120 mm diameter for a deployable antenna was fabricated with the PCO shape memory polymer. To investigate the deployment performance, the folded specimen as a temporary shape was heated by two heaters to the 15 ℃ higher temperature than the glass transition temperature of shape memory polymer. Firstly, the specimen was installed horizontally and tested. The deploying motion was captured by a digital camera and analyzed by a Tracker program. To reduce the effects of gravity, the specimen was installed vertically and tested again. The deployment performance of a shape memory polymer was investigated by comparing the results of horizontal and vertical installation tests. 본 연구에서는 우주 안테나 설계용 형상기억 폴리머 시편의 전개 시험을 수행하였다. Poly(cyclooctene)을 dicumyl peroxide를 이용하여 가교시켜 PCO 형상기억 폴리머를 제조하고, 이를 이용하여 지름이 120 mm인 전개형 안테나의 축소 모델을 제작하였다. 전개 성능 시험을 위하여 원형 형태의 형상기억 폴리머 시편을 반으로 접어 임시 형상을 만든 후 두 개의 히터로 형상기억 폴리머의 유리 전이 온도보다 15℃ 높은 온도로 시편을 가열하였다. 먼저 시편을 수평 설치하여 전개 실험을 수행하였다. 시편의 전개 영상을 디지털 카메라를 사용하여 촬영한 후 트래커 프로그램을 이용하여 분석하였다. 중력의 효과를 최소화하기 위하여 수직 설치하여 다시 실험을 수행하였다. 두 실험의 결과를 비교하여 형상기억 폴리머 시편의 전개 성능을 고찰하였다.
곡면형 비대칭 압전복합재료 작동기 LIPCA의 설계해석/제작/성능평가
구남서,신석준,박훈철,윤광준,Gu, Nam-Seo,Sin, Seok-Jun,Park, Hun-Cheol,Yun, Gwang-Jun 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.10
This paper is concerned with design, manufacturing and performance test of LIPCA ( Lightweight Piezo- composite Curved Actuator) using a top carbon fiber composite layer with near -zero CTE(coefficient of thermal expansion), a middle PZT ceramic wafer and a bottom glass/epoxy layer with high CTE. The main point of this design is to replace the heavy metal layers of THUNDER by thigh tweight fiber reinforced plastic layers without losing capabilities to generate high force and large displacement. It is possible to save weight up to about 30% if we replace the metallic backing material by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a graphite/epoxy prepreg were simply stacked and cured at an elevated temperature (177 $^{circ}C$ after following an autoclave bagging process. It was found that the manufactured composite laminate device had a sufficient curvature after detached from a flat mold. The analysis method of the cure curvature of LIPCA using the classical lamination theory is presented. The predicted curvatures are fairly in agreement with the experimental ones. In order to investigate the merits of LIPCA, a performance test of both LIPCA and THUNDE$^{TM}$ were conducted under the same boundary conditions. From the experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDERT$^{TM}$.