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복합재료 와이어로 제작된 semi-WBK 의 전단 강도 예측 및 평가
강기주(Ki-Ju Kang),이기원(Ki-Won Lee),이병철(Byung-Chul Lee),변준형(Jun-Hyeung Byeun) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Over the last decade, truss type cellular metals attract attention because of their strength per unit weight and potential of multi-functional using the inner space. Wire-woven Bulk Kagome(WBK) is a candidate for mass-producible and multi layered cores with Kagome truss structures. Recently, a new truss core of fiber reinforced plastic was introduced. As its name, semi-WBK, hints, the structure is similar to WBK. Mechanical behavior of compression on semi-WBK was reported. In this work, we predicted theoretical shear strength of semi-WBK and performed the experiment for verification.
강기주(Ki-Ju Kang),임상채(Sang Chai Lim),이상신(Sang Shin Lee),전문창(Moon Chang Jeon),주재황(Jae Hwang Joo) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Recently, the authors have developed a new material test system for thin film at the high temperature. It is so compact and precise with sub micron resolution that it seems to be a useful tool for research of the oxide film growth, its mechanical behavior and failure mechanism. To this end, in this paper three methologies are described for in-situ monitoring of the displacement & strain and the temperature, the oxide thickness. These are the Laser Speckle analysis with digital image correlation technique, the two-color infra-red thermometer und the laser reflection interferometry respectively. The calibration results and some issues which should be addressed for practical application are presented.
압축하중을 받는 WBK의 기계적 거동에 대한 방향 의존성
강기주(Ki-Ju Kang),김판수(Pan-Su Kim),허해규(Hae-Kyu Hur) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Wire-woven Bulk Kagome (WBK) is fabricated by assembling metallic wires spatially formed in the three-dimensional directions, and the WBK assembly is uniformly composed of a number of twisted wires. To get a better understanding of WBK structures and their mechanical characteristics, the concepts of WBK unit cell/sub-unit cell are introduced. And also several geometrical parameters based on a WBK unit cell are suggested to get the three-dimensional volume. By using the WBK unit cells, the orientation dependency on the mechanical behavior of WBK assemblies under compression is investigated theoretically. The strength, elastic modulus and failure mechanism of WBK structures are analyzed under various directions of loading. Finally, a good agreement between the present results and the available data is suggested.
마이크로 및 나노 박막의 잔류응력을 측정하기 위한 새로운 방법
강기주(Ki-Ju Kang),Anthony G. Evans 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
A new method to measure residual stress in micron and nano scale films is described. In the theory it is<br/> based on Linear Elastic Fracture Mechanics. And in the techniques it depends on the combined capability of<br/> the focused ion beam (FIB) imaging system and of high-resolution digital image correlation (DIC) software.<br/> The method can be used for any film material (whether amorphous or crystalline) without thinning the<br/> substrate. In the method, a region of the film surface is highlighted and scanning electron images of that<br/> region taken before and after a long slot, depth a, is introduced using the FIB. The DIC software evaluates the<br/> displacement of the surface normal to the slot due to the stress relaxation by using features on the film surface.<br/> To minimize the influence of signal noise and rigid body movement, not a few, but all of the measure<br/> displacements are used for determining the real residual stress. The accuracy of the method has been assessed<br/> by performing measurements on a nano film of diamond like carbon (DLC) on glass substrate and on micro<br/> film of aluminum oxide thermally grown on Fecrally substrate. It is shown that the new method determines<br/> the residual stress R σ =-1.73 GPa for DLC and R σ =-5.45 GPa for the aluminum oxide, which agree quite<br/> well with ones measured independently.
이기원(Ki Won Lee),강기주(Ki-Ju Kang) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.4
기존의 WBK(와이어 직조 카고메)의 기계적 강도와 강성은 WBK를 구성하는 요소가 반듯하다는 가정 아래에서 계산되었다. 실제 WBK의 요소는 3차원 나선형상을 이루고 있어 계산된 이론 해와 실험 결과값과 차이를 보인다. 이번 연구에서는 정확한 WBK의 기계적 강도와 강성을 위해 하나의 트러스 요소의 굴곡 효과와 브레이징 접합 부를 고려하여 계산하였다. 또한 예측한 이론 해의 검증을 위한 경계주기조건(PBC) 유한요소해석을 수행하여 실험 결과값과 비교 분석하였다. Since the mechanical strength and stiffness of WBK have been theoretically estimated on basis of assumption that WBK is composed of straight struts, the analytic solutions sometimes give substantial errors compared with experimental. Consequently, the struts of the WBK are curved, which resulted in errors in estimation based on the previous analytic solution. In this work, to predict the mechanical properties about WBK accurately, the effect of waviness and brazing paπ are taken into account to estimate the strength and the stiffness of WBK. The results are compared with those measured by experimental and estimated by finite element analysis conducted on a unit cell under periodic boundary conditions.
이기원(Ki Won Lee),강기주(Ki-Ju Kang) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.9
기존의 WBK(와이어 직조 카고메)의 기계적 강도와 강성은 WBK 를 구성하는 요소가 반듯하다는 가정 아래에서 계산되었다. 실제 WBK 의 요소는 3 차원 나선형상을 이루고 있어 계산된 이론 해와 실험 결과값과 차이를 보인다. 이번 연구에서는 정확한 WBK 의 기계적 강도와 강성을 위해 하나의 트러스 요소의 굴곡 효과와 브레이징 접합 부를 고려하여 계산하였다. 또한 예측한 이론 해의 검증을 위한 경계주기조건(PBC) 유한요소해석을 수행하여 실험 결과값과 비교 분석하였다. Since the mechanical strength and stiffness of wire-woven bulk Kagome (BK) have been theoretically estimated by assuming that WBK is composed of straight struts, the analytical solutions occasionally give substantial errors as compared with the experimental results. The struts of WBK are helically formed, which results in errors in the estimations In this study, for accurately predicting the mechanical properties of WBK, the effects of waviness and brazed part are taken into account for estimating the strength and stiffness of WBK. The results are compared with the measured experimental results and the results estimated by a finite element analysis performed on a unit cell under periodic boundary conditions (PBC).