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Cu-Zn-Al 형상기억 합금의 열사이클에 따른 집합조직의 변화에 관한 연구
홍대원,박영구 ( D . W . Hong,Y . K . Park ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.3
The shape memory effect results from the martensite transformation of each individual grain. Thus it is necessary to study the texture and its variation. In this study the change of texture during thermal cycling and it`s effect on shape memory ability are investigated. The major component of the rolling texture in the parent phase is identified (001)[110], and minor components are (112)[110], (111)[112]. {hkl}<100> fiber texture is developed at 45° from rolling direction. In the case of martensite phase, it is estimated that the major component is (011)[100] and the minor components are (105)[501], (010)[101] and (100)[001]. According to thermal cycling, severity of texture, especially (001)[110] component in parent phase and (011)[100] component in martensite phase are increased. The shape memory ability is increased with increase of thermal cycles and also increased as the direction of specimen approach to 45° from rolling direction. After first thermal cycling the temperature of transformation can be define clearly and Ms and As are raised by thermal cycling.
Ni3Al 금속간 화합물의 압연변형 및 우선방위에 관한 연구
홍대원,박영구 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.5
The Purpose of this study is to investigate the rolling deformation and preferred orientation for Ni₃Al intermetallic compounds. The chemical compositions of the alloys used in this study are 75.7Ni-24Al-0.3B(Al alloy) and 78.8Ni-21Al-0.2B(A2 alloy). The preferred orientation has been characterized by plotting inverse pole figures and pole figures. The preferred orientations of Al alloy after cold rolling, are {110} $lt;111$gt; and {110} $lt;211$gt;, whereas A2 alloy has brass type orientation of {110} $lt;211$gt;. This alloy could be cold rolled soundly to 80% reduction without intermediate annealing. The microstructure of A2 alloy consists of the ordered γ´cells surrounded by disordered γ phases. Also dislocations were concentrated in the γ phase near the of γ´/γ interface. The improved workability of this alloy may be due to the γ phase located at Ni₃Al interface, which alleviates the grain boundary embrittlement.
RC 구조물의 균열 보수용 폴리머 시멘트 복합체의 점도와 유동성에 관한 연구
홍대원 ( Hong¸ Dae-won ),김상혁 ( Kim¸ Sang-hyuk ),권우찬 ( Kwon¸ Woo-chan ),조영국 ( Jo¸ Young-kug ) 한국건축시공학회 2021 한국건축시공학회 학술발표대회 논문집 Vol.21 No.2
The purpose of this study is to evaluate the viscosity and flowability of polymer-cement composites for repairing cracks of RC structures. The viscosity and flowability of the polymer cement composites differed greatly depending on the type of polymer and the polymer cement ratio, and the polymer cement composites could be produced that could repair fine cracks in the RC structure without material separation by adjusting the proper water-cement ratio. In particular, the mixing of high viscosity EVA-modified polymer composites could be adjusted.
윤광준,홍대원,박정근,강태삼 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4
건물 옥상이나 자동차와 선박 지붕에서 멀티콥터가 자동으로 수직이착륙하며 임무를 수행하는 시스템을 개발하기 위해서는, 기반 착륙 장치에 정확한 자동 착륙 기술을 필요로 한다. 이를 위해 DGPS와 AHRS센서를 연동하여 기체와 기반 착륙장치의 정확한 위치를 확인하고, 기체의 제어 컴퓨터가 위치를 인지하게 하는 것이 선행되어야 한다. 실제 장비를 구성한 시스템 실험에서 센서에서 감지한 기체의 위치좌표와 Heading 방향이 실제 임무에서 사용 가능 할 정도로 정확한 성능을 보여주었다. To develop a multi-copter that can operate its own mission and return to landing station on the roof of building, automobile and ship automatically, precise landing technology to land on the base landing station is required. To do this mission, FCC(Flight Control Computer) must verify precise position values of the mulitcopter and landing station using AHRS aided DGPS. Experimental test with the designed device shows suitable values of position and heading direction which can be used at real flight operation.