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프레넬 렌즈 성형에서 tip radius가 광학 성능에 미치는 영향
심종명(Jongmyeong Shim),김호관(Hokwan Kim),김중억(Joongeok Kim),명호(Ho Myung),김명연(Myungyon Kim),강신일(Shinill Kang) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
This paper describes the effect of tip radius on optical performance for fabricating Fresnel lens. We firstly designed Fresnel lens for uniform light distribution by backward design method and energy compensation method. To verify the effect of tip radius, simulation was conducted varying lens tip radius. Designed Fresnel lenses were replicated by UV imprinting and injection molding process using metal mold fabricated by direct machining. Lens profile fabricated by each process and optical performance with each fabricated lens were measured. We compared the results with simulation data, and analyzed the effect of tip radius.
Al6061 합금의 열간 압출공정에서 금형 냉각시스템에 의한 압출재의 결정립 성장 제어
고대훈(Daehoon K),이상호(Sangho Lee),고대철(Daecheol K),김호관(Hokwan Kim),김병민(Byungmin Kim) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.7
In this study, die cooling system using the nitrogen gas has been applied to hot aluminum extrusion process for refining grains and reducing of grain growth. Computational fluid dynamics(CFD) has been carried out to evaluate die cooling effect by nitrogen gas, and the results of CFD have been used to FEsimulation for the prediction of the extrudate temperature in hot extrusion process. Experimental hot extrusion has been performed to observe microstructure and to measure temperature of extrudate. The results of FESimulation have been good agreement with those of experiment. Finally, process condition of hot extrusion can be established to reduce grain growth of Al6061 through the experiment.
개폐 시 최소 간섭을 갖는 버터플라이 밸브 다시크의 설계
최영(Young Choi),부광석(Kwangsuk Boo),여홍태(Hongtae Yeo),허관도(Kwando Hur),김호관(Hokwan Kim) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.12
In this study, the design and analysis of a butterfly valve disk was performed to minimize the rubbing between the disk and the seat at opening and closing. The butterfly valve has double eccentric structure and the contact surface between the disk and the seat is a conical surface. At the instant of opening and closing the valve by the rotation of disk, the positions of zero contact point are changed. Also, if the cone surface is cut in the perpendicular direction to the rotation axis of the valve, the contour of cutting section is hyperbolic. Therefore minimum distance between the origin of the eccentric axis and the hyperbolic curve goes to the position of zero contact point. In order to consider the interferences between the disk and the seat, the thermal-structure coupled field analysis was performed by ANSYS.