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금속 와이어의 무구속 열간 인발 특성 -스테인레스강 와이어와 구리 와이어-
하보근,김종성,백영남,허유,Ha, Bo-Keun,Kim, Jong-Seong,Paik, Young-Nam,Huh, You 한국섬유공학회 2010 한국섬유공학회지 Vol.47 No.5
Micro-sized metal fibers are suitable for multi-functional and high performance industrial components, but the fiber manufacturing process relies heavily on wire drawing with dies, which can cause die-raw material friction. An alternative for the efficient production of the metal fibers is to use dieless wire drawing technology. This paper reports the characteristic differences of the dieless wire drawing process, which relies on forced necking. The hot working principle was applied to the most frequently used raw materials, stainless steel and copper, while a microwave furnace and susceptor were employed. The experimental trials showed that stainless steel wires could be more advantageous in dieless drawing than copper wires in that the necking of the stainless steel wire took place in a narrower zone than copper. Furthermore, a mathematical model was set up considering volume heating and wire cooling and combining the temperature effect of viscosity in Arrhenius form with the plastic deformation in Bingham form. The model showed good agreement with the experiments when the process was carried out in a steady state at various draw ratios and process speeds. These results suggest that the theoretical model can depict the real process quite well.
비틀림 흡수구조형 제륜자 홀더행거의 적용방안에 관한 연구
홍재성(Hong Jai-Sung),함영삼(Ham Young-Sam),백영남(Paik Young-Nam) 한국철도학회 2004 한국철도학회 학술발표대회논문집 Vol.- No.-
Among welded structure bogies in use for high speed freight car, a part of bogies manufactured in 1999 and 2000 have found problems that crack occurs in its end beam. In case of a freight car the difference of weight between empty and loading conditions are worse than in case of a passenger car. Moreover its brake system is tread brake without second suspension system. Cracks of end beam is supposed to be due to loading by brake system rather than vertical loading by freight. These cracks can make brake system useless and may be a cause of derailment in the worst case. In this study, we have proposed a simple torsion-free brake shoe holder hanger to remove torsion of hanger bracket which was supposed to be one of causes of cracks and performed finite element analyses. Also static load test was applied in torsion free brake shoe holder.
벌크시멘트화차의 대차 하중시험과 진동성능시험 및 동특성 해석 연구
홍재성(Jai-Sung Hong),함영삼(Young-Sam Ham),백영남(Young-Nam Paik) 한국철도학회 2003 철도저널 Vol.6 No.3
The object of this study is to ensure the stability of bulk cement cars conducting vibration performance test, dynamic characteristic analysis and static load test of bogie frame. In case of static load test, bogie static load test facility was used. In case of dynamic characteristic analysis, Vampire Software was used. In case of vibration performance test, real bulk cement cars were used in kyeung-bu line. In the results of static load test of bogie frame for bulk cement car, all structures satisfied allowable stress criteria of materials. The vibration performance test and dynamic characteristic analysis results satisfied allowable standards.
극저온 볼 밀링을 통한 Ibuprofen 분말의 마이크로화
조현갑(Hyun Kab Cho),이경엽(Kyong Yop Rhee),백영남(Young Nam Paik),박훈재(Hoon Jae Park),이상목(Sang Mok Lee) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.11
For the present study, the cryogenic ball milling process was applied to make Ibuprofen microsized. The cryogenic ball milling was performed at low temperature of about -180℃ for 6 hours. The particle size distribution was determined before and after the cryogenic process. X-ray diffraction (XRD) measurement was made to determine the effect of cryogenic process on the crystallinity of Ibuprofen. The results showed that the size of Ibuprofen was reduced about 10 times by the cryogenic process. The degree of crystallinity of Ibuprofen was slightly reduced by the cryogenic process.
허유(You Huh),김승훈(Seung Hoon Kim),김인석(Ihn Seok Kim),백영남(Young Nam Paik) Korean Society for Precision Engineering 2007 한국정밀공학회지 Vol.24 No.7
In modern industries, materials are required that possess multi-functional properties and at the same time flexibility in their shapes with structural stability. The major technology realizing this requirement consists of thinning metal wires and laying them with stable contact nodes. This research has dealt with a new method to manufacture thin wires by drawing without applying dies, but with introducing enforced necking, which enables to process multi-ends. Based on the new method, the process dynamics was modelled and its steady-state characteristics were analyzed. Results showed that the profiles of the material velocity in the drawing zone increased with a downward convex shape, while the cross-sectional area decreased with the shape of upward convex. The microwave heating turned out to be effective in wire drawing, but dependent on the input feeding direction. The variation in the diameters of the drawn wires was negatively affected by increasing the drawing ratio.
Graphite/Epoxy 적층복합재의 층간파괴 향상을 위한 프리프레그의 전처리 연구
김민호(Min Ho Kim),이경엽(Kyong Yop Rhee),백영남(Young Nam Paik),김현주(Hyeon Ju Kim),정동호(Dong Ho Jung) Korean Society for Precision Engineering 2006 한국정밀공학회지 Vol.23 No.10
In this study, the graphite/epoxy prepregs were surface-treated using oxygen plasma, and optimal treatment time was determined measuring the contact angle on the prepreg surface. Interlaminar fracture behavior of surface-treated graphite/epoxy composites was compared with that of regular (untreated) graphite/epoxy composites. The results showed that the contact angle was a minimum when treated for 30 minutes. The interlaminar fracture toughness of surface-treated specimen was improved about 15% compared with that of regular specimen.