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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.
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.
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.
고주파 열처리에 따른 SPS5 강의 마모특성 변화에 대한 연구
김민호(Min Ho Kim),이경엽(Kyong Yop Rhee),백영남(Young Nam Paik),홍재성(Jai Sung Hong),함영삼(Young Sam Ham) Korean Society for Precision Engineering 2006 한국정밀공학회지 Vol.23 No.10
In this study, the tempering effect on the wear characteristics of induction-hardened SPS5 steel was investigated. For this purpose, three tempering conditions were applied to control the hardness of heat-treated SPS5 steel. Ball-on-disk wear tests have been performed using zircornia balls on the tempered specimens to determine the variation of wear characteristics. The results showed that friction coefficient decreased with increasing hardness for induction hardening conditions. This seems to occur because real contact area between specimen and mating ball was affected by the specimen hardness.
김기주(Kee Joo Kim),신광선(Kwang Seon Shin),정효태(Hyo-Tae Jeong),백영남(Young-Nam Paik) 한국자동차공학회 2005 한국 자동차공학회논문집 Vol.13 No.6
In order to fabricate the aluminum alloys with good drawability, the textures evolution of the AA5182 sheets after rolling and annealing was studied. The measurement of the deformation textures was carried out for the sheets which were cold rolled with high reduction ratio by using the symmetric roll. In addition, the change of the recrystallization texture was investigated after heat-treatments of the rolled sheets with various heat treatment conditions. Rolling without lubrication and subsequent annealing led to the formation of favorable rot-C_(ND) {001}<110> and γ-fiber ND//<111> textures in AA5182 sheets. From the results, the γ-fiber ND//<111> component well evolved during rolling at highest reduction ratio (over 90%, l/d parameter of 6.77). Among shear deformation textures, the γ-fiber ND//<111> was not rotated in holding time of 180~7,200 seconds at 350°C. The Monte-Carlo technique was used and could be representatively simulated these textures evolution during recrystallization.
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.