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주조 잉고트의 코깅공정시 기공압착 분석을 위한 유한요소해석
권용철(Y.C. Kwon),이정환(J.H. Lee),이승욱(S.W. Lee),정용수(Y.S. Jeong),김남수(N.S. Kim),이영선(Y.S. Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
In the steel industry, there is a need to produce large forged parts for the automobile industries, the flight and shipping industries and military industries. In many steel-industry application, a cogging technique for cast ingots is required, because the major parts are needed as one large body in order to obtain higher quality. Therefore, cogging is the primary step in manufacturing of practically large open-die forging. In the cogging process, internal voids have to be eliminated as defects, The present work is concerned with the elimination of the internal voids in large ingots so as to obtain sound products. In this study, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperatures and strain rates. The FEM analysis are performed to investigate the overlap defect of cast ingots from the first ingot to bloom. Also the analysis of void closure are performed by using the DEFORM™ -3D.
나종주(J.J.Rha),황윤철(Y.C.Hwang),정용수(Y.S.Jeong),문성모(S.M.Moon),안계혁(K.H.An) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Lotus leaf displays self cleaning effect. Because the contact angle of water is higher than 140°, water droplets roll easily on the lotus leaf. Rolling water droplets sweep off dusts or contaminants on lotus leaf. Self cleaning effects come from hydrophobicity and rough surface. In order to imitate lotus leaf, PTFE(Polytetraflouroethylene) sputtered in vacuum, CNTs(Carbon Nano Tubes) grown with different densities and replica of AAO(Aluminium Anodic Oxide) template are fabricated. Measured contact angles are 150°, 154° and 135° respectively. These results are analyzed with Wenzel's theory for homogeneous surface and Cassie and Baxters's theory for heterogeneous surface.
권해웅,김성갑,정용수 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.4
Magnetic field influences the electrodeposition of ferromagnetic metals into the pores of anodic film. In this study, the magnetic properties and morphology of the anodic film deposited with Fe or Co were examined, and a particular emphasis was placed on the effect of magnetic field on the crystallographic orientation of the deposited crystals. In the case of Fe-deposited anodic film the intrinsic coercivity was not influenced significantly by the magnetic field, and no preferred orientation of the deposited crystals was observed regardless of the application of magnetic field. On the other hand, the coercivity and the crystallographic orientation in Co-deposited film were significantly influenced by magnetic field. Co crystals in the film deposited even in absence of magnetic field showed preferred orientation to some extent, in which c-axis of the deposited Co crystals was more or less parallel to the electric field. This preferred orientation was further enhanced by the application of magnetic field, and his was closely related the enhancement of coercivity.
질소이온주입에 따른 생체안전성 티타늄 임플란트의 마모특성
변응선,최종운,손선희,정용수 한국산업안전학회 1999 한국안전학회지 Vol.14 No.4
In this study, plasma source ion implantation was used to improve the wear properties of biocompatible titanium implant. In order to observe the effect of ion energy and dose on wear property of titanium implant, pin-on-disk type wear tests in Hank's solution were carried out. The friction coefficient of ion implanted specimens were increased from 0.47 to 0.65 under high energy and ion dose conditions. As increasing ion energy and ion dose, the amount of wear was reduced.