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Squeeze Cast 한 Al 기지 금속복합재료의 응고거동
김대업,김진,박익민 ( Dae Up Kim,Jin Kim,Ik Min Park ) 한국주조공학회 1991 한국주조공학회지 Vol.11 No.3
N/A The solidification behavior of the squeeze cast composites of aluminum alloys reinforced with boron fiber(100㎛) and silicon carbide fibers(140㎛ and 15㎛) were investigated. Al-4.5wt%Cu and Al- l0wt%Mg were chosen for the matrix phase of the composites. In the squeeze cast specimen with high thermal difference between fiber and melt, the average secondary dendrite arm spacing(DAS) in reinforced alloy is smaller than that in unreinforced alloy. It was also observed that primary α and non-equilibrium eutectic, which seems to be penetrated and solidified at the final stage of the solidification of the matrix, are irregularly distributed around fibers. It is considered that cold fibers serve as heterogeneous nucleation site. While in the remelted and resolidified specimen without temperature difference, the DAS was not changed with reinforcement and microstructure reveals non-equilibrium eutectic with relatively uniform thickness around fibers. It might be evident the nucleation starts at interfiber region. Microsegregation decreases with the decrease in cooling rate and with reinforcement in the as-squeeze cast specimen. Al-10wt%Mg alloy shows less microsegregation than Al-4.5wt%Cu alloy.
방전 플라즈마에 의한 마찰교반공정 툴용 WC-3 wt% (Ni, Fe) 소결체의 미세조직 및 기계적특성
김대업 ( Dae-up Kim ),최영 ( Young Choi ),강봉용 ( Bong-yong Kang ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.3
In this study, the microstructure and mechanical characteristics of WC-3 wt% Ni and WC-3 wt% Fe hard materials by spark plasma sintering (SPS) for friction stir-processing tool applications were evaluated. Sintered bodies with a diameter of 66 mm were fabricated with a relative density up to 99% after the simultaneous application of a pressure level of 60 MPa and electric current for 35 min mostly without grain growth during sintering. Only the initial phase existed in the initial powers and in the ball-milled powders, but the phases of W2C and WC1-x in all sintered bodies appeared after the sintering process. The Vickers hardness and fracture toughness of the WC-3 wt% Ni hard material were approximately 2,240 kg/mm2 and 9.1MPa·m1/2, respectively, while those of the WC-3 wt% Fe sintered body were correspondingly 2,242 kg/mm2 and 6.8 MPa·m1/2.
사물인터넷 시대의 생체인식 스마트 센서 기술과 연구 동향
김광석,김대업,Kim, Kwang-Seok,Kim, Dae Up 한국마이크로전자및패키징학회 2016 마이크로전자 및 패키징학회지 Vol.23 No.2
With the pace of rapid innovation in technology of IoT (Internet of Things) and smart devices, biometric technology becomes one of the most progressive industries. Recent trends in biometrics show most are focused on embedding biometric sensors in mobile devices for user authentication. Multifactor biometrics such as fingerprint, retina, voice, etc. are considering as identification system to provide users with services more secured and convenient. Here we, therefore, demonstrate some major technologies and market trends of mobile biometric technology with its concerns and issues.
정기한,오재신,김대업,Chung, Ki-Han,Oh, Jae-Sin,Kim, Dae-Up 대한산업경영학회 2004 산업융합연구 Vol.2 No.2
The purpose of this study is to analyze satisfaction factors that consumers perceive during purchasing products and using services on Internet Shopping Mall. Consumers' purchase process on Internet Shopping Mall is examined by finding the relation between overall satisfaction and intention. The study results show that consumers' higher appraisal degree on satisfaction means their higher purchase intention. In the process of service encounter, many factors affect customer's evaluation for overall satisfaction. They are categorized as five factors; information provision, merchandising, ordering convenience, payment risk, after services.
CP강 전기저항점용접부의 기계적 성질에 미치는 Ti 함유량과 용접전류의 영향
공종판 ( Jong Pan Kong ),김대업 ( Dae Up Kim ),강정윤 ( Chung Yun Kang ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.4
When complex-phase (CP) steel with a tensile strength of more than 1 GPa grade is joined using resistance spot welding (RSW), the optimum Ti content should be chosen in order to satisfy the weldability and mechanical properties. Therefore, in this study, the effect of the Ti content (0~300 ppm) on the tensile- shear load of the RSW in CP steels is investigated. Because the resistivity of the base metal is independent of the Ti content, it does not affect the nugget diameter. Regardless of the Ti content, the specimens under 5t1/2 (t = sheet thickness) are fractured in the interfacial failure mode. In the low welding current condition (lower than 6.4 kA), the measured nugget diameters are smaller than the calculated critical nugget diameter regardless of the amount of Ti addition in order that the fracture mode is interfacial failure. Pull-out failure occurs at the softened zone, which is the boundary between the base metal and heat-affected zone. The tensile-shear load of the specimen failure in the pull-out mode increases as the fractured diameter and hardness of the softened zone increase. The shear load is only dependent on the fractured diameter.
조원경,조상욱,김두인,김대업,정명영,Cho, Won Kyoung,Cho, Sang Uk,Kim, Doo-In,Kim, Dae-Up,Jeong, Myung Yung 한국마이크로전자및패키징학회 2016 마이크로전자 및 패키징학회지 Vol.23 No.1
본 연구에서는 소수성 구현을 위한 표면 거칠기가 접촉각과 접촉각 이력에 미치는 영향을 평가하였다. 초발수 특성을 극대화하기 위해, 액적이 이동하기 위해 필요한 구름저항력을 제안하였으며, 이에 대한 평가를 통하여 표면에 형성한 패턴이 접촉각 이력 및 구름저항력에 큰 영향을 주는 것을 확인하였다. 초발수 특성이 요구되는 실제 응용을 위해서는 액적의 이동에 필요한 에너지를 최소화하기 위하여 접촉각을 극대화하고 동시에 접촉각 이력을 최소화하기 위한 표면 패턴 형상의 최적화가 요구됨을 확인하였다. In this study, the effects of the contact angle (CA) and contact angle hyteresis (CAH) of planar and nano-patterned surfaces on rolling resistance of water droplet were studied. Based on the investigation on the CAH of water droplet on surfaces with various static wettability, it was found that the rolling resistance coefficient of water droplet is highly influenced by the surface pattern as well as CAH. The observed results suggest that the optimal surface patterns should be designed in order to minimize the rolling resistance of water droplet for the practical applications where superhydrophocitiy is required.
600MPa급 TRIP강의 $CO_2$ 및 Nd:YAG 레이저 용접부의 특성
한태교,김성준,이봉근,김대업,강정윤,Han, Tae-Kyo,Kim, Seung-Jun,Lee, Bong-Keun,Kim, Dae-Up,Kang, Chung-Yun 대한용접접합학회 2006 대한용접·접합학회지 Vol.24 No.1
The characteristics of $CO_2$ or Nd:YAG laser welded 600MPa ade TRIP steel was investigated. He or Ar gas was used as a shield gas in case of $CO_2$ laser welding, but the shield gas was not used in case of Nd:YAG laser welding. Bead on plate welding was performed with various welding conditions. Defects in the joints of both welding type occurred at 1.8m/min but were not observed over the welding speed of 2.1m/min in case of Nd:YAG laser welding. However, porosity occurred in $CO_2$ laser welding and the tendency of decreasing with the increase of welding speed. The hardness was the highest at heat affected zone near fusion zone as well as at the fusion zone and decreased on approaching the base metal. In a perpendicular tensile test to the weld line, all specimens that have been welded at optimum conditions were fractured at the base metal, and the tensile properties showed the rather higher than those of raw material. In a parallel tensile test, the strength of the joints was higher than that of the base metal. Elongation was found to be lower than that of the raw material. Forming height by Erichsen test and elongation were deeply related with the ratio of base metal/weld metal and the maximum hardness of the weld metal. Also porosity induced to decrease the strength and the elongation. The maximum formability was recorded at approximately 80% as compared with that of the raw material with the optimum condition.