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RISS 인기검색어
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- 저자 : 이형식(Hyong-Sik Lee) (검색결과 7 건)
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이형식(Hyong-Sik Lee),방흥석(Heung-Sug Bang),지성근(Sung-Keun Ji) 산업기술교육훈련학회 2011 산업기술연구논문지 (JITR) Vol.16 No.1
In this study, Bingham Properties of ER(Electro-Rheological) fluids are experimentally investigated at various temperatures. Especially the viscometer is made in order to measure the effects of temperature. As for the ER fluid to be tested, five types of ER fluids are employed; soluble-gum arabic based ER fluid, an ER fluid of Shokubai, an ER fluid of Loctite, A type fluid and B type ER fluid of Bayer. The first one is composed in-housingly. The Bingham properties of ER fluids is including the dynamic yield stress and the current density. And these prosperities are measured by increasing the electric field from zero to maximum voltage in 25℃, 70℃ and 100℃. Consequently, the yield stress and the current density of the ER fluids are obtained and compared at different temperatures.
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ER유체의 빙햄특성 측정을 위한 측정기의 설계변수에 관한 연구
이형식(Hyong-Sik Lee),방흥석(Heung-Sug Bang),지성근(Sung-Keun Ji) 산업기술교육훈련학회 2011 산업기술연구논문지 (JITR) Vol.16 No.2
In this study, the shear mode measuring devices which is used in general applications of ER fluid is proposed and Bingham Properties of ER(Electro-Rheological) fluid depended on various electrode shapes and materials is measured. Shear forces depended on radius variations is measured similarly. When the torque of ER fluid which is measured is same, the shear stress shows the size which is identical. The case where the torque which is measured will be same, the shear stress is of one size whether the gap of electrodes is changed. As a result of experiment, shear stress is increased with increasing shear rate. Also Bingham Property is increased with increasing electrical field strength. The experimental results by the proposed equipment is almost same with the conventional equipment by increasing electrode radius. ER effects is increased with the decreasing of the electrode gap.
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STS 316L 스테인리스강의 미세 드릴가공 특성에 관한 연구
이형식(Hyong-Sik Lee) 산업기술교육훈련학회 2013 산업기술연구논문지 (JITR) Vol.18 No.4
In this research, to the effort reaching the needed processing shape and preciseness, I suggest cutting feature data about STS 316L stainless steel, when you perform micro-drilling with machining center, using solid tungsten carbide drill(∅0.15). There are the cutting conditions, which I found the changes of Thrust and Torque in accordance with, to restrain the built-up edge occurrence when you process micro drilling, to maintain the shape of optimize chip, and to get a fine surface roughness inside of drill hole. I also try applying them in a real spinneret processing to see possibilities to make them better.
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장우영(Woo-Young Jang),이형식(Hyong-Sik Lee) 산업기술교육훈련학회 2011 산업기술연구논문지 (JITR) Vol.16 No.4
MR fluid is widely used in many kinds of actuators because of its good controllability. The damping characteristic of the MR brake is controllable by varying the magnetic field around the fluid. In this paper, a MR brake is designed and analyzed using FE analysis. Under consideration of spatial limitation, design parameters are determined to maximize to torque using finite element method. The FE analysis is performed using a commercial code, ANSYS workbench. he proposed brake device is manufactured, and its field-dependant torque is experimentally evaluated. When the electric current increases, the torque of the MR fluid brake is increased and the response time of MR fluid brake is very fast. Depending on the strength of the current supply, torques of the MR fluid brake also increases.
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전우청(Woo-Cheong Jeon),이형식(Hyong-Sik Lee) 산업기술교육훈련학회 2011 산업기술연구논문지 (JITR) Vol.16 No.4
This experimental study presents Bingham properties under the flow mode. Among working modes of ER fluids the flow mode is considered in this study. In order to undertake this work, a flow mode type electro-viscometer is manufactured. The experimental setup is similar to the ER damper which is operated by the double-rod hydraulic cylinder. The electrode gap is chosen by 1.00㎜. The pressure drops in the viscometer are measured by two pressure sensors at each end of the electrode. The yield stresses are then obtained through analytical procedures. As for the ER fluid to be tested, two types of ER fluids are employed; soluble-arabic gum based ER fluid(I3S50), an ER fluid of Bayer. The first one is composed in-housingly. The pressure drops of ER fluids are measured by increasing the electric field from zero to maximum voltage in room temperature. Consequently, the yield stresses of the ER fluids are obtained. The significant factor of Bingham properties, ?? and ?? values, of all ER fluid in the flow mode appeared to be greater than that in the shear mode, exclusive of soluble-arabic gum based ER fluid. Therefore, the Bingham model applied to the application of flow-mode type of device, the results obtained from the flow-mode type of experiment should be used.
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박종현(Park-Jong Hyun),임한선(Han-Sun Lim),이형식(Hyong-Sik Lee) 한국구매조달학회 2007 한국구매조달학회지 Vol.6 No.1
본 논문의 목적은 국내 공공 건설공사 발주제도의 개선방향을 제시하는데 있다. 이를 위하여 본 연구에서는 우리나라와 선진국의 정부공사제도의 현황과 실태 그리고 혁신 움직임 등을 검토하여 과거의 가격경쟁을 근간으로 하는 정부공사제도를 기술경쟁을 가미하여 혁신적인 제도로 개선하는 방안을 제시하였다. 그리고 이를 달성하기 위한 방안으로 최저가(Low Bid)낙찰방식 이나 적격심사 낙찰방식에서 벗어나서 가격과 기술을 동시에 경쟁하도록 함으로써 건설산업의 기술력을 최대한 활용하여 공공시설물과 건축물의 가치를 극대화하는 최고가치(Best Value)낙찰제도나 기술만으로 경쟁하는 기술경쟁위주(Qualifications Based Selection)낙찰방식 등을 도입할 것을 제안하였으며, 또한, 합리적이고 과학적인 기술평가체계의 구축, 공정하고 투명한 경쟁을 유도하는 방안 등을 제시하였다. This research aims to suggest the direction of improving the regulation of public procurement in Korea. For this purpose, research was based on studies by materials of construction contracts regulations in Korea, USA, UK and Japan. Based on these materials, this study recommend to change the awarding system from the price based competition to the technology based competition. And also suggest how to achieving this goal. The recommendations are followings. These are to develop an evaluation system of the technical capacity of bidders, to introduce a best value based selection system or qualifications based selection system and etc. Also recommend how to be guaranteed more fairness and transparency in the competition procedures.
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鄭準基,李炯植 연세대학교 산업기술연구소 1981 논문집 Vol.13 No.2
The phenomenon of chatter is a violent relative vibration between workpiece and tool in machining of metals, and is an important limiting factor of production rate and surface quality, and also reduces the life of machine-tool and tool. In this study, for the prevention of chatter, the tendency of vibration of cutting force and horizontal deflection of workpiece at the chatter occurring point was observed, and some methods to determine the chatter occurring point were suggested, and by these methods, the maximum chatter free length of cantilever type workpiece in lathe was determined according to the variation of workpiece diameter and cutting depth.
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