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천두만,안성훈,최정오,이선영,Isaku Kanno,Hidetoshi Kotera 한국정밀공학회 2012 International Journal of Precision Engineering and Vol.13 No.7
With increasing concerns of environmental issues in manufacturing process, energy efficient and waste free manufacturing processes have been widely studied. In the field of nano/micro manufacturing, many research results of direct writing processes such as ink jet printing, gravure printing, and rapid prototyping processes have been reported to remove wasteproducing conventional lift-off process for patterning. In addition, the use of toxic solvents such as acetone, toluene, xylene and so on has been decreased. At the same time, energy efficiency becomes one of environmental issues in manufacturing process. In this research, Nano particle deposition system (NPDS), a dry spray deposition process for fabrication of meta and ceramic direct patterning at room temperature, was introduced according to the environmental aspects. In previous studies, NPDS has shown the feasibility of the depositions of metals such as Sn and Ni, and the depositions of ceramics such as Al2O3, and TiO2 by spraying powders under low vacuum condition. The advantages of NPDS are 1) solvent free dry deposition process, 2) relatively low energy consumption with room temperature and low vacuum process condition, and 3)direct patterning process. The energy consumption in NPDS was briefly compared with similar processes including aerosol deposition and cold spray. The direct patterning results with 200μm width line pattern using micro-nozzle were fabricated without any post-processes. These results confirmed NPDS can become a solvent-free energy efficient direct patterning process for metals and ceramics.
천두만,J. C. LEE,J. C. YEO,안성훈,S. S. HONG,J. D. JANG 한국자동차공학회 2011 International journal of automotive technology Vol.12 No.2
In new slim torque converters, lock-up clutches are used to provide high fuel efficiency at low speed. However, the slimness of the converters causes difficulty in heat dissipation, which may damage the friction material and shorten its life span. A cooling hole in the lock-up piston reduces the heat but also reduces the torque because oil flows through the hole due to the pressure difference between the two faces of the piston. In the early stages of the development of this type of torque converter, designers must consider the minimum flow rate required to cool the friction material and the minimum torque capacity required to transmit the engine torque. This research explored two methods of estimating these parameters. In the first method, an estimation equation was derived by combining the response surface method with physical properties such as the centrifugal force, a sudden expansion, a sudden contraction, and the steady flow energy equation. The second method involved the use of an artificial neural network. The feasibility of the estimates based on statistics and on the artificial neural network were confirmed in the design stage by comparing experimental and estimated data. An estimation program was created using the C#.Net language and has been used for actual torque converter designs by the Korea Powertrain Company.
천두만,김민행,이재철,안성훈 한국정밀공학회 2008 International Journal of Precision Engineering and Vol.9 No.1
A new nano-particle deposition system (NPDS) was developed for a ceramic and metal coating process. Nano- and micro-sized powders were sprayed through a supersonic nozzle at room temperature and low vacuum conditions to create ceramic and metal thin films on metal and polymer substrates without thermal damage. Ceramic titanium dioxide (TiO2) powder was deposited on polyethylene terephthalate substrates and metal tin (Sn) powder was deposited on SUS substrates. Deposition images were obtained and the resulting chemical composition was measured using X-ray photoelectron spectroscopy. The test results demonstrated that the new NPDS provides a noble coating method for ceramic and metal materials.
웹기반 재료 데이터베이스 구축 및 자동차 엔진풀리용 재료선정 예
천두만(Doo-Man Chun),안성훈(Sung-Hoon Ahn),장재덕(Jae-Duk Jang) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.4
Material selection is one of the important activities in design and manufacturing. A selected material at the conceptual design stage affects functionality of the designed part as well as manufacturability and cost of the final product. Unfortunately there are not many accessible material databases that can be used for design. In this research, a web-based material database was constructed. In order to assist designers to compare different materials, two-dimensional and three-dimensional graphs were provided via the web browser. Using these graphical tools, multi-dimensional comparison was available in more intuitive manner. As a case study, this system was applied for material selection of an automotive engine pulley.