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나병철,윤재륜,오박균 대한기계학회 1990 대한기계학회논문집 Vol.14 No.1
본 연구에서는 세라믹 기계요소를 생산하기 위한 기초연구로서, 세라믹 사출 성형에 대한 기본적인 가공조건과 여러변수들을 고찰하고 가능한한 최대의 세라믹체적 비를 갖고 세라믹입자와 완벽한 융합을 이룰수 있는 최적의 결합제 구성과 세라믹입자 의 충진비율에 따른 혼합체(mixture)의 유동특성을 규명하여 사출성형의 적부를 판별 함과 동시에 그 훈련된 상태를 고찰하여 이후의 공정에서 불균일에 의한 결함이 발생 하지 않도록 정확한 성형조건을 제시하고자 한다. 또한 사출성형에 가장 적절한 혼 합체를 선정하여 탈지공정 및 소결을 행하고 각 공정에서의 부품의 수축률 및 결함을 관찰하여 그 결함의 원인 및 제거방법에 대하여 논의할 것이다. 본 논문에서 제시한 각 공정 및 고찰은 중요한 모든 변수들의 경향 및 특성을 다루었으며 정밀한 세라믹부 품의 신속한 생산을 위한 기초 연구로서 실제 산업체에 응용될 수 있을 것으로 사료된 다. The fabrication of ceramic machine components by injection molding(CIM : Ceramic Injection Molding) is critically dependent on the shaping and binder extraction techniques. Injection molding is of keen interest to ceramic industries because CIM is suitable for making an intricate shape and manufacturing cost is lower than other process when production scale is large. The success of the molding process is dependent on the correct formulation of the organic vehicle and the achievement of optimum filler loading. Fine alumina powders and polyethylene binder systems were employed to prepare moldable blend then produce a simple specimen by compression molding. Flow characteristics of the mixture was evaluated by viscosity measurement. Optimum binder system and ceramic volume loading for injection molding were determind. A good debinding technique was utilized to improve the quality of debinded parts and save the debinding time. The simple ceramic part was successfully sintered after debinding and its microstructure examined with SEM revealed good consolidation.
나병철,안영재,한동철,전경진,Na, B.C.,An, Y.J.,Han, D.C.,Chun, K.J. 대한설비공학회 1994 설비공학 논문집 Vol.6 No.4
One of the chlorofluorocarbon compounds. R-12 deplete atmospheric ozone. It leads to international agreement to reduce CFC production. R-134a has similar thermodynamic properties to CFC-12. It has zero ODP(Ozone Depletion Potential). This Paper focuses on the lubricating oils for using with R-134a PAGs(Polyalkylene Glycol's) and esters are primary lubricants that are now being tested for use with R-134a Because of extreme polarity of R-134a. there are many problems in the selection of lubricating oil. This investigation analyzes compressor working conditions and calculates wear parts friction for simulation testing. Miscibility and material compatibility is proved by sealed glass tests. Friction was tested on the closed type pin on disk wear tester. This equipment simulates actual refrigerating compressor. Environment controlled test made more reliable result than field test Conventional oils(mineral oils, Alkylbenzene, PAO(Polyalpha Olefin) are immiscible with R-134a. PAGs and ester oils are miscible with R-134a. Friction coefficient is similar to conventional system(mineral oil/R-12 systems) at operating condition. At start & stop condition, PAGs/R-134a system has high friction coefficient. It provide reliable result on the lubricity, miscibility, material compatibility of R-134a with these new lubricants. It suggests proper selection of refrigeration oil that may improve compressor durability of performance.
나병철,전경진,한동철 한국트라이볼로지학회 1997 한국윤활학회지(윤활학회지) Vol.14 No.1
Sealing an oil-air mixture plays important roles to have an enhanced lubrication for high speed spindle. High speed spindles require non-contact type sealing mechanism. In this study, an optimum seal design to minimize leakage is concerned in the aspect of flow control. This paper categorizes geometries of mostly used non-contact type seals and analyzes each leakage characteristics to minimize a leakage on sealing area. Effect of minimum clearance and its position are considered according to variation of detail geometry. The estimation of non-leaking property is determined by amount of pressure drop in the leakage path assuming constant leakage flow. To simulate an oil jet or oil mist type high speed spindle lubrication, the working fluid is regarded as two phases that are mixed flow of oil phase and air phase. Both of the turbulence and the compressible flow model were introduced in CFD(Computational Fluid Dynamics) analysis. Design parameters has been induced to minimize leakage in limited space, and a methodological study on geometrical optimization has been conducted.