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실리타 코팅된 CI particle을 이용한 SUS 304의 초정밀 연마
홍광표(K. P. Hong),이정원(J. W. Lee),하석재(S. J. Ha),조용규(Y. K. Cho),이현주(H. J. Lee),조명우(M. W. Cho),최형진(H. J. Choi),제태진(T.J.Je) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
Recently, the magnetorheological (MR) polishing method has been performed as a new ultra precision polishing technique for many industrial applications. This method uses MR fluids, which consists of carbonyl iron (CI) particle, carrier fluid, additives and dispersion stabilizer. However, CI particle are easily oxidized in water. This problem leads to unpredictable polishing results and reduces the life of MR fluid. To solve the problem, in this study, Silica-coated CI particles were used for MR polishing. Their rheological properties were analyzed to compare silica coated MR fluid and uncoated MR fluid. As a result, in terms of surface roughness, MR polishing with silica-coated CI based MR fluid (Ra=1.89nm) shows a better than that of uncoated CI based MR fluid.
김철암,최형진,윤형기,박성룡,김종엽 ( C . A . Kim,H . J . Choi,H . K . Yoon,S . Y . Park,J . Y . Kim ) 한국공업화학회 1998 공업화학 Vol.9 No.1
양이온 계면활성제를 이용하여 마찰저항 감소의 특성과 유변학적 거동을 규명하였다. 양이온 계면활성제는 CMC이상의 농도에서 미세구조의 변화가 일어나 미셀의 형태가 구형에서 실린더형 또는 디스크형 미셀로의 전이가 일어난다. 마찰저항감소는 이러한 미셀의 전이가 일어나게 하는 농도 이상에서 발현된다. 따라서 농도 변화에 따른 마찰저항감소를 측정하였으며, 이러한 마찰저항 감소를 규명하기 위하여 유변학적 특성을 조사하였다. 미셀은 non-Newtonian거동을 보이며, 구조의 전이가 일어남에 따른 증거로 shear thickening 현상을 보였다. 그리고 양이온 계면활성제중의 하나인 DOBON-G의 경우에는 counter-ion의 첨가에 의해 이러한 구조의 전이거동이 변화되는 것을 관찰하였다. The characteristics of drag reduction and rheological behaviors were investigated using cationic surfactants, whose microstructures are known to change when concentration of the surfactant exceeds CMC. The firstly formed spherical micelles change to rodlike or disklike micelles because of packing between surfactants micelles, and of thermodynamic preference. The drag reduction becomes significant when the concentration increases over this micellar transient point. Drag reductions were measured as a function of concentration, and rheological characteristics of the surfactant were further investigated to understand the correlation between their rheological properties and drag reduction. Micelles show the non-Newtonian behavior, and shear thickening behaviors were observed due to the structural development. In addition, structural developments were determined by adding the counter-ion in case of DOBON-G.
Xantan gum로 코팅된 CI-particle를 이용한 MR Polishing 특성에 관한 연구
이정원(J.W.Lee),하석재(S.J.Ha),신봉철(B.C.Shin),김동우(D.W.Kim),조명우(M.W.Cho),최형진(H.J.Choi) 한국소성가공학회 2011 금형가공 심포지엄 Vol.2011 No.9
An finishing process using magnetorheological fluid (MR) fluid has been developed as a new precision finishing technique to obtain a fine metal surface. For MR polishing process, MR fluid was consists of CI particles, nonmagnetic polishing abrasives, water and stabilizers. One of the main ingredients in MR fluid is the magnetic CI particles. But carbonyl iron used in MR fluids a severe corrosion problem. Through coated on the CI particles had study the defect supplementation. It is understand the rheological behavior of the MR fluid based on the coated CI particles. Also the objectives of this research is to investigate the surface roughness obtained from the MR polishing process.
고분자물질(高分子物質) 첨가(添加)에 따른 마찰저항감소(摩擦抵抗減少)에 관한 연구(硏究)
김재근,차경옥,최형진,김종보,Kim, J.G.,Cha, K.O.,Choi, H.J.,Kim, C.B. 대한설비공학회 1996 설비공학 논문집 Vol.8 No.2
It is well known that drag reduction in single phase liquid flow is affected by polymer material, molecular weight, polymer concentration, pipe diameter, and flow velocity. Drag reduction in two phase flow can be applied to the transport of crude oil, phase change system such as chemical reactor, pool and boiling flow, and to present cavitation which occurs in pump impellers. But the research of drag reduction in two phase flow is not sufficient. The purpose of the present work is to evaluate the drag reduction by measuring pressure drop, void fraction, mean liquid velocity, and turbulent intensity whether polymer is added in the horizontal two phase system or not. Experiment has been conducted in a test section with the inner diameter of 24mm and the length of 1,500mm. The polymer materials used are two kinds of polyacrylamide[PAAM] and co-polymer[A611P]. The polymer concentration was varied with 50, 100 and 200 ppm under the same experimental conditions. Experimental results showed that the drag reduction of co-polymer is higher than that of polyacrylamide. Mean liquid velocities increased as polymer was added, and turbulent intensity decreased inversely near the pipe wall.
김남수,김종보,김인석,최형진,Kim, N.S.,Kim, C.B.,Kim, I.S.,Choi, H.J. 대한설비공학회 1993 설비공학 논문집 Vol.5 No.3
Experimental investigations have been carried out to find the effect of drag reduction caused by effective polymer additives in turbulent flows. The experiments were undertaken with a test section of 9.8mm pipe diameter and 3500 mm pipe length(L/D=357) in a closed loop, and Copolymer-X and Polyacrylamide(PAAM) were used as polymer additives for comparisons. The tests were carried out under different polymer concentrations, and the temperatures of the flow considered were $26^{\circ}C$, $60^{\circ}C$ at the flow velocity of 5.3 m/s. The rate of drag reduction obtained by Copolymer-X is found to be considerably higher than that of PAAM in turbulent flows. Copolymer-X is also found to be very reliable for mechanical degradation, which has not been the case in any other additives. It is concluded that Copolymer-X is considered to be one of the most effective agents as an additive especially for long time hydraulic transports. It is also found that polymer degradation in more likely at lower polymer concentrations in the turbulent flows.