• Journal of the Korean Society for Precision Engineering
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• v.25 no.11
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• pp.66-72
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• 2008

During the plate and foil cold rolling process, considerable values of the force of material pressure on the tool occur. These pressures cause the elastic deformation of the roll, thus changing the shape of the deformation legion. Rolled copper foils should be characterized by a good quality and light dimensional tolerances. Because of automation that is commonly implemented in flat product rolling mills, these products should meet the requirements of tightened tolerances, particularly strip thickness, and feature the greatest possible flatness. The shape of the roll gap is influenced by the elastic deformation of rolls parts of the rolling process affecter of the pressure force. However, to control roll deformation should be difficult. Because the foil thickness is very thin and the permissible deviations in the thickness of foil are small. In this paper, FE-simulation of roll deformation in thin foil cold roiling process is presented.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.166-171
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• 2007

In this paper Research development about a micro metal forming manufacturing system has been developed. A micro forming system has been achieved in Japan and it's developed micro press is limited to single forming process. To coincide with the purpose to be more practical, research and development is necessary about the press which the multi forming process is possible. We set the development of the equipment including micro deep drawing, micro punching and micro restriking process to the goal. To achieve this goal, we set the application product to a micro thin foil valve which is used in the micro pump module. The compound die set has been designed and manufactured to make two step process. The material of thin foil valve is SUS-304 and its thickness is 50$\mu$m. We can get a good forming results from micro punching experiments in this paper.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.413-416
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• 2007

In general, by means of the electrodepositing technique, a copper foil sample was prepared with a high purity and a high density. But the mechanical properties of the electrodepositing copper foil was lower than it's the rolling copper foil. However, the production of copper foil with approximately 36 microns thick in rolling process was very difficult. This paper describes the outline of the high accuracy cold rolling in 6 high mill which was developed for the purpose of rolling very thin accurate gauge copper foil(36 micron thick), and give several rolling characteristic of 600 mm wide copper foil. a) Large strain can be accumulated pass by pass in industrial multi-pass rolling processing to overcome large critical strain for thickness accuracy through optimization of rolling schedule. b) Also, permissible tension for rolling 0.45 $\sim$ 0.036 mm thick copper strip stably in accordance with the each pass work had been established by FEM simulation results. c) During the plate rolling process, considerable values of the forces of material pressure on the tool occur. These pressures cause the elastic deformation of the roll, thus changing the shape of the deformation region. A numerical simulation of roll deflection during cold rolling is presented in the paper. d) The proposed pass schedule can roll very thin copper foil of 36 micron thickness to a tolerance of ${\pm}1$ microns. The validity of simulated results was verified into rolling experiments on the copper foil.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.206-206
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• 2007

PCB기판 제작에 있어서 미세패턴을 형성하기 위한 차세대 공법으로 imprint공법을 이용하여 PCB기판제작에 대한 내용입니다. imprinting을 하기 위해서 미세때턴이 형성된 Tool-foil을 이용하여 imprinting시 Via hole을 동시 가공을 함으로서, 공정 비용 절감과 공정 프로세스 단축의 효과를 볼수 있다. 하지만 대면적(405*510size) imprint용 N-stamp제작이 쉽지 않으며, Ni-stamp가격 또한 만만치 않으며, 대면적 size일수록 이형처리 또한 쉽지 않다. 이형문제와 Stamp제작 비용을 줄이기 Cu-stamp를 제작 하여, Imprint후 이형처리 하지 않으며, Stamp제작 또한 쉬우며, 가격도 싸기 때문에 그에 따른 기대효과를 간략하게 소개 하고자 한다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.72.2-72.2
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• 2007

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.146-158
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• 1991

The flow around a two-dimensional foil section Is measured by a LDV(Laser Doppler Velocimetry) system which is capable of measuring the datailed flow field without interfering the original flow field. A 2-color 3-beam LDV system, which is capable of mea,;tiring 2 velocity components simultaneously and uses 2W Ar-Ion laser source, is used to measure the flow field around an NACA0012 foil section. The measured flow velocities are analysed iii order to study the boundary layer characteristics, flow separation and the detail structure of the flow near the trailing edge of the foil. The boundary layer characteristics are compared with the results by the head's momentum integral method. For the case of small angle of attack at relatively higher Reynolds number, both results show good agreements. The measured data of the velocity field around an NACA0012 foil section would be valuable data to validate the CFD(Computational Fluid Dynamic) calculation results. The developed experimental technique to evaluate the characteristics of two-dimensional foil sections is essential tool to develope new blade sections which have good lift characteristics and better cavitation performances.

• Tribology and Lubricants
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• v.40 no.3
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• pp.103-110
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• 2024

Gas foil thrust bearings (GFTBs) are oil-free self-acting hydrodynamic bearings that support axial loads with a low friction during airborne operation. They need solid lubricants to reduce dry-friction between the runner and top foil and minimize local wears on their surfaces during start-up and shutdown processes. In this study, we evaluate the lift-off speeds and load capacity performance of a GFTB with Polytetrafluoroethylene (PTFE) surface coating by measuring drag torques during a series of experimental tests at increasing ambient temperatures of 25, 75 and 110℃. An electric heat gun provides hot air to the test GFTB operating in the closed booth to increase the ambient temperature. Test results show that the increasing ambient temperature delays the lift-off speed and decreases the load capacity of the test GFTB. An early developed prediction tool well predicts the measured drag torques at 60 krpm. After all tests, post inspections of the surface coating of the top foil are conducted. Scanning electron microscope (SEM) images imply that abrasive wear and oxidation wear are dominant during the tests at 25℃ and 110℃, respectively. A quantitative energy dispersive spectroscopy (EDS) microanalysis reveals that the weight percentages of carbon, oxygen, and nitrogen decrease, while that of fluorine increases significantly during the highest-temperature tests. The study demonstrates that the increasing ambient temperature noticeably deteriorates the static performances and degrades the surface coating of the test GFTB.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1092-1098
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• 2007

Since one decade, the detection of HFPD (High frequency Partial Discharge) has been proposed as one of the effective method for the diagnosis of the power component under service in power grids. As a tool for HFPD detection, Metal Foil sensor based on the embedded technology has been commercialized for mainly power cable due to its advantages. Recently, for the on-site noise discrimination, several PA (Pulse analysis) methods have been reported and the related software, such as Neural Network and Fuzzy, have been proposed to separate the PD (Partial Discharge) signals from the noises since their wave shapes are completely different from each other. On the other hand, the relevant fundamental investigation has not yet clearly made while it is reported that the effectiveness of the current methods based on PA is dependant on the types of sensors. Moreover, regarding the identification of the vital defects introducible into the Power Cable, the direct identification of the nature of defects from the PD signals through Metal Foil coupler has not yet been realized. As a trial for solving above shortcomings, different types of software have been proposed and employed without any convincing probability of identification. In this regards, our novel algorithm 'PA Map' based on the pulse analysis is suggested to identify directly the defects inside the power cable from the HFPD signals which is output of the HFCT and metal foil sensors. This method enables to discriminate the noise and then to make the data analysis related to the PD signals. For the purpose, the HFPD detection and PA (Pulse Analysis) system have been developed and then the effect of noise discrimination has been investigated by use of the artificial defects using real scale mockup. Throughout these works, our system is proved to be capable of separating the small void discharges among the very large noises such as big air corona and ground floating discharges at the on-site as well as of identifying the concerned defects.

• Journal of Welding and Joining
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• v.21 no.4
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• pp.63-68
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• 2003

Scanning electron microscopy (SEM) has been used as a surface measurement instrument and a tool for lithography in semiconductor process due to its high density localized beam. For those purposes, however, the maximum current of SEM Is less than 100pA, which is not enough fo material processing. In this paper SEM was modified to increase the amount of current reaching a specimen from gun part where current is generated, the possibility of applying SEM to material processing, especially microjoining, was investigated. The maximum current of SEM after modifications was measured up to 10$\mu$A, which is about 10$^{5}$ times greater than before modifications. Through experiments such as eutectic solder wetting on thin 304 stainless steel foil and microjoining of 10$\mu$m thick 304 stainless steel, the intensity of electron beam of SEM proved to be great enough fur material processing as heat source. And a tight jig system was found necessary to hold materials close enough fur successful microloining.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.367-369
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• 2009

플렉서블 태양전지용 연성기판재에는 플라스틱재와 금속재가 있다. 기존의 연성기판인 플라스틱의 경우 열과, 내구성, 화학약품에 약하다는 단점이 있으며, 금속기판은 높은 생산원가, 박판화의 어려움 등의 문제를 안고 있다. 일반적으로 기판재와 cell을 구성하는 반도체 층의 열팽창 거동 차이에 의한 열 변형이 태양전지의 공정안정성에 영향을 주는 것으로 알려져 있으며, cell을 구성하는 반도체 층과 열팽창 거동이 유사한 금속기판재의 적용이 필요하다. Si 박막 태양전지의 경우 Si 열팽창 거동과 비슷한 특성을 갖는 기판재의 개발이 필요하다. 전주법을 적용하여 조성이 다른 Ni계 합금의 열팽창 거동을 TMA 장비를 사용하여 측정하였다. 그리고 전산해석 Tool을 활용하여 가상의 Si 박막 태양전지 제조공정을 설정하고 고온 공정온도에서 상온으로 냉각시 발생되는 층간 열변형 연구를 수행하였고 열팽창 거동이 다른 합금 상에 Si층을 증착하여 열 충격에 의한 결함 발생여부를 관찰하였다.