• Journal of Korea Foundry Society
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• v.30 no.3
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• pp.115-120
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• 2010

Recently, an advanced raw material supplying system in diecasting industry that molten metal produced by the raw material supplier can be directly delivered to the diecasting shops was proposed. It was known to have advantages of reducing melting process cost and improving working environment. However, for its successful mass production, the development of high insulation ladle is inevitable. In this study, the optimal mixing ratio of $SiO_2-Al_2O_3$ was investigated and the high insulation ladle with computer simulation result was built in a prototype and evaluated. The prototype which has refractory wall of $SiO_233%-Al_2O_3$ 35%-CaO 33% showed high insulation sufficient for carrying the Al molten metal for 138 minutes. Gas quantity result and SEM-EDS analysis on the melt poured in the ladle also showed extremely low level of 0.028 cc / 100 g and no penetration of Al molten metal into the refractory wall, satisfying the requirements for mass production.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.229-229
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• 2012

Adhesion of Copper film on the aluminum oxide layer formed by anodizing an aluminum plate was enhanced by applying ion beam mixing method. Forming an conductive metal layer on the insulating oxide surface without using adhesive epoxy bonds provide metal-PCB(Printed Circuit Board) better thermal conductivities, which are crucial for high power electric device working condition. IBM (Ion beam mixing) process consists of 3 steps; a preliminary deposition of an film, ion beam bombardment, and additional deposition of film with a proper thickness for the application. For the deposition of the films, e-beam evaporation method was used and 70 KeV N-ions were applied for the ion beam bombardment in this work. Adhesions of the interfaces measured by the adhesive tape test and the pull-off test showed an enhancement with the aid of IBM and the adhesion of the ion-beam-mixed films were commercially acceptable. The mixing feature of the atoms near the interface was studied by scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.62.2-62.2
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• 2013

Recent spectroscopic observations have provided evidence for complex chemical evolution by supernovae and/or asymptotic giant branch (AGB) stars in the two metal-poor globular clusters (GCs) NGC2419 and M15. In particular, the horizontal branches (HBs) of these metal-poor GCs are very extended in the Hertzsprung-Russell diagram. The origin of these peculiar features, as well as that for the Sandage period-shift effect observed in these clusters, are yet to be understood. Here we show, by constructing population models including the Nitrogen enhanced subpopulation, that the second generation populations in these clusters would be enhanced not only in Helium, but also in Nitrogen. This working hypothesis can simultaneously explain the observed extended feature on the HB and the period-shift of RR Lyrae variables.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.956-961
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• 2000

This paper describes the design of a small size Alkali Metal Thermal to Electric Converter (AMTEC) which employs a capillary structure for recirculating sodium working fluid. The cycle is based on the simple and small capillary type ${\beta}"$ -alumina and wick tube element. The proposed cell consists of the 37 conversion elements with capillary tube of $50{\mu}m$ in diameter and the sealed cylindrical vessel of 22mm in outer diameter. Results on the cycle analysis of sodium flow and heat transfer in the cell showed that the expected power output was 4.65W and the conversion efficiency was 19% for the source temperature of 900K.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.1
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• pp.90-96
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• 2013

During the cold forming, due to high working pressure acting on the die surface, failure mechanics must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. Die wear affects the tolerances of formed parts, metal flow and costs of process etc. The only way to control these failures is to develop methods which allow prediction of die wear and which are suited to be used in the design state in order to optimize the process. In this paper, the wear experiments to obtain the wear coefficients and the upsetting processes was accomplished to observe the wear phenomenon during the cold forming process. The analysis of upsetting processes was accomplished by the rigid-plastic finite element method. The result from the deformation analysis was used to analyse the die wear during the processes and the predicted die wear profiles were compared with the measured die wear profiles.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.5
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• pp.405-409
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• 2001

This paper describes fabrication and characteristics of metal thin-film pressure sensor for working at high temperature. The proposed pressure consists of a chrom thin-film, patterned on a Wheat stone bridge configuration, sputter-deposited onto thermally oxidized Si membranes with an aluminium interconnection layer. The fabricated pressure sensor presents a low temperature coefficient of resistance, high-sensitivity, low non-linearity and excellent temperature stability. The sensitivity is 1.097∼1.21mV/V$.$kgf/$\textrm{cm}^2$ in the temperature range of 25∼200$^{\circ}C$ and the maximum non-linearity is 0.43%FS.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.10a
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• pp.44-54
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• 1994

A variational formulation and the associated finite elemet equations have been derived for general three-dimensional deformation of a planar anisotropic rigid-plastic sheet metal which obeys the strain-rate potential proposed by BARLAT et al [13]. By using the natural convected coordinate system, the effect of geometric change and the rotation of planar anisotropic axes are considered efficiently. In order to check the validity of present formulation, a cylindrical cup and a square cup deep drawing test was modeled. good agreement was found between the FE simulation and the experiment. The results have shown that the present formulation for planar anisotropic deformation can be efficiently applied to the analysis of sheet metal working processes for planar anisotropic nonferrous metals.

• Transactions of Materials Processing
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• v.20 no.4
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• pp.279-283
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• 2011

Recently incremental sheet metal forming (ISF) has used widely in making prototypes and small-volume products in automotive industry etc. We apply the ISF to make a 1/4 sized automobile body-in-white. First, ISF tests for rectangular shaped cup have been performed to clarify the formability denoting the relationship between the component wall angle and maximum cup height of safe forming. Next, a CAD model for the automobile was designed and segmented into several components in order to accommodate the working space of the CNC machine we adopted and the formability of the sheet metal. Then, a CAM software was employed to generate the tool path for manufacturing wooden dies and all the small parts. Finally, the different parts were joined into a single component by laser welding after the ISF process. By using the ISF we successfully produced the 1/4 sized automobile body-in-white.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.295-300
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• 2001

The progressive die performs a series of fundamental sheet metal working, particularly this study regards to develop the center carrier feeding type die for thick sheet metal(SS41, 2.5mm) production that is a specific division. In order to prevent defect on the production, the analysis of production part, optimum design of strip process layout, die design and die making and tryout etc. are necessary. In this study, we designed and predicted a progressive die of multi stages by wide collected data base and computer aided method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.316-319
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• 2008

The L-bending of inner-structure bonded sandwich sheet metal is examined by using a bending die attached to the material testing machine. The specimen is composed of top and bottom layers and a middle layer of pyramid-core structure and each layer is bonded by brazing. The variables chosen for experiments were clearance between punch and die, location of bend line on the specimen surface and clamping type of specimen during L-bending. Effects of these variables on deformation of specimen around die-corner radius were investigated. It was shown that the irregular shapes of recess are formed in the inner layer of bended parts and they greatly depend on working conditions.