• Journal of the Korean Society for Precision Engineering
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• v.31 no.12
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• pp.1093-1100
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• 2014

The goal of this paper is to investigate preliminary the applicability of 3D printing technologies for the development of the hot bulk forming process and die. 3D printing technology based on the plastic material was applied to the preform design of the hot forging process. Plastic hot forging dies were fabricated by Polyjet process for the physical simulation of the workpiece deformation. The feasibility of application of Laser-aided Direct Metal Rapid Tooling (DMT) process to the fabrication of the hot bulk metal forming die was investigated. The SKD61 hot-working tool steel was deposited on the heat treated SKD61 using the DMT process. Fundamental characteristics of SKD 61 hot-working tool steel deposited specimen were examined via hardness and wear experiments as well as the observation of the morphology. Using the results of the examination of fundamental characteristics, the applicability of the DMT process to manufacture hot bulk forming die was discussed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.218-223
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• 2000

Ultra precision progressive die have used for above one million's lot size of production part. In the field of design and making tool for press working, the progressive die for sheet metal (STS 304, thickness : 0.5mm) is a specific division. In order to prevent the defects, the optimum design of the production part, strip layout, die design, die making and tryout etc. are necessary. They require analysis of many kinds of important factors, i.e. theory and practice of metal press working and its phenomena, die structure, machining condition for die making, die materials, heat treatment of die component, know-how and so on. In this study, we designed and constructed a progressive die of multi-stage and performed try out. Out of these processes the die development could be taken for advance. Especially the result of tryout and its analysis become the characteristics of this paper (part 1 and part 2) that nothing might be ever seen before such as this type of research method on all the processes. In the part 2 of this study we treated die making and tryout mostly.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2136-2141
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• 2007

The Loop Heat Pipe(LHP) system uses capillary forces so as to pump the working fluid from heat acquisition to heat rejecting systems. The performance of the LHP systems depends mainly upon the operating performance of the wick structure. The capillary pressure increases with decreasing the pore size of the wick structure. By the way, the wick structure's permeability decreases with decreasing the pore size and the porosity. To obtain an ideal wick, the wick structure should possess several characteristics such as the small pore size, high porosity and chemical compatibility with working fluid. Sintered metal wicks have been mainly used as the capillary wick structure mounted in LHP because of the fact that the sintered metal wick has some advantages like convenient selection of wick material, smaller pore size and so on as well as high reliability. In this study, sintered metal wicks were developed to meet required several parameters to design the high performance LHP systems for obtaining even more effective cooling technologies.

• Transactions on Electrical and Electronic Materials
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• v.10 no.5
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• pp.147-151
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• 2009

For integrated passive device (IPD) applications, we have successfully developed and characterized metalinsulator-metal (MIM) capacitors with 2000 $\AA$ plasma-enhanced chemical vapor deposition (PECVD) silicon nitride which are deposited with the $SiH_4/NH_3$ gas mixing rate, working pressure, and RF power of PECVD at $250^{\circ}C$. Five PECVD process parameters are designed to lower the refractive index and lower the deposition rate of $Si_3N_4$ films for the high breakdown electric field. For the PECVD process condition of gas mixing rate (0.957), working pressure (0.9 Torr), and RF power (60 W), the atomic force microscopy (AFM) root mean square (RMS) value of about 2000 $\AA$ $Si_3N_4$ on the bottom metal is lowest at 0.862 nm and the breakdown electric field is highest at about 8.0 MV/cm with a capacitance density of 326.5 pF/$mm^2$. A pretreatment of metal electrodes is proposed, which can reduce the peeling of nitride in the harsh test environment of heat, pressure, and humidity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.241-241
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• 2009

For the Radio Frequency Integrated Passive Device (RFIPD) application, we have successfully developed and characterized high break-down voltage metal-insulator-metal (MIM) capacitors with 2,000 ${\AA}$ plasma-enhanced chemical vapor deposition (PECVD) silicon nitride which deposited with $SiH_4/NH_3$ gas mixing rate, working pressure, and RF power of PECVD at $250^{\circ}C$ chamber temperature. At the PECVD process condition of gas mixing rate (0.957), working pressure (0.9 Torr), and RF power (60 W), the AFM RMS value of about 2,000 ${\AA}$ silicon nitride on the bottom metal was the lowest of 0.862 nm and break-down electric field was the highest of about 8.0 MV/cm with the capacitance density of 326.5 $pF/mm^2$.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.31-34
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• 2008

The L-bending of inner-structure bonded sandwich sheet metal is examined to reduce springback and defects of bent parts. The specimen is composed of top and bottom layers and a middle layer with dimple type-inner-structure and each layer is bonded by resistance welding. This specimen with hollow type-inner-structure shows different bending characteristics from the conventional sandwich sheet metals with solid type-inner-structure. The experiments were conducted for two kinds of working conditions, that is, clearance and movement of first bent specimen for second bending. The deformed profile, bend angle and springback were investigated and compared and then the proper working conditions for L-bending of sandwich sheet metal were prosed.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.289-294
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• 2001

This study reveals the thin sheet metal Process with multi-forming die that the name is progressive die, also high precision production part is made. They require analysis of many kinds of important factors, i.e. theory and practice of metal press working and its phenomena, die structure, machining condition for die making, die material, heat treatment of die components, know-how and so on. In this study, we designed and constructed a multi-forming progressive die as a bending working of multi-stage and peformed through the try out. Out of the characteristics of this paper that nothing might be ever seen before such as this type of research method on the all of processes of thin and high precision production part.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1528-1533
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• 2004

In this study, we have manufactured the LHP(Loop Heat Pipe) with sintered metal wick and investigated the working characteristics of LHP experimentally.Water was used as a working fluid and fill charge rate was changed. LHP basically consist of the separated vapor/liquid channels, evaporator having sintered metal wick(effective pore diameter :$16{\sim}19{\mu}m$), and condenser cooled by water. The diameter of vapor/liquid line tube are 3.2mm/6.35mm, respectively. Heat transfer rate and thermal resistance was represented to study the basic characteristics of LHP at each conditions

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.162-167
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• 2000

Synthetic water-based metal-cutting fluids are increasingly popular in the metal-working industry because of its environmental friendliness. However, the fluids have the problem to be decomposed by microbes with use. Thus, it is very important to evaluate the stabilities of the fluids against microbes for the excellent fluids. The purpose of this study is to investigate the biodegradability of several lubricating agents used to improve anti-wear property of the fluids. From the study, it was found that there existed some difference on the biodegradability against microbes such as Escherichia coli and Klepsiella pneumoniae depended on the structure of the lubricating agents and pH of the fluids.

• Bulletin of the Korean Chemical Society
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• v.18 no.3
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• pp.316-318
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• 1997

A general and universal detection method, which can be used in high performance liquid chromatography (HPLC) and flow injection analysis (FIA) system for the determination of any metal ions complexing with ethylenediaminetetraacetic acid (EDTA), is demonstrated. Pulsed amperometric detection scheme is applied in a flow-through thin layer electrochemical cell at an Au working electrode. Fluctuation of peak current level at the same flow rate of carrier solution is minimized at this solid working electrode, whereas not at a dropping mercury electrode. Removal of dissolved oxygen can be omitted with this detection method, which is a required step for cathodic detection methods. Also, a group of metal ions can be determined selectively and indirectly with this detection scheme.