• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.168-174
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• 1998

In the present study, a method for measuring the relative density by the hardness measurement was proposed for sintered metal powder compacts. It is based on the indentation force equation, by which the relative density is related with the hardness, that was obtained by the finite element analysis of rigid-ball indentation on sintered metal powder compacts. For verifying the method, it was applied to prediction of density distributions in sintered and sintered-and-forged Fe-0.5%C-2%Cu powder compacts.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.10 no.3
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• pp.220-227
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• 1981

The purpose of this paper is to investigate the potential ability of sintered metal tube to promote heat transfer. In the experiment for Freon - 11, the boiling heat transfer on the sintered metal tube of bronze element is investigated and compared with that of the bronze tube (bare tube) atmospheric pressure. The experimental results are obtained as follows : 1) For sintered metal tubes of bronze element with particle diameters which ranges from $79({\mu})\;to\;461({\mu})$ and bare tube, boiling characteristic curves are expressed as : a) Sintered metal tube $$q{\propto}{\Delta}T^{1.05\~1.373}$$ b) Brae tube $$q{\propto}{\Delta}T^{3.096}$$ 2) Compared with that of the bare tube at low temperature difference$({\Delta}T_{sat})$, boiling heat transfer coefficient of the sintered bronze tube are relatively high. 3) There is tendency that curves of boiling heat transfer coefficients of sintered ·bronze tube and bare tube approach each other at rather high temperature difference. It is due to the increasing rate of the former heat transfer coefficient along with temperature difference is smaller than that of the latter. 4) Referring to particle diameter, optimum condition, i. e. , maximum heat transfer coefficient is found to be at approximately 2 mm thickness of sintered layer with $D_p=150({\mu})$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2003.10a
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• pp.128-129
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• 2003

• 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.

• Tribology and Lubricants
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• v.15 no.1
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• pp.108-115
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• 1999

The electrical and frictional properties of oil-impregnated sintered-metal bearing (OSB) and herringbone-grooved fluid bearing (HFB) with varying loads and speeds were measured. OSB shows very good performance up to 20,000 rpm and 0.05 N, and HFB successfully works up to 35,000 rpm and 0.05 N. From the endurance tests on start-stop and continuous operation, it was confirmed that those bearings could be mass-produced fur use on scanner motor in a laser scanner unit.

• Tribology and Lubricants
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• v.13 no.3
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• pp.108-114
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• 1997

The electrical and frictional properties of new sintered-metal bearing (S-bearing) with varying loads and speeds were measured. Also those were compared with the same products(J-bearing) made in Japan and the conventionally used ball bearing. The test results show that the frictional values of S-bearing are less than those of J-bearing, and that S-bearing operates in full-hydrodynamic lubrication regime. The values of rating current, starting time and jitter reveal that S-bearing is superior to J-bearing as well as ball bearing.

• Journal of Powder Materials
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• v.4 no.3
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• pp.188-195
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• 1997

In most of sintered metal powder compacts, the sintered density distribution is controlled to be as high and uniform as possible to ensure the required mechanical properties. In general, the density distribution in the compacts is not uniform and not easy to measure. In the present study, a method for measuring the density distribution was developed, based on the indentation force equation by which the hardness and the relative density were related. The indentation force equation, expressed as a function of strength constant, workhardening coefficient and relative density, was obtained by finite element analysis of rigid-ball indentation on sintered powder metal compacts. The present method was verified by comparing the predicted density distribution in the sintered Fe-0.5%C-2%Cu compacts with that obtained by experiments, in which the density distribution was directly measured by machining the compacts from the outer surface progressively.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.479-482
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• 2006

The most the electronic industry has recently accelerated the modularization, the miniaturization and the high integrated trend of electronics fields such as electronics components, appliances and etc., the most increasingly the heat generation problem rises. Even though the conventional cooling technologies are widely used in order to reduce the heat loads, the technologies are not easy to meet the present trends due to the fact that most of many conventional methods are relative to external form environments such as size, design and so on. With regardless of those environments, however, a heat pipe is one of the most efficient systems to improve the heat transfer performance. And then the performance of the heat pipe depends on a wick structure. Of various wick structures, sintered metal wick is known so that it has some advantages such as smaller pore size, increasing porosity as well as high reliability. In this study sintered metal wicks, thickness 0.7 mm, 0.8 mm and 0.9 mm, were manufactured as of $100{\mu}m$ copper powder to obtain the manufacturing technology of heat pipes mounted with a sintered metal wick. Furthermore, experiments for the operational performance factors such as capillary limit, thermal resistance were not only performed but also compared with a theoretical model simultaneously. Experimental results agreed with the theoretical model, and then it seems to be required to study various development processes of sintered metal wicks for the high performance of a heat pipe system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.8
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• pp.617-623
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• 2008

The membrane filter adhered with nanostructured porous layer was made by heat treatment after deposition of nanoparticle-agglomerates sintered in aerosol phase onto a conventional micron-fibrous metal filter as a substrate filter. The Sintered-Nanoparticle-Agglomerates-coated NanoStructured porous layer Membrane Filter (SNA-NSMF), whose the filtration performance was improved compared with the conventional metal membrane filters, was developed by adhesion of nanoparticle-agglomerates of dendrite structure sintered onto the micron-fibrous metal filter. The size of nanoparticle-agglomerates of dendrite structure decreased with increasing the sintering temperature because nanoparticle-agglomerates shrank. When shrinking nanoparticle-agglomerates were deposited and treated with heat onto the conventional micron-fibrous metal filter, pore size of nanostructured porous layer decreased. Therefore, pressure drops of SNA-NSMFs increased from 0.3 to 0.516 kPa and filtration efficiencies remarkably increased from 95.612 to 99.9993%.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.759-760
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• 2006

Ti-6Al-4V has low specific gravity, high corrosion resistance and superior mechanical properties but it is very difficult to control oxygen content in MIM process. It is necessary to use powders with coarse particle size to decrease oxygen content of powders, so feedstocks with poor fluidity and sintered bodies with lower density are obtained in such cases. Fine titanium hydride-dehydride powders were blended with atomized powders to accomplish higher fluidity and sintered density. Sintered bodies had higher sintered density and mechanical properties equivalent to those of wrought materials by controlling oxygen content less than 0.35mass%.