• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.244-251
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• 2011

Pipe rolling process using the planetary rolling mill for AISI 304 stainless steel has been studied by using finite element method. Mannesmann method using three-roll is applied to this rolling process. Commonly, rolling process has started from the cold working and finished to the hot working. This rolling process has more advantage that make reduction of process and cost than existing extrusion process. This process includes various and complex process parameters. Each of the process parameters affects forming result. Therefore, all of the process parameters should be considered in FEA. In this study, possibility and productivity of forming pipe for AISI 304 stainless steel had been investigated. Also, preheating process and variations of rotation velocity and product thickness were considered in FEA. Rolling process for AISI 304 stainless steel pipe was successfully simulated and it should be useful to determine optimal rolling condition.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.592-600
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• 2012

Conventional methods for preparing ceramic bodies, such as cold isostatic pressing, gypsum-mold slip casting, and filter pressing are not completely suitable for fabricating large and thick ceramic plates owing to disadvantages of these processes, such as the high cost of the equipment, the formation of density gradients, and differential shrinkage during drying. These problems can be avoided by employing a pressure-vacuum hybrid slip casting approach that considers not only by the compression of the aqueous slip in the casting room (pressure slip casting) but also the vacuum sucking of the dispersion medium (water) around the mold (vacuum slip casting). We prepared the alumina formed bodies by means of pressure-vacuum hybrid slip casting with stepwise pressure loading up to 0.5 MPa using a slip consisting of 40 vol% solid, 0.6 wt% APC, 1 wt% PEG, and 1 wt% PVA. After drying the green body at $30^{\circ}C$ and 80% RH, the green density of the alumina bodies was about 56% RD. The sintered density of an alumina plate created by means of sintering at $1650^{\circ}C$ for 4 h exceeded 99.8%.This method enabled us to fabricate a $110{\times}110{\times}20$ mm alumina plate without cracks and with a homogeneous density, thus demonstrating the possibility of extending the method to the fabrication of other ceramic products.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.515-526
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• 2009

There are three main production processes in the manufacture of concrete-filled square steel columns. The first process is known as the 'box-type process' or 'four-seam method,' wherein four beams are welded together at the seams. The second is the 'cold-forming process' or 'two-seam method,' wherein the seams of two channel beams are welded together. The third is the 'pressing process' or 'one-seam method,' wherein a circular column is pressed until it becomes a square column. In calculating the production cost for the making of a steel tube, it is very important to consider the welding process to be used and the desiredthickness of the steel tube, such as a square column that was developed under a new method, formed through the four-seam flare welding method at the center of the steel column width, following the L-shape formation. Certain tests were suggested in this study to evaluate the welding amount of concrete-filled square steel columns. With the parameters of the production method of a square steel column, the thickness of the steel square columns, and the welding amount, six specimens were produced. A structural test and finite-element analysis were conducted to assess the behavior of the steel column according to the water pressure inside the steel columns.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.223-229
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• 2016

In this study, a cold forging process was developed for the roller tappet housing of an engine valvetrain system. A tappet sample was manufactured and subjected to an endurance test. The material properties were obtained from a compression test, and forging analysis was carried out to design a forging process using a commercial program, Deform-3D. The forging process was set up based on the analysis results, and a die set and sample tappet housing were manufactured. To evaluate the sample, the dimensional accuracy, surface roughness, parallelism, and concentricity were measured and confirmed. To evaluate the actuation and durability, a special test rig was developed to simulate the valvetrain system of the engine. An actuation test was performed based on the idle speed of a general diesel engine, and an endurance test was done based on the maximum speed. The results show minor wear of 0.002 mm. The developed test rig will be used to evaluate the actuation and durability of other valvetrain parts.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.356-364
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• 1998

The dependence of green and sintered densities of Zirconia-Toughened Alumina ($ZTA:\;Al_2O_3/\;15\;vol{%}\;ZrO_2$) on the properties of spray-dried granules was studied thoroughly to establish the optimum compaction condition leading to high reproducibility in the light of sintered density. The sphericity, mean size, degree of hollow occurrence and moisture content of spray-dried granules were largely different in between the granule containing binder and the ones with no binder. The effect of these differences in the characteristic of granules on the compaction behavior was examined in terms of the compaction pressure from 80 MPa to 120 MPa 10 MPa increment and the compaction method, i.e., uniaxial and cold isostatic pressing. This work confirmed that the reproducibility of sintered density caused by the variation of granule property could be improved by the optimization of compaction process. The variation of sintered density was controlled within 1 % deviation by compacting the granules under a relatively low pressure of 80 MPa in an uniaxial forming and subsequent cold isostatic pressing at high pressure of 500 MPa.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.314-319
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• 2016

Flange bolt has a circular flange under the head that acts like a washer to distribute the clamping load over a large area. Flange bolt has usually been manufactured by cold forging. Flower shape defect occurs in the flange forging stage. This defect causes lack of dimensional accuracy and low quality. So it is needed to improve these forging defects. In this study, die design method for flower shape defect of flange bolt was suggested. In order to improve flower shape defect, inner diameter of the addition die in conventional forging process was modified. The forging process with applied modified die was simulated by commercial FEM code DEFORM-3D. The simulated results for modified die were confirmed by experimental trials with the same condition.

• Herbal Formula Science
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• v.21 no.1
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• pp.142-153
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• 2013

Objectives : Examined the editing system and the characteristics of "Clinical Formula Science of Korean Medicine" to establish a basis for compilation system of the common formula science textbook for colleges of Korean medicine nationwide. Methods : Comprehended the "Clinical Formula Science of Korean Medicine" published by professor Hyeongok(1911-1987) in 1985 and analyzed its configuration system. Results : "Clinical Formula Science of Korean Medicine" has made it possible to understand the formula systematically by establishing and classifying 24 kinds of treatment method [the three treatment methods of cold-dampness, dryness-heat and interior deficiency and its subdivision, 19 kinds of treatment method (stomach, phlegm, eum, yang, spirit, essence, ki, blood, blood stasis, exterior, interior, half-exterior half-interior, water, wind, cold, heat, dampness) combined with reducing and vomiting] and main formula. These can be considered as professor Hyeongok's own method of classification, which is distinctive from the existing formula science system. Also, it suggests that a Korean medicine doctor should not use a biased formula science that is limited to some schools but apply the formula widely and synthetically because it is believed to pursue perfection in cure if the main formulas related to a physical disorder, pregnancy and childbirth, invigorating and purging five viscera, and Four-Constitution Medicine are added. Conclusions : "Clinical Formula Science of Korean Medicine" is seen as a formula science book which is to be consulted when compiling a common formula science textbook for colleges of Korean medicine by forming a Korean formula science system that is distinctive from that of China.

• Resources Recycling
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• v.9 no.2
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• pp.46-52
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• 2000

Aluminum can to can recycling was divided into two stpes. The first step was composed of the processes such as collection of used beverage cans (UBC), shredding, magnetic separation, De-laquiring, melting and casting. The second one was remelting and casting, heat treating, hot and cold rolling, annealing, and can making. In this study, the effect of alloying elements on the microstructure and texture of the secondary ingots made by Al UBC was investigated. In aluminum can to can recycling, the second phase particles appeared in the solidification stage must be controlled by heat treatment. The optimum heat treatment condition was $615^{\circ}C$ for 5hrs. the texture in hot rolled sheet was depressed with increasing Mn content, on the other hand, Si and Fe elements promoted the texture development. The textures of can-body sheet should be controlled in the hot rolling and annealing stage because can was formed from cold rolled sheet without heat treatment.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.2
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• pp.75-83
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• 2017

In severe accident conditions of light water reactors, the loss of coolant may cause problems in integrity of zirconium fuel cladding. Under the condition of the loss of coolant, the zirconium fuel cladding can be exposed to high temperature steam and reacted with them by producing of hydrogen, which is caused by the failure in oxidation resistance of zirconium cladding materials during the loss of coolant accident scenarios. In order to avoid these problems, we develop a multi-metallic layered composite (MMLC) fuel cladding which compromises between the neutronic advantages of zirconium-based alloys and the accident-tolerance of non-zirconium-based metallic materials. Cold pilgering process is a common tube manufacturing process, which is complex material forming operation in highly non-steady state, where the materials undergo a long series of deformation resulting in both diameter and thickness reduction. During the cold pilgering process, MMLC claddings need to reduce the outside diameter and wall thickness. However, multi-layers of the tube are expected to occur different deformation processes because each layer has different mechanical properties. To improve the utilization of the pilgering process, 3-dimensional computational analyses have been made using a finite element modeling technique. We also analyze the dimensional change, strain and stress distribution at MMLC tube by considering the behavior of rolls such as stroke rate and feed rate.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.65-65
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• 2011

Early-type galaxies represent the end point of galaxy evolution and, despite pervasive residual star formation, are generally considered "red and dead", that is composed exclusively of old stars with no star formation. Here, their molecular gas content is constrained and discussed in relation to their evolution, supporting the continuing importance of minor mergers and/or cold gas accretion. First, as part of the Atlas3D survey, the first complete, large, volume-limited survey of CO in normal early-type galaxies is presented. At least of 23% of local early-types possess a substantial amount of molecular gas, the necessary ingredient for star formation, independent of mass and environment but dependent on the specific stellar angular momentum. Second, using CO synthesis imaging, the extent of the molecular gas is constrained and a variety of morphologies is revealed. The kinematics of the molecular gas and stars are often misaligned, implying an external gas origin in over a third of all systems, more than half in the field, while external gas accretion must be shot down in clusters. Third, many objects appear to be in the process of forming regular kpc-size decoupled disks, and a star formation sequence can be sketched by piecing together multi-wavelength information on the molecular gas, current star formation, and young stars. Fourth, early-type galaxies do not seem to systematically obey all our usual prejudices regarding star formation (e.g. Schmidt-Kennicutt law, far infrared-radio continuum correlation), suggesting a greater diversity in star formation processes than observed in disk galaxies and the possibility of "morphological quenching". Lastly, a first step toward constraining the physical properties of the molecular gas is taken, by modeling the line ratios of density- and opacity-sensitive molecules in a few objects. Taken together, these observations argue for the continuing importance of (minor) mergers and cold gas accretion in local early-types, and they provide a much greater understanding of the gas cycle in the galaxies harbouring most of the stellar mass. In the future, better dust masses and dust-to-gas mass ratios from Herschel should allow to place entirely independent constraints on the gas supply, while spatially-resolved high-density molecular gas tracers observed with ALMA will probe the interstellar medium and star formation laws locally in a regime entirely different from that normally probed in spiral galaxies.