• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.149-152
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• 2000

By using a three-dimensional finite element program HydroFORM-3D based on a rigid-plastic model, the hydroforming process for automobile subfrmae is analyzed in this study. The goal of this study is to accomplish preform design and determine the level of internal pressure for producing final hydroformed subframe component. Prior to hydroforming, the initial tube blank must be bent to the approximate centerline of the final part to enable the tube to be placed in the die cavity, After then, a preforming operation like stamping is carried out to the prebent tube. Finally, hydroforming process is performed to the preformed tube to get the final production. And through ductile fracture theory, the failure, bursting, is predicted during hydroforming process for tube blank with different diameter.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1847-1850
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• 2008

The process conditions during ultraviolet nanoimprint lithography (UV-NIL) process such as temperature, stamping pressure, UV irradiation, etc. are effective factors for successful imprinting of complex and fine patterns. In this study, the effects of aluminum mold on the thermal characteristics of UV-NIL process were investigated through imprinting experiments and numerical simulations. The temperature of polymer resin on mold was measured to study thermal characteristics during UV curing. From the experimental and numerical results, the importance of curing reaction control for UV-NIL process was discussed for deformation characteristics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.845-848
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• 2002

The wrinkling in the flange and wall of a part is a predominent failure mode in stamping of sheet metal parts. In many cases this wrinkling may be eliminated by appropriate control of the blank holding forco(BHF), but BHF affects the draw depth. Gotoh had studied the wrinkles under 0.02mm in height. In general, the height of wrinkles could be limited under 0.2mm practically. Therefore small BHP can be allowed so that the depth of drawing could be increased. Authors research the variation of the wrinkles in flange in the course of cup drawing by using aluminium alloy Al050 and A5052.

• Transactions of Materials Processing
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• v.17 no.6
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• pp.401-406
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• 2008

The frictional behavior of stamping process is a function of interface parameters such as sheet and tool material, lubricant, surface roughness, contact pressure, sliding speed etc. Among these parameters the thing that can be controlled by a steel maker is the surface roughness of sheet. In this study, effects of surface roughness on the frictional behavior of steel sheet for automotive were investigated to find out the way to improve the frictional characteristics of steel sheet. The cold rolled steel sheets with various surface roughnesses were prepared for the test. The flat type friction test was conducted with different lubricant conditions. The surface roughness effect on frictional behavior depends on the viscosity of lubricant. The frictional characteristic of steel sheet was influenced by the amplitude of roughness as well as the shape of that.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.4
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• pp.223-228
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• 2005

Tube hydroforming provides a number of advantages over conventional stamping process, including fewer secondary operation, weight reduction, assembly simplification, adaptability to forming of complex structural components and improved structural strength and stiffness. It can produce wide range of products such as subframe, engine cradle, and exhaust manifold. In this study, the effect of the heat treatment conditions such as post seam annealing (PSA) and bright annealing (BA) on the ovality and hydro-formability of steel tubes has been investigated. Hydroformabilities have been estimated by the bulging heights obtained at various processing parameters such as internal pressure, axial feeding and heat treatment conditions. The ovality and forming height are strongly influenced by material properties after heat treatments.

• Korean Journal of Environment and Ecology
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• v.18 no.2
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• pp.191-196
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• 2004

Mt. Deogyusan, 1,614m in altitude, is located in the southwest of South Korea. Around Mt. Duckyu, many Korean endemic and rare plants are populated, so it is considered a very important biogeographical area where the temperature zones of northern and southern plants are crossed. Because it is the graceful figure of Mt. Duckyu, it is a common mountain where many tourists visit frequently. Continuous tourist's visit may cause a bad influence on vegetation around the climbing paths. Therefore, weed community around the climbing paths on Mt. Duckyu, where visitors exert a bad influence directly on its community by coming in and out, was surveyed phytosocialogically. Our surveys have been accomplished from July to August, 2003. Weed communities formed around the climbing paths on Mt. Duckyu were divided into several patterns and analysed. They have been divided into 8 communities and 4 subcommunities. Community A: Plantago asiatica community, A-a: Carex bostrychostigma subcommunity, A-b: Artemisia princeps var. orientalis subcommunity, B: Sasa borealis community, B-a: Carex siderosticta subcommunity, B-b: Veratrum parulum subcommunity, C: Rubus crataegifolius community, D: Hosta longipes community, E: Tripterygium regelii community, F: Miscanthus sinensis var. purpurascens community, G: Carex okamotoi community, H: Lespedeza maximowiczii community. The flora surveyed in these communities was constituted of 34 families, 83 genera, 12 varieties, and 92 species. Wild plants such as Plantago asiatica, Artemisia princeps var. orientalis, Rubus crataegifolius, Sasa borealis and Miscanthus sinensis var. purpurascens were mostly light loving plants and higher resistant plants against the stamping pressure.

• Korean Journal of Environment and Ecology
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• v.17 no.3
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• pp.232-241
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• 2003

Mountain Chungyeong, 879m in altitude, is located in the northeast of the middle area in Korea. Around Mt. Chungyeong, many Korean endemic and rare plants are populated, so it is considered a very important biogeographical area where the temperature zones of northern and southern plants are crossed. Because it is close to Seoul, a capital of Korea, it is a common mountain where many tourists visit frequently. Continuous tourist's visit may cause a bad influence on vegetation around the climbing paths. Therefor, weed community around the climbing paths on Mt. Chungyeong, where visitors exert a bad influence directly on its community by coming in and out, was surveyed phytosocialogically. Our surveys have been accomplished from August, 2001 to September, 2002. weed communities formed around the climbing paths on Mt. Chungyeong were divided into several patterns and analysed. They have been divided into 5 communities and 5 subcommunities. Community A: Plantago asiatica community, A-a: Erigeron annuus subcommunity, A-b: Carex. lanceolata subcommunity, B: Pseudostellaria palibiniana community, B-a: Carex siderosticta subcommunity, B-b: Galium trachyspermum subcommunity, C: Pueraria thunbergiana community, D: Lespedeza maximowiczii community, E: Rubus crataegifolius community, F: Oplismenus undulatifolius community, The flora surveyed in these communities was constituted of 47 families, 101 genera, 17 varieties, and 149 species. Wild plants such as Plantago asiatica, Erigeron annuus, Erigeron strigosus, Pueraria thunbergiana, Lespedeza maximowiezii, Rubus crataegifolius, Artemisia princeps var. orientalis, Artemisia japonica and Lysimachia clethroides were mostly light loving plants and higher resistant plants against the stamping pressure. Our result from the ranking all surveyed areas by the Bray-Curtis ordination method was very similar to the results from phytosocialogical table analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1575-1578
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• 2005

As GA(Galvannealed sheet steel, GA) has good corrosion resistance, weldability and paintability as well as excellent stamping formability it's demand is rapidly increasing for automotive panel. But the layer of the Galvannealed sheet steel is easy to have a coating layer such as powdering and flaking in the press process because it is composed of Fe-Zn alloy. Therefore, the process condition is properly required to form the surface treated sheet steel. The frictional characteristics with dies are changed according to the annealing temperature, $505^{\circ}C,\;515^{\circ}C\;and\;540^{\circ}C$ during the process. To obtain the frictional characteristics of GA sheet steel in this study, on flat friction test is conducted. The friction coefficient is compared with the variation of pressure and velocity, viscosity of lubricant at the various galvannealed temperatures.

• Journal of the Semiconductor & Display Technology
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• v.15 no.2
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• pp.74-80
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• 2016

This study presents a thermal device specially designed for thermal nanoimprint lithography equipments, which requires the capability of rapid heating and cooling, high temperature uniformity and the material strength to endure high stamping pressure. The proposal to meet these requirements is a planar-type hot plate extensible to a large area, in which long circular cartridge heaters and heat pipes are installed inside in parallel. The heat pipes are connected to the outside water cooling chamber. A hot plate made of stainless steel is fabricated with a dimension $240mm{\times}240mm{\times}20mm$. Laboratory experiments are conducted to examine the thermal performance of the hot plate. The results illustrate that the employment of heat pipes leads to a notable enhancement of temperature uniformity in the device and provides an efficient heat delivery from the hot plate to outside. It is verified that the suggested hot plate could be a feasible thermal tool for thermal nanoimprint lithography, satisfying the major design requirements.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.555-559
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• 2005

Spinning process is a chipless metal forming method for axis-symmetric parts, which is more economical, efficient and versatile method for producing parts than other sheet metal forming process such as stamping or deep drawing. The large-sized spindle for spinning machine is the equipment to ferm a high-pressure vessel into the demanded shape. The important problem in the spindle system fur spinning machines is to reduce and minimize the thermal effect by motor and bearings. In this study, the effect of heat generation of bearings for the large-sized spindle is considered. Temperature distribution and thermal displacement of the spindle system for spinning machine can be analyzed by using the finite element method. The numerical results are compared with the measured data. The results show that temperature distribution and thermal displacement can be reasonably estimated by using the finite element method and the three dimensional model.