• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.77-78
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• 2007

AZ31 마그네슘 판재의 장식 도금을 공정 개발을 적용하기 위한 기초 연구로서 전처리 특성에 따른 마그네슘 AZ31 판재의 아연치환도금의 특성을 연구하였다. AZ31 판재는 다이캐스팅으로 사용되는 AZ91 소재에 비해 산세에 대해 민감한 반응을 나타내었다. 소재의 균일화는 시편 E와 F에서 균일하고 광택 있는 표면을 얻었고, 질산은 표면 에칭효과만을 가진다는 것을 알 수 있었다. 아연치환도금을 위한 전처리에 있어서는 시편 E에서 우수한 밀착력을 나타내었다. 이후 청화동 도금과 황산동 도금, 니켈도금 3가 크롬도금을 실시하여, X-cutting 테이핑 테스트에서 양호한 밀착성과 내식성 72시간, 열탕시험을 만족하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.114-114
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• 2009

마그네슘은 실용금속 중에서 열역학적으로 가장 활성이 큰 부류에 속하며, 그 표준적극전위는 -2.363VNHE (NHE: 수소표준전극기준)으로 대기중에서 표면부터 신속하게 산화되는 내식성에 큰 취약점을 가지고 있어, 내식성과 낮은 표면전기저항성을 갖는 마그네슘판재용 화성처리를 제안하기 위해 망간-인산염, 바나듐, 세륨, 불화 실리콘 등의 화합물로 구성되는 여러 가지의 화성처리용액을 제조한 뒤 침지처리시간을 달리하는 방법으로 마그네슘판재를 코팅하였다. 코팅된 시편을 이용하여 색상과 광택, 표면전기저항, 내식성 등에 대한 특성을 고찰하였다.

• Journal of Life Science
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• v.26 no.6
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• pp.633-639
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• 2016

Biomaterials including polymer, metal, ceramic, and composite have been widely applied for medical uses as medical fibers, artificial blood vessels, artificial joints, implants, soft tissue, and plastic surgery materials owing to their physicochemical properties. However, the biocompatibility and toxicity for film- and plate-form biomaterials is difficult to measure in mammalian cells because there is no appropriate incubation system. To solve these problems, we developed a novel mammalian cell culture system consisting of a silicone ring, top panel, and bottom panel and we applied two polymer films (PF) and one metal plate (MP). This system was based on the principal of sandwiching a test sample between the top panel and the bottom panel. Following the assembly of the culture system, SK-MEL-2 cells were seeded onto Styela Clava Tunic (SCT)-PF, NaHCO₃-added SCT (SCTN)-PF, and magnesium MP (MMP) and incubated at 37℃ for 24 hr and 48 hr. An MTT assay revealed that cell viability was maintained at a normal level in the SCT-PF culture group at 24 or 48 hr, although it rapidly decreased in the SCTN-PF culture group at 48 hr. Furthermore, the cell viability in the MMP culture group was very similar to that of the control group after incubation for 24 hr and 48 hr. Together, these results suggest the sandwich-type mammalian culture system developed here has the potential for the evaluation of the biocompatibility and toxicity of cells against PF- and MP-form biomaterials.

• Journal of the Korean Society for Railway
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• v.19 no.4
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• pp.417-426
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• 2016

In this study, the optimal welding condition of an extruded AZ61 magnesium alloy plate was investigated through evaluation of the mechanical properties and microstructure in the friction stir welding zones. The friction stir welding conditions considered in this study were the tool rotation speeds of 400, 600, and 800rpm and the welding speeds of 200, 300, and 400mm/min. To evaluate the welding strength, tensile and hardness tests were carried out. Microstructures of the welded regions were examined using optical microscopes. Under a tool rotation speed of 800rpm and welding speed of 200mm/min, the joint showed the best joining properties. The UTS, yield strength, and elongation of the welded region showed values of 79.0%, 65.4%, and 30.1%, respectively, of those of the base metal.

• Korean Journal of Veterinary Research
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• v.45 no.1
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• pp.121-125
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• 2005

The present study was carried out to produce the hematological and blood chemical findings after hypophysectomy in rats. Hypophysectomy was performed by the parapharyngeal method and the sham surgery was performed for the control group. Two weeks after the operation, the body weight of the hypophysectomized and control rats was measured daily for 5 days. We deleted the rats the weight gain of which is less than 5 g during 5 days from the hypophysectomy group. The successful operation rate was approximately 40%. In the hypophysectomized and control rats, their blood samples were collected from posterior vena cava after celiotomy under generally anesthesia with ether. Hematological parameters such as erythrocyte count, leukocyte count, hemoglobin concentration, hematocrit level, and platelet count were determined by Animal Blood Counter. The erythrocyte count, hemoglobin concentration, and hematocrit level were lower significantly (p<0.01), and the leukocyte count was lower significantly (p<0.05) in hypophysectomy group compared with control group. But the plate count did not show significant difference (p>0.05) between hypophysectomy group and control group. Also, blood chemical parameters such as glucose, blood urea nitrogen (BUN), aspartate animotransferase, albumin, total protein, cholesterol, calcium, and magnesium in serum were determined. Except BUN concentration, all parameters were not affected by hypophysectomy. But the BUN concentration was higher significantly (p<0.01) in hypophysectomy group compared with control group.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.534-538
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• 2002

Dissimilar friction stir welding of aluminum (AI) alloy 1050 and magnesium (Mg) alloy AZ31 was successfully done in the limited welding parameters. The dissimilar weld showed good quality and facility compared to conventional fusion weld. Transverse cross section perpendicular to the welding direction had no defects. The weld was divided into base material of Al alloy, an irregular shaped stir zone and base material of Mg alloy. The irregular shaped stir zone was roughly located around the initial weld center. The weld interface near plate surface shifted from initial weld centerline to the advancing side. Hardness profile of the weld was heterogeneous, and the hardness value of the stir zone was raised to about 150 Hv to 250 Hv. The mixed phase was identified to intermetallic compound $Mg_{17}$Al$_{12}$ using x-ray diffraction method, energy dispersive x-ray spectroscopy (EDX) and electron probe micro analysis (EPMA). The formation of intermetallic compound $Mg_{17}$Al$_{12}$ during FSW causes the remarkable increase in hardness value in the stir zone.one.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.72-82
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• 2004

The deformation mechanism of hexagonal close-packed materials is quite complicate including slips and twins. A deformation mechanism, which accounts for both slip and twinning, was investigated for polycrystalline hop materials. The model was developed in a finite element polycrystal model formulated with initial strain method where the stiffness matrix in FEM is based on the elastic modulus. We predicted numerically the texture of Mg alloy(AZ31B) sheet by using FEM based on crystal plasticity theory. Also, we introduced the recrystallized texture employed the maximum energy release theory after rolling. From the numerical study, it was clarified that the shrink twin could not be the main mechanism for shortening of c-axis, because the lattice rotation due to twin rejects fur c-axis to become parallel to ND(normal direction of plate). It was showed that the deformation texture with the pyramidal slip gives the ring type pole figure having hole in the center.

• Design & Manufacturing
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• v.13 no.4
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• pp.17-22
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• 2019

Currently, studies on weight reduction and fuel efficiency increase are the most important topics in the automotive industry and many studies are under way. Among them, weight reduction is the best way to raise fuel efficiency and solve environmental pollution and resource depletion. Materials such as aluminum, magnesium and carbon curing materials can be found in lightweight materials. Among these, research on improvement of bonding technology and manufacturing method of materials and improvement of material properties through study of ultrahigh strength steel sheet is expected to be the biggest part of material weight reduction. As the strength of the ultra hight strength steel sheet increases during forming, it is difficult to obtain the dimensional accuracy as the elastic restoring force increases compared to the hardness or high strength steel sheet. It is known that the spring back phenomenon is affected by various factors depending on the raw material and processing process. We have conducted analytical evaluations and studies to analyze the springback that occurs according to the cross-sectional shape of the ultra high tensile steel sheet.

• Journal of the Korean institute of surface engineering
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• v.47 no.4
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• pp.186-191
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• 2014

Double layer films which consisted of aluminum(Al) and magnesium(Mg) have been prepared by e-beam deposition. The structure, alloy phase, and corrosion resistance of the prepared films were investigated before and after heat treatment. The first (bottom) layer fixed with Al, and the thickness ratio between Al and Mg layers has been changed from 1 : 1 to 5 : 1, respectively. Total thickness of Al-Mg film was fixed at $3{\mu}m$. The cold-rolled steel sheet was used as a substrate. Heat treatment was fulfilled in an nitrogen atmosphere at the temperature of $400^{\circ}C$ for 2, 3 and 10 min. Surface morphology of as-deposited Al-Mg film having Mg top layer showed plate-like structure. The morphology was not changed even after heat treatment. However, cross-sectional morphology of Al-Mg films was drastically changed after heat treatment, especially for the samples heat treated for 10 min. The morphology of as-deposited films showed columnar structure, while featureless structure of the films appeared after heat treatment. The x-ray diffraction data for as-deposited Al-Mg films showed only pure Al and Mg peaks. However, Al-Mg alloy peaks such as $Al_3Mg_2$ and $Al_{12}Mg_{17}$ appeared after heat treatment of the films. It is believed that the formation of Al-Mg alloy phase affected the structure change of Al-Mg film. It was found that the corrosion resistance of Al-Mg film was increased after heat treatment.

• Korean Journal of Metals and Materials
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• v.46 no.4
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• pp.189-198
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• 2008

The changes in microstructure and mechanical properties of AZ31 alloy subjected hot-rolling process were investigated. The AZ31 plates fabricated by horizontal continuous casting process were prepared and have hot-rolled from 30 mm to 1 mm in thickness under different processing conditions. At the rolling temperature of $400^{\circ}C$, little surface and side crack was observed up to 20% reduction rate. As total reduction and reduction rate increase to more than 75% and 20% pass, respectively, Grains were more uniformly refined through overall thickness, and particularly lots of shear bands were appeared to be inclined at less than $20^{\circ}C$ along the rolling direction. Average grain size of less than $5{\mu}m$ and tensile properties of YS ${\geq}$ 250 MPa, UTS ${\geq}$ 300 MPa and El. ${\geq}$ 13% were acquired for hot-rolled AZ31 sheets without post-heat treatment. Maximum intensity of (0002) pole figure was decreased with an increase in reduction rate, indicating the improvement of texture by means of high reduction rate.