• 공업화학
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• 제5권6호
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• pp.1056-1061
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• 1994

$80^{\circ}C$에서 열처리하거나, $80^{\circ}C$와 상대습도 85%인 습도 조건에서 처리한 황동이 피복된 강선 코드의 표면 상태와 고무와 접착 성질을 조사하였다. 열처리로 황동의 산화가 진행되었으며, 습윤처리 후에는 더 심하게 산화되었다. 처리기간이 길어질수록 전처리한 코드의 접착 성질이 나빠졌으며, 고무부착 정도가 심하게 저하되었다. 황동 피복층의 산화로 인한 코드의 접착 성질 저하를 산화아연층의 과도한 성장과 연계지어 설명하였다.

• 한국레이저가공학회지
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• 제11권4호
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• pp.21-28
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• 2008

Remote Laser welding technology for manufacturing automotive body is studied. Laser welding and industrial robot systems are used for the robot based laser welding system. The laser system is used 1.6kW Fiber laser(YLR-1600) of IPG. The robot system is used HX130-02 of Hyundai Heavy Industry(payload : 130kg). The robot based laser welding system is equipped with laser scanner system for remote laser welding. The welding joints of steel plate and steel plate coated with zinc are butt and lapped joints. The quality test of the laser welding are through the observation the shape of bead on plate and cross-section of welding part. During past three years the laser system, 4kW Nd:YAG laser (HL4006D) of Trumpf was used and the robot system, IRB6400R of ABB (payload:120kg) was used. The new laser source, robot and laser scanner system are used to increase the processing speed and to improve the process efficiency. This paper introduces the robot based remote laser welding system to resolve the limited welding speed and accuracy of the conventional laser welding system.

• Journal of Welding and Joining
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• 제19권1호
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• pp.58-64
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• 2001

The initiation and propagation lives of fatigue crack were studied for spot weldments composed of cold rolled steel plates(SPC$\times$SPC) and galvanized steel plates(GA$\times$GA) using DC potential drop method(DCPDM). Through the various test results, it was known that the fatigue crack initiation and propagation behaviors in all specimens could be definitely detected by DCPDM. The fatigue crack initiation life( $N_{i}$) detected by DCPDM in SPC$\times$SPC and GA$\times$GA spot weldments increased as the welding current and the nugget diameter( $N_{d}$) increased. The fatigue crack propagation life($\Delta$ $N_{f-i}$) declined as the difference of $N_{i}$ and the fatigue fracture life( $N_{f}$) also increased according to the decrease of fatigue load, $\Delta$P and the increase of nugget diameter. In the same spot weldments, the increase of nugget diameter came to increase fatigue crack propagation life owing to a decrease of stress concentration in front of nugget, especially the increasing extent for GA$\times$GA spot weldment was very high. In the welding current 6kA, $N_{f}$ for GA$\times$GA spot weldment decreased more than that of SPC$\times$SPC specimen due to zinc layer coated in steel plate and undersized nugget diameter. On the other hand, in 8kA and 10kA, the GA$\times$GA spot weldment showed higher $N_{f}$ in spite of lower $N_{i}$, than that of SPC$\times$SPC specimen except 3,000N fatigue load.ue load. load.d.

• Structural Engineering and Mechanics
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• 제32권4호
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• pp.477-488
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• 2009

A slip critical joint has various values to adopt the proper slip coefficient in various conditions of faying surfaces in the following codes: AISC, AIJ and Eurocode 3. However, the Korean Building Code still regulates the unique slip coefficient, 0.45, regardless of the diverse faying conditions. In this study, the slip resistance test, including five kinds of surface treatments were conducted to obtain the proper slip coefficients available to steel plate KS SM490A. The faying surfaces were comprised of a clean mill, rust, red lead paint, zinc primer, and shot blast treatment. The candidates for high strength bolts were torque-shear bolts, torque-shear bolts with zinc coating, and ASTM A490 bolts. Based on the test results, the specimens with a shot blasted surface and rusted surface exhibited $k_s$, 0.61, and 0.5, respectively. It is recommended that the specimens with zinc primer exhibit $k_s{\geq}0.40$. The clean mill treated surface had prominently lower values, 0.27. For red lead painted treatment, the thickness of the coating affects the determinant of slip coefficient, so it is necessary to establish a minimum $k_s$ of 0.2, with a coating thickness of 65 ${\mu}m$. During 1,000 hours of relaxation, the uncoated surfaces exhibited the loss of clamping force behind 3%, while the coated surfaces within a certain limited thickness exhibited the loss of clamping within a range of 4.71% and 8.37%.

• Composites Research
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• 제37권3호
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• pp.238-245
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• 2024

본 연구에서는 강관의 효율적 유지관리를 위한 모니터링 시스템 개발 연구의 일환으로 개질 폴리에틸렌 코팅 처리된 강관의 성능 평가를 위한 실험적 연구를 수행하였다. 기존 방식인 기계적 전처리 코팅의 경우 확관시 폴리에틸렌 부착이 저하되는 현상이 발생하여 이를 해결하고자 칼슘 혼입 인산 아연 피막을 활용한 화학적 전처리 공정이 적용되었다. SEM 및 EDX 분석결과, Zn/Ca 비 1.0에서 가장 치밀한 구조가 확인되었다. 또한, 확관 시의 코팅 이탈 방지를 위한 그라프트 처리 무수말레산을 기반으로 엘라스토머, 금속산화물, 블로킹방지제, 슬립제를 각기 다른 조합으로 혼입하여 개질된 폴리에틸렌 코팅 강관에 대한 부착 및 연신율 평가를 실시하였다. 그 결과, 모든 개질 재료를 혼입한 시험체(S4)에서 금속산화물만 혼입한 시험체(S2)대비 25% 이상 향상된 성능을 확인하였다. 마지막으로, 공정이 완료된 코팅 파이프에 대하여 표면부 코팅 손상 방지를 위한 파이프 고정 부속 일부인 쐐기형 소켓링과 이탈 방지 압륜을 개발하고 성능평가를 수행하였다.

• Corrosion Science and Technology
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• 제9권4호
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• pp.147-152
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• 2010

Conventional paints for conversion coating applications in steel production derived mainly from water-based polymer dispersions containing several additives actually show good general performance, but suffer from poor scratch and abrasion resistance during use. The reason for this is because the relatively soft organic binder matrix dominates the mechanical surface properties. In order to maintain the high quality and decorative function of coated steel sheets, the mechanical performance of the surface needs to be improved significantly. In fact the wear resistance should be enhanced without affecting the optical appearance of the coatings by using appropriate nanoparticulate additives. In this direction, nanocomposite coating compositions (Nanomer$^{(R)}$) have been derived from water-based polymer dispersions with an increasing amount of surface-modified nanoparticles in aqueous dispersion in order to monitor the effect of degree of filling with rigid nanoparticles. The surface of nanoparticles has been modified for optimum compatibility with the polymer matrix in order to achieve homogeneous nanoparticle dispersion over the matrix. This approach has been extended in such a way that a more expanded hybrid network has been condensed on the nanoparticle surface by a hydrolytic condensation reaction in addition to the quasi-monolayer type small molecular surface modification. It was expected that this additional modification will lead to more intensive cross-linking in coating systems resulting in further improved scratch-resistance compared to simple addition of nanoparticles with quasi-monolayer surface modification. The resulting compositions have been coated on zinc-galvanized steel and cured. The wear resistance and the corrosion protection of the modified coating systems have been tested in dependence on the compositional change, the type of surface modification as well as the mixing conditions with different shear forces. It has been found out that for loading levels up to 50 wt.-% nanoparticles, the mechanical wear resistance remains almost unaffected compared to the unmodified resin. In addition, the corrosion resistance remained unaffected even after $180^{\circ}$ bending test showing that the flexibility of coating was not decreased by nanoparticle addition. Electron microscopy showed that the inorganic nanoparticles do not penetrate into the organic resin droplets during the mixing process but rather formed agglomerates outside the polymer droplet phase resulting in quite moderate cross linking while curing, because of viscosity. The proposed mechanisms of composite formation and cross linking could explain the poor effect regarding improvement of mechanical wear resistance and help to set up new synthesis strategies for improved nanocomposite morphologies, which should provide increased wear resistance.

• 한국해양공학회지
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• 제24권5호
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• pp.67-74
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• 2010

Chromate conversion coating is a coating technique used to passivate aluminum, zinc, cadmium, copper, silver, magnesium, tin, and their alloys to slow corrosion. The process uses various toxic chromium compounds, which may include hexavalent chromium. The industry is developing less toxic alternatives in order to comply with substance restriction legislation, such as RoHS. One alternative is to develop a Cr-free coating solution. In this study, eco-friendly, Cr-free solutions (urethane solution S-700, organic/inorganic solution with Si LRO-317) were used. Test specimens were dried in a drying oven at $190^{\circ}C$ for 3, 5, 7, and 9 minutes. Corrosion resistance was evaluated using a salt spray test for 72 hours. The results show that the optimum corrosion resistance was achieved at $190^{\circ}C$ for five minutes for EGI and three or five minutes for HDGI, respectively. The adhesive properties of the two types of coating solutions were superior regardless of drying time.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.181-186
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• 2002

Laser welding application for car body manufacturing has many advantages in the stiffness and the lightness of vehicle, the productivity of assembly line, and the degree of freedom in design. This presentation will express the innovation of car body manufacturing including parameter optimization, process modeling, and system integration. In this application the investment for systems was cut down dramatically by real time switching over the laser path between two welding stations. Points of technical discussion are as follows: optimization of parameters such as laser power, robot speed and trajectory, compact and useful design of jig & fixture to assure welding quality for 3 sheet-layer zinc-coated steel, system integration between 4kW Nd:YAG laser device and the other systems, on-line real time welding quality monitoring system, perfect safety standards for high power laser, minimization of consumption costs such as arc lamp, protective glass for optic, etc. Laser welding has found a place on Hyundai's production plant in conjunction with the startup of mass production of new sports car, and this production system is the result of a collaboration of its engineers. Outer side sheets are joined to inner side sheets by 122 stitch welds totally. And the length is about 2.4meter.

• KIEAE Journal
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• 제4권2호
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• pp.65-72
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• 2004

Ecological architecture enables people to recycle and reuse architectural resources within the category of ecosystem and also to minimize the effect on environment in a whole process, including architectural planning, usage and exhaustion to use sustainable energies. Rammed earth wall construction method utilized in EcoCenter located in Crystalwaters ecological village in Austrailia is a good example, which maximizes its advantages and also covers its limits to use soil and wood as structural resources. In a case of wood, they used non-treated timber to minimize environmental load and utilized used materials in openings. In the roofs, aluminum coated steel which is plated with zinc collects rain effectively even though it is not regenerable. Nontoxic finishes and insulation in floor and ceiling with used papers are able to minimize its environmental load. Solar energy system applied in EcoCenter enables them to market extra energy with electricity companies as well as support needs of its own buildings to utilize photovoltaic panel system with PV panels. Passive solar system is planned effectively in heating and cooling to apply regenerative walls in a use of rammed earth wall construction and natural ventilation systems through openings.

• 한국산학기술학회논문지
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• 제14권2호
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• pp.535-541
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• 2013

본 연구에서는 아연도금강관 용접에 용접 전류, 전압과 보호가스가 용접 비드 형상과 미세조직과 경도에 미치는 영향을 조사하였다. 전압, 전류과 보호가스 종류 및 조성의 변화가 용접 비드의 높이와 너비, 용입깊이에 영향을 미침을 확인하였다. 비드높이에는 보호가스 Ar 가스, 용입에는 $CO_2$ 가스, 그리고 비드너비에는 Ar+$O_2$ 가스가 가장 큰 영향을 미쳤다. 용접부의 경도에서는 Ar+10% $O_2$ 와 Ar+20% $CO_2$ 가스 사용 시 결정립계 페라이트와 다각형 페라이트가 생성되어 낮았으며, Ar+2% $O_2$ 가스를 사용했을 때는 아시큘러 페라이트와 베이나이트적 페라이트와 사이드플레이트 페라이트가 생성되어 경도가 높았다.