• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.96-99
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• 2011

Fiber coatings are essential in optical fiber manufacturing, since they provide the protective layers from the surface damages and the adequate fiber strength. Flow and temperature fields of coating liquid in a fiber coating applicator are numerically investigated by using a commercial CFD software. The main focus of this computational study is on the thermal effects by viscous dissipation and the effects of coating supply temperature on the final fiber coating thickness. The numerical results reveal that the thermal effects play a major role in the high-speed optical fiber coating process and give substantial influences on the determination of coating thickness. Changing the supply temperature of coating liquid is found to relieve the radial variation of coating liquid viscosity in the coating die and it can be an effective way to control the fiber coating thickness.

• 한국세라믹학회지
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• 제34권5호
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• pp.544-551
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• 1997

We tried to improve the coating capability of the coating material using an additive(hexagonal cystalline graphite) of 2%, 3%, 4% and 6% under various pouring temperature for the easy isolation of sand and coating material from the final product. As a result in case of using a 2% and 3% additive generally no burning state has been occurred under the low pouring temperature, but it has been gradually increased with the pouring temperature. On the other hand in case of using a 4% and 6% additive there has been no burning state through out the whole pouring temperature. From this result we could see that the best state of the final product without sand and coating material could generally be obtained if 4% and/or 6% of the crystalline graphite and the pouring temperature of 140$0^{\circ}C$$\pm$5$^{\circ}C$ would be used.

• Tribology and Lubricants
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• 제35권6호
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• pp.362-368
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• 2019

In this study, mechanical and tribological properties were investigated by varying the process temperature (50, 100, 125 and 150℃) to reduce internal stress. The internal stress reduction by thermal dissociation ta-C coating film with increasing temperature is confirmed through the curvature radius of the ta-C coating according to the temperature of the SUS plate. As the coating temperature increased, the mechanical properties (hardness, modulus, toughness) deteriorated, which is in agreement with the Raman analysis results. As the temperature increased, the sp² phase ratio increased owing to the dissociation of the sp³ phase. The friction and wear properties are related to the process temperature during ta-C coating. Low friction and wear properties are observed in high hardness samples manufactured at 50℃, and wear resistance properties decreased with increasing temperature. The contact area is expected to increase owing to the decrease of hardness(72 GPa to 39 GPa) and fracture toughness with increasing temperature which accelerated wear because of the debris generated. It was confirmed that at process temperature of over than 100℃, the bond structure of the carbon film changed, and the effect of excellent internal stress was reduced. However, the wear resistance simultaneously decreased owing to the reduction in fracture toughness. Therefore, in order to increase industrial utilization, optimum temperature conditions that reduce internal stress and retain mechanical properties.

• 한국산학기술학회논문지
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• 제1권1호
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• pp.49-54
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• 2000

Calorizing(또는 Aluminizing)에서 코팅분말의 입자크기 및 코팅온도가 금속표면에 형성된 코팅 층의 특성에 미치는 영향을 SEM과 EDXS를 사용하여 자세히 고찰하였다. 코팅분말은 입자크기별로 3단계로 분리하여 사용하였으며 코팅온도는 950℃ 와 980℃로 변화하였다. Calorizing 처리는 팩 세멘테이션 방법을 사용하여 아르곤 분위기에서 5시간 동안 행하였다. Calorizing 처리 결과 코팅분말의 입자크기가 감소하고 코팅온도가 증가할수록 코팅 층의 두께와 코팅 층에서의 알루미늄의 함량이 증가하였다. 또한 오팅분말의 크기가 작은 경우(150-200 mesh) 코팅 층 표면에 형성된 기공이 현저히 감소하였고 표면의 균일성도 우수함을 알 수 있었다.

• 반도체디스플레이기술학회지
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• 제16권4호
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• pp.91-96
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• 2017

In this computational study of optical fiber manufacturing, WOW (wet-on-wet) double coating process on freshly drawn glass fiber has been numerical modelled and simulated using a simplified geometry of typical optical fiber coating apparatus. The numerical domain includes primary and secondary coating dies along with secondary coating cup and the interface between primary and secondary coating liquids are investigated using level set method. Coating liquid viscosity is an important parameter and its dependence on temperature is also considered. Since there would be possibility for pressure and temperature of primary coating liquid to be increased substantially at high fiber drawing speed, the effects of increased pressure and temperature of primary coating liquid are examined on flow patterns of coating liquids in secondary coating cup. In case that both pressure and temperature of primary coating liquid are high enough, liquid interface becomes noticeably unstable and this flow instability could adversely affect the uniform coatings and final quality of produced optical fiber.

• 공업화학
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• 제10권7호
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• pp.1061-1065
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• 1999

Calorizing 처리에서 코팅분말의 입자크기 및 코팅온도가 금속표면에 형성된 코팅층의 두께에 미치는 영향을 XRD, SEM, 및 EDXS를 사용하여 고찰하였다. 코팅분말은 입자크기별로 3단계로 분리하였으며 코팅온도는 $950^{\circ}C$와 $980^{\circ}C$로 변화하였다. Calorizing 처리는 공기 및 아르곤 분위기에서 5시간 동안 행하였다. XRD 결과 공기분위기의 calorizing 처리과정에서 금속산화물($Al_2O_3$)과 질화물(AlN)이 형성됨을 관찰하였다. 공기 및 아르곤 분위기의 calorizing 처리 결과 코팅분말의 입자크기가 감소하고 코팅온도가 증가할수록 코팅층의 두께와 코팅층에서의 알루미늄의 함량이 증가함을 알 수 있었다.

• 한국산학기술학회논문지
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• 제20권8호
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• pp.425-430
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• 2019

아연말 코팅은 친환경성 및 고성능으로 인하여 널리 사용되고 있다. 일반적으로 코팅온도가 코팅층 두께 및 코팅 품질을 결정하는 주요한 요소이며 아연말 코팅의 경우에도 코팅 룸 내 균일하며 적절한 코팅온도가 요구된다. 본 연구에서는 일반적으로 사용하는 자연대류 상태에서의 아연말 스프레이 코팅 룸의 온도 분포를 해석하기 위해 룸 내부의 공기 유동을 포함하는 열 유동 전산 시뮬레이션을 수행하였다. 3차원 CAD 프로그램인 SolidWorks를 이용하여 스프레이 코팅 룸 전체와 예열실과 건조실을 모두 고려한 모델링을 수행하였으며 ANSYS의 FLUENT 프로그램을 이용하여 열 유동연성 해석을 수행하였다. 해석 결과 스프레이 코팅 룸에서의 온도 분포 특성을 파악할 수 있었으며, 현재의 상태로는 목표 온도 값인 $25^{\circ}C$에 미달하고 있었음을 알 수 있었다. 이에 두 가지 다른 경계조건 (히터를 추가하는 방법과 현재 상태에서 Open 부분을 닫는 방법) 에 대해 열 유동 시뮬레이션을 수행하였으며, 시뮬레이션 결과 히터를 추가하기보다는 Open된 부분을 닫는 방법이 더 좋은 결과를 나타내었다.

• Corrosion Science and Technology
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• 제4권2호
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• pp.60-63
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• 2005

A high temperature resistant coating has been developed, which is mainly for heavy oil production pipes deserved the serious corrosion. The coating has excellent physical and mechanical performance and corrosion resistance at room and high temperature. In order to simulate the underground working condition of heavy oil pipes, the heat resistance of the high temperature resistant coating has been studied. The development and a study on the heat resistance of the DHT high temperature resistance coating have been introduced in this paper.

• 항공우주시스템공학회지
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• 제2권2호
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• pp.42-45
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• 2008

Under the non-operating exposure condition in the hot area, the T-50 cockpit temperature is expected over the requirement according to T-50 environmental criteria. So it is necessary to protect the cockpit from the high temperature condition during the non-operating exposure because the high temperature of the cockpit may result in the cockpit equipment malfunction. In this study, the transparency coating is selected as the method for protecting the cockpit from the high temperature exposure and analyzed the effect on the cockpit heat load attenuation. Some kinds of cockpit coating were reviewed and selected and the analysis was performed about the effect before and after coating application under 1% hot day condition based on the T-50 FSD hot soaking test data. The result of analysis show transparency coating is so effective to attenuate the heat load of T-50 cockpit.

• 한국주조공학회지
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• 제10권1호
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• pp.31-42
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• 1990

The full mould casting process in one of the newly developed techniques which has many advantages. Unbonded sand mould has been prepared for the major mould and $CO^2$ gas mould has been used occasionally for comparison. Patterns were built up with expanded polystyrene and coated with three different materials. Silica, graphite and zircon were used for the coating layer. The effects on fluidity and temperature loss of molten metals were investigated. The molten metals were Al-5% Si alloy, Cu-30% Zn alloy and gray iron of approximately 4.0% of carbon equivalent. Experimental variables were runner section area, superheat, sprue height, coating materials, coating thickness and apparent density of EPS pattern. The effects of coating materials on fluidity and temperature loss of the molten metals during transient pouring are summarized as follows : As runner section area, superheat and sprue height increased, fluidity increased. Temperature loss decreased as runner section area and sprue height increased. However, reversed effects were observed in the case of superheat increment. The coating materials decreased the fluidity of each alloy in the order of silica, graphite and zircon. Zircon brought to the highest temperature loss among the coating materials used. The fluidity increased in the order gray iron, Cu-30% Zn and Al-5% Si alloy while temperature loss in the reverse order. Especially in case of reduced pressure process, the fluidity was increased apparently. Al-5% Si alloy showed the lowest temperature loss among the alloys. The increment of the apparent density of EPS pattern resulted in the fluidity decrease and temperature loss increase. The relation between fluidity and temperature loss of each alloy can be expressed by the following equation within the coating thickness limit of 0.5-1.5㎜. F^*={\frac{a}{T^*-b}}-c$ where, $F^*$ : fluidity in the Full mould, $T^*$ : temperature loss in the mould. a : parameter for full mould. b, c : constants.