• 한국표면공학회지
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• 제34권2호
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• pp.115-124
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• 2001

Gas wiping process of continuously hot-dip galvanized coating on steel strip has noise and coating problems. To improve the qualify of product, characteristics of air flow on the steel surface must be investigated. In this paper, fluid dynamic model of the gas flow is setup and solved numerically using STAR-CD. The effects of edge baffle, distance between steel plane edge and baffle, inlet pressure, and gap between air knife and strip steel surface are investigated, and it is concluded that edge baffle can reduce over-coating and edge built-up.

• 소성∙가공
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• 제28권2호
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• pp.71-76
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• 2019

Corrosion resistance is one of the essential properties required in steel bolts. The various types of coatings are used to improve the corrosion resistance of steel bolts. But, roll formed, subsequently Zn alloy electrodeposited and top coated steel bolt easily takes place the white storage stain or white rust under high humidity condition. To investigate the corrosion resistance of roll formed and subsequently the various types of coated steel bolts, their polarization curves were measured by potentio-dynamic tester in this study. Based on the measured polarization curves, the more times of chromate and top coating on roll formed steel bolt, the higher corrosion resistance was shown. The roll formed steel bolt, which was Zn-Ni electro-deposited, two times chromated, one time inorganic top coated, one time organic top coated and annealed, showed the best corrosion resistance.

• 한국기계가공학회지
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• 제15권6호
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• pp.35-40
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• 2016

In this study, the thermal and fluid dynamic characteristics for the coating process of large-sized water pipes was studied by heating the inside of a pipe directly with a gas burner. Heat and flow analyses were performed on large pipes with various inlet shapes. Using large pipes for coating was shown to be the proper shape for heating large pipes uniformly. This type has a screw with a diameter of 200 mm installed at the inlet to provide a rotational motion to the heating air. The rotational motion resulted in a uniform temperature distribution that ranged from $289.1^{\circ}C$ to $352.1^{\circ}C$ The optimized geometric configuration of the inlet of the pipe successfully and uniformly enhanced the thermal characteristics of the devised temperature limit.

• Tribology and Lubricants
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• 제18권1호
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• pp.42-48
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• 2002

Experiments were conducted to determine the structural dynamic characteristics of bump foil bearing. The housing of the bearing on the journal was driven by two shakers which were used to simulate dynamic forces acting on the bump foil strips. Three different bump foils(Cu-coated bump, silicon bump, viscoelastic bump) are tested and the dynamic coefficients of three bump foils compared, based on the experimental measurements for a wide range of operating conditions. From the test results, the high damping coefficients of viscoelastic bump are achieved and the possibility of the super-bending-critical operation is suggested.

• 한국가시화정보학회지
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• 제16권2호
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• pp.16-22
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• 2018

This study investigates dynamic wetting behaviors of a water droplet placed on surfaces with different wettability and nano-structures. Hydrophobic and hydrophilic properties on as-received silicon wafers were prepared by fabricating thin films of hydrophobic polymer and hydrophilic nanoparticles via layer-by-layer coating. Dynamic advancing contact angle of droplets on the prepared surfaces was measured at various moving velocities of triple contact line with a high-speed video camera. As advancing velocity of triple contact line increased, dynamic advancing contact angle on the as-received silicon and hydrophobic surfaces sharply increased up to $80^{\circ}$ in the range of order of mm/sec whereas the SiO2 nanoparticle-coated hydrophilic surface maintained low contact angles of about $30^{\circ}$ and then it gradually increased in the velocity range of order of hundred mm/sec. The improved dynamic wetting ability observed on the nanostructured hydrophilic surface can benefit the performance of various phase-change heat transfer phenomena under forced convective flow.

• 해양환경안전학회지
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• 제23권4호
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• pp.407-414
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• 2017

본 연구에서는 저온소성 코팅을 적용한 SUS 304 판을 사용하여 고가의 티타늄 판 대체에 대한 성능평가를 수행하였다. 전산유동해석 결과, 저온소성 코팅을 적용한 SUS 304 판은 100 마이크론 두께의 코팅까지는 티타늄 판에 비해 더 뛰어난 열전달 성능을 보이는 것으로 나타났다. 실제 열교환기를 이용하여 열전달 성능에 대한 실험을 한 결과, 코팅을 적용한 SUS 304 판이 티타늄 판에 비해 더 우수한 열전달 성능을 나타냄을 확인하였다. 또한 개방검사를 통해서 판의 부식 및 스케일 생성 정도를 확인하였을 때, 코팅을 적용한 SUS 304 판의 내부식 성능은 티타늄 판과 거의 동등하게 나타났으며, 해수에 의한 스케일의 생성 억제 효과는 코팅을 적용한 SUS 304 판에서 더욱 우수하게 나타났다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.605-608
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• 1998

In this paper, we have investigated the pyroelectric characteristics of the $20\mu\textrm{m}-thick$ $LiTaO_3$ single crystal with black coating by using the nondestructive dynamic method. The $LiTaO_3shows$ the maximum pyroelectric coefficient (${\gamma}$) of $1.56$\times$10-8C/\textrm{cm}^2K$ at 40Hz and the responsivity (Rv) is 488V/W at 2Hz. The noise equivalent power (NEP) is obtained as 3.95$\times$10-10W/√Hz at 40Hz. The detectivity (D*) is obtained divided by the sample area and estimated to be 5.6$\times$108cm√Hz/W at 40Hz. These results, shows that the $LiTaO_3$ single crystals are the best candidates to pyroelectric IR sensors.

• Corrosion Science and Technology
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• 제14권5호
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• pp.226-231
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• 2015

In spite of highly advanced paint coating techniques, corrosion damage of marine metal and alloys increase more and more due to inherent micro-cracks and porosities in coatings formed during the coating process. Furthermore, flowing seawater conditions promote the breakdown of the protective oxide of the materials introducing more oxygen into marine environments, leading to the acceleration of corrosion. Various corrosion protection methods are available to prevent steel from marine corrosion. Cathodic protection is one of the useful corrosion protection methods by which the potential of the corroded metal is intentionally lowered to an immune state having the advantage of providing additional protection barriers to steel exposed to aqueous corrosion or soil corrosion, in addition to the coating. In the present investigation, the effect of flow velocity was examined for the determination of the optimum corrosion protection current density in cathodic protection as well as the corrosion rate of the steel. It is demonstrated from the result that the material corrosion under dynamic flowing conditions seems more prone to corrosion than under static conditions.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.143-146
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• 2002

Unsized AS-4 carbon fibers were etched by RF plasma and then coated via plasma polymerization in order to enhance adhesion to vinyl ester resin. The gases utilized for the plasma etching were Ar, $N_2 and O_2$, while the monomers used for the plasma polymerization coating were acetylene, butadiene and acrylonitrile. The conditions for the plasma etching and the plasma polymerization were optimized by measuring interfacial adhesion with vinyl ester resin via micro-droplet tests. Among the treatment conditions, the combination of Ar plasma etching and acetylene plasma polymerization provided greatly improved interfacial shear strength (IFSS) of 69MPa compared to 43MPa with as-received carbon fiber. Based on the SEM analysis of failure surface and load-displacement curve, it was assume that the failure might be occurred at the carbon fiber and plasma polymer coating. The plasma etched and plasma polymer coated carbon fibers were subjected to analysis with SEM, XPS, FT-IR or Alpha-Step, and dynamic contact angles and tensile strengths were also evaluated. Plasma polymer coatings did not change tensile strength and surface roughness of fibers, but decreased water contact angle except butadiene plasma polymer coating, possibly owing to the functional groups introduced, as evidenced by FT-IR and XPS.

• 한국정밀공학회지
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• 제32권6호
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• pp.577-585
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• 2015

We fabricated multi-scale such as macro-, micro-, and multi-scale wrinkles by using repetitive volume dividing (RVD) method and thermal curing process. Also wrinkle surface was modified with coating of a self-assembled monolayer (SAM). We measured the contact angle of each wrinkled surface, and observed the behavior of droplets on sloping surface. Through experimental study, we found out that the contact angle was much higher in case of multi-scale and SAM coated wrinkles. And micro-scale wrinkle showed a high contact angle comparing with that of macro-scale wrinkle. Dynamic behaviors of a water droplet like sliding velocity on diverse wrinkled surfaces were dependent on their static contact angles. These results showed that hydro-dynamic characteristics were changed depending on the wrinkle structure and the material forming the wrinkle. These dynamic characteristics can be utilized in bio-chip, microfluidics, and many others in order to control easily chemical reactivity.