• Journal of Welding and Joining
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• 제7권4호
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• pp.46-55
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• 1989

Zirconia coatings are performed by the plasma spraying on the substrate of Al-Si alloy. In case of plasma sprayed ceramic coatings, it is important to control properly residual stress occurred during cooling process. Residual stress in coating layer varies with sprayed conditions and is influenced greatly by the coating layer thickness. Surface residual stress due to coating layer thickness is measured by X-ray diffraction method and the residual stress in coating layer is estimated by the deflection of coating layer when the restraint force in substrate was removed. When zirconia was coated on the substrate, tensile residual stress remains on zirconia coated surface layer. The tensile stress is increased to 0.35mm thickness and after 0.45mm thickness it is decreased abrouptly. A thick bond and composite coating reduce the zirconia surface stress and composite coating controls effectively the thick zirconia surface stress.

• Journal of Mechanical Science and Technology
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• 제16권6호
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• pp.757-761
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• 2002

When a layer of cylindrical composite component containing an axisymmetric residual stress state is removed from the inner or outer surface, the dimension of the remaining material changes to balance internal forces. Therefore, in order to machine cylindrical composite components within tolerances, it is important to know dimensional changes caused by residual stress redistribution in the body. In this study, analytical solutions for dimensional changes and the redistribution of residual stresses due to the layer removal from a residually stressed cylindrically orthotropic cylinder were developed. The cylinder was assumed to have axisymmetric radial, tangential and axial residual stresses. The result of this study is useful in cases where the initial residual stress distribution in the component has been measured by a non-destructive technique such as neutron diffraction with no information on the effect of layer removal operation on the dimensional changes.

• 오토저널
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• 제4권2호
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• pp.35-46
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• 1982

This paper deals with residual stress characteristics of ion-nitrided metal which is primarilly concerned with the effects of added carbon content in gas atmosphere. A small optimal amount of carbon content in gas atmosphere increase compound layer thickness, as well as to increase diffusion layer thickness and hardness. The residual stress and deflection of the specimens was measured in various elevated temperature at the surface of ion-nitrided metal and the internal stress distribution was calculated. It is found that compressive residual stress at the compound layer is largest at the compound layer, and decreases as the depth from the surface increases.

• 한국환경과학회지
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• 제10권6호
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• pp.417-422
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• 2001

The vertical structure of atmosphere was observed In investigate the variation of surface ozone concentration by vertical downward mixing of residual ozone in the atmospheric boundary layer at the Busan coastal area. Airsonde and pilot balloon measurements were made at Gamcheondong and the Kimhae airport for April 26~27, 1996. The vertical potential of potential temperature showed a residual layer between 510m and 1800m from 2100LST April 26 to 0900LST April 27. The downward mixing of ozone in the residual layer of the atmospheric boundary layer was confirmed from vertical profile of mixing ratio near 600m in the morning. The thickness of the sea breeze layer was 900m at 1500LST April 26. Thereafter, it become to be lowered with time A low level jet was measured near 900m at 0300LST on April 27 from a pibal measurement. Early morning sharp increase of surface ozone concentration at the Busan coastal area was caused by vertical downward mixing of ozone concentration rather than by photochemical reaction In the atmospheric boundary layer.

• 한국기계가공학회지
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• 제12권1호
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• pp.104-109
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• 2013

In order to apply nano imprint technology in large area process, roller pressing is promising because of its low cost and high productivity. When pressing mold by roller, liquid resin is locally squeezed between mold and substrate. In this study, the main focus is to understand which process parameter affects residual layer. To do this, a simple analytical model was introduced. Especially, we consider the aspect ratio of patterns as essential cause of variation of the thickness in the equation. As a result, when the aspect ratio of pattern in the mold increases, the thickness of residual layer also increases. In conclusion, we show that the uniformity of residual layer could be accomplished by the control of velocity and pressing force in roller pressing imprint process.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.61-63
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• 2001

Residual stress distribution in injection-molded short fiber composites was determined using layer-removal method. Polysterene with 3 vol% carbon fibers was injection-molded into the tensile specimen. With milling machine layer-removal process was conducted and the curvature data were acquired. Treuting and Read analysis which is assuming isotropic material, and White analysis considering anisotropy due to the fiber orientation were used to calculate residual stress of the flow direction through the thickness direction and compared with each other.

• 반도체디스플레이기술학회지
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• 제12권2호
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• pp.79-84
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• 2013

Nanoimprint lithography (NIL) is the next generation photolithography process in which the photoresist is dispensed onto the substrate in its liquid form and then imprinted and cured into a desired pattern instead of using traditional optical system. There have been considerable attentions on NIL due to its potential abilities that enable cost-effective and high-throughput nanofabrication to the display device and semiconductor industry. Although one of the current major research trends of NIL is large-area patterning, the technical difficulties to keep the uniformity of the residual layer become severer as the imprinting area increases more and more. In this paper, with the rolling type imprinting process, a mold, placed upon the $2^{nd}$ generation TFT-LCD glass sized substrate($370{\times}470mm^2$), is rolled by a rubber roller to achieve a uniform residual layer. The prediction of residual layer thickness of the photoresist by rolling of the rubber roller is crucial to design the rolling type imprinting process, determine the rubber roller operation conditions-mpressing force & feeding speed, operate smoothly the following etching process, and so forth. First, using the elasticity theory of contact problem and the empirical equation of rubber hardness, the contact length between rubber roller and mold is calculated with consideration of the shape and hardness of rubber roller and the pressing force to rubber roller. Next, using the squeeze flow theory to photoresist flow, the residual layer thickness of the photoresist is calculated with information of the viscosity and initial layer thickness of photoresist, the shape of mold pattern, feeding speed of rubber roller, and the contact length between rubber roller and mold previously calculated. Last, the effects of rubber roller operation conditions, impressing force & feeding speed, on the residual layer thickness are analyzed with consideration of the shape and hardness of rubber roller.

• 한국세라믹학회지
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• 제48권5호
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• pp.458-462
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• 2011

The strength of ceramic was improved by lamination by suppressing the propagation of cracks with compressive residual stress in the face layer of the laminate. Hot pressed SiAlON+SiC/SiC/SiAlON+SiC laminate discs were fabricated for tailored residual stress. The residual stress in this laminate was studied by X-ray diffraction (XRD). There was considerable compressive residual stress in the face layer. A Finite Element Analysis (FEA) was performed to support the measured XRD results and to determine the stress field in the laminate. The residual stress measured by XRD had satisfactory agreement with the analytically calculated and FEA values. The measured value by XRD was -385 ${\pm}$ 20 MPa over most of the face layer. The calculated and FEA values were -386 MPa and -371MPa, respectively. FEA also showed significantly modified stresses and the maximum tensile stress near the edge region which are possible crack generators in the presence of flaws or contact damage.

• 한국해양공학회지
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• 제10권2호
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• pp.88-97
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• 1996

The pupose of this study is to improve the mechanical properies and to evaluate the residual stresses of flame-sprayed Alumina ceramic coating layer. The first work in this study is to investigate the effects of strengthening heat treatments on the mechanical properties of coating layer. Strengthening heat treatments for sprayed specimens were carried out in vaccum furnace. The mechanical properties such as microhardness, thermal shock resistance, adhesive strength and erosion resistance were tested for the sprayed specimens after strengthening heat treatments. And it was clear that the mechanical properties of coating layer were much improved by strengthening heat treatments. The second work in this study is to evalute the residual stresses in coating lsyer by numerical analysis. FDM and FEM were used to analyze temperature distribution and residul stresses in coating layer. It was proved that are tensile stresses in coating layer and that residual stresses can be controlled by the appropriate selection of the spraying parameters such as preheat temperature, coating thickness and bond coat thickness.

• Tribology and Lubricants
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• 제26권5호
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• pp.297-302
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• 2010

This study is focused on the resin layer formation of UV imprinting process by changing imprinting pressure and period. The mold shape is made for the process of window open over the pattern transfer area and the imprinting period is assigned as the time just before the UV light curing. The residual layer is measured by changing the imprinting period and pressure magnitude, and the measured data of residual layer provides useful information for the design of the process conditions of imprinting processes.