• 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.

• 한국표면공학회지
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• 제15권2호
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• pp.69-76
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• 1982

With a view to manufacturing membranes for separation of gas mixtures, Al foils were anodized in a 2% oxalic-acid electrolyte at 40V and 80V. When anodizing was completed and Barrier layer existed at the extreme back site of the foil, the anodized foil was made to react with only electrolyte, with switching off the electric power. When the size and density of pores were changed through voltage change, the membr-anes did not show large difference in the permeability. Reacting with electrolyte, the existing Barrier layer turns into porous layer. During this process, several small pores grow from one relatively large pore, getting to the back site. The number and size of the small pores getting to the back surface increase as time passing. This change of Barrier layer into porous layer is thought to be directly related to the permeability change of the membranes. The selectivity of an anodized Al membrane was not related to the voltage change, and was high, being similar to the theoretical selctivity of metallic membranes, according to my observation.

• 한국시뮬레이션학회논문지
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• 제26권1호
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• pp.69-75
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• 2017

MCP(Multi-chip Package)는 두 개 이상의 Chip을 적층하여 하나의 패키지로 합친 제품이다. MCP를 만들기 위해서는 두 개 이상의 Chip이 동일한 Substrate에 적층되기 때문에 다수의 조립 공정이 필요하다. Package 공정에서는 Lot들이 동일한 특성을 가지는 Chip으로 구성되고 MCP를 구성하는 Chip의 특성은 Layer sequence에 의해 결정된다. MCP 생산 공정에서 WIP Balance 뿐만 아니라 Throughput을 달성하기 위해서는 Chip의 Layer sequence가 중요하다. 본 논문에서는 Chip들의 Layer sequence의 제약 조건을 고려한 스케쥴링 방법론을 제안한다.

• 한국CDE학회논문집
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• 제7권3호
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• pp.148-156
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• 2002

Most Rapid Prototyping (RP) processes adopt a solid Computer Aided Design (CAD) model, which will be sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; and eventually the stacked layers from a physical part of the model. A new RP process, the transfer-type Variable Lamination Manufacturing process using expandable polystyrene foam sheet (VLM-ST), has been developed to reduce building time and to improve the surface finish of parts with the thick layers and a sloping surface. This paper describes the generation of Unit Shape Layer (USL), the cutting path data of the linen. hotwire cutter for the VLM-ST process. USL is a three-dimensional layer with a thickness of more than 1 mm and a side slope, and it is the basic unit of cutting and building in the VLM-ST process. USL includes data such as layer thickness, positional coordinates, side angles of each layer, hotwire cutting speed, the heat input to the hotwire, and reference shape. The procedure of generating USL is as follows: (1)Generation of the mid-slice from the CAD model, (2)Conversion of the mid-slice into a simply connected domain, (3)Generation to the reference shape for the mid-slice, (4)Calculation of the rotation angle of the hotwire of the cutting system.

• 한국표면공학회지
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• 제52권6호
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• pp.316-320
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• 2019

The effect of boronizing on mechanical properties including wear behavior and hardness of Inconel 625 superalloy were investigated. The cross-section observation demonstrated that boronized samples were composed of multi-phase boride layer (Cr_xB_x, Ni₂B), diffusion layer, and substrate. The boride and diffusion layers were increased with increasing treatment temperature and holding time. However, Cr_xB_x layer was partially peeled off when it treated 1000℃. Subsequently, boride layer was completely separated from substrate with increasing temperature and time. A partial peeling of Cr_xB_x layer is not noticeably degraded mechanical properties. In particular, friction coefficient and wear resistance were enhanced in lack of Cr_xB_x phase. Therefore, these results suggest that a Ni₂B phase mainly contribute to wear behavior on boronized Inconel 625 superalloy.

• 열처리공학회지
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• 제21권4호
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• pp.183-188
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• 2008

Hot press forming allows geometrically complicated parts to be formed from sheet and the rapid cooling hardens them to extremely high strength. The main purpose of this research is to characterize Al coated layer in Al coated boron steel during hot press forming. For the hot press hardening experiment, test specimens were heated up to $810{\sim}930^{\circ}C$ and held for 3, 6 and 9 minutes, respectively. And then, some specimens were press hardened and others were air-cooled without any pressing for the comparison purpose. Al coated layer shows four distinct micro-structural regions of interest; diffusion zone, Al-Fe zone(I) low-Al zone(LAZ) and Al-Fe zone(II). Band-like LAZ is clearly shown at temperature ranges of $810{\sim}870^{\circ}C$ and sparsely dispersed at temperature higher than 900oC. The micro-cracking behavior in the Al coated layer during forming were also analyzed by bending and deep drawing tests. The strain concentration in softer LAZ is found to be closely related with micro-cracking and exfoliation in coated layer during forming.

• Archives of Metallurgy and Materials
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• 제64권2호
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• pp.607-611
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• 2019

Thermal/cold spray deposition were used for additive manufacture of oxide dispersion strengthened (ODS) steel layers. Mechanically alloyed F/M ODS steel powders (Fe(bal.)-10Cr-1Mo-0.25Ti-0.35Y2O3 in wt.%) were sprayed by a high velocity oxygen fuel (HVOF) and cold spray methods. HVOF, as a thermal method, was used for manufacturing a 1 mm-thick ODS steel layer with a ~95% density. The source to objective distance (SOD) and feeding rate were controlled to achieve sound manufacturing. Y₂Ti₂O₇ nano-particles were preserved in the HVOF sprayed layer; however, unexpected Cr₂O₃ phases were frequently observed at the boundary area of the powders. A cold spray was used for manufacturing the Cr₂O₃-free layer and showed great feasibility. The density and yield of the cold spray were roughly 80% and 45%, respectively. The softening of ODS powders before the cold spray was conducted using a tube furnace of up to 1200℃. Microstructural characteristics of the cold sprayed layer were investigated by electron back-scattered diffraction (EBSD), the uniformity of deformation amount inside powders was observed.

• 한국정밀공학회지
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• 제15권7호
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• pp.85-90
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• 1998

The business of manufacturing is increasingly becoming time-compressing, precise and long-life oriented, owing to various needs from the consumers and harsh global competition. With the emergence of the layer laminate manufacturing method, it is possible to produce prototypes directly from 3D CAD and additive process, the production time and cost have shortened dramatically. However there are some problems like surface-step, dimensional deviation and warp. A newly developed powder casting is suitable for rapid-manufacturing metallic tools. Powder casting can serve as a promising rapid tooling method because of high density characteristics and low dimensional shrinkage below 0.1％ during sintering and infiltration. By this process, we have realized significant time savings bypassing the wait for prototype tooling and cost savings eliminating the expense of conventional prototype tooling process.

• 열처리공학회지
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• 제37권2호
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• pp.49-57
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• 2024

We investigated the changes in microstructure and surface roughness of the compound layer of GC250D gray cast iron, commonly used in brake discs, during gas nitriding. The gas atmosphere of the nitriding process was controlled with a hydrogen partial pressure of 49.5%, and the process was conducted at a nitriding temperature of 520℃ with various process times. As the nitriding process time of the GC250D material increased, both the depth of hardening and the thickness of the compound layer increased, with a maximum surface hardness of approximately 1265 HV_0.1 was measured. Additionally, the surface roughness increased with the process time. Phase analysis of the compound layer revealed an increase in the proportion of the γ' phase as the nitriding process time increased. Changes in the formation of the compound layer were observed depending on the orientation of graphite within the material, leading to the formation of wedges. Therefore, the increase in surface roughness appears to be attributed to the uneven compounds, the expansion of the compound layer and wedges formed on the surface during the nitriding process.

• 보존과학회지
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• 제38권1호
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• pp.45-54
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• 2022

This study examined the production technique of bracket murals in Daeungjeon Hall, Gaeamsa Temple by conducting a analysis of their wall structure, material characteristics, and painting layers. Wall was a single-branch structure with support layer, middle layer, finishing layer, and painting layer. The support layer, middle layer and finishing layer, were produced by mixing sand (quartz, feldspars etc.), and loess. The ratio of above medium sand to below fine sand was approximately 0.7 : 9.3 in the support layer, 4 : 6 in the middle layer and 6 : 4 in the finishing layer, which had a more percentage of above medium sand than the support layer. The analysis of the painting layer showed that natural soil pigment was used to establish a relatively ground layer of up to 50 ㎛, and pigments such as Lead sulfate, atacamite and mercury sulfide were painted on top of the layer. This study's results confirmed that the bracket mural paintings in Gaeamsa Temple are within the category of the production style of murals during the Joseon period. However, the points that the middle layer was formed several times, the significant difference in particle size distribution between the wall, and the absence of chopped straw in the support layer are a feature of bracket mural paintings in Gaeamsa Temple. These properties of murals as material and structure may be viewed for correlation with the degree of damage to wall structure of mural painting and would serve as an important reference to diagnosis the conservation conditions of murals or prepare conservation treatments.