• 대한기계학회논문집A
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• 제30권11호
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• pp.1425-1432
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• 2006

Coating layers on a coated sheet steel frequently affect distributions of strain rate of sheets and deteriorate the frictional characteristics between sheets and tools in sheet metal forming. Thus, it is important to identify the deformation behavior of these coatings to ensure the success of the sheet forming operation. In this study, the technique using nano-indentation test, FE-simulation and Artificial Neural Network(ANN) were proposed to determine the power law stress-strain behavior of coating layer and the power law behavior of extracted coating layers was examined using FE-simulation of drawing and nano-indentation process. Also, deep drawing test was performed to estimate the formability and frictional characteristic of coated sheet, which was calculated using the linear relationship between drawing force and blank holding force obtained from the deep drawing test. FE-simulations of the drawing process were respectively carried out for single-behavior FE-model having one stress-strain behavior and for layer-behavior FE-model which consist of coating and substrate separately. The results of simulations showed that layer-behavior model can predict drawing forces with more accuracy in comparison with single-behavior model. Also, mean friction coefficients used in FE-simulation signify the value that can occur maximum drawing force in a drawing test.

• Tribology and Lubricants
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• 제36권6호
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• pp.350-358
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• 2020

Hot stamping is an effective and suitable process widely used in automotive applications, though critical issues such as the transfer of the coating materials and build-up of these materials on tool surfaces have been encountered. Past researches figured out the resultant wear phenomenon using pin-on-disc and drawing (for example, strip drawing and deep drawing) methods to mimic the process and analyzed the wear behavior with respect to the influencing factors such as surface coating, load, and roughness. Although the pin-on-disc is a conventional and widely-used method, it presented a methodological limitation when simulating the hot stamping process by forming a new blank each time, and hence, a drawing-based friction method has been proposed and developed. Each drawing method applies loads in a different way, resulting in a different wear behavior. Notably, the deep drawing process is most similar to the hot stamping process compared to other drawing methods. In this paper we present a review of the friction testing methods mimicking the hot stamping process and the associated wear behavior. This can be helpful in presenting a step-by-step approach and different perspectives on the wear behavior in the hot stamping process.

• 가정과삶의질연구
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• 제31권1호
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• pp.61-72
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• 2013

This study evaluated Kinetic Family Drawing according to preschoolers' external problem behavior. To achieve this, 120 preschoolers who were four or five years old were investigated and data were statistically analyzed using mean, and chi square analysis with the SPSS Win 13.0 program. The preschoolers' family drawings were analyzed by using the method in Kinetic Family Drawing(Burns & Kaufman, 1972). First, regarding characteristics, the preschoolers in the aggression group rotated certain person or drew the figure from behind, the preschoolers in the delinquency group drew long arms, the figure from behind, and angular forms. Second, regarding action depicted, the preschoolers in both aggression and delinquency groups perceived the lower activity level of their fathers, dangerous situations, and excluded family interaction. Third, regarding symbols, the preschoolers in the delinquency group drew objects such as balls. Finally, regarding drawing style, the preschoolers in the delinquency group drew edges and underline.

• 소성∙가공
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• 제19권4호
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• pp.236-241
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• 2010

The frictional behavior of bare steel sheet highly depends on surface roughness. It was investigated that the change of surface roughness of bare steel sheet due to deformation for each forming mode. The flat type friction test was done to check the effect of surface roughness change on frictional characteristics of bare steel sheet. As increasing the deformation, the Ra value was increased at stretching forming mode and drawing forming mode, however the change of Pc showed different trends. The Pc was decreased as increasing stretch deformation but increased at compression deformation. At drawing forming mode, the friction coefficient was increased as deformation was increased after initial big drop with drawing oil. As deformation was increased, the friction coefficient was decreased with drawing oil at stretching forming mode. The results show that the deformation changes the surface roughness and frictional characteristics of steel sheet but the effect depends on the forming mode.

• 한국염색가공학회지
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• 제11권5호
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• pp.44-54
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• 1999

Poly(ethylene 2,6-naphthalate), PEN, is a relatively well-known polymer used for engineering purposes. Naphthalene ring provides rigidity to the polymer backbone, thus, it elevated the glass transition temperature and enhanced mechanical properties. The structure and properties of PEN affect a processing conditions severely, and the high-thermal stability have been had a poor thermal processibility. Hence, the basic mechanism of solvent drawing, is very much the same as that of thermal drawing from glassy state since both involve the inducement of segmental mobility. The former achieves the goal by use of chemical energy, and the latter does so by use of thermal energy. Generally, the sorption of the solvent by the polymer has a plasticizing effect, and leads to a lowering of the glass transition temperature, $T_g$. In this paper, the dynamic viscoelasticity behavior in liquid-drawing process of an unoriented amorphous PEN films were investigated using Rheovibron. The results are as follows ： (1) For the drawing in silicone oil, the drawing below $T_g$. had $\alpha{2}$-dispersion due to an inhomogeneous taut structure. (2) For the drawing in water, the inhomogeneous taut structure reduced by the effect of plasticization even below $T_g$. (3) For the drawing in butanol, the only aliphatic segment in PEN have some molecular mobility but the mobility of the aromatic segment having naphthalene ring is nearly impossible. (4) For the drawing in dioxane/water mixing solvent, the solvent effect is complementary each other and accordingly the entire molecular conformation have stable state. (5) For the drawing in dioxane/butanol mixing solvent, the inhomogeneity of the taut structure and the aromatic segment increase with increasing the temperature and this tendencies correspond with that of the draw ratio.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.213-214
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• 2009

Recently the use of ferritic stainless steels for automotive exhaust system has been increased dramatically. A detailed knowledge of material behavior of ferritic stainless steel is important for successful manufacturing of exhaust systems. To achieve this goal, numerical study of square cup deep drawing for ferritic stainless steel sheet, type 409L was conducted with Yld2000-24. Uniaxial tensile test and hydraulic bulge test were performed to characterize plastic material behavior. Finite element simulation of square cup deep drawing was performed successfully.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.409-412
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• 2009

A study is made to put forward the new method of continuous-shear drawing (CSD), and investigate deformation behavior and microstructure evolution of aluminum alloy with a comparison of equal-channel angular (ECA) drawing. In contrast to ECA drawing, the die for CSD deformation can impart an additional strain to the workpiece since the diameter of the exit channel is narrower than that of its entrance channel. Although no significant crack occurs in all conditions during deformation, the sample deformed via CSD method showed better surface quality as compared to ECA drawing. This is mainly ascribed to the fact that the sample is significantly bent rather than sheared when deforming through ECA drawing.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 춘계학술발표대회 논문집
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• pp.91-94
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• 1999

• 소성∙가공
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• 제20권5호
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• pp.357-361
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• 2011

A beryllium copper alloy(C1720) sheet was stretch-drawn using different processes. A hemispherical punch was first used and the forming behavior was examined. Then, cylindrical cups with a hemispherical head were produced by either one-step drawing or two-step forming(sequential stretch forming-drawing). The one-step drawing showed the better formability than two-step forming. However, the two-step forming was the superior process in terms of attaining shape accuracy.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2006년도 추계학술발표논문집
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• pp.290-293
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• 2006

본 연구는 웹 기반 선례검색 시스템을 개발하였다. 기존의 연구들에 대한 사례 조사를 통해서 지금까지의 선례 검색 방법의 한계: 변환과정에서의 의미 손실과 자료 공유의 시공간제한성 밝혔다. 해결책으로 의미기반 공통표현모듈을 도입하고 웹 환경을 이용하여 효과적인 선례검색 해결방법을 찾아냄으로써 검색과 자료 공유가 용이한 선례검색 시스템을 개발했다.