• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
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• pp.83-90
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• 2004

The drawbead is one of the most important factors in sheet metal forming for automotive parts. So clarifying the friction characteristics between sheets and drawbead is essential to improve the formability of sheet metal. Therefore in this study, drawbead friction test was performed at various panels(cold rolled steel sheets, galvanized steel sheets, electrogalvanized coating steel sheets, electrogalvanized Zn-Fe alloy steel sheets and aluminum alloy steel sheets). Circular shape bead has been used for the test. The results show that friction and drawing characteristics were mainly influenced by the nature of zinc coating.

• Tribology and Lubricants
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• 제38권6호
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• pp.241-246
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• 2022

This paper presents the effects of cryogenic temperature on the wear behavior of 22MnB5 blank under cold stamping. After immersing the blank in liquid nitrogen (LN2) for 10 min, a strip drawing test was performed within 10 s. The hardness was measured using the Rockwell hardness test, which increased from 165 HV at 20℃ to 192 HV at cryogenic temperature. The strip drawing test with 22MnB5 blank and SKD61 tool steel shows that for the different wear mechanisms on the tool surface with respect to temperature; adhesive wear is dominant at 20℃, but abrasive wear is the main mechanism at cryogenic temperature. As the friction test is repeated, sticking gradually increases on the tool surface at 20℃, whereas the scratch increases at cryogenic temperature. For the friction behavior, the friction coefficient rapidly increases when adhesive wear occurs, and it occurs more frequently at 20℃. The results for nanoindentation near the worn blank surface indicate a difference of 1.3 GPa at 20℃ and 0.8 GPa at cryogenic temperature compared to the existing hardness, indicating increased deformation by friction at 20℃. This occurs because thermally activated energy available to move the dislocation decreases with decreasing temperature.

• 한국산학기술학회논문지
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• 제10권12호
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• pp.3963-3970
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• 2009

본 연구에서는 컴퓨터를 이용하여 미술치료에서 윤곽선의 예리성으로 형태를 평가하고 컬러이미지스케일을 통해 색채를 평가하여 '부드러운-딱딱한'의 정도를 정량적으로 평가하는 방법을 제안한다. 회귀모형을 사용하며 종속 변수는 색채 전문가가 그림을 '부드러운-딱딱한'으로 평가한 순위가 된다. 독립변수는 그림의 명도 및 채도의 평균과 표준편차, 그림의 색채 수, 픽셀의 양, 클러스터의 수, 윤곽선의 길이 및 예리성 등을 고려한다. 단계별 회귀분석에 의하여 종속변수를 설명하는 적절한 독립변수들을 선정한다. 평가자 간의 신뢰성을 살피고 평가자 순위와 시스템 순위 간의 순위상관계수를 통해 시스템의 타당성을 입증한다. 객관적이고 정량적 평가를 가능케 함으로써 색채심리 연구, 미술치료뿐만 아니라 패션, 섬유, 인테리어 산업 등에 유용한 정보를 제공한다.

• 전기의세계
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• 제30권7호
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• pp.441-447
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• 1981

As a preceeding work for the study on dielectric characterstics of a kind of low density polyethylene introduced morphological change by mechanical method, glass transition temperature which is regarded as a macroscopic aspect for relaxation of molecular chain segments has been observed by means of temperature dependent dilatometric measurement. The origina specimen clearly shows two knees which correspond to two peaks (.gamma. and .betha. peak) in the intenal friction measurement, suggesting the existence of separated glass transition temperatures at 150.deg.k and 260.deg.k respectively. On the specimen irradiated to 100 Mrad both glass transition temperatures tend to shift towards high temperature sides because of crosslinking by irradiation. furthemore an evidence can be seen that radiation effect, even in amorphous phase, is also slelctive depending on slight morphological differences. The specimen extended to four times in length shows a peculiar nature such as negative linear thermal expansion coefficient increasing with temperature between 220.deg.k and ambient temperature and that this fact is interpreted by considering that c axis of the lattice aligns along the extended direction by drawing, further c axis inherently possesses the characteristics of negative linear thermal expansion coefficient. For the observations that the relatively small positive linear expansion on the specimen extended to ca. two times as well as the part below 220.deg.k of the specimen extended to four times, it is considered for the reason of the facts that the incompletely oriented region indicated as the middle part of Peterlin's model tends to restore partially to orginal arrangement-a kind of phase transition-as increasing with temperature.

• 대한기계학회논문집
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• 제15권6호
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• pp.1807-1818
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• 1991

본 연구에서는 자동차용 Zn-Ni계 합금 전기도금 강판(electro Zn-Ni alloy coated steel sheet, EGN)에서 도금층 중의 Ni함량에 따른 금층의 표면특성이 마찰거 동에 미치는 영향과 윤활유 종류에 따른 Ni 함량별 마찰특성을 파악하여 최적 스탬핑 조건을 도출하는데 기여하고자 한다.

• 대한기계학회논문집
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• 제16권4호
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• pp.658-666
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• 1992

본 연구에서는 고속, 연속장업으로 이루어지고 있는 스템핑 공정에서 금형과 강판간의 접촉-슬립에 따른 마찰 및 윤활특성의 성능을 평가할 수 있도록 한 원형단면 형상의 드로오비드 마찰실험장치를 활용하여 가압력, 윤활유 특성, 드로잉 속도와 강 판의 표면특성 등에 따른 자동차용 냉연강판과 도금강판의 마찰계수와 드로오비드 저 항력에 대한 테이터 베이스를 구축하고자 한다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 자동차부품 제작기술의 진보
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• pp.75-86
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• 1996

Three-Dimensional finite element analysis is performed using PAM-STAMP for design evaluation of automotive back door inner panel die. Gravity process by blanks own weight, binder-wrap process, and drawing process in the forming operations are sequentially simulated with Virtual Manufacturing Method. The most valuable result in this research is that 3-D FEM analysis can be applied to the design evaluation of draw die in the die try-out, though effects of mesh size and drawbead resistance force on the numerical accuracy are much sensitive. For the intensive application to draw-die design and try-out, the experimental know-hows about the forming variables such as friction coefficient, punch velocity, drawbead force, etc are necessary.

• 소성∙가공
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• 제16권2호
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• pp.107-112
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• 2007

In this study, the mechanical joining process for double sheet metals was investigated by using physical modeling method. Process parameters of mechanical joining such as friction coefficient, drawing depth, pouch radius, die radius and material thickness are preliminarily analyzed by finite element method. Referring to the finite element analysis results mechanical joining system is designed on the basis of physical similarities. From the physical modeling test, the effect of process parameters on the deformation for the mechanical joining are experimentally investigated and optimized joining shape that can provide strong joining strength is obtained.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.546-551
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• 1997

In sheet metal forming, since the surface area of workpiece is apparently larger than the volume of it, the surface condition of the sheet metal is much varied. The formability of sheet metal is decided by the forming limit and the macroscopic suface defect as like fracture and wrinkle, and microscopic asponent, The factors affected in forming limit are stain herdening exponent, strain-rate scnsitivity exponent, anisotropic coefficient. The increasing of surface roughness is decresed the forming limit curve. It is known that the greater plastic deformation the more surface roughness by Kienzle, Osadaka. The purpose of this study is to investigate the influences of surface roughness in a uniaxial tension and the traperzoidal-shaped box drawing.

• 소성∙가공
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• 제9권1호
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• pp.17-26
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• 2000

A series of parametric study was performed for the investigation on the influence of analysis parameters to the solution behavior in the elastic-plastic-static analysis of several sheet metal forming processes, such as deflection by a point force under plane strain and axisymmetric conditions, plane strain bending by a punch, axisymmetric stretching by a punch, axisymmetric bulging by hydraulic pressure, and axisymmetric deep drawing by a punch. The parameters considered are kind of element, number of elements, integration scheme for elemental equation and friction coefficient. Results obtained for different selections of those parameters were compared with each other, experimental measurements and analytical solution.