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평면이방성을 고려한 차체 스템핑의 3차원 유한요소 시뮬레이션
금영탁(Y.T.Keum),이승열(S.Y.Lee),안덕찬(D.C.Ahn) 한국자동차공학회 1994 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The 3-dimensional FEM formulation for simulating stamping processes of autobody pannel. which considers the sheet as a planar anisotropic membrane, is applied to the formability analysis of front fender stampings, In the FEM formulation, an implicit, incremental, updated Lagrangian scheme is adopted. The linear triangular<br/> finite-elements with rigid-viscoplastic material behaviors are used, For considering directional in-plane properties of the stamping operation of the sheet, Barlat's strain-rate potential is employed.<br/> The numerical simulaion of a front fender panel verified the usefulness, accuracy and stability of the formulation, and the in-plane anisotropic effects on the stampings of mild steel and aluminum alloy sheets are examined.<br/>
홍성훈(S. H. Hong),안덕찬(D. C. Ahn),김광육(K. Y. Kim),김영석(Y. S. Kim) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
Tensile tests are used to clarify the basic mechanical properties of tested specimens and the obtained stress-strain relation gives important information for plastic flow under metal forming processes, i.e. formability and anisotropic properties. The specimen size, test procedure and data measurement method are specified under tensile test standards in order to assure reliability of the tested data. However, many various tests are performed in industrised, universities and research institutes for their convenience in reality. In this study we performed tensile tests according to the different test method and compared their results. These finding will contribute the understanding of each test method.
홍성훈(S. H. Hong),안덕찬(D. C. Ahn),김영석(Y. S. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.10
A fuel cell car has been noted next generation automobile. Recent research focused on fuel cell which is the main part of fuel cell cars. Use of thinner stainless steel sheets in bi-polar plate can reduce the weight and volume of the fuel cell. There are various standards to get into the basic mechanical properties of material, but not in the case of thin sheet metal is not clarified. To get an exact mechanical property is important to evaluated formability of thin stainless steel sheets. In this study, we performed tensile test, erichsen test to evaluate the formability of thin stainless steel sheets. It is difficult to mount a strain gauge on the thin sheet metal due to its weight. To improve the reliability of the tensile test, a CCD camera was used for calculation deformation. Erichsen test is a cupping test to measure the ductility of a sheet metal and to determine its suitability for deep drawing. However, more than 0.1mm thickness material is used as the test apparatus. Erichsen spherical punch diameter of 8.0mm~20.0mm, that is not good for the sheet metal as thin as 0.075 to 0.15mm thickness, In the case of thin sheet metal small punch diameter is needed for experiment.
성형해석을 이용한 테일러드 블랭크 사이드 아우터 패널의 블랭크 및 금형 설계
인정제(J.J.Yin),안덕찬(D.C.Ahn),최익현(I.H.Choi),이경돈(K.D.Lee),유순영(S.Y.You),이영국(Y.K.Lee) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_2
The successful forming of tailor welded side panel requires appropriate blank design, weld line position and draw die design, etc.. In this study, the blank design of tailor welded side panels with different thicknesses was suggested through forming simulation results on the stretch flange model. Then the full model simulation was performed with the proposed designs of tailor welded side outer blank. From the full model simulation results, failure, wrinkles, and weld line movements were checked. According to the moving pattern of weldlines, the proper step position in the draw die was determined. The suggested blank and draw die design were applied to the real panel forming.
3차원 집합조직을 이용한 페라이트계 스테인리스강의 리징 예측
정양진(Y. J. Chung),안덕찬(D. C. Ahn),이명규(M. G. Lee) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
Experimental and numerical investigations of the surface roughening (namely, ridging or roping) in ferritic stainless steels were presented in this paper. Stainless steels exhibiting distinct level of ridging were selected as samples; i. e., MatA: severe ridging, MatR: low ridging. The roughness of the uniaxially elongated specimens up to 15% in rolling direction was measured and predicted using rate-dependent crystal plasticity FEM. For the input of the material model, initial textures of the two materials on the 5 sequential RD planes which were obtained by mechanical polishing in identical abrasive depth were measured by EBSD (Electron back-scatter diffraction). Measured respective 2-D textures were collected and mapped onto the FE mesh in each material. Ridging profiles by CPFEM using both 1-layer and 5-layer texture were compared to the experimental results. Predicted ridging profile of MatR by 3-dimensional, i.e. using 5-layer EBSD, orientations was in good agreement with experiment. On the other hand, 2-dimensional approach was sufficient to estimate the ridging in MatA.
박진기(J. G. Park),안덕찬(D. C. Ahn),남재복(J. B. Nam),김영석(Y. S. Kim) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
This paper includes a review of biaxial tensile test equipment and specimen. Biaxial testing of metal is becoming prevalent in sheet metal industry to evaluate mechanical properties for tested materials. Because light and high strength materials as aluminum, magnesium, titanium, and ultra high strength steel are largely anisotropic, biaxial tensile test i: used as opposed to the common uniaxial test. Also, the stresses acting on a component in service are generally multi-axial in nature. Therefore, it is necessary to consider the mechanical properties not only under uniaxial stress states but also under these multi-axial states of stress. In this paper, the several kinds of biaxial tensile test were introduced and it: limitation and challenge were discussed.