• 제목/요약/키워드: Normal Anisotropy

검색결과 107건 처리시간 0.022초

초기 이방성 SUS409L 박판재의 직사각 컵 성형을 위한 다단 디프드로잉 공정 적용에 관한 수치적 연구 (Numerical Simulation for a Multi-Stage Deep Drawing of Anisotropic SUS409L Sheet into a Rectangular Cup)

  • 박지우;구태완;강범수
    • 소성∙가공
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    • 제22권3호
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    • pp.133-142
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    • 2013
  • Recently, electric vehicles and hybrid cars are being promoted as alternatives to reduce automobile emissions. Generally, thin sheet materials such as aluminum alloy AA300X and cold-rolled steel sheet such as JIS-G-3141 are used for the container for the lithium-ion secondary batteries. In this study, a multi-stage deep drawing process is used to produce a rectangular cup from thin stainless steel sheet material, SUS409L, with an initial blank thickness of 0.4mm for the battery container application. Numerical simulations of the first through the fifth stages for the multi-stage deep drawing with thin SUS409L sheet were conducted using LS-Dyna3D Implicit/Explicit. Special consideration was given to the deformation characteristics due to the normal anisotropy of the sheet material. The numerical simulations were conducted with both isotropic properties and the anisotropic properties of the initial blank material. An unexpected forming failure, barreling in the bottom region of the deep drawn rectangular cup, was observed. This failure mode can be avoided by additional ironing thickness control during the process.

부분용적효과를 고려한 확산텐서영상에 대한 관심영역 분석 연구 (ROI Study for Diffusion Tensor Image with Partial Volume Effect)

  • 최우혁;윤의철
    • 대한의용생체공학회:의공학회지
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    • 제37권2호
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    • pp.84-89
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    • 2016
  • In this study, we proposed ameliorated method for region of interest (ROI) study to improve its accuracy using partial volume effect (PVE). PVE which arose in volumetric images when more than one tissue type occur in a voxel, could be used to reduce an amount of gray matter and cerebrospinal fluid within ROI of diffusion tensor image (DTI). In order to define ROIs, individual b0 image was spatially aligned to the JHU DTI-based atlas using linear and non-linear registration (http://cmrm.med.jhmi.edu/). Fractional anisotropy (FA) and mean diffusivity (MD) maps were estimated by fitting diffusion tensor model to each image voxel, and their mean values were computed within each ROI with PVE threshold. Participants of this study consisted of 20 healthy controls, 27 Alzheimer's disease and 27 normal-pressure hydrocephalus patients. The result showed that the mean FA and MD of each ROI were increased and decreased respectively, but standard deviation was significantly decreased when PVE was applied. In conclusion, the proposed method suggested that PVE was indispensable to improve an accuracy of DTI ROI study.

Abnormal Behavior in Color Tracking in the Fringe-Field Switching (FFS) Liquid Crystal Display

  • Jung, Jun-Ho;Ha, Kyung-Su;Chae, Mi-Na;Cho, In-Young;Kim, Woo-Il;Kim, Dae-Hyun;Kim, Sung-Min;Lee, Seung-Hee
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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    • pp.616-619
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    • 2009
  • Color tracking behavior of in the fringe-field switching (FFS) mode using a liquid crystal with positive dielectric anisotropy has been studied. In the in-plane switching and vertical alignment devices, color chromaticity at normal direction changes from bluish to yellowish white linearly with increasing grey levels from dark to white state. Interestingly, abnormal behavior in color tracking is observed in FFS devices using a liquid crystal with positive dielectric anisotropy, that is, it changes from bluish to yellowish up to a certain middle grey level but turns over to bluish white with further increasing from a grey level to a fully white state. In this paper, we analyze this abnormal effect from the calculated and experimental results.

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액상소결한 탄화규소의 집합조직 발달에 관한 연구 (A Study on Texture Development in Liquid-Phase Sintered Silicon Carbide)

  • 성한규;조경식;박노진;최헌진;이준근
    • 한국세라믹학회지
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    • 제37권4호
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    • pp.320-326
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    • 2000
  • Development of texture in SiC materials by hot-pressing and subsequent annealing was studied. Crystallographic texture type was characterized by measuring X-ray pole figures on the perpendicular plane to the hot-pressing direction. Observed all pole figures were nearly axially symmetric (fiber texture). In case of ${\beta}$-SiC materials, the pole density of basal plane (0004) increased as annealing time increased, in contrast, other planes (hkil) of ${\beta}$-SiC materials and all planes of ${\alpha}$-SiC materials nearly remained unchanged. In the case of ${\beta}$-SiC materials, therefore, a weak texture of (0001) plane at the normal direction took place in the 8h annealed samples, resulting from grian growth. The fracture toughness values of ${\alpha}$-SiC materials measured in both planes parallel and perpendicular to the hot-pressing direction were very similar. However, the fracture toughness of ${\beta}$-SiC materials measured parallel to the hot-pressing direction were higher than that measured perpendicular to the hot-pressing derection, relatively, because of the texture and the microstructure anisotropy.

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직교 이방적 사질토의 미시역학적 탄소성 모델링: I. 정식화 (Elastic-plastic Micromechanics Modeling of Cross-anisotropic Granular Soils: I. Formulation)

  • 정영훈;정충기
    • 한국지반공학회논문집
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    • 제23권3호
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    • pp.77-88
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    • 2007
  • 본 연구에서는 사질토의 탄성 및 탄소성 거동을 모사하기 위한 미시역학 기반의 구성 모델을 개발하였다. 개발 모델은 접촉 방향의 공간 분포를 통계적으로 처리한 조직 이방성, 응력비에 따른 조직 이방성의 변화, 간극비 변화에 따른 접촉점 수의 변화, 그리고 미시적 탄성-탄소성 접촉 강성을 고려하였다. 금속 재료에 대한 시험결과를 이용하여 미시적 탄소성 접촉 강성 모델을 수직 접촉력과 입자의 항복 접촉력에 대한 거듭제곱 함수의 형태로 유도하였다. 모델 변수를 정량적으로 평가하기 위해 직교 이방 탄성 계수의 근사식을 유도하였다.

축대칭 튜브 하이드로포밍 공정의 유한요소 시뮬레이션 (Finite Element Simulation of Axisymmetric Tube Hydroforming Processes)

  • 김용석;금영탁
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2001년도 추계학술대회 논문집
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    • pp.58-61
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    • 2001
  • An implicit finite element formulation for axisymmetric tube hydroforming is investigated. In order to describe normal anisotropy of the tube, Hill's non-quadratic yield function is employed. The frictional contact between die and tube and frictionless contact between tube and fluid are considered using the mesh-normal vector computed from finite element mesh of the tube. In order to verify the validity of the developed finite element formulation, the axisymmetric tube bulge test is simulated and simulation results are compared with experimental measurements. In the axisymmetric tube hydroforming process, an optimal hydraulic curve is pursued by performing the simulation with various internal pressures and axial forces.

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축대칭 튜브 하이드로포밍 공정의 유한요소 시뮬레이션 (Finite Element Simulation of Axisymmeric Tube Hydroforming Processes)

  • 김용석;금영탁
    • 소성∙가공
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    • 제11권1호
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    • pp.75-83
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    • 2002
  • Recently, the hydroforming process is widely applied to the automotive industry and rapidly spreaded to other industries. In this paper, An implicit finite element formulation for simulating axisymmetric tube hydroforming processes is performed. In order to describe normal anisotropy of the tube, Hill's non-quadratic yield function is employed. The frictional contact between die and tube and the frictionless contact between tube and fluid are considered using the mesh-normal vectors computed from the finite element mesh of the tube. The complete set of the governing relations comprising equilibrium and interfacial equations is linearized for Newton-Raphson procedure. In order to verify the validity of the developed finite element formulation, the axisymmetric tube bulge test is simulated and the simulation results are compared with experimental measurements. In a simulation of stepped circular tube hydroforming processes, an optimal hydraulic pressure curve is pursued by considering simultaneously internal pressures and axial forces.

랜덤하중이 가해진 복합재료 H-형 보의 동적 응답 해석 (Dynamic Response Analysis of Composite H-Type Cross-Section Beams to Random Loads)

  • 김성균;송봉건;송오섭
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2011년도 추계학술대회 논문집
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    • pp.130-135
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    • 2011
  • A study of the bending-extension-transverse shear coupled random response of the composite beams with thin-walled open sections subjected to various types of concentrated and distributed random excitations is dealt with in this paper. First of all, equations of motion of thin-walled composite H-type cross-section beams incorporating a number of nonclassical effects of transverse shear and primary and secondary warping, and anisotropy of constituent materials are derived. On the basis of derived equations of motion, analytical expressions for the displacement response of the composite beams are derived by using normal mode method combined with frequency response function method.

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연속체요소를 이용한 이방성 박판재료 성형공정의 강소성 유한요소해석 (Rigid-Plastic Finite Element Analysis of Anisotropic Sheet Metal Forming Processes by using Continuum Elements)

  • 이동우;양동열
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1997년도 추계학술대회논문집
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    • pp.24-27
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    • 1997
  • In the present work, rigid-plastic continuum elements employing the shape change and anisotropic effects are derived for the purpose of applying more realistic blankholding force condition in three-dimensional finite element analysis of sheet metal forming process. In order to incorporate the effect of shape change effectively in the derivation of finite element equation using continuum element for sheet metal forming, the convected coordinate system is introduced, rendering the analysis more rigorous and accurate. The formulation is extended to cover the orthotropic material using Hill's quadratic yield function. For the purpose of applying more realistic blankholding force condition, distributed normal and associated frictional tangent forces are employed in the blankholder, which is pressed normal and associated frictional tangent forces are employed in the blankholder, which is pressed against the flange until the resultant contact force with the blank reaches the prescribed value. As an example of sheet metal forming process coupling the effect of planar anisotropy and that of blankholding boundary condition, circular cup deep drawing has been analyzed considering both effects together.

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DEPENDENCE OF STRUCTURAL AND MAGNETIC PROPERTIES ON DEPOSITTION ANGLE IN EVAPORATED Co/Pt MULTILAYER THIN FILMS

  • Moon, Ki-Seok;Shin, Sung-Chul
    • 한국자기학회지
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    • 제5권5호
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    • pp.465-469
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    • 1995
  • We have investigated the effects of deposition angle on structural and magnetic properties of e-beam evaporated ${(4-{\AA}\;Co/9.2-{\AA}\;Pt)}_{23}$ multilayer thin films prepared on tilted substrates. It was found that the [111] crystallographic orientations of the multilayer thin films were not aligned with colummar growth orientations and they were remained to be normal to the substrate planes even though the deposition angle was severely oblique up to $60^{\circ}$. The analysis of the torque curve reveal that the intrinsic anisotropy energy was monotonically decreased with the deposition angle but the easy axis orientation parallel to the substrate normal was not much influenced by deposition angle.

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