• Title/Summary/Keyword: anisotropic material

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Formulation and Identification of an Anisotropic Constitutive Model for Describing the Sintering of Stainless Steel Powder Compacts

  • Vagnon, Alexandre;Bouvardb, Didier.;Kapelskic, Georges
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.64-65
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    • 2006
  • Anisotropic constitutive equations for sintering of metal powder compacts have been formulated from a linear viscous transversely-isotropic model in which an anisotropic sintering stress has been introduced to describe free sintering densification kinetics. The identification of material parameters defined in the model, has been achieved from thermomechanical experiments performed on 316L stainless steel warm-compacted powder in a dilatometer allowing controlled compressive loading.

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Experimental and Numerical Study on Anisotropic Phase Separation of Liquid Crystal and Polymer Composites Cell Gap Variation

  • Jin, Min-Young;Bae, Ji-Hong;Kim, Jae-Hoon
    • 한국정보디스플레이학회:학술대회논문집
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    • 2007.08a
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    • pp.567-570
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    • 2007
  • Cell gap dependence on anisotropic phase separation was studied. The results showed that the morphology of phase separation depended on cell gap and material parameters. With numerical simulation and experiments, the optimal range of cell gap in the formation of polymer layer and liquid crystal was suggested for given material parameters.

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Analysis of Deep Drawing of Planar Anisotropic Materials Using the Rigid- Plastic Finite Element Method (강소성 유한요소법을 이용한 평면 이방성 재료의 디프 드로잉 해석)

  • 김형종;김동원
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.2
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    • pp.248-258
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    • 1992
  • Three-dimensional rigid-plastic finite element formulation based on the membrane theory was described and a computer program for large deformation analysis was developed. In the formulation, normal and planar anisotropy of sheet material and rotation of the principal axes of anisotropy was taken into consideration. Sheet metal was assumed to be rigid-plastic material obeying Hill's quadratic yield criterion and its associated flow rule. Deep drawing process, as a preliminary test, for normal anisotropic material was analyzed in order to examine the validity of developed finite element program. The results were consistent with the existing finite element solutions or experimental data. The present study was mainly concerned with the influence of planar anisotropy on deformation behaviour. Finite element analysis and experiment were carried out for the whole process of deep drawing of planar anisotropic material. The computational and experimental results on the shape of ear, strain distribution and punch load were in good agreement.

TMAH/IPA Anisotropic Etching Characteristics with Addition of Pyrazine (Pyrazine이 첨가된 TMAH/IPA 이방성 식각특성)

  • 박진성;정귀상
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1997.04a
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    • pp.23-26
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    • 1997
  • This work presents the TMAH/IPA anisotropic etching characteristics with addition of Pyrazine. (100) Si etching rate of 0.747 ${\mu}{\textrm}{m}$/min at 8$0^{\circ}C$ was obtained using TMAH 25 wt.% / IPA 17 vol.% / pyrazine 0.1 g. The etching rate of (100) Si is increased about 52% compare to pure TMAH 25 wt.%. But etching rate of (100) Si is decreased with increasing Pyrazine additive. Activation energy of TMAH/IPA/pyrazine is much lower than TMAH and TMAH/IPA solutions. Addition of Pyrazine does not effect on surface flatness and decreases undercutting ratio about 20 %. Therefore, TMAH/IPA/pyrazine is an attractive anisotropic etchant because of alkaline-ion free.

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A Theoretical Investigation of Forming Limits of Voided Anisotropic Sheet Metals (기공을 포함한 이방성 판재의 성형한계 예측)

  • You Bongsun;Yim Changdong;Kim Youngsuk;Won Sungyeun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.8 s.239
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    • pp.1139-1145
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    • 2005
  • Most failures of ductile materials in metal forming processes occurred due to material damage evolution - void nucleation, growth and coalescence. In this paper, the modified yield function of Liao et al in conjunction with the Hosford's yield criterion is studied to clarify the plastic deformation characteristic of voided anisotropic sheet metals. The void growth of an anisotropic sheet under biaxial tensile loading and damage effect of void growth on forming limits of sheet metals are investigated. Also the characteristic length defining the neck geometry is introduced in M-K model to incorporate the effect of triaxial stress in necked region on forming limits. The forming limits theoretically predicted are compared with experimental data. Satisfactory agreement was obtained between the predictions and experimental data.

Mode III Dynamic Interfacial Crack in Bonded Anisotropic Strip Under Anti-Plane Deformation (이방성재료 접합 띠판에 대한 면외 동적계면균열)

  • Park, Jae-Wan;Choi, Sung-Ryul
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.111-116
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    • 2000
  • A semi-infinite interfacial crack propagated with constant velocity in two bonded anisotropic strip under out-of-plane clamped displacements is analyzed. The asymptotic stress and displacement fields near the crack tip are obtained, where the results get more general expressions applicable not only to isotropic/orthotropic materials but also to the extent of the anisotropic material having one plane of elastic symmetry for the interfacial crack. The dynamic stress intensity factor is obtained as a closed form, which is decreased as the velocity of crack propagation increases. The critical velocity where the stress intensity factor comes to zero is obtained, which agrees with the lower value between the critical values of parallel crack merged in the material 1 and 2 adjacent to the interface. The dynamic energy release rate is also obtained as a form related to the stress intensity factor.

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Anisotropic Dispersion Force Effects for Surface Liquid Crystal Alignment on Rubbed Polystyrene Surfaces (러빙처리된 폴리스타이렌막 표면에있어서의 표면 액정 배향에관한 이방성 분산력의 효과)

  • 서대식
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1996.05a
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    • pp.105-108
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    • 1996
  • We have studied the anisotropic dispersion force effects for surfaces alignment of liquid crystals (LCs) on rubbed polystyrene (PS) surfaces by unidirection. In microphotographs of the textures, we obtained the nematic (N) LCs are shown to align in both direction parallel and Perpendicular to the rubbing for region up to medium rubbing, however to align in the direction perpendicular to the rubbing for strong rubbing legion. We suggest that the anisotropic dispersion force is very important rather than macro-surface groove effect to uniform alignment of LCs. We also measured the temperature dependence of extrapolation length of 5CB on rubbed PS surfaces for strong rubbing. It is shown that the polar anchoring strength of 5CB is very weak on rubbed PS surface compared to the rubbed polyimide (Pl) surface.

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Formulation of forming limit diagram based on strain-rate potential (소성 변형률 포텐셜에 기초한 성형 한계도의 정식화)

  • Kim D.;Chung K.;Kim K. J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.10a
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    • pp.156-159
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    • 2004
  • Most formulations for a forming limit diagram (FLD) have been based on yield stress potentials defined in the stress field. Nevertheless, there are formulations where potentials defined in the stain-rate field are especially convenient to formulate the rigid plastic material. Based on a strain-rate potential proposed for materials exhibiting planar anisotropic, the formulations for the forming limit diagram has been developed applying M-K theory. As verification example, the formulation is applied for anisotropic AA5182-O sheet. The good verification results show that the formulation for the forming limit diagram has been successfully developed.

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Numerical Simulation of the Electro-discharge Machining Process of a Conductive Anisotropic Composite (전기전도성 이방성 복합재료 방전가공의 수치모사)

  • 안영철;천갑재
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.709-712
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    • 2002
  • For the electro-discharge machining of an electro-conductive anisotropic composite, an unsteady state formulation was established and solved by Galerkin's finite element method. The distribution of temperature on work piece, the shape of the crater and the material removal rate were obtained in terms of the process parameters. As the spark was initiated the workpiece immediately started to melt and the heat affected zone was formed. The moving boundary of the crater was also identified with time. When the radial and axial conductivities were increased separately the temperature distribution and the shape of the crater were shifted in the same direction respectively and the material removal rate was found to be higher in the case of increasing radial conductivity rather than the axial conductivity.

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Elastic-Plastic Implicit Finite Element Method Considering Planar Anisotropy for Complicated Sheet Metal Forming Processes (탄소성 내연적 유한요소법을 이용한 평면 이방성 박판의 성형공정해석)

  • Yun, Jeong-Hwan;Kim, Jong-Bong;Yang, Dong-Yeol;Jeong, Gwan-Su
    • Transactions of Materials Processing
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    • v.7 no.3
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    • pp.233-245
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    • 1998
  • A new approach has been proposed for the incremental analysis of the nonsteady state large deformation of planar anisotropic elastic-plastic sheet forming. A mathematical brief review of a constitutive law for the incremental deformation theory has been presented from flow theory using the minimum plastic work path for elastic-plastic material. Since the material embedded coordinate system(Lagrangian quantity) is used in the proposed theory the stress integration procedure is completely objective. A new return mapping algorithm has been also developed from the general midpoint rule so as to achieve numerically large strain increment by successive control of yield function residuals. Some numerical tests for the return mapping algorithm were performed using Barlat's six component anisotropic stress potential. Performance of the proposed algorithm was shown to be good and stable for a large strain increment, For planar anisotropic sheet forming updating algorithm of planar anisotropic axes has been newly proposed. In order to show the effectiveness and validity of the present formulation earing simulation for a cylindrical cup drawing and front fender stamping analysis are performed. From the results it has been shown that the present formulation can provide a good basis for analysis for analysis of elastic-plastic sheet metal forming processes.

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