• Title/Summary/Keyword: Constitutive equation analysis

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A Finite Element Analysis for Near-net-shape Forming of Al6061 Powder under Warm Pressing (온간 성형 하에서 Al 합금 분말의 정밀정형에 대한 유한요소해석)

  • Kim, Ki-Tae;Yang, Hoon-Chul;Kim, Jong-Kwang
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.507-512
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    • 2003
  • A finite element analysis for near-net-shape forming of Al6061 powder was performed under warm pressing. The advantages of warm compaction by rubber isostatic pressing were discussed to obtain parts with better density distributions. To simulate densification and deformed shape of a powder compact during warm pressing, the elastoplastic constitutive equation based on yield function of Shima-Oyane was implemented into a finite element program(ABAQUS). The hyperelastic constitutive equation based on the Ogden strain energy potential was employed to analyze nonlinear elastic response of rubber. Finite element results were compared with experimental data for Al6061 powder compacts under warm pressing.

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Deformation Analysis of Micro-Sized Material Using Strain Gradient Plasticity

  • Byon S.M.;Lee Young-Seog
    • Journal of Mechanical Science and Technology
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    • v.20 no.5
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    • pp.621-633
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    • 2006
  • To reflect the size effect of material $(1\sim15{\mu}m)$ during plastic deformation of polycrystalline copper, a constitutive equation which includes the strain gradient plasticity theory and intrinsic material length model is coupled with the finite element analysis and applied to plane strain deformation problem. The method of least square has been used to calculate the strain gradient at each element during deformation and the effect of distributed force on the strain gradient is investigated as well. It shows when material size is less than the intrinsic material length $(1.54{\mu}m)$, its deformation behavior is quite different compared with that computed from the conventional plasticity. The generation of strain gradient is greatly suppressed, but it appears again as the material size increases. Results also reveal that the strain gradient leads to deformation hardening. The distributed force plays a role to amplify the strain gradient distribution.

Plane Strain Analysis of Sheet Metal with Arbitrary Forming Conditions (임의의 성형조건을 갖는 박판의 평면변형율 해석)

  • Keum, Y.T.;Lee, S.Y.;Wagoner, R.H.
    • Transactions of Materials Processing
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    • v.1 no.1
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    • pp.95-103
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    • 1992
  • The plane strain analysis for simulating the stretch/draw forming operation with an arbitrarily-shaped tool profile is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshes without depending on the explicit spatial derivatives of tool surfaces. The linear line elements are used for depicting the formed sheet, based on membrane approximation. The FEM formulation is tested in the sections of automotive inner panel and two-side draw-in. Not only the excellent agreement between measured and computed strains is obtained in the stretched section, but also the numerical stability of formulation is verified in the draw-in section.

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Development of Temperature Dependent Damage Model for Evaluating Material Performance under Cryogenic Environment (극저온 재료 성능분석을 위한 온도의존 손상모델 개발)

  • Lee, Kyoung-Joon;Kim, Tae-Woo;Yoo, Jea-Sin;Yoo, Seong-Won;Chun, Min-Sung;Lee, Jae-Myung
    • Journal of the Society of Naval Architects of Korea
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    • v.45 no.5
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    • pp.538-546
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    • 2008
  • In this paper, the constitutive equation is developed to analyze the characteristics of strain-induced plasticity in the range of low temperature of 316 stainless steel. The practical usefulness of the developed equations is evaluated by the comparison between experimental and numerical results. For 316 stainless steel, constitutive equations, which represent the characteristics of nonlinear material behavior under the cryogenic temperature environment, are developed using the Bodner's plasticity model. In order to predict the material behaviour such as damage accumulation, Bodner-Chan's damage model is implemented to the developed constitutive equations. Based on the developed constitutive equations, 3-D finite element analysis program is developed, and verified using experimental results.

Effect of rubber mold on densification behavior of metal powder during cold isostatic pressing (냉간정수압 하에서 금속분말의 치밀화에 미치는 고무몰드의 영향)

  • Jeong, Jin-Won;Kim, Gi-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.2
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    • pp.330-342
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    • 1998
  • The effect of rubber mold on densification behavior of pure iron powder was investigated under cold isostatic pressing. The thickness effect of rubber mold was also studied. The elastoplastic constitutive equation based on the yield function of Shima and Oyane was implemented into the finite element program(ABAQUS) to predict compaction responses of metal powder under cold isostatic pressing. The hyperelastic constitutive equation based on Moony-Rivlin and Ogden strain energy potentials was also employed to analyze deformation of rubber mold. The coefficients of the strain energy potentials were obtained from tension and volumetric compression data of rubber. Finite element results were compared with experimental data for densification of pure iron powder under cold isostatic pressing.

An Analysis of Axial Crushing Behavior of Energy Absorbing Aluminum Honeycomb and Design of Cell Configuration (에너지 흡수용 알루미늄 허니컴 재료의 압축거동 분석 및 설계)

  • 김중재;김상범;김헌영
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.5
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    • pp.195-205
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    • 2001
  • The mechanical properties of aluminum honeycomb on the direction of axial crushing under quasistatic loading test was investigated. The crushing process was simulated numerically by full-scale finite element models. Simulations reproduce the experimental results both qualitatively as well as quantitatively. From the investigation, we suggested the constitutive model of energy absorbing honeycomb structure for large scale impact analysis. Real impact test of the WB(Moving Deformable Barrier) was carried and compared with finite element simulation. Constitutive model used in the numerical simulation had a good correlation with experiment. By suggesting the optimizing method fur honeycomb cell configuration design, relationship between cell configuration and crush strength is studied.

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A THERMO-ELASTO-VISCOPLASTIC MODEL FOR COMPOSITE MATERIALS AND ITS FINITE ELEMENT ANALYSIS

  • Shin, Eui-Sup
    • Journal of Theoretical and Applied Mechanics
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    • v.3 no.1
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    • pp.45-65
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    • 2002
  • A constitutive model on oorthotropic thermo-elasto-viscoplasticity for fiber-reinforced composite materials Is illustrated, and their thermomechanical responses are predicted with the fully-coupled finite element formulation. The unmixing-mixing scheme can be adopted with the multipartite matrix method as the constitutive model. Basic assumptions based upon the composite micromechanics are postulated, and the strain components of thermal expansion due to temperature change are included In the formulation. Also. more than two sets of mechanical variables, which represent the deformation states of multipartite matrix can be introduced arbitrarily. In particular, the unmixing-mixing scheme can be used with any well-known isotropic viscoplastic theory of the matrix material. The scheme unnecessitates the complex processes for developing an orthotropic viscoplastic theory. The governing equations based on fully-coupled thermomechanics are derived with constitutive arrangement by the unmixing-mixing concept. By considering some auxiliary conditions, the Initial-boundary value problem Is completely set up. As a tool of numerical analyses, the finite element method Is used with isoparametric Interpolation fer the displacement and the temperature fields. The equation of mutton and the energy conservation equation are spatially discretized, and then the time marching techniques such as the Newmark method and the Crank-Nicolson technique are applied. To solve the ultimate nonlinear simultaneous equations, a successive iteration algorithm is constructed with subincrementing technique. As a numerical study, a series of analyses are performed with the main focus on the thermomechanical coupling effect in composite materials. The progress of viscoplastic deformation, the stress-strain relation, and the temperature History are careful1y examined when composite laminates are subjected to repeated cyclic loading.

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A Study on the Analysis of Incompressible and Looped Flow Network Using Topological Constitutive Matrix Equation (위상구성행렬식을 이용한 비압축성 순환망 형태의 유로망 해석에 관한 연구)

  • Yoo, Seong-Yeon;Kim, Bum-Shin
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.22 no.8
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    • pp.573-578
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    • 2010
  • Topological matrix which reflects characteristics of network connectivity has been widely used in efficient solving for complicated flow network. Using topological matrix, one can easily define continuity at each node of flow network and make algorithm to automatically generate continuity equation of matrix form. In order to analyze flow network completely it is required to satisfy energy conservation in closed loops of flow network. Fundamental cycle retrieving algorithm based on graph theory automatically constructs energy conservation equation in closed loops. However, it is often accompanied by NP-complete problem. In addition, it always needs fundamental cycle retrieving procedure for every structural change of flow network. This paper proposes alternative mathematical method to analyze flow network without fundamental cycle retrieving algorithm. Consequently, the new mathematical method is expected to reduce solving time and prevent error occurrence by means of simplifying flow network analysis procedure.