• 제목/요약/키워드: Constitutive models

검색결과 391건 처리시간 0.021초

포화 다공질 매체의 Arbitrary Lagrangian Eulerian (ALE) 정식화 (Arbitrary Lagrangian Eulerian (ALE) Formulations of Saturated Porous Media)

  • 박대효;정소찬
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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    • pp.235-242
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    • 2003
  • The solids and the fluids in porous media have a relative velocity to each other. Due to physically and chemically different material properties and their relative velocity, the behavior of saturated porous media is extremely complicated. Thus, in order to describe and clarify the deformation behavior of saturated porous media, constitutive models for deformation of porous media coupling several effects such as flow of the fluids or thermodynanical change need to be developed in frame of Arbitrary Lagrangian Eulerian (ALE) description. The aim of ALE formulations is to maximize the advantages of Lagrangian and Eulerian elements, and to minimize the disadvantages. Therefore, this method is appropriate for the analysis of porous media that are considered for the behavior of the solids and the fluids. In this work, governing equations of porous media based on ALE description are obtained from governing equations in frame of updated Lagrangian description. Then, weak forms of these equations are derived using arbitrary weighting functions.

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재료비선형을 고려한 콘크리트 보의 실용적인 유한요소해석 (Practical Nonlinear FE Analysis of Concrete Beam Considering Material Nonlinearity)

  • 정원석
    • 한국철도학회논문집
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    • 제9권6호
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    • pp.778-783
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    • 2006
  • This study investigates the ultimate behavior of reinforced concrete beams by means of practical nonlinear finite element (FE) analyses. Uniaxial constitutive models for the concrete and steel material are selected in this study. The adopted material model is integrated into the ABAQUS fiber beam elements through a user-defined material subroutine (UMAT). Within a developed nonlinear finite element framework, the FE results have been compared to experimental results reported by other researchers. It has been found that the proposed finite element model is capable of predicting the initial cracking load level, the yield load, the ultimate load, and the crack distribution with acceptable accuracy.

2단 인장 실험을 통한 이방성 경화 모델의 평가 (Evaluation of Anisotropic Hardening Models using Two-Step Tension Tests)

  • 하진진;이명규
    • 소성∙가공
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    • 제21권6호
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    • pp.372-377
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    • 2012
  • In this study, the plastic flow behaviors of extra deep drawing quality (EDDQ) steel subjected to non-proportional strain paths were investigated. Two-step uniaxial tension tests, in which the first step was performed in the rolling direction (RD) and the subsequent test in different directions in $15^{\circ}$ increments from the RD, were conducted. The experiments clearly showed that stress overshooting and strain hardening stagnation were the dominant features, which were captured reasonably well using a recently proposed distortional hardening model.

Numerical modeling for cyclic crack bridging behavior of fiber reinforced cementitious composites

  • Shin, Kyung-Joon;Lee, Kwang-Myong;Chang, Sung-Pil
    • Structural Engineering and Mechanics
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    • 제30권2호
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    • pp.147-164
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    • 2008
  • Recently, many researches have been done to examine the behavior of fiber reinforced concrete (FRC) subjected to the static loading. However, a few studies have been devoted to cyclic behaviors of FRC. A main objective of this paper is to investigate the cyclic behavior of FRC through theoretical method. A new cyclic bridging model was proposed for the analysis of fiber reinforced cementitious composites under cyclic loading. In the model, non-uniform degradation of interfacial bonding under cyclic tension was considered. Fatigue test results for FRC were numerically simulated using proposed models and the proposed model is achieving better agreement than the previous model. Consequently, the model can establish a basis for analyzing cyclic behavior of fiber reinforced composites.

Characteristic features of concrete behaviour: Implications for the development of an engineering finite-element tool

  • Kotsovos, Michael D.;Pavlovic, Milija N.;Cotsovos, Demetrios M.
    • Computers and Concrete
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    • 제5권3호
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    • pp.243-260
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    • 2008
  • The present article summarises the fundamental characteristics of concrete behaviour which underlie the formulation of an engineering finite element model capable of realistically predicting the behaviour of (plain or reinforced) concrete structural forms in a wide range of problems ranging from static to impact loading without the need of any kind of re-calibration. The already published evidence supporting the proposed formulation is complemented by four additional typical case studies presented herein; for each case, a comparative study is carried out between numerical predictions and the experimental data which reveals good agreement. Such evidence validates the material characteristics upon which the FE model's formulation is based and provides an alternative explanation regarding the behaviour of structural concrete and how it should be modelled which contradicts the presently (widely) accepted assumptions adopted in the majority of FE models used to predict the behaviour of concrete.

형상기억합금 트러스 구조물을 이용한 스텐트의 설계 및 해석 (Stent modeling and simulation of truss structure using SMA)

  • 양성필;김상헌;조맹효
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2008년도 추계학술대회A
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    • pp.518-522
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    • 2008
  • Recently, many patients related to heart disease have surgical operation by expanding a blood vessel to treat the angiostenosis. So far most angioplasties have been performed using balloon-dilative stent made of stainless steel. Some researchers are studying the stent made of shape memory alloy (SMA) to operate the angioplasty more easily. and there are several papers which introduce the angioplasty using SMA. However, most of the analysis models for stents are constructed using solid elements. So much computing time is required to solve the analysis model. In this study, we suggest the SMA stent model using 1D truss element which is much faster than stent model using 3D solid element. To represent non-linear behavior of SMA, we apply 1D SMA constitutive equation of Lagoudas'. Pseudo-elastic behavior of stent structures is presented as a numerical example.

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이중 후방 응력 경화 모델을 이용한 주기 하중에서의 래쳐팅 거동 현상 연구 (Simulation of Ratcheting Behavior under Stress Controlled Cyclic Loading using Two-Back Stress Hardening Constitutive Relation)

  • 홍성인;황두순;윤수진
    • 소성∙가공
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    • 제17권1호
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    • pp.19-26
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    • 2008
  • In the present work, the ratcheting behavior under uniaxial cyclic loading is analyzed. A comparison between the published and the results from the present model is also included. In order to simulate the ratcheting behavior, Two-Back Stress model is proposed by combining the non-linear Armstrong-Frederick rule and the non-linear Phillips hardening rule based on kinematic hardening equation. It is shown that some ratcheting behaviors can be obtained by adjusting the control material parameters and various evolutions of the kinematic hardening parameter can be obtained by means of simple combination of hardening rules using simple rule of mixtures. The ultimate back stress is also derived for the present combined kinematic hardening models.

AZ31B 마그네슘 합금 판재의 구성식 개발 (Constitutive Modeling of AZ31B Magnesium Alloys)

  • 이명규;정관수;김헌영
    • 소성∙가공
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    • 제16권4호
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    • pp.234-238
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    • 2007
  • Magnesium alloy sheets in room temperature have unusual mechanical properties such as high in-plane anisotropy/asymmetry of yield stress and hardening behavior. In this paper, the continuum plasticity models considering the plastic behavior of AZ31B Mg alloy sheet were derived. A new hardening law based on modified two-surface model was developed to consider the general stress-strain response of metals including Bauschinger effect, transient behavior and the unusual asymmetry. Three deformation modes observed during the continuous tension/compression tests were mathematically formulated with simplified relations between the state of deformation and their histories. To include the anisotropy and asymmetry of the initial yield stress, the Drucker-Prager's pressure dependent yield surface was modified by adding anisotropic constants.

효율적 수소 생산을 위한 메탄 수증기 개질 반응기에서의 불연속적 가스 유입의 영향 (Effect of discontinuous mixture gas feeding on effective hydrogen production in a steam reformer frommethane)

  • 이신구;박준근;임성광;배중면
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2008년도 추계학술대회 논문집
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    • pp.25-28
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    • 2008
  • Steam reforming reaction is a matured technology to get hydrogen from hydrocarbon fuels compared with other reforming reactions such as partial oxidation(POX), autothermal reforming(ATR). It is so endothermic that it needs heat source to activate the reaction. Due to the reaction characteristics, heat transfer limitation phenomena generally occur in the steam reformer. As one of new ideas, the effect of discontinuous gas feeding is investigated based on heat transfer characteristics. The new operating method is usually favorable at high GHSV region(i.e. over $10,000h^{-1}$). In order to numerically simulate the physical issues, numerical approach is adopted based on heterogeneous reaction model, two-equation model in energy equation, and other constitutive models in porous media.

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모래에 대한 단일항복면 구성모델의 평가 (Evaluation of Single Hardening Constitutive Model for Sand)

  • 정진섭;박명배
    • 한국농공학회지
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    • 제40권6호
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    • pp.95-103
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    • 1998
  • Solutions of geotechnical engineering problems require calculation of deformation and stresses during various stages of loading. Powerful numerical methods are available to make such calculation even for complicated problems. To get accurate results, realistic stress-strain relationships of soil are dependent on a number of factors such as soil type, density, stress level and stress path. Attempts are continuously being made to develope analytical models for soils incorporating all such factors. The nature of stress-path dependency, the principle that governs deformations in sand, and the use of Lade's single work-hardening model for predicting sand response for a variety of stress-paths have been investigated and are examined. The test results and the analyses presented show that under some conditions sand exhibits stress-path dependent behavior. The strains calculated from Lade's single work-hardening model are in reasonable agreement with those measured, but some discrepancies occur. The largest difference between measured and calculated strains occurs for proportional loading with increasing stresses and for stress-path directions.

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