• Title/Summary/Keyword: 연속체손상역학모델

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Constitutive Equation for Concrete using Anisotropic Continuum Damage Model (이방성 손상모델을 이용한 콘크리트 구성방정식의 도출)

  • Lee, Ki Seong;Byun, Keun Joo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.4
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    • pp.751-759
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    • 1994
  • Concrete contains numerous microcracks initially. The growth and propagation of microcracks cause failure of concrete. These processings are termed as "damage". The concepts of the continuum damage mechanics are presented and the damage evolution law and constitutive equation are derived by using the Helmholz free energy and the dissipation potential by means of the thermodynamic principles. The constitutive equation includes the effects of elasticity, damage and plasticity of concrete. The proposed model successfully predicts the nonlinear behavior of concrete subject to monotonic uniaxial and biaxial loadings.

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Parallel Computation of a Nonlinear Structural Problem using Parallel Multifrontal Solver (다중 프런트 해법을 이용한 비선형 구조문제의 병렬계산)

  • Jeong, Sun Wan;Kim, Seung Jo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.2
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    • pp.41-50
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    • 2003
  • In this paper, nonlinear parallel structural analyses are introduced by using the parallel multifrontal solver and damage localization for 2D and 3D crack models is presented as the application of nonlinear parallel computation. The parallel algorithms related with nonliear reduce the amount of memory used is carried out because many variables should be utilized for this highly nonlinear damage analysis. Also, Riks' continuation method is parallelized to search the solution when strain softening occurs due to damage evolution. For damage localization problem, several computational models having up to around 1-million degree of freedoms are used. The parallel performance in this nonlinear parallel algorithm is shown through these examples and the local variation of damage at crack tip is compared among the models with different degree of freedoms.

Elasto-Plastic Anisotropic-Damage Model for Concrete (콘크리트의 탄-소성 이방성-손상 모델)

  • 이기성;송하원
    • Computational Structural Engineering
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    • v.9 no.1
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    • pp.65-76
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    • 1996
  • The initiation and growth of microcracks or microvoids inside concrete results in the progressive degradation of concrete. This damage processing along processing along with plastic deformation is main cause of nonlinear behavior of concrete. In this study, a continuum damage model of concrete is developed for the analysis of the nonlinear behavior of concrete due to damage and elasto-plastic deformation. Anisotropic damage tensor is used to describe the anisotropy of concrete and hypothesis of equivalent elastic energy is used to define the effective elastic tensor. The damage model including the damage evolution law and constitutive equation is derived with damage variable and damage surface which is defined by damage energy release rate by using the Helmholtz free energy and dissipation potential based on the thermodynamic principles. By adopting a typical plasticity model of concrete, plasticity of concrete is included to this model. Afinite element analysis program implemented with this model was developed and finite element analysis was performed for the analyses of concrete subjected to uniaxial and biaxial loadings. Comparison of the results of analysis with those of experiments and other models shows that the model successfully predicts the nonlinear behavior of concrete.

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Development of the Big-size Statistical Volume Elements (BSVEs) Model for Fiber Reinforced Composite Based on the Mesh Cutting Technique (요소 절단법을 사용한 섬유강화 복합재료의 대규모 통계적 체적 요소 모델 개발)

  • Park, Kook Jin;Shin, SangJoon;Yun, Gunjin
    • Composites Research
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    • v.31 no.5
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    • pp.251-259
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    • 2018
  • In this paper, statistical volume element modeling method was developed for multi-scale progressive failure analysis of fiber reinforced composite materials. Big-size statistical volume elements (BSVEs) was considered to minimize the size effect in the micro-scale, by including as many fibers as possible. For that purpose, a mesh cutting method is suggested and adapted into the fiber model generator that creates finite element domain rapidly. The fiber defect model was also developed based on the experimental distribution of the fiber strength. The size effects from the local load sharing (LLS) are evaluated by increasing the fiber inclusion in the micro-scale model. Finally, continuum damage mechanics (CDM) model to the fiber direction was extracted from numerical analysis on BSVEs. And it was compared with strength prediction from typical representative volume element (RVE) model.

An Application of Plasticity Model for Ice Deformation Characteristics (수변형 특성에 있어서 소성 모델의 응용)

  • Choe, Gyeong-Sik
    • Journal of Ocean Engineering and Technology
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    • v.4 no.2
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    • pp.15-21
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    • 1990
  • This study focuses the mechanical deformation response predicted by the plasticity model for polycrystalline ice. To describe various deformation characteristics, ice is idealized as a perfectly plastic material using an asymptotic exponential failure criterion. This criterion is suite for describing materials which exhibit brittle deformation at low hydrostatic pressure and ductile deformation at high hydrostatic pressure. The results are compared to those of continuum damage mechanics model. Plasticity model shows good agreement with damage model and experimental results for high confining pressures even at high strain-rates which is usually considered as a brittle condition under uniaxial compression.

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An Application of Plasticity Model for Ice Deformation Characteristics (수변형 특성에 있어서 소성 모델의 응용)

  • Choe, Gyeong-Sik
    • Journal of Ocean Engineering and Technology
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    • v.4 no.2
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    • pp.165-165
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    • 1990
  • This study focuses the mechanical deformation response predicted by the plasticity model for polycrystalline ice. To describe various deformation characteristics, ice is idealized as a perfectly plastic material using an asymptotic exponential failure criterion. This criterion is suite for describing materials which exhibit brittle deformation at low hydrostatic pressure and ductile deformation at high hydrostatic pressure. The results are compared to those of continuum damage mechanics model. Plasticity model shows good agreement with damage model and experimental results for high confining pressures even at high strain-rates which is usually considered as a brittle condition under uniaxial compression.

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.

Tunnel Stability Assessment Considering Rock Damage from Blasting Near to Excavation Line (굴착선 주변공 발파의 암반손상을 고려한 터널 안정성 검토)

  • 이인모;윤현진;이형주;이상돈;박봉기
    • Journal of the Korean Geotechnical Society
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    • v.19 no.4
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    • pp.167-178
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    • 2003
  • Damage and overbreak of the remaining rock induced by blasting can not be avoided during tunnel construction which may result in either short-term or long-term tunnel instability. Therefore, in this paper, a methodology to take into account the effect of blast-induced damage in tunnel stability assessment is proposed. Dynamic numerical analysis was executed to evaluate damage and overbreak of the remaining rock for the most common blasting pattern in road tunnel. Rock damage was quantified by utilizing the damage variable factor which is adopted proposed in continuum damage mechanics. The damaged rock stiffness and the damaged failure criteria are used to consider the effect of rock damage in tunnel stability analysis. The damaged geological strength index of the damaged rock was newly proposed from the relationship between deformation modulus and geological strength index. Also the Hoek-Brown failure criteria of the damaged rock was obtained using the damaged geological strength index. Analysing the tunnel stability with the consideration of the blast-induced damage of remaining rock, it was found that the extend of plastic zone and deformation increased compared to the undamaged rock. Therefore the short-term or long-term tunnel stability will be threatened when the rock damage from blasting is ignored in the tunnel stability analysis.

Micromechanical Model for the Consolidation Behavior in SiC-Ti Metal Matrix Composites (SiC-Ti금속기 복합재료의 강화거동에 관한 미시역학적 모델)

  • 김준완;김태원
    • Composites Research
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    • v.16 no.3
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    • pp.1-8
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    • 2003
  • Densification occurs by the inelastic flow of the matrix materials during the consolidation processes at high temperature for MMCs, and the results depend on many process conditions such as applied pressure, temperature and volume fraction of fiber and matrix materials. This is particularly important in titanium matrix composites since material failure may occur by either the applied conditions or microstructural parameters through the processes, and thus a generic model based on micro-mechanical approaches enabling the evolution of density over time to be predicted has been developed. The mode developed is then implemented into FEM so that practical process simulation has been carried out. Further the experimental investigation of the consolidation behavior of SiC/Ti-6Al-4V composites using vacuum hot pressing has been performed, and the results obtained are compared with the model predictions.

Numerical analysis of blast-induced anisotropic rock damage (터발파압력에 기인한 이방성 암반손상의 수치해석적 분석)

  • Park, Bong-Ki;Cho, Kook-Hwan;Lee, In-Mo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.6 no.4
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    • pp.291-302
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    • 2004
  • Blast-induced anisotropic rock damage around a blast-hole was analyzed by a using numerical method with user-defined subroutine based on continuum damage mechanics. Anisotropic blasting pressure was evaluated by applying anisotropic ruck characteristics to analytical solution which is a function of explosive and rock properties. Anisotropic rock damage was evaluated by applying the proposed anisotropic blasting pressure. Blast-induced isotropic rock damage was also analyzed. User-defined subroutines to solve anisotropic and isotropic damage model were coded. Initial rock damages in natural ruck were considered in anisotropic and isotropic damage models. Blasting pressure and elastic modulus of rock were major influential parameters from parametric analysis results of isotropic rock damage. From the results of anisotropic rock damage analysis, blasting pressure was the most influential parameter. Anisotropic rock damage area in horizontal direction was approximately 34% larger and about 12% smaller in vertical direction comparing with isotropic rock damage area. Isotropic rock damage area under fully coupled charge condition was around 30 times larger than that under decoupled charge condition. Blasting pressure under fully coupled charge condition was estimated to be more than 10 times larger than that of decoupled charge condition.

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