• Title/Summary/Keyword: 소성변형영역

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Finite Element Analysis of Strain Localization in Concrete Considering Damage and Plasticity (손상과 소성을 고려한 콘크리트 변형률 국소화의 유한요소해석)

  • 송하원;나웅진
    • Computational Structural Engineering
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    • v.10 no.3
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    • pp.241-250
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    • 1997
  • The strain localization of concrete is a phenomenon such that the deformation of concrete is localized in finite region along with softening behavior. The objective of this paper is to develop a plasticity and damage algorithm for the finite element analysis of the strain-localization in concrete. In this paper, concrete member under strain localization is modeled with localized zone and non-localized zone. For modeling of the localized zone in concrete under strain localization, a general Drucker-Prager failure criterion by which the nonlinear strain softening behavior of concrete after peak-stress can be considered is introduced in a thermodynamic formulation of the classical plasticity model. The return-mapping algorithm is used for the integration of the elasto-plastic rate equation and the consistent tangent modulus is also derived. For the modeling of non-localized zone in concrete under strain localization, a consistent nonlinear elastic-damage algorithm is developed by modifying the free energy in thermodynamics. Using finite element program implemented with the developed algorithm, strain localization behaviors for concrete specimens under compression are simulated.

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Unified Constitutive Modeling for Low Temperature Austenitic Stainless Steel (저온용 스테인레스강의 통합 구성방정식)

  • Yoo, Seong-Won;Park, Woong-Sup;Lee, Jae-Myung
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2010.04a
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    • pp.504-507
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    • 2010
  • 본 논문에서는 저온용 오스테나이트계 스테인리스강(ASS)의 온도 및 변형률 속도의 영향을 고려한 통합 구성 방정식 및 손상 모델을 제안하였다. 저온 영역에서, 304L ASS의 온도 및 변형률 속도별 인장 실험을 시행하였다. 그 결과, 변형 유기 마르텐사이트 상변태에 의해 상변태 유기 소성(TRIP)이 저온에서 현저히 나타났으며 온도 및 변형률 속도의 영향이 지대하였다. 실험 결과를 바탕으로 ASS의 저온 거동 및 특성을 규명하여 수치 모델에 반영하였다. 저온에서 일어나는 2차 경화 현상을 표현하기 위해, Bodner/Partom 점소성 구성 방정식을 수정하고 Tomita/Iwamoto 변형 유기 상변태 모델을 구성 방정식에 적용시켰다. 저온 연성 파단 현상을 표현하기 위해, Bodner/Chan 손상모델을 수정하여 접목시켰다. 제안된 모델을 유한요소 프로그램에 탑재시키고, 온도 및 변형률 속도 의존 재료 정수를 결정하였다. 저온 영역에서, 온도 및 변형률 속도별 재료 거동을 시뮬레이션하고 이를 실험 결과와 비교 및 검증하였다.

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Liquefaction Analysis at Multi-Layered Ground Considering Viscoplastic Effect of Clay (점성토의 점소성 효과를 고려한 다층지반의 액상화 해석)

  • Yoon, Yong-Sun;Lee, Jae-Deuk;Kim, Yong-Seong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.55 no.5
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    • pp.59-69
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    • 2013
  • 본 연구에서는 동적 점탄-점소성 구성식에 기초한 다층지반의 1차원 액상화 해석을 수행하였다. 일본 고베 포트아일랜드에서 발생한 1995 Hyogoken Nanbu 지진에 대하여 지반 모델링을 하였으며, 사질토 지반에는 탄소성 모델을, 점성토 지반에는 점탄-점소성 모델 및 탄-점소성 모델을 각각 적용하였다. 본 연구 결과, 모델 지반의 경우 지표 10 m 아래를 전후하여 액상화가 발생하였으며 액상화가 발생한 지반을 통과하는 지진파는 감쇠특성을 나타내고 이 때 전단변형률을 크게 증가시켰다. 또한, 대변형률 영역에서의 점성토의 동적거동 해석에서는 점소성 거동특성이 지배적이므로 점소성 모델의 적용이 중요함을 알 수 있었다. 한편 동적 점탄-점소성 구성모델은 대변형률 영역에서 점성토의 소성변형을 유발하는 대형 지진 발생시 점성토의 증폭 및 감쇠특성 분석에 적용 가능한 모델임을 확인하였다.

p-Version Finite Element Analysis of Elasto-Plastic Cracked Plates Including Strain Hardening Effects (변형률 경화효과를 고려한 탄소성 균열판의 p-Version 유한요소해석)

  • 우광성;홍종현;윤영필
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.12 no.4
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    • pp.537-549
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    • 1999
  • 선형탄성 파괴해석은 균열을 갖는 변형률 경화재료의 파괴거동을 예측하는데 불충분하기 때문에 최근에는 균열 선단 부에서 대규모 소성 역을 갖는 균열 체에 적용할 수 있는 많은 파괴역학개념이 제안되고 있다. 따라서, 본 연구에서는 대규모항복 조건하의 연성파괴를 보이는 평판을 정확하게 해석할 수 있는 새로운 유한요소모델을 제시하고자 한다. 균열 선단 부의 응력 장을 정의하는데 가장 지배적인 파괴매개변수인 J-적분 값과 소성 역의 크기 및 형상을 J-적분법과 등가영역적분법을 통해 파괴거동을 설명할 수 있도록 증분소성이론에 기초를 둔 p-version 유한요소해석이 채택되었다. 제안된 유한요소모델에 의한 수치해석결과는 이론 해와 h-version 유한요소해석과 비교되었다.

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Evaluation of Plastic Rotational Capacity Based on Material Characteristics in Reinforced Concrete Flexural Members (재료 특성에 기반한 철근콘크리트 휨부재의 소성회전능력 산정)

  • Choi, Seung-Won;Kim, Woo
    • Journal of the Korea Concrete Institute
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    • v.22 no.6
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    • pp.825-832
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    • 2010
  • Although a critical section reaches its flexural strength in reinforced concrete structures, the structure does not always fail because moment redistribution occurs during the formation of plastic hinges. Inelastic deformation in a plastic hinge region results in plastic rotation. A plastic hinge mainly depends on material characteristics. In this study, a plastic hinge length and plastic rotation are evaluated using the flexural curvature distribution which is derived from the material models given in Eurocode 2. The influence on plastic capacity the limit values of the material model used, that is, ultimate strain of concrete and steel and hardening ratio of steel(k), are investigated. As results, it is appeared that a large ultimate strain of concrete and steel is resulting in large plastic capactiy and also as a hardening ratio of steel increases, the plastic rotation increases significantly. Therefore, a careful attention would be paid to determine the limit values of material characteristics in the RC structures.

AE Characteristic under Tensile of Carbon Steel for High-Pressure Pipe (고압배관용 탄소강의 인장시 음향방출 특성)

  • Nam Kiwoo;Lee Siyoon
    • Journal of the Korean Institute of Gas
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    • v.7 no.2 s.19
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    • pp.48-53
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    • 2003
  • This study is to look at the effect for deformation of carbon steel for high-presure pipe, on the AE signals produced by tensile test. Acoustic emission(AE) has been widely used in various fields because of its extreme sensitivity, dynamic detection ability and location of growing defects. We investigated a relationship failure mode and AE signals by tensile test, From the tensile test, we could divide into four ranges of the failure modes of elastic range, yield range, plastic range before $\sigma$u, plastic range after $\sigma$u. And failure behaviors of elastic range, yield range, plastic range before $\sigma$u, plastic range after $\sigma$u could be evaluated in tensile test by AE counts, accumulation counts and time frequency analysis. It is expected to be basic data that can protect a risk according to tensile test and bending of pipe material for pressure vessel, as a real time test of AE.

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Hydrostatic pressure in the center of wire drawing and extrusion of viscoplastic material (점소성 재료의 인발과 변형역 중심에서의 정수압에 관한 연구)

  • Oh, Hung Kuk
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.5 no.3
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    • pp.170-177
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    • 1981
  • 1,200.deg.C에서의 단조철은 점소성을 나타내며 인발과 압출시 변형영역이 구형수렴형태가 됨을 실험을 통하여 나타난다. 이 변형역 모델로부터 평형방정식을 사용하여 평균 압출 및 인발응력과 정수압을 계산해 낸다. 평균 압출 및 임발응력은 상계 해석 방법에 의한 결과와 비교하여 본 연구의 해석방법의 유효성을 타진하고 정수압은 다른 연구자들의 결과와 비교 검토되며 특히 냉간가공의 경우와 비교 검토 된다. 그 외에 마찰계수, 급형각도와 단면감소율의 영향에 대해서도 논의 된다.

Assessment of Ductility and Plastic Hinge Region of Reinforced Concrete Multi-Column Bent (2주형 다주교각의 연성도 및 소성힌지 영역에 관한 연구)

  • Byun, Soon-Joo;Im, Jung-Soon
    • Journal of the Korean Society of Hazard Mitigation
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    • v.6 no.3 s.22
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    • pp.37-45
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    • 2006
  • In this study, displacement ductility capacity and plastic hinge regions of reinforced concrete multi-column bent with different transverse reinforcement ratio are investigated. The ductility increases remarkably as transverse reinforcement ratio increase and the multi-column bent loaded along transverse direction is more ductile. The plastic hinge length for special detailing requirements of transverse reinforcement is estimated. For high target ductility, plastic hinge length for confinement should be extended with increased transverse reinforcement ratio. The plastic hinge length of multi-column bent loaded along transverse direction is shorter than that along longitudinal direction, because of the different moment distribution.

J2-bounding Surface Plasticity Model with Zero Elastic Region (탄성영역이 없는 J2-경계면 소성모델)

  • Shin, Hosung;Oh, Seboong;Kim, Jae-min
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.43 no.4
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    • pp.469-476
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    • 2023
  • Soil plasticity models for cyclic and dynamic loads are essential in non-linear numerical analysis of geotechnical structures. While a single yield surface model shows a linear behavior for cyclic loads, J2-bounding surface plasticity model with zero elastic region can effectively simulate a nonlinearity of the ground response with the same material properties. The radius of the yield surface inside the boundary surface converged to 0 to make the elastic region disappear, and plastic hardening modulus and dilatancy define plastic strain increment. This paper presents the stress-strain incremental equation of the developed model, and derives plastic hardening modulus for the hyperbolic model. The comparative analyses of the triaxial compression test and the shallow foundation under the cyclic load can show stable numerical convergence, consistency with the theoretical solution, and hysteresis behavior. In addition, plastic hardening modulus for the modified hyperbolic function is presented, and a methodology to estimate model variables conforming 1D equivalent linear model is proposed for numerical modeling of the multi-dimensional behavior of the ground.

Earth Pressure Analysis of Tunnel Ceiling according to Tunnel Plastic Zone (터널 소성영역에 따른 터널 천단토압 해석)

  • Park, Shin-Young;Han, Heui-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.11
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    • pp.753-764
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    • 2020
  • In this study, the plastic zone and internal earth pressure of the tunnel were calculated using the following three methods: metal plasticity to analyze the deformation of metal during plastic processing, Terzaghi's earth pressure theory from the geotechnical perspective and modified Terzaghi's earth pressure theory, and slip line theory using Mohr-Coulomb yield conditions. All three methods are two-dimensional mathematical analysis models for analyzing the plane strain conditions of isotropic materials. Using the theory of metallurgical plastics, the plastic zone and the internal earth pressure of the ground were obtained by assuming that the internal pressure acts on the tunnel, so different results were derived that did not match the actual tunnel site, where only gravity was applied. An analysis of the plasticity zone and earth pressure via the slip-line method showed that a failure line is formed in a log-spiral, which was found to be similar to the real failure line by comparing the results of previous studies. The earth pressure was calculated using a theoretical method. Terzaghi's earth pressure was calculated to be larger than the earth pressure considering the dilatancy effect.