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등방성손상을 고려한 탄소성 대변형 문제의 유한요소해석(제1보)
노인식(IN SIK NHO) 한국해양공학회 2000 韓國海洋工學會誌 Vol.14 No.2
In this paper, a new constitutive model for ductile materials was proposed. This model can describe the material degradation due to the evolution of isotropic damage during elasto-platic deformation. The plastic flow rule was derived under the framework of thermodynamic approach of continuum damage mechanics (CDM) in which plastic strain, hardening parameters and isotropic damage were taken as thermodynamic state variables. And the process to determine material constants for constitutive model using an experimental data was presented.
멀티스케일 모델을 이용한 CFRP 복합재료 적층판의 연속체 손상역학 모델 개발
박국진,남경민,정찬훈,최익현,신상준,김승조 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4
이 논문에서는 복합재료 적층판의 강도예측을 위해 멀티스케일 모델이 적용된 연속체 손상역학 모델을 개발하였다. 미시역학적 모델을 확장하여 전진적 파손해석을 수행할 때 필요한 연속체 손상역학 모델을 사용할 수 있도록 구성하였다. 다중 셀에 기반한 RVE 모델을 이용하여 섬유 다발 모델에 대한 해석을 수행하였다. 이 때 결함이 있는 섬유의 난수 분포를 이용하여 다중 셀로 구성되어 있는 RVE모델을 사용하였다. 또한 RVE 모델에 대한 점진적 파손해석을 수행하여 섬유다발에 대한 유한요소모델의 국부하중공유 방법을 수치적으로 재현하였다. 이에 대한 하중 변위 그래프를 도출하여 개별 섬유 파손에 의한 일방향 복합재료 물성의 강성저하 모델을 얻어내었다. 이를 통해 복합적층판 해석을 위한 Weibull 분포 기반의 연속체 손상역학 모델의 계수를 최적화하여 확인하였다. In this paper, a continuum damage mechanics model is developed which considers multi-scale situation to predict failure strength of composite materials. Extended concept for dealing with micro-mechanics model is considered to set up continuum damage mechanics model of progressive failure analysis. Using multi-cell based representative volume element (RVE) model, finite element models of fiber bundle are generated. Fiber bundle models with local defects are generated by combining RVE model with random distribution of fiber strength. Because of existence of the defects, local load sharing (LLS) occurs, and then it causes degradation of RVE model when progressive failure analysis is performed. Load and displacement curves of RVE model can be treated in ply material property degradation. Finally, certain variable is selected regarding degradation factor for solving laminates problems.
탄성체의 소성변형을 위한 응력파 기반 손상위상장 접근법을 이용한 MPM 시뮬레이션
김재형,성수경,신병석 한국차세대컴퓨팅학회 2023 한국차세대컴퓨팅학회 논문지 Vol.19 No.5
We propose a new approach to combining the Damage Phase Field for Stress Wave velocity with MPM(Material Point Method) simulation to improve the accuracy of the elastic plastic deformation simulation based on the MPM. Existing MPM simulations have calculated the Cauchy stress of each particle for plastic deformation and expressed force transfer between particles using the APIC (Affine Particle in Cell) approach. However, there is a limit to expressing the continuous damage evolution of an object from various plastic deformations only by affine calculations on the vertical stress of each particle. To cope with this limitation, this study calculates the stress wave velocity through differential computation for stress to represent continuous damage evolution as a damage phase field and combines it with MPM. Comparative experiments of the proposed method with the existing MPM were conducted in the same environment, and it was confirmed that the visual accuracy of the simulating elastic object's plastic deformation and damage was improved.
재료 비선형과 연속체 손상역학을 고려한 복합 적층판의 강도 예측
박국진(Kook-jin Park),강희진(Hee-jin Kang),신상준(SangJoon Shin),최익현(Ik-hyun Choi),김민기(MinKi Kim),김승조(Seung-jo Kim) 한국항공우주학회 2014 韓國航空宇宙學會誌 Vol.42 No.11
이 논문에서는 복합 적층판의 점진적 파손해석 기법을 개발하고 검증하였다. 강도 및 강성 예측의 정확성을 높이기 위해 재료 비선형 효과와 연속체 손상역학을 동시에 고려하였다. 파손 시작점과 성장을 예측하기 위한 식으로 Hashin의 판별식이 사용되었으며, 파손 모드는 수지인장/전단, 섬유 인장의 2가지 파손모드를 고려하였다. 비선형 탄성 및 점탄성의 구성방정식을 고려한 평형을 계산하기 위해 Newton-Raphson 방법이 사용되었다. 실험을 통해 얻어진 복합재료 단층의 물성을 이용하여 노치가 없는 시편에 인장력을 가했을 때 예상되는 적층복합재의 강도 및 변형률을 예측하였다. 이 경우 선형 물성과 저하계수만을 고려하여 예측된 강성/강도보다 실험결과에 근사하게 나타남을 확인하였다. This paper presents development and verification of the progressive failure analysis upon the composite laminates. Strength and stiffness of the fiber-reinforced composite are analyzed by property degradation approach with emphasis on the material nonlinearity and continuum damage mechanics (CDM). Longitudinal and transverse tensile modes derived from Hashin’s failure criterion are used to predict the thresholds for damage initiation and growth. The modified Newton-Raphson iterative procedure is implemented for determining nonlinear elastic and viscoelastic constitutive relations. Laminar properties of the composite are obtained by experiments. Prediction on the un-notched tensile (UNT) specimen is performed under the laminate level. Stress-strain curves and strength results are compared with the experimental measurement. It is concluded that the present nonlinear CDM approach is capable of predicting the strength and stiffness more accurately than the corresponding linear CDM one does.
최경식(Kyung-Sik Choi) 한국해양공학회 1990 韓國海洋工學會誌 Vol.4 No.2
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.
유한요소해석 후처리 기법을 이용한 용접부의 건전성 평가
이제명(JAE-MYUNG LEE),백점기(JEOM-KEE PAIK),강성원(SUNG-WON KANG),김명현(MYUNG-HYUN KIM) 한국해양공학회 2002 韓國海洋工學會誌 Vol.16 No.4
In this paper, a numerical methodology for health monitoring of weldment was proposed using finite element method coupled with continuum damage mechanics. The welding-induced residual stress distribution of T-joint weldment was calculated using a commercial finite element package SYSWELD+. The distribution of latent damage was evaluated from the stress and strain components taken as the output of a finite element calculation. Numerical examples were given to demonstrate the usefulness of this so-called "post-processing approach" in the case of welding-induced damage assessment.
요소 절단법을 사용한 섬유강화 복합재료의 대규모 통계적 체적 요소 모델 개발
박국진 ( Kook Jin Park ),신상준 ( Sangjoon Shin ),윤군진 ( Gunjin Yun ) 한국복합재료학회 2018 Composites research Vol.31 No.5
본 논문에서는 섬유강화복합재의 멀티스케일 해석을 위해 필요한 대규모/소규모 통계적 체적요소 모델을 개발하였다. 미시영역모델의 크기효과를 최소화하기 위해서 섬유를 최대한 포함한 거대모델을 구성하였다. 이를 위해 국부 영역의 요소 절단법을 이용하여 전체 유한요소 크기에 상관없이 신속한 격자 섬유/기지의 모델링이 가능한 요소생성기를 구성하였다. 이를 통해 대규모 통계 체적 모델을 도출하여 체적모델의 크기에 따른 국부하중공유의 차이를 고찰하고, 섬유방향의 연속체손상역학모델을 BSVEs 모델 해석으로부터 도출 하였다. BSVEs 모델을 보편적인 RVE모델과 비교 검증하였다. 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.