• 제목/요약/키워드: Homogenization Method

검색결과 257건 처리시간 0.03초

분자동역학을 이용한 다공성 물질 건조공정 멀티스케일 시뮬레이션(1부 : 균질화법 해석) (Multi-scale simulation of drying process for porous materials using molecular dynamics (part 1 : homogenization method))

  • 오진원;백성민;금영탁
    • 한국결정성장학회지
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    • 제14권3호
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    • pp.115-122
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    • 2004
  • 다공성 물질이 건조될 때 입자는 겔 상태의 그물망 구조를 갖는다. 따라서 건조공정 중 발생하는 잔류응력을 정확하게 해석하기 위해서는 공극률과 공극형상에 따른 물성을 알아야 한다. 본 연구에서는 균질화법으로 원형과 십자형의 공극을 갖는 미시적인 겔구조로부터 공극률에 따른 재료의 탄성특성을 예측하고. 다공성 세라믹 애자의 건조공정을 유한요소 해석하였다. 해석 결과, 변형 형상과 온도, 습도 분포는 공극을 고려하지 않은 해석과 유사하지만 잔류응력 값은 큰 차이가 있음을 알 수 있었다.

Design and homogenization of metal sandwich tubes with prismatic cores

  • Zhang, Kai;Deng, Zichen;Ouyang, Huajiang;Zhou, Jiaxi
    • Structural Engineering and Mechanics
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    • 제45권4호
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    • pp.439-454
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    • 2013
  • Hollow cylindrical tubes with a prismatic sandwich lining designed to replace the solid cross-sections are studied in this paper. The sections are divided by a number of revolving periodic unit cells and three topologies of unit cells (Square, Triangle and Kagome) are proposed. Some types of multiple-topology designed materials are also studied. The feasibility and accuracy of a homogenization method for obtaining the equivalent parameters are investigated. As the curved elements of a unit cell are represented by straight elements in the method and the ratios of the lengths of the curved elements to the lengths of the straight elements vary with the changing number of unit cells, some errors may be introduced. The frequencies of the first five modes and responses of the complete and equivalent models under an internal static pressure and an internal step pressure are compared for investigating the scope of applications of the method. The lower bounds and upper bounds of the number of Square, Triangular and Kagome cells in the sections are obtained. It is shown that treating the multiple-topology designed materials as a separate-layer structure is more accurate than treating the structure as a whole.

균질화기법과 유한요소법을 이용한 복합재료의 등가탄성계수 산정 (The Finite Element Analysis for Calculations of Equivalent Elastic Constants Using the Homogenization Method)

  • Yun, Seong-Ho
    • 한국전산구조공학회논문집
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    • 제13권1호
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    • pp.51-61
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    • 2000
  • 본 논문은 구조물의 미시적 측면에서 유효평균탄성계수를 결정하기 위한 균질화기법인 점근적 방법을 적용하였고, 탄성값을 조사하기 위하여 유한요소법으로 정식화하였다. 수치 예로서 물성치가 각기 다른 등방성 재료를 적층한 부재의 임의 단면에서 단위요소를 해석영역으로 설정하고 산출된 탄성계수를 기존의 해석방법으로부터 산출된 값과 비교하였다. 균질화기법으로 산출된 탄성계수는 과소평가되어 나타나며, 이는 해석영역을 유한요소 정식화하는 과정에서 수정항만큼 차이가 난다는 것을 증명하였다. 기존 해석방법으로는 복합재료의 탄성계수가 단순히 재료의 산술적 평균값으로 계산되는 것과는 달리, 미시적으로 복합재 단위요소의 반복성을 고려함으로써 제안된 해석방법이 보다 유용하다는 것을 보여 주었다.

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Multigroup cross-sections generated using Monte-Carlo method with flux-moment homogenization technique for fast reactor analysis

  • Yiwei Wu;Qufei Song;Kuaiyuan Feng;Jean-Francois Vidal;Hanyang Gu;Hui Guo
    • Nuclear Engineering and Technology
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    • 제55권7호
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    • pp.2474-2482
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    • 2023
  • The development of fast reactors with complex designs and operation status requires more accurate and effective simulation. The Monte-Carlo method can generate multi-group cross-sections in arbitrary geometry without approximation on resonances treatment and leads to good results in combination with diffusion codes. However, in previous studies, the coupling of Monte-Carlo generated multi-group cross-sections (MC-MGXS) and transport solvers has shown relatively large biases in fast reactor problems. In this paper, the main contribution to the biases is proved to be the neglect of the angle-dependence of the total cross-sections. The flux-moment homogenization technique (MHT) is proposed to take into account this dependence. In this method, the angular dependence is attributed to the transfer cross-sections, keeping an independent form for the total sections. For the MET-1000 benchmark, the multi-group transport simulation results with MC-MGXS generated with MHT are improved by 700 pcm and an additional 120 pcm with higher order scattering. The factors that cause the residual bias are discussed. The core power distribution bias is also significantly reduced when MHT is used. It proves that the MCMGXS with MHT can be applicable with transport solvers in fast reactor analysis.

최적조건법에 의한 위상 최적화 연구 (Topology Optimization using an Optimality Criteria Method)

  • 김병수;서명원
    • 한국자동차공학회논문집
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    • 제7권8호
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    • pp.224-232
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    • 1999
  • Topology optimization has evolved into a very efficient concept design tool and has been incorporated into design engineering processes in many industrial sectors. In recent years, topology optimization has become the focus of structural design community and has been researched and applied widely both in academia and industry. There are mainly tow approaches for topology optimization of continuum structures ; homogenization and density methods. The homogenization method is to compute is to compute an optimal distribution of microstructures in a given design domain. The sizes of the micro-calvities are treated as design variables for the topology optimization problem. the density method is to compute an optimal distribution of an isotropic material, where the material densities are treated as design variables. In this paper, the density method is used to formulate the topology optimization problem. This optimization problem is solved by using an optimality criteria method. Several example problems are solved to show the usefulness of the present approach.

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Analysis Method of Transmission Characterization for Multi-layered Composite Material Based on Homogenization Method

  • Hyun, Se-Young;Song, Yong-Ha;Jeoun, Young-Mi;Kim, Bong-Gyu
    • 항공우주시스템공학회지
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    • 제15권6호
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    • pp.59-65
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    • 2021
  • In this paper, the transmission characteristics of the multi-layered composite material with wire mesh and honeycomb core for aircraft applications have been analyzed with the proposed method. The proposed method converts the conductive wire mesh into effective layer, while for the dielectric honeycomb core, effective permittivity has been derived based on volume fraction with the proposed method. The proposed method has been verified through comparison with full-wave simulation and revealed excellent. In addition, the calculation time of the proposed method is a few order of magnitude faster in comparison with the full-wave simulation.

Estimation of In vitro Digestibility of Barley Straw by Using a Homogenized Rumen Fluid and Artificial Saliva Mixed with Nitrogen and Energy Sources

  • Chaudhry, Abdul S.
    • Asian-Australasian Journal of Animal Sciences
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    • 제11권1호
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    • pp.13-16
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    • 1998
  • A $2{\times}2{\times}4$ factorial study was conducted to examine the possibility of improving estimates of in vitro digestibility, using untreated (UBS) and ammonia-treated (ABS) barley straw, through homogenization of rumen fluid (RF) and by additions of urea (U) and casein (C) as N sources and Xylose + Glucose (XG) as energy sources into artificial saliva. Digestibiltiy of ABS was significantly greater than that of UBS (p < 0.001). There was a significant decrease in digestibility when additions (U, UC, UCXG) were compared with the control (p < 0.001). A 2-way interaction between RF and straw type was significant (p < 0.05) for dry matter digestibility (DMD). Homogenization of RF increased DMD of ABS (p < 0.05) whereas it decreased DMD of UBS (p > 0.05). The study showed that addition of N alone or in combination with energy sources was not better than control, rather the reverse, digestion was inhibited by a combination of U and casein (UC). It was concluded that sufficient N and branched chain fatty acids were supplied in the inoculum from sheep fed high protein grass cubes to support the growth of cellulolytic microbes during in vitro incubation. Further studies are, however, required to explore the potential of homogenization in improving the in vitro method to estimate digestibility of cereal straws.

원공배열 결정에 최적기준법에 의한 전동차 크로스 빔의 위상최적화에 관한 연구( I ) (A Study on the Topology Optimization of Electric Vehicle Cross beam using an Optimality Criteria Method in Determination of Arranging Hole( I ))

  • 전형용
    • 한국정밀공학회지
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    • 제19권11호
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    • pp.137-145
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    • 2002
  • Electric vehicle body has to be subjected to uniform load and requires auxiliary equipment such as air pipe and electric wire pipe. Especially, the cross beam supports the weight of passenger and electrical equipments. a lightweight vehicle body is salutary to save operating costs and fuel consumption. Therefore this study is to perform the size and the shape optimization of crossbeam for electric vehicle using the method of topology optimization to introduce the concept of homogenization based on optimality criteria method which is efficient for the problem having the number of design variables and a few boundary condition. this provides the method to determine the optimum position and shape of circular hole in the cross beam and then can achieve the optimal design to reduce weight.

요소제거법을 이용한 구조물 위상최적설계 (Structural Topology Optimization using Element Remove Method)

  • 임오강;이진식;김창식
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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    • pp.183-190
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    • 2001
  • Topology optimization. has been evolved into a very efficient conceptual design tool and has been utilized into design engineering processes in many industrial parts. In recent years, topology optimization has become the focus of structural optimization design and has been researched and widely applied both in academy and industry. Traditional topology optimization has been using homogenization method and optimality criteria method. Homogenization method provides relationship equation between structure which includes many holes and stiffness matrix in FEM. Optimality criteria method is used to update design variables while maintaining that volume fraction is uniform. Traditional topology optimization has advantage of good convergence but has disadvantage of too much convergency time and additive checkerboard prevention algorithm is needed. In one way to solve this problem, element remove method is presented. Then, it is applied to many examples. From the results, it is verified that the time of convergence is very improved and optimal designed results is obtained very similar to the results of traditional topology using 8 nodes per element.

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Analysis of propagation characteristics of elastic waves in heterogeneous nanobeams employing a new two-step porosity-dependent homogenization scheme

  • Ebrahimi, Farzad;Dabbagh, Ali;Rabczuk, Timon;Tornabene, Francesco
    • Advances in nano research
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    • 제7권2호
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    • pp.135-143
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    • 2019
  • The important effect of porosity on the mechanical behaviors of a continua makes it necessary to account for such an effect while analyzing a structure. motivated by this fact, a new two-step porosity dependent homogenization scheme is presented in this article to investigate the wave propagation responses of functionally graded (FG) porous nanobeams. In the introduced homogenization method, which is a modified form of the power-law model, the effects of porosity distributions are considered. Based on Hamilton's principle, the Navier equations are developed using the Euler-Bernoulli beam model. Thereafter, the constitutive equations are obtained employing the nonlocal elasticity theory of Eringen. Next, the governing equations are solved in order to reach the wave frequency. Once the validity of presented methodology is proved, a set of parametric studies are adapted to put emphasis on the role of each variant on the wave dispersion behaviors of porous FG nanobeams.