• Interaction and multiscale mechanics
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• 제2권1호
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• pp.45-68
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• 2009

An aim of the study is to develop an efficient numerical simulation technique that can handle the two-scale analysis of fluid permeation filters fabricated by the partial sintering technique of small spherical ceramics. A solid-fluid mixture homogenization method is introduced to predict the mechanical characters such as rigidity and permeability of the porous ceramic filters from the micro-scale geometry and configuration of partially-sintered particles. An extended finite element (X-FE) discretization technique based on the enriched interpolations of respective characteristic functions at fluid-solid interfaces is proposed for the non-interface-fitted mesh solution of the micro-scale analysis that needs non-slip condition at the interface between solid and fluid phases of the unit cell. The homogenization and localization performances of the proposed method are shown in a typical two-dimensional benchmark problem whose model has a hole in center. Three-dimensional applications to the body-centered cubic (BCC) and face-centered cubic (FCC) unit cell models are also shown in the paper. The 3D application is prepared toward the computer-aided optimal design of ceramic filters. The accuracy and stability of the X-FEM based method are comparable to those of the standard interface-fitted FEM, and are superior to those of the voxel type FEM that is often used in such complex micro geometry cases.

• 항공우주기술
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• 제12권2호
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• pp.48-56
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• 2013

본 연구에서는 다양한 균질화 기법을 통해 섬유강화 복합재료 단일 적층판의 등가탄성계수를 예측을 수행하였다. 섬유강화 복합재료의 등가 탄성계수를 예측하는 해석식 및 준실험식 등 많은 기법들이 제안되어 왔지만 사용대상에 따라 제약이 있거나, 복합재료를 구성하는 섬유나 기지의 종류에 따라 예측결과가 시험결과와 잘 일치하지 않는 문제점을 가지고 있다. 본 연구에서 전산 균질화 기법을 통해 실제 복합재료 형상과 유사한 대표체적 요소를 선정하여 유한요소 모델링을 수행하고, 주기적 경계조건을 부여하여 등가 탄성계수를 예측하였다. 아울러 기존의 예측식 및 시험 결과와 비교하여 그 성능을 검증하였으며, 인공위성 복합재료 패널 구조해석결과에 미치는 영향에 대해 검토하였다.

• 지질공학
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• 제16권3호
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• pp.227-233
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• 2006

암반은 일반적으로 생성환경 및 지질학적 조건에 따라 균질하지 못하며, 특히 기질과 역의 성분차이가 심한 역암 또는 각력암이나 핵석 등은 복합물질로 구성된 암반에 해당된다. 이들 복합 지반물질의 역학적 특성은 역과 기질의 역학특성과 분포특성 등에 따라 달라진다. 사면과 터널 및 지하구조물의 설계를 위한 이들의 역학성 평가는 매우 중요하지만 일반적으로 행해지는 암반분류법에 의한 이들의 평가는 부적절하다. 따라서 본 연구에서는 복합지반물질의 역학성 평가를 위해 균질화법을 적용하였다. 역의 함유량, 크기, 기질의 고결도, 분급, 경사 등의 인자를 고려한 조합에 의해 총 49개의 해석모델을 작성하여 탄성해석을 실시하였다. 해석결과는 역암이나 핵석같은 복합지반물질의 역학성 계산에 적용될 수 있다.

• 한국전산구조공학회논문집
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• 제31권2호
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• pp.105-114
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• 2018

본 연구에서 페리다이나믹 이론 모델을 이용하여 준정적하중과 동적 하중, 균열전파와 분기균열 패턴 그리고 등방성재료, 직교 이방성 재료의 균열 진전 해석 등 다양한 조건을 고려한 전산 시뮬레이션을 수행하여 그 적합성을 검토하였다. 초기 균열은 없지만 중심에 홀이 있는 등방성 재료, 초기 균열이 존재하는 등방성 및 이방성 재료에 대한 전산 시뮬레이션이 수행되었다. 조정 동적 완화 기법이 사용되어 준정적 하중을 모사하였고, 이방성 재료 해석에서는 고전 연속체 역학과 페리다이나믹의 변형률 에너지를 고려한 균질화 방법이 사용되었다. 균열 전파와 분기 균열이 성공적으로 확인되었으며 파괴 거동의 시작과 그 방향 역시 페리다이나믹 이론으로 확인되었다. 페리다이나믹을 균질화 방법을 사용하여 비교적 복잡한 이방성 재료에 적용한 경우 역시 실험 결과 값과 비교하여 검증하였다.

• 한국분말재료학회지
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• 제11권1호
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• pp.55-59
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• 2004

TiNi bodies were produced from (Ti＋Ni) powder mixture by spark-plasma sintering procerg. The sintering behavior was investigated through the measurement of change in density, densification rate, phase analysis and microstructure. Irrespective of heating rate, sintered bodies with above 97％ relative density could be obtained. TiNi with B2 structure was confirmed as the major phase and $Ti_2Ni,\;TiNi_3$, unreacted Ti, Ni as the second phase. Increase in heating rate suppressed a formation of intermediate phase during sintering process. Increase in holding time at sintering temperature led to a compositional homogenization.

• 한국관광식음료학회:학술대회논문집
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• 한국관광식음료학회 2003년도 학술논문발표집
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• pp.19-35
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• 2003

This study was carried out to find a cholesterol removal rate, flavor development, and bitter amino acid productions in Cheddar cheese treated with -cyclodextrin (${\beta}-CD$): 1) Control (no homogenization, no ${\beta}--CD$), and 2) Milk treatment (1000 psi milk homogenization, 1% ${\beta}-CD$). The cholesterol removal of the cheese were 79.3%. The production of short-chain free fatty acids (FFA) increased with a ripening time in both control and milk treated cheese. The releasing quantity of short-chain FFA was higher din milk treated cheese than control at 5 and 7 mo ripening. Not much difference was found in neutral volatile compounds production between samples. In bitter-tasted amino acids, milk treatment group produced much higher than control. In sensory analysis, texture score of control Cheddar cheese significantly increased, however, that in cholesterol-reduced cheese decreased dramatically with ripening time.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1390-1395
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• 2005

To analyze the effects of oyster shell particles, inserted in the self-hardening matrix such as cement paste, on strength, homogenization analysis using micro structure was used to estimate and assess the apparent elastic modulus of oyster shell particle. DIB modeling technique was used to represent of the micro structure of oyster shell mixed concrete. The results showed that the apparent elastic modulus of LOS (large oyster shell particle) was changed with the amount of LOS inserted. In particular, when the amount of LOS was 200% of the weight of cement, the apparent elastic modulus of LOS tended to decrease rapidly. This could mean that the strength of oyster shell mixed concrete is much affected by LOS inserted material in mixed ratio of 200%.

• 대한기계학회논문집A
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• 제29권4호
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• pp.518-525
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• 2005

The electromagnetic noise generates when natural frequencies of a stator core with wingdings and frame coincide with or approach natural frequencies of the magnetic motive force. In order to suppress such noise, the estimation of natural frequencies of the motor is important at the design stage. However, the natural frequency analysis is not so easy because motor stator is in the laminated plate structure and windings are composed of wires, insulation sheets and vanishs. Thus the accurate prediction of the equivalent material properties of windings becomes an essential task. In this paper, we derive the equivalent material properties using homogenization methods.

• 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.

• Structural Engineering and Mechanics
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• 제57권2호
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• pp.369-387
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• 2016

In this work, random homogenization analysis for the effective thermal properties of a three-dimensional composite material with unidirectional fibers is presented by combining the equivalent inclusion method with Random Factor Method (RFM). The randomness of the micro-structural morphology and constituent material properties as well as the correlation among these random parameters are completely accounted for, and stochastic effective thermal properties as thermal expansion coefficients as well as their correlation are then sought. Results from the RFM and the Monte-Carlo Method (MCM) are compared. The impact of randomness and correlation of the micro-structural parameters on the random homogenized results is revealed by two methods simultaneously, and some important conclusions are obtained.