• 대한기계학회논문집
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• 제18권5호
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• pp.1245-1252
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• 1994

A solution of heat transfer problems of composite materials has been tried using homogenization technique. Homogenization technique, which was derived by applying asymptotic expansion to the standard finite element method, helped compute the equivalent thermal conductivity matrices of base cells which constituted the composite material with repeated patterns. The homogenization technique made it possible to compute the solution of the heat transfer problem of composite materials with lower degrees of freedom compared to those of other numerical methods. The equivalent thermal conductivities computed by computed by homogenization technique are also applicable to other numerical methods such as finite difference method.

• 전산구조공학
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• 제8권3호
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• pp.51-57
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• 1995

다공평판에서의 응력해석에 균질화기법이 사용되었다. 표준적인 유한요소법에 미소좌표계확장을 도입한 균질화 기법은 다공평판을 microscale 모델과 macroscale 모델로 나누어 해석한다. 같은 패턴이 반복되는 최소의 기하학적단위를 microscale에서의 단위구조로 취하여 등가물성치를 산출한다. Macroscale 모델에서는 다공평판을 구멍이 없는 일반평판으로 가정하여 앞에서 산출한 등가물성치와 주어진 경계조건을 이용하여 변위를 산출하고, microscale 모델에서 다공평판의 응력을 계산한다. 균질화기법은 다공평판외에도 기본단위의 반복도가 심한 복합구조의 응력해석에서 유용한 전처리 및 후처리 개념을 제공하며, 계산에 필요한 자유도를 현저히 줄이면서 적절한 등가물성치와 응력분포의 계산을 가능케 하여준다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1997년도 가을 학술발표회 논문집
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• pp.1-7
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• 1997

Equivalent thermal conductivities and elasticity properties of woven fabric composites are computed using homogenization technique. The computational results show that the strength and thermal conductivity linearly increase with fiber volume fraction and that the variations of undulation of fibers has little effect on equivalent material properties. Homogenization technique is proved useful in the study of woven fabric composites and may find a lot more applications in the area.

• 대한기계학회논문집A
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• 제22권3호
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• pp.588-594
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• 1998

Reliable three-dimensional models of woven fabric composites had scarcely been proposed for their geometric complexity. Simplified models, mostly one- or two-dimensional, currently used are not considered effective enough because of their oversimplifications. In this paper, the equivalent thermal conductivities and elasticity properties of woven fabric composites are computed using homogenization technique. The computational results show that the strength and thermal conductivity linearly increase with fiber volume fraction and that the variations of undulation of fibers has little effect on equivalent material properties. Homogenization technique is proved useful in the study of woven fabric composites and may find a lot more applications in the area.

• Structural Engineering and Mechanics
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• 제38권4호
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• pp.503-516
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• 2011

Uncertainty in concrete properties, including concrete modulus of elasticity and modulus of rupture, are predicted by developing a microstructural homogenization model. The homogenization model is developed by analyzing a concrete representative volume element (RVE) using the finite element (FE) method. The concrete RVE considers concrete as a three phase composite material including: cement paste, aggregate and interfacial transition zone (ITZ). The homogenization model allows for considering two sources of variability in concrete, randomly dispersed aggregates in the concrete matrix and uncertain mechanical properties of composite phases of concrete. Using the proposed homogenization technique, the uncertainty in concrete modulus of elasticity and modulus of rupture (described by numerical cumulative probability density function) are determined. Deflection uncertainty of reinforced concrete (RC) beams, propagated from uncertainties in concrete properties, is quantified using Monte Carlo (MC) simulation. Cracked plane frame analysis is used to account for tension stiffening in concrete. Concrete homogenization enables a unique opportunity to bridge the gap between concrete materials and structural modeling, which is necessary for realistic serviceability prediction.

• 대한기계학회논문집A
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• 제31권3호
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• pp.388-394
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• 2007

Many engineering problems require the calculation of effective material properties of a structure which is composed of repeated micro-structures. The homogenization method has been used to calculate the effective (homogenized) properties of composites and several homogenization procedures for different physical fields have been introduced. This research describes the modified homogenization technique for magnetostatic problems. Assuming that the material is periodically repeated, its effective permeability can be prescribed by calculating the homogenized magnetic reluctivity using the finite element analysis of the micro unit cell. Validity of the suggested method is confirmed by comparing the results by the energy based method as well as the widely known homogenization method.

• Journal of Periodontal and Implant Science
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• 제27권1호
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• pp.263-290
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• 1997

Homogenization technique is employed to investigate the series of stress analyses of mandible for three different types of dental implants. This technique helps to make proper material model of bone and analyze such a non homogeneous structure at the level of individual microstructural unit. The stress analyses with homogenization technique show much higher stress level in the sponge bone, compared to those of conventional FEM. It also manifested that even a minor lateral force results in crucial stresses in the dental implant system and that the macroscale model should take the shape and size after real mandible to produce reasonable solution in the analyses of dental implant systems. The shapes of dental implants simulated in this study are rectangular-cross-sectioned type, hemi-sphere rooted type, and wedge type implant. The stress states of mandible with hemisphere rooted type implant and wedge type implant show similar levels, while those with sectioned rectangular implant results in higher stresses. It is suggested that the distance between the implant tip and cortical bone be kept far enough to prevent stress concentrations in the mandible.

• Structural Engineering and Mechanics
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• 제11권4호
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• pp.373-392
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• 2001

The main idea behind the paper is to present two alternative methods of homogenization of the heat conduction problem in composite materials, where the heat conductivity coefficients are assumed to be random variables. These two methods are the Monte-Carlo simulation (MCS) technique and the second order perturbation second probabilistic moment method, with its computational implementation known as the Stochastic Finite Element Method (SFEM). From the mathematical point of view, the deterministic homogenization method, being extended to probabilistic spaces, is based on the effective modules approach. Numerical results obtained in the paper allow to compare MCS against the SFEM and, on the other hand, to verify the sensitivity of effective heat conductivity probabilistic moments to the reinforcement ratio. These computational studies are provided in the range of up to fourth order probabilistic moments of effective conductivity coefficient and compared with probabilistic characteristics of the Voigt-Reuss bounds.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.79-81
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• 1994

A solution of magnetic fields for amorphous core transformer has been tried using homogenization technique. The technique, which is derived by applying asymptotic expansion to the standard finite element method, is helpful to analyse a joint part of amorphous core transformer microscopically. A butt-lap-step joint type of lamination method is modeled and its equivalent reluctivity is calculated to analyse various quantities of the magnetic fields. The algorithm is also applicable to other electric devices which have complicated material structure with repeated patterns.

• 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.