• Structural Engineering and Mechanics
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• v.4 no.6
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• pp.631-644
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• 1996

Geomaterials such as soil and rock are composed of discrete elements of microstructures with different grains and microcracks. The studies of these microstructures are of increasing interest in geophysics and geotechnical engineering relating to underground space development We first show experimental results undertaken for direct observation of microcrack initiation and propagation by using a newly developed experimental system, and next a homogenization method for treating a viscoelastic behavior of a polycrystalline rock.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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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.

• Fibers and Polymers
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• v.2 no.2
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• pp.81-85
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• 2001

The effects of rate of phase separation to ester interchange reactions and the repulsive pair interaction energy on the phase behavior in a phase-separated immiscible polyester blend are investigated using a Monte Carlo simulation method. The time evolution of structure factor and the degree of randomness are monitored as a function of homogenization time. When the phase separation is dominant over ester interchange reactions, the domain size slowly increases with homogenization time. However, when the pair interaction becomes less repulsive, the domain size does not significantly change with homogenization time. On the other hand, when ester interchange reactions are dominant over the phase separation, the homogenization proceeds without a change in the domain size. The higher the extent of phase separation, the lower the increasing rate of the DR. However, when the phase separation is sufficiently dominant, the effect of the extent of phase separation on the increasing rate of the degree of randomness become less significant.

• Structural Engineering and Mechanics
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• v.4 no.6
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• pp.613-630
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• 1996

The homogenization method is used to develop a beam element in space for thermo-mechanical analysis of unidirectional composites. Local stress and temperature field in the microscale are described using the function of homogenization. The global (macroscopic) behaviour of the structure is supposed to be that of a beam. Beam-type kinematical hypotheses (including independent shear rotations) are hence applied and superposed on the microdescription. A macroscopic stiffness matrix for such a beam element is then developed which contains the microscale properties of the single cell of periodicity. The presented model enables us to analyse without too much computational effort complicated composite structures such as e.g. toroidal coils of a fusion reactor. We need only a FE mesh sufficiently fine for a correct description of the local geometry of a single cell and a few of the newly developed elements for the description of the global behaviour. An unsmearing procedure gives the stress and temperature field in the different materials of a single cell.

• Structural Engineering and Mechanics
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• v.11 no.4
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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.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2120-2130
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• 2024

This study significantly reduced the seismic analysis time of PCSG assembly by introducing a reduced model using homogenization and sub-structuring methods. The homogenization method was applied to the primary and secondary micro-channel sheets, and the sub-structuring method was applied to the PCSG module sets. Modal analysis and frequency response analysis were then performed to validate the accuracy of the reduced model. The analysis results were compared with the full model and it was confirmed that the reduced model provided almost the same analysis results as the full model. To verify the computational efficiency of the reduced model, the computational time was then compared with the full model, and it was confirmed that the modal analysis time was reduced by 3.42 times and the frequency response analysis time was reduced by 4.59 times.

• Journal of the Chungcheong Mathematical Society
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• v.21 no.1
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• pp.71-78
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• 2008

We introduce the homogenized differential systems for fissured medium equations representing the small temperature variation or densities of a fluid in a system consisting of two components.

• Structural Engineering and Mechanics
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• v.67 no.5
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• pp.527-544
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• 2018

In this paper, the effect of homogenization models on stress analysis is presented for functionally graded plates (FGMs). The derivation of the effective elastic proprieties of the FGMs, which are a combination of both ceramic and metallic phase materials, is of most of importance. The majority of studies in the last decade, the Voigt homogenization model explored to derive the effective elastic proprieties of FGMs at macroscopic-scale in order to study their mechanical responses. In this work, various homogenization models were used to derive the effective elastic proprieties of FGMs. The effect of these models on the stress analysis have also been presented and discussed through a comparative study. So as to show this effect, a refined plate theory is formulated and evaluated, the number of unknowns and governing equations were reduced by dividing the transverse displacement into both bending and shear parts. Based on sinusoidal variation of displacement field trough the thickness, the shear stresses on top and bottom surfaces of plate were vanished and the shear correction factor was avoided. Governing equations of equilibrium were derived from the principle of virtual displacements. Analytical solutions of the stress analysis were obtained for simply supported FGM plates. The obtained results of the displacements and stresses were compared with those predicted by other plate theories available in the literature. This study demonstrates the sensitivity of the obtained results to different homogenization models and that the results generated may vary considerably from one theory to another. Finally, this study offers benchmark results for the multi-scale analysis of functionally graded plates.

• KSBB Journal
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• v.26 no.5
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• pp.400-406
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• 2011

This study was investigated to improve the saccharification yield of Ulva pertusa Kjellman by the high pressure homogenization process. It was found that the high pressure homogenization pretreatment effectively destructed the cell wall structures only by using water. The high pressure homogenization process was operated under various conditions such as 10000, 20000 or 30000 psi with different recycling numbers. The optimal condition was determined as 30000 psi and 2 pass of recycling numbers and the sugar conversion yields were 16.02 (%, w/w) of glucose and 14.70 (%,w/w) of xylose, respectively. In the case of enzymatic treating the hydrolyzates with 5 FPU/glucan of celullase and 100 units/mL of amyloglucosidase, 65.8% of carbohydrates was converted into glucose. Using the hydrolysates of Ulva pertusa Kjellman, 48.7% of ethanol was obtained in the culture S.cerevisiae. These results showed that the high pressure homogenization process could efficiently hydrolyze the marine resource by using only water for bioethanol production.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.1950-1958
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• 2024

For the pressurized water reactor two-step calculation, the traditional assembly homogenization and two-group neutron diffusion calculation have been widely used. When it comes to the core pin-by-pin simulation, many models and techniques are different and unsettled. In this paper, the homogenization methods based on the pin discontinuity factors and super homogenization factors are used to get the pin-cell homogenized parameters. The heterogeneous leakage model is applied to modify the infinite flux spectrum of the single assembly with reflective boundary condition and to determine the diffusion coefficients for the SP3 solver which is used in the core simulation. To reduce the environment effect of the single-assembly reflective boundary condition, the online method for the SPH factors updating is applied in this paper, and the functionalization of SPH factors based on the least-squares method will be pre-made alone with the table of the group constants. The fitting function will be used to update the thermal-group SPH factors with a whole-core pin-by-pin homogeneous solution online. The three-dimensional Watts Bar Nuclear Unit 1 (WBN1) problem was utilized to test the performance of pin-by-pin calculation. And numerical results have demonstrated that PWR pin-by-pin core calculation has more accurate results compared with the traditional assembly-homogenization scheme.