• The Journal of Engineering Geology
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• v.20 no.3
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• pp.271-279
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• 2010

Time-dependent behavior similar to secondary deformation related to mineral dissolution is easily observed when performing a laboratory pressure experiment. In this research, to observe the dissolution of quartz found in bentonite used as buffer material for the geological disposal of high-level waste (HLW) under conditions of high pH, we calculated the diffusion of $OH^-$ ions and the behavior of quartz dissolution using the homogenization analysis method. The results reveal that the rate of quartz dissolution is proportional to the temperature and interlayer water thickness. In particular, in a high-pH environment, the reacted area (and therefore the dissolution rate) increases with decreasing interlayer water thickness.

• Journal of Korea Foundry Society
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• v.30 no.6
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• pp.235-240
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• 2010

The evolution of microstructure and phases of Mg-10Al-Mn alloy by cooling plate method during homogenization treatment have been investigated with metallographic analysis, scanning electron microscopy and energy dispersive spectroscopy. The ingots used for this experiment were prepared by cooling plate and homogenization heat treatment was performed at 300 and $400^{\circ}C$ for various holding times (0, 1, 4, 8 and 12h). The casting ingots were consisted of the fine grains and eutectic phases. And, these eutectic phases were dissolved into the matrix during homogenization treatment at $400^{\circ}C$ but the lower temperature (at $300^{\circ}C$) did not be.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.1
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• pp.51-61
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• 2000

This paper discusses the homogenization method to determine effective average elastic constants of a linear structure by considering its microstructure. A detailed description on the homogenization method is given for the linear elastic material and then the finite element approximation is performed for an investigation of elastic properties. An asymptotic expansion is carried out in the cross-section area, or in the unit cell. Two and three lay-up structures made up of individual isotropic constituents are chosen for numerical examples to check discrepancies between results generated by this theoretical development and the conventional approach. Asymptotic characteristics of the process in extracting the stiffness of structure locally formed by spatial repetitions yield underestimated values of stiffness. These discrepancies are detected by the asymptotic corrective term which is ascribed to considerations of microscopic perturbations and proved in the finite element formulation. The asymptotic analysis is the more reasonable in analysing the composite material, rather than the conventional approach to calculate the macroscopic average for elastic properties.

• Journal of Powder Materials
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• v.30 no.2
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• pp.146-155
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• 2023

The Ti-6Al-4V lattice structure is widely used in the aerospace industry owing to its high specific strength, specific stiffness, and energy absorption. The quality, performance, and surface roughness of the additively manufactured parts are significantly dependent on various process parameters. Therefore, it is important to study process parameter optimization for relative density and surface roughness control. Here, the part density and surface roughness are examined according to the hatching space, laser power, and scan rotation during laser-powder bed fusion (LPBF), and the optimal process parameters for LPBF are investigated. It has high density and low surface roughness in the specific process parameter ranges of hatching space (0.06-0.12 mm), laser power (225-325 W), and scan rotation (15°). In addition, to investigate the compressive behavior of the lattice structure, a finite element analysis is performed based on the homogenization method. Finite element analysis using the homogenization method indicates that the number of elements decreases from 437,710 to 27 and the analysis time decreases from 3,360 to 9 s. In addition, to verify the reliability of this method, stress-strain data from the compression test and analysis are compared.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.3
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• pp.115-122
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• 2004

When porous materials are dried, the particles flocculate into fish-net structure in gel phase. In order to exactly analyze the stress distribution of porous materials during drying process, the elastic tensor of microscopic gel structures has to be predicted considering pore shapes as well as porosities of porous materials. The elastic characteristics of porous materials associated with porosities were predicted analyzing microscopic gel structures with circular and cross pores via homogenization method and the drying processes of the electric porous ceramic insulator were simulated using finite element method (FEM). Comparing analysis results between consideration and negligence of pores, the deformed shape and distributions of temperature and moisture were similar but the residual stress was significantly different.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.159-163
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• 2004

This study was conducted to calculate the permeability coefficient in a single fracture while taking the true fracture geometry into consideration. The fracture geometry was measured using the confocal laser scanning microscope (CLSM). The CLSM geometry data were used to reconstruct a fracture model for numerical analysis using a homogenization analysis (HA) method. The HA is a new type of perturbation theory developed to characterize the behavior of a micro-inhomogeneous material that involves periodic microstructures. The HA permeability was calculated based on the local geometry and local material properties (water viscosity in this case). The results show that the permeability coefficients do not follow the theoretical relationship of the cubic law.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.79-88
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• 2005

Evaluating the effective properties of materials containing various types of in-homogeneities is an important issue in the analysis of structures composed of those materials. A simple and effective method for the purpose is to impose the periodic displacement boundary conditions on the finite element model of a unit cell. Their theoretical background is explained based on the purely kinematical relations in the regularly spaced in-homogeneity problems, and the strategies to implement them into the analysis and to evaluate the homogenized material constants are introduced. The creep behavior of a thin sheet with square arrayed rectangular voids is characterized, where the orthotropy is induced by the presence of the voids. The homogenization method is validated through the comparison of the analysis of detailed model with that of the simplified one with the effective parameters.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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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.

• Journal of Aerospace System Engineering
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• v.15 no.6
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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.

• Advances in nano research
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• v.7 no.2
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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.