• Nuclear Engineering and Technology
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• v.26 no.3
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• pp.374-380
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• 1994

A method to simulate the extent of interlinkage of grain boundary gas bubbles to the free surfaces of fuel pellet was developed. With the shape of UO$_2$gain treated as tetrakaidecahedron (TKD)), the interlinked fraction of fission gas bubbles to free surfaces at grain comers was calculated as a function of the radius of grain corner bubbles by the Monte Carlo technique. In spite of two dimensional analysis, the present method shooed reasonable agreement between predicted and measured fuel swelling at the moment that complete bubble interlinkage was achieved. However, for more realistic simulation of interlinkage, grain comer bubbles should be treated three dimensionally.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.7
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• pp.618-623
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• 2006

This study was carried out to select the acceptance test influenced by some quality characteristics of rice, and may provide the basic information on rice grade of appearance quality as distinguished the numerical values. Forty-four Japonica rice varieties mainly cultivated in Korea were evaluated for a consumer acceptance test. Color preferences of rice were highly correlated with appearance quality (r=-0.897**) and redness (r=-0.893**). Especially, appearance quality value resulted from interaction of $redness{\times}yellowness$ values was expected as a specific character used for grade of rice appearance. Shape preferences of rice showed the positive correlation with grain width (r=0.527**) and grain size (r=0.454**). Result of the consumer acceptance test of rice appearance conducted through a cluster analysis revealed five groups. Our study suggests that it may be feasible to be graded by average of quality character among groups, grain width, and grain size in Duncan's multiple range test.

• Advances in materials Research
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• v.1 no.1
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• pp.51-74
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• 2012

A powder metallurgy-based rapid consolidation technique, Plasma Pressure Compaction ($P^2C^{(R)}$), was utilized to produce near-net shape parts of gamma titanium aluminides (${\gamma}$-TiAl). Micron-sized ${\gamma}$-TiAl powders, composed of Ti-50%Al and Ti-48%Al-2%Cr-2%Nb (at%), were rapidly consolidated to form near-net shape ${\gamma}$-TiAl parts in the form of 1.0" (25.4 mm) diameter discs, as well as $3"{\times}2.25"$ ($76.2mm{\times}57.2mm$) tiles, having a thickness of 0.25" (6.35 mm). The ${\gamma}$-TiAl parts were consolidated to near theoretical density. The microstructural morphology of the consolidated parts was found to vary with consolidation conditions. Mechanical properties exhibited a strong dependence on microstructural morphology and grain size. Because of the rapid consolidation process used here, grain growth during consolidation was minimal, which in turn led to enhanced mechanical properties. Consolidated ${\gamma}$-TiAl samples corresponding to Ti-48%Al-2%Cr-2%Nb composition with a duplex microstructure (with an average grain size of $5{\mu}m$) exhibited superior mechanical properties. Flexural strength, ductility, elastic modulus and fracture toughness for these samples were as high as 1238 MPa, 2.3%, 154.58 GPa and 17.95 MPa $m^{1/2}$, respectively. The high temperature mechanical properties of the consolidated ${\gamma}$-TiAl samples were characterized in air and vacuum and were found to retain flexural strength and elastic modulus for temperatures up to $700^{\circ}C$. At high temperatures, the flexural strength of ${\gamma}$-TiAl samples with Ti-50%Al composition deteriorated in air by 10% as compared to that in vacuum. ${\gamma}$-TiAl samples with Ti-48%Al-2%Nb-2%Cr composition exhibited better if not equal flexural strength in air than in vacuum at high temperatures.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.158-160
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• 2005

Zener coefficient on cubic shaped particle was proposed. Most previous researches about Zener coefficient were developed on the assumption that the shape of particle is spherical. But, some particle has other shape, and modification of Zener coefficient needs with shape of particle. In this research, TiN particle that has a cubic shape was considered. A Zener coefficient of a cubic shape TiN was theoretically calculated with appropriate assumptions. And, using a semi-empirical method, Zener coefficient was also measured. Finally, the proposed Zener coefficient was proved by comparing with experimentally measured data.

• Journal of Photoscience
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• v.3 no.3
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• pp.159-161
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• 1996

Photosensitivity of silver halide emulsion depends on the properties of the microcrystals. Size, shape, grain distribution and chemical composition as well as the inner structure or the topography of the latent image specks affect on the optical properties and play an important role in the photographic process. In the present paper, a study on the sensitization of emulsion containing AgBrClI core/shell grains showed that for the given size, shape, halide content and crystal habit, under the optimal conditions the photosensitivity of the heterojunction type grains are different from that of the common regular grains. The optimal photosensitivity was obtained at the iodide content of 2.0 mo1%.

• Transactions of Materials Processing
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• v.10 no.4
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• pp.338-346
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• 2001

Evaluation of microstructural changes is important for process control during open die forging of heavy ingots. The control of forging parameters, such as shape of the dies, reduction, temperature and sequence of passes, is to maximize the forging effects and to minimize inhomogeneities of mechanical properties. The hot working die steel is produced by using the multistage open die forging. The structure is altered during forging by subsequent Precesses of plastic deformation, recrystallization and grain growth. A numerical analysis using an rigid visco-plastic finite element model was performed to predict microstructural evolution of hot working die steel.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.131-135
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• 2001

Evaluation of microstructural changes during open die forging of heavy ingots is important for process control. The objective of the control of forging parameters, such as shape of the dies, reduction, temperature and sequence of passes, is to maximize the forging effects md to minimize inhomogeneities of mechanical properties. The hot working die steel is produced by using the multistage open die forging. The structure is altered during forging by subsequent processes of plastic deformation, recrystallization and grain growth. A numerical analysis using an rigid visco-plastic finite element model was performed to predict microstructural evolution of hot working die steel.

• Journal of Powder Materials
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• v.4 no.2
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• pp.90-99
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• 1997

Densification behavior and grain growth of tool steel powder compacts during pressureless sintering, sinter forging, and hot isostatic pressing were investigated. Experimental data were compared with results of finite element calculations by using the constitutive model of Abouaf and co-workers and that of McMeeking and co-workers. Densification and deformation of tool steel powder compacts were studied by implementing power-law creep, diffusional creep, and grain growth into the finite element analysis. The shape change of a powder compact in the container during hot isostatic pressing was also studied. The theoretical models did not agree well with experimental data in sinter forging, however, agreed well with experimental data in hot isostatic pressing.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.84-91
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• 2005

The role of microstructure is quite significant in fretting of Ti-6Al-4V since its material properties depend strongly on crystallographic texture. In this study, we adopt crystal plasticity theory with a 2-D planar triple slip idealization to account fur microstructure effects such as grain orientation distribution, grain geometry, as well as $\alpha$ colony size. Crystal plasticity simulations suggest strong implications of microstructure effects at fretting contacts.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.107-110
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• 1999

The purpose of this research is for the development of a new type forging equipment H.C.G(Hyundai Continuous Grain-flow) by using two virtual build-up tools rigid viscoplastic FEM and downsized plasticine experiment. This forging equipment consists of consecutive horizontal and vertical pressure while the traditional forging method consists of only vertical pressure. Using this method high quality crankshafts can be forged as it can maintain a continuous grain flow. The factors considered in the development of equipment are die geometry for flawless deformed shape die reaction forces stress/strain distributions and continuous material flow. We carried out several numerical simulations and downsized plasticine experiments for the proper design of the forging equipment. The validity of those simulation results is confirmed by checking with the actual test results. Based on these simulation results the proper design of the H.C.G for ging equipment is enabled.