• Journal of Mechanical Science and Technology
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• v.16 no.8
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• pp.1117-1126
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• 2002

A conducting crack in an electrostrictive ceramic under combined electric and mechanical loading is investigated. Analysis based on linear dielectric model predicts that the surfaces of the crack are not open completely but they are contact near the crack tip. The complete solution for the crack with a contact zone in a linear electrostrictive ceramic under combined electric and mechanical loading is obtained by using the complex variable formula. The asymptotic problems for a semi-infinite crack with a partial opening zone as well as for a fully open semi-infinite crack in a nonlinear electrostrictive ceramic are analyzed in order to investigate the effect of the electrical nonlinearity on the stress intensity factor under small scale nonlinear conditions. Particular attention is devoted to a finite crack in the nonlinear electrostrictive ceramic subjected to combined electric and mechanical loading. The stress intensity factor for the finite crack under small scale nonlinear conditions is obtained from the asymptotic analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.2
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• pp.162-172
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• 1998

A numerical study of premixed combustion within a porous ceramic burner (PCB) is performed to understand flame behavior with respect to various model parameters. Basic flame structure within the porous ceramic burner and species profiles such as NO and CO are examined. Sensitivity analysis of flame speed, gas and solid temperature, NO and CO emission from the burner with respect to reaction steps and various physical properties of the ceramic material is applied to find the most significant parameters in selection of porous materials for the porous ceramic burner. Effects of thermal conductivity, extinction coefficient and scattering albedo on the burner characteristics are studied through the sensitivity analysis. The results of sensitivity study reveal the order of importance in ceramic material properties to get suitable burner performance. Scattering albedo, which governs the ratio of absorbed energy by the ceramic material to total radiative energy transferred, is one of the most important parameters in the material properties since it affects the actual absorbed radiation rate and thus it largely affects the flame structure. Through the study, it is found that the sensitivity study can be used to estimate the flame behavior within the porous ceramic burner more effectively.

• Tribology and Lubricants
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• v.8 no.2
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• pp.64-72
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• 1992

The recent trends of rotating machinery demand high speed and high temperature operation, and the bearing with new material is required to be developed. Ceramic, especially silicon nitride, have been receiving attention as alternative material to conventional bearing steel. Ceramic ball bearing offers major performance advantages over steel bearing, for instance, high speed, maginal lubrication, high temperature, improved corrosion resistance and nonmagnetic capabilities etc.. In this paper, the mechanical characteristics of ceramic ball bearing (hybrid ceramic bearing and all ceramic bearing) were investigated, and the characteristics of ceramic bearing were compared with that of steel bearing. Deep groove ball bearing 6208 was taken the object of analysis. The main results of analysis were followings: the radial stiffness of hybrid and all ceramic bearing were 112% and 130% that of steel bearing, and the axial stiffness of all ceramic bearing was 110% that of steel bearing. According as rotating speed was up, the ball load, the contact angle, the contact stress and the spin-to-roll ratio between ball and raceway of ceramic bearing were far smaller than these of steel bearing. And there was not a significant difference between the minimum film thickness of ceramic bearing and steel bearing. It is expected that this research is contributed to enhanced fundamental technology for the practical applications of ceramic ball bearing.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1163-1167
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• 2003

Effective properties of ceramic matrix plain woven textile composites were calculated using finite element analysis. The considered geometry is a unit cell of plain weave and the analysis was performed by commercial finite element program, ANSYS. The materials for analysis are 3 types for matrix, 1 type for fiber with various volume fraction. The result indicates that the effective properties of ceramic matrix composites can be controlled by the volume fraction. The result can be used for numerical analysis using ceramic matrix composites.

• Journal of the Korea Institute of Building Construction
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• v.12 no.4
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• pp.386-392
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• 2012

In this study, life cycle cost (LCC) is analyzed according to insulation panel system type using a deterministic LCC analysis method. Through this analysis, it was found that the construction cost in the deterministic LCC analysis for Ceramic panels was low compared to the construction cost for metal and stone panels. Also, the difference in cost between the Ceramic panel and the metal panel was about 2 times. In the area of maintenance cost, it was found to be similar to the previously analyzed construction cost, in which the metal panel has the highest cost due to the high cost of construction and the frequent need for maintenance. In the case of the stone panel, a small difference in cost is shown compared with that of the Ceramic panel, but the cost is higher than the Ceramic panel. Regarding the cost of waste disposal, the Ceramic panel can reduce the cost by at least 1.5 times and up to 2 times compared to other panel systems. Finally, in the analysis of sensitivity according to changes in discount rates, the Ceramic panel and metal panel systems have a similar cost, and the cost of the metal panel is a bit larger than that of other panel systems. Thus, in the subjects used in the analysis, the Ceramic panel system shows the highest economic benefits.

• Structural Engineering and Mechanics
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• v.4 no.6
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• pp.679-702
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• 1996

The finite element method is employed in conjunction with micromechanical modelling in order to assess the performance of ceramic thermal barrier coatings applied to structural components. The study comprises the conditions of the deposition of the coating by plasma spraying as well as the thermal cycling of the coated component, and it addresses particularly turbine blades. They are exposed to high temperature changes strongly influencing the behaviour of the core material and inducing damage in the ceramic material by intense straining. A concept of failure analysis is discussed starting from distributed microcracking in the ceramic material, progressing to the formation of macroscopic crack patterns and examining their potential for propagation across the coating. The theory is in good agreement with experimental observations, and may therefore be utilized in proposing improvements for a delayed initiation of failure, thus increasing the lifetime of components with ceramic thermal barrier coatings.

• Journal of the Korean Ceramic Society
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• v.23 no.2
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• pp.64-70
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• 1986

In this investigation x-ray diffraction method was mainly studied for quantitative analysis of clinker mineral composition. And also optical microscopic observation and Bogue calculation method were applied to compare with the x-ray diffraction method. In the procedure of x-ray diffraction analysis graphite monochromator automatic divergence slit and spinner for sample holder were used for minimizing the error due to the operation of the equipment. Especially the separation of overlapped peaks were proceeded by micro-processor automatically. The results of x-ray diffraction method for synthesized clinker were consistent with the Bogue value and the results of optical microscopic observation. However the results of quantitative analysis of mineral composition or commercial clinker containing solid solution of minor component were different from the Bogue value. On the other hand they agreed reasonably well with results of the optical mic-roscopic observation.

• Journal of the Korean Ceramic Society
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• v.49 no.2
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• pp.146-150
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• 2012

The effects of $Al_2O_3$ on the crystallization behavior of glass compositions in the $Na_2O$-CaO-$SiO_2$ system were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effect of $Al_2O_3$ content on the mechanical properties, density, phase formation, and microstructures of $Na_2O$-CaO-$P_2O_5$-$SiO_2$ glass ceramics were studied. The thermal parameters of each glass were studied by DTA. The density of the glass ceramic samples was measured by Archimedes' method. It was found that the glass-ceramic containing 2.0 molar percent $Al_2O_3$ had desirable sintering behavior and reached an acceptable density. Phase investigation and micro-structural analysis were performed by XRD and SEM, respectively.

• Journal of the Korean Ceramic Society
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• v.48 no.1
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• pp.34-39
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• 2011

Systematic study on relationship between celadon coloring and glaze component was conducted by chromaticity analysis and M$\ddot{o}$ssbauer spectroscopic analysis. The chromaticity ($L^*$, $a^*$, $b^*$ values) and M$\ddot{o}$ssbauer analysis results were correlated to the amount of $Fe_2O_3$, $TiO_2$, MnO, and $P_2O_5$, which are the essential factors influencing celadon coloring. According to chromaticity analysis, celadon glaze color belongs to GY group when the addition of $TiO_2$ was 1.4%, whereas the color belongs to BG group when the addition of $TiO_2$ was 0.1%. For the GY group, the colors change from GY to YR with the decrease of brightness as the addition of $TiO_2$, MnO, and $P_2O_5$ increases. According to M$\ddot{o}$ssbauer analysis results, as the amount of divalent iron ion increases, the $a^*$ and $b^*$ values decrease, on the other hand, $L^*$ value increases. The ratio of divalent iron ion produced in reductive sintering process is found to be 80~95% in this study, which induces the increase of $L^*$ values in celadon glaze.

• Journal of the Korean Ceramic Society
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• v.36 no.10
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• pp.1069-1074
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• 1999