• Journal of the Korean Society of Safety
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• v.23 no.1
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• pp.12-17
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• 2008

The earn shaft is very important for the safety of automobiles. The earn shaft needs a surface hardening process by high frequency induction to have both strength and toughness. It is required for safety of automobile to consider how the characteristics of tensile strength and toughness are changed according to the condition of surface hardness. In this study, we prepared surface hardened SM53C which is used as cam shaft materials. We examined the tensile strengths according to the depth of surface hardening and the effect of tempering. We also investigated the fracture toughnesses according to the depth of surface hardening(1mm, 2mm).

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.25-32
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• 1993

In composite materials, the fracture perpendicular to the fiber direction usually shows a non-linear behavior accompannying blunting and plastic deformation around the crack tip. In this study, the fracture thoughness in random short fiber SMC composite material and Carbon/Epoxy composite material is estimated by the A.M.(Area Method) and the G.L.M.(Generalized Locus Method) which can determine a stable total energy release rate(G$_T$) not only in highly elghly elastic material but also in highly non-linear materials.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.930-932
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• 2017

In this paper, prediction of progressive interlaminar fracture in curved composite laminates under mode I loading was described. The prediction of progressive interlaminar fracture in curved composite laminates was conducted using cohesive zone model(CZM) in ABAQUS V6.13. Interlaminar fracture toughness used as input parameters in CZM was obtained through mode I, mode II and mixed mode I/II tests. The behaviors of progressive interlaminar fracture for curved composite laminates showed a good agreement between experimental and numerical results.

• Journal of the Korean Ceramic Society
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• v.33 no.3
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• pp.339-347
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• 1996

Mechanical properties(flexural strength hardness fracture toughness) of alumina ceramics were evaluated. Alumina products of four companies were selected and three of those were made in Korea and one of those was made in Japan. The large differences according to manufacturing companies had resulted from flexural strength and weibull modulus which had a wide ranges of 300 to 400 MPa and 5 to 15 respectively. Critical indenstation load which could be neglected the effect of elastic recovery was about 9.8N and Vickers' hardness were about 15 GPa. Fracture toughnesses were evaluated by IF and ISB method. It was more preferable to the average at one indentation load that fracture toughness were obtained from the slope of the relationship between indentation load and crack length in IF method and between indentation load and fracture load in ISB method and fracture toughness was about 4 MPa·m1/2.

• Journal of the Korean Ceramic Society
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• v.29 no.5
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• pp.357-366
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• 1992

Residual organics were considered as impurity in Sol-Gel method. The purpose of this study was to find the conditions to contain as much residual organics as possible in silica gel prepared from TEOS(tetraethylortho-silicate) by Sol-Gel method. Residual organics are to be expected to have reduction effect on synthesizing Si3N4 from silica gel. The results of this study are follows: 1) The maximum content of entrapped carbon was 19.8 wt.%(C/SiO2=0.25 wt.ratio) in silica gel synthesized under the conditions 1.5 fold mole water for incomplete hydrolysis, 2.5 fold mole phenol as a solvent and 0.1 fold mole HCl as a catalyst to TEOS. 2) Silica gel with organics entrapped by Sol-Gel method had a positive effect on the formation of Si3N4 compared with commercial silica gel. 3) Sintered body of synthesized $\alpha$-Si3N4 with Y2O3 and Al2O3 as additives at 175$0^{\circ}C$ in N2 atmosphere showed bending strength, 602$\pm$20 MPa and frature toughness 4.45$\pm$0.15 MPa.m1/2.