• Proceedings of the Korean Vacuum Society Conference
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• 1998.06a
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• pp.85-85
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• 1998

• Proceedings of the Korean Vacuum Society Conference
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• 1994.02a
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• pp.41-42
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• 1994

• Proceedings of the Materials Research Society of Korea Conference
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• 1995.11a
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• pp.85-85
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• 1995

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.61-61
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• 1993

• Proceedings of the Korean Vacuum Society Conference
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• 1997.02a
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• pp.132-133
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• 1997

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.4-4
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• 2007

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.806-815
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• 1996

The interlaminar fracture behavior of woven laminates under static and cyclic loadings has been studied using DCB(double cantilever beam) specimens. The effects of surface treatment and stiching on the fracture behavior of composite laminates are investigated experimentally. Fracture toughness has been improved by surface treatment because the surface treatment can change the fracture mechanism of laminates. SCB(stitched cantilever beam) model has been proposed to quantify the effect of through-thickness resinforcement(stiching) in improving the delamination crack growth resistance. Distributed loads which are transfered to through-thickness fibers can be calculated by the SCB model. And fracture energy increase due to the distributed load can be predicted by a power function of the distributed load. A new parameter agreed well proposed predict fatigue crack growth rate. The predictions using this parameter agreed well with the experimental data.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.501-504
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• 2004

High quality GaN layer was obtained on 0001 sapphire substrate using ammonia($NH_3$) as a nitrogen source by gas source molecular beam epitaxy. As a result, RHEED is used to investigate the relaxation processes which take place during the growth of GaN. In-situ RHEED(reflection high electron energy diffraction) appeared streaky-like pattern. The full Width at half maximum of the x-ray diffraction(FWHM) rocking curve measured from plane of GaN has exhibited as narrow as 8arcmin and surface roughness was 7.83nm. Photoluminescence measurement of GaN was investigated at room temperature, where the intensity of the band edge emission is much stronger than that of deep level emission. The GaN epitaxy layer according to various growth condition was investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.834-842
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• 1998

This paper examines the crack growth behavior of 7075-T651 and 5052-H32 aluminum alloy under high-low block loading condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure ae investigated by compliance method. The applied stress ratios are R=0.15, 0.0, -0.15 and R=-0.15, 0.0, 0.15. The crack growth rate was found to increase as the load amplitude increases. However,${\bigtriangleup}K_eff$ was almost independent on the stress ratio. The experimental constants of 7075-T651 and 5052-H32 in Paris law were c`=1-1.3${\times}{10^-7},m`=3~3.2 and c`=4~6{\times}{10^-9}, m`=4.3-4.8$, respectively. $K_op$ of 7075-T651 and 5052-H32 becomes smaller as the stress ratio decreases. It seems that the crack closure affects $K_op$.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.5
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• pp.471-477
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• 2015

In this study, the property of crack propagation and growth at high tension steel plate existed with center crack is investigated. The behaviors of fracture mechanics due to existence or not of hole near the center crack in specimen and the length of crack length are investigated when the load is applied at the one side end of specimen. Stress, deformation and deformation of this specimen are evaluated through simulation analysis. By the analysis results at this study, stress intensity factors are obtained. The damage happened at machine or structure with crack or defect can be estimated on the basis of study results.