• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.04a
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• pp.156-163
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• 1997

Recently, attempts have been made to be join ceramics to metals in order to make up for the brittleness of ceramics. The difference in the coefficients of linear expansion of the two materials joined at high temperature will cause residual stress, which has a strong influence on the strength of the bonded joints. In this paper, the residual stress distribution and stress intensity factors of the ceramic/metal bonded joints were analyzed by 2-dimensional elastic boundary element method. Fracture toughness tests of ceramic/metal bonded joints with an interface crack were carried out. So the advanced method of quantitative strength evaluation for ceramic/metal bonded joints is to be suggested. Fracture surface and crack propagation path were observed using scanning electron microscope.

• Journal of Korea Foundry Society
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• v.28 no.4
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• pp.175-178
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• 2008

우주선, 항공기, 수송차량 등은 기능은 집적 다양화 그리고 성능의 고도와 됨에 따라 에너지 효율성을 위해 구조부재의 경량화가 중요성은 증가되고 있다. 경량화 구조부재 재료 중에는 알루미늄 합금, 세라믹, 복합재료 등이 개발되어 우주선, 항공기, 수송차량 구조부재에 적용하기 위한 많은 연구가 이루어지고 있다. 이들 중, 20세기 초 알루미늄합금이 초 경량화 구조부재로서 많이 이용되었다. 본 논문에서는 경량화 재료 중 이방성을 가지는 복합재료를 구조부재에 적용하였다. 그러나 구조부재에 적용되기 위한 이방성 복합 재료는 강한 충격 이후 취성의 특징 때문에 하중과 흡수에너지가 급속히 감소하는 단점을 가지고 있다. 그래서 이방성 복합재료의 각 층간을 완전히 접합하여 성질이 매우 우수한 부재를 제작할 수 있는 Autoclave 성형법으로 제작하였다. 이방성 복합재료 중 CFRP를 설계 메커니즘 변수에 따라 Autoclave 성형을 하고 하중과 흡수에너지가 높음 평가하기 위해 굽힘실험을 하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.1
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• pp.7-11
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• 2006

Since ceramic layers coated on machinery components inevitably experience the changes in their properties it is necessary to evaluate the characteristics of ceramic coating layers nondestructively for a reliable use of coated components and 4heir remaining life prediction. To address such a need, in the present study, an ultrasonic backward radiation technique is applied to investigate the characteristics of leaky Rayleigh surface waves propagating through the very thin TiN ceramic layers coated on AISI 1045 steel or austenitic 304 steel substrate with three different conditions of surface roughness, coating layer thickness and wear condition. In the experiments performed in the present work, the peak angle and the peak amplitude of ultrasonic backward radiation profile varied sensitively according to three specimen preparation renditions. in fact, this result demonstrates a high possibility of the ultrasonic backward radiation as an effective tool for the nondestructive characterization of the resting layers even in such a thin regime.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.10
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• pp.966-978
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• 2011

Transpiration cooling is the most effective cooling technique for the high-performance liquid rockets and air-breathing engines operating in aggressive environments with higher pressures and temperatures. When applying transpiration cooling, combustor liners and turbine blades/vanes are cooled by the coolant(air or fuel) passing through their porous walls and also the exit coolant acting as an insulating film. Practical implementation of the cooling technique has been hampered by the limitations of available porous materials. But advances in metal-joining techniques have led to the development of multi-laminate porous structures such as Lamilloy$^{(R)}$ fabricated from several diffusion-bonded, etched metal thin sheets. And also with the availability of lightweight, ceramic matrix composites(CMC), transpiration cooling now seems to be a promising technique for high-performance engine cooling. This paper reviews recent research activities of transpiration cooling and its applications to gas turbines, liquid rockets, and the engines for hypersonic vehicles.