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정연길 漢城大學校 1988 論文集 Vol.12 No.1
개벽지에 발표된 시가작품을 그 형식으로 나누면, 시조, 정형율 시가와 자유시, 산문시로 구분할 수 있다. 우리나라의 시가율조인 4·4조 3·4조 외에 3·3조. 6(3·3)·5조, 7(3·4 또는 4·3)·5조 작품도 더러 보인다. 시조 작품을 발표한 이는 찬간호의 개벽 2편의 무기명 작품과 단단자, 유당, 이상정, 이광수, 박종화, 김형원과 독자문예란의 환경환 등이다.
소결법에 의한 $ZrO_2/Metal$계 경사기능재료에 관한 연구(II)
정연길,최성철 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.1
To analyze the mechanical property and the residual stress in functionally gradient materials(FGMs), disctype TZP/Ni-and TZP/SUS304-FGM were hot pressed using powder metallurgy compared with directly bonded materials which were fabricated by the same method. The continuous interface and the microstructure of FGMs were characterized by EPMA, WDS, optical microscope and SEM. By fractography, the fracture behavior of FGMs was mainly influenced by the defects which originated from the fabrication process. And the defectlike cracks in the FGMs induced by the residual stress have been shown to cause failure. This fact has well corresponded to the analysis of the residual stress distribution by Finite Element Method (FEM). The residual stress generated on the interface (between each layer, and matrix and second phase, respectively) were dominantly influenced on the sintering temperature and the material constants. As a consequence, the interfacial stability and the relaxation of residual stress could be obtained through compositional gradient.
소결법에 의한 $ZrO_2/Metal$계 경사기능재료에 관한 연구(1)
정연길,최성철 한국세라믹학회 1994 한국세라믹학회지 Vol.31 No.3
Functionally gradient materials(FGM), which have the continuous or stepwise variation in a composition and microstructure, are being noticed as the material that solves problems caused by heterogeneous interface of coating or joining. And these materials also expect new functions occured by gradient composition itself. Therefore, to examine possibility of thermal barrier materials, TZP/Mo·FGM and TZP/Ni·FGM were fabricated by sintering method. As to the sintered specimens, sintering shrinkage, relative density and Vicker's hardness in each composition were examined. The phenomena due to the difference of sintering shrinkage velocity during sintering process and the thermal stress induced through differences of thermal expansion coefficient in FGM were discussed. And the structure changes at interface and microsturcture of FGM were investigated. As a results, the difference of shrinkage between ceramic and metal was about 14% in TZP/Mo and 7% in TZP/Ni. The relative density and hardness were considerably influenced by metal content changes. Owing to unbalance of sintering shrinkage velocity between ceramic and metal, various sintering defects were occured. To control these sintering defects and thermal stress, gradient composition of FGM should be narrow. The microstructure changes of FGM depended on the ceramic or metal volume percents and were analogous to the theoretical design.
치아 응용을 위한 /유리침윤 알루미나 이중 층상구조의 접촉손상 및 파괴
정연길,여정구,최성설 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.12
Hertzian contact tests were used to investigate the evolution of fracturedamage in the coating layer as functions of contact load and coating thickness by studying crack patterns in porcelain on glass-infiltrated alumina bilayer system conceived to simulate the crown structure of a tooth. Cone cracks initiated at the coating top surface without delamination at interface and crack propagation to substrate. Preferentially the cracks made multi-cracks at the coating top surface rather than proceeding to interface. The cracks were highly stabilized with wide ranges between the loads to initiate first cracking and to cause final failure im-plying damage-tolerant capability. Finite element modelling was used to evaluate the stress distribution. Maximum tensile stress were responsible for the cracking at the coating layer and had a profound influence on the crack pattern and fracture damage in the layered structure materials.