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RISS 인기검색어
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김민건,지정근,Kim, Min-Gun,Ji, Jueng-Keun 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.1
Rotary bending fatigue tests were carried out on the nitrided titanium in order to investigate the effect of nitriding layer on fatigue limit. Main results obtained are as follows. (1) The fatigue limit of nitrided pure titanium is remarkably reduced because of enlargement of grain size at high heat treating temperature and high stress field created from the elastic interaction in the compound layer. (2) Further test using specimen which was removed nitrified layer gradually, were also conducted and it was found that by removing the compound layer the fatigue limit recovered as the level of basic material and rather increased by coming of a diffusion layer. Therefore it is concluded that the surface compound layer generated by nitriding treatment reduced the fatigue limit but diffusion layer increased it.
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고강도 구상흑연주철의 피로한도에 미치는 2상 기지조직의 영향
김진학,지정근,김민건,Kim, Jin-Hak,Ji, Jueng-Keun,Kim, Min-Gun 강원대학교 산업기술연구소 1999 産業技術硏究 Vol.19 No.-
Rotary bending fatigue tests were performed to investigate the effects of 2-phase matrix structure on fatigue limit with prepared specimens in high strength ductile irons. Two types of the specimens with different microstructures have been used. Series A has sorbite and series B has bainite. Fatigue limits of both specimens are improved comparing with as cast specimen. The fatigue limit is higher in series B than in series A. The reason why the fatigue limit of series A shows inferiority to that of series B is due to the transition of micro fatigue cracks to mesocrack occurs very rapidly, so increased stress intensity factor drives the fatigue crack growth. The higher fatigue limit of series B which has bainite is caused by the ${\gamma}$ layer contained in microstructure impede the rapid growth of micro fatigue crack to mesocrack and ${\alpha}$ layer around graphite has the higher capacity for the absorption of plastic deformation energy than sorbite.
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페라이트-마르텐사이트 복합 조직강의 피로한도에 미치는 마르텐사이트 조직형태의 영향
김민건(Kim Min Gun),지정근(Ji Jueng Keun) 강원대학교 산업기술연구소 2000 産業技術硏究 Vol.20 No.1
A study has been made on the behavior of microscopic fatigue crack growth at the stress level of the fatigue limit with ferrite-martensitic structures. For the above purpose, two types of the microstructures were prepared ; one is the microstructure having the ferrite encapsulating the islands of second phase martensite(FEM), the other is the microstructure with the martensite encapsulating the islands of ferrite(MEF). It has been pointed out that the fatigue limits of these microstructures are related to the critical stress at which the microcrack in the MEF microstructure in which the critical crack length would be restricted within the second phase spacing in contrast with the FEM microstruture. However, the fatigue tests shows that no appreciable difference of the fatigue limits among them were recognized. Also, it turned out from the metallographic observations that the micro crack path is very much affected by the microstructures, so that the microcracks grow according to the 3-dimentional situation of its microstructures.
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CRACK 開口變位에 기초한 微小疲勞크랙 전파法則의 考察
김민건,지정근 江原大學校 産業技術硏究所 1993 産業技術硏究 Vol.13 No.-
Bending fatigue tests were carried out on the specimenes with tow different strength levels in order to investigate small crack growth rate. The main results obtained are as follows : (1) Small crack growth law, da/dn = Cσ?a is useful several materials, but is not the rule applicable to all cases generally. (2) When da/dn in several specimens are equal. COD near the crack tip are also nerarly equal. (3) Crack tip opening displacement (CTOD) is the main factor to control the small crack growth rate, and da/dn ? CTOD comes into being between the two. Accordingly, da/dn = c(σ?/σ)?a? shows the small crack growth rate being reflected crack closure phenomenon.
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페라이트-마르텐사이트 복합 조직강의 피로한도에 미치는 마르텐사이트 조직형태의 영향
김민건,지정근 강원대학교 산업기술연구소 2000 産業技術硏究 Vol.20 No.B
A study has been made on the behavior of microscopic fatigue crack growth at the stress level of the fatigue limit with ferrite-martensitic structures. For the above purpose, two types of the microstructures were prepared ; one is the microstructure having the ferrite encapsulating the islands of second phase martensite(FEM), the other is the microstructure with the martensite encapsulating the islands of ferrite(MEF). It has been pointed out that the fatigue limits of these microstructures are related to the critical stress at which the microcrack in the MEF microstructure in which the critical crack length would be restricted within the second phase spacing in contrast with the FEM microstruture. However, the fatigue tests shows that no appreciable difference of the fatigue limits among them were recognized. Also, it turned out from the metallographic observations that the micro crack path is very much affected by the microstructures, so that the microcracks grow according to the 3-dimentional situation of its microstructures.
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