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산성안개 하의 구조용강에서 피로균열의 발생 및 정류특성
김민건,김진학,김명섭,지정근,구은회,Kim, Min-Geon,Kim, Jin-Hak,Kim, Myeong-Seop,Ji, Jeong-Geun,Gu, Eun-Hoe 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.2
Corrosion fatigue tests were carried out to clarify the influence of acid fog as environmental factor on the fatigue strength of SM55C using rotary bending fatigue tester. The fatigue strength of acid fog specimen extremely decreased about 80% compared to that of distilled water specimen. In acid fog environment, a number of cracks commenced at corrosion pit and coalesced with the adjacent cracks during they propagate, and they formed a single non-propagating circumferential crack under the endurance stress of N=5$\times$10$\^$7/ cycles. Also, the depth of the crack is smaller than that of normal fatigue crack, so the crack has a veil small aspect ratio. The reason of this peculiar crack growth characteristics is that the crack opening-closure behaviors are hindered by corrosion products on the surface crack faces, and hence it is thinkable that the strong corrosion action like anodic dissolution for crack growth in depth direction is weaker compared with surface, resulting from faint pumping action of crack during loading-shedding processes.
극저사이클 하중을 받는 구상흑연주철의 초기균열성장에 관한 연구
김민건,임복규,김동열 江原大學校 産業技術硏究所 2002 産業技術硏究 Vol.22 No.A
In this study, extremely low cycle fatigue tests were carried out under push-pull loading conditions using graphite cast iron (GCD). In order to clarify the fatigue fracture mechanism of GCD in an extremely low cycle fatigue regime successive observations of internal fatigue damage were performed. The results obtained are as follows. (1) The process of extremely low cycle fatigue can be classified into three stages which are composed of the generation, growth and coalescence of microvoids inside materials. (2) In an extremely low cycle fatigue regime, microvoids originate from debonding of graphite-matrix interface.
오스템퍼링처리한 구상흑연주철의 오스테나이트화 조건에 따른 기계적 성질 및 피로한도에 관한 연구
김민건,임복규 江原大學校 産業技術硏究所 2004 産業技術硏究 Vol.24 No.A
This study was performed to investigate the effect of two step austenitized treatment on the mechanical properties and fracture characteristic of the ductile cast iron and austempered ductile cast iron(ADI). The obtained results of this study were as follows. The matrix structures of specimens were changed differently by austenitizing heat treatment Microstructure of austempered ductile cast iron obtained by two step austenitized treatment was bainitic ferrite and retained austenite. With two step austenitized treatment, vield strength, tensile strength and hardness decreased, while the elongation increased.
마하피닝 처리에 의한 기계구조용 합금강의 피로균열전파 지연효과
김민건,임복규,박홍기,황중각 강원대학교 산업기술연구소 2006 産業技術硏究 Vol.26 No.A
Mach peening treatment is one of the various kinds of techniques to improve the fatigue properties. The mach peening process gives high-level work hardening and compressive residual stress near the surface layer, improving the fatigue strength. In addition, this treatment reduces slip bands that initiate the fatigue cracks near the surface. During impingement, a plastic indentation surrounded by a plastic zone is formed. Mach peening treatment characteristic is less energy consumption and is an environmental friendly processing methods that is not accompanied by pollution. It is machining process that can prevent fatigue fracture beforehand in structure using already as well as process of production. The test results showed that fatigue crack propagation delay appeared by drilling type 43%, mach peening type 110%.
황련해독탕가감방(黃連解毒湯加減方)으로 치료한 지루성 피부염 치험 3례
김민건,황문제,Kim, Min-Gun,Hwang, Moon-Je 대한한방안이비인후피부과학회 2014 한방안이비인후피부과학회지 Vol.27 No.1
Objectives : The purpose of this study is to report the effect of Hwangryuhaedok-tang gagambang on seborrheic dermatitis. Methods : The clinical study was done on 3 cases of seborrheic dermatitis patients with symptoms of flare, scales, pricking and itching. An author prescribed Hwangryuhaedok-tang gagambang for these patients and checked VAS(Visual Analogue Scale) scores depending on the patient's evaluation. Photographies were taken before and after the treatment. Results : VAS scores of all patients decreased from 10 to 1,2. Judging by photographies, patients noticeably improved in facial skin. As a result of examining VAS scores and photographies, Hwangryuhaedok-tang gagambang was effective on seborrheic dermatitis. Conclusions : From these results, Hwangryuhaedok-tang gagambang may be considered as a basic prescription for seborrheic dermatitis. And an author consider that continuous clinical study will be needed in Korean medical dermatology.