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SUS 304 강의 크리프 온도역에 있어서 피로균열성장거동에 관한 연구
주원식,오세욱,조석수 대한기계학회 1994 대한기계학회논문집 Vol.18 No.3
The high temperature fatigue crack growth behavior of SUS 304 stainless steel at $550^{\circ}C$ and $650^{\circ}C$ was investigated under various kinds of stress ratio and frequency in sinusoidal waveform on the basis of the non-linear fracture mechanics. The result arranging crack growth rate by modified J-integral J' showed influence of stress ratio and frequency. All the data obtained under the test at $550^{\circ}C$ were plotted within data band of da/dN-${\triangle}J_f$ relationship for cycle-dependent crack growth. On the basis of static creep and cycle-dependent data band; both time- and cycle-dependent crack growth behavior was observed under loading conditions at $650^{\circ}C$, but cycle-dependent crack growth behavior predominantly appeared and time-dependent crack growth behaviour was little observed under loading conditions at $550^{\circ}C$. Fractographic examinations for fracture surface indicated that the fracture mode was generally transgranular. The stripes were found on fracture surface and each stripe was accompanied by a crack tip blunting and an abrupt increase in the load-point displacement. The $J'_{an}$ had a validity in case of $650^{\circ}C, but scarcely had it in case of $550^{\circ}C$.
미국 RGA(Rice Growers Association) 협동조합의 실패사례가 주는 교훈
주원식 농업협동조합중앙회 2005 농협조사월보 Vol.574 No.-
RGA(Rice Grower's Association) 및 TVG (Tri Valley Growers) 등을 포함한 캘리포니아의 대형 협동조합들이 2000년을 전후로 파산하였으며, 다른 캘리포니아의 협동조합들도 재정적으로 많은 어려움을 겪고 있다. 이러한 양상은 캘리포니아의 협동조합들이 농업분야에서 갈수록 힘든 경쟁에 직면하고 있다는 것을 의미한다. 캘리포니아 농업의 규모와 국가적 중요성을 감안한다면 주(州)조합들의 역할 감소는 향후 대형조합들의 역할 감소를 예견하는 것일 수도 있으며, 이는 국지적 현상이 아니라 전국적 현상일 수도 있다. 미 농무부와 UC Davis의 ARE(Agricultural and Resurce Economics)는 RGA 협동조합 몰락의 숨겨진 원인을 공동으로 연구하고 있다. 이번 사례연구의 목적은 RGA 협동조합 파산의 근본문제를 규명하고 다른 협동조합들에게 유용한 교훈을 주는데 있다. 이전 RGA 협동조합의 관계자를 상대로 한 설문조사를 통해 다수의 조합원과 경영진들이 추정하는 RGA 협동조합 몰락의 주요 원인들을 정형화기 위해 이루어졌다. 거의 80년의 역사를 가진 RGA 협동조합은 2000년 8월에 파산하였다. RGA 협동조합은 1980년대 초반까지만 하더라도 전체 캘리포니아 쌀 생산량의 70% 이상을 취급하였지만 2000년 파산시점에는 전체 물량의 겨우 5%를 취급하는 조합으로 추락하였고, 이러한 극적인 몰락은 연구과제로서 매우 흥미롭다.
알루미늄 破覆鋼板의 疲榮强度와 프랙트그래피에 관한 硏究
周原植,吳世旭 동아대학교 공과대학 부설 한국자원개발연구소 1981 硏究報告 Vol.5 No.2
Aluminum coated steel has been used as a simple stress of material for machine parts. Because it is excellent in a high temperature, corrision resistance and wear resistance. It has been still widely applied to making highly efficient machine parts of an extremely high fidelity with the task of a complicated stress and repeated load. In these years of severe economical situation around the world, the shortage of natural resources has forced to replace the high priced materials-super allay steel-, to the low priced materials of an extremely high fidelity for machine parts, resulting to be successful in developing the above mentioned aluminum coated steel for this propose. Therefore, concentrated all efforts in this study on the investigation and observation of the application of V-notch specimens of structural steel plate treated with aluminum diffusion coated, to the fatigue strength and fatigue behavior effected from bending fatigue, tension fatigue, static tension fracture and fracture surface. The result of experimental study are as follows : 1) Notch specimens of structural steel plate treated with aluminum diffusion coated has 20% higher fatigue limit than raw materials. This result confirmed that aluminum coated steel could be applied in raising fatigue limit. 2) The elevation of fatigue limit comes from the generation of peeling crack in between the alloy layer and matrix. 3) The bending fatigue fracture surface of the low stress level has a little striation while the high stress level and tension has a conspicuous strition. 4) The bending fatigue fracture surface of the low stress level has a tire track.