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유헌일(Heonil Yoo),천기정(T. Kawasaki),택목양삼(Y. Sawaki) 한국자동차공학회 1983 오토저널 Vol.5 No.1
In case of K_lmax < K_lscc, the corrosion fatigue of high strength steel in O.1N H₂SO₄ solution and 3.5% salt water is as follows.<br/> 1. The fatigue life shortens in order of 3.5% salt water and O.1N H₂SO₄ solution.<br/> 2. The fatigue crack growth rate in air is obtained as the following equation.<br/> (dc/dN)_?=7.23×10^-?(△K)^?<br/> 3. The corrosion fatigue crack growth rate in environment is divided into three regions, that is, First Region, Second Region and Third Region from the small cyclic stress intensity.<br/> 4. The formation rate of the active surface on metal is slower than the mechano-chemical reaction rate in First Region. The crack growth rate depends on time and the cyclic stress intensity and is expressed as the following equation.<br/> (dc/dN)=C(△K)^δ<br/> 5. The formation rate of the active surface is faster than the mechano-chemical reaction rate in Second Region and the synergistic effect by stress and corrosion becomes slow. In case the. fatigure load is large, we have the critical crack growth rate which is not<br/> related to the cyclic stress intensity. .<br/> 6. The corrosion crack growth rate by the mechano-chemical reaction is the same in H₂S0₄ solution and salt water, so Hydrogen accelerates the crack growth.<br/> 7. The environment has no effect on the corrosion. fatigue crack growth rate in Third Region.<br/> 8. In First Region and Second Region, dimple is observed on the fatigue fracture surface in O.lN H₂SO₄ solution.<br/> 9. The striation is observed in any environment as in air in Third Region and its interval approximately coincide with the crack growth rate.
고장력강의 부식피로에 미치는 용액온도의 영향에 관한 연구
유헌일 한국자동차공학회 1986 오토저널 Vol.8 No.1
A study has been made of the corrosion fatigue of high strength low alloy steel in 3.5% NaCl solution under tension stress for solution temperature being 25.deg. C, 55.deg. C and 85 .deg. C. The main results obtained are as follows; 1) The corrosion fatigue crack growth rate curve could be divided into the First Region, the Second Region and the Third Region. 2) The corrosion fatigue crack growth rates in the First Region and the Second Region were Arrhenius temperature-dependent in this test range. The apparent activation energies for the corrosion fatigue cack growth rate were found to be 2000cal/mol in the First Region and 3700 cal/mol in the Second Region. 3) Hematite (Fe$_{2}$O$_{3}$) as the hexahedral crystal and magnetite (Fe$_{3}$O$_{4}$) as the octahedral crystal were observed in the corrosion products on the corrosion fatigue fracture surface at 85.deg. C and the anode fusion seem to be generated in the crack tip region at high temperature. 4) The complex environment effect ratio which was defined by the ratio of fatigue crack growth rate in corrosion environment to that in air might be considered not only a criterion estimating the effect of environment quantitatively but also an important parameter in the selection of the design stress for the fail safe design. The complex environment effect was not greater than ten in this test.
Surgical Outcomes of Hemorrhagic Metastatic Brain Tumors
유헌,정유진,곽호신,신상훈,이승훈 대한암학회 2011 Cancer Research and Treatment Vol.43 No.2
Purpose Hemorrhagic metastatic brain tumors are not rare, but little is known about the surgical outcome following treatment. We conducted this study to determine the result of the surgical outcome of hemorrhagic metastatic brain tumors. Materials and Methods From July 2001 to December 2008, 21 patients underwent surgery for hemorrhagic metastatic brain tumors at our institution. 15 patients had lung cancer, 3 had hepatocellular carcinoma,and the rest had rectal cancer, renal cell carcinoma, and sarcoma. 20 patients had macroscopic hemorrhage in the tumors, and one patient had intracerebral hemorrhage surrounding the tumor. A retrospective clinical review was conducted focusing on the patterns of presenting symptoms and signs, as well as local recurrence following surgery. Results Among 21 hemorrhagic brain metastases, local recurrence developed in two patients. The 12 month progression free survival rate was 86.1%. Mean time to progression was 20.8months and median survival time after surgery was 11.7 months. Conclusion The results of our study showed that hemorrhagic metastatic brain tumors rarely recurred after surgery. Surgery should be considered as a good treatment option for hemorrhagic brain metastasis, especially in cases with increased intracranial pressure or severe neurologic deficits.
유헌일,택목양삼 대한기계학회 1982 大韓機械學會誌 Vol.22 No.1
금속재료의 파괴에 대해 옛부터 많은 연구가 행해져 왔다. 그러나 실제의 구조부제에 따라서는 그 파괴가 순간적으로 생기는 경우가 많아서 그 파괴를 실험적으로 파악한다는 것은 어렵다. 그러나 최근 전자현미경의 진보로 파괴면을 관찰하는 일이 쉬워지고 파괴과정이나 그 미시기구가 더욱 충실히 밝혀지므로서 electronmicro-fractography 라 불리우는 학문체계가 형성되기에 이르 렀다. 따라서 본 해설에서는 금속재료의 파괴와 fractography에 대해 설명하고, 파괴역학의 기 초적개념에 관해서 해설하고, 최후로 하나의 응용으로 파괴사고의 사고예해석(case study)에 대한 개설을 하기로 한다.