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RISS 인기검색어
- 검색키워드
- 저자 : Jae Kyoo Lim (검색결과 143 건)
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Pre-strain狀態에서의 熔接後熱處理가 構造用鋼熔接熱影響部의 破壞靭性에 미치는 影響
林載奎,鄭世喜 全北大學校 1982 論文集 Vol.24 No.-
In order to study the change of fracture toughness owing to post weld heat treatment of welded specimens under the elastic bending deformation, after post weld heat treating of four different conditions, that holding time is 0, 1/4hr, 1hr and 10hr, on the welding joint of the high strength steel with bead on plate, tested the low temperature fracture toughness, observed the microstructure and measurred the microhardness. We obtained the results as follows. 1. Fracture toughness depends upon the heat treatment conditions. 2. Fracture toughness of the specimen under the pre-strain remarkablly increased until the holding time of the heat treatment is one hour, but it was almost saturated over the one hour. 3. Tempering the welding HAZ with the maximum (H_v=250), it became soft to H_v=170, but tempering under the elastic straining (ε=0.024), increased the hardness to the H_v=210. 4. Tempering at the condition of the elastic strain on the HAZ structure, fracture toughness greatly depends upon the hot working deformation.
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林載奎,鄭世喜 全北大學校 1985 論文集 Vol.27 No.-
Post weld heat treatment(PWHT) of weldment of the low alloy steel, in general, is carried out not only to remove residual stress and hydrogen existing in weldment but to improve fracture toughness of weld HAZ. There occur some problems when PWHT is practiced. They are toughness drecrement and stress relief cracking(SRC), which especially exist in the coarse-grained region of weld HAZ taken the effect of tempering treatment because PWHT is conducted at high temperature more than 600℃. Therefore, in this study, the effect of heating rate during PWHT on fracture toughness under the various kinds of stresses simulated residual stress in weld HAZ of Cr-Mo steel were evaluated by crack opening displacement(COD) test and microhardness test. The experimental results are as follows; 1. Fracture toughness of weld HAZ was improved by PWHT, but it decreased as heat treated under the stress. 2. Fracture toughness of weld HAZ was dependant upon heating rate during PWHT. In case of no stress, it was decreased with increment of heating rate, but it was improved with increment of heating rate in case of stress. 3. The difference of transition temperature, (ΔT_tr)_(σ=0), was linearly changed to hardness ratio, Hv/(Hv)_(σ=0), due to the varity of heating rate. And fracture toughness was increased with decrement of hardness ratio at the heating rate of 600℃/hr and 220℃/hr, but it was the reverse at 60℃/hr.
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李揆成,權相善,金大倫,朴哉林,林鍾吉,朴英淑 新羅大學校 1982 論文集 Vol.12 No.-
The present study aims to develop of evaluation method for college education. This study consiste of two parts: to identify the corelation between the freshmen's scores of pre-test for entrance examination and their scores of freshmen's year, and to make suggestions for the improvement of evaluation method in college on the basis of the former study results. Seen from the above mentioned aspects of this study, this study has meanings in its seek for a rational curriculum improvement and in its research of the pilot curriculum which presupposes the alleged system of limited graduation quota. This research which is conducted by above mentioned purpose andmeanings can be summerized as follows; 1) The freshmen's mean score of the-pre-test of college entrance examination is 192. 38. Among the departments of natural scienc attained the most higher score(204.22). and department of arts and gymnastics 162. 02 which is below average score. 2) In the achivements of the freshmn'e year the departments of natural sciences obtained the best results, followed by the departments of arts and gymnastics, education, and cultural aciences in oder. 3) There is no corelation between the pre-test scores of college entrance examination and the college achivement results. 4) The mean scores of the major and teaching subjects geneally increas as they go up into the advanced school years. 5) Each department has their own method of evaluation. 6) Teaching syllabus is asked to be presented whit the direction of clas, contents, purpose, and specific items of evaluation. 7) Achivements of college work must be evaluated by the normal distribution curve with the facts about specific factors of the study and students group taken into consideration.
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鄭世喜,林載奎,金貴子 全北大學校 1986 論文集 Vol.28 No.-
The fracture toughness of elasto-plastic materials was directly affected by the size, shape of plastic zone which are great important parameter in large scale fracture mechanics. This paper is to observe the influences of the interference of notches on plastic deformation at notch tip of double notch. Specimens were tested by four point bending, and then the shape of the plastic deformation could be visualized with the technique of recrystallization. Beside, numerical method for the analysis of the plastic zone with a F.E.M. (Finite Element Method) were used. The obtained results are summarized as follows: 1) The behavior of plastic zone on double notch was different from single notch. 2) When the plastic zone was saturated at a limitation on the middle between the notches, the behavior of the plastic deformation of double notched specimen was similar to that of the single notch. 3) Maximum equivalent plastic strain was shown at the tips of both single and double notch. 4) The evaluated model of plastic zone by F.E.M. corresponded to the results of the experiment.
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高溫에서 疲損勞傷이 Stainless Steel의 破壞靭性에 미치는 影響에 關한 硏究
鄭世喜,林載奎,李宗基 전북대학교 1982 論文集 Vol.24 No.-
The latest industrial machinery is usually used under the severe conditions such as high temperature, high pressure and high load because it needs the best efficiency. The austenitic stainless steels(SUS 316) are well suited for high temperature and high pressure service because of their creep resistance and high ductility. In this paper, in order to investigate the variation of fracture toughness of the specimens given repeat stress at 450℃, decreasing temperture of ductility, instrumented charpy impact test was carried out from-150℃ to 100℃. The results are summerized as follows ; 1. The fatigue life at 450℃ is reduced by 70 percent than that at room temperature. 2. When the specimens are damaged by the fatigue at 35kg/㎟ and at cyclic numbers with the same ratio on N_f, the difference between 450℃ and room temperature in hardness increasing ratio is 7%, and 5% at 30kg/㎟ 3. The maximum distance of work hardened zone by the fatigue damage at room temperature is larger than at 450℃. It means that the plastic deformation occurs easily because the yielding stress is lower at room temperature than at 450℃. 4. The fracture energy(E_f) decreases with the increase of nominal stress and rate of damage.
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鄭世喜,金台永,林載奎,鄭熙敦,朴昌彦 全北大學校 1984 論文集 Vol.26 No.-
The susceptibility of weld metal(AWS, F76-EH14) on hot straining embrittlement has been examined. The sharp notch was machined on the weld metal of 1st bead and on coarse-grained HAZ transformed by next pass. After machining the notch, these specimens were bended at 250℃ to receive the hot straining embrittlement and they were done COD fracture toughness test by the three point bending, and then the change of plastic zone at notch tip was evaluated by microhardness test. The obtained results are summarized as follows. 1. Fracture toughness of weld metal was greater than that of base metal. 2. Fracture toughness of the coarse-grained HAZ was similar to that of weld metal. 3. Hardness of weld metal reheated by next pass was lower than that of weld metal owing to the effect of heat treatment. 4. Plastic deformation of the coarse-grained HAZ was less than that of weld metal.
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전해산성수를 이용한 새로운 내시경 소독 시스템(Cleantop WM-1??)의 소독효율
이준행,이풍렬,송재훈,이남용,임윤정,장재권,김영호,김재준,백승운,이종철,최규완 대한감염학회 2001 감염 Vol.33 No.2
Background : Electrolyzed acid water (EAW) is a new liquid chemical germicide containing a mixture of oxidizing species and prepared by mixing a small amount of salt with tap water in an electrolyzer. We attempted an in-use evaluation of the high-level disinfection capability of Cleantop WM-1□, a new endoscope reprocessing system using EAW. Methods : Forty-seven flexible endoscopes were randomly collected just after upper endoscopic examinations and were disinfected using Cleantop WM-1□. Parts of the endoscopes without contact to EAW were disinfected with 75% ethyl alcohol. Immediately after the disinfection procedure, samples were taken from the biopsy channel (S-1), tip of the insertion tube (S-2), the umbilical cord (S-3), and the angulation knob (S-4). Results : In EAW-disinfected parts of the endoscopes, the culture-positive rates were 4.3% (2/47) in S-1 samples and 12.8% (6/47) in S-2 samples. In ethyl alcohol-disinfected area, the culture-positive rates were 2.1% (1/47) in S-3 samples and 25.5% (12/47) in S-4 samples. The colony counts of culture-positive samples ranged from 1 to 144. Pseudomonas aerugi-nasa was recovered from the angulation knob of an endoscope, but other contaminating organisms were mostly : normal flora or opportunistic pathogens. Conclusion : Although part of the endoscopes disinfected with 75% ethyl alcohol were contaminated with more organisms than EAW-disinfected areas, Cleantop WM-1□ showed a relatively good disinfection efficacy in reprocessing patient-used endoscopes. (Korean J Infect Dis 33:133∼138, 2001)
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