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국산 선급 A-1 강판의 수중용접 입열량이 기계적 특성에 미치는 영향에 관한 연구
오세규(Sae Kyoo Oh),이종석(Jong Seok Lee),한상덕(Sang Deok Han) 한국해양공학회 1987 韓國海洋工學會誌 Vol.1 No.1
In this paper, the optimizing investigation of characteristics of underwater welding by a gravity type arc welding process is experimentally carried out by using the ø 4 ㎜ ilmenite type of domestic coated welding electrodes for welding the domestic marine structural steel plates of 8 mm thickness in order to develop the underwater welding techniques in practical use, resulting in the quantitative analysis possibility for the relationship between the mechanical properties of underwater welded joint HAZ and the welding heat input.
오세규(Sae-Kyoo Oh),이종두(Jong-Doo Lee) 한국해양공학회 1990 韓國海洋工學會誌 Vol.4 No.1
The friction welding has more techanical and economic advantages than the other welding processes. As this welding process has the characteristics such as curtailment of production time, materials, cost reduction, etc., it has been widely used in production of various mechanical components which have complex shapes.<br/> So, this paper deals with optimizing the friction welding conditions and analyzing various mechanical properties of the friction welded joints of torsion bar material SUP9A bar to bar.<br/> The results obtained are summarized as follows ;<br/> 1) The quantitative relation between heating time(t₁, sec) and total upset(U, ㎜) can be obtained. The empirical formula obtained is ; U=3.29 t₁+1.6<br/> 2) The tensile strength(σt, ㎏f/㎟) of friction welding joints as post weld heat treated (PWHT) depends upon heating time(t₁, sec) quantitatively and the empirical formula obtained is ; σ=-5.1 t<SUP>2</SUP>1+44.90 t₁+45.2<br/> 3) It is certain that the optimum condition for friction welded joints of SUP9A steel bars of diameter 14.5㎜ is, considering on various properties such as tensile strength, torsional strength, impact energy and strain of the joints after PWTH ; n=2000rpm, P₁=8㎏f/㎟, P₂=20㎏f/㎟, t₁=4sec, t₂=3sec<br/> 4) The tensile strength, torsional strength and hardness were increased with the increasing carbon equivalent, but toughness was decreased.
吳世奎(Sae-Kyoo Oh),李鍾斗(Jong-Doo Lee) 한국해양공학회 1990 韓國海洋工學會誌 Vol.4 No.2
This paper deals with investigating experimentally the effects of PWHT on the weld quality such as strength, toughness, hardness and micro-structure of the welded joints in friction welding of torsion bar material SUP9A bar to bar.<br/> The results obtained are summarized as follows ;<br/> 1) It was certified that the condition of the post-weld heat treatment(PWHT) for the friction welded joints was very satisfactory because both strength and toughness of the joints were improved as almost same as those of the base metal or better by the PWHT.<br/> 2) The peak of hardness distribution of the friction welded joints can be eliminated by PWHT, resulting in being almost equalized at the weld interface, the HAZ(heat affected zone) and the base metal.<br/> 3) The micro-structure of the base metal, HAZ and weld interface(WI) of friction welded joints welded at the optimum welding condition consists of the same sorbite structure obtained by PWHT and fined sorbite at WI, resulting in increasing toughness as well as strength, and no micro structural defect has been found at the friction welded zone.
오세규(Sae-Kyoo Oh),김연호(Yeon-Ho Kim),이상국(Sang-Guk Lee),이종두(Jong-Doo Lee) 한국해양공학회 1989 韓國海洋工學會誌 Vol.3 No.2
It has been very important in various industry fields to improve the fatigue strength characteristics of bearings such as bearing life, fatigue limit, etc., because such poor properties could result in shortening the machinery life as well as in decreasing the accuracy. However, no successful heat treatment criterion seems to be available at present.<br/> In this study, the effect of the 170℃×120min tempering cycles repeated after 830℃×30min oil quenching for 800℃ spheroidizing-annealed bearing steel (STB2) as base metal on the 120℃ high temperature rotary bending fatigue strength characteristics were investigated, including the effects on hardness, Charpy impact value and micro-structure, in order to seek for the best heat treatment condition finally. The important results obtained are as follows :<br/> 1) The optimal cycle of tempering so that the fatigue strength σ could become the highest was the 4th cycle. And it is confirmed that this σF is about 6 times more increased than that of base metal, and about 1.3 times more increased than the case of the 1 cycle tempered.<br/> 2) As a result of the investigation for the effects of tempering cycles on hardness, the hardness at the tempering number of 2 thru 5 cycles was not decreased severely ; only about 10% decrease from those of the quenched and 1 cycle tempered case. Such hardness is equivalent to HRC61~62 with no bad effect on anti-abrasion of bearing steel.<br/> 3) In the case of 2 thru 5 cycle tempering as well as 1 cycle tempering, the impact value was not so improved comparing with the case of quenching, but an increase of 5 to 10% could be expected at least.<br/> 4) It was experimentally confirmed that the control of the mechanical properties improvement such as fatigue strength and fatigue life for bearing steels could be possible by the number of tempering cycles.
유공압 밸브 스풀용 강재의 봉대봉 이종재 마찰용접 최적화와 용접강도 특성 및 AE 평가
오세규(Sae-Kyoo Oh),유인종(In-Jong Yoo),오정환(Jung-Hwan Oh),박형동(Hyung-Dong Park),이연탁(Yeon-Tack Lee) 한국해양공학회 1996 韓國海洋工學會誌 Vol.10 No.3
Up to now, most of studies on mechanical properties in friction welded components are about tensile and bending strength. However the fatigue studies on the friction-welded components subjected to repeated stress are not available. The purposes of this study are the development of fundamental design and manufacturing technique of hydraulic valve spool by optimizing of friction welding, and the development of in-process real-time weld quality evaluation technique by acoustic emission for the bar-to-bar dissimilar friction welding of hydraulic valve spool steels.
미세조류 생물반응기 시스템의 민감도분석을 위한 최적입력설계 및 모델예측제어
이종민 ( Jong Min Lee ),유성진 ( Sung Jin Yoo ),오세규 ( Se Kyu Oh ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.1
Microalgae have been suggested as a promising feedstock for producing biofuel because of their potential of lipid production. In this study, a first principles ODE model for microalgae growth and neutral lipid synthesis proposed by Surisetty et al. (2010) is investigated for the purpose of maximizing the rate of microalgae growth and the amount of neutral lipid. The model has 6 states and 12 parameters and follows the assumption of Droop model which explains the growth as a two-step phenomenon; the uptake of nutrients is first occurred in the cell, and then use of intracellular nutrient to support cells growth. In this study, optimal input design using D-optimality criterion is performed to compute the system input profile and sensitivity analysis is also performed to determine which parameters have a negligible effect on the model predictions. Furthermore, model predictive control based on successive linearization is implemented to maximize the amount of neutral lipid contents.