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[論文] 고강도 알미늄 합금재에 있어서 크랙열림점 평가에 관한 연구(I)
최병기(B. K. Choi) 한국자동차공학회 1993 오토저널 Vol.15 No.1
This paper aims to synthesize the research on fatigue fracture mechanisms of high strength aluminum alloys which are widely used in motorcars or airplanes to prevent accidents.<br/> To measure the data of crack opening ratio, the same materials and methods are used for evaluating the fatigue crack propagation rate as an effective stress intensity factor. But, many researchers have brought different results.<br/> An exact crack opening ratio was, therefore, proposed for getting a more accurate fatigue crack propa gation rate.<br/> The main. conclusions obtained are as follows.<br/> (1) As a result of the fatigue test, the value of the crack opening ratio is the same regardless of the stress ratio.<br/> (2) The value of crack opening ratio is different according to the measuring point.<br/> After measuring the crack propagation rate by using an effective stress intensity factor, the crack opening ratio value measured at the crack mouth by a clip gage, or measured rear of the specimen by a strain gage is more accurate than that by any other measuring test.
C200 마르에이징강의 기계적성질에 미치는 Nb 첨가량 및 시효처리의 영향
장경천(K.C. Jang),최병희(B.H. Choi),최병기(B.K. Choi) 한국생산제조학회 2005 한국공작기계학회 추계학술대회논문집 Vol.2005 No.-
Objective of this study was effects of Nb(Niobium) contents and age hardening conditions on the strength of C200 maraging steel which are commonly using in aircraft, space field, nuclear energy, and vehicle etc. To investigate the effects, steel was manufactured by a VIM (Capacity: 30㎏f, Max Temp. : 1650℃, 10?³? Torr, 45 min/charge) added 0%, 0.03%, and 0.06% niobium with basic chemical compositions. And the steel was hot rolled automatically, solution annealed at 815℃ for I hour, and age hardened with 48%KNO₃+52NaNO₃ at 455℃, 482℃, and 510℃ for 1,2,4, and 8 hours each other. The most excellent condition for elongation was 0.03% Nb material aged at 455℃ for 1 hour having about 97% of base metal. The most excellent aging condition was 8 hours aged at 482℃ with 0.06% Nb content showing that the strength of the specimen increased twice more than that of the base metal.
원판형 이중 질량 플라이휠에 대한 피로 실험 및 유한요소 응력해석
남욱희(W. H. Nam),최병기(B. K. Choi),이춘열(C. Y. Lee) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
RDMF system increases the moment inertia or transmission by shifting some part of flywheel inertia to transmission, and reduces the stiffness of torsional spring by using wider space compare to conventional clutch system. As a result. RDMF systcm can redoce the resonance speed to below idle speed(about 700 RPM). This paper deals with the design concept and working(behavior) principle of RDMF system and the stress analysis for spring box. Finite element analysis and fatigue test were performed to evaluate stress level and critical area of the torsional spring box. By finite element analysis and fatigue test, it is proven that the most critical area of RDMF system structure is the welded zone of spring box. The maximum stress concentration occurs at the welded zone when the torque difference between engine and transmission is maximum. The stress concentration decreases with increasing engine rotational speed. Thus engine speed relieves stress concentration or the welded zone.
송준혁(S.J. Song),김하수(H.S. Kim),강희용(H.Y. Kang),양성모(S.M. Yang),홍동표(D.P. Hong),정태진(T.L. Chung),최병기(B.K. Choi) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.6_1
This study has two main pants, comqaring the characteristics between the conventional clutch system and DMF system, and the DMF system in vehicle and computer simulation of DMF. The characteristics of torsional vibrations between a conventiona1 clutch system after optimal clutch system tunning and DMF system at engine phase of stat up, idle, creeping drive and coast. To develope a new optimum system, a dynamic model of powertrain at idle phase is developed compared with actual vehicle at start up ant idle phase of engine. This model is well suited for actual system. First of all, a DMF system is superior to a conventional clutch system.