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계장화 샬피 충격시험에 의한 노치형상에 따른 동적파괴인성치의 평가
우창기(C. K. Woo),박홍기(H. K. Park),이장규(J. G. Lee),강동명(D. M. Kang),이하성(H. S. Lee) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.6_1
Dynamic fracture toughness is evaluated in terms of notch shape, notch depth and impact velocity of instrumented Charpy test. Specimen used is SM4SC. The results obtained are as follows: (1) Dynamic calibration of instrumented tup is important in addition to static calibration for the reliance of instrumented Charpy test. (2) Magnitude of inertia force in instrumented Charpy test has no relation with notch shape or notch depth. However, It increases as the impact velocity increases. (3) For the U-notch of notch depth 2mm and 3mm, the fomula obtained by crack initiation load should be used to determine the dynamic fracture toughness. (4) For the V-notch of any notch depth, either the formula obtained by crack initiation load or that by impact energy may be used to determine the dynamic fracture toughness. However, for the notch depth 2mm and 3mm, the formula by crack initiation load should be used.
충돌수분류(衝突水噴流)에 의한 원통내면(圓筒內面)에서의 열전달증진(熱傳達增進)에 관한 연구(硏究)
엄기찬,우창기,최국광,서정윤,Ohm, K.C.,Woo, C.K.,Choi, G.G.,Seo, J.Y. 대한설비공학회 1990 설비공학 논문집 Vol.2 No.4
An experimental study of the heat transfer characteristics between circular water jet and cylindrical inner surface is presented. The ratios of the semi-cylinder's inner diameter and the nozzle outlet diameter were varied parametrically, as were the Reynolds number and the supplementary water heights. The measurements showed that cirucmferential distribution of the heat transfer coefficient peaked at the stagnation point and, there occurred a kind of a secondary maximum of heat transfer that moved toward to stagnation point as the ratio d/D increased. The local heat transfer coefficient increases as the Reynolds number becomes larger, and the rate of increase is subjected to the influence of d/D & position of angle. Also, optimum heights of supplementary water which brings about the augmentation of heat transfer are S/D=1 for the stagnation point, the position of $15^{\circ}$ & $30^{\circ}$ angle, but for the positions of $45^{\circ}$ angle (d/D=10~11.67), $60^{\circ}$ & $75^{\circ}$ angle, the heat transfer coefficients in the case of using supplementary water are smaller than simple jet (S/D=0).
[구조강도부문] 자동차 현가 부품 개발 과정에서의 와이베이즈 분석을 이용한 내구신뢰성 평가
김범룡(B.R. Kim),우창기(C.G. Woo) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_2
This paper discusses the practical process of design verification for durability and reliability by laboratory test in vehicle suspension development. Weibayes analysis assumes that the weibull slope is knO\\11 or can be approximated in advance of the data analysis which is used for assessing highly reliable suspension components for reliability goal in initial development phase of vehicle suspension. This technique can be adapted to determine the sample size, reliability, confidence level and test time of fatigue test as qualification test to demonstrate compliance to requirement in production phase.
다구찌 방법을 이용한 박육 성형제품 열 특성에 관한 연구
김옥래(O. R. Kim),박균명(G. M. Park),고현준(H. J. Ko),이상용(S. Y. Lee),우창기(C. K. Woo) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
A Thin wall injection molding is generally defined as a product having a thickness lesser than 1 ㎜ or having a ratio between flow length and wall thickness more than 100:1. The typical applications are laser disks like CD and DVD, connectors for electric devices, IC card and so forth. Besides, for manufacturing mobile information equipments like laptop computers and cell phone cases, thin wall has been studied considering molding formability and strength in many aspects.
유효 K_Id 산정을 위한 샬피 충격시험편의 노치형상에 관한 연구
강동명(D.M.Kang),이하성(H.S.Lee),우상훈(S.H.Woo),조진호(J.H.Jo),우창기(C.G.Woo) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.5_1
This investigation evaluates effects of notch depth, fatigue precrack length and side groove in impact specimen for estimation of a valid K_id by instrumented charpy impact test. Specimen used is 6005-T6. For notch depth 2.0mm and 2.5mm specimens or within about 2 mm fatigue precrack length with notch depth 2.0mm specimens, the formula of dynamic fracture toughness obtained by crack initiation load(Pm) should be used to determined K_id. Dynamic fracture toughness of side grooved specimens are overestmated to that of standard impact specimen about 15^ ~ 20%. It is confirmed that the formula of dynamic fracture toughness obtained by impact absorbed energy is inappropriate for ductile materials.<br/>