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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.
우창기(C.K.Woo),이장규(Z.K.Rhee) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.11_1
In this paper, stress aging effects of aging stress. aging temperature and aging time on the rotary bending fatigue fracture behavior for the SM45C were investigated. The stress aging treatment is a well known technology for the increment of elastic strength and yield strength without losing toughness in alloys by applying the external load under the conditions with the optimum values of stress. temperature and time. The optimal stress aging treatment conditions in these experiments are the stress of 3.38 MPa. the temperature of 300℃ and the time of 5 hours. The results show that the fatigue limit increased about 30.0% under rotary bending fatigue test.<br/>
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).
Dual-PDA를 이용한 절삭유 에어로졸 특성분석에 관한 연구(II) - 선삭공정의 절삭유 에어로졸 예측
정의식,황덕철,우창기,황준,Chung, E.S.,Hwang, D.C.,Woo, C.K.,Hwang, J. 한국액체미립화학회 2005 한국액체미립화학회지 Vol.10 No.2
This paper presents the analytical approaches to predict cutting fluid aerosol formation characteristics in machining process. The prediction model which is based on the rotary atomization theory analyzes aerosol behaviors in terms of size and concentration. Experiments were tarried out to verify the aerosol formation prediction model under various operational conditions. The experimental results which are obtained by Dual-PDA measurement show resonable agreement with prediction results of aerosol concentration. This study can be provided as a basis to estimate and control the hazardous cutting fluid aerosol in machining process in view of environmental consciousness.
이중사출의 접합성 개선 및 생산성향상을 위한 금형구조 개발기술연구
김옥래,이상용,김영근,우창기,한일용,Kim, O.R.,Lee, S.Y.,Kim, Y.K.,Woo, C.K.,Han, I.Y. 한국금형공학회 2008 한국금형공학회지 Vol.2 No.6
Double-injection molding can inject two different materials or two colors in the same mold and process. If this injection process use, product has ability because the base part maintain strength and specified part can inject soft-material. It makes the cost down by single operation automatically for saving wages. In this paper, we designed double-injection mold for automobile remote control to inject secondary using this part as insert after inject external appearance of product. CAE analysis was progressed gate location and runner size as variable and analysis result is reflected in mold design process. As a result, it could solved badness that is generated at the conventional mold. Additionally, cost is downed by reducing loss of runner as well as could omit painting process because surface of finished product is improved through new mold.
김옥래(O. R. kim),우창기(C. K. Woo) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
In this paper, using by rapid heating and cooling systems for injection molding and temperatures to changes. In the process of molding temperature and pressure inside the mold was found. In addition, the tensile strength of test specimens were molded. And The mechanical properties of injection molded parts were identified on mold temperature. Copper could withstand more tensile force than NAK. Therefore, it can be concluded that materials with high heat conductivity must be used in thin walled products.