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4행정 가솔린 기관의 배기계 맥동압력 전달특성에 대한 주파수 해석
이준서(J.S.Lee),정광국(K.K.Chung),박종남(J.N.Park),유병구(B.K.Yoo),박세만(S.M.Bahk),차경옥(K.D.Cha) 한국자동차공학회 1994 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Pulsating pressure of exhaust system is generated by pulsating gas flow due to working of exhaust valve. The pulsating gas flow is closely<br/> concerned to engine power loss according to back pressure and exhaust noise. However, because of nonlinear effect due to large amplitude of pulsating pressure. it is difficult to exactly calculate pulsating pressure propagation in exhaust system of typical engine, Moreover, in case of estimating exhaust system performance, conventional prediction method which is based on linear theory, gives many restrictions and overestimate.<br/> As the first step for solving this problem, this paper contains experimental model to measure pulsating pressure propagation and shows power spectrum density, frequency response function, coherence in frequency domain for characterize pulsating pressure propagation in exhaust system of typical engine.<br/>
공진법에 의한 Carbon-Epoxy 복합재료의 탄성계수 평가
김형삼(H.S.Kim),박세만(S.M.Bahk),박명균(M.K.Park),이재혁(C.H.Yi),최홍섭(H.S.Choi) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_2
Carbon/epoxy is a well known composite material for its outstanding performance in structural applications. A method of experimentation is conceived and an experimental set-up is constructed to evaluate elastic constants of carbon/epoxy composites. The frequencies are measured for three different modes: torsional, flexural and longitudinal vibrations.<br/> There has existed a formula expressing an explicit relationship between resonance frequencies and elastic constants. However the formula is valid only for a isotropic media. Area moments of inertia for composite materials are computed from measured frequencies of both longitudinal and flexural vibrations. The computed moments of inertia are utilized to determine elastic constants of carbon/epoxy composites. Which are then compared with elastic constants obtained from the formula developed for isotropic materials. Also. Variations of elastic constants at different temperatures are investigated with applications of the modified formula that has corrected values of area moment of inertia.<br/>
계장화 샤피충격시험기를 이용한 재료의 동적파괴특성에 관한 연구
김길수(K. S. KIM),김기동(K. D. KIM),박세만(S. M. BAHK),박명균(M. K. PARK) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.6_1
This investigation determines dynamic fracture characteristics of metals such as SM45C, SM20C and SS41. One of the dynamic' characteristics, dynamic fracture toughness, was evaluated by conducting instrumented charpy impact tests. Specially, in this study, signals obtained from the strain gage implanted in the impact tup is transformed to Load-Time data by digital signal processing. To obtain appropriate dynamic fracture toughness, the Load-Time data is critically reviewed and tested based on three criteria; inertia effect, limited frequency response and energy levels. This procedure ensures the reliability of the data. The data is, then, examined in view of topological aspects of fractured surfaces of the metals to reveal dynamic natures of materials failure.<br/> <br/>
백범선(B.S.BAEK),주재황(J.H.JOO),박명균(M.K.PARK),박세만(S.M.BAHK) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.6_2
A conventional photoelasticity method has some difficulties to get the accurate results due to a collapsed image of the fringe when performing stress analysis around a crack tip or concentrated loading point. A method of digital image processing technique, which can multiply and sharpen the isochromatic fringe in photoelasticity is applied to obtain a better photoelastic fringe pattern of a v-notch plate under tension.<br/>
김길수(K. S. KIM),박세만(S. M. BAHK),박명균(M. K. PARK) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.11_1
This investigation determines dynamic crack initiation roughnesses(K_id, J_id) of metallic materials such as SM20C and STD 11. Dynamic fracture toughnesses were was evaluated by conducting instrumented charpy impact tests. Specially, in this study, signals obtained from the strain gage implanted in the impact tup is transformed to Load-Time data by digital signal processings. To obtain appropriate data, the data were critically reviewed and tested against three criteria; inertia effects, limited frequency responses and energy levels. Initiation energy was determined using the method of compliance changing rate and was corrected to take into account of energy which was absorbed by inertia force.<br/>
4 행정 가솔린 기관의 배기계 맥동 압력 감쇄 특성에 관한 실험적 연구.
이준서(J.S.Lee),조수강(S.K.Cho),박세만(S.M.Park),차경옥(K.O.Cha) 한국자동차공학회 1993 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Pulsating pressure of engine exhaust system is generated by pulsating gas flow due to working of exhaust valve. This exhaust gas pulsating flow is closely concerned to engine power loss according to back pressure and engine exhaust noise. Moreover, in case of estimating the muffler, conventional prediction method, which is based on linear acousstic theory, gives many restrictions and an overestimate. These fact suggest that the nonlinear effect due to large amplitude of pulsating pressure. In this paper. it shows difficulty in theoritical prediction in typical engine. As the first step for solving this problem we measured pulsating histories. Measured pressure histories in exhaust system are analyzed by spectral formula. And using the frequency response function. experimental model of performance test is proposed by pulsating pressure attenuation characteristics due to exhaust system.<br/>