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차량과 콘크리트 교각의 직접충돌해석법과 충돌하중이력곡선을 이용한 간접충돌해석법 비교연구
김우석,김경진,이재하,Kim, WooSeok,Kim, Kyeongjin,Lee, Jaeha 한국전산구조공학회 2014 한국전산구조공학회논문집 Vol.27 No.6
본 연구에서는 차량과 교각의 직접충돌해석을 통하여 기존 설계기준(도로교설계기준, AASHOTO LRFD)에서 아직 고려하고 있지 않은 동적영향을 고려한 실제 교각의 충돌 파괴 거동을 다양한 경계조건별로 검토하였다. 선정된 차량은 10톤, 16톤, 38톤의 Cargo 트럭이며 교각은 경부고속도로 상 일반적인 제원으로 선정하였다. 해석결과 가장 많은 파괴는 상부구조의 고려없이 교각의 상부면을 구속하였을 시에 발생하였으며 상부구조는 2차적인 영향을 교각에 전달하기 보다는 충돌에너지를 일부 흡수하는 역할을 하며 파괴를 감소시키는 것으로 확인되었다. 또한 해석의 효율성을 위해 차량과 강체간 충돌시 발생하는 충돌하중이력곡선을 교각에 외력으로 부여한 간접충돌해석을 수행하고, 이를 직접충돌해석 결과와 비교하였다. 해석 결과 직접충돌해석 결과와 매우 유사하게 교각의 거동을 예측하는 것으로 확인되었으며 해석효율성 또한 높아져 해석시간은 약 92%정도 감소하였다. 이러한 간접충돌해석법은 다양한 기존 모델이나 다른 해석프로그램에도 쉽게 부여될 수 있어 그 활용범위가 증가할 것으로 판단된다. In design standards such as AASHTO LRFD and Korea Highway Bridge Design, the dynamic behaviors under the impact loading has not been considered and it recommends of using a static force for designing bridge column against vehicle collisions. Accordingly, in this study, models of vehicle collisions to concrete bridge column were developed with various boundary conditions in order to take into account dynamic behaviour of the column. Cargo trucks of 10tons, 16tons and 38tons were selected and a typical type of concrete bridge pier column along the Kyungbu highway in Korea was selected for this study. Results from this study indicate that the static load specified in the design standards are too small compared to results obtained in this study. It was also found that a consideration of the bridge superstructure allowed smaller damages of concrete bridge pier column under truck impact loadings. Furthermore, a comparison study of direct impact analysis of vehicle to bridge-column with in-direct impact analysis using load-time history functions was performed. The in-direct impact analysis shows that the use of load-time history graph improves the computational cost up to 92% and predict the behaviors of the bridge column under the impact loadings well. The obtained load-time history graph could be easily applied to several existing models.
LPG 액상 분사 시 인젝터 주위의 Icing 현상에 관한 연구 (Ⅰ)
김우석(Wooseok Kim),박정철(Jungcheol Park),이종화(Jonghwa Lee),유재석(Jaisuk Yoo),박심수(Simsoo Park) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_3
Recently, LPli(Liquefied Petroleum liquid injection) system is studied for the new stringent emission regulations. Different from the mixer system for LPG, there are some problems to be solved such as injector tip icing and leakage for LPli system development.<br/> In this study, icing problem near injector tip, this leads to difficulty of accurate A/F control, was studied and reported. Icing of injector tip & port waII was observed at all the cases in this study regardless of injection duration and angle, air humidity change. The spray angle of LPli was observed approximately two times wider than that of Gasoline injection. This makes the LPli spray collide with intake port around injector tip. Temperature of the wetted area was decreascd and icing of water vapor contained in intake air because of evaporation of the fuel film. The ice of the injector tip and port wall is also affected by the materials related to heat transfer.
초음파 속도법을 활용한 강판의 두께 변화 탐지를 위한 기초연구
김우석 ( Wooseok Kim ),문성모 ( Seongmo Mun ),김철민 ( Chulmin Kim ),임석빈 ( Seokbeen Im ) 한국구조물진단유지관리공학회 2020 한국구조물진단유지관리공학회 논문집 Vol.24 No.6
본 연구는 강교량의 폐합부재 등 시각적으로 탐지하기 어려운 부위의 강재에 대한 손상을 탐지하기 위한 방법을 개발하기 위한 목적의 기초연구이다. 여러 비파괴 방법들 중에서 초음파 속도법을 활용하여 두께가 다른 시편에 대해서 초음파 속도법을 실시하여, 평균 매질내전파속도를 도출하였고, 이를 활용하여 강재 부재에 대한 회귀분석을 실시하였다. 동일한 재료일 경우 회귀분석의 결과를 활용하면 다른 부재의 두께를 도출할 수 있을 것으로 예상된다. 또한, 광범위한 범위를 스캐닝하기 위해 200 mm/s로 이동하는 연속스캐닝 기법을 검토하였고, 두께가 변화는 부재의 두께를 효과적으로 예측할 수 있었다. This study was initiated to develop an effective inspection method to detect defects such as corrosion in closed-cell steel members in steel-box girder bridges. The ultrasonic velocity method among various non-destructive method was selected as a rapid and effective method to derive the average propagation velocity in the medium by using the ultrasonic wave velocity method for specimens of different thickness. The regression analysis was performed based on the experimental results, and the results was interpolated to evaluate the prediction accuracy. If the material properties are identical, this ultrasonic velocity method can predict the thickness using the averaged transmitted velocity. In addition, a continuous scanning method moving at 200 mm/s was tested for scanning a wide area of a bridge. The results exhibited that the continuous scanning method was able to effectively scan the different thickness of a bridge.
가스 고속 샘플링 모듈 해석 및 가용 범위 결정에 관한 연구
김우석(Wooseok Kim),이석원(Sukwon Lee),이종화(Jonghwa Lee),박진일(Jinil Park),유재석(Jaisuk Yoo) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
As engine investigations in abnormal condition is recognized an important matter to meet strict enhanced emission regulations, needs of a fast response exhaust gas analyzer are getting stronger. A fast analyzing instrument of concentration should be designed to analyze gas concentration cycle by cycle by using fast sampling module and appropriate measuring methods for each emission elements. In this study, a fast sampling module with a new concept is introduced and flow analysis is performed using FLUENT code. According to the analysis, module's operating condition for applying engine and data for expecting measurement sensitivity are acquired. Calculated flow toward sampling module has 0.5~4% error, and back flow toward expansion tube is expected when CP chamber's pressure is over 0.6bar. For stable supply of flow toward optical cell, the pressure of sample gas should be 0.35~1.90bar when the pressure in the CP camber and the optical cell are 0.2bar and 0.158bar respectively.
[가솔린엔진부문] 흡기포트 분사식 LPG 엔진의 연료량 제어 및 연소 특성에 관한 연구
김우석(Wooseok Kim),이종화(Jonghwa Lee),장창현(changhyun Jang) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this paper. characteristics of a port injection type LPG fuel system were investigated to adopt the system 10 a spark ignition engine through rig test. It was also studied that engine combustion characteristics for limited conditions and the precise control method of LPG fuel supply. As a basic experiment, the effects and the relationships of parameters such as orifice area, fuel delivery pressure, fuel temperature and flow coefficient were established. From this, one dimensional compressible flow equation can be applied to control gaseous fuel flow rate by setting pressure difference between vaporizer and manifold to a certain range, for example about 1.2 bar in a naturally aspirated engine. The combustion analysis results of LPG engine were also compared with those of gasoline engine according to spark timing and load change. At part load and stoichiometric condition, the MBT spark timing of LPG fueled engine is retarded by 2' - 4'. CA compared to that of gasoline engine. On the contrary, the spark timing of LPG fueled engine can be advanced by 5' - 10' CA at WOT, which results from higher Octane Number of LPG fuel compared 10 gasoline.