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차체패널 성형공정 유한요소해석에 드로우비드 전문모델의 적용
금영탁(Young Tag Keum),김준환(Jun Hwan Kim) 한국자동차공학회 2000 한국 자동차공학회논문집 Vol.8 No.3
In order to show the efficiency and accuracy of an expert drawbead model, finite element simulations of auto-body panel stampings are carried out. For numerical modeling of the drawbead of a panel die, the drawbead restraining force and bead-exit thinning calculated by the expert model are imposed to a node nearest to the drawbead position as a boundary condition. Finite element simulations show that the expert model provides the accurate solution, guarantees the stable convergence, and has the merit in the computation time.
액체로켓의 연소안정을 위한 유량공급에 관한 실험적 연구
박희호,김유,조남춘,금영탁,Park, Hee-Ho,Kim, Yoo,Cho, Nam-Choon,Keum, Young-Tag 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.6
In liquid rocket engine, propellant feed rate is proportional to approximately square root of the pressure difference between injector head and combustion chamber. This ΔP depends on the engine design, but in general on the order of 50psi. However, during ignition period, especially for the pressurized feed system, combustion chamber pressure is almost atmospheric and large ΔP causes over flow of propellants which may lead to catastrophic accident due to hard start. Hard start may be prevented by applying cavitating venturi or/and two step ignition. In cavitating venturi, evaporated propellants near the venturi throat become chocked and flow rate depends on only upstream condition. In two step ignition propellants are supplied to the liquid engine in two different flow rate. First step, to avoid hard start, small amount of propellants are supplied to build up chamber pressure in safe zone, then full propellants to ensure design pressure. In this study, both cavitating venturi and two step ignition method were used for the hot test and hard start problem was completely solved.
이일랑(Il Lang Yi),정일용(Il Yong Chung),최병욱(Byung Wook Choi),금영탁(Young Tag Keum) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.11
In this paper, benchmark tests of Rapid Prototyping(RP) are presented to evaluate characteristics of various RP Systems and Processes, and several decision-support systems are developed to select RP Machine/Process suitable to user's requirements. Results of the RP benchmark tests are applied to the recently developed RP machines for the purpose of analyzing attributes such as dimensional accuracy, surface roughness, build cost, build time, and etc. Decision-making support systems are also developed, which contain not only new LCE (Linear Confidence Equation) algorithm but also modified PRES and MDS algorithm. Those algorithms are proved to be effective in that reasonably acceptable results are obtained on several cases of different inputs.