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권용철(Y. C. Kwon),김종혁(C. H. Kim),홍예선(Y. S. Hong),김상범(S. B. Kim) 유공압건설기계학회 2012 드라이브·컨트롤 Vol.9 No.3
In this study the flow rate-to-pressure difference characteristics of short-tube type damping orifices for an aircraft door damper were investigated by CFD analyses and experiments. As the design parameters of the damping orifice its diameter, inlet and outlet angle, tube length and the viscosity of the working fluid were taken into consideration. The results showed that the discharge coefficient of the orifices are dependant on the inlet and outlet angle and the oil viscosity, while their length plays an little significant role. Although the short-tube type damping orifice was employed to induce a turbulent flow, their discharge coefficient decreases rapidly as the oil viscosity gets higher than 50mm2/s. Therefore, in order to determine the orifice size, satisfying the working temperature range of the door damper, the oil viscosity as well as the friction force on the damper piston should be kept within proper values. For the verification of the CFD analysis results the actual performance of a door damper was measured and compared with them.
권용철(Y. C. Kwon),김종혁(C. H. Kim),홍예선(Y. S. Hong),김상범(S. B. Kim) 유공압건설기계학회 2012 유공압건설기계학회 학술대회논문집 Vol.2012 No.6
In this study the flow rate-to-pressure difference characteristics of short-tube type damping orifices for an aircraft door damper were investigated by CFD analyses and experiments. As the design parameters of the damping orifice its diameter, inlet and outlet angle, tube length and the viscosity of the working fluid were taken into consideration. The results showed that the discharge coefficient of the orifices are dependant on the inlet and outlet angle and the oil viscosity, while their length plays an little significant role. Although the short-tube type damping orifice was employed to induce a turbulent flow, their discharge coefficient decreases rapidly as the oil viscosity gets higher than 50cSt. Therefore, in order to determine the orifice size, satisfying the working temperature range of the door damper, the oil viscosity as well as the friction force on the damper piston should be kept within proper values. For the verification of the CFD analysis results the actual performance of a door damper was measured and compared with them.
풍력 발전기용 Door Frame의 제조 공정에 관한 연구
권용철(Y. C. Kwon),송명준(M. J. Song),강종훈(J. H. Kang),이성환(S. H.Lee) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
The Door Frame is a gate to the wind turbine generator tower, and manufactured through forging or plate welding. Mechanical properties and fatigue characteristics of this product are very important. New manufacturing method is suggested in this paper for short production time, uniform quality, smooth surface, close tolerance, and considerable material savings as much as 30%. The rigid-viscoplastic three-dimensional finite element analyses were applied to new process design and the thickness distribution, shape of final product were investigated. The prototypes of door frame were manufactured based on analyzed results. Productivity was stable, mechanical properties was increased and product dimension was optimized with newly suggested process. With FE analysis and prototype production, the advantages of new method such as productivity, mechanical properties and production cost were verified.
권용철(Y. C. Kwon) 유공압건설기계학회 2019 유공압건설기계학회 학술대회논문집 Vol.2019 No.6
HPM(High speed Power Matching) system is the electro-hydraulic control system that directly control the swash plate of pump by selecting 4 loop logic based on the joystick signal, pump flow and pressure signal to improve the efficiency and controllability of the construction machine. In the NFC(Negative Flow Control) system, which is a typical pump control system using conventional open center type MCV, the loss is continuously generated in the center bypass line even when the excavator is not operated. Also, due to the slow response of the pump that indirectly controls the pump flow rate using the pressure regulator, peak pressure occurs at the start or stop of operation. On the other hand, the HPM system uses the MCV without a center-by-pass flow path and the pump controller controls the swash plate of the pump directly. At this time, the pump can control the angle of the swash plate to almost 0 degree, so that unnecessary flow loss can be minimized in the excavator standby state. In addition, a quick swash plate control is possible to suppress peak pressure generation by the channel block at the instantaneous MCV spool neutral position at the start or stop of the excavator operation. In this paper, the concept of HPM system algorithm is introduced and the hydraulic system efficiency of HPM system and NFC system using excavator SAT(System Analysis Tool) is compared and analyzed.
주조 잉고트의 코깅공정시 기공압착 분석을 위한 유한요소해석
권용철(Y.C. Kwon),이정환(J.H. Lee),이승욱(S.W. Lee),정용수(Y.S. Jeong),김남수(N.S. Kim),이영선(Y.S. Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
In the steel industry, there is a need to produce large forged parts for the automobile industries, the flight and shipping industries and military industries. In many steel-industry application, a cogging technique for cast ingots is required, because the major parts are needed as one large body in order to obtain higher quality. Therefore, cogging is the primary step in manufacturing of practically large open-die forging. In the cogging process, internal voids have to be eliminated as defects, The present work is concerned with the elimination of the internal voids in large ingots so as to obtain sound products. In this study, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperatures and strain rates. The FEM analysis are performed to investigate the overlap defect of cast ingots from the first ingot to bloom. Also the analysis of void closure are performed by using the DEFORM™ -3D.
풍력용 중공형 메인샤프트의 열처리공정 최적화를 위한 예비 성형체 및 냉각방법 연구
권용철(Y. C. Kwon),김홍태(H. T. Kim),김상식(S. S. Kim) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
Main shaft is one of the most important mechanical components for wind turbine. Large forged parts are most being manufactured with hot open die forging. Then these components progress heat treatment process to increase mechanical properties. Heat treatment of Hollow Main Shaft is doing using forged part. One of the general defects of these parts is Quenching crack during heat treatment. In this paper, to prevent the Quenching crack, FE-Analysis is performed to determine the optimum perform design and Quenching method. This calculated results confirmed temperature, stress change and micro-structure distribution according to perform shape and cooling method during heat treatment cycle. From the results, the prototypes of Hollow Main Shaft were manufactured based on analyzed results, productivity was stable, Also To evaluate mechanical properties this part, Specimens for tensile test and impact test were taken various region of manufactured Hollow Main Shaft.