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420J2 마르텐사이트계 스테인레스강의 오스테나이트화 온도가 기계적 성질에 미치는 영향
김용길,김영주,김기돈,성장현 ( Y . G . Kim,Y . J . Kim,G . D . Kim,J . H . Sung ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.2
For the purpose of investigating the effect of austenitizing temperatures on the mechanical properties of 0.23%C-13.6%Cr martensitic stainless steel, tensile properties, hardness, impact value and carbide extraction were examined after changing the austenitizing temperatures and tempering temperatures. The results obtained are summerized as follows. The carbide laminations formed from hot rolling before austenitization could not be eliminated after austenitizing at 950℃. With increasing austenitizing temperature, hardness increased and showed maximum value at 1050℃ and then slightly decreased. With increasing tempering temperature up to 500℃, impact value and elongation appeard to be decreased but hardness showed nearly unchanged at austenitizing temperature of 1150℃ due to the fine M_7C₃carbides precipitation. The abrupt increase in impact value, hardness and elongation above the tempering temperature of 500℃ appeared to change in carbide structure from fine M_7C₃to coarse M_(23)C_6.
유압 피스톤 펌프의 전자제어를 위한 EPPR 밸브의 해석모델 개발 및 특성 분석
이근호(G. H. Lee),함영복(Y. B. Ham),윤소남(S. N. Yoon),김홍욱(H. U. Kim),하룬 아흐마드 칸(H. A. Khan),김용길(Y. K. Kim),김당주(D. J. Kim),손호연(H. Y. Son),김수태(S. T. Kim) 유공압건설기계학회 2019 유공압건설기계학회 학술대회논문집 Vol.2019 No.6
This paper is a study to apply EPPR valve for the electronic control of variable displacement hydraulic piston pump. In order to adjust the displacement of the pump, a regulator capable of controlling the swash plate angle is required. I apply the EPPR valve which is a valve that controls the output pressure by proportional current. It can be applied to control the swash plate angle with the advantage of excellent response, competitive price and electronic control. So this study deals with the development of analytical model and analysis of characteristics of EPPR valve by using SimulationX.
김현수(H. S. Kim),강호석(H. S. Kang),김용길(Y. G. Kim),김용조(Y. J. Kim) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.10
In order achieve a high durability and light weight, a suspension control arm, which has absorbed vibration and impact, for motor vehicles has been designed a very complex cross-sectional shape. It is very difficult to a hot forging process because the cross-sectional area in the middle body of the control arm is relatively small compared to the ends of the control arm, and the middle body has twisted in the longitudinal direction. In this study, a four step forging process was investigated. The hot forging process consists of; 1)preform by forging roll, 2)bending, 3)blocker, and 4)finisher. However, the investigation of the preform of the forging roll, in order to reduce the material input weight per forging weight, focused on the preform on the forging roll stage. The hot forging processes were conducted using FE simulations, the simulation results have been compared with experimental results and also relatively in good agreement with the experimental results.
스퀴즈 효과를 고려한 사판식 피스톤 펌프 홀더의 부하특성에 대한 연구
주경진(G. J. Ju),김수태(S. T. Kim),김용길(Y. K. Kim) 유공압건설기계학회 2019 유공압건설기계학회 학술대회논문집 Vol.2019 No.6
The load characteristics of the piston pump holder due to the squeeze effect are influenced by the surface shape and the gap thickness of holder. Therefore, the pressure distribution and the load capacity of piston pump holder due to the squeeze effect are studied using CFD software and the surface shape and the gap thickness of piston pump holder are considered. In order to verify the accuracy of the numerical analysis results, a circular plate holder is numerically analyzed and the accuracy of the numerical results is verified by comparing with the theoretical results. Numerical analysis on the load characteristics of a rectangular plate holder for the piston pump are performed by applying the results of circular plate holder. And the pressure distribution and load capacity of the rectangular plate holder are obtained. The results show that both maximum pressure and load capacity of the square plate holder without grooves are highest and the effects of the number and arrangement of grooves on the load capacity of holder are weak. We are concluded that the load capacity and the maximum pressure are slightly affected due to the existence of grooves on the holder surface and the fluid storaging effect of holder surface grooves during operation is possible to prevent the dry-sticking phenomenon.