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민옥기(Min. Oak-Key),박명식(Park. Myung-Sik) 한국자동차공학회 1987 오토저널 Vol.9 No.6
컴퓨터의 발달에 따라 이를 이용한 자연과학 분야의 분제해석도 많은 발전을 보이고 있다.수치해석으로 알려진 여러방법중에서 유한요소법이 가장 광범위하게 응용되고 있으며, 이러한 응용분야는 구조해석, 열전도, 유체흐름, 및 전사장 등 다양하다.또한 개인용 컴퓨터의 발달과 함께 소규모로 운영할 수 있는 전문적인 프로그램이 다수 개발되어 적절한 프로그램의 신정이 어려워지고 있다. A.Niku-Lari^1) 가 전문구조해석 시스템의 이론적 배경, 응용, 프로그램설명, 하드웨어, 및 응용예 등을 요약하였으며, B.Fredriksson과 J.Markerle^2) 은 범용 프로그램의 기능을 정리하였다. 본 란에서는 상용 유한요소 프로그램의 범용성과 그 한계 등을 B.Fredriksson과 J.Mackerle가 정리한 내용을 소개하는 방법을 통해 알아보고자 한다. 또한 A.Niku-Lari 가 요약한 도표를 소개하여 각 프로그램을 비교하는데 도움이 되도록 하였다.이를 통해 해석하고자 하는 문제의 설정, 이용가능한 상용프로그램의 선정, 이의 이용을 통해 얻을수 있는 경과의 유용성 등을 프로그램을 직접 취급 하기전에 검토하여 볼 수 있으리라 기대한다.
문원주,민옥기,김용우,Moon, Won-Joo,Min, Oak-Key,Kim, Yong-Woo 대한기계학회 1993 대한기계학회논문집 Vol.17 No.7
This paper presents the theoretical natural frequencies of out-of-plane deformable ring based on the variables such as out-of-plane deflection, torsional rotation and shear rotation. Based on the same variables, a finite element eigen analysis is carried out by using the $C^0$-continuous, isoparametric element which has three nodes per element and three degrees-of-freedom at each node. Numerical experiments are peformed to find the integration scheme which produces accurate natural frequencies, natural modes and correct rigid body motion. The uniformly reduced integration and the selective reduced integration give more accurate numerical frequencies than the uniformly full integration, but the uniformly reduced integration produces incorrect rigid body motion while selective reduced integration does correct one. Therefore, the ring element based on the three variables which employes selective reduced integration is recommended to avoid spurious modes, to alleviate the error due to shear locking and to produce correct rigid body motion, simultaneously.
문원주,김용우,민옥기,이강원,Moon, Won-joo,Kim, Yong-woo,Min, Oak-key,Lee, Kang-won 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.12
Since the skew beam element has two curvatures which are a curvature and a torsion, spatial behavior of curved beam which cannot be included in one plane can be anlayzed by emploting the skew beam element. The $C^{0}$-continuous skew beam element shows the stiffness locking phenomenon when full integration is employed. The locking phenomenpn is characterized by two typical phenomena ; one is the much smaller displacement thant the exact one and theother is the undelation phenomenon is stress distribution. In this paper, we examine how unmatched coefficient in the constrained energy brings about the locking by Reduced Minimization theory. We perform the numerical ones. These comparisons show that uniformly full integration(UFI), which employs full integration for the constrained energy, entails the locking phenomenon. But the use of uniformly reduced integration(URI) of selectively reduced integration(SRI), which employs reduced integration for constrained energy, does not produce the significant errors of displacements of the undulation phenomenon in stress distribution since they do not entails the locking, Additionally, the error due to the approximated parameters for describing the geometry of skew beam is examined.d.
유승원(Yoo Seungwon),민옥기(Min Oak-key),박춘수(Park Choonsoo),정흥채(Chung Heungchai) 한국철도학회 2000 한국철도학회 학술발표대회논문집 Vol.- No.-
This paper describes the analysis of aerodynamics and the prediction of airflow induced noise around simplified pantograph. First, computational fluid dynamics (CFD) is conducted for several model to evaluate linear/nonlinear flow field characteristics due to high speed flow and the CFD results support the computational aeroacoustics. The accurate prediction of the aeroacoustic analysis is necessary for designers to control and reduce the airflow induced noise. We adopt the acoustic analogy based on Ffowcs Williams-Hawkings (FW-H) equation and predict aeroacoustic noise.
이인규(In-gyu Lee),양현모(Hyun-mo Yang),민옥기(Oak-Key Min) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Split Hopkinson Pressure Bar (SHPB) has been used to find out the true flow stress-strain relationship of materials. In this study, the SHPB is used with heating apparatus in order to observe the effect of temperature in Aluminum 2024-T4. For the purpose of accuracy in design, it is important to know how dynamic behavior of the material is changed at room temperature as well as at high temperature. To determine the true flow stress-strain relationship of the Aluminum 2024-T4, the specimens are tested from room temperature to 400℃ with an interval of 100℃ at strain rate of 1500/sec. Additional tests at temperatures, between 230℃ and 250℃, are conducted because of significant change of the true flow stress in these temperature range. For constitutive equation from the true flow stress-strain relationship, the Johnson-Cook constitutive equation and the modified Johnson-Cook constitutive equation are used, and parameters in the constitutive equations are determined.
권해성,민옥기 연세대학교 산업기술연구소 1993 논문집 Vol.25 No.1
The running mechanism of flexible and thin foil above rotating protrusion is analyzed throught a numerical simulation. The scope of analysis is confined to the phenomena of elastohydrodynamic lubrication between the rotary drum with a running protrusion and thin foil. This mathematical analysis is based on the modified Reynolds equation and the equation of plate, considering the protrusion geometry and the effect of geometric nonlinearity. Finite element method is adopted as a numerical simulation method to solve the above coupled nonlinear equations. In numerical analysis, the effects of head window in rotary drum are evaluated. And the analysis results of the window model are compared with the those of no window model.
민옥기,권해성 연세대학교 산업기술연구소 1991 논문집 Vol.23 No.2
This study analyzes the running mechanism of flexible and thin tape above rotating protuberance through the numerical simulation. The scope of analysis is confined to the phenomena of elasto-hydrodynamic lubrication between the rotating cylinder with a protuberance and the running tape. This model is based on the equation of plate considering the effect of geometric nonlinearity and the modified Reynolds equation. Finite element method is adopted as a numerical simulation technique to solve the above two coupled nonlinear equations. In numerical analysis, the effects of tape tension and the relative velocity are basically evaluated.