• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 춘계학술대회 논문집
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• pp.118-128
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• 1994

The planar anisotropic FEM analysis for predicting the earing profiles and draw-in amounts in the deep-drawing processes is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-based unit vectors and the normal contact pressure. the consistent full set of governing relations, comprising equilibrium and geometric constraint equations, is appropriately linearized. Barlat's strain-rate potential is employed, whose in-plane anisotropic properties are taken into account with anisotropic coefficients and potential parameter. The linear triangular membrane elements are used for depicting the formed sheet. with the numerical simulations of deep drawing processes of flat-top cylindrical cup for the 2090-T3 aluminum effects on the earing behavior are examined. Earing predictions made for the 2090-T3 aluminum alloy sheet show good agreement with experiments, although some discrepancies were observed in the directional trend of cup height and thickness strains.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.959-961
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• 1996

In this paper, we study the modeling and control of Electro-Magnetic Suspension System with 2 Degree Of Freedom. While the previous researchers considered the control of single rail EMS Systems, we consider the control of two rail EMS Systems. We first derive a simple model to represent the dynamics of EMS System with 2 D.O.F., using the Lagrange's method. The nonlinear equations of motion that we derive are shown to be linearizable by coordinate change and nonlinear static state feedback. The nonlinear static state feedback controller is constructed explicitly.

• Journal of the Korean Physical Society
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• 제73권10호
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• pp.1410-1419
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• 2018

A skier's motion was analyzed by a simple model consist of point mass m and a single rod connected to a single ski plate. We studied the conditions for the stable ski turn as functions of the linear velocity and the radius of the turn. The solutions for the stable ski turn in our model do not require any extra skier's movement to complete a stable circular turn. The solution may then give the skier the most comfortable skiing method without any active movement to control the ski. The generalized force supporting the point mass from the ski plate was calculated. We obtained the force from the ground (rebound force) without any geometrical structure of the ski plate. Adding an active movement to the direction of the ski plate, the conditions for the stable ski turn were also analyzed. Our result gives some insight for the skier who wants to develop technique.

• 한국정밀공학회지
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• 제14권9호
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• pp.124-129
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• 1997

The purpose of this study is to predict the stability and frequency response of multipurpose vehicle. The vehicle model has seven degrees of freedom. The motion equations are derived by using Lagrangian equation and linearized. The positions of eigenvalues of model which are dominated by lateral velocity, yaw rate, roll rate of sprung mass are used to predict the stability of motion. The resonse of sprung mass to steering wheel is simulated in time domain. It is predicted that the roll response of sprung mass would rather be improved by modifying the position of eigenvalues. The responses of sprung mass to steering wheel are also simulated in frequency domain. The magnitude and phase plots of gains are evaluated in driver's steering input frequency range.

• 대한기계학회논문집B
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• 제23권8호
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• pp.1022-1030
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• 1999

A numerical study was carried out to analyze the effect of flow distribution of stirred part and plug flow part on combustion efficiency at the coal gasification process in an entrained bed coal reactor. The model of computation was based on gas phase eulerian balance equations of mass and momentum. The solid phase was described by lagrangian equations of motion. The $k-{\varepsilon}$ model was used to calculate the turbulence flow and eddy dissipation model was used to describe the gas phase reaction rate. The radiation was solved using a Monte-Carlo method. One-step parallel two reaction model was employed for the devolatilization process of a high volatile bituminous Kideco coal. The computations agreed well with the experiments, but the flame front was closer to the burner than the measured one. The flow distribution of a stirred part and a plug flow part in a reactor was a function of the magnitude of recirculation zone resulted from the swirl. The combustion efficiency was enhanced with decreasing stirred part and the maximum value was found around S=1.2, having the minimum stirred part. The combustion efficiency resulted from not only the flow distribution but also the particle residence time through the hot reaction zone of the stirred part, in particular for the weak swirl without IRZ(internal recirculation zone) and the long lifted flame.

• 한국정밀공학회지
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• 제31권10호
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• pp.897-904
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• 2014

In this paper, two-DOF parallel manipulator has the sliders which execute a linear reciprocating motion depending on parallel guides and the end-effector which can be adjusted arbitrarily. To investigate the dynamic characteristics of the manipulator, the dynamic performance index is used. The index is able to be obtained by the relation between the Jacobian matrix and the inertia matrix. The kinematic and the dynamic analysis find these matrices. Also, the dynamic model of the manipulator is derived from the Lagrange formula. This model represents complicated nonlinear equations of motion. With the simulation results of the dynamic characteristic of the manipulator, we find that the dynamic performance index is based on the selection of the ranges for the continuous movement of the manipulator and the dynamic model derived can be used to the control algorithm development of the manipulator.

• 전산구조공학
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• 제10권4호
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• pp.205-216
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• 1997

구속된 ?(restrained warping)효과를 고려하는 박벽 공간뼈대구조의 횡후좌굴거동을 조사하기 위하여 기하학적 비선형 유한요소이론 및 해석법을 제시한다. 가상일의 원리를 이용하여 대변형효과를 고려한 3차원 연속체의 평형방정식으로부터, 구속된 ?효과를 고려하고 유한한 회전각의 2차항의 효과를 포함하는 변위장을 도입하여 초기응력을 받는 박벽 공간뼈대요소의 증분평형방정식을 유도한다. 박벽 공간뼈대구조를 유한요소로 나누고 변위장을 요소변위에 관한 Hermitian 다항식으로 나타내어 이를 평형방정식에 대입함으로써 접선강도행렬을 유도한다. 또한 updated Lagrangian formulation에 근거하여, 증분변위로부터 강체회전변위와 순수변형성분을 분리시켜서 강체회전은 요소의 방향변화를 결정하고, 순수변형은 부재력증분을 산정하는 불평형하중 산정법을 제시한다. 박벽 공간뼈대구조의 횡-비틂좌굴 및 후좌굴 거동에 대한 예제들을 통하여 본 연구에 대한 해석결과와 문헌의 결과를 비교 검토함으로써 본 연구에서 제시된 이론 및 해석방법의 정당성을 입증한다.

• 전산구조공학
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• 제10권1호
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• pp.201-211
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• 1997

공간뼈대의 구조에 대하여 기하학적 비선형성이 고려될 수 있는 유한요소이론 및 해석법을 제시한다. 이를 위하여 가상일의 원리를 이용하여 대변형효과를 고려한 3차원 연소체의 평형방정식으로부터, 구속된(restrained warping)효과를 무시하고 유한한 회전각의 2차항의 효과를 포함하는 변위장을 도입하여 초기응력을 받는 공간뼈대요소의 증분평형방정식을 유도한다. 공간뼈대구조를 유한요소로 나누어 요소의 변위장을 요소변위 벡터에 관한 Hermitian다항식으로 나타내고 이를 평형방정식에 대입함으로써 탄성 및 가하학적인 강도행렬을 유도한다. 또한 updated Lagrangian co-rotational formulation에 근거하여, 증분변위로부터 강체회전변위와 순수변형성분을 분리시켜서 강체회전은 요소의 방향변화를 결정하고, 순수변형은 부재력증분을 산정하는 불평형하중 산정법을 제시한다. 공간뼈대구조의 횡-비틂좌굴 및 후좌굴 거동에 대한 예제들을 통하여 본 연구에 대한 해석결과와 문헌의 결과를 비교 검토함으로써 본 연구에서 제시된 이론 및 해석방법의 정당성을 입증한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.737-742
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• 2002

This reaserch is concern with dynamic modeling of satellite with deployable solar arrays equipped with strain energy hinges(SEH). It is found from experiments that the SEH has the nonlinear dynamic characteristics and complex buckling behavior which is difficult to explain theoretically. In this paper, we use an equivalent one dimensional nonlinear torsional spring for the SEH. Lagrangian equations of motion are used for the derivations.

• 한국전산유체공학회지
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• 제2권1호
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• pp.54-65
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• 1997

Wall wetting in diesel engines has been considered as a bad phenomenon because of fuel deposition which makes fuel/air mixing and evaporation worse. In order to avoid the problem, many research works have been carried out. One of the studies is on new combustion chamber systems which are using spray impacting on a wall. In this study a new type of chamber system is analysed using wall impaction model introduced and assessed in the coupled paper. The gas phase is modelled in terms of the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction, The liquid phase is modelled following the discrete droplet model approach in Lagrangian form. With various conditions the spray distribution, vapor contour and gas flows are analyzed, and then design factors of those combustion systems are recommended.