• Tribology and Lubricants
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• 제13권4호
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• pp.53-59
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• 1997

The camshaft locus at camshaft beating in a direct acting OHC valve train system has been investigated using the transient method. Forces applied to the camsfiaft are composed of two components, one is the transfer force between the cam and the tappet, the other is the frictional force. These forces have been calculated using the lumped mass model and the elastohydrodynamic lubrication theory. The alternating direction implicit method has been used for the numerical analysis of Reynolds equation, and 4th order Runge-Kutta method has been used for the transient journal locus analysis. The effects of various load conditions are presented in the form of journal locus. As a result of the analysis, it has been found that camshaft bearings were mainly in the hydrodynamic lubrication condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.90-92
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• 1993

Stability analysis is an essential work in the operation and planning of power system. There are two categories, direct method and indirect method, and indirect method calculates the trajectories of states by numerical methods. Popular method using explicit integration has relatively low accuracy, so a more accurate method is requested. By the consideration of bus voltage variation, Runge-Kutta 4th order method can be made more accurate, but this scheme need much computation time. Through three recipes, computational cost of proposed method can be reduced. So the proposed method has improved accuracy and slight rise in cost. the method was tested on the IEEE 14 bus system.

• 전기학회논문지
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• 제61권8호
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• pp.1123-1129
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• 2012

This paper presents the fast steady state analysis using time-stepping finite element method for a high power three-phase transformer. The high power transformer spends huge computational cost of the time-stepping finite element method. It is because that the high power transformer requires a lot of time to reach steady state by its large inductance component. In order to reduce computational cost, in this paper, the adaptive time-step control algorithm combined with the embedded 2nd 4th singly diagonally implicit Runge-Kutta method and the analysis strategy using variation of the winding resistance are studied, and their numerical results are compared with those from the typical time-stepping finite element method.

• Structural Engineering and Mechanics
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• 제30권5호
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• pp.593-602
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• 2008

This paper presents a new linearization algorithm to find the periodic solutions of the Duffing equation, under harmonic loads. Since the Duffing equation models a single degree of freedom system with a cubic nonlinear term in the restoring force, finding its periodic solutions using classical harmonic balance (HB) approach requires numerical integration. The algorithm developed in this paper replaces the integrals appearing in the classical HB method with triangular matrices that are evaluated algebraically. The computational cost of using increased number of frequency components in the matrixbased linearization approach is much smaller than its integration-based counterpart. The algorithm is computationally efficient; it only takes a few iterations within the region of convergence. An example comparing the results of the linearization algorithm with the "exact" solutions from a 4th order Runge- Kutta method are presented. The accuracy and speed of the algorithm is compared to the classical HB method, and the limitations of the algorithm are discussed.

• 한국자동차공학회논문집
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• 제6권4호
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• pp.17-23
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• 1998

This paper presents the motion of dynamically loaded journal in the connecting rod bearing of reciprocation internal combustion engine. Journal motions in engine bearings have been composed of two components, which was rotational and translational motion. Early study of journal locus in engine bearing had been performed on each motion. This paper has been considered two motions simultaneously. Reynolds equation including the squeeze effect has been analyzed using the ADI method, and real engine bearing and crankshaft system has been considered to calculate the cyclic external force. The equations are performed by 4th order Runge-Kutta method. This paper gives various journal orbits in connecting rod bearing depending on cyclic external forces, rotation speeds, and bearing parameters.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.1-8
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• 2004

For the linearized differential algebraic equation of the nonlinear constrained system, exact initial values of the acceleration are needed to solve itself. It may be very troublesome to perform the inverse operation for obtaining the incremental quantities since the mass matrix contains the zero element in the diagonal. This fact makes the mass matrix impossible to be positive definite. To overcome this singularity phenomenon the mass matrix needs to be modified to allow the feasible application of predictor and corrector in the iterative computation. In this paper the proposed numerical algorithm based on the modified mass matrix combines the conventional implicit algorithm, Newton-Raphson method and Newmark method. The numerical example presents reliabilities for the proposed algorithm via comparisons of the 4th order Runge-kutta method. The proposed algorithm seems to be satisfactory even though the acceleration, Lagrange multiplier, and energy show unstable behaviour. Correspondingly, it provides one important clue to another algorithm for the enhancement of the numerical results.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.167-175
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• 1997

The locus of a camshaft supported on camshaft bearings has been investigated using transient method. Forces applied to camshaft are composed of two components, one is transfer force between cam and tappet, the other is frictional force. These forces have been calculated using lumped mass model and EHL theory. ADI method has been used for numerical analysis of Reynolds equation, and 4th order Runge-Kutta method has been used for transient journal locus analysis. The effects of various load conditions are presented in the form of journal locus. As the result of analysis, it is found that camshaft bearings exist in the hydrodynamic lubrication condition.

• 항공우주기술
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• 제6권1호
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• pp.19-28
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• 2007

본 연구에서는 올레오-뉴메틱(Oleo-pneumatic) 완충장치와 차등 제동 조향(Differential Braking Steering)을 위한 캐스터링 휠 포크(Castering Wheel Fork)가 적용된 소형항공기용 전방착륙장치의 충격하중 해석을 위한 비선형 2 자유도 수학적 모델을 생성하고, 수치해석 기법을 이용하여 시간에 따른 충격응답을 구하였다. 생성된 전방착륙장치의 수학적 모델은 타이어의 충격 시 동적 특성과 스트루트 기울기, 캐스터에 의한 모멘트, 타이어 접촉과 조향 등에 의해 발생하는 측면하중에 의한 올레오 스트루트 내부의 마찰 특성 등의 비선형 요소들을 포함하고 있다. 또 생성된 운동방정식의 수치해석은 4차 Runge-Kutta 방식을 이용하였으며, 운동방정식 및 수치해의 정확도를 평가하기 위한 타 항공기에 기 적용된 전방 착륙장치의 낙하시험 결과와의 비교 검증과정을 수행하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.396-401
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• 2006

Dynamic behaviors of the impact damper are studied experimentally and numerically. In order to investigate wide range of excitation frequencies and amplitudes, a simple but high amplifying and bias-free experimental setup is designed. Experiments focused on the harsh operation condition demonstrate Accelerated mass loading which not only deteriorates the performance of the impact damper but also involves the structural resonance which should be avoided for the stability of the system. In the previous studies, instability or deterioration of the performance was reported for the off resonance frequency region. But this paper shows that the performance deterioration and structural resonances can be predicted. Using finite element modeling and analysis, accurate system parameters were derived and used for the numerical modeling employing the conservation of the momentum. Numerical study of the transient responses using 4th-order Runge-Kutta method demonstrates general performance of the system, and shows that accelerated mass loading phenomenon is deeply related with the vibration amplitudes and the mass of the auxiliary system.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.183-189
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• 1997

This paper presents the motion of dynamically loaded journal in the connecting rod bearing of reciprocating internal combustion engine. Journal motions in engine bearings have been composed of two components, which was rotational and translational motion. Early study of journal locus in engine bearing had been performed on each motion. This paper has been considered two motions simultaneously. Reynolds equation including the squeeze effect has been analyzed using the ADI method, and real engine bearing and crankshaft system has been considered to calculate the cyclic external force. The equations of journal motion have been derived and then the numerical integration of these equations performed by 4th order Runge-Kutta method. This paper gives various journal orbits in connecting rod bearing depending on cyclic external forces, rotating speeds, and bearing parameters.