• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.526-531
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• 2003

Conventional modal analysis techniques are known to be inappropriate for asymmetrical rotor systems. when the equations of motion are written in the stationary coordinates, due to the presence of time varying parameters. This paper presents a generalized modal analysis method for asymmetrical rotor systems in the stationary coordinates, employing the modulated coordinates and the lambda matrix formulation. A numerical example with a flexible asymmetric rotor model is provided to demonstrate the effectiveness of the proposed modal analysis method. As an application of the proposed method, modal analysis is also performed with an open cracked rotor system.

• Journal of KSNVE
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• v.8 no.1
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• pp.203-211
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• 1998

In order to find out relationship between hit probability and gun firing of a moving tank, a turret and flexible gun system model has been developed using a recursive flexible multibody dynamics. For a firing simulation model, nodal coordinates for a finite element model of a flexible gun have been employed to include transverse loads to the gun tube due to moving bullet and ballistic pressure. Modal coordinates are also used to represent the motion induced gun vibration before a firing occurs. An efficient switching technique from modal equations to nodal equation has been introduced for an entire gun firing simulation with a rotating turret.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.2105-2108
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• 2007

지진해일이 발생하여 먼 거리를 전파할 때 코리올리스 힘이 지진해일의 거동에 매우 큰 영향을 준다. 또한 지진해일은 파장에 비해 파고가 작은 장파이기 때문에 먼 거리를 이동하는 지진해일의 해석에는 코리올리스 효과가 반영된 선형 천수방정식을 사용하는 것이 적절하다. 본 연구에서는 구면좌표계에서 유한차분기법을 사용하여 지진해일의 거동을 모의하였다. 대상 지진해일은 1983년 동해 중부 지진해일이다. 관측된 결과를 본 연구에서의 모의 결과와 비교하였다.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.899-904
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• 2004

Multibody dynamics formulation has been developed based on relative cartesian coordinates for subsystem analysis. Relative cartesian coordinates are defined with respect to a reference body of a subsystem. Relative cartesian formulation inherits the same merits of absolute cartesian formulation, such as generality and easy implementation. Two methods have been applied. One is Largrange Multiplier Elimination method and the other is independent coordinate method. A 1/4 car simulation has been carried out to verify the formulations. Since both methods provide identical results, it proves the validity of the formulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1339-1344
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• 2010

MSM (Modal Superposition Method) is a technique for analyzing structural durability by taking the vibration characteristics into consideration. In this paper, MSR (Modal Stress Recovery) method, which is similar to MSM, was reviewed to check its validity as a durability analysis method. The MSR method directly calculates the modal displacement time history in multibody dynamics analysis; as a result, the total analysis time is shorter than that of MSM method. We conduct durability analysis using the MSR method and a durability test of a torsion beam axle that is affected by various road loads within the natural frequency of the beam axle. The analysis results for critical location and durability were in good agreement with the respective test results. Therefore, durability analysis using the MSR method is effective in predicting the durability of the structures of various dynamic systems.

• Journal of Energy Engineering
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• v.22 no.1
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• pp.28-37
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• 2013

Stirred tank is widely used in various industries for mixing operations and chemical reactions for single- or multi-phase fluid systems. For designing agitator of high performance, quantity data of internal flow characteristics influenced by mixing performance are definitely confirmed but quantity analysis about the transient flow characteristics of complicate structure is recognized as difficult problem in the present. In this study, two models of commercial CFD code Fluent 6.3 used to propose suitable for the tank analysis. Agitation of Stirred tank is analyzed using a mixed model and the flow in the stirred tank is analyzed using a standard k-${\varepsilon}$ model. Multiple reference frame(MRF) and Sliding mesh(SM), the analysis techniques were used For compare a result of CFD with a visualization experiment result, to grasp internal flow and mixing characteristic in stirred tank and to present fundamental analysis method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.248-249
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• 2011

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.39-48
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• 1994

An equivalent homogeneous 3-D linear composite analysis and accomponying finite element program is presented for elastomeric bearings. This study is limited to the 3-D layered system with linear, elastic, isoparametric small deformation. And we used method of multiscale to model the 3-dimensional configurations and overall response of the layered elastomeric bearings with global and local coordinates. The primary dependent variables for the theory have been selected that require only $C_o$ continuity of the finite element analysis. As a result, it is very simple and computationally economical. The presented theory can also be applied easily to the analysis of nonlinear behavior of layered systems. And those of past are not applicable to nonlinear analysis, because it uses superposition theory. Numerical examples are presented to verify the theory and to illustrate potential applications of the analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.55-64
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• 2001

Industrial machines are sometimes exposed to the danger of earthquake. In the design of a mechanical system, this factor should be accounted for from the viewpoint of reliability to analyze a complex nonlinear structure system under random excitation is proposed. First, the actual random excitation, such as earthquake, is approximated to the corresponding Gaussian process for the statistical analysis. The modal equations of overall system are expanded sequentially. Then, the perturbed equations are synthesized into the overall system and solved in probabilistic way. Several statistical properties of a random process that are of interest in random vibration are evaluated in each substructure. Comparing with the results of the numerical simulation proved the efficiency of the proposed method.

• The Korean Journal of Applied Statistics
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• v.28 no.3
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• pp.485-494
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• 2015

Canonical correspondence analysis is an ordination method used to visualize the relationships among sites, species and environmental variables. However, projection results are fluctuations if the samples slightly change and consistent interpretation on ecological similarity among species tends to be difficult. We use the bootstrap methods for canonical correspondence analysis to solve this problem. The bootstrap method results show that the variations of coordinate points are inversely proportional to the number of observations and coverage rates with bootstrap confidence interval approximates to nominal probabilities.