• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.3
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• pp.127-132
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• 2010

Eigensolutions associated with self-excited vibration of disc brake system can be obtained by complex eigenvalue analysis. The eigenvalue sensitivity to change in contact stiffness can be used to demonstrate stability criteria and eigenvalue veering. Dynamic instability on eigenvalue loci with respect to the variation of contact stiffness is found to be related to mode interaction between two adjacent modes. This modal interaction can be effectively shown by mode shape visualization. This paper presents the methodology to construct the mode shape of disc brake system where a disc and two brake pads are coupled with contact stiffness.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.365-377
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• 2017

In this paper, we propose a method to identify the parameters of a rotorcraft slung load system using the modal characteristics of a flexible cable. The proposed method estimates the length of the cable and the mass of the payload by means of a frequency analysis. Dynamic equations of the slung load system with the flexible cable are derived using Udwadia-Kalaba equation (UKE) in order to build a simulation program, and the similarity of the simulated slung load movement is verified by comparison with flight test results. Using the computer simulation program, we show that the proposed method works well within various parameter ranges.

• Wind and Structures
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• v.4 no.1
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• pp.63-72
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• 2001

This paper presents results of a study on wind loads and wind induced dynamic response of bridge jointed twin-towered buildings. Utilizing the high-frequency force balance technique, the drag and moment coefficients measured in wind tunnel tests, and the maximum acceleration rms values on the top floor of towers, are analyzed to examine the influence of building's plan shapes and of intervals between towers. The alongwind, acrosswind and torsional modal force spectra are investigated for generic bridge jointed twin-towered building models which cover twin squares, twin rhombuses, twin triangles, twin triangles with sharp corners cut off, twin rectangles and individual rectangle with the same outline aspect ratio as the twin rectangles. The analysis of the statistical correlation among three components of the aerodynamic force corroborated that the correlation between acrosswind and torsional forces is significant for bridge jointed twin-towered buildings.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1042-1045
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• 1999

This paper presents a new method for contingency selection of the transient stability. Contingency ranking in transient stability is done by estimating the change in the imaginary part of electro-mechanical oscillation mode, which represents modal synchronizing coefficient. And the change in the imaginary part is obtained by applying eigen-sensitivity theory of augmented matrix to linear system model. The Proposed algorithm was tested for New England System and compared the results with PSS/E dynamic simulation.

• Aerospace Engineering and Technology
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• v.3 no.2
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• pp.149-159
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• 2004

Dynamic analysis of laminated beams with a embedded damping layer under tensional and compressive axial load is investigated. Improved Layer-Wise Zig-Zag Beam Theory and Interdependent Kinematic Relation are incorporated to model the laminated beams with a damping layer and a corresponding beam zig-zag finite element is developed. Flexural frequencies and modal loss factors under tension or compression axial load are calculated based on Complex Eigenvalue Method. The effects of the axial tensional and compressive load on the frequencies and loss factors are discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1133-1145
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• 2000

It is necessary to develop an efficient analysis method to identify the dynamic characteristics of a large mechanical structure and update its finite element model. That is because these processes need the huge computation of a large structure and iterative estimation due to the use of the first- order sensitivity. To efficiently carry out these processes, a new method, called the generalized free-interface mode sensitivity method, has been proposed in the authors' preceeding paper. This method is based on substructuring approach such as a free-interface method and a generalized synthesis algorithm. In this paper, the proposed method is applied to the model updating of a car body structure to verify its accuracy and reliability for a large mechanical structure.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.484-487
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• 2003

In designing AMBs (active magnetic bearings) for high-speed spindle system, the shaft is usually assumed as a rigid rotor. For automatic tool change process, there should be a tool clamping system with drawbar using spring or hydraulic force, and the drawbar in the spindle can be in various condition of support during design and manufacturing error. In this paper, the modal characteristics of drawbar in high-speed milling spindle system due to supporting stiffness between drawbar and shaft are analyzed by numerical method. The result shows enough stiff supports must be provided between shaft and drawbar to prevent occurring drawbar vibration lower than the natural frequency of 1$\^$st/ bending mode of spindle.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1091-1096
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• 2007

Since Maglev vehicle is run over an elevated guideway, the structural properties of guideways affect the running behavior of the vehicle and guideway. The design of a guideway has a strong effect on the costs of constructing guideways, therefore optimized design of the guideway satisfying running performance is needed for the commercialization of the Maglev vehicle. With an analysis program for dynamics of Maglev vehicles, the dynamic responses of the Maglev vehicle with electromagnet suspension are numerically analyzed according to changes in fundamental modal damping ratio of a guideway.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.3 s.18
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• pp.149-156
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• 2004

In this study, vibration and aeroelastic analyses of a T-tail have been conducted. The structural dynamic computations of the T-tail are performed using MSC/NASTRAN and CFD-based computational aeroelastic analysis method is used to investigate the complex flutter phenomena. The results for vibration and aeroelastic analyses in the frequency and time domains are presented. It is importantly shown that the modal coupling of the torsional mode of vertical-wing and the asymmetric bending mode of horizontal-wing parts can give sensitive effects for the flutter stability of T-tail configurations.

• Journal of KSNVE
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• v.9 no.5
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• pp.1029-1035
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• 1999

This paper relates to the flexural vibration analysis of slender spindle systems with multiple thin disks, supported by the ball bearings by means of the finite element method. Each system component is analytically modeled taking into account its flexibility and also the centrifugal effect especially for the disk. In order to show the rapid convergence rate and accuracy of the proposed approach, an experimental set-up is built to be versatile. In two distinct cases, its natural modes are numerically computed using only a small number of total element meshes as the shaft rotational speed is varied, and verified through experimental frequency response function obtained by the impact test.