• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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• pp.701-707
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• 2007

In this paper the vibration system is composed of a rotating cantilever pipe conveying fluid. The equation of motion is derived by using the Lagrange's equation. Generally, the system of pipe conveying fluid becomes unstable by flutter. Therefore, the influence of the rotating angular velocity, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe by the numerical method are studied. The influence of mass ratio, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the stability of a cantilever pipe are analytically clarified. The critical fluid velocity ($u_{cr}$) is proportional to the angular velocity of the cantilever pipe. In this paper Flutter(instability) is always occurred in the second mode of the system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.575-578
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• 2008

In this paper, the purpose is to investigate the stability and variation of natural frequency of a Timoshenko cantilever beam subjected to follower force and tip mass. In addition, an analysis of the flutter instability(flutter critical follower force) of a cantilever beam as slenderness ratio is investigated. The governing differential equations of a Timoshenko beam subjected to an end tangential follower force is derived via Hamilton;s principle. The two coupled governing differential equations are reduced to one fourth order ordinary differential equation in terms of the flexural displacement. Finally, the influence of the slenderness ratio and tip mass on the critical follower force and the natural frequency of a Timoshenko beam are investigated.

• Wind and Structures
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• v.6 no.4
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• pp.263-278
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• 2003

This study investigates the effects of a bridge deck's width-to-depth (B/H) ratio and turbulence on buffeting response and flutter critical wind speed of long-span bridges by conducting section model tests. A streamlined box section and a plate girder section, each with four B/H ratios, were tested in smooth and turbulent flows. The results show that for the box girders, the response increases with the B/H ratio, especially in the vertical direction. For the plate girders, the vertical response also increases with the B/H ratio. However, the torsional response decreases as the B/H ratio increases. Increasing the B/H ratio and intensity of turbulence tends to improve the bridge's aerodynamic stability. Experimental results obtained from the section model tests agree reasonably with the calculated results obtained from a numerical analysis.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.949-954
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• 2006

The purpose of this paper is to investigate the stability of tapered columns with clamped one end and carrying a tip mass of rotatory inertia with translational elastic support at the other end. The linearly tapered columns with the solid rectangular cross-section is adopted as the column taper. The differential equation governing free vibrations of such Beck columns is derived using the Bernoulli-Euler beam theory. Both the divergence and flutter critical loads are calculated from the load-frequency curves which are obtained by solving the differential equation. The critical loads are presented as functions of various non-dimensional system parameters: the taper type, the subtangential parameter, mass ratio and spring stiffness.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.961-966
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• 2008

In this paper, the purpose is to investigate the stability and variation of natural frequency of a Timoshenko cantilever beam subjected to Subtangential follower force and tip mass. In addition, an analysis of the flutter instability(flutter critical follower force) of a cantilever beam as slenderness ratio is investigated. The governing differential equations of a Timoshenko beam subjected to an end tangential follower force is derived via Hamilton;s principle. The two coupled governing differential equations are reduced to one fourth order ordinary differential equation in terms of the flexural displacement. Finally, the influence of the slenderness ratio and tip mass on the critical follower force and the natural frequency of a Timoshenko beam are investigated.

• 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.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.12
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• pp.1161-1169
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• 2007

In this paper, the dynamic stability of a rotating cantilever pipe conveying fluid with a crack is investigated by the numerical method. That is, the influence of the rotating angular velocity, mass ratio and crack severity on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating cantilever pipe are derived by using extended Hamilton's principle. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of fracture and always opened during the vibrations. Generally, the critical flow velocity for flutter is proportional to the rotating angular velocity of a pipe. Also, the critical flow velocity and stability maps of the rotating pipe system for the variation each parameter are obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.191-195
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• 2011

The airframe ground vibration tests were conducted on the KC-100 aircraft according to the regulation requirement, KAS 23.629(a)(2) and the modal characteristics for the target modes were measured. To make FE model tuning, a design sensitivity approach with engineering judgment was implemented using MSC/Nastran and Attune, a genetic algorithm based parameter optimization software. Based on the comparison between initial prediction and test results, design variables such as beam cross-sectional properties and spring stiffnesses were devised. As the results, the correlation of the FE model to the GVT results was made appropriately, meeting the goal of matching the target frequencies within 5%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.254-257
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• 2006

In this paper a dynamic behavior(natural frequency) of a cracked cantilever and simply supported pipe conveying fluid is presented. In addition, an analysis of the flutter and buckling instability of a cracked pipe conveying fluid subjected to a follower compressive load is presented. Based on the Euler-Bernouli beam theory, the equation of motion can be constructed by using the Lagrange's equation. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations.

• Wind and Structures
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• v.7 no.1
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• pp.41-54
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• 2004

An analysis refinement of the Messina Strait suspension bridge project has been recently required, concerning mainly the yaw angle effects on the multi-box deck section aerodynamics and the vortex shedding at low reduced velocities $V^*$. In particular the possible interaction of the axial flow with the large cross beams has been investigated. An original test rig has been designed at this purpose allowing for both forced motion and free motion aero elastic tests, varying the average angle of attack ${\alpha}$ and the deck yaw angle ${\beta}$. The hydraulic driven test rig allowed for both dynamic and stationary tests so that both the stationary coefficients and the flutter derivatives have been evaluated for each yaw angle. Specific free motion tests, taking advantage from the aeroelastic features of the section model, allowed also the study of the vortex shedding induced phenomena.