• 항공우주기술
• /
• 제6권1호
• /
• pp.35-44
• /
• 2007

본 연구에서는 선미익을 채용한 경항공기인 반디호의 수출형 시제기에 대한 플러터 해석을 수행하였다. 내부 하중 생성용 유한요소모델을 기초로 강성 모델을 작성하였고, 중량 통제를 위한 중량 DB에 근거하여 중량 모델을 작성하였다. 공력모델은 DLM을 이용하였다. 작성된 모델을 이용하여 1차 플러터 해석을 수행하였다. 이를 토대로 주요 진동 모드를 구분해 내고, 지상진동시험을 수행하여 진동 특성을 획득하였다. 획득된 고유진동수를 근거로 유한요소모델의 수정이 이루어졌고 2차 해석이 수행되었다. 해석 결과 주요 플러터 근의 특성을 정리하였다. 가장 중요한 플러터 근은 롤 운동을 갖는 강체 모드와 반대칭 주익 피칭 모드의 연계 모드로 판명되었다.

• 한국군사과학기술학회지
• /
• 제5권4호
• /
• pp.81-87
• /
• 2002

In this paper, the transonic aeroelastic behavior of the generic fighter model is investigated in the time domain. The simulation of flutter flight test using forced harmonic motion of control surfaces including inertial coupling effects is conducted at the various conditions. The nonlinear aerodynamic effects are considered using a transonic small disturbance equation. A modal model obtained by a free vibration analysis is used for the structural model. The relations between the computed flutter boundary and the simulation results of the responses using the harmonic motions of control surfaces at various conditions are investigated.

• Coupled systems mechanics
• /
• 제1권3호
• /
• pp.219-234
• /
• 2012

Tuned vibration control in aeroelasticity of slender wood bridges is treated in present paper. The approach suggested takes into account multiple functions in aeroelastic analysis and flutter of slender wood bridges subjected to laminar and turbulent wind flow. Tuned vibration control approach is presented with application on actual bridge. Some results obtained are discussed.

• 한국군사과학기술학회지
• /
• 제20권1호
• /
• pp.148-157
• /
• 2017

Miniature guided-bullet is an advanced military technology of developing guided missile which is designed to hit a target precisely while having easily carriable miniature size. A key issue of developing such system involves size reduction of the original guided missile system, and this in turn arouses stiffness issue regarding small and thin sized control surface. In this study, procedures on how to calculate the critical flutter speed of special type of control surface with the change of its dimension or material property is arranged. During this procedure, design parameters related to critical flutter speed are abridged to help preliminary design of similar structure even faster than time-consuming, and cumbersome computer analysis.

• 한국항공우주학회지
• /
• 제30권6호
• /
• pp.92-100
• /
• 2002

본 연구에서는 천음속 미소교란 방정식을 이용하여 조종면의 강제 조화 운동을 고려한 전기체 형상에 대하여 천음속/초음속 비선형 플러터 특성을 파악할 수 있는 정밀 해석 시스템을 개발하였다. 본 시스템에는 충격파의 비선형 특성을 고려하기 위해 전산구조동역학, 유한요소해석 및 전산유체역학 기법을 동시에 연계하여 적용하는 연계시간 적분법을 도입하였다. 복잡한 전기체 형상에 대한 효과적인 격자생성을 위해 자체 자동격자 생성프로그램이 개발되었다. 천음속과 초음속 속도 영역에서 전기체 항공기에 대한 정적/동적 공탄성 특성을 고찰하였으며, 시간 영역에서 조종면 강제 조화운동에 대한 플러터 비행시험 시뮬레이션 결과들을 제시하였다.

• International Journal of Aeronautical and Space Sciences
• /
• 제14권1호
• /
• pp.46-57
• /
• 2013

Flutter stability and buffeting response have been the topics of most concern in the design state of long-span suspension bridges. Among approaches towards the aerodynamic stability, the aerodynamic-based control method which uses control surfaces to generate forces counteracting the unstable excitations has shown to be promising. This study focused on the mechanically controlled system using flaps; two flaps were attached on both sides of a bridge deck and were driven by the motions of the bridge deck. When the flaps moved, the overall cross section of the bridge deck containing these flaps was continuously changing. As a consequence, the aerodynamic forces also changed. The efficiency of the control was studied through the numerical simulation and experimental investigations. The values of quasi-steady forces, together with the experimental aerodynamic force coefficients, were proposed in the simulation. The results showed that the passive flap control can, with appropriate motion of the flaps, solve the aerodynamic instability. The efficiency of the flap control on the full span of a simple suspension bridge was also carried out. The mode-by-mode technique was applied for the investigation. The results revealed that the efficiency of the flap control relates to the mode number, the installed location of the flap, and the flap length.

• Journal of Mechanical Science and Technology
• /
• 제16권1호
• /
• pp.1-12
• /
• 2002

In this study, a passive suppression scheme for nonlinear flutter problem of composite panel, which is believed to be more reliable than the active control methods in practical operations, is proposed. This scheme utilizes a piezoelectric inductor-resistor series shunt circuit. The finite element equations of motion for an electromechanically coupled system is derived by applying the Hamilton\\`s principle. The aerodynamic theory adopted for the present study is based on the quasi-steady piston theory, and von-barman nonlinear strain-displacement relation is also applied. The passive suppression results for nonlinear panel flutter are obtained in the time domain using the Newmark-$\beta$ method. To achieve the best damping effect, optimal shape and location of fille piezoceramic (PZT) patches are determined by using genetic algorithms. The effects of passive suppression are investigated by employing in turn one shunt circuit and two independent shunt circuits. Feasibility studies show that two independent inductor-resistor shunt circuits suppresses flutter more effectively than a single shunt circuit. The results clearly demonstrate that the passive damping scheme that uses piezoelectric shunt circuit can effectively attenuate the flutter.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 춘계학술대회논문집
• /
• pp.303-310
• /
• 2002

The bending vibration and thermal flutter instability of spacecraft booms modeled as circular thin-walled beams of closed cross-section and subjected to thermal radiation loading is investigated in this paper. Thermally induced vibration response characteristics of a composite thin walled beam exhibiting the circumferantially uniform system(CUS) configuration are exploited in connection with the structural flapwise bending-lagwise bending coupling resulting from directional properties of fiber reinforced composite materials and from ply stacking sequence. The numerical simulations display deflection time-history as a function of the ply-angle of fibers of the composite materials, damping factor, incident angle of solar heat flux, as well as the boundary of the thermal flutter instability domain. The adaptive control are provided by a system of piezoelectric devices whose sensing and actuating functions are combined and that an bonded or embedded into the host structure.

• International Journal of Aeronautical and Space Sciences
• /
• 제8권1호
• /
• pp.140-147
• /
• 2007

Whenever the hinge axis of aircraft wing rotates, its stiffness varies. Also, there are nonlinearities in the connection of the actuator and the hinge axis, and it is necessary to inspect the coupled effects between the actuator dynamics and the hinge nonlinearity. Nonlinear aeroelastic characteristics are investigated by using the iterative V-g method. Time domain analyses are also performed by using Karpel's minimum state approximation technique. The doublet hybrid method(DHM) is used to calculate the unsteady aerodynamic forces in subsonic regions. Structural nonlinearity located in the load links of the actuator is assumed to be friction. The friction nonlinearity of an actuator is identified by using the describing function technique. The nonlinear flutter analyses have shown that the flutter characteristics significantly depends on the structural nonlinearity as well as the dynamic stiffness of an actuator. Therefore, the dynamic stiffness of an actuator as well as the nonlinear effect of hinge axis are important factors to determine the flutter stability.

• International Journal of Aeronautical and Space Sciences
• /
• 제6권1호
• /
• pp.17-26
• /
• 2005

An optical phase tracking technique for an extrinsic Fabry-Perot interferometer (EFPI) is proposed in order to overcome interferometric non-linearity. Basic idea is utilizing strain-rate information, which cannot be easily obtained from an EFPI sensor itself. The proposed phase tracking system consists of a patch-type EFPI sensor and a simple on-line phase tracking logic. The patch-type EFPI sensor comprises an EFPI and a piezoelectric patch. An EFPI sensor itself has non-linear behavior due to the interferometric characteristics, and a piezoelectric material has hysteresis. However, the composed patch-type EFPI sensor system overcomes the problems that can arise when they are used individually. The dynamic characteristics of the proposed phase tracking system were investigated, and then the patch-type EFPI sensor system was applied to the active suppression of flutter, dynamic aeroelastic instability, of a swept-back composite plate structure. The proposed system has effectively reduced the amplitude of the flutter mode, and increased flutter speed.