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排序方式: 共有137条查询结果,搜索用时 916 毫秒
31.
The prediction of flutter instability is of major concern for design of flexible structures. This necessitates the identification of aeroelastic parameters, known as flutter derivatives from wind tunnel experiments. The extraction of flutter derivatives becomes more challenging when the number of degrees of freedom (DOF) increases from two to three. Since the work in the field of identifying all 18 flutter derivatives has been limited, it has motivated the development of a new system identification method (iterative least squares method or ILS method) to efficiently extract the flutter derivatives using a section model suspended by a three-DOF elastic suspension system. The accuracy of a particular flutter derivative was determined by comparing the results obtained from all possible DOF combinations. 相似文献
32.
Henrik Ditlev Nissen Ole Jannerup 《Journal of Wind Engineering & Industrial Aerodynamics》2004,92(10):829-847
The paper describes the addition of actively controlled aerodynamic appendages (flaps) attached along the length of the bridge deck to dampen wind-induced oscillations in long suspension bridges. A novel approach using control systems methods for the analysis of dynamic stability is presented. In order to make use of control analysis and design techniques, a linear model of the structural and aerodynamic motion around equilibrium is developed. The model is validated through comparison with finite element calculations and wind tunnel experimental data on the Great Belt East Bridge in Denmark. The developed active control scheme is local in that the flap control signal at a given longitudinal position along the bridge only depends on local motion measurements. The analysis makes use of the Nyquist stability criteria and an analysis of the sensitivity function for stability analysis. The analysis shows that the critical wind speed for flutter instability and divergence is increased substantially by active control. 相似文献
33.
Jae-On Kim Kee-Seok Lee Jin-Woo Lee 《Journal of Mechanical Science and Technology》2008,22(12):2386-2392
Problems related to the stability and behavior of a cantilevered beam with a tip mass on an elastic foundation and subjected
to a distributed follower force are addressed. The stability of a beam partially attached to an elastic foundation is also
considered. The dynamic stability of a beam subjected to a distributed follower force is formulated by using finite element
method to get a general eigenvalue problem. The influence of the modulus on the elastic foundation and the ratio of the cantilevered
beam’s mass to the tip mass on the critical flutter are investigated. Finally, the stability of the cantilevered beam is found
to depend on both the modulus of the elastic foundation and the ratio of the cantilevered beam’s mass to the tip mass.
This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo
Dr. Jae-On Kim is now adjunct professor of Hanbat National University and president of Shinwall architectural & const. Co. Ltd. He has an
excellent background in the architecural structure design and analysis.
Dr. Kee-Seok Lee was educated at the Chungnam National University in Korea Ph.D. degree in mechanical engineering. For 10 years, he has a
researcher in the field of mechanical design and control. Especially, he has an excellent background in the vibration control.
At university, he has designend and established the control method for measuring Cam Profile without contact and air-bearing
control method under disturbances. He is an author of 10 papers.
Dr. Jin-Woo Lee was educated at the Kyushu institute of Technology in JapanPh.D. degree in of life-science and system engineering(Dec., 2006).
He is a senior researcher at the steel solution research group of POSCO. 相似文献
34.
Quanshun Ding Ledong Zhu Haifan Xiang 《Journal of Wind Engineering & Industrial Aerodynamics》2010,98(12):911-918
The flutter derivatives of bridge decks can be determined in a unique manner on condition that the complex modal parameters of the system at one reduced frequency are obtained. Based on the idea, a new method of identifying the flutter derivatives of bridge decks is proposed and it can overcome some shortcoming of the existing method and extend the applicability of the free vibration technique at high wind velocity. The identified results have agreements with the target ones of an ideal thin-plate section and those of a thin-plate section measured by the forced vibration technique. The proposed method is reliable and effective to extract the flutter derivatives from coupled free vibration. 相似文献
35.
In this study, the instability of delaminated cross-ply thin laminated cylindrical shells and panels when subjected to supersonic flow parallel to its length edge is investigated. The delamination is parallel to the shell reference and it extends along the entire length of the cylindrical shell. The Love’s shell theory and Von-Karman–Donnell type of kinematic relations along with first-order potential theory have been employed to construct the aeroelastic equations of motion. The effects of several parameters such as length to radius ratio, delamination position, size and thickness on the critical values are discussed in the details. The results indicate that the presence of delamination reduced the overall stiffness of the structure and thereby decreases the flutter critical boundaries. 相似文献
36.
37.
从频谱分析理论和机床颤振的特性出发,在大量试验基础上分析了车削加工系统从平稳切削,经过渡过程到颤振中各种颤振信号之间的互谱特性。着重分析了互谱密度函数中的实部(共谱)、虚部(重谱)以及主频带上的相位差在颤振发展过程中的特征变化。并在此基础上提出了一种新的机床颤振预兆判别的特征量。 相似文献
38.
J. Dario Aristizabal-Ochoa 《Canadian Metallurgical Quarterly》2005,131(5):473-484
Stability criteria that evaluate the effects of combined conservative and nonconservative end axial forces on the elastic divergence buckling load of prismatic beam-columns with semirigid connections is presented using the classic static equilibrium method. The proposed method and stability equations follow the same format and classification of ideal beam-columns under gravity loads presented previously by Aristizabal-Ochoa in 1996 and 1997. Criterion is also given to determine the minimum lateral bracing required by beam-columns with semirigid connections to achieve “braced” buckling (i.e., with sidesway inhibited). Analytical results obtained from three cases of cantilever columns presented in this paper indicate that: (1) the proposed method captures the limit on the range of applicability of the Euler’s method in the stability analysis of beam-columns subjected to simultaneous combinations of conservative and nonconservative loads. The static method as proposed herein can give the correct solution to the stability of beam-columns within a wide range of combinations of conservative and nonconservative axial loads without the need to investigate their small oscillation behavior about the equilibrium position; and (2) dynamic instability or flutter starts to take place when the static critical loads corresponding to the first and second mode of buckling of the column become identical to each other. “Flutter” in these examples is caused by the presence of nonconservative axial forces (tension or compression) and the softening of both the flexural restraints and the lateral bracing. In addition, the “transition” from static instability (with sidesway and critical zero frequency) to dynamic instability (with no sidesway or purely imaginary sidesway frequencies) was determined using static equilibrium. It was found also that the static critical load under braced conditions (i.e., with sidesway inhibited) is the upper bound of the dynamic buckling load of a cantilever column under nonconservative compressive forces. Analytical studies indicate the buckling load of a beam-column is not only a function of the degrees of fixity (ρa and ρb), but also of the types and relative intensities of the applied end forces (Pci and Pfj), their application parameters (ci, ηj, and ξj), and the lateral bracing provided by other members (SΔ). 相似文献
39.
40.
A high precision high order triangular plate element is developed for the linear flutter analysis of thermally buckled composite sandwich plates. Due to uneven thermal expansion in the two local material directions, the buckling mode of the plate may be shifted from one pattern to another for certain fiber orientation or plate aspect ratio as the aerodynamic pressure is present. This buckle pattern change alters the frequencies and modes of the plate and that in turn changes the flutter coalescent modes. Numerical results show that temperature has a destabilizing effect on the flutter boundary but the aerodynamic pressure has a stabilizing effect on the buckling boundary. 相似文献