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Fei Q.,Nanjing Southeast University | Fei Q.,Jiangsu Provincial Key Laboratory of Engineering Mechanics | Zhou H.,Jiangsu Provincial Key Laboratory of Engineering Mechanics | Han X.,Nanjing Southeast University | And 2 more authors.
Engineering Failure Analysis

Structural stability is an vital aspect for structural health monitoring of transmission lines. This paper presents a novel method to evaluate the structural status of transmission line based on dynamic and stability analysis. A newly built long-span transmission tower-line system that crosses the Huaihe River in China with a span of 1083. m was studied as an example. Finite element model of the transmission tower-line system was constructed. Nonlinear buckling analysis for both the tower and tower-line system were performed to determine the critical wind loads. Dynamic properties of both the tower and tower-line system under different levels of wind loads were analyzed. Numerical results show the law that modal frequency of low order modes decreases when the wind velocity increases before the structural instability happens for both cases. Therefore, for the structural health monitoring of transmission lines, frequency decrease of low order mode is an useful indicator to predict the happening of structural instability. This conclusion could be taken as the reference in the design of structural health monitoring system for transmission lines. © 2011 Elsevier Ltd. Source

Zhang D.-H.,Nanjing Southeast University | Zhang D.-H.,Jiangsu Provincial Key Laboratory of Engineering Mechanics | Fei Q.-G.,Nanjing Southeast University | Fei Q.-G.,Jiangsu Provincial Key Laboratory of Engineering Mechanics | And 2 more authors.
Zhendong yu Chongji/Journal of Vibration and Shock

Bird shape and strike orientation are two very important factors affecting the accuracy of bird strike analysis. The realistic bird has a complex configuration and there are different bird types with different body shapes, so researchers often use simple configurations to model birds in bird strike events. There are four substitute bird models most-frequently employed in literatures, they are sphere, straight-ended cylinder, hemispherical-ended cylinder and ellipsoid. During a bird strike event, a bird can strike an airplane from its head, tail, abdomen or wings. These orientations have different effects on the response of an airplane part. Firstly, a realistic bird model was established to study the effect of its strike orientation. The results obtained by using the four substitute bird models were compared with those using a realistic bird model in order to determine the best substitute bird model for modeling the force exerted by a real bird with different strike orientations. It was shown that the striking orientation of a bird has a big influence on the impact force; the impact force obtained by striking from abdomen is the largest and the impact duration is the shortest while those obtained by striking from head and tail are relatively less; meanwhile, the kinetic energy loss of bird tends to be most and fastest for striking from abdomen, for strikings from wing and tail they are second, for striking from head it is the smallest; besides, for string from tail, a hemispherical-ended cylinder model has the best results and for striking from abdomen, an ellipsoid model striking from its long side is the best substitute model, while for striking from head and wing, no substitute models are better. © 2015, Chinese Vibration Engineering Society. All right reserved. Source

Lu T.,Nanjing Southeast University | Lu T.,Jiangsu Provincial Key Laboratory of Engineering Mechanics | Jiang D.,Nanjing Southeast University | Jiang D.,Jiangsu Provincial Key Laboratory of Engineering Mechanics | And 4 more authors.
Zhendong yu Chongji/Journal of Vibration and Shock

By using the large commercial finite element software NASTRAN, a method for elastic parameters identification of a 2.5D C/SiC composite plate based on modal test data was proposed here. An optimization problem was formulated with the model updating technique, its objective function was defined as the sum of squares of the discrepancies between measured and calculated modal frequencies, the initial values of the elastic parameters were obtained by adopting the stiffness averaging method making full use of the prior information of the material parameters. Finally, the accurate elastic parameters of the composite plate were identified through a iteration process by using the sensitivity analysis method. The accuracy of the first 1-4 modal frequencies of the C/SiC composite plate was significantly improved after identification, and the predictive accuracy of the 5-8 modal frequencies could also be guaranteed. Results showed that the proposed method can accurately identify the elastic parameters of the 2.5D C/SiC composite plate, and it can provide an effective reference for dynamic design and equivalently modeling of composite materials. Source

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