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Dynamic Analysis of Structure with Modal Properties Identification of Its Substructures Using Component Mode Synthesis

Momeni Massoule, Hassan | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40952 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Hosseini Kordkheili, Ali
  7. Abstract:
  8. The substructuring method provides a suitable tool to conduct modal analysis of large and complicated structures. In this method the original structure is decomposed into simpler and smaller substructures, and the dynamic properties of the resulting substructures are first evaluated independently. The original structure’s dynamic properties are subsequently estimated by coupling the substructures’ dynamic results. In this procedure, the boundary conditions need to be imposed in such a way that the overall behaviour of the original structure is properly represented. Substructuring method can be used in different types of dynamic analysis. The focus of this paper is on the modal type of substructuring, which is referred to as component mode synthesis (CMS). Although with the continuous trend of increasing computational processing power it is now possible to simulate very large structures, the substructuring method is still considered to be an efficient method which can complement experimental modal analysis procedures in which direct modal results from test data cannot be obtained. In the next, it is shown that the Craig-Chung’s proposed approximation function for higher frequency modes does not compare well with the exact function. This inconsistency motivated to develop a new approach. Therefore, in this thesis a modal coupling procedure is developed to improve residual modal effects based on experimentally-generated data. In this procedure in order to re-express the dynamic residuals, all frequency dependent terms of the Mac Lauren series in Craig-Chung’s proposed method are replaced by a general compatible function which include the neglected higher order terms. However, this function no longer appears in final equation of motion. Results for the discrete, continues and experimentally models presented to verify the procedure as well as to show the capabilities of the proposed method.
  9. Keywords:
  10. Substructures ; Coupling ; Experimental Method ; Frequency Response ; Structure Decomposition ; Modal Properties ; Components Mode Synthesis

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