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      報告時間 2022年5月31日下午14:00-18:00 報告地點 騰訊會議ID:185 625 358
      報告人 NatasaTrisovic





      騰訊會議ID:185 625 358

      報告人簡介(in Chinese)塞爾維亞貝爾格萊德大學機械工程學院教授,CEEPUS(Central European Exchange Program for University Studies)計劃成員,捷克工程大學力學工程學院客座教授(2009),波西尼亞巴尼亞盧卡大學力學工程學院客座教授(2010,2012),斯洛伐克科技大學力學工程學院客座教授,美國萊斯大學MEMS學院客座教授(2012-2014),EUREKA計劃和ESPRIT項目成員,塞爾維亞結構完整性與生命協會成員,塞爾維亞力學學會秘書長,研究方向為理論與應用力學,主要集中于對結構系統振動疲勞可靠性的數值研究。發表學術論文60多篇,參加項目10余項。


      Abstract:Structural dynamic modification implies the incorporation, into an existing model, of new information gained either from experimental testing or some other source, which questions or improves the accuracy of the model. This paper deals with improving of dynamic charasteristics of tube collector (protection pipe of conductors of transformer) of the ring cross section. It is shown how change of conditions of support can improve dynamic characteristics of structure. Distribution of potential and kinetic energy in every finite element is used for analysis. In this study it is shown that structural dynamic modification is important in structural reanalysis.

      Key words: structural dynamics modification, eigenvalues, potential and kinetic energy


      Abstract:This paper presented a review of the modal sensitivity analysis. It is becoming widely accepted that sensitivity analysis can be a valuable tool in structural reanalysis where (enough of) the modal properties are known, either through theoretical or experimental analysis. Modal sensitivities are the derivatives of the modal properties of a dynamic system with respect to chosen structural variables. In the modal analysis literature there have been two primary applications. In the first case sensitivity data are used solely as a qualitative indicator of the location and approximate scale of design changes to achieve a desired change in structural properties. The consequences of candidate design changes would then be evaluated using exact methods. The second strategy uses the design sensitivities directly to predict the effect of proposed structural changes. A variational approach will be discussed here. NR 10 pt)

      Keywords: eigenvalues, eigenvectors, sensitivity analysis, FEM

      報告題目3Reanalysis in structural dynamics

      Abstract.Structural Dynamic Modification is a term used in Modal Analysis. In the wider Computer Aided Engineering Community, for example in Finite Element Analysis, the corresponding methods are often described as Reanalysis. Due to increasing demands for better performance and use of lighter structures in modern engineering (machinery an civil engineering), vibration engineers must have better testing and analysis tools than in the past. To solve vibration problems in a structure, the dynamic behaviour of the structure needs to be understood and an accurate dynamic model needs to be developed. Analysis (or predictions) of the dynamic behaviour of the structure with such a model can reduce development cost and test effort. There are two ways of achieving a suitable dynamic model of structure: by theoretical prediction and by experimental measurement, respectively. The initial design concept is likely to give rise to a variety of design options each of which will be evaluated against the requirements of the product specification. Often at this stage a prototype or series of prototypes will be constructed and their properties compared with the design idealisation. Reanalysis implies the incorporation, into an existing model, of new information gained either from experimental testing or some other source, which questions or improves the accuracy of the model. The following topics are addressed in this paper: how the frequency considerations influence the structural design, eigensensitivity, and constraint approximations, and how different types of optimization algorithms are used in solving the frequency problem. The optimal design of structures with frequency constraints is extremely useful in manipulating the dynamic characteristics in a variety ways.

      Key words: structural dynamics, reanalysis, eigenvalues, sensitivity


      Abstract.The dynamic behavior of a structural system is characterized by its eigendata. The partial derivatives of eigenvalues and eigenvectors of mechanical system with respect to the design parameters have attracted extensive attention for the last four decades because of their various applications, such as optimal dynamic design, machinery failure diagnostic, parameter identification, model modification and automative control. A more general problem of structural dynamic analysis has three important aspects. Firstly, the observed physical structure is represented by initial finite element model. Modeling is based on numerous idealizing approximations within an exaggerated elaboration of details, which in essence does not significantly improve the accuracy of output data, especially having available powerful computers and appropriate software packages. Optimal alternative is to have the possibility of verifying outputted data that were measured on a prototype or real structure. Secondly, the dynamic characteristics of construction under reanalysis are analyzed. What is basically observed are eigenvalues and main forms of oscillations as characteristic variables that can invoke inadequate actual dynamic behavior. Thirdly, on the basis of the analysis of actual dynamic behavior, modification steps are proposed after which a modified model is obtained. Having in mind that mechanical structures are most often very complex, the most convenient modification steps are not easily obtained. The most straightforward approach for calculating the derivatives is the finite difference method. There mainly exist three categories in the literature: the modal method, the direct method and the iterative method. Several methods for the computation of eigenvector derivatives is analyzed with emphasis on the iterative methods.

      Key words:eigensensitivity, structural optimization, repeated frequencies

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