报告人：NatasaTrisovic,教授，贝尔格莱德大学

邀请人：李伟

报告时间：2022年5月31日下午14:00-18:00

腾讯会议ID：185 625 358

报告人简介(in Chinese)塞尔维亚贝尔格莱德大学机械工程学院教授，CEEPUS(Central European Exchange Program for University Studies)计划成员，捷克工程大学力学工程学院客座教授（2009），波西尼亚巴尼亚卢卡大学力学工程学院客座教授（2010，2012），斯洛伐克科技大学力学工程学院客座教授，美国莱斯大学MEMS学院客座教授（2012-2014），EUREKA计划和ESPRIT项目成员，塞尔维亚结构完整性与生命协会成员，塞尔维亚力学学会秘书长，研究方向为理论与应用力学，主要集中于对结构系统振动疲劳可靠性的数值研究。发表学术论文60多篇，参加项目10余项。

报告题目1：AN EXAMPLE FOR STRUCTURAL DYNAMIC MODIFICATION

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

报告题目2：MODAL SENSITIVITY ANALYSIS. THEORETICAL BACKGROUND

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

报告题目3：Reanalysis 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

报告题目4：ITERATIVE METHODS FOR EIGENSENSITIVITY ANALYSIS - A REVIEW

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