Research On Finite Element Model Modification Based On Frequency Response Function

At present,structural dynamics modeling at home and abroad can generally be divided into two forms: one is the experimental model,which has the advantage of conforming to the real situation,but it is limited to small and low-order structures,and the experimental modal is often not complete and has the noise effect that is difficult to ignore,so its cost is relatively high for large and complex structures;the other is the finite element method.The advantage of this model is that it has low investment and easy to correct,but it will cause modeling deviation.Therefore,combining the advantages of two kinds of modeling methods,model updating technology has gradually become an important research topic in the field of structural dynamics.Through literature review,this paper draws the following main problems and research hotspots in the current model updating technology: 1)the deviation of experimental test and modal analysis is hard to neglect,and has a great impact on the results of the correction;2)the matching problem of degree of freedom is introduced by the incompleteness of measured modes,and the general model condensation method often leads to the ambiguity of matrix meaning;3)there are many problems at present.The modification method is effective for the application of small or ordinary structures,but it has great limitations for large or special structures.In order to solve the above problems,a finite element model updating method based on frequency response function is proposed in this paper.Firstly,a model updating method which does not depend on sensitivity analysis is deduced and the modal expansion method is extended.Then,an extended iterative model updating method based on frequency response function is proposed by means of iteration theory.Finally,by modifying the riveted plate structure model,it is proved that this method has a high precision in correcting the modeling deviation of the joints often seen in engineering,and can effectively identify the place where the modeling deviation occurs and the size of the deviation.In the first chapter,the engineering background and theoretical meaning of the research which has been introduced,the research situation and progress of model updating technology at home and abroad are introduced,and the main research contents and the arrangement of each chapter are described.In the second chapter,the basic idea and analysis process of finite element method are introduced,and then several structural damage identification methods are elaborated,which makes sufficient preparations for the later introduction of finite element model updating technology.In the third chapter,it introduces the concepts and common methods of DOF matching and correlation analysis,and introduces the model updating technology based on frequency response function.Then,an extended iteration updating method based on frequency response function is proposed by linking the DOF expansion mode with the model updating technology.In the fourth chapter,referring to the riveted plate structure example,the structure with modeling deviation at the joint is modified by the method proposed in this paper.Then the feasibility of this method is analyzed.Finally,the modified results of IRS model condensation method are compared.The fifth chapter is the summary and Prospect of the full text work,summarizes the main research work done in this paper and the countermeasures to the existing problems,and also makes a prospect of the direction and content of future research.