An Improved Edge Based Smoothed Finite Elementadaptive Edge Based Smoothed Finite Element Method For The Analysis Of Mid To High Frequency Structural Acoustic Interaction Problems

With the rapid development of the modern industry,vibration and noise problems of diesel engines are becoming a serious problem.As the main noise source of a diesel engine,the vibration and noise analysis of thin-walled structures is an important research topic in diesel engine related industries and research.In order to reduce the cost and to shorten the research cycle,numerical simulation of engine noise and vibration is fast becoming a viable approach to replace the traditional diesel engine test.However,as noise and vibration of diesel engines typically have a broadband frequency,the existing numerical analysis methods such as finite element method(FEM)or boundary element method(BEM)has certain limitations.For instance,FEM can only be used to analyze low frequency vibration and noise problems,the numerical errors caused by "overly-stiff" elements increase as the analyzed frequency increases.The edgebased smoothed finite element method(ES-FEM)was proposed to overcome this problem,however,too many smoothed operations in ES-FEM in the analysis of mid to high frequency nosie and vibration problems will produce a "slightiy over-soft" phenomenon and reduce the computattional accuracy.Statistical energy analysis method is based on a statistical approach which is only applicable to high frequency analysis.On the other hand,a recently proposed numerical analysis technique termed as improved edge-based smoothed finite element method(IES-FEM)was found to be a vaiable approach for the analysis of mid-frequency three-dimensional acoustic problems.Thie method introduces a weight parameter to control the proportion of FEM and ES-FEM domains to moderately soften the stiffness matrix of the discrete system.However,the method has not been used in solving mid to high frequency frequency problems this far,and has not been applied in the structure domain.This thesis in view of the existing methods in the mid to high frequency structuralacoustic interaction analysis of problems in the large dispersion error,in the structure domain proposed adaptive edge-based smoothed finite element method(AES-FEM),and the IES-FEM has been extended to calculation of mid to high frequency acoustic cavity domain,a computational formula for the analysis of the mid to high frequency structuralacoustic interaction problem by the adaptive edge-based smoothed finite elementimprove edge-based smoothed finite element method(AES-FEM/IES-FEM)is derived.the stiffness of the coupling system is more close to the true structural-acoustic interaction model of stiffness,improve the calculation precision of the mid to high frequency structural-acoustic interaction analysis.In addition,an adaptive edge smoothed finite element method is proposed to select the optimal parameter ? based on the mesh size and frequency interval,? is the proportion of the FEM stiffness and ES-FEM stiffness in the calculation of structural domain stiffness.Compared with the FEM and ES-FEM,AESFEM improves the calculation accuracy,efficiency and convergence of structural domain stiffness.Finally,the proposed the AES-FEM/IES-FEM is used to analysis and predict the mid to high frequency structural-acustic interaction problems of a cylinder head cover with an enclosed chamber.Results from the numerical example show that the AES-FEM/IESFEM can appropriately soften the stiffness of the discrete system to make the calculated result more reasonable.