The Study Of Dynamic Characteristic Of Aluminum Honeycomb Sandwich Structure Based On Nonlinear Method In Frequency Domain

The identification approaches of nonlinear systems, especially the approaches in frequency domain, are discussed based on investigation of related articles. The frequency results are far more significant and easy to calculate and explain than the ones in time domain. The honeycomb sandwich structure has been widely utilized in engineering field nowadays. However, due to the complex construction of this structure, it seems not quite easy to describe its dynamic characteristic clearly and completely via conventional methods. The purpose of this thesis is to analyze and identify the dynamic characteristic of honeycomb sandwich structure based on nonlinear methods to stochastic data in frequency domain.First, the methods and procedures of general three orders nonlinear identification are summarized and the results are frequency functions described by basic and high order spectral density functions and frequency response functions.Secondly, the characteristics and procedures of before linear systems and after linear systems are discussed. It is found that the high order frequency response functions of these systems will become single frequency variable functions.Finally, the nonlinear identification method to stochastic data in frequency domain is used to analyze and identify the nonlinear characteristic of some multifunctional electrical case with honeycomb sandwich structure. This system is fitted separately by six models of before linear system and after linear system and then the optimal model with minimum relative error is chosen to describe the system. This method can not only analyze the system characteristic accurately, but also get the order and nonlinear frequency response function in every order, therefore realizes the nonlinear system identification of the case under study. The causes of nonlinear are also discussed later based on these results from the view of structure material and form.To identify the dynamic characteristic of honeycomb sandwich structure via method mentioned in this thesis can be valuable in practice for further design,...