Research Of Mode Identification And Damage Detection Based On Wavelet Transformation

Wavelet transformation is a time-scale and time-frequency signal analysis. It has many desirable properties, and has been widely applied in many fields.In this thesis, theory of wavelet transform is introduced into area of modal identification and damage detection, and two new methods for modal identification and damage detection based on wavelet transformation are proposed.The main work of this thesis includes two aspects:(1) Modal identification based on wavelet transformationA equation of hard threshold wavelet de-noise is reasoned out from MSE function. Through the equation, free response can be gotten from random response. At last, ITD method based on free acceleration response is used to identify mode parameters, frequencies and modal.(2) Damage detection based on wavelet transformationUsing the principle of time-frequency analysis based on orthonormal discrete wavelet transformation, it can detect damage by analyzing how the frequency content of observation signal changes with time.In order to realize the up theories, computer programs are composed in Matlab6.1 because of its strong abilities of scientific calculation. And calculation results of some models show that the methods are effectual.