Examining the Function of Wavelet Packet Transform (WPT) and Continues Wavelet Transform (CWT) in Recognizing the Crack Specification

Modern and efficient methods focus on signal analysis and have drawn researchers' attention to it in recent years. These methods mainly include Continuous Wavelet and Wavelet Packet transforms. The main advantage of the application of these Wavelets is their ability to analyze the signal position in different times and places. The frequency decomposition of this transform in location with high frequencies is very poor. Wavelet packet transform is more advanced form of continuous wavelet and can make a perfect level by level resolution for each signal. However, very few studies have been done in this field. In the present study, first there was an attempt to do a modal analysis on the structure by the ANSYS finite elements software, then using MATLAB, the wavelet was investigated through a continuous wavelet analysis. Finally, the results were displayed in 2-D location-coefficient figures. In the second form, transient dynamic analysis was done on the structure and to find out the characteristics of the crack, wavelet packet energy rate index was suggested. The results revealed that suggested index in the second form is both practical and applicable.