Damage detection in beam-like structure based on wavelet packet

Abstract

Modern and efficient methods of structural damage detection focus on signal processing and have drawn researchers’ attention in recent years. These methods mainly are based on Wavelet Packet Transforms (WPT). The WPT is an extension of the Wavelet Transform, which provides a complete level-by-level decomposition of signal. The wavelet packets are alternative bases formed by the linear combinations of the usual wavelet functions. Therefore, the WPT enables the extraction of features from the signals that combine the stationary and non-stationary characteristics with an arbitrary timefrequency resolution. In this study, a damage detection index called Wavelet Packet Energy Rate Index (WPERI) is proposed for the diagnosing of damage in beam-like structures with two different damage scenarios. For this purpose, the measured vibration signals of an experimental model of the beam were decomposed into the wavelet packet components and the wavelet energy rate index which were computed to indicate the structural damages. It will be shown that, the advantage of this method is applying minimum number of sensors which therefore makes this method practical and economical in comparison with other methods, for example Continues Wavelet Transform and Discrete Wavelet Transform. Also, in spite of low signal to noise ratio, the damage location and intensity will be identified correctly.