Damage Identification in Beam-like Structures Based on Wavelet Packet Using Minimum Number of Sensors

Modern and efficient methods focus on signal processing and have drawn researchers' attention to themselves in recent years. These methods mainly are Wavelet Packet transforms. The wavelet packet transform (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 time-frequency resolution. In this study, a damage detection index called 'Wavelet Packet Energy Rate Index (WPERI)', is proposed for the damage detection of beam structures and a beam-like structure was tested by two damage scenarios in the laboratory and then, the measured dynamic signals were decomposed into the wavelet packet components and the wavelet energy rate index was computed to indicate the structural damages. The advantage of this method is that it uses minimum number of sensors that makes this method practical and economical. In spite of that the noise was present for real data measurement; the identified damage patterns were comparable with the tests. This experimental study demonstrates that the WPT-based energy rate index is a good candidate index that is sensitive to location and intensity of damage.