Damage detection in structural elements through wave propagation using weighted RMS

Abstract

The paper presents an application of wave propagation for damage detection in an aluminum plate. The experimental investigation was conducted on an aluminum plate by generating the wave with Lead Zirconate Titanate (PZT) patches by function generator. Normal responses are measured with the Scanning Laser Doppler Vibrometer (SLDV). Eleven sine cycles modulated by hanning window with frequency of 5 kHz have been used as an excitation signal. Recorded signals were analyzed using the signal processing techniques developed for damage detection. The time signals recorded during measurement have been utilized to calculate the values of root mean square (RMS) response. It has turned out that the values of RMS differed significantly in damaged areas from the values calculated for the healthy ones. It is thus become possible to identify precisely the locations of damage over the entire measured surface. The magnitude of propagating wave decreases with travelled distance from the excitation point. This effect produces larger values of RMS near the excitation. To equalize RMS function in whole area time samples are multiplied by a weighting factor called weighted RMS function. The obtained results are presented in the form of scatter plots and numerical contour maps. It may be concluded that the proposed approach enables damage localization in a relatively fast and precise manner.