Damage size estimation by the continuous wavelet ridge analysis of dispersive bending waves in a beam

The damage assessment in a structure consists of the estimation of its location and extent. The objective of this work is to assess the damage size using the ratio of the incident wave toward and the reflected wave from the damage. Since waves to be analyzed are of the bending type, the measured signals are highly dispersive; it is almost impossible to estimate the magnitude ratio alone in the time domain. So, we propose to use the continuous wavelet transform of the measured signal and perform the ridge analysis in order to extract accurately the magnitudes of the incident and the reflected waves for a range of frequencies of interest from the measured wave signal. Wave experiments are conduced in a slender cylindrical beam and the magnetostrictive sensors are used to capture the bending waves in the beam. To correlate the magnitude ratio with the damage size, we employ the Timoshenko beam theory. Several experiments are conducted to check the effectiveness of the proposed wavelet-based method.