Dept. of Mech. Eng., Tennessee Technol. Univ., Cookeville, TN 38505
With the increasing demand for safety and reliability on structures and mechanical systems, damage detection by nondestructive evaluation (NDE) methods has attracted considerable attention from many researchers. This paper presents a new method for damage detection based on time-frequency analysis of transient bending wave propagation. The wavelet transform and short-time Fourier transform are applied to the analysis of impulse-induced bending wave propagation in a cracked finite beam. The time-frequency representation resulting from the transformation of measured acceleration response is utilized to identify the reflection part of the transient bending wave by a crack and to determine its reflection coefficient and the arrival time (from the location of the crack to the transducer position) for different frequency components contained in the transient bending wave. The quantity of the crack is evaluated from the reflection coefficient, and its location is estimated from the arrival time. To demonstrate the effectiveness of the presented method in quantifying and locating cracks, a cantilever beam and a free--free beam with the same crack are investigated.