Crack characterization using guided circumferential waves

This paper examines the propagation of guided circumferential waves in a ho llow isotropic cylinder that contains a crack, with the goal of using these guided waves to both locate and size the crack. The crack is sized using a modified Auld's formula, which relates the crack's length to a reflected e nergy coefficient. The crack is then located by operating on the backscatte red signal with a time-frequency digital signal processing (DSP) technique, and then comparing these results to those obtained if the cylinder is perf ect. The guided circumferential waves are generated with a commercial finit e element method (FEM) code. One objective of this work is to demonstrate t he effectiveness of using sophisticated DSP techniques to describe the effe ct of scattering on dispersive waves, showing it is possible to characteriz e cracks systematically and accurately by quantifying this scattering effec t. The results show that the need for high frequency signals to detect smal l cracks is significantly decreased by using these techniques. (C) 2001 Aco ustical Society of America.