Patent ID: 6925881
Filing Date: 2005-08-09
Classification: G01N

Abstract:
1. A method of using long range guided wave inspection techniques to detect geometric irregularities in a cylindrical shell structure, comprising the steps of: generating a first long range wave from a first probe at a first probe position along the cylindrical shell, wherein the first long range wave travels substantially in one direction from the probe along a length of the structure; acquiring a first data set representing reflection signals reflected from an irregularity to the first probe; generating a second long range wave from a second probe at a second probe position along the cylindrical shell having a known separation from the first probe position, wherein the second long range wave travels in the same direction relative to the first long range wave; acquiring a second data set representing reflection signals reflected from the irregularity to the second probe position; wherein the first probe and the second probe are external to the structure; wherein the first long range wave and the second long range wave are substantially of a single wave mode of a fixed order, both propagated in a single direction relative to each other; identifying peak signal values in the first data set and in the second data set, thereby obtaining a first set of peak signal values and a second set of peak signal values; associating each peak signal value with an occurrence time; time-shifting one set of peak signal values by an amount equal to the roundtrip time of the first long range wave over the distance between the first probe and the second probe; determining a coincidence in time of values in the shifted set of peak signal values and values in the unshifted set of peak signal values; and interpreting coincident values as corresponding to an irregularity in the structure.