Patent ID: 8225665
Filing Date: 2012-07-24
Classification: G01B,G01H,G01N

Abstract:
1. A method of measuring an amount of loss of material thickness from a solid structure operable to support propagation of acoustic waves therein, said method comprising the steps of (a) placing a plurality of acoustic transducers in contact with a surface of the solid structure; (b) transmitting an acoustic signal from at least one of the plurality of acoustic transducers into a wall of said structure, and receiving the transmitted acoustic signal at a plurality of said transducers after travelling a distance within the solid structure; (c) collecting signals from said plurality of said transducers in a processing unit; (d) analyzing and comparing the received signals generated in step (b) and/or with results from earlier corresponding measurements, wherein the signal received by the receiving acoustic transducer and analyzed in the processing unit is a fundamental asymmetric (flexural) mode generated by the one or more transmitting acoustic transducers, wherein signal components corresponding to said flexural mode are isolated from signal components of other modes by using a gating technique applied to the received signals and wherein the processing unit analyzes a group velocity and a phase velocity of said flexural mode in a range wherein a group velocity of said flexural mode is approximately constant, said processing unit computing from a change in the said phase velocity a change in a true thickness of the solid structure; and (e) computing a degree of loss of material thickness from said solid structure from an analysis executed in step (d).