J0402-2-5 Noncontact measurement of wall thinning of a hollow cylinder using circumferential Lamb waves generated and detected by a pair of air-coupled ultrasonic transducers.

Abstract

A novel method for noncontact measurement of wall thinning of a hollow cylinder using circumferential Lamb waves generated and detected by a pair of air-coupled ultrasonic transducers was proposed. In the method, wave-packets of multiple-turnaround C-Lamb wave are superposed and interfere themselves when the number of tone-burst cycle takes large enough. An amplitude of the superposed signal is determined by the angular wave number due to both the wall thickness and frequency. In the verifications, the wall thinnings were determined within the maximum error of 6 μm in comparison to the theoretical estimations.