Specimen-agnostic guided wave inspection using recursive feedback

Abstract

ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract-Lamb waves, a configuration of guided waves are often applied to the inspection of plate like structures. Their complex, multi-modal nature makes them well suited to the inspection of different defects. Control over their propagation direction allows the engineer to increase inspection distance and prospectively locate the defect. Schemes already exist, but they require knowledge of material and its dispersion curves. If the material composition is not known, or external factors are effecting its speed of sound then these schemes may not be appropriate. The recursive feedback algorithm can be used to enhance guided waves in a single direction without a-priori knowledge. In recursive feedback, a guided wave is generated using the first element of an array transducer. Over several subsequent iterations, this guided wave is reinforced by retransmitting recorded out of plane displacements. In this work, recursive feedback has been applied to two inspection problems; a contaminated kissing bond and a plate with a defect. With the kissing bond, it is shown that the the contamination can be identified as the A0 mode of generated waves are absorbed. In the defective plate, the defect direction is identified by a 10 dB increase in reflected energy when the guided waves are enhanced in one direction.

An Adaptive Array Excitation Scheme for the Unidirectional Enhancement of Guided Waves

“…The direction of propagation can be controlled without a priori knowledge of the material's parameters. This paper builds on existing work [48], [49] with the addition of an improved signal processing chain that has facilitated experimental validation.…”

Excitation and acquisition of cranial guided waves using a concave array transducer

“…15 Consisting of multiple modes of oscillation, guided waves (GW) are complex but well understood. [16][17][18][19] They form when a thin structure is insonified with a wavelength greater than its thickness. There are an infinite number of modes and each mode's attenuation, group and phase velocity changes independently with frequency.…”