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Metals 2017, 7(12), 552; https://doi.org/10.3390/met7120552

A Numerical Study on the Excitation of Guided Waves in Rectangular Plates Using Multiple Point Sources

1
Department of Mechanical, Aerospace and Civil Engineering, Brunel University London, Uxbridge, Middlesex UB8 3PH, UK
2
National Structural Integrity Research Centre, TWI Ltd, Cambridge CB21 6AL, UK
3
Department of Engineering Science, University of Greenwich, Chatham ME4 4TB, UK
*
Authors to whom correspondence should be addressed.
Received: 10 October 2017 / Revised: 27 November 2017 / Accepted: 29 November 2017 / Published: 8 December 2017
(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)
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Abstract

Ultrasonic guided waves are widely used to inspect and monitor the structural integrity of plates and plate-like structures, such as ship hulls and large storage-tank floors. Recently, ultrasonic guided waves have also been used to remove ice and fouling from ship hulls, wind-turbine blades and aeroplane wings. In these applications, the strength of the sound source must be high for scanning a large area, or to break the bond between ice, fouling and plate substrate. More than one transducer may be used to achieve maximum sound power output. However, multiple sources can interact with each other, and form a sound field in the structure with local constructive and destructive regions. Destructive regions are weak regions and shall be avoided. When multiple transducers are used it is important that they are arranged in a particular way so that the desired wave modes can be excited to cover the whole structure. The objective of this paper is to provide a theoretical basis for generating particular wave mode patterns in finite-width rectangular plates whose length is assumed to be infinitely long with respect to its width and thickness. The wave modes have displacements in both width and thickness directions, and are thus different from the classical Lamb-type wave modes. A two-dimensional semi-analytical finite element (SAFE) method was used to study dispersion characteristics and mode shapes in the plate up to ultrasonic frequencies. The modal analysis provided information on the generation of modes suitable for a particular application. The number of point sources and direction of loading for the excitation of a few representative modes was investigated. Based on the SAFE analysis, a standard finite element modelling package, Abaqus, was used to excite the designed modes in a three-dimensional plate. The generated wave patterns in Abaqus were then compared with mode shapes predicted in the SAFE model. Good agreement was observed between the intended modes calculated in SAFE and the actual, excited modes in Abaqus. View Full-Text
Keywords: SAFE; rectangular plate; guided waves; modal excitation SAFE; rectangular plate; guided waves; modal excitation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Duan, W.; Niu, X.; Gan, T.-H.; Kanfoud, J.; Chen, H.-P. A Numerical Study on the Excitation of Guided Waves in Rectangular Plates Using Multiple Point Sources. Metals 2017, 7, 552.

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