Ultrasound imaging of immersed plates using high-order Lamb modes at their low attenuation frequency bands

•Characterization and selection of low attenuation Lamb modes in immersed plates.•Methodology for imaging using phased-array and Lamb waves in immersed plates.•Use of higher order Lamb modes for defect detection in immersed structures.•A video showing the attenuation effect can be seen at https://yo...

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Published inMechanical systems and signal processing Vol. 96; pp. 321 - 332
Main Authors Takiy, Aline E., Kitano, Cláudio, Higuti, Ricardo T., Granja, Silvio C.G., Prado, Vander T., Elvira, Luis, Martínez-Graullera, Oscar
Format Journal Article
LanguageEnglish
Published Berlin Elsevier Ltd 01.11.2017
Elsevier BV
Subjects
Aluminum
Attenuation
Band theory
Defects
Dynamic focusing
Frequencies
Imaging
Immersed plate
Lamb waves
Leaky waves
Metal plates
Propagation modes
Ultrasonic array
Ultrasonic imaging
Ultrasonic testing
Ultrasound
Lamb waves
Attenuation
Immersed plate
Ultrasonic array
Imaging
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Summary:•Characterization and selection of low attenuation Lamb modes in immersed plates.•Methodology for imaging using phased-array and Lamb waves in immersed plates.•Use of higher order Lamb modes for defect detection in immersed structures.•A video showing the attenuation effect can be seen at https://youtu.be/EkbrzY3MHMo. This paper focuses on the use of a Lamb wave-based methodology for ultrasound imaging of immersed plate structures. In these cases Lamb waves can be strongly attenuated due to leaky waves and viscous losses in the liquid, but there are low attenuation frequency bands that may be used for NDT applications. Experimental measurements were conducted to validate the existence of these low attenuation frequency bands, which were also theoretically predicted for some propagation modes, between the frequencies-thickness products of 0.5MHzmm and 9.0MHzmm. Using a 5MHz linear-array and phased-array techniques, A1 and S1 modes are used to obtain images of an immersed aluminum plate with artificial defects. The signals are post-processed in order to select the desired propagation mode and to obtain an image with dynamic focusing in reception. While the A1 mode is strongly attenuated, the S1 mode, at 3.4MHzmm, can be used to detect and localize defects in the immersed plate.
ISSN:0888-3270
1096-1216
DOI:10.1016/j.ymssp.2017.04.021