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Open AccessArticle

Attenuation of a Slow Subsonic A0 Mode Ultrasonic Guided Wave in Thin Plastic Films

Ultrasound Institute, Kaunas University of Technology, Baršausko str. 59, LT-51368 Kaunas, Lithuania
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Materials 2019, 12(10), 1648; https://doi.org/10.3390/ma12101648
Received: 25 April 2019 / Revised: 13 May 2019 / Accepted: 17 May 2019 / Published: 21 May 2019
(This article belongs to the Special Issue Non-destructive Inspection)
The ultrasonic testing technique using Lamb waves is widely used for the non-destructive testing and evaluation of various structures. For air-coupled excitation and the reception of A0 mode Lamb waves, leaky guided waves are usually exploited. However, at low frequencies (<100 kHz), the velocity of this mode in plastic and composite materials can become slower than the ultrasound velocity in air, and its propagation in films is accompanied only by an evanescent wave in air. To date, the information about the attenuation of the slow A0 mode is very contradictory. Therefore, the objective of this investigation was the measurement of the attenuation of the slow A0 mode in thin plastic films. The measurement of the attenuation of normal displacements of the film caused by a propagating slow A0 mode is discussed. The normal displacements of the film at different distances from the source were measured by a laser interferometer. In order to reduce diffraction errors, the measurement method based on the excitation of cylindrical but not plane waves was proposed. The slow A0 mode was excited in the polyvinylchloride film by a dry contact type ultrasonic transducer made of high-efficiency PMN-32%PT strip-like piezoelectric crystal. It was found that that the attenuation of the slow A0 mode in PVC film at the frequency of 44 kHz is 2 dB/cm. The obtained results can be useful for the development of quality control methods for plastic films. View Full-Text
Keywords: ultrasonic guided waves; subsonic A0 Lamb wave mode; attenuation of subsonic A0 mode ultrasonic guided waves; subsonic A0 Lamb wave mode; attenuation of subsonic A0 mode
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MDPI and ACS Style

Kažys, R.; Šliteris, R.; Mažeika, L.; Tumšys, O.; Žukauskas, E. Attenuation of a Slow Subsonic A0 Mode Ultrasonic Guided Wave in Thin Plastic Films. Materials 2019, 12, 1648.

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