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Airborne ultrasonic systems for one-sided inspection using thermoacoustic transmitters

  • Airborne ultrasonic inspection is performed in through transmission, where the test piece (e.g. adhesive joint or polymer-based composite plate) is placed between the transmitter and the receiver. However, many structures with difficult shapes allow only one-sided inspection. The strong reflection of the signal from the surface overshadows the signals from the inside, so that broadband pulses are required. Thermoacoustic transmission, where the thermal energy of an electrically heated electrode is transformed into the acoustic energy of an ultrasonic wave, opens the possibility to excite broadband pulses and thus to inspect objects with one-sided access. We present various thermoacoustic transducers consisting of an electrically conductive film on a solid substrate. The first type of transducer is a transmitter with an indium-tin-oxide electrode on a glass substrate combined with a laser Doppler vibrometer as a receiver. The second type of transducer combines thermoacousticAirborne ultrasonic inspection is performed in through transmission, where the test piece (e.g. adhesive joint or polymer-based composite plate) is placed between the transmitter and the receiver. However, many structures with difficult shapes allow only one-sided inspection. The strong reflection of the signal from the surface overshadows the signals from the inside, so that broadband pulses are required. Thermoacoustic transmission, where the thermal energy of an electrically heated electrode is transformed into the acoustic energy of an ultrasonic wave, opens the possibility to excite broadband pulses and thus to inspect objects with one-sided access. We present various thermoacoustic transducers consisting of an electrically conductive film on a solid substrate. The first type of transducer is a transmitter with an indium-tin-oxide electrode on a glass substrate combined with a laser Doppler vibrometer as a receiver. The second type of transducer combines thermoacoustic transmission and piezoelectric reception, having a titanium electrode as a transmitter deposited onto charged cellular polypropylene serving as a piezoelectric receiver. Using a focusing thermoacoustic transmitter and a separate cellular polypropylene receiver, a through-transmission inspection of a 4 mm thick CFRP test piece with inserts as small as 1 mm was performed. The same emitter and a laser vibrometer as a receiver were used for a one-sided inspection of a Plexiglas block with a cross hole at 15 mm depth. A twin probe consisting of a thermoacoustic transmitter on a cellular polypropylene receiver was applied to a profile measurement on a step wedge with flat bottom holes. The smallest detected diameter of a flat bottom hole was 1 mm. Sound pressure level above 140dB was achieved with each of these transmitters. Thermoacoustic transmitters enable a step towards one-sided air-coupled ultrasonic inspection.zeige mehrzeige weniger

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Metadaten
Autor*innen:Mate Gaal, Jürgen Bartusch, Florian Schadow, Uwe Beck, M. Daschewski, M. Kreutzbruck
Dokumenttyp:Beitrag zu einem Tagungsband
Veröffentlichungsform:Graue Literatur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):IEEE International Ultrasonics Symposium
Jahr der Erstveröffentlichung:2016
Erste Seite:(online publication) 1
Letzte Seite:4
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Freie Schlagwörter:Air-coupled; Airborne; Ferroelectret; Thermoacoustic; Ultrasonic transducer
Veranstaltung:IEEE International Ultrasonics Symposium
Veranstaltungsort:Tours, France
Beginndatum der Veranstaltung:18.09.2016
Enddatum der Veranstaltung:21.09.2016
ISSN:1948-5719
ISBN:978-1-4673-9897-8
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:24.10.2016
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:15.12.2016
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