Zitieren Sie bitte immer diesen URN: urn:nbn:de:kobv:b43-317204
Ultrasonic testing of adhesively bonded joints using air-coupled cellular polypropylene transducers
- In air-coupled ultrasonic testing, the impedance mismatch between the transducer and the air is commonly being solved by adding matching layers to composite transducers. To avoid the difficult technological procedure regarding matching layers, some new piezoelectric materials have been proposed. Most promising are ferroelectrets, which are charged cellular polymers, having ferroelectric and consequently piezoelectric properties. In particular, the extreme softness of cellular polypropylene (cPP) leads to a high piezoelectric constant and to a good impedance match with the air, making matching layers redundant. Its elasticity modulus below 1 MPa causes an additional effect not observed with common piezoelectric materials: that is the electrostrictive effect, here defined as the thickness change due to the attractive force between the transducer electrodes. This effect exceeds the piezoelectric effect at excitation voltages over 1 kV. The extreme softness of cPP leads also to highIn air-coupled ultrasonic testing, the impedance mismatch between the transducer and the air is commonly being solved by adding matching layers to composite transducers. To avoid the difficult technological procedure regarding matching layers, some new piezoelectric materials have been proposed. Most promising are ferroelectrets, which are charged cellular polymers, having ferroelectric and consequently piezoelectric properties. In particular, the extreme softness of cellular polypropylene (cPP) leads to a high piezoelectric constant and to a good impedance match with the air, making matching layers redundant. Its elasticity modulus below 1 MPa causes an additional effect not observed with common piezoelectric materials: that is the electrostrictive effect, here defined as the thickness change due to the attractive force between the transducer electrodes. This effect exceeds the piezoelectric effect at excitation voltages over 1 kV. The extreme softness of cPP leads also to high flexibility, enabling easy focusing by bending the transducer. We have developed air-coupled ultrasonic transducers based on cPP. This includes the electrical matching networks for the transmitter and for the receiver. The transmitter is excited with voltages up to 2.5 kV, so that the electrostrictive effect dominates, leading to sound pressure around 145dB at the transducer surface. These transducers have been applied for testing carbon-fiber-reinforced polymer plates, adhesive joints and other composite structures. Here we report about ultrasonic transmission of two types of adhesive joints. The first one is multi-layer aluminium components with some artificial disbonds, which are common in aerospace industry, and the second one is an aluminium-steel joint with polyurethane adhesive, which is used in automotive industry.…
Autor*innen: | Mate GaalORCiD, Elmar Dohse, Jürgen Bartusch, Enrico Köppe, Marc Kreutzbruck, W. Hillger, J. M. Amos |
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Dokumenttyp: | Beitrag zu einem Tagungsband |
Veröffentlichungsform: | Verlagsliteratur |
Sprache: | Englisch |
Titel des übergeordneten Werkes (Englisch): | ECNDT 2014 - 11th European conference on non-destructive testing (Proceedings) |
Jahr der Erstveröffentlichung: | 2014 |
Veröffentlichende Institution: | Bundesanstalt für Materialforschung und -prüfung (BAM) |
Verlag: | Brno University of Technology |
Erste Seite: | 1 |
Letzte Seite: | 8 |
Freie Schlagwörter: | Adhesive joint; Air-coupled; Cellular polypropylene; Ferroelectret; Transducer; Ultrasonic testing |
Veranstaltung: | ECNDT 2014 - 11th European conference on non-destructive testing |
Veranstaltungsort: | Prague, Czech Republic |
Beginndatum der Veranstaltung: | 06.10.2014 |
Enddatum der Veranstaltung: | 10.10.2014 |
URN: | urn:nbn:de:kobv:b43-317204 |
ISBN: | 978-80-214-5018-9 |
Verfügbarkeit des Dokuments: | Datei für die Öffentlichkeit verfügbar ("Open Access") |
Lizenz (Deutsch): | Creative Commons - Namensnennung-Keine Bearbeitung |
Datum der Freischaltung: | 20.02.2016 |
Referierte Publikation: | Ja |
Datum der Eintragung als referierte Publikation: | 30.10.2014 |
Schriftenreihen ohne Nummerierung: | Wissenschaftliche Artikel der BAM |