Filtern
Erscheinungsjahr
Dokumenttyp
Referierte Publikation
- nein (29) (entfernen)
Schlagworte
- Cellular polypropylene (4)
- Ferroelectret (4)
- Luftultraschall (4)
- Akustische Impedanz (3)
- Transducer (3)
- Air-coupled (2)
- Air-coupled ultrasound (2)
- Polypropylen (2)
- Sensor (2)
- Ultrasonic transducer (2)
- Zelluläres Polypropylen (2)
- Adhesive joint (1)
- Air coupled ultrasound (1)
- Air-coupled ultrasonic testing (1)
- Aushärtung (1)
- Electromechanical properties (1)
- Elektrostriktion (1)
- Ferroelectret film (1)
- Ferroelectrets (1)
- Ferroelektret (1)
- Fiber-reinforced polymers (1)
- Focused sound fields (1)
- Focused transducers (1)
- Gelation (1)
- Harzinjektionsverfahren (1)
- Impedance spectroscopy (1)
- Luftschall-ZfP (1)
- Mould (1)
- Non-contact ultrasound (1)
- Piezoelectric (1)
- Piezoelectric materials (1)
- Prozesskontrolle (1)
- Pulse compression (1)
- Pulsed THz radiation system (1)
- RTM (1)
- Rtm (1)
- Signal-Rausch-Anstand (1)
- THz imaging (1)
- Thermoacoustic (1)
- Thermoset (1)
- Time domain spectroscopy (1)
- Ultraschall (1)
- Ultraschall-Wandler (1)
- Ultrasonic (1)
- Ultrasonic testing (1)
- Ultrasonic transducers (1)
- Ultrasound sensors (1)
- Vitrification (1)
- Wanderfolien (1)
- Wandler (1)
Air-coupled ferroelectret ultrasonic transducers applied to testing of fiber-reinforced polymers
(2013)
Highly sensitive air-coupled ultrasonic sensors are essential for various applications such as testing of composite materials. One of the major challenges for the development of air-coupled ultrasonic sensors is the impedance matching to air. With a lower acoustic impedance than the usual piezoelectric materials, charged cellular polypropylene film (cPP) offers better matching to air with a similar piezoelectric coefficient. The piezoelectric behaviour demonstrated by cPP comes from polarized air cells that create a permanent internal voltage. The sensitivity of the sensor varies with the application of an additional DC bias voltage. Thus, this work presents a cPP ultrasonic sensor with an improvement of up to 15 ± 1 dB on the signal-to-noise ratio.
Charakterisierung der Wandler für Luftultraschallprüfung aus zellulärem Polypropylen-Ferroelektret
(2011)
In den letzten Jahren stieg die Anfrage für zerstörungsfreie Prüfung (ZIP) mit Luftultraschall deutlich. Die klassische ZfP mit Ultraschall nutzt Flüssigkeiten als Koppelmittel zwischen dem Wandler und dem Prüfkörper. Für die Prüfung von Gegenständen mit empfindlicher Oberfläche, die das Koppelmittel beschädigen oder verunreinigen kann, ist deswegen Luftultraschall besser geeignet. Eine mögliche Anwendung ist beispielsweise der Nachweis von Delaminationen in glas- und kohlefaserverstärkten Verbundwerkstoffen sowie Sandwichbauteilen, die in der Luftfahrt- und der Automobilindustrie eingesetzt werden.
The curing conditions play an important role in the quality assurance of composite products.
Especially as composite materials are widely used in high tech areas so that they are required to fulfil high quality Standards. Some problems which occur during curing, for instance undercuring, can hardly be detected using Standard NDT investigations, mainly because they are manifested only at high temperatures, particularly close to glass-rubber-transition. On-line eure monitoring has the outstanding advantage that it can monitor the material parameters even at the highest temperatures possible.
In recent years eure monitoring with ultrasonic methods has become more populär. In comparison to dielectric methods mechanical parameters are measured directly. The quantities to be measured are the velocity and the attenuation of the sound wave. On this basis the storage and loss modulus can be calculated. Depending on the form of excitation with longitudinal or transversal waves these moduli are referred to as long wave or shear modulus.
Well developed Computer based technology and sensor materials are available in the non-destructive testing (NDT) market. The measuring equipment employed a commercial NDT System, which worked computer-aided. With a special Software the demands of automatic Operation under industrial conditions was accomplished. This measurement equipment was tested on composites. Its structure, performance and some practical results will be presented in the following paper.
An Methoden zur luftgekoppelten Ultraschallprüfung wird seit einigen Jahren mit großer Intensität gearbeitet. Probleme bei der praktischen Realisierung entstehen vor allem durch die großen Unterschiede in der akustischen Impedanz von Wandlermaterial und Luft. Sie führen zu erheblichen Signaldämpfungen. Durch die Verwendung von Kunststoff-Folien z.B. aus porösem Polypropylen kann dieser Unterschied stark reduziert werden.
Im Beitrag werden die akustischen Eigenschaften dieser Folien untersucht und im Hinblick auf ihre Eignung für die Luftultraschall-Technik analysiert.