Filtern
Erscheinungsjahr
Dokumenttyp
Schlagworte
- Ferroelectret (11)
- Cellular polypropylene (7)
- Transducer (7)
- Air-coupled (6)
- Luftultraschall (5)
- Ferroelectrets (4)
- Ultrasonic transducer (4)
- Air-coupled ultrasound (3)
- Akustische Impedanz (3)
- Electromechanical properties (3)
- Non-contact transducers (3)
- Ultrasonic (3)
- Ultrasonic transducers (3)
- Adhesive joint (2)
- Air-coupled ultrasonics (2)
- Aushärtung (2)
- Electrostriction (2)
- Ferroelektret (2)
- Polypropylen (2)
- Sensor (2)
- Thermoacoustic (2)
- Ultraschall (2)
- Ultrasonic testing (2)
- Zelluläres Polypropylen (2)
- Acoustic sensors (1)
- Air borne transducer (1)
- Air coupled ultrasonics (1)
- Air coupled ultrasound (1)
- Air-coupled ultrasonic testing (1)
- Air-coupled ultrasonic transducers (1)
- Airborne (1)
- Airborne ultrasonics (1)
- Composite material (1)
- Cure process (1)
- Electret film (1)
- Electromechanical effects (1)
- Elektrostriktion (1)
- Ferroelectret film (1)
- Ferroelectric devices (1)
- Fiber-reinforced polymers (1)
- Focused sound fields (1)
- Focused transducers (1)
- Focusing (1)
- Gelation (1)
- Harzinjektionsverfahren (1)
- Impedance spectroscopy (1)
- Luftschall-ZfP (1)
- Materialparameter (1)
- Metal bond (1)
- Mould (1)
- Non-contact ultrasound (1)
- Non-destructive testing (1)
- Nondestructive testing (1)
- Nonlinearity (1)
- Piezoelectric (1)
- Piezoelectric effect (1)
- Piezoelectric film (1)
- Piezoelectric materials (1)
- Piezoelectric transducers (1)
- Piezoelectricity (1)
- Polypropylene ferroelectret (1)
- Process controlling (1)
- Prozesskontrolle (1)
- Prüfkopf (1)
- Pulse compression (1)
- Pulsed THz radiation system (1)
- RTM (1)
- Reproducibility (1)
- Rtm (1)
- Sensoren (1)
- Signal-Rausch-Anstand (1)
- THz imaging (1)
- Thermoset (1)
- Time domain spectroscopy (1)
- Ultraschall-Wandler (1)
- Ultrasonic imaging (1)
- Ultrasonic monitoring (1)
- Ultrasonic transmission (1)
- Ultrasound sensors (1)
- Vitrification (1)
- Wanderfolien (1)
- Wandler (1)
- Zerstörungsfreie Prüfung (1)
Organisationseinheit der BAM
Für die luftgekoppelte Ultraschall-Prüfung wird der Prototyp eines neuartigen Prüfkopfes vorgestellt. Statt eines piezokeramischen Ultraschall-Wandlers mit einer λ/4-Anpassschicht wird eine Ferroelektret-Folie aus schaumförmigem Polypropylen eingesetzt. Durch die außerordentlich geringe akustische Impedanz der Folie reduzieren sich die Reflexionsverluste an den Grenzschichten zur Luft so stark, dass bei diesem Prüfkopf auf eine λ/4-Anpassschicht verzichtet werden kann. Außerdem ist die Folie hochspannungsfest. Sie konnte mit Spannungen von mehr als 3500 V angesteuert werden und erlaubte eine Vorspannung am Ultraschall-Wandler des Empfangsprüfkopfes von 2000 V. Mithilfe der hohen Anregungsspannung stieg die Amplitude des akustischen Prüfimpulses auf das 11,2-Fache. Die Empfindlichkeit des Empfängers erhöhte sich durch die Vorspannung weiter um den Faktor 4,3. Insgesamt steigt die Amplitude am Empfänger also auf das 48-Fache, bei gleichbleibendem Rauschpegel. Ein abschließender Vergleich mit kommerziellen Luftultraschall-Prüfköpfen belegt die Überlegenheit der Folien-Prüfköpfe. Damit rückt der Einsatz einer vollwertigen Impuls-Echo-Technik auch bei der luftgekoppelten Ultraschallprüfung deutlich näher.
Analysis of the dielectric and electromechanical properties of the cellular polypropylene ferroelectret films (EMFIT) evidences their high potential for the application in the air-coupled ultrasonic transducers. Simple prototype transducers, based on the EMFIT films, were developed and their high sensitivity was proved in the air-coupled ultrasonic experiment. Amplitude and delay time scanned images of the polyethylene step wedge with holes, obtained in both pulse-echo and transmission modes, demonstrate that non-contact ultrasonic imaging with EMFIT transducers is possible.
Dielectric and electromechanical properties of the cellular polypropylene ferroelectret films (EMFIT), combining strong piezoelectric response with a low density and softness, evidence their high potential for the air-coupled ultrasonic applications. The disadvantage of the low coupling factor is compensated by the extremely low acoustic impedance, which provides excellent matching to air and promises efficient sound transmission through the airtransducer interface. The influence of the electrodes on the electromechanical properties was investigated. Electron beam evaporation technology was adapted to the EMFIT films, and films with both-sided Au and Al electrodes were prepared without reducing or suppressing of the electromechanical properties. Finally, prototype transducers based on the EMFIT films were developed. In spite of the simple construction and absence of matching layers, high sensitivity of the EMFIT transducers was proved in the air-coupled ultrasonic experiment. Amplitude and delay time scanned images of the polyethylene step wedge with holes, obtained in both pulse-echo and transmission modes, demonstrate that non-contact ultrasonic imaging and testing with EMFIT transducers is possible.
Making Cure Visible
(2005)