TY - JOUR A1 - Döring, Joachim A1 - Bovtun, V. A1 - Gaal, Mate A1 - Bartusch, Jürgen A1 - Erhard, Anton A1 - Kreutzbruck, Marc A1 - Yakymenko, Y. T1 - Piezoelectric and electrostrictive effects in ferroelectret ultrasonic transducers N2 - Electromechanical response of polypropylene ferroelectret transducers under application of high-voltage pulses was measured by laser Doppler vibrometry and compared with results of ultrasonic through-air transmission between two ferroelectret transducers. The electromechanical response was completely explained by piezoelectric and electrostrictive effects. The electrostrictive effect dominates at high voltages and provides significant enlargement of the transducer constant, up to factor of 2.5. The induced strain of 1.7% was achieved at – 2000 V. The nonlinear ultrasonic transmission was shown to be well described by the piezoelectric and electrostrictive response of transmitter, except in the range of high negative exciting voltages where some limitation of the transmitted signal was observed. This limitation seems not to be a fundamental one and does not abolish the advantages of high-voltage excitation of polypropylene ferroelectret transducers. KW - Electromechanical effects KW - Ferroelectric devices KW - Piezoelectric transducers KW - Piezoelectricity KW - Ultrasonic transducers KW - Ultrasonic transmission KW - Cellular polypropylene KW - Ferroelectret KW - Electrostriction PY - 2012 DO - https://doi.org/10.1063/1.4759052 SN - 0021-8979 SN - 1089-7550 VL - 112 IS - 8 SP - 084505-1 - 084505-6 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-26806 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gaal, Mate A1 - Döring, Joachim A1 - Bartusch, Jürgen A1 - Lange, Thorid A1 - Hillger, W. A1 - Brekow, Gerhard A1 - Kreutzbruck, Marc T1 - Ferroelectret transducers for air-coupled ultrasonic testing of fiber-reinforced polymers N2 - Ferroelectrets are promising materials for air-coupled ultrasonic transducers. A transducer made of polarized cellular polypropylene, including its electronic interface, was developed and compared with conventional air-coupled probes. Test pieces of fiber-reinforced polymer containing impact flaws and flat-bottom holes were inspected in transmission. The ferroelectret transducers achieved a considerably higher signal-to-noise ratio. The impacts were clearly visible with all transducers, but less noisy with ferroelectret transducers. The flat-bottom holes were better detectable than with a conventional probe with about the same focus size. T2 - 39th Annual review of progress in quantitative nondestructive evaluation CY - Denver, Colorado, USA DA - 15.07.2012 KW - Air-coupled ultrasound KW - Transducer KW - Ferroelectret PY - 2013 SN - 978-0-7354-1129-6 DO - https://doi.org/10.1063/1.4789224 SN - 0094-243X SN - 1551-7616 N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings VL - 1511 SP - 1534 EP - 1540 AN - OPUS4-27747 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gaal, Mate A1 - Bartusch, Jürgen A1 - Döring, Joachim A1 - Dohse, Elmar A1 - Lange, Thorid A1 - Hillger, W. A1 - Kreutzbruck, Marc T1 - Air-coupled ferroelectret ultrasonic transducers applied to testing of fiber-reinforced polymers N2 - Air-coupled ultrasound is an emerging testing technique applied to materials with sensitive surfaces. One of the most important applications is on components made of carbon-fiber-reinforced polymers, which find their use in aerospace and increasingly in automotive industry. A promising alternative to piezoceramic transducers with matching layers is the use of ferroelectrets, which are charged cellular polymers exhibiting piezoelectric and ferroelectric properties. Ferroelectret transducers for air-coupled ultrasonic testing, including their electronic interface, were developed and compared with conventional air-coupled probes, all having a resonance frequency between 200 and 250 kHz. The cPP transducers were excited with square pulses of 2.5 kV, whereas two different piezoceramic transducers with similar properties were excited with 800 V. The signal-to-noise ratio was evaluated and compared. Two test blocks, (i) a sandwich-structured composite with a honeycomb core between plates of carbon-fiber-reinforced polymer (CFRP) containing an impact and (ii) a CFRP plate with an impact and several flat-bottom holes, were inspected in transmission. The ferroelectret transducers achieved a SNR at least 11 dB higher than the conventional probes. The impacts were clearly visible with all probes, but less noisy with ferroelectret transducers. The flat T2 - 12th International conference of the Slovenian society for non-destructive testing - Application of contemporary non-destructive testing in engineering CY - Portoroz, Slovenia DA - 04.09.2013 KW - Air-coupled ultrasound KW - Transducer KW - Ferroelectret KW - Cellular polypropylene KW - Fiber-reinforced polymers PY - 2013 SN - 978-961-93537-0-7 SP - 43 EP - 50 AN - OPUS4-29927 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -