TY - JOUR A1 - Bovtun, Viktor Petrovic A1 - Stark, Wolfgang A1 - Kelm, Jürgen A1 - Porokhonskyy, V. A1 - Yakimenko, Y. T1 - Microwave Dielectric Properties of Rubber Compounds Undergoing Vulcanisation - Part 1. Natural rubber with and without carbon black filler KW - Dielectric parameters KW - Microwave methods KW - Vulcanisation KW - Elastomers KW - Monitoring PY - 2000 SN - 0948-3276 SN - 0022-9520 PB - Hüthig CY - Heidelberg AN - OPUS4-1062 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bovtun, Viktor Petrovic A1 - Stark, Wolfgang A1 - Kelm, Jürgen A1 - Pashkov, V.M. A1 - Yakimenko, Y. T1 - Characterization of carbon black filled rubber compounds by the Microwave Coaxial Method KW - Dielectric parameters KW - Microwave methods KW - Filled rubber compounds KW - Vulcanisation PY - 2005 SN - 0025-5300 VL - 47 IS - 3 SP - 118 EP - 122 PB - Carl Hanser Verlag CY - München AN - OPUS4-7273 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bovtun, Viktor Petrovic A1 - Döring, Joachim A1 - Bartusch, Jürgen A1 - Gaal, Mate A1 - Erhard, Anton A1 - Kreutzbruck, Marc A1 - Yakymenko, Y. T1 - Enhanced electromechanical response of ferroelectret ultrasonic transducers under high voltage excitation N2 - Polypropylene based ferroelectret films exhibit a strong electromechanical activity and provide a promising solution for the air coupled ultrasonic (ACUS) transducers. Ultrasonic transmission between two air coupled ferroelectret transducers in dependence on the amplitude and polarity of the high voltage exciting pulse revealed a strongly non-linear electromechanical response of the ferroelectret transmitter which provides an increase in the transmitter efficiency. The authors present a simple model describing both promotion and competition of the piezoelectric and electrostriction contributions, as well as increase in the transducer constant under high voltage excitation. Enlargement of the inverse transducer constant of the polypropylene ferroelectret film by a factor of 4 was demonstrated. The non-linear properties of the polypropylene ferroelectrets result in a strong increase in their ACUS figure of merit under the high voltage excitation, which exceeds the results of their technological optimisation. Consequently, enhancement of the ACUS system transmission by 12 dB and signal to noise ratio by 32 dB was achieved. KW - Air coupled ultrasonics KW - Non-contact transducers KW - Ferroelectrets KW - Piezoelectric effect KW - Electrostriction KW - Cellular polypropylene KW - Ultrasonic transducer PY - 2013 U6 - https://doi.org/10.1179/1743676112Y.0000000021 SN - 1743-6753 SN - 1743-6761 VL - 112 IS - 2 SP - 97 EP - 102 PB - Maney CY - London AN - OPUS4-27880 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Döring, Joachim A1 - Bartusch, Jürgen A1 - Gaal, Mate A1 - Kreutzbruck, Marc A1 - Erhard, Anton A1 - Bovtun, Viktor Petrovic T1 - Ferroelektret-Prüfköpfe für die zerstörungsfreie Prüfung mit Luftultraschall N2 - 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. KW - Prüfkopf KW - Ferroelektret KW - Luftultraschall KW - Zerstörungsfreie Prüfung PY - 2013 SN - 0025-5300 VL - 55 IS - 2 SP - 96 EP - 102 PB - Hanser CY - München AN - OPUS4-27778 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bovtun, Viktor Petrovic A1 - Döring, Joachim A1 - Bartusch, Jürgen A1 - Beck, Uwe A1 - Erhard, Anton A1 - Yakymenko, Y. T1 - Ferroelectret non-contact ultrasonic transducers N2 - 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 air–transducer 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. KW - Piezoelectric film KW - Air borne transducer KW - Non-destructive testing PY - 2007 SN - 0947-8396 VL - 88 IS - 4 SP - 737 EP - 743 PB - Springer CY - Berlin AN - OPUS4-15074 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bovtun, Viktor Petrovic A1 - Döring, Joachim A1 - Bartusch, Jürgen A1 - Beck, Uwe A1 - Erhard, Anton A1 - Yakimenko, Y. T1 - EMFIT Ferroelectret Film Transducers for Non-Contact Ultrasonic Testing T2 - 9th European Conference on NDT CY - Berlin, Germany DA - 2006-09-25 KW - Non-contact ultrasound KW - Ferroelectret film KW - Ultrasonic transducer PY - 2006 SN - 3-931381-86-2 SP - 1 EP - 10(?) PB - European Federation for Non-Destructive Testing CY - Berlin AN - OPUS4-14211 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Döring, Joachim A1 - Bovtun, Viktor Petrovic A1 - Bartusch, Jürgen A1 - Erhard, Anton A1 - Kreutzbruck, Marc A1 - Yakymenko, Y. T1 - Nonlinear electromechanical response of the ferroelectret ultrasonic transducers N2 - The ultrasonic transmission between two air-coupled polypropylene (PP) ferroelectret (FE) transducers in dependence on the amplitude of the high-voltage exciting pulse revealed a strongly nonlinear electromechanical response of the FE transmitter. This phenomenon is described by a linear increase of the inverse electromechanical transducer constant t33(1) of the PP FE film with an increase of the exciting electrical pulse amplitude. Enlargement of t33(1) by a factor of 4 was achieved by application of 3500 V exciting pulses. The electrostriction contribution to t33(1) can be attributed to the electrostatic force between electrodes and the Maxwell stress effect. The nonlinear electromechanical properties of the PP FE result in a strong increase of its air-coupled ultrasonic (ACUS) figure of merit (FOM) under the high-voltage excitation, which exceeds results of the PP FE technological optimization. The FOM increase can be related to the increase of PP FE coupling factor and/or to the decrease of its acoustic impedance. A significant enhancement of the ACUS system transmission (12 dB) and signal-to-noise ratio (32 dB) was demonstrated by the increase of excitation voltage up to 3500 V. The nonlinear electromechanical properties of the PP FEs seem to be very important for their future applications. KW - Airborne ultrasonics KW - Electret film KW - Transducer KW - Nonlinearity PY - 2010 U6 - https://doi.org/10.1007/s00339-010-5752-7 SN - 0947-8396 VL - 100 IS - 2 SP - 479 EP - 485 PB - Springer CY - Berlin AN - OPUS4-21809 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bovtun, Viktor Petrovic A1 - Döring, Joachim A1 - Wegener, M. A1 - Bartusch, Jürgen A1 - Beck, Uwe A1 - Erhard, Anton A1 - Borisov, V. T1 - Air-coupled ultrasonic applications of ferroelectrets KW - Air-coupled ultrasonics KW - Non-contact transducers KW - Ferroelectrets KW - Electromechanical properties PY - 2008 U6 - https://doi.org/10.1080/00150190802380243 SN - 0015-0193 SN - 1563-5112 VL - 370 IS - 1 SP - 11 EP - 17 PB - Taylor & Francis CY - New York, NY AN - OPUS4-20924 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gaal, Mate A1 - Döring, Joachim A1 - Bartusch, Jürgen A1 - Beck, Uwe A1 - Weise, Matthias A1 - Bovtun, Viktor Petrovic A1 - Brekow, Gerhard A1 - Kreutzbruck, Marc T1 - Parameter reproducibility of polypropylene ferroelectret transducers for air-coupled ultrasonic testing N2 - The extremely low acoustic impedance of polypropylene ferroelectret combined with its piezoelectric properties makes this material suitable for construction of aircoupled ultrasonic transducers for non-destructive testing. For the fabrication of transducers with a stable quality, the reproducibility of their key parameters is of interest. The reproducibility was evaluated by means of (i) impedance spectroscopy and (ii) pulse-echo measurements. (i) Impedance spectroscopy was applied to identify the resonance frequency, the coupling factor and the acoustic impedance of several nominally identical transducers. (ii) Pulse-echo measurements yielded the signal form of these transducers. The variation of the signal amplitude measured with pulseecho technique was about 10 dB. A part of this variation Comes from the deposition of transducer electrodes and another part from local variations of ferroelectret properties. The variation of the signal amplitude was caused by the observed variation of the coupling factor, which was also about 10 dB. The variation of the acoustic impedance was only about 1 dB, thus having no effect on the variation of the signal amplitude. These results indicate that the variability can be reduced by improving the control of electrode deposition and by optimizing the production technology affecting the reproducibility of material properties. T2 - 2011 IEEE International ultrasonics symposium (IUS) CY - Orlando, FL, USA DA - 18.10.2011 KW - Air-coupled ultrasonic transducers KW - Polypropylene ferroelectret KW - Reproducibility PY - 2011 IS - Abstract-ID 258 SP - 1 EP - 3 AN - OPUS4-26405 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gaal, Mate A1 - Bovtun, Viktor A1 - Stark, Wolfgang A1 - Erhard, Anton A1 - Yakymenko, Y. A1 - Kreutzbruck, Marc T1 - Viscoelastic properties of cellular polypropylene ferroelectrets N2 - Viscoelastic properties of cellular polypropylene ferroelectrets (PP FEs) were studied at low frequencies (0.3–33 Hz) by dynamic mechanical analysis and at high frequencies (250 kHz) by laser Doppler vibrometry. Relaxation behavior of the in-plane Young’s modulus (Y´ 11~1500 MPa at room temperature) was observed and attributed to the viscoelastic response of polypropylene matrix. The out-of-plane Young’s modulus is very small (Y´33≈0.1 MPa) at low frequencies, frequency- and stress-dependent, evidencing nonlinear viscoelastic response of PP FEs. The highfrequency mechanical response of PP FEs is shown to be linear viscoelastic with Y´33≈0.8 MPa. It is described by thickness vibration mode and modeled as a damped harmonic oscillator with one degree of freedom. Frequency dependence of Y*33 in the large dynamic strain regime is described by the broad Cole-Cole relaxation with a mean frequency in kHz range attributed to the Dynamics of the air flow between partially closed air-filled voids in PP FEs. Switching-off the relaxation contribution causes dynamic crossover from the nonlinear viscoelastic regime at low frequencies to the linear viscoelastic regime at high frequencies. In the small strain regime, contribution of the air flow seems to be insignificant and the power-law response, attributed to the mechanics of polypropylene cell walls and closed air voids, dominates in a broad frequency range. Mechanical Relaxation caused by the air flow mechanism takes place in the sound and ultrasound frequency range (10 Hz–1MHz) and, therefore, should be taken into account in ultrasonic applications of the PP FEs deal with strong exciting or receiving signals. KW - Viscoelastic KW - Cellular polypropylene KW - Ferroelectret PY - 2016 U6 - https://doi.org/10.1063/1.4944798 SN - 0021-8979 SN - 1089-7550 SN - 1520-8850 VL - 119 SP - Article Number: 125101 PB - AIP Publishing AN - OPUS4-35956 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Döring, Joachim A1 - Bovtun, Viktor Petrovic A1 - Bartusch, Jürgen A1 - Erhard, Anton T1 - Eigenschaften von Polypropylen- und PVDF-Folien für Luftschall-Anwendungen N2 - 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. T2 - DACH-Jahrestagung 2004 - ZfP in Forschung, Entwicklung und Anwendung CY - Salzburg, Österreich DA - 2004-05-17 KW - Luftschall-ZfP KW - Ultraschall-Wandler PY - 2004 UR - http://www.ndt.net/article/dgzfp04/papers/p11/p11.htm SP - 1 EP - 4 CY - Salzburg, Österreich AN - OPUS4-19059 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -