TY - CONF A1 - Gaal, Mate A1 - Bartusch, Jürgen A1 - Daschewski, Maxim A1 - Dohse, Elmar A1 - Köppe, Enrico A1 - Weise, Matthias A1 - Hillger, W. A1 - Kreutzbruck, Marc T1 - Schwingverhalten des Ferroelektret-Senders für Luftultraschall T2 - DGZfP-Jahrestagung 2013 T2 - DGZfP-Jahrestagung 2013 CY - Dresden, Germany DA - 2013-05-06 KW - Luftultraschall KW - Wandler KW - Ferroelektret KW - Zelluläres Polypropylen KW - Elektrostriktion PY - 2013 SN - 978-3-940283-49-8 IS - Mo.3.B.4 SP - 1 EP - 8 AN - OPUS4-28651 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Daschewski, Maxim A1 - Harrer, Andrea A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Beck, Uwe A1 - Lange, Thorid A1 - Weise, Matthias T1 - A resonance-free nano-film airborne ultrasound emitter T2 - 39th Annual review of progress in quantitative nondestructive evaluation (Proceedings) N2 - In this contribution we present a novel thermo-acoustic approach for the generation of broad band airborne ultrasound and investigate the applicability of resonance-free thermo-acoustic emitters for very short high pressure airborne ultrasound pulses. We report on measurements of thermo-acoustic emitter consisting of a 30 nm thin metallic film on a usual soda-lime glass substrate, generating sound pressure values of more than 140 dB at 60 mm distance from the transducer and compare the results with conventional piezoelectric airborne ultrasound transducers. Our experimental investigations show that such thermo-acoustic devices can be used as broad band emitters using pulse excitation. T2 - 39th Annual review of progress in quantitative nondestructive evaluation CY - Denver, Colorado, USA DA - 2012-07-15 KW - Thermo-acoustic KW - Broad band airborne ultrasound KW - High pressure airborne ultrasound KW - Resonance free ultrasound transducer KW - Broad band ultrasonic emitter KW - Measurement sound particle velocity PY - 2013 SN - 978-0-7354-1129-6 DO - https://doi.org/10.1063/1.4789225 SN - 0094-243X SN - 1551-7616 N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings VL - 1511 SP - 1541 EP - 1546 AN - OPUS4-27790 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Daschewski, Maxim A1 - Boehm, Rainer A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Harrer, Andrea T1 - Physics of thermo-acoustic sound generation JF - Journal of applied physics N2 - We present a generalized analytical model of thermo-acoustic sound generation based on the analysis of thermally induced energy density fluctuations and their propagation into the adjacent matter. The model provides exact analytical prediction of the sound pressure generated in fluids and solids; consequently, it can be applied to arbitrary thermal power sources such as thermophones, plasma firings, laser beams, and chemical reactions. Unlike existing approaches, our description also includes acoustic near-field effects and sound-field attenuation. Analytical results are compared with measurements of sound pressures generated by thermo-acoustic transducers in air for frequencies up to 1 MHz. The tested transducers consist of titanium and indium tin oxide coatings on quartz glass and polycarbonate substrates. The model reveals that thermo-acoustic efficiency increases linearly with the supplied thermal power and quadratically with thermal excitation frequency. Comparison of the efficiency of our thermo-acoustic transducers with those of piezoelectric-based airborne ultrasound transducers using impulse excitation showed comparable sound pressure values. The present results show that thermo-acoustic transducers can be applied as broadband, non-resonant, high-performance ultrasound sources. KW - Thermophone KW - Ionophone KW - Thermo-acoustic effect KW - Non resonant ultrasound source PY - 2013 DO - https://doi.org/10.1063/1.4821121 SN - 0021-8979 SN - 1089-7550 VL - 114 SP - 114903-1 - 114903-12 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-29278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kreutzbruck, Marc A1 - Pelkner, Matthias A1 - Gaal, Mate A1 - Daschewski, Maxim A1 - Brackrock, Daniel T1 - Evolution of modern NDT-methods for the inspection of lightweight components T2 - 12th International conference of the Slovenian society for non-destructive testing - Application of contemporary non-destructive testing in engineering (Proceedings) N2 - NDT is a multidisciplinary research area fusing the disciplines of natural Science and engineering. Particularly in the early development stages of a new testing method, feasibility investigations focus on the fundamental physical interaction between the sensing mechanism and specimen. Research activities during subsequent phases of modular prototype development, technical System Integration and Validation primarily attempt to solve the practical engineering and real-life aspects of a testing method. We show several examples of new methods in different stages of development and highlight the potential for further industrial use. The first section deals with Steel surfaces of lightweight components which are inspected with pm-sized magneto resistive sensor arrays. This quantitative magnetic stray field approach combines high spatial resolution and very high sensitivity, enabling the user to detect even very small micro-defects. Tuming to CFRP components we also show new developments in airbome ultrasonic testing. Here we use ferroelectret foils to reduce the acoustical mismatch between transducer and air, which enhances the signal-to-noise ratio. A further example illuminates the use of metallic nano layers as a broadband thermo acoustical emitter. Their use provides both high sound pressures and very broadband Signal characteristics. When it comes to CFRP components and other anisotropic and highly Scattering materials, ultrasonic matrix arrays in conjunction with many angles of incidences per transducer position can help to enhance the statistics of a testing problem. In the field of conventional water-coupled UT testing we also show the use of matrix array transducers providing a tomographic-like 3D-image of impact damage in CFRP samples. 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 - GMR-sensors arrays KW - Air coupled ultrasonics KW - Thermo acoustical transducers KW - Matrix arrays PY - 2013 SN - 978-961-93537-0-7 SP - 303 EP - 314 AN - OPUS4-29245 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Harrer, Andrea A1 - Daschewski, Maxim A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Guderian, Matthias A1 - Meyer-Plath, Asmus T1 - Thermoacoustic generation of airborne ultrasound using carbon materials at the micro- and nanoscale JF - International journal of applied electromagnetics and mechanics N2 - The generation of airborne ultrasound is presented using the thermoacoustic principle applied to carbon materials at the micro- and nanoscale. Such materials are shown to be capable of emitting ultrasound when being fed by an alternating current. We tested the acoustic performance of carbon fibers, bucky papers and electrospun polyacrylonitrile-derived carbon nanofibers and determined the sound pressure for frequencies up to 350 kHz. A comparison between the experimental results and the theoretical prediction showed remarkable agreement for frequencies up to 150 kHz. Beyond 150 kHz, we found slight deviations from the expected sound pressure dependence on the square root of the frequency. KW - Thermoacoustic KW - Airborne ultrasound transducer KW - Sound pressure PY - 2012 DO - https://doi.org/10.3233/JAE-2012-1440 SN - 1383-5416 SN - 0925-2096 VL - 39 IS - 1-4 SP - 35 EP - 41 PB - IOS Press CY - Amsterdam, The Netherlands AN - OPUS4-26737 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Daschewski, Maxim A1 - Harrer, Andrea A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Guderian, Matthias A1 - Meyer-Plath, Asmus ED - Linde, B. B. J. ED - Paczkowski, J. ED - Ponikwicki, N. T1 - Carbon nanomaterials as broadband airborne ultrasound transducer T2 - International congress on ultrasonics N2 - A method has been developed for the generation of airborne ultrasound using the thermoacoustic principle applied to carbon materials at the micro- and nanoscale. Such materials are shown to be capable to emitting the ultrasound. We tested the acoustic performance of electrospun polyacrylonitrile-derived carbon nanofibers tissues and determined the sound pressure for frequencies up to 350 kHz. The experimental results are compared to analytic calculations. T2 - International congress on ultrasonics CY - Gdansk, Poland DA - 2011-09-05 KW - Thermoacoustic KW - Airborne ultrasound transducer KW - Sound pressure PY - 2012 SN - 978-0-7354-1019-0 DO - https://doi.org/10.1063/1.3703262 SN - 0094-243X N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings IS - 1433 SP - 624 EP - 627 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-26788 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Daschewski, Maxim A1 - Harrer, Andrea A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Beck, Uwe A1 - Lange, Thorid A1 - Weise, Matthias T1 - Metallic nanofilm as resonance-free airborne ultrasound emitter T2 - IUS 2012 - IEEE International Ultrasonics Symposium (Proceedings) N2 - A novel approach for the generation of broadband airborne ultrasound by using the thermo-acoustic effect is presented in this contribution. We investigate the applicability of resonance-free thermo-acoustic emitters for generation of very short high pressure airborne ultrasound pulses. A thermoacoustic emitter consisting of a 30 nm thin metallic film on a usual soda-lime glass substrate generates sound pressure values of more than 140 dB at 60 mm distance. The results are compared with conventional piezoelectric airborne ultrasound transducers. Our investigations show the applicability of the thermo-acoustic devices for broadband and high pressure ultrasound emitters using pulse excitation. T2 - 2012 IEEE International Ultrasonics Symposium (IUS) CY - Dresden, Germany DA - 2012-10-07 KW - Thermo-acoustic KW - Broadband airborne ultrasound KW - Resonance-free ultrasound transducer KW - High pressure airborne ultrasound KW - Sound particle velocity measurement PY - 2012 SN - 978-1-4673-4562-0 DO - https://doi.org/10.1109/ULTSYM.2012.0241 SN - 1948-5719 SP - 965 EP - 967 AN - OPUS4-29152 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gaal, Mate A1 - Daschewski, Maxim A1 - Bartusch, Jürgen A1 - Schadow, Florian A1 - Dohse, Elmar A1 - Kreutzbruck, Marc A1 - Weise, Matthias A1 - Beck, Uwe T1 - Novel air-coupled ultrasonic transducer combining the thermoacoustic with the piezoelectric effect T2 - Proceedings of WCNDT 2016 N2 - In recent years, there has been an increasing industrial demand for one-sided inspection of various structures by means of air-coupled ultrasonic technique. Lightweight structures based on carbon-fibre-reinforced polymers may have very complex shapes, making air-coupled transmission difficult or even impossible. The inspection of concrete structures is another example where one-sided inspection is required. To address these challenges a new type of transducer for air-coupled pulse-echo inspection was developed, which unites two principles: thermoacoustic emission and piezoelectric reception. The thermoacoustic emitter is a titanium electrode with a thickness of several tens of nanometer. This electrode was deposited onto charged cellular polypropylene, which serves as a piezoelectric receiver. The thermoacoustic transmission is based on a transformation of the thermal energy of an electrically heated electrode into the acoustic energy of an ultrasonic wave. Thermoacoustic emitters provide resonance-free behaviour and thus extremely broadband pulses. Charged cellular polypropylene is piezoelectric due to the polarization of its cells and it is well matched to air, with a Young modulus in the order of magnitude of MPa. In this contribution we present some pulse-echo measurements with the first prototypes of the combined thermoacoustic-piezoelectric transducer. T2 - World Conference of Non-Destructive Testing CY - Munich, Germany DA - 13.6.2016 KW - Thermoacoustic KW - Piezoelectric KW - Ultrasonic transducer KW - Ferroelectret PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-367151 VL - 158 SP - Mo.1.F.4, 1 EP - 6 AN - OPUS4-36715 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Daschewski, Maxim A1 - Kreutzbruck, Marc A1 - Prager, Jens T1 - Influence of thermodynamic properties of a thermo-acoustic emitter on the efficiency of thermal airborne ultrasound generation JF - Ultrasonics N2 - In this work we experimentally verify the theoretical prediction of the recently published Energy Density Fluctuation Model (EDF-model) of thermo-acoustic sound generation. Particularly, we investigate experimentally the influence of thermal inertia of an electrically conductive film on the efficiency of thermal airborne ultrasound generation predicted by the EDF-model. Unlike widely used theories, the EDF-model predicts that the thermal inertia of the electrically conductive film is a frequency-dependent parameter. Its influence grows non-linearly with the increase of excitation frequency and reduces the efficiency of the ultrasound generation. Thus, this parameter is the major limiting factor for the efficient thermal airborne ultrasound generation in the MHz-range. To verify this theoretical prediction experimentally, five thermo-acoustic emitter samples consisting of Indium-Tin-Oxide (ITO) coatings of different thicknesses (from 65 nm to 1.44 lm) on quartz glass substrates were tested for airborne ultrasound generation in a frequency range from 10 kHz to 800 kHz. For the measurement of thermally generated sound pressures a laser Doppler vibrometer combined with a 12 lm thin polyethylene foil was used as the sound pressure detector. All tested thermo-acoustic emitter samples showed a resonance-free frequency response in the entire tested frequency range. The thermal inertia of the heat producing film acts as a low-pass filter and reduces the generated sound pressure with the increasing excitation frequency and the ITO film thickness. The difference of generated sound pressure levels for samples with 65 nm and 1.44 lm thickness is in the order of about 6 dB at 50 kHz and of about 12 dB at 500 kHz. A comparison of sound pressure levels measured experimentally and those predicted by the EDF-model shows for all tested emitter samples a relative error of less than ±6%. Thus, experimental results confirm the prediction of the EDF-model and show that the model can be applied for design and optimization of thermo-acoustic airborne ultrasound emitters. KW - Thermophone KW - Thermo-acoustic effect KW - Thermal sound generation KW - Resonance-free ultrasound emitter KW - Energy density fluctuation KW - Thermal inertia PY - 2015 DO - https://doi.org/10.1016/j.ultras.2015.06.008 SN - 0041-624x VL - 63 SP - 16 EP - 22 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-34573 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Daschewski, Maxim A1 - Kreutzbruck, Marc A1 - Prager, Jens A1 - Dohse, Elmar A1 - Gaal, Mate A1 - Harrer, Andrea T1 - Resonanzfreie Messung und Anregung von Ultraschall JF - Technisches Messen N2 - In diesem Beitrag präsentieren wir innovative Methoden für die breitbandige und resonanzfreie Messung und Anregung von Ultraschall. Das Messverfahren verwendet eine Kunststofffolie und ein Laser-Vibrometer als breitbandigen und resonanzfreien Empfänger. Im Allgemeinen ermöglicht dieses Verfahren eine präzise Messung der Schallschnelle und des Schalldruckes in beliebigen, für das Laserlicht transparenten Flüssigkeiten und Gasen mit bekannter Dichte und Schallgeschwindigkeit. Das resonanzfreie Senden von Ultraschall basiert auf einem elektro-thermo-akustischen Wandlerprinzip und ermöglicht, im Gegensatz zu herkömmlichen Ultraschallwandlern, die Erzeugung von beliebig geformten akustischen Signalen ohne Resonanzen und ohne Nachschwingen. N2 - In this contribution we present innovative methods for broadband and resonance-free sensing and emitting of ultrasound. The sensing method uses a polyethylene foil and a laser vibrometer as a broadband and resonance-free sound receiver. In general, this method enables absolute measurement of sound particle velocity and sound pressure in arbitrary, laser beam transparent liquids and gases with known density and sound velocity. The resonance-free emitting method is based on the electro-thermo-acoustic principle and enables, contrary to conventional ultrasound transducers, generation of arbitrary shaped acoustic signals without resonances and post-oscillations. KW - Ultraschall KW - Übertragungsfunktion KW - Charakterisierung von Ultraschallmesssystemen KW - Thermo-akustische Ultraschallemitter KW - Ultrasound KW - Transfer function KW - Characterization of ultrasonic measurement systems KW - Thermo-acoustic ultrasound emitter PY - 2015 DO - https://doi.org/10.1515/teme-2014-0020 SN - 0340-837X SN - 0178-2312 SN - 0171-8096 VL - 82 IS - 3 SP - 156 EP - 166 PB - Oldenbourg CY - München AN - OPUS4-32733 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -