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 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 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 - TY - CONF A1 - Daschewski, Maxim A1 - Kreutzbruck, Marc A1 - Prager, Jens ED - Kollmeier, B. T1 - Ein neues Modell zur Beschreibung der thermo-akustischen Schallerzeugung N2 - In unserem Beitrag präsentieren wir ein verallgemeinertes physikalisches Modell der thermischen Schallerzeugung. Im Gegensatz zur existierenden analytischen Näherungen erlaubt es eine exakte analytische Vorhersage des thermisch generierten Schalldrucks in Fluiden und Festkörpern, berücksichtigt die akustischen Nahefeld- und Schallschwächungseffekte und ist anwendbar für beliebige thermische Energiequellen, wie stromdurchflossene elektrische Leiter aber auch chemische Reaktionen, Plasmabrennen oder Laseranregung. Zur Verifikation des Modells vergleichen wir die analytischen Ergebnisse mit experimentellen Schalldruckmessungen an thermo-akustischen Emittern in Luft in einem Frequenzband von 4 kHz bis 1 MHz. Zusätzlich wurde die Effizienz der Wandler mit der von konventionellen piezoelektrischen Luftultraschallwandlern verglichen. Da die Schallerzeugung ohne mechanisch bewegliche Komponenten auskommt, arbeiten die thermo-akustischen Emitter resonanzfrei. Somit ist es möglich, beliebig geformte Schallsignale exakt und frei von Nachschwingen zu erzeugen. Thermo-akustische Schallemitter haben damit das Potenzial für eine breite Anwendung in der angewandten Akustik als leistungsfähige und resonanzfreie Schallsender mit einer Bandbreite bis in den Subgigahertz-Bereich. T2 - DAGA 2014 - 40. Jahrestagung für Akustik CY - Oldenburg, Germany DA - 10.03.2014 PY - 2014 SN - 978-3-939296-06-5 SP - 790 EP - 791 AN - OPUS4-31132 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Kitze, Jessica A1 - Brackrock, Daniel A1 - Brekow, Gerhard A1 - Prager, Jens A1 - Gaal, Mate A1 - Kreutzbruck, Marc A1 - Szabo, D. A1 - Kuti, K. A1 - Paczolay, G. T1 - SAFT und TOFD - Ein Vergleich im Analyseverhalten von Reflektoren T2 - 15. ITG/GMA-Fachtagung - Sensoren und Messsysteme 2010 CY - Nürnberg, Deutschland DA - 2010-05-18 PY - 2010 SN - 978-3-8007-3260-9 IS - C5/115 SP - 650 EP - 657 PB - VDE-Verl. CY - Berlin; Offenbach AN - OPUS4-22971 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Prager, Jens A1 - Hoever, Carsten A1 - Brekow, Gerhard A1 - Kreutzbruck, Marc T1 - Flaw detection with guided waves using phased array technique N2 - Guided waves travel in plates and hollow cylinders over large distances and propagate with multiple mode shapes. Therefore the waves can be used viably for integrity tests of large scale structures. The number of propagating modes increases with frequency. Due to their dispersive character the different modes are manageable only in a limited frequency range. Depending on the wave length and on the angle of impingement of the wave front to the coupling surface between transducer and structure, a trace wavelength is predefined and a selective excitation of single modes becomes feasible. By using phased array technique the excited wave mode can be selected by controlling the input signal of the transducer. Different modes are excitable with a sin-gle mechanical set-up. In a first step of the investigation, a calculation model is developed modelling the wave propagation and the selective excitation of guided wave modes depending on the control parameters. Dedicated experiments show the applicability of the method presented. The flaw detection of different sized cracks and of material thickness reductions is examined depending on the excitation wave mode. T2 - ECNDT 2010 - 10th European conference on non-destructive testing CY - Moscow, Russia DA - 2010-06-07 KW - Ultrasonic testing KW - Guided waves KW - Plate-like structures PY - 2010 SN - 978-1-617-82791-4 SP - 1 EP - 10 AN - OPUS4-22972 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Prager, Jens A1 - Hoever, Carsten A1 - Brekow, Gerhard A1 - Kreutzbruck, Marc ED - Mazal, Pavel T1 - Flaw detection with guided waves using phased array technique T2 - 5th International workshop of NDT experts - NDT in progress 2009 CY - Prague, Czech Republic DA - 2009-10-12 KW - Ultrasonic testing KW - Guided waves KW - Plate-like structures PY - 2009 SN - 978-80-214-3968-9 SP - 203 EP - 212 AN - OPUS4-20339 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gaal, Mate A1 - Döring, Joachim A1 - Prager, Jens A1 - Brekow, Gerhard A1 - Kreutzbruck, Marc T1 - Fehlernachweis mit Plattenwellen und Luftultraschall T2 - DGZfP-Jahrestagung 2009 CY - Münster, Deutschland DA - 2009-05-18 KW - Plattenwellen KW - Luftultraschall KW - Ultraschallprüfung PY - 2009 SN - 978-3-940283-16-0 IS - DGZfP-BB 115 ( Di.1.A.2) SP - 1 EP - 7 AN - OPUS4-20516 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hoever, Carsten A1 - Prager, Jens A1 - Brekow, Gerhard A1 - Kreutzbruck, Marc T1 - Fehlernachweis mit geführten Wellen unter Verwendung der Gruppenstrahlertechnik T2 - DGZfP-Jahrestagung 2009 CY - Münster, Deutschland DA - 2009-05-18 KW - Geführte Wellen KW - Gruppenstrahlertechnik PY - 2009 SN - 978-3-940283-16-0 IS - DGZfP-BB 115 (Poster 35) SP - 1 EP - 8 AN - OPUS4-20519 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Prager, Jens A1 - Hoever, C. A1 - Kreutzbruck, Marc T1 - Untersuchungen zur Anregung geführter Wellen in Platten mittels Gruppenstrahlertechnik N2 - Geführte Wellen breiten sich in Platten und Hohlzylindern über weite Entfernungen aus. Aus dieser Eigenschaft ergibt sich ein hohes Anwendungspotential dieser Wellenart für die zerstörungsfreie Prüfung ausgedehnter Bauteile und Strukturen mittels Ultraschall. Nachteilig für die Anwendung geführter Wellen sind ihr dispersives Verhalten und die zunehmende Anzahl ausbreitungsfähiger Wellenmoden bei hohen Frequenzen. Ziel des Einsatzes der Gruppenstrahlertechnik ist es, eine ausgewählte Wellenmode selektiv anzuregen bzw. zu empfangen. Durch die Änderung des Schwenkwinkels im Gruppenstrahlerprüfkopf wird eine definierte Spurwellenlänge auf dem Interface zwischen Prüfkopf und Struktur festgelegt, die zur Anregung einer Welle mit entsprechender Phasengeschwindigkeit führt. Da der Schwenkwinkel elektronisch verändert werden kann, lässt sich auch die angeregte Wellenmode elektronisch auswählen, worin der große Vorteil des vorgestellten Verfahrens liegt. In den vorgestellten Untersuchungen wurde die Anwendbarkeit der Methode experimentell demonstriert. Der Anregemechanismus wurde theoretisch beleuchtet und die Wellenausbreitung im Prüfkopf mit verschiedenen analytischen Ansätzen modelliert. Mit diesen Modellen können Fragen der Richtwirkung und der Effizienz der Anregung detailliert untersucht werden. Die modellierten Wellenfelder wurden mit den experimentellen Ergebnissen verglichen und die Anwendbarkeit der theoretischen Ansätze beurteilt, wobei die Ergebnisse der theoretischen Untersuchungen im Experiment verifiziert werden konnten. T2 - DGZfP-Jahrestagung 2010 CY - Erfurt, Deutschland DA - 2010-05-10 PY - 2010 SN - 978-3-940283-26-9 IS - DGZfP-BB 122 (P41) SP - 1 EP - 5 CY - Berlin AN - OPUS4-21883 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kitze, Jessica A1 - Brackrock, Daniel A1 - Brekow, Gerhard A1 - Prager, Jens A1 - Gaal, Mate A1 - Kreutzbruck, Marc A1 - Szabo, D. A1 - Kuti, K. A1 - Paczolay, G. T1 - SAFT und TOFD - Ein Vergleich im Analyseverhalten von Reflektoren N2 - Mit der Gruppenstrahlertechnik der Bundesanstalt für Materialforschung und -prüfung sind umfangreiche Untersuchungen an einer plattierten Druckbehälter-Testwand durchgeführt worden. In der vorliegenden Testwand mit einer Wanddicke von 149 mm befinden sich künstliche Testreflektoren im Schweißnaht- und Plattierungsbereich, die mit Gruppenstrahler- Prüfköpfen mit unterschiedlichen Frequenzen, Einschallwinkeln und Einschallrichtungen nachgewiesen und in ihrem Anzeigenverhalten analysiert wurden. Zur Rekonstruktion der Reflektoranzeigen wurde ein SAFT - Algorithmus verwendet, der die Variation der Einschallwinkel berücksichtigt. Zum Vergleich sind die Reflektoren auch mit der TOFD - Technik analysiert worden. Ziel der Untersuchungen war der direkte Vergleich der Eignung der SAFT- und TOFDTechnik zur quantitativen Reflektorgrößenbestimmung. T2 - DGZfP-Jahrestagung 2010 CY - Erfurt, Deutschland DA - 2010-05-10 PY - 2010 SN - 978-3-940283-26-9 IS - DGZfP-BB 122 (Mi.2.A.3) SP - 1 EP - 11 CY - Berlin AN - OPUS4-21880 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kolkoori, Sanjeevareddy A1 - Rahman, Mehbub-Ur A1 - Prager, Jens A1 - Kreutzbruck, Marc T1 - Acoustic wave energy skewing and coefficients for the reflected and transmitted plane waves in general homogeneous transversely-isotropic austenitic materials N2 - In this contribution a simulation tool is developed to compute the energy skewing angles and energy coefficients for the reflected and refracted plane waves in following general cases: (1) reflection and refraction of plane elastic waves at an interface between isotropic and transversely isotropic solid, (2) reflection and refraction of plane elastic waves at an interface between transversely isotropic and isotropic solid, (3) reflection and refraction of plane elastic waves at an interface between two general transversely isotropic solid and (4) reflection of plane elastic waves from a stress free boundary of a transversely isotropic solid. Computational results for analytically evaluated acoustic wave energy skewing angles and energy reflection and transmission coefficients in acoustically anisotropic materials such as austenitic steel materials exhibiting columnar grain orientation are presented. The obtained results show that the acoustic energy skewing angles and coefficients in austenitic steel materials strongly depend upon the columnar grain orientation and are less influenced by the grain orientations which are parallel and perpendicular to the interface. T2 - 8th International conference on NDE in relation to structural integrity for nuclear and pressurised components CY - Berlin, Germany DA - 2010-09-29 KW - Anisotropy KW - Austenitic weld material KW - Energy skewing KW - Critical angle KW - Energy flux vector KW - Energy coefficients PY - 2010 SN - 978-3-940283-30-6 IS - DGZfP-BB 125 (Th.1.C.3) SP - 1 EP - 10 CY - Berlin AN - OPUS4-25232 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Harrer, Andrea A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Guderian, Matthias A1 - Meyer-Plath, Asmus T1 - Erzeugung von Luftultraschall mit mikro- und nanostrukturierten Kohlenstoffmaterialien unter Ausnutzung des thermoakustischen Prinzips N2 - In diesem Beitrag wird ein neuartiger Ansatz zur Erzeugung von Luftultraschall vorgestellt, der auf dem thermoakustischen Prinzip beruht. Mikro- und nanostrukturierte Kohlenstoffmaterialien werden dabei mit einem harmonischen Wechselstrom gespeist und erfahren durch ohmsche Verluste eine Temperaturänderung, die sich auf das umgebende Fluid überträgt. Daraus resultieren Druckmodulationen, und es wird eine ausbreitungsfähige Schallwelle erzeugt. Dabei tritt Frequenzverdopplung gegenüber der Anregungsfrequenz auf. Es konnte gezeigt werden, dass der entscheidende Parameter für die Effizienz der Methode, d.h. für ein möglichst großes Verhältnis von Schalldruck zu eingebrachter Leistung, die Wärmekapazität pro Flächeneinheit ist. Da dieser Quotient für Kohlenstoffmaterialien sehr klein sein kann, erlaubt das thermoakustische Prinzip hier die effiziente Erzeugung von Luftultraschall. Schalldruckmessungen an verschiedenen Materialproben wurden bis 100 kHz mit einem Mikrofon durchgeführt, oberhalb von 100 kHz wurde eine laservibrometrische Schnellemessung eingesetzt. In experimentellen Untersuchungen wurde die Schallerzeugung in Abhängigkeit der Materialeigenschaften analysiert und systematisiert. Die experimentellen Ergebnisse wurden mit numerischen und analytischen Berechnungsergebnissen verglichen. T2 - DAGA 2011 - 37. Jahrestagung für Akustik - Fortschritte der Akustik CY - Düsseldorf, Germany DA - 21.03.2011 KW - Thermoakustisches Prinzip KW - Luftultraschall KW - Kohelnstoffmaterialien PY - 2011 SN - 978-3-939296-02-7 SP - 339 EP - 340 AN - OPUS4-25328 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kolkoori, Sanjeevareddy A1 - Shokouhi, Parisa A1 - Höhne, Christian A1 - Rahman, Mehbub-Ur A1 - Kreutzbruck, Marc A1 - Prager, Jens T1 - A comparative study of ray tracing and CIVA simulation for ultrasonic examination of anisotropic inhomogeneous austenitic welds N2 - Ultrasonic examination of anisotropic inhomogeneous austenitic welds is challenging, because of the columnar grain structure of the weld leads to beam skewing and splitting. Modeling tools play an important role in understanding the ultrasound field propagation and optimization of experimental parameters during the ultrasonic testing of austenitic welds as well as the interpretation of the test results. In this contribution, an efficient theoretical model based on the ray tracing concepts is developed to calculate the ultrasonic fields in inhomogeneous austenitic welds quantitatively. The developed model determines the ultrasound fields by taking into account the directivity of the ray source, the inhomogenity of the weld as well as ray transmission coefficients. Directivity of the ray source in columnar grained austenitic materials (including layback orientation) is obtained in three dimensions based on Lamb's reciprocity theorem. Ray energy reflection and transmission coefficients at an interface between two general columnar grained austenitic materials are calculated in three dimensions. The ray tracing model predictions on inhomogeneous austenitic weld material are compared against those from CIVA, a commercial non-destructive modeling and simulation tool. The ultrasonic modeling tools in CIVA are based on semi-analytical solutions. For beam propagation simulation, a so-called 'pencil method' is used, which involves modeling the probe as a set of individual source points, each radiating 'a bundle' of diverging rays into the medium and integrating those elementary contributions. Inhomogenity in the weld region is approximated by mapping the grain orientations on weld macrograph. Simulation results for ultrasonic field profiles for an austenitic weld are shown to be in good agreement with the corresponding experimental results. T2 - 39th Annual review of progress in quantitative nondestructive evaluation CY - Denver, Colorado, USA DA - 15.07.2012 KW - Crystal microstructure KW - Ray tracing KW - Ultrasonic materials testing KW - Ultrasonic propagation KW - Ultrasonic reflection KW - Ultrasonic transmission KW - Welds PY - 2013 SN - 978-0-7354-1129-6 DO - https://doi.org/10.1063/1.4789158 SN - 0094-243X SN - 1551-7616 N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings VL - 1511 SP - 1043 EP - 1050 PB - AIP Publishing AN - OPUS4-27736 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 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 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 - 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 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 - 15.07.2012 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 - Prager, Jens A1 - Kitze, Jessica A1 - Acheroy, Cécile A1 - Brackrock, Daniel A1 - Brekow, Gerhard A1 - Kreutzbruck, Marc T1 - SAFT and TOFD - A comparative study of two defect sizing techniques on a reactor pressure vessel mock-up N2 - Defect sizing is required for a quantitative assessment of the quality and reliability of safety relevant components and materials using ultrasonic non-destructive testing. The SAFT (Synthetic Aperture Focussing Technique) and the TOFD technique (Time Of Flight Diffraction) are such promising sizing candidates, extracting more information from the raw ultrasound echo data and the corresponding crack tip response. In this work the phased array technique is used to inspect a clad mock-up model of a pressure vessel section. The full scale model contains artificial test reflectors which are located in the weld and in the cladding region as well. The defects—representing typical flaws at a very early stage—are analysed with different frequencies, beam angles and directions of incidence. For the reconstruction of reflector indications a SAFT algorithm is applied to the phased array measurement results. Additionally the reflectors are analysed by means of the TOFD technique, using different beam angles at the same time. Both analysis methods are performed using different directions of incidence considering the complex cladding structure underneath the inner surface of the mock-up model. A direct comparison of the SAFT and TOFD techniques shows that, besides the clarity of the results, the detection and sizing capabilities of SAFT are far better. KW - Ultrasonic inspection KW - Phased array probe KW - Synthetic aperture focussing technique KW - Time of flight diffraction method PY - 2013 DO - https://doi.org/10.1007/s10921-012-0153-9 SN - 0195-9298 SN - 1573-4862 VL - 32 IS - 1 SP - 1 EP - 13 PB - Plenum Press CY - New York, NY AN - OPUS4-29277 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 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 - JOUR A1 - Kolkoori, Sanjeevareddy A1 - Höhne, Christian A1 - Prager, Jens A1 - Rethmeier, Michael A1 - Kreutzbruck, Marc T1 - Quantitative evaluation of ultrasonic C-scan image in acoustically homogeneous and layered anisotropic materials using three dimensional ray tracing method N2 - Quantitative evaluation of ultrasonic C-scan images in homogeneous and layered anisotropic austenitic materials is of general importance for understanding the influence of anisotropy on wave fields during ultrasonic non-destructive testing and evaluation of these materials. In this contribution, a three dimensional ray tracing method is presented for evaluating ultrasonic C-scan images quantitatively in general homogeneous and layered anisotropic austenitic materials. The directivity of the ultrasonic ray source in general homogeneous columnar grained anisotropic austenitic steel material (including layback orientation) is obtained in three dimensions based on Lamb's reciprocity theorem. As a prerequisite for ray tracing model, the problem of ultrasonic ray energy reflection and transmission coefficients at an interface between (a) isotropic base material and anisotropic austenitic weld material (including layback orientation), (b) two adjacent anisotropic weld metals and (c) anisotropic weld metal and isotropic base material is solved in three dimensions. The influence of columnar grain orientation and layback orientation on ultrasonic C-scan image is quantitatively analyzed in the context of ultrasonic testing of homogeneous and layered austenitic steel materials. The presented quantitative results provide valuable information during ultrasonic characterization of homogeneous and layered anisotropic austenitic steel materials. KW - Ultrasonic non-destructive evaluation KW - Ultrasonic C-scan image KW - Anisotropic austenitic steel KW - 3D ray tracing KW - Directivity PY - 2014 DO - https://doi.org/10.1016/j.ultras.2013.08.007 SN - 0041-624x VL - 54 IS - 2 SP - 551 EP - 562 PB - Elsevier CY - Amsterdam AN - OPUS4-29733 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kolkoori, Sanjeevareddy A1 - Rahman, Mehbub-Ur A1 - Chinta, P.K. A1 - Kreutzbruck, Marc A1 - Rethmeier, Michael A1 - Prager, Jens T1 - Ultrasonic field profile evaluation in acoustically inhomogeneous anisotropic materials using 2D ray tracing model: Numerical and experimental comparison N2 - Ultrasound propagation in inhomogeneous anisotropic materials is difficult to examine because of the directional dependency of elastic properties. Simulation tools play an important role in developing advanced reliable ultrasonic non destructive testing techniques for the inspection of anisotropic materials particularly austenitic cladded materials, austenitic welds and dissimilar welds. In this contribution we present an adapted 2D ray tracing model for evaluating ultrasonic wave fields quantitatively in inhomogeneous anisotropic materials. Inhomogeneity in the anisotropic material is represented by discretizing into several homogeneous layers. According to ray tracing model, ultrasonic ray paths are traced during its energy propagation through various discretized layers of the material and at each interface the problem of reflection and transmission is solved. The presented algorithm evaluates the transducer excited ultrasonic fields accurately by taking into account the directivity of the transducer, divergence of the ray bundle, density of rays and phase relations as well as transmission coefficients. The ray tracing model is able to calculate the ultrasonic wave fields generated by a point source as well as a finite dimension transducer. The ray tracing model results are validated quantitatively with the results obtained from 2D Elastodynamic Finite Integration Technique (EFIT) on several configurations generally occurring in the ultrasonic non destructive testing of anisotropic materials. Finally, the quantitative comparison of ray tracing model results with experiments on 32 mm thick austenitic weld material and 62 mm thick austenitic cladded material is discussed. KW - Ultrasonic field KW - 2D ray tracing KW - Directivity KW - Anisotropic austenitic weld KW - Non-destructive testing PY - 2013 DO - https://doi.org/10.1016/j.ultras.2012.07.006 VL - 53 IS - 2 SP - 396 EP - 411 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-27324 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kolkoori, Sanjeevareddy A1 - Rahman, Mehbub-Ur A1 - Chinta, P.K. A1 - Kreutzbruck, Marc A1 - Prager, Jens ED - Thompson, D. O. ED - Chimenti, D. E. T1 - Quantitative evaluation of ultrasonic sound fields in anisotropic austenitic welds using 2D ray tracing model N2 - Ultrasonic investigation of inhomogeneous anisotropic materials such as austenitic welds is complicated because its columnar grain structure leads to curved energy paths, beam splitting and asymmetrical beam profiles. A ray tracing model has potential advantage in analyzing the ultrasonic sound field propagation and there with optimizing the inspection parameters. In this contribution we present a 2D ray tracing model to predict energy ray paths, ray amplitudes and travel times for the three wave modes quasi longitudinal, quasi shear vertical, and shear horizontal waves in austenitic weld materials. Inhomogenity in the austenitic weld material is represented by discretizing the inhomogeneous region into several homogeneous layers. At each interface between the layers the reflection and transmission problem is computed and yields energy direction, amplitude and energy coefficients. The ray amplitudes are computed accurately by taking into account directivity, divergence and density of rays, phase relations as well as transmission coefficients. Ultrasonic sound fields obtained from the ray tracing model are compared quantitatively with the 2D Elastodynamic Finite Integration Technique (EFIT). The excellent agreement between both models confirms the validity of the presented ray tracing results. Experiments are conducted on austenitic weld samples with longitudinal beam transducer as transmitting probe and amplitudes at the rear surface are scanned by means of electrodynamical probes. Finally, the ray tracing model results are also validated through the experiments. T2 - 38th Annual Review of Progress in Quantitative Nondestructive Evaluation CY - Burlington, VT, USA DA - 17.07.2011 KW - Ultrasonic sound field KW - Ray tracing KW - Ray directivity KW - Austenitic weld PY - 2012 SN - 978-0-7354-1013-8 DO - https://doi.org/10.1063/1.4716359 SN - 0743-0760 SN - 0094-243X N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings IS - 1430 SP - 1227 EP - 1234 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-26205 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 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 - Kreutzbruck, Marc A1 - Prager, Jens A1 - Boehm, Rainer A1 - Kitze, Jessica A1 - Brekow, Gerhard T1 - Progress in acoustical defect sizing NDT methods for the inspection of power-plant components N2 - The demand of improved NDT methods with proper visualization and sizing capabilities is a persistent trend in maintenance and manufacturing quality inspection. Especially when dealing with high quality standards in conjunction with safety-critical components in the sector of energy and transportation quantitative NDT techniques are vital to provide reliable quality control systems and a corresponding deeper insight into the component structure for a further fracture-mechanical estimation. The paper thus focuses the progress of the defect sizing capabilities of modern Ultrasonic Testing (UT). In Ultrasonic Testing the SAFT-algorithm (Synthetic Aperture Focusing Technique) currently experiences a renaissance. The method is based on combining the data of different transducer positions with their corresponding varied propagating time and it is currently applied in several industrial applications. SAFT enhances the SNR and the spatial resolution and is thus a valuable tool when it comes to improved defect detection and sizing. A tomographic-like data mapping is illustrated on several examples, where adapted phased array systems were used for the inspection of turbine components and also for a cladded mock-up of a nuclear reactor pressure vessel. In a statistical investigation we also performed a comparison with other defect sizing methods like TOFD (Time of flight diffraction). T2 - 18th WCNDT - World conference on nondestructive testing CY - Durban, South Africa DA - 16.04.2012 KW - SAFT KW - TOFD KW - Cracks KW - Phased Array PY - 2012 SN - 978-0-620-52872-6 SP - 1 EP - 8 (Paper 497) AN - OPUS4-26350 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -