TY - CONF A1 - Bühling, Benjamin T1 - Entwicklung eines luftgekoppelten Ultraschall-Echo-Prüfverfahrens mittels fluidischer Anregung N2 - In vielen technischen Bereichen werden Ultraschallverfahren zur zerstörungsfreien Werkstoffprüfung (ZfP) eingesetzt um auf Basis der Signalstärke und der Laufzeit Einbauteile und Beschädigungen zu orten. Luftgekoppelter Ultraschall spielt bisher in kommerziellen Anwendungen vor Allem im Bauwesen eine untergeordnete Rolle, da die Differenz der akustischen Impedanzen von Luft und Festkörpern immense Verluste beim Übergang des Schallsignals hervorruft. Im Rahmen des Promotionsvorhabens soll die Eignung eines neuartigen Anregungsprinzip untersucht werden, mit dem ein Großteil dieser Verluste vermieden werden soll. Anstelle eines Festkörpers soll mit Hilfe einer fluidischen Düse Druckluft zur Signalerzeugung eingesetzt werden. Die Impedanzverluste zwischen Aktuatormembran und Umgebungsluft entfallen daher. Die gezielte Schallerzeugung durch einen pulsierenden Freistrahl ist weitgehend unerforscht. Es ist daher notwendig, den so erzeugten Schallpuls in der Interaktion mit dem transienten Strömungsfeld zu untersuchen. Das kompressible Medium Luft und die geringen räumlichen Dimensionen einer hochfrequenten Pulsdüse werfen darüber hinaus einige Herausforderungen hinsichtlich der eingesetzten Messtechnik auf. Hier sollen geeignete Verfahren weiterentwickelt und validiert werden, um die Eignung des fluidisch erzeugten Pulses zu überprüfen. In diesem Vortrag werden erste Messungen an einem fluidischen Schalter mit denen an einem kommerziellen Luftultraschallprüfkopf verglichen. T2 - Doktorandenseminar BAM Abt. 8 CY - Berlin, Germany DA - 17.02.2020 KW - ZfP KW - Ultraschall KW - NDT KW - Ultrasound KW - Air-coupled KW - Non-Contact KW - Luftgekoppelt KW - Kontaktlos PY - 2020 AN - OPUS4-51120 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Aßmann, Norman A1 - Bühling, Benjamin T1 - Impact-echo dataset "Radarplatte" N2 - This dataset contains raw data resulting from Impact-Echo measurements at the reference conrete block "Radarplatte", located at BAM (German Federal Institute for Materials Research and Testing). This specimen has been described in detail by Niederleithinger et al. (2021), who applied muon tomography, ultrasonic echo measurements, radar and X-ray laminography to visualize its internal structure. The Impact-Echo method is based on the excitation of the zero-group-velocity frequency of the first symmetric Lamb mode of a plate-like structure, in order to assess its thickness. Numerous publication elaborate on Impact-Echo theory, examples are (Gibson and Popovics 2005, Schubert and Köhler 2008 , Abraham and Popovics 2010). The measurements have been conducted using a setup that contains only commercially available components. The setup consists of an Olson CTG-2 concrete thickness gauge (Olsen Instruments, USA) for actuation and sensing and an 8-bit NI USB-5132 digital storage oscilloscope (National Instruments, USA) combined with the Echolyst software (Schweizerischer Verein für technische Inspektionen (SVTI), Switzerland) for data acquisition. Measurements were conducted using a grid of 23x23 points with a spacing of 50 mm. At each point 8192 samples were recorded at a sampling rate of 1 MS/s. The dataset contains the (X,Y) location in mm of the individual measurement points as well as the raw measurement data at those points. The data is provided in the formats *.mir/*.mhdr (Echolyst), *.npy (Python) and *.mat (Matlab) and *.csv to ease the import in various post-processing tools. KW - Nondestructive testing KW - Impact-echo KW - S1-ZGV mode KW - Concrete PY - 2021 DO - https://doi.org/10.7910/DVN/UNOH2U PB - Harvard College CY - Cambridge, MA, USA AN - OPUS4-53886 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Grotelüschen, Bjarne A1 - Bühling, Benjamin T1 - Impact-Echo Dataset "IE Platte" N2 - This dataset contains raw data resulting from Impact-Echo measurements at the reference concrete block "IE Platte", located at BAM (German Federal Institute for Materials Research and Testing). The specimen contains three polystyrene slabs and one polyethylene foil to act as reflectors. The specimen was produced in a three-step process. First, the base plate was cast. Second, the reflectors were taped to the base plate. Finally, the upper layer was cast on top of base plate and reflectors. A drawing is contained in the dataset. The Impact-Echo method is based on the excitation of the zero-group-velocity frequency of the first symmetric Lamb mode of a plate-like structure, in order to assess its thickness. Numerous publications elaborate on Impact-Echo theory, examples are (Gibson and Popovics 2005, Schubert and Köhler 2008 , Abraham and Popovics 2010). The measurements have been conducted using a setup that contains only commercially available components. The setup consists of an Olson CTG-2 concrete thickness gauge (Olsen Instruments, USA) for actuation and sensing and an 8-bit NI USB-5132 digital storage oscilloscope (National Instruments, USA) combined with the Echolyst software (Schweizerischer Verein für technische Inspektionen (SVTI), Switzerland) for data acquisition. Measurements were conducted using a grid of 29x29 points with a spacing of 50 mm. At each point 8192 samples were recorded at a sampling rate of 1 MS/s. The dataset contains the (X,Y) location in mm of the individual measurement points as well as the raw measurement data at those points. The data is provided in the formats *.mir/*.mhdr (Echolyst), *.npy (Python) and *.mat (Matlab) and *.csv to ease the import in various post-processing tools. KW - Concrete KW - Impact-Echo KW - Nondestructive testing PY - 2022 DO - https://doi.org/10.7910/DVN/EH4E9G PB - Harvard College CY - Cambridge, MA, USA AN - OPUS4-55279 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin A1 - Maack, Stefan A1 - Strangfeld, Christoph T1 - OsciCheck - A Novel Fluidic Transducer for Air-Coupled Ultrasonic Measurements N2 - Ultrasonic measurement technology has become indispensable in NDT-CE. Air-coupled ultrasonic (ACU) measurement techniques promise to reduce measurement time. However, the signal quality suffers from large specific impedance mismatch at the transducer-air and air-specimen interface. Additionally, large pressure amplitudes are necessary for the penetration depth required in NDT-CE applications. To address the specific requirements of ultrasonic testing in NDT-CE, a robust ACU transducer was developed, that generates ultrasound by quickly switching a pressurized air flow. The simple design of the fluidic transducer makes the device maintenance free and resilient against harsh environmental conditions. Since the signal is generated by aeroacoustics, there is no specific impedance mismatch between the transducer and the surrounding air. The ultrasonic signal exhibits frequencies in the 30-60 kHz range and is therefore well suited to penetrate heterogenous materials such as concrete. This contribution gives an introduction in the working principle and signal characteristics of the fluidic transducer. Its applicability to measurements in concrete is verified. A detailed outlook is given to discuss the future potential of fluidic ultrasonic actuators. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Air-coupled ultrasound KW - Nondestructive testing KW - Fluidics KW - Bistable amplifier KW - Aeroacoustics PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-555271 UR - https://www.ndt.net/search/docs.php3?id=27319 VL - 2022/09 SP - 1 EP - 9 PB - NDT.net CY - Bad Breisig AN - OPUS4-55527 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Maack, Stefan A1 - Küttenbaum, Stefan A1 - Bühling, Benjamin T1 - Low-frequency ultrasound data (pulse-echo technique) with shear horizontal and longitudinal waves on the step-shaped concrete specimen “Pk050” N2 - This dataset contains raw data acquired in ultrasound measurements on a reference specimen made of concrete at Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin (Germany). The internal specimen identifier is “Pk050”. The measurements were conducted using the pulse-echo method. The upper surface of the specimen was defined as measuring area. The aim of the measurements is to determine the geometrical dimensions (thickness) of the specimen “Pk050”. In addition to this, a dataset of a second specimen with identifier “Pk266” has been acquired. Pk266 has the same geometrical dimensions and concrete recipe as Pk050, but contains tendons [Reference: https://doi.org/10.7910/DVN/NUU0WZ]. KW - Ultrasound KW - Pulse echo method KW - Synthetic Aperture Focusing Technique KW - Validation KW - Elastic wave PY - 2023 DO - https://doi.org/10.7910/DVN/9EID5D PB - Harvard College CY - Cambridge, MA, USA AN - OPUS4-57231 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph A1 - Bühling, Benjamin A1 - Maack, Stefan T1 - OsciCheck - A novel fluidic transducer for air coupled ultrasonic measurements N2 - Ultrasonic measurement technology has become indispensable in NDT-CE. Air-coupled ultrasonic (ACU) measurement techniques promise to reduce measurement time. However, the signal quality suffers from large specific impedance mismatch at the transducer-air and air-specimen interface. Additionally, large pressure amplitudes are necessary for the penetration depth required in NDT-CE applications. To address the specific requirements of ultrasonic testing in NDT-CE, a robust ACU transducer was developed, that generates ultrasound by quickly switching a pressurized air flow. The simple design of the fluidic transducer makes the device maintenance free and resilient against harsh environmental conditions. Since the signal is generated by aeroacoustics, there is no specific impedance mismatch between the transducer and the surrounding air. The ultrasonic signal exhibits frequencies in the 30-60 kHz range and is therefore well suited to penetrate heterogenous materials such as concrete. This contribution gives an introduction in the working principle and signal characteristics of the fluidic transducer. A detailed outlook is given to discuss the future potential of fluidic ultrasonic actuators. T2 - International Symposium Non-Destructive Testing in Civil Engineering CY - Zurich, Switzerland DA - 16.08.2022 KW - Air-coupled ultrasound KW - Nondestructive testing KW - Fluidics KW - Bistable amplifier KW - Aeroacoustics PY - 2022 AN - OPUS4-55529 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Maack, Stefan A1 - Küttenbaum, Stefan A1 - Bühling, Benjamin T1 - Low-frequency ultrasound data (pulse-echo technique) with shear horizontal and longitudinal waves on the step-shaped concrete specimen “Pk266” with tendons N2 - This dataset contains raw data acquired in ultrasound measurements on a reference specimen made of concrete at Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin (Germany). The internal specimen identifier is “Pk266”. The measurements were conducted using the pulse-echo method. The upper surface of the specimen was defined as measuring area. The aim of the measurements is to determine both the geometrical dimensions (thickness) and the position of tendons to the measuring area. In addition to this, a second dataset of a second specimen with identifier is existing named “Pk050” has been acquired. Pk050 has the same geometrical dimensions and concrete recipe as Pk266 recipe but does not contain tendons [Reference: https://doi.org/10.7910/DVN/9EID5D]. KW - Ultrasound KW - Pulse echo method KW - Synthetic Aperture Focusing Technique KW - Validation KW - Elastic wave PY - 2023 DO - https://doi.org/10.7910/DVN/NUU0WZ PB - Harvard College CY - Cambridge, MA, USA AN - OPUS4-57232 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin T1 - OsciCheck - Fluidic Generation of Ultrasound N2 - The OsciCheck project is presented. The working principle and sound field of a fluidic switch is described. Future goals of the project are presented. T2 - CoDA Summer School 2020 CY - Berchtesgaden, Germany DA - 28.09.2020 KW - Fluidic Switch KW - Air-coupled ultrasound KW - Ultrasound KW - Non-destructive testing KW - Fluidischer Schalter KW - Luftgekoppelter Ultraschall KW - Ultraschall KW - Zerstörungsfreie Prüfung PY - 2020 AN - OPUS4-51380 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Bühling, Benjamin T1 - Acoustic and flow data of an ultrasonic fluidic switch and an ultrasonic piezoelectric transducer N2 - This dataset contains acoustic and flow data of an ultrasonic fluidic switch, which have been acquired using a microphone, a hot-wire anemometer and a pitot tube. Furthermore, acoustic data of a commercial piezoelectric transducer is provided. KW - Fluidics KW - Air-coupled ultrasound KW - Ultrasound KW - Non-destructive testing KW - Acoustic-flow interaction KW - Piezoelectric transducer PY - 2020 DO - https://doi.org/10.7910/DVN/OQYPC9 PB - Harvard College CY - Cambridge, MA, USA AN - OPUS4-52392 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin A1 - Schweitzer, T. A1 - Maack, Stefan A1 - Strangfeld, Christoph T1 - Influence of operating conditions on the fluidic ultrasonic transducer signal N2 - While contact and immersion ultrasonic testing are established methods in non-destructive testing (NDT), generating high power air-coupled ultrasound remains a challenging task. Solutions often involve setups that are restricted to lab environments. When field measurements are required, such as in NDT for civil engineering, a handy, robust and safe transducer is needed. For this purpose, an ultrasonic transducer based on a fluidic switch has been developed. A sonic air flow inside the device is switched rapidly so that an ultrasonic signal is generated. Both theory and previous flow simulations suggest that the control flow pressure ramp has only little influence on the switching time of the device. This publication gives an overview over the operating principle of the fluidic ultrasonic transducer and investigates the influence of control tube length and pulsing repetition rate on the ultrasonic pressure amplitude. High repetition rates are found to reduce the signal amplitude, whereas long tubing has only little negative influence on the amplitude while improving signal quality. T2 - 47. Jahrestagung für Akustik (DAGA 2021) CY - Vienna, Austria DA - 15.08.2021 KW - Ultrasound KW - Non-destructive testing KW - Fluidic devices PY - 2021 UR - https://pub.dega-akustik.de/DAGA_2021 SN - 978-3-939296-18-8 SP - 48 EP - 51 CY - Berlin, Germany AN - OPUS4-53493 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin T1 - Recent Developments of Fluidic Ultrasonic Transducers at BAM N2 - Ultrasonic measurement technology has become indispensable in NDT. In order to reduce measurement time and extend the application to other materials, contactless ultrasound is the subject of many different research groups. Department 8 has been researching successfully in this field for years. A novel approach is based on so-called fluidic devices. These devices can be used to perform binary logic operations with the help of natural flow instabilities. Hence the abbreviated name, Fluidic (FLUID+LogIC). Only a pressure reservoir of the used fluid is required as energy supply. This enables the production of very robust actuators that generate ultrasonic signals in an extremely energy efficient way. The presentation includes the research results of the ZIM innovation project OsciCheck. The original idea will be presented and its application on different building materials is validated. Beyond this, the possible application areas are much larger and a detailed outlook is given to discuss the future potential of fluidic ultrasonic actuators. T2 - Abteilungsseminar Abteilung 8 CY - Berlin, Germany DA - 23.09.2021 KW - Uultrasound KW - Non-destructive testing KW - Fluidic devices KW - Hydrogen KW - Ranging KW - Harsh environments PY - 2021 AN - OPUS4-53356 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin T1 - Influence of Operating Conditions on the Fluidic Ultrasonic Transducer Signal N2 - Motivation: • Air-coupled ultrasound (AC-US) enables faster measurements in non-destructive testing for civil engineering • Current state of the art: piezo and capacitive transducers are mostly used for AC US • Currently >99.9% sound intensity loss due to impedance mismatches Innovation: • Fluidic transducers generate US (30-60 kHz) by rapid switching of a supersonic jet • Fluidic transducers rely on external components such as solenoid valves and tubing --> How do repetition time and tube length influence the signal? T2 - DAGA 2021 CY - Vienna, Austria DA - 15.08.2021 KW - Ultrasound KW - Non-destructive testing KW - Fluidic devices PY - 2021 AN - OPUS4-53408 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin T1 - Using a spectral entropy criterion for improved onset picking in ultrasonic testing N2 - In ultrasonic testing, the time of flight (ToF) of a signal can be used to infer material and structural properties of a test item. In dispersive media, extracting the bulk wave velocity from a received signal is challenging as the waveform changes along its path of propagation. When using signal features such as the first peak or the envelope maximum, the calculated velocity changes with the propagation distance. This does not occur when picking the signal onset. Borrowing from seismology, researchers used the Akaike information criterion (AIC) picker to automatically obtain onset times. In addition to being dependent on arbitrarily set parameters, the AIC picker assumes no prior knowledge of the spectral properties of the signal. This is unnecessary in ultrasonic through-transmission testing, where the signal spectrum is known to differ significantly from noise. In this contribution, a novel parameter-free onset picker is proposed, that is based on a spectral entropy criterion (SEC) to model the signal using the AIC framework. Synthetic and experimental data are used to compare the performance of SEC and AIC pickers, showing an improved accuracy for densely sampled data. T2 - 183rd Meeting of the Acoustical Society of America CY - Nashville, TN, USA DA - 05.12.2022 KW - ToF KW - Arrival time KW - Nondestructive testing KW - Through-transmission KW - AIC picker PY - 2022 AN - OPUS4-56616 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin A1 - Strangfeld, Christoph A1 - Maack, Stefan T1 - Entwicklung eines luftgekoppelten Ultraschall-Echo-Prüfverfahrens mittels fluidischer Anregung N2 - In vielen technischen Bereichen werden Ultraschallverfahren zur zer-störungsfreien Werkstoffprüfung eingesetzt. Dabei wird ein Schallpuls von einem Prüfkopf in ein Prüfobjekt eingebracht. Der Puls kann unter anderem durch Membra-nen oder Piezoelemente erzeugt werden und wird in der Regel durch direkten Kontakt oder über ein Koppelmittel an das Objekt übertragen. Luftgekoppelter Ultraschall spielt in kommerziellen Anwendungen bisher eine untergeordnete Rolle, da die Dif-ferenz der akustischen Impedanzen von Luft und Festkörpern immense Verluste beim Übergang des Schallsignals hervorruft. In diesem Beitrag soll ein neuartiges Anregungsprinzip vorgestellt werden, mit dem ein Großteil dieser Verluste vermieden wird. Anstelle eines Festkörpers soll mit Hilfe einer fluidischen Düse Druckluft zur Signalerzeugung eingesetzt werden. In die-ser Düse wird eine selbsterhaltende Strömungsinstabilität erzeugt, die einen Schall-puls von bis zu 100 kHz hervorruft, sodass der Impedanzverlust in die Umgebungsluft entfällt. Da die charakteristische Frequenz eines fluidisch generierten Pulses maßgeb-lich von der Bauform der Düse und dem anliegenden Druck abhängt, lässt sich mittels einer geeigneten Strömungsregelung ein breiter Frequenzbereich zur Abtastung nut-zen. Die so emittierten Pulse werden auf das Prüfobjekt gerichtet und die reflektierten Signale mit einem Laservibrometer an der Oberfläche des Objekts im Echo-Verfahren abgetastet. Von drei signalmindernden Materialübergängen bei gewöhnlichem luftge-koppeltem Ultraschall bleibt in dem hier vorgeschlagenen Messystem lediglich die Grenzfläche von Luft zu Prüfkörper, sodass eine höhere Signalausbeute als bisher er-wartet werden kann. T2 - DACH-Jahrestagung 2019 CY - Friedrichshafen, Germany DA - 27.05.2019 KW - Ultraschall KW - Ultrasound KW - Air-coupled KW - Luftgekoppelt KW - Fluidic oscillator KW - Fluidischer Oszillator KW - Laser-Doppler-Vibrometer KW - Refraktovibrometrie KW - Refracto-vibrometry KW - NDT KW - ZfP PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-481207 VL - 2019 SP - 1 EP - 8 PB - DGZfP Deutsche Gesellschaft für Zerstörungsfreie Prüfung AN - OPUS4-48120 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin T1 - Entwicklung eines luftgekoppelten Ultraschall-Echo-Prüfverfahrens mittels fluidischer Anregung N2 - In vielen technischen Bereichen werden Ultraschallverfahren zur zerstörungsfreien Werkstoffprüfung eingesetzt. Dabei wird ein Schallpuls von einem Prüfkopf in ein Prüfobjekt eingebracht. Der Puls kann unter anderem durch Membranen oder Piezoelemente erzeugt werden und wird in der Regel durch direkten Kontakt oder über ein Koppelmittel an das Objekt übertragen. Luftgekoppelter Ultraschall spielt in kommerziellen Anwendungen bisher eine untergeordnete Rolle, da die Differenz der akustischen Impedanzen von Luft und Festkörpern immense Verluste beim Übergang des Schallsignals hervorruft. In diesem Beitrag soll ein neuartiges Anregungsprinzip vorgestellt werden, mit dem ein Großteil dieser Verluste vermieden wird. Anstelle eines Festkörpers soll mit Hilfe einer fluidischen Düse Druckluft zur Signalerzeugung eingesetzt werden. In dieser Düse wird eine selbsterhaltende Strömungsinstabilität erzeugt, die einen Schallpuls von bis zu 100 kHz hervorruft, sodass der Impedanzverlust in die Umgebungsluft entfällt. Da die charakteristische Frequenz eines fluidisch generierten Pulses maßgeblich von der Bauform der Düse und dem anliegenden Druck abhängt, lässt sich mittels einer geeigneten Strömungsregelung ein breiter Frequenzbereich zur Abtastung nutzen. Die so emittierten Pulse werden auf das Prüfobjekt gerichtet und die reflektierten Signale mit einem Laservibrometer an der Oberfläche des Objekts im Echo-Verfahren abgetastet. Von drei signalmindernden Materialübergängen bei gewöhnlichem luftgekoppeltem Ultraschall bleibt in dem hier vorgeschlagenen Messystem lediglich die Grenzfläche von Luft zu Prüfkörper, sodass eine höhere Signalausbeute als bisher erwartet werden kann. T2 - Akustisches Seminar der TU Berlin CY - Berlin, Germany DA - 24.06.2019 KW - Luftgekoppelter Ultraschall KW - Ultrasound KW - Vibrometer PY - 2019 AN - OPUS4-48303 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin T1 - OsciCheck - Fluidische Erzeugung eines luftgekoppelten Ultraschallpulses N2 - Das ZIM-Projekt OsciCheck wird vorgestellt, die Funktionsweise eines fluidischen Oszillators erläutert und die nächsten Arbeitsschritte im Projekt dargestellt. T2 - Herbstworkshop der jungen DEGA CY - Berlin, Germany DA - 01.11.2019 KW - Fluidischer Oszillator KW - Ultraschall KW - Luftgekoppelter Ultraschall KW - Zerstörungsfreie Prüfung PY - 2019 AN - OPUS4-51294 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -