{"id":{"repo_id":"tu-berlin","oai_identifier":"oai:depositonce.tu-berlin.de:11303/21206"},"canonical_url":"https://search.dev.ndltd.org/etd/tu-berlin/oai:depositonce.tu-berlin.de:11303/21206","repository":{"repo_id":"tu-berlin","name":"Technische Universität Berlin","base_url":"https://api-depositonce.tu-berlin.de/server/oai/request"},"display":{"title":"Fluidic ultrasound generation for nondestructive testing","abstract":"Ultrasonic testing has become an indispensable method for verifying integrity, dimensional accuracy and material properties in numerous technical domains. Air-coupled ultrasound offers advantages in terms of measurement flexibility and reduced measurement time, but also presents challenges due to limitations in transmitted sound pressure amplitude and sensor positioning. Due to the high impedance mismatch at the interfaces between the transducer, air, and specimen, only a fraction of the generated sound pressure interacts with the specimen and is received by a sensor. To reduce these losses, a novel fluidic ultrasonic transducer is presented. This device produces a transient triggered ultrasound pulse based on aeroacoustic sound generation mechanisms in a bistable fluidic amplifier. Little is known about its performance characteristics and suitability for nondestructive testing (NDT). The publications included in this thesis are the first to present a transient aeroacoustic ultrasonic generator using a bistable fluidic amplifier. This dissertation demonstrates that such a fluidic ultrasonic transducer is applicable for common measurement tasks in NDT. By disseminating the acoustic and flow characteristics of the device, the resulting challenges and opportunities concerning its applicability to NDT tasks are identified and addressed. It is found that the generated pulse contains frequency components below 60 kHz, fluctuating in amplitude and phase delay, and is accompanied by a high velocity free jet that partially interacts with the sound pulses. In order to prevent interaction between the jet and the specimen surface and to increase transducer directivity, the attachment of sonic crystals and an exponential horn were successfully tested. The distinct spectral characteristics of each ultrasonic pulse were exploited to develop a signal processing approach that allows better differentiation between two pulses received in quick succession. This improved the usability of the fluidic transducer in multiple-input multiple-output (MIMO) setups. To address the stochastic ultrasound generation behavior, a novel, fully non-contact through-transmission measurement setup is presented that allows time-of-flight measurements without prior knowledge of trigger time, pulse shape, or distance between the transducer and the specimen. Successful measurement of longitudinal propagation velocity in various materials demonstrates that the fluidic transducer is capable of nondestructively measuring a variety of geometric and material properties. Thus, a new type of ultrasonic transducer has been established and its applicability to common NDT tasks has been demonstrated. The usability of these novel procedures extends beyond fluidic ultrasonic testing and can also be employed to improve conventional air-coupled ultrasonic measurements. The results presented not only offer the amplifier-based fluidic transducer as a robust alternative ultrasound source for NDT, especially in civil engineering, but also raise a number of research questions related to the use of aeroacoustic transducers as an alternative to conventional air-coupled ultrasonic devices.","abstract_html":"Ultrasonic testing has become an indispensable method for verifying integrity, dimensional accuracy and material properties in numerous technical domains. Air-coupled ultrasound offers advantages in terms of measurement flexibility and reduced measurement time, but also presents challenges due to limitations in transmitted sound pressure amplitude and sensor positioning. Due to the high impedance mismatch at the interfaces between the transducer, air, and specimen, only a fraction of the generated sound pressure interacts with the specimen and is received by a sensor. To reduce these losses, a novel fluidic ultrasonic transducer is presented. This device produces a transient triggered ultrasound pulse based on aeroacoustic sound generation mechanisms in a bistable fluidic amplifier. Little is known about its performance characteristics and suitability for nondestructive testing (NDT). The publications included in this thesis are the first to present a transient aeroacoustic ultrasonic generator using a bistable fluidic amplifier. This dissertation demonstrates that such a fluidic ultrasonic transducer is applicable for common measurement tasks in NDT. By disseminating the acoustic and flow characteristics of the device, the resulting challenges and opportunities concerning its applicability to NDT tasks are identified and addressed. It is found that the generated pulse contains frequency components below 60 kHz, fluctuating in amplitude and phase delay, and is accompanied by a high velocity free jet that partially interacts with the sound pulses. In order to prevent interaction between the jet and the specimen surface and to increase transducer directivity, the attachment of sonic crystals and an exponential horn were successfully tested. The distinct spectral characteristics of each ultrasonic pulse were exploited to develop a signal processing approach that allows better differentiation between two pulses received in quick succession. This improved the usability of the fluidic transducer in multiple-input multiple-output (MIMO) setups. To address the stochastic ultrasound generation behavior, a novel, fully non-contact through-transmission measurement setup is presented that allows time-of-flight measurements without prior knowledge of trigger time, pulse shape, or distance between the transducer and the specimen. Successful measurement of longitudinal propagation velocity in various materials demonstrates that the fluidic transducer is capable of nondestructively measuring a variety of geometric and material properties. Thus, a new type of ultrasonic transducer has been established and its applicability to common NDT tasks has been demonstrated. The usability of these novel procedures extends beyond fluidic ultrasonic testing and can also be employed to improve conventional air-coupled ultrasonic measurements. The results presented not only offer the amplifier-based fluidic transducer as a robust alternative ultrasound source for NDT, especially in civil engineering, but also raise a number of research questions related to the use of aeroacoustic transducers as an alternative to conventional air-coupled ultrasonic devices.","abstract_has_math":false,"creators":["Bühling, Benjamin"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Sarradj, Ennes","Strangfeld, Christoph","Maack, Stefan"],"committee_chairs":[],"committee_members":[],"year":2024,"date_issued":"2024","date_published":"2024","updated_at":"2026-07-27T21:28:26Z","subjects":[],"languages":["en"],"rights":[],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://doi.org/10.14279/depositonce-20006"],"render_values":[{"text":"https://doi.org/10.14279/depositonce-20006","href":"https://doi.org/10.14279/depositonce-20006","code":true}]}]},"links":{"outbound_url":"https://depositonce.tu-berlin.de/handle/11303/21206","outbound_label":"Repository record","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Sarradj, Ennes","Strangfeld, Christoph","Maack, Stefan"]},{"key":"dc:creator","label":"Author","values":["Bühling, Benjamin"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2024-04-03T12:34:27Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2024-04-03T12:34:27Z"]},{"key":"dc:date.issued","label":"Date","values":["2024"]},{"key":"dc:type","label":"Dc Type","values":["Doctoral Thesis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://depositonce.tu-berlin.de/handle/11303/21206","https://doi.org/10.14279/depositonce-20006"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Ultrasonic testing has become an indispensable method for verifying integrity, dimensional accuracy and material properties in numerous technical domains. Air-coupled ultrasound offers advantages in terms of measurement flexibility and reduced measurement time, but also presents challenges due to limitations in transmitted sound pressure amplitude and sensor positioning. Due to the high impedance mismatch at the interfaces between the transducer, air, and specimen, only a fraction of the generated sound pressure interacts with the specimen and is received by a sensor. To reduce these losses, a novel fluidic ultrasonic transducer is presented. This device produces a transient triggered ultrasound pulse based on aeroacoustic sound generation mechanisms in a bistable fluidic amplifier. Little is known about its performance characteristics and suitability for nondestructive testing (NDT). The publications included in this thesis are the first to present a transient aeroacoustic ultrasonic generator using a bistable fluidic amplifier. This dissertation demonstrates that such a fluidic ultrasonic transducer is applicable for common measurement tasks in NDT. By disseminating the acoustic and flow characteristics of the device, the resulting challenges and opportunities concerning its applicability to NDT tasks are identified and addressed. It is found that the generated pulse contains frequency components below 60 kHz, fluctuating in amplitude and phase delay, and is accompanied by a high velocity free jet that partially interacts with the sound pulses. In order to prevent interaction between the jet and the specimen surface and to increase transducer directivity, the attachment of sonic crystals and an exponential horn were successfully tested. The distinct spectral characteristics of each ultrasonic pulse were exploited to develop a signal processing approach that allows better differentiation between two pulses received in quick succession. This improved the usability of the fluidic transducer in multiple-input multiple-output (MIMO) setups. To address the stochastic ultrasound generation behavior, a novel, fully non-contact through-transmission measurement setup is presented that allows time-of-flight measurements without prior knowledge of trigger time, pulse shape, or distance between the transducer and the specimen. Successful measurement of longitudinal propagation velocity in various materials demonstrates that the fluidic transducer is capable of nondestructively measuring a variety of geometric and material properties. Thus, a new type of ultrasonic transducer has been established and its applicability to common NDT tasks has been demonstrated. The usability of these novel procedures extends beyond fluidic ultrasonic testing and can also be employed to improve conventional air-coupled ultrasonic measurements. The results presented not only offer the amplifier-based fluidic transducer as a robust alternative ultrasound source for NDT, especially in civil engineering, but also raise a number of research questions related to the use of aeroacoustic transducers as an alternative to conventional air-coupled ultrasonic devices.","Die Ultraschallprüfung hat sich in vielen technischen Bereichen zu einer unverzichtbaren Methode zur Überprüfung von Bauteilintegrität, Maßhaltigkeit und Materialeigenschaften entwickelt. Luftgekoppelter Ultraschall bietet Vorteile im Hinblick auf Flexibilität in der Durchführung der Messung und in der Verringerung der Messdauer. Herausforderungen bestehen hingegen sowohl aufgrund der geringeren eingebrachten Schalldruckamplituden als auch der erforderlichen Positionierungsgenauigkeit der Sensorik. Auf Grund des großen Unterschieds der spezifischen Schallimpedanzen an den Übergängen zwischen Schallwandler, Luft und Prüfkörper interagiert nur Bruchteil des erzeugten Schalldrucks mit dem Prüfkörper und wird im Anschluss vom Schallsensor empfangen. Um diese Verluste zu reduzieren, wird ein neuartiger fluidischer Ultraschallwandler vorgestellt. Basierend auf der aeroakustischen Schallerzeugung in einem fluidischen bistabilen Haftstrahlelement erzeugt dieses Gerät einen gesteuerten transienten Ultraschallpuls. Weder dessen Schallcharakteristik noch die Eignung zur zerstörungsfreien Prüfung (ZfP) wurden bisher erforscht. Die Publikationen dieser Dissertation sind die ersten, die Luftschallerzeugung durch fluidische Wandstrahlelemente untersuchen und die transiente Signalerzeugung mit Hilfe aeroakustischer Ultraschallwandler zeigen. In dieser Dissertation wird gezeigt, dass der fluidische Ultraschallwandler für übliche ZfP-Messverfahren geeignet ist. Mit der Untersuchung der Schall- und Strömungseigenschaften des Wandlers werden die Möglichkeiten und Herausforderungen für ZfP-Anwendungen herausgearbeitet. Es wird gezeigt, dass der durch den fluidischen Wandler erzeugte Puls dominante Frequenzen unter 60 kHz erzeugt, die stochastisch in Amplitude und Phase variieren, und mit einem Freistrahl nahe der Schallgeschwindigkeit einhergeht, der mit nachfolgenden Schallpulsen interagiert. Um die Interaktion dieses Freistrahls mit der Oberfläche eines Probekörpers zu verhindern und um die Richtcharakteristik des Wandlers zu verbessern, wurden das Anbringen eines Exponentialtrichters und der Einsatz sonischer Kristalle erfolgreich untersucht. Die spezifischen spektralen Eigenschaften der einzelnen Ultraschallpulse werden genutzt, um eine Signalverarbeitungsmethode zu entwickeln, durch die mehrere kurz aufeinanderfolgende Pulse besser unterschieden werden können und so Multiple-input Multiple-output (MIMO) Anwendungen mit Hilfe des fluidischen Wandlers möglich werden. Um dem stochastischen Verhalten des Schallerzeugungsmechanismus zu begegnen, wird ein neuartiger komplett berührungsloser Durchschallungsprüfstand vorgestellt, der erlaubt, die Laufzeit eines Ultraschallsignals zu messen, ohne dass der Trigger-Zeitpunkt, die Pulsform oder der Abstand zwischen Wandler und Probekörper bekannt sein müssen. Durch die erfolgreiche Messung der Longitudinalwellengeschwindigkeit in verschiedenen Materialien wird gezeigt, dass der fluidische Wandler geeignet ist, eine Reihe von Geometrie- und Materialeigenschaften zerstörungsfrei zu untersuchen. In dieser Arbeit wird damit ein neuer Typ von luftgekoppelten Ultraschallwandlern vorgestellt und deren Einsetzbarkeit in typischen ZfP-Anwendungen nachgewiesen. Die benötigten neuen Verfahren reichen über die fluidische Ultraschallerzeugung hinaus und können auch in konventionellen Luftultraschall-Anwendungen eingesetzt werden. Die vorgestellten Ergebnisse zeigen nicht nur, dass ein Wandler auf Basis eines fluidischen Wandstrahlelements eine robuste alternative Ultraschallquelle für die zerstörungsfreie Prüfung - insbesondere im Bauwesen - sein kann, sondern eröffnen allgemein das Forschungsfeld der aeroakustischen Wandler als Alternative zu konventionellen Geräten für die Erzeugung von luftgekoppeltem Ultraschall."]},{"key":"dc:title","label":"Title","values":["Fluidic ultrasound generation for nondestructive testing"]}]}],"canonical_facts":{"dc:contributor.advisor":["Sarradj, Ennes","Strangfeld, Christoph","Maack, Stefan"],"dc:creator":["Bühling, Benjamin"],"dc:date.accessioned":["2024-04-03T12:34:27Z"],"dc:date.available":["2024-04-03T12:34:27Z"],"dc:date.issued":["2024"],"dc:description.abstract":["Ultrasonic testing has become an indispensable method for verifying integrity, dimensional accuracy and material properties in numerous technical domains. Air-coupled ultrasound offers advantages in terms of measurement flexibility and reduced measurement time, but also presents challenges due to limitations in transmitted sound pressure amplitude and sensor positioning. Due to the high impedance mismatch at the interfaces between the transducer, air, and specimen, only a fraction of the generated sound pressure interacts with the specimen and is received by a sensor. To reduce these losses, a novel fluidic ultrasonic transducer is presented. This device produces a transient triggered ultrasound pulse based on aeroacoustic sound generation mechanisms in a bistable fluidic amplifier. Little is known about its performance characteristics and suitability for nondestructive testing (NDT). The publications included in this thesis are the first to present a transient aeroacoustic ultrasonic generator using a bistable fluidic amplifier. This dissertation demonstrates that such a fluidic ultrasonic transducer is applicable for common measurement tasks in NDT. By disseminating the acoustic and flow characteristics of the device, the resulting challenges and opportunities concerning its applicability to NDT tasks are identified and addressed. It is found that the generated pulse contains frequency components below 60 kHz, fluctuating in amplitude and phase delay, and is accompanied by a high velocity free jet that partially interacts with the sound pulses. In order to prevent interaction between the jet and the specimen surface and to increase transducer directivity, the attachment of sonic crystals and an exponential horn were successfully tested. The distinct spectral characteristics of each ultrasonic pulse were exploited to develop a signal processing approach that allows better differentiation between two pulses received in quick succession. This improved the usability of the fluidic transducer in multiple-input multiple-output (MIMO) setups. To address the stochastic ultrasound generation behavior, a novel, fully non-contact through-transmission measurement setup is presented that allows time-of-flight measurements without prior knowledge of trigger time, pulse shape, or distance between the transducer and the specimen. Successful measurement of longitudinal propagation velocity in various materials demonstrates that the fluidic transducer is capable of nondestructively measuring a variety of geometric and material properties. Thus, a new type of ultrasonic transducer has been established and its applicability to common NDT tasks has been demonstrated. The usability of these novel procedures extends beyond fluidic ultrasonic testing and can also be employed to improve conventional air-coupled ultrasonic measurements. The results presented not only offer the amplifier-based fluidic transducer as a robust alternative ultrasound source for NDT, especially in civil engineering, but also raise a number of research questions related to the use of aeroacoustic transducers as an alternative to conventional air-coupled ultrasonic devices.","Die Ultraschallprüfung hat sich in vielen technischen Bereichen zu einer unverzichtbaren Methode zur Überprüfung von Bauteilintegrität, Maßhaltigkeit und Materialeigenschaften entwickelt. Luftgekoppelter Ultraschall bietet Vorteile im Hinblick auf Flexibilität in der Durchführung der Messung und in der Verringerung der Messdauer. Herausforderungen bestehen hingegen sowohl aufgrund der geringeren eingebrachten Schalldruckamplituden als auch der erforderlichen Positionierungsgenauigkeit der Sensorik. Auf Grund des großen Unterschieds der spezifischen Schallimpedanzen an den Übergängen zwischen Schallwandler, Luft und Prüfkörper interagiert nur Bruchteil des erzeugten Schalldrucks mit dem Prüfkörper und wird im Anschluss vom Schallsensor empfangen. Um diese Verluste zu reduzieren, wird ein neuartiger fluidischer Ultraschallwandler vorgestellt. Basierend auf der aeroakustischen Schallerzeugung in einem fluidischen bistabilen Haftstrahlelement erzeugt dieses Gerät einen gesteuerten transienten Ultraschallpuls. Weder dessen Schallcharakteristik noch die Eignung zur zerstörungsfreien Prüfung (ZfP) wurden bisher erforscht. Die Publikationen dieser Dissertation sind die ersten, die Luftschallerzeugung durch fluidische Wandstrahlelemente untersuchen und die transiente Signalerzeugung mit Hilfe aeroakustischer Ultraschallwandler zeigen. In dieser Dissertation wird gezeigt, dass der fluidische Ultraschallwandler für übliche ZfP-Messverfahren geeignet ist. Mit der Untersuchung der Schall- und Strömungseigenschaften des Wandlers werden die Möglichkeiten und Herausforderungen für ZfP-Anwendungen herausgearbeitet. Es wird gezeigt, dass der durch den fluidischen Wandler erzeugte Puls dominante Frequenzen unter 60 kHz erzeugt, die stochastisch in Amplitude und Phase variieren, und mit einem Freistrahl nahe der Schallgeschwindigkeit einhergeht, der mit nachfolgenden Schallpulsen interagiert. Um die Interaktion dieses Freistrahls mit der Oberfläche eines Probekörpers zu verhindern und um die Richtcharakteristik des Wandlers zu verbessern, wurden das Anbringen eines Exponentialtrichters und der Einsatz sonischer Kristalle erfolgreich untersucht. Die spezifischen spektralen Eigenschaften der einzelnen Ultraschallpulse werden genutzt, um eine Signalverarbeitungsmethode zu entwickeln, durch die mehrere kurz aufeinanderfolgende Pulse besser unterschieden werden können und so Multiple-input Multiple-output (MIMO) Anwendungen mit Hilfe des fluidischen Wandlers möglich werden. Um dem stochastischen Verhalten des Schallerzeugungsmechanismus zu begegnen, wird ein neuartiger komplett berührungsloser Durchschallungsprüfstand vorgestellt, der erlaubt, die Laufzeit eines Ultraschallsignals zu messen, ohne dass der Trigger-Zeitpunkt, die Pulsform oder der Abstand zwischen Wandler und Probekörper bekannt sein müssen. Durch die erfolgreiche Messung der Longitudinalwellengeschwindigkeit in verschiedenen Materialien wird gezeigt, dass der fluidische Wandler geeignet ist, eine Reihe von Geometrie- und Materialeigenschaften zerstörungsfrei zu untersuchen. In dieser Arbeit wird damit ein neuer Typ von luftgekoppelten Ultraschallwandlern vorgestellt und deren Einsetzbarkeit in typischen ZfP-Anwendungen nachgewiesen. Die benötigten neuen Verfahren reichen über die fluidische Ultraschallerzeugung hinaus und können auch in konventionellen Luftultraschall-Anwendungen eingesetzt werden. Die vorgestellten Ergebnisse zeigen nicht nur, dass ein Wandler auf Basis eines fluidischen Wandstrahlelements eine robuste alternative Ultraschallquelle für die zerstörungsfreie Prüfung - insbesondere im Bauwesen - sein kann, sondern eröffnen allgemein das Forschungsfeld der aeroakustischen Wandler als Alternative zu konventionellen Geräten für die Erzeugung von luftgekoppeltem Ultraschall."],"dc:identifier.uri":["https://depositonce.tu-berlin.de/handle/11303/21206","https://doi.org/10.14279/depositonce-20006"],"dc:language.iso":["en"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:title":["Fluidic ultrasound generation for nondestructive testing"],"dc:type":["Doctoral Thesis"]},"updated_at":"2026-07-27T21:28:26Z"}