Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-42030 Beitrag zu einem Tagungsband Beckmann, Jörg; Spranger, Holger THz-TDS-SAFT for the detection of inherent discontinuities in dielectric materials Today X-ray tomography and Ultrasound Synthetic Aperture Focusing Techniques are representative examples for defect imaging in the field of nondestructive testing. THz time domain spectroscopy (TDS) operates with short electromagnetic pulses. The sensitivity of the pulses to optical material property changes makes THz-TDS attractive for the detection of flaws in dielectric materials. Unfortunately, the X-ray computed tomography (CT) model holds only for THz-TDS reconstruction if minor refraction index differences between the inhomogeneities and the surrounding material matrix exist. A Time Domain SAFT algorithm has been developed to overcome the restrictions. THz time domain measurement on representative sample sets with inherent artefacts were performed to use them for the Image reconstructions. The results will be presented and compared with optical surface images of the used test objects to evaluate the SAFT algorithm in relation to the econstruction quality. Danvers, USA IEEE IEEE 2017 IRMMW- THz-Program 978-1-5090-6048-1 42nd International Conference on Infrared, Millimeter and Terahertz Waves Cancun, Mexico 27.08.2017 01.09.2017 TD.19-1 TD.19-2 10.1109/IRMMW-THz.2017.8067159 2017-09-21 OPUS4-47220 Beitrag zu einem Tagungsband Beckmann, Jörg; Spranger, Holger; Ewert, Uwe THz Applications for Non-Destructive Testing Up to now THz-TDS-systems aren't considered to be nondestructive testing facilities for large scale industrial applications, despite it was proven that they provide a comprehensive set of quality parameters. A practical approach to bring THz-TDS in addition to already existing testing systems into the industrial mainstream is systematic development of future test procedures and test facilities for dielectrics. For this purpose polyeth-ylene test specimen with introduced artefacts were designed, to evaluate the detection sensitivity of Time of Flight measurements based on dielectrics. SAFT reconstructed tomograms are presented which visualize the sizes and location of artificially introduced flaws. USA IEEE Conference Publication IEEE 2018 2017 Far East NDT New Technology & Application Forum (FENDT) 12 2017 Far East NDT New Technology & Application Forum (FENDT) XI'an, China 22.06.2017 24.06. 2017 272 276 10.1109/FENDT.2017.8584511 2019-01-28 OPUS4-37246 Vortrag Spranger, Holger THz-TOF saft & ola for the detection of inherent discontinuities in dielectric materials T-rays are electromagnetic waves with frequencies between 0.3 and 10 THz. The ability to penetrate dielectric materials makes them attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available which operates with THz-pulses. In THz-TDS the travelling time (ToF) and shape of the pulse changes if it interacts with the basic material and its discontinuities. Several reconstruction techniques have been already demonstrated in the context of THz-ToF. Nevertheless, tomographic reconstruction procedures, developed for x-ray computed tomography (CT) ap-plications, have been preferably applied. As a result, reliable tomograms could be presented in case of existing minor refraction property differences between the defect and its surrounding material. Nevertheless geometric artefacts could be observed. The strong restriction of the CT application for the inspection of dielectric plastics that engaged us to develop a recon-struction technique that takes refraction into account. A time domain SAFT based algorithm will be presented, which is able to visualize discontinuities properly in dimension and location, if the base materials shape and its refractive index are considered. The algorithm became more challenging in case of multilayer composites. For that reason an Optical Layer algorithm was developed. Measurements on representative samples with a variety of artificially produced small and large size defects will be shown. The calculated tomograms will be demonstrated to discuss and evaluate the benefits and limits of the two different reconstruction approaches. 2016 QNDE 2016 Atlanta, G.A, USA 17.07.2016 22.07.2016 2016-09-01 OPUS4-36221 Posterpräsentation Spranger, Holger THz-ToF techniques for the detection of inherent discontinuities in dielectric materials based on SAFT The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. Changes of travelling time (ToF) and pulse shape due to the interactions of THz pulses with the dielectric material and its inherent discontinuities can be observed. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. 2016 7th International Workshop on Terahertz Technology and Applications Kaiserslautern, Germany 15.03.2016 2016-05-25 OPUS4-36223 Posterpräsentation Spranger, Holger THz-ToFD Tomography with Synthetic-Aperture-Aperture Terahertz-radiation (T-ray) are electromagnetic waves within a frequency range between 0,3 to 6 THz. T-rays are nonionising! They penetrate plastic, paper, ceramic and fabric. It is promising to use T-Rays for CT-applications to reveal uncertainties in dielectric materials. 2013 8. THz-PhD-meeting Marburg, Germany 06.08.2013 2016-05-26 OPUS4-36591 Vortrag Spranger, Holger THz-ToF techniques for the detection of inherent discontinuities in dielectric materials based on a SAFT - and an Optical Layer reconstruction algorithm Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent disconti-nuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. Otherwise, planar discontinuities like cracks in plastics or delaminated lay-ers in composites can be abstracted as layers located at any angle in relation to the outer sample surface direction. A tomogram from the scanned sample can then be reconstructed in case the interactions of electromagnetic pulses with the existing in-herent interfaces are detectable and a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielec-tric properties. A short description of both the SAFT - and Optical Layer algorithm for the recon-struction of the inherent structure is initially given. Measurements on representative samples with a variety of artificially produced small and large scale. Reconstructed tomograms are presented to discuss and evaluate the benefits and limits of the two different reconstruction approaches. 2016 19th World Conference on Non-Destructive Testing 2016 Munich, Germany 13.06.2016 2016-06-22 OPUS4-39689 Vortrag Spranger, Holger THZ-SAFT Rekonstruktion von HDPE-Bauteilen Obwohl THz-TDS-Systeme vielfältige Qualitätsparameter von Dielektrika ermitteln können, ist deren industrielle Nutzung im Bereich der zerstörungsfreien Bauteilprüfung noch nicht anerkannter Stand der Technik. Ein pragmatischer Weg, TDS-Systeme neben traditionellen Prüfverfahren zu etablieren, sind systematische Untersuchungen an Modellbauteilen, mit dem Ziel einer Methodenentwicklung zur zuverlässigen berührungslosen Prüfung von Dielektrika. Anhand von THz-TDS-Messungen an Polyethylen-Testkörpern mit künstlich eingebauten Fehlstellen werden anfänglich die Möglichkeiten der Laufzeitmessung zur Ermittlung von Tiefenlagen von Ungänzen in Testkörpern präsentiert. Im weitern Teil wird gezeigt, wie durch eine veränderte Versuchsdurchführung und Verwendung eines modifizierten SAFT-Rekonstruktions-Algorithmus Tomogramme berechnet werden können, in denen die künstlich eingebrachten Fehlstellen hinsichtlich ihrer Größe und Lage geometrisch richtig dargestellt werden. 2017 3. Fachseminar Mikrowellen- und Terahertz-Prüftechnik in der Praxis Würzburg, Germany 05.04.2017 2017-04-07 OPUS4-39393 Beitrag zu einem Tagungsband Spranger, Holger; Beckmann, Jörg THz - ToF optical layer analysis (OLA) to determine optical properties of dielectric materials Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. The knowledge of the base materials shape and optical properties is essential for a proper reconstruction result. To obtain these properties a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric characteristics. The Optical Layer Analysis (OLA) is able to fulfill these requirements. A short description why the optical properties are crucial for meaningful SAFT reconstruction results will be given first. Afterwards the OLA will be derived and applied on representative samples to discuss and evaluate ist benefits and limits. AIP Publishing American Institute of Physics 2017 AIP Conference Proceedings 1806 978-0-7354-1474-7 QNDE 2016 Atlanta, GA, USA 17.07.2016 22.07.2016 1 UNSP 120002, 1 7 10.1063/1.4974707 2017-03-16 OPUS4-39688 Beitrag zu einem Tagungsband Spranger, Holger; Beckmann, Jörg THz-SAFT Rekonstruktion von HDPE-Bauteilen Obwohl THz-TDS-Systeme vielfältige Qualitätsparameter von Dielektrika ermitteln können, ist deren industrielle Nutzung im Bereich der zerstörungsfreien Bauteilprüfung noch nicht anerkannter Stand der Technik. Ein pragmatischer Weg, TDS-Systeme neben traditionellen Prüfverfahren zu etablieren, sind systematische Untersuchungen an Modellbauteilen, mit dem Ziel einer Methodenentwicklung zur zuverlässigen berührungslosen Prüfung von Dielektrika. Anhand von THz-TDS-Messungen an Polyethylen-Testkörpern mit künstlich eingebauten Fehlstellen werden anfänglich die Möglichkeiten der Laufzeitmessung zur Ermittlung von Tiefenlagen von Ungänzen in Testkörpern präsentiert. Im weitern Teil wird gezeigt, wie durch eine veränderte Versuchsdurchführung und Verwendung eines modifizierten SAFT-Rekonstruktions-Algorithmus Tomogramme berechnet werden können, in denen die künstlich eingebrachten Fehlstellen hinsichtlich ihrer Größe und Lage geometrisch richtig dargestellt werden. Berlin Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) 2017 DGZfP-Berichtsband 161 978-3-940283-84-9 3. Fachseminar des FA MTHz Mikrowellen- und Terahertz-Prüftechnik in der Praxis Würzburg, Germany 05.04.2017 1 9 urn:nbn:de:kobv:b43-396883 http://creativecommons.org/licenses/by-nd/3.0/de/ 2017-04-07 OPUS4-36586 Beitrag zu einem Tagungsband Spranger, Holger; Beckmann, Jörg; Boehm, Rainer THz-ToF techniques for the detection of inherent discontinuities in dielectric materials based on a SAFT - and an optical layer reconstruction algorithm Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. Otherwise, planar discontinuities like cracks in plastics or delaminated layers in composites can be abstracted as layers located at any angle in relation to the outer sample surface direction. A tomogram from the scanned sample can then be reconstructed in case the interactions of electromagnetic pulses with the existing inherent interfaces are detectable and a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric properties. A short description of both the SAFT - and Optical Layer algorithm for the reconstruction of the inherent structure is initially given. Measurements on representative samples with a variety of artificially produced small and large scale. Reconstructed tomograms are presented to discuss and evaluate the benefits and limits of the two different reconstruction approaches. 2016 DGZfP-Proceedings 158 978-3-940283-78-8 19th World Conference on Non-Destructive Testing 2016 Munich, Germany 13.06.2016 1 10 urn:nbn:de:kobv:b43-365866 http://creativecommons.org/licenses/by-nd/3.0/de/ 2016-06-21