TY - CONF A1 - Erthner, Thomas A1 - Bertus, Norbert A1 - Dohse, Elmar A1 - Neubauer, Andreas A1 - Pelkner, Matthias A1 - Kreutzbruck, Marc T1 - Miniaturisierte Mehrkanalelektronik für die magnetische Streuflussprüfung N2 - Hohe Empfindlichkeit und Ortsauflösung sowie eine kurze Prüfzeit sind Anforderungen an ein leistungsfähiges Prüfsystem basierend auf magnetischen ZfP-Verfahren für die Oberflächenprüfung. Dieses soll das sichere Auffinden feinster Risse mit Tiefen von weniger als 50 Mikrometern gewährleisten. Um eine gute Ortsauflösung zu gewährleisten, müssen in der Regel der Defektgröße angepasste Sensoren zum Einsatz kommen. Speziell im Fall von Risslängen kleiner als ein Millimeter sollten die Sonden für die Streuflussprüfung ebenfalls Wirkbreiten kleiner als ein Millimeter aufweisen. Durch die daraus folgenden geringen Spurbreiten ergeben sich allerdings lange Prüfzeiten. Der begrenzten Prüfzeit und präzisionsbedingten mechanischen Grenzen in der Verfahr- Geschwindigkeit einer Sonde kann mit einem Multikanalansatz begegnet werden. Eine hohe Anzahl an Kanälen wiederum führt zu einem Platzproblem in der Prüfsonde, schließlich erfordert die Verstärkung schwacher Signale im eine Reihe von aktiven Bauelementen. Der Schlüssel zur Auflösung dieses Konflikts ist der Einsatz moderner Schaltkreise wie Multiplexer und FPGA. In diesem Beitrag stellen wir am Beispiel eines 48 kanaligen Testaufbaus für die GMR-basierte Streuflussprüfung ein flexibles miniaturisiertes Elektronikkonzept vor. Dabei gehen wir auf die einzelnen Komponenten zur Ansteuerung der Sensoren und zur Signalkonditionierung ein. Wir berichten vom Design, Aufbau und der Charakterisierung des Multikanalmoduls und seiner Erprobung im realen Prüfeinsatz. T2 - DACH-Jahrestagung 2012 CY - Graz, Austria DA - 2012-09-17 KW - GMR KW - Streufluss PY - 2012 UR - http://jt2012.dgzfp.de/Portals/jt2012/BB/p29.pdf SN - 978-3-940283-44-3 IS - DGZfP-BB 136 SP - Poster 29, 1 EP - 7 AN - OPUS4-32698 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kreutzbruck, Marc T1 - Flying Laser Spot Thermography for the Fast Detection of Surface Breaking Cracks T2 - 18th WCNDT 2012 (World Conference on Nondestructive Testing) CY - Durban, South Africa DA - 2012-04-16 PY - 2012 AN - OPUS4-26719 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kreutzbruck, Marc T1 - Progress in Acoustical Defect Sizing NDT Methods for the Inspection of Power-Plant Components T2 - 18th WCNDT 2012 (World Conference on Nondestructive Testing) CY - Durban, South Africa DA - 2012-04-16 PY - 2012 AN - OPUS4-26720 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kreutzbruck, Marc T1 - Adapted GMR Sensor Arrays used in Magnetic Flux Leakage Inspection T2 - 18th WCNDT 2012 (World Conference on Nondestructive Testing) CY - Durban, South Africa DA - 2012-04-16 PY - 2012 AN - OPUS4-26722 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Richter, Regina A1 - Maierhofer, Christiane A1 - Kreutzbruck, Marc ED - Cardone, G. T1 - Numerical method of active thermography for the reconstruction of back wall geometry T2 - QIRT 11 - 11th International conference on Quantitative InfraRed Thermography CY - Prague, Czech Repubilc DA - 11.06.2012 KW - Rekonstruktion KW - Inverse Probleme KW - Defekte PY - 2012 SP - 1 EP - 9 AN - OPUS4-26446 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kreutzbruck, Marc T1 - A Resonance-Free Nanofilm Airborne Ultrasound Emitter N2 - In recent years the demand for airborne ultrasound techniques for non-destructive materials testing has increased remarkably. The applications for non-contact airborne ultrasound techniques are very broad and range from detection of flaws in composite laminates, solar cells and printed circuit boards to the applications in medicine and food industry. Conventional piezoelectric ultrasound transducers are mostly narrowbanded, show large resonance oscillations after a short excitation and therefore are generally not suitable for pulse-echo applications. In this contribution we present a novel thermoacoustic approach for the generation of broad band airborne ultrasound and investigate the applicability of resonance-free thermoacoustic emitters for very short high pressure airborne ultrasound pulses. We report on measurements of thermoacoustic emitters consisting of metal film below 50 nm thickness, generating sound pressure values of more than 140 dB in 60 mm distance and compare the results with piezoelectric airborne ultrasound transducers. Our experimental investigations show that such thermoacoustic devices can be used as a broad band emitters using pulse excitation. T2 - QNDE Conference 2012 CY - Denver, CO, USA DA - 2012-07-15 PY - 2012 AN - OPUS4-26756 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kreutzbruck, Marc T1 - Ultrasound and Thermographic Imaging for Weld Inspection T2 - NDE of Welds Short Course CY - Denver, CO, USA DA - 2012-07-14 PY - 2012 AN - OPUS4-26757 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Daschewski, Maxim A1 - Harrer, Andrea A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - 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 - JOUR A1 - Döring, Joachim A1 - Bovtun, V. A1 - Gaal, Mate A1 - Bartusch, Jürgen A1 - Erhard, Anton A1 - Kreutzbruck, Marc A1 - Yakymenko, Y. T1 - Piezoelectric and electrostrictive effects in ferroelectret ultrasonic transducers N2 - Electromechanical response of polypropylene ferroelectret transducers under application of high-voltage pulses was measured by laser Doppler vibrometry and compared with results of ultrasonic through-air transmission between two ferroelectret transducers. The electromechanical response was completely explained by piezoelectric and electrostrictive effects. The electrostrictive effect dominates at high voltages and provides significant enlargement of the transducer constant, up to factor of 2.5. The induced strain of 1.7% was achieved at – 2000 V. The nonlinear ultrasonic transmission was shown to be well described by the piezoelectric and electrostrictive response of transmitter, except in the range of high negative exciting voltages where some limitation of the transmitted signal was observed. This limitation seems not to be a fundamental one and does not abolish the advantages of high-voltage excitation of polypropylene ferroelectret transducers. KW - Electromechanical effects KW - Ferroelectric devices KW - Piezoelectric transducers KW - Piezoelectricity KW - Ultrasonic transducers KW - Ultrasonic transmission KW - Cellular polypropylene KW - Ferroelectret KW - Electrostriction PY - 2012 DO - https://doi.org/10.1063/1.4759052 SN - 0021-8979 SN - 1089-7550 VL - 112 IS - 8 SP - 084505-1 - 084505-6 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-26806 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 - JOUR A1 - Maierhofer, Christiane A1 - Röllig, Mathias A1 - Steinfurth, Henrik A1 - Ziegler, Mathias A1 - Kreutzbruck, Marc A1 - Scheuerlein, C. A1 - Heck, S. T1 - Non-destructive testing of Cu solder connections using active thermography N2 - Impulse and lock-in thermography have been applied to detect delaminations of prototype solder joints, similar to those to be produced between Cu shunts and Cu busbar stabilisers at the Large Hadron Collider (LHC) at CERN. Two infrared cameras with different detector materials and with different spectral ranges and two excitation techniques have been tested and compared for their ability to detect delaminations behind 2 and 3 mm thick Cu shunts. We have analyzed the signal to noise ratio (SNR) for each detected defect and are able to detect defects down to a nominal edge length of 4 mm behind 2 mm thick Cu shunts by using fast impulse thermography and a camera with a microbolometer array. For the 3 mm thick Cu shunt, on the other hand, the nominal 4 mm defect is only visible in the lock-in thermography phase images and the highest SNR has been achieved with a cooled InSb-based camera. In addition, numerical simulations show the influence of the minimum detectable defect size on the shunt thickness and that the developed on-site testing technique is sufficient to find all defects that are detectable theoretically. KW - Active thermography KW - Solder joint KW - Copper KW - FFT KW - Signal-to-noise-ratio PY - 2012 DO - https://doi.org/10.1016/j.ndteint.2012.07.010 SN - 0963-8695 VL - 52 SP - 103 EP - 111 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-27575 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schlichting, Joachim A1 - Maierhofer, Christiane A1 - Kreutzbruck, Marc T1 - Crack sizing by laser excited thermography N2 - Active thermography is a nowadays widely used NDT method making use of thermal material properties for defect detection. Basically, the sample is heated and the resulting surface temperature is recorded by an IR camera. For laser thermography a laser is used to heat the sample locally. The resulting spherical heat flow allows the detection of voids in arbitrary orientation. In this work, a method is presented which is suitable for the quantitative characterization of depth and angle of surface cracks. The main idea is to evaluate the crack-caused asymmetries of the laser's thermal footprint. The heat is introduced at fixed reference positions relative to the crack. In this paper a data analysis procedure is presented which allows the crack depth and angle to be described by only two characteristic scalar parameters. By investigating artificial test specimens with spark eroded notches, the feasibility of this method is validated. Furthermore, the behavior of the characteristic parameters with variations of crack angle, depth and experimental conditions is studied systematically by FEM simulations, showing that these parameters are well behaved. KW - Thermography KW - Laser excitation KW - FEM modeling KW - Crack sizing PY - 2012 DO - https://doi.org/10.1016/j.ndteint.2011.09.014 SN - 0963-8695 VL - 45 IS - 1 SP - 133 EP - 140 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-24873 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schlichting, Joachim A1 - Brauser, Stephan A1 - Pepke, Lutz-Alexander A1 - Maierhofer, Christiane A1 - Rethmeier, Michael A1 - Kreutzbruck, Marc T1 - Thermographic testing of spot welds N2 - Spot welding is one of the most important technologies for joining sheet metal. While there are lot of approaches to non-destructive testing, quality assurance still mainly relies on welding parameter monitoring and destructive testing, leading to significant failure rates. In this paper an approach to spot weld testing using flash thermography is presented. The main focus of attention is on the identification of two typical error classes: stick welds and welds at the splash limit. Besides investigating the principal feasibility of thermography for zinc plated samples the results of a series test of spot welds joining 1 mm thick TRIP steel are shown. Based upon these results a statistical criterion is developed which allows a reliable classification of the named error classes. KW - Thermography KW - Spot welding KW - Automotive industry PY - 2012 DO - https://doi.org/10.1016/j.ndteint.2012.02.003 SN - 0963-8695 VL - 48 SP - 23 EP - 29 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-26276 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Richter, Regina A1 - Kreutzbruck, Marc A1 - Maierhofer, Christiane T1 - Untersuchungen zur 2D- und 3D-Rekonstruktion von Rückwandgeometrien in der Impuls-Thermografie N2 - Die aktive Thermografie kommt zunehmend in der zerstörungsfreien Prüfung zum Einsatz. Hierin steckt allerdings der Bereich der Defektklassifizierung und die quantitative Defektcharakterisierung noch in den Kinderschuhen. In diesem Beitrag werden die Möglichkeiten untersucht anhand einer inversen Rekonstruktion von thermografischen Daten die Rückwandgeometrien in 2D und 3D zu ermitteln. Die Datensätze wurden bei der Prüfung von 2 cm dicken PVC-Platten mit rückseitiger Nutfräsung und mit Flachbodenbohrungen von unterschiedlichen Restwandstärken und Durchmessern gewonnen. Die thermische Anregung erfolgt mit Blitzlampen, die zeit- und ortsaufgelöste Erfassung der Oberflächentemperatur mit einer Infrarotkamera. Sowohl die thermische Anregung als auch die Temperaturmessung werden von der defektfreien Vorderseite aus durchgeführt. Die Unregelmäßigkeiten in der Abkühlung weisen auf unterschiedliche Materialdicken hin, die unter Verwendung eines iterativen Vergleiches mit simulierten Daten an die realen Wandstärken angenähert werden. Mittels simulierter Daten, die in 2D bzw. 3D durch eine Finite-Elemente-Methode berechnet werden, rekonstruieren wir die Geometrie des Probekörpers in 2D bzw. 3D mit einer optimierten und zuverlässigeren Version der iterativen Echo-Defect-Shape-Methode. Diese zeiteffiziente Methode berechnet den Startwert und seine iterative Verbesserung anhand des relativen Kontrastes. Wanddicken können innerhalb der Iteration zu- und abnehmen, bei der optimierten Version aber nicht kleiner als der Startwert werden. Dies bietet eine größere Zuverlässigkeit, da die Wanddicke vor der Iteration, d.h. der Startwert, grundsätzlich unterschätzt wird. Unter der Voraussetzung geeigneter Startwerte und Abbruchkriterien kann die Restwand an minimalen Wanddicken im Mittel auf ca. 1 mm genau bestimmt werden (z. B. bei 3D Rekonstruktion der Flachbodenbohrungen). Speziell an scharfen Defektkanten verliert das Verfahren durch laterale Wärmeflüsse an Genauigkeit. T2 - DACH-Jahrestagung 2012 CY - Graz, Austria DA - 17.09.2012 KW - Rekonstruktion KW - Inverse Probleme KW - Defekte PY - 2012 SN - 978-3-940283-44-3 IS - DGZfP-BB 136 SP - Poster 33, 1 EP - 8 AN - OPUS4-27694 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Neubauer, Andreas A1 - Reimund, Verena A1 - Erthner, Thomas A1 - Panke, Nicolai A1 - Kreutzbruck, Marc T1 - Automatisierte Streuflussprüfung und Bewertung von Zylilnderlagerringen unter Anwendung von GMR-Sensorarrays N2 - Dieser Beitrag behandelt die automatisierte Streuflussprüfung an Zylinderlagerschalen. Die Anforderung an das im Verbundprojekt mit Industriepartnern aufgebaute System waren neben einer schnellen Detektion von Mikrorissen die Bewertung und grafische Darstellung der ermittelten Risssignale. Mithilfe neu angepasster GMR-Sensorarrays war es möglich, die Prüfung der Außen-, Innen- und Stirnflächen in kürzester Zeit (< 2 min) durchzuführen und Risse mit einer Tiefe unterhalb der geforderten 50 µm zu detektieren (Risse mit Tiefen von 30 µm konnten noch mit einem guten Signal-Rausch-Abstand besser 6 dB detektiert werden). Eine selbst entwickelte Messsoftware bereitet die Daten auf und stellt sie grafisch dar. Zusätzlich werden die Mikrorisse bewertet. T2 - DACH-Jahrestagung 2012 CY - Graz, Austria DA - 17.09.2012 KW - Streufluss KW - GMR KW - Sensorarrays PY - 2012 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-279490 SN - 978-3-940283-44-3 IS - DGZfP-BB 136 SP - Mo.2.A.2, 1 EP - 8 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung e.V. (DGZfP) AN - OPUS4-27949 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Neubauer, Andreas A1 - Reimund, Verena A1 - Kreutzbruck, Marc ED - Thompson, D. O. ED - Chimenti, D. E. T1 - Local magnetization unit for GMR array based magnetic flux leakage inspection N2 - GMR sensors are increasingly used for magnetic surface inspection due to their high sensitivity and high spatial resolution. In case of simple planar or cylindrical shaped components, the GMR-based inspection procedure can be automated easily. We present GMR measurements of real fatigue cracks. In addition, we present a probe design using a local magnetization unit and commercially available GMR sensors. The design was carried out by means of finite-element method (FEM) simulations. Using the local probe we measured bearings containing artificial reference cracks of different depths and orientations. Cracks with a depth of 40 µm could be resolved with a signal-to-noise ratio better than 6. A further reduction of the measuring time can be obtained using a sensor array. For this purpose we present a study of the optimized size of the sensing GMR-layers for a NDE-adapted sensor array. The geometric sensor parameters were investigated through simulations of the magnetic flux leakage of surface cracks using an analytic model. T2 - 38th Annual Review of Progress in Quantitative Nondestructive Evaluation CY - Burlington, VT, USA DA - 17.07.2011 KW - GMR KW - Magnetic flux leakage KW - NDE KW - Sensor array PY - 2012 SN - 978-0-7354-1013-8 DO - https://doi.org/10.1063/1.4716332 SN - 0743-0760 SN - 0094-243X N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings IS - 1430 SP - 1005 EP - 1012 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-26107 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pelkner, Matthias A1 - Neubauer, Andreas A1 - Reimund, Verena A1 - Kreutzbruck, Marc T1 - Routes for GMR-sensor design in non-destructive testing N2 - GMR sensors are widely used in many industrial segments such as information technology, automotive, automation and production, and safety applications. Each area requires an adaption of the sensor arrangement in terms of size adaption and alignment with respect to the field source involved. This paper deals with an analysis of geometric sensor parameters and the arrangement of GMR sensors providing a design roadmap for non-destructive testing (NDT) applications. For this purpose we use an analytical model simulating the magnetic flux leakage (MFL) distribution of surface breaking defects and investigate the flux leakage signal as a function of various sensor parameters. Our calculations show both the influence of sensor length and height and that when detecting the magnetic flux leakage of µm sized defects a gradiometer base line of 250 µm leads to a signal strength loss of less than 10% in comparison with a magnetometer response. To validate the simulation results we finally performed measurements with a GMR magnetometer sensor on a test plate with artificial µm-range cracks. The differences between simulation and measurement are below 6%. We report on the routes for a GMR gradiometer design as a basis for the fabrication of NDT-adapted sensor arrays. The results are also helpful for the use of GMR in other application when it comes to measure positions, lengths, angles or electrical currents. KW - Giant magneto resistance KW - Non-destructive testing KW - Magnetic flux leakage KW - Sensor array PY - 2012 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-271325 DO - https://doi.org/10.3390/s120912169 SN - 1424-8220 VL - 12 IS - 9 SP - 12169 EP - 12183 PB - MDPI CY - Basel AN - OPUS4-27132 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schlichting, Joachim A1 - Ziegler, Mathias A1 - Maierhofer, Christiane A1 - Kreutzbruck, Marc T1 - Flying laser spot thermography for the fast detection of surface breaking cracks N2 - We report on recent developments in the detection of surface breaking cracks using flying laser spot thermography. Application of an infrared camera for mapping the thermal radiation after excitation with a diode laser equipped with an optical scanner allows us to examine a surface containing cracks in an entirely non-destructive, contactless and fast way, without even moving the camera. We developed an efficient and robust algorithm that can be applied directly to the recorded thermal sequences, and that derives a single image containing all crack signatures. For this crack detection technique, no specific synchronisation between laser and camera is required. Hence, our approach is suitable for an upgrade of existing thermographic systems. The feasibility of the proposed procedure is proven by testing an artificial test sample and a piece of rail that comprises roll contact fatigue cracks and by comparing the results with magnetic particle testing. T2 - 18th WCNDT - World conference on nondestructive testing CY - Durban, South Africa DA - 16.04.2012 KW - Thermography KW - Cracks KW - Laser KW - Flying spot PY - 2012 SN - 978-0-620-52872-6 IS - (Paper 499) SP - 1 EP - 7 AN - OPUS4-26352 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 - Neubauer, Andreas A1 - Pelkner, Matthias A1 - Reimund, Verena T1 - Adapted GMR array used in magnetic flux leakage inspection N2 - GMR sensors are increasingly used for magnetic surface inspection due to their high sensitivity and high spatial resolution. In case of simple planar or cylindrical shaped components, the GMR-based inspection procedure can be automated easily. In order to reduce the inspection time we present a GMR-based NDT-system consisting of a yoke and a coil as a local magnetization unit. This way the global magnetization step and, if necessary, the corresponding demagnetization cycle can be avoided reducing the number of working steps. Using a local probe we measured plates, bearings, and rails, each of which containing real fatigue cracks and reference artificial cracks of different depths and orientations. Cracks with a depth of 40 ìm could be resolved with a signalto-noise ratio of about 20. A reduction of the measuring time can be obtained using a sensor array. We present an optimized sensor array for nondestructive testing application, where gradiometric arranged GMR layers were fabricated on a board with up to 48 GMR sensors. Each sensor detects the vertical field gradient. In our example the baseline was chosen to be 250 ìm which efficiently suppress external Background fields without losing sensitivity for the detection of surface breaking defects. T2 - 18th WCNDT - World conference on nondestructive testing CY - Durban, South Africa DA - 16.04.2012 KW - Flux leakage testing KW - GMR-Sensors KW - Sensor arrays PY - 2012 SN - 978-0-620-52872-6 SP - 1 EP - 8 (Paper 498) AN - OPUS4-26351 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 -