TY - THES A1 - Pelkner, Matthias T1 - Entwicklung, Untersuchung und Anwendung von GMR-Sensorarrays für die Zerstörungsfreie Prüfung von ferromagnetischen Bauteilen N2 - Die Zerstörungsfreie Prüfung (ZfP) ist ein wichtiges Werkzeug zur Qualitätssicherung sowie zur Überwachung sicherheitsrelevanter Bauteile. In der industriellen ZfP ist das Interesse an innovativen, kostengünstigen und sicherheitssteigernden ZfP-Methoden sehr groß. Die klassische Streuflussmethode ist die Magnetpulverprüfung, die sehr sensitiv auf Mikrorisse ist. Eine zuverlässige, automatische Prüfung ist hier aber nur bedingt und mit großem Aufwand zu erreichen. Die Lösung liegt im Einsatz von Magnetfeldsensoren, die zudem eine Bewertung der Defektgeometrie aufgrund der gemessenen Rissstreufelder ermöglicht. Insbesondere GMR-Sensoren (giant magneto resistance) eignen sich hierfür aufgrund ihrer kleinen Sensorelemente, welche eine hohe Ortsauflösung ermöglichen, und der sehr guten Feldempfindlichkeit. Jedoch sind kommerzielle GMR-Sensoren nicht an die Bedürfnisse der ZfP angepasst. Daher wurden während dieser Arbeit GMR-Sensoren dahingehend optimiert, dass sie für eine automatisierte Prüfung infrage kommen. Neben dem Design und der Charakterisierung der angepassten Sensoren wurden Messungen zur Detektionswahrscheinlichkeit durchgeführt. Um die Praxistauglichkeit zu untermauern, erfolgte ein quantitativer Vergleich mit alternativen ZfP- Oberflächenmethoden, der Wirbelstrom-, Magnetpulver- und Thermografieprüfung. Zusätzlich konnte der erfolgreiche Einsatz der GMR-Streuflussprüfung in einer industriellen, automatisierten Prüfeinrichtung unter Beweis gestellt werden. N2 - Non-destructive testing is important for both Quality control and maintenance of safety-related components. Modern industry steadily undergoes competition and cost pressure. Therefore, new innovative testing methods are key to increase safety and cost effectiveness. The conventional magnetic flux leakage testing method (MFL) using magnetic particle inspection (MP) is a manual procedure which is very sensitive in terms of the detection of micrometer-scaled cracks. An automated reliable testing however calls for adapted magnetic field sensors. Additionally the quantification of stray fields allows an evaluation of defect geometry. GMR sensors (giant magneto resistance) are particularly well-suited for this purpose. Their low costs, excellent field sensitivity, and capacity to be miniaturized lead to high resolution test results. However, drawbacks exist for commercial GMR sensors which include nonadaption for NDT applications. To overcome this drawback one objective of this thesis was to optimize the geometry of the sensing elements for a GMR sensor array. After characterization, the new sensor arrays were used for validation and investigation of a probability of detection. In addition, by comparing GMR-MFL with other testing methods related to surface breaking defects (eddy current testing, MP, thermography), it was possible to classify in a first step GMR MFL testing in NDT. Finally, an automated GMR was tested successfully established for industrial purposes. T3 - BAM Dissertationsreihe - 122 KW - Zerstörungsfreie Prüfung KW - GMR KW - magnetischer Streufluss KW - Sensorarrays PY - 2014 SN - 978-3-9816668-0-9 SN - 1613-4249 VL - 122 SP - 1 EP - 232 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-36 LA - deu 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 - 2012-04-16 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 - Pelkner, Matthias A1 - Neubauer, Andreas A1 - Kreutzbruck, Marc T1 - Automatisierte Streuflussprüfung und Bewertung von Zylinderlagerringen unter Anwendung von GMR-Sensorarrays T2 - DACH-Tagung (DGZfP-Jahrestagung) CY - Graz, Austria DA - 2012-09-17 PY - 2012 AN - OPUS4-27943 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 T2 - DACH-Jahrestagung 2012 CY - Graz, Austria DA - 2012-09-17 KW - Streufluss KW - GMR KW - Sensorarrays PY - 2012 SN - 978-3-940283-44-3 IS - DGZfP-BB 136 SP - Mo.2.A.2, 1 EP - 8 AN - OPUS4-27949 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Reimund, Verena A1 - Neubauer, Andreas A1 - Kreutzbruck, Marc T1 - Lokal Magnetization Unit for GMR Array Based Magnetic Flux Leakage Inspection T2 - QNDE 2011 CY - Burlington, VT, USA DA - 2011-07-17 PY - 2011 AN - OPUS4-24573 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Reimund, Verena A1 - Blome, Mark A1 - Pelkner, Matthias A1 - Kreutzbruck, Marc T1 - Fast defect parameter estimation based on magnetic flux leakage measurements with GMR sensors N2 - We present a fast inverse scheme that is capable of simultaneously estimating the parameters depth, opening and length for rectangular 3D geometries of surface-breaking defects. The parameter estimation is realized by an iterative least-squares minimization using the trust-region reflective algorithm. A semi-analytic magnetic dipole model that allows the sensor characteristics to be incorporated is used for predicting the stray magnetic fields. Giant magneto-resistance (GMR) measurements were carried out on a test specimen that includes a series of artificial defects. For the estimation of the defect depths relative errors between 0.6% and 15.9% have been obtained. Due to its very low computational costs, the inverse scheme can suitably be employed in automated production environments. KW - Magnetic flux leakage KW - GMR sensor KW - Nonlinear least-squares optimization PY - 2011 U6 - https://doi.org/10.3233/JAE-2011-1391 SN - 1383-5416 SN - 0925-2096 VL - 37 IS - 2-3 SP - 199 EP - 205 PB - IOS Press CY - Amsterdam, The Netherlands AN - OPUS4-24637 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schlichting, Joachim A1 - Ziegler, Mathias A1 - Pelkner, Matthias A1 - Maierhofer, Christiane A1 - Kreutzbruck, Marc T1 - Kameragestütztes Flying-Spot-Verfahren zur Risserkennung N2 - In dieser Arbeit wird ein kameragestütztes Verfahren zur Flying- Spot-Thermografie vorgestellt. Die Anregung wird über einen Diodenlaser mit einem optischen Scanner realisiert. Bei der Auswertung kommt ein effizienter und robuster Algorithmus zum Einsatz, der direkt auf die mit der Kamera aufgenommene Thermografiesequenz angewendet werden kann, ohne auf eine Synchronisation zwischen Kamera und Lasersystem angewiesen zu sein. Daher eignet sich diese Herangehensweise besonders zur Nachrüstung bestehender Thermografiesysteme. Die prinzipielle Eignung dieser Methode wird anhand einer Messung an einem Schienenstück mit Rollkontaktermüdungsrissen gezeigt. Als Referenzverfahren werden die Magnetpulverprüfung und eine auf GMR (Giant Magnetoresistance)- Sensoren basierende Streufeldmessung herangezogen. Mit dem thermografischen Verfahren konnten sämtliche enthaltenen Fehler erkannt werden. Dabei wurden Risse im mm-Abstand getrennt nachgewiesen, was etwa der geometrischen Auflösung der eingesetzten Kamera entspricht. T2 - Thermographie-Kolloquium 2011 CY - Stuttgart, Germany DA - 29.09.2011 KW - Flying-Spot Thermografie KW - Diodenlaser KW - Rissortung KW - Magnetpulverprüfung KW - GMR-Sensoren PY - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-246220 SN - 978-3-940283-36-8 IS - DGZfP-BB 130 (Vortrag 09) SP - 1 EP - 6 PB - Deutsche Gesellschaft für zerstörungsfreie Prüfung e.V. (DGZfP) AN - OPUS4-24622 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reimund, Verena A1 - Pelkner, Matthias A1 - Neubauer, Andreas A1 - Thomas, Hans-Martin A1 - Kreutzbruck, Marc T1 - Automatische Detektion von Rissen in Stahlbauteilen unter Verwendung von GMR-Sensoren bei der magnetischen Streuflussprüfung N2 - GMR-Sensor Arrays ermöglichen eine örtlich hoch aufgelöste Messung magnetischer Streufeldamplituden an Stahlbauteilen, bei der abhängig von der Größe der zu prüfenden Oberfläche erhebliche Datenmengen erzeugt werden. Eine automatische Detektion von Rissen kann anschließend mittels digitaler Bildverarbeitung erreicht werden, welche hauptsächlich auf einer Kantenerkennung basiert. Diese wurde anhand einer Magnetometer-Messung getestet, die an einem zylindersymmetrischem Bauteil mit funkenerosiv eingebrachten Rissen geringer Tiefe durchgeführt wurde. Die erzielte Selektion der Defekte wird für eine angestrebte Rekonstruktion der Defektgeometrie benötigt. T2 - DGZfP-Jahrestagung 2011 CY - Bremen, Deutschland DA - 30.05.2011 KW - GMR-Sensor KW - Streuflussprüfung PY - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-253451 SN - 978-3-940283-33-7 IS - DGZfP-BB 127 (Mo.3.C.4) SP - 1 EP - 7 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) AN - OPUS4-25345 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Pelkner, Matthias A1 - Neubauer, Andreas A1 - Blome, Mark A1 - Reimund, Verena A1 - Thomas, Hans-Martin A1 - Kreutzbruck, Marc ED - Chady, T. ED - Gratkowski, S. ED - Takagi, T. ED - Udpa, S.S. T1 - Flux leakage measurements for defect characterization using NDT adapted GMR sensors N2 - High-precision magnetic field sensors are of increasing interest in non destructive testing (NDT). In particular GMR-sensors (giant magneto resistance) are qualified because of their high sensitivity, high signal-to-noise ratio and high spatial resolution. We performed magnetic flux leakage measurements of artificial cracks with a GMR-gradiometer and a 3-axes GMR-magnetometer. Cracks of a depth of 44 μm still could be detected with a sufficient high signal-to-noise ratio. A semi-analytic magnetic dipole model was used for swiftly predicting magnetic stray fields. The reliable reconstruction based on measurements of artificial rectangular-shaped defects is demonstrated. KW - GMR KW - NDT KW - Magnetic flux leakage KW - Reconstruction PY - 2011 SN - 978-1-60750-749-9 SN - 1383-7281 N1 - Serientitel: Studies in applied electromagnetics and mechanics – Series title: Studies in applied electromagnetics and mechanics VL - 35 SP - 217 EP - 224 PB - IOS Press CY - Amsterdam, The Netherlands AN - OPUS4-25374 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Neubauer, Andreas A1 - Kreutzbruck, Marc T1 - Automatisierte Streuflussprüfung und Bewertung von Zylinderlagerringen unter Anwendung von GMR-Sensorarrays T2 - DACH-Tagung (DGZfP-Jahrestagung) CY - Graz, Austria DA - 2012-09-17 PY - 2012 AN - OPUS4-27819 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Neubauer, Andreas A1 - Kreutzbruck, Marc T1 - Design und Charakterisierung ZfP-angepasster GMR-Sensorarrays T2 - DACH-Tagung (DGZfP-Jahrestagung) CY - Graz, Austria DA - 2012-09-17 PY - 2012 AN - OPUS4-27820 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Reimund, Verena A1 - Neubauer, Andreas A1 - Panke, Nicolai A1 - Erthner, Thomas A1 - Kreutzbruck, Marc T1 - Angepasste Wirbelstromsonden mit GMR Sensoren für die zerstörungsfreie Prüfung von Alluminium T2 - DGZFP-Jahrestagung 2013 CY - Dresden, Germany DA - 2013-05-06 PY - 2013 AN - OPUS4-29115 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Erthner, Thomas A1 - Kreutzbruck, Marc T1 - Zerstörungsfreie Prüfung von Lagerschalenringen T2 - Hannover Messe 2013 CY - Hanover, Germany DA - 2013-04-08 PY - 2013 AN - OPUS4-29116 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias T1 - Angepasste GMR-Sensorarrays für die Zerstörungsfreie Prüfung T2 - DGZfP Arbeitskreis Berlin, 347. Sitzung CY - Berlin, Germany DA - 2013-02-12 PY - 2013 AN - OPUS4-29119 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 - Kreutzbruck, Marc T1 - Automatisierte Streuflussprüfung von Zylinderlagerringen mit GMR-Sensoren T2 - 10. VDI-Fachtagung Gleit- und Wälzlagerungen CY - Schweinfurt, Germany DA - 2013-04-23 PY - 2013 AN - OPUS4-29120 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kreutzbruck, Marc A1 - Pelkner, Matthias A1 - Gaal, Mate A1 - Daschewski, Maxim A1 - Brackrock, Daniel T1 - Evolution of modern NDT-methods for the inspection of lightweight components N2 - NDT is a multidisciplinary research area fusing the disciplines of natural Science and engineering. Particularly in the early development stages of a new testing method, feasibility investigations focus on the fundamental physical interaction between the sensing mechanism and specimen. Research activities during subsequent phases of modular prototype development, technical System Integration and Validation primarily attempt to solve the practical engineering and real-life aspects of a testing method. We show several examples of new methods in different stages of development and highlight the potential for further industrial use. The first section deals with Steel surfaces of lightweight components which are inspected with pm-sized magneto resistive sensor arrays. This quantitative magnetic stray field approach combines high spatial resolution and very high sensitivity, enabling the user to detect even very small micro-defects. Tuming to CFRP components we also show new developments in airbome ultrasonic testing. Here we use ferroelectret foils to reduce the acoustical mismatch between transducer and air, which enhances the signal-to-noise ratio. A further example illuminates the use of metallic nano layers as a broadband thermo acoustical emitter. Their use provides both high sound pressures and very broadband Signal characteristics. When it comes to CFRP components and other anisotropic and highly Scattering materials, ultrasonic matrix arrays in conjunction with many angles of incidences per transducer position can help to enhance the statistics of a testing problem. In the field of conventional water-coupled UT testing we also show the use of matrix array transducers providing a tomographic-like 3D-image of impact damage in CFRP samples. T2 - 12th International conference of the Slovenian society for non-destructive testing - Application of contemporary non-destructive testing in engineering CY - Portoroz, Slovenia DA - 04.09.2013 KW - GMR-sensors arrays KW - Air coupled ultrasonics KW - Thermo acoustical transducers KW - Matrix arrays PY - 2013 SN - 978-961-93537-0-7 SP - 303 EP - 314 AN - OPUS4-29245 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 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-271325 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 - 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 - 2011-07-17 KW - GMR KW - Magnetic flux leakage KW - NDE KW - Sensor array PY - 2012 SN - 978-0-7354-1013-8 U6 - 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 - CONF A1 - Pelkner, Matthias T1 - Automatisierte Streuflussprüfung von Lagerringen mit GMR-Sensorarrays T2 - Sensorik und Messtechnik für Schienenfahrzeuge (Fokussierte Thementage 2013) CY - Berlin, Germany DA - 2013-09-26 PY - 2013 AN - OPUS4-29172 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias T1 - Angepasste GMR-Sensorarrays für die zerstörungsfreie Prüfung T2 - VDI/VDE-Expertenforum, Messe Sensor & Test CY - Dresden, Germany DA - 2013-05-14 PY - 2013 AN - OPUS4-29135 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ehlers, Henrik A1 - Thewes, R. A1 - Pelkner, Matthias T1 - Online Process Monitoring for Additive Manufacturing Using Eddy Current Testing With Magnetoresistive Sensor Arrays N2 - The rising popularity of additive manufacturing processes leads to an increased interest in possibilities and methods for related process monitoring. Such methods ensure improved process quality and increase the understanding of the manufacturing process, which in turn is the basis for stable component quality, e.g., required in the aerospace industry or in the medical sector. For laser powder bed fusion, a handful of process monitoring tools already exist, such as optical tomography, thermography, pyrometry, imaging, or laser power monitoring. Although these tools provide helpful information about the process, more information is required for an accurate in-depth understanding. In this article, advanced approaches in eddy current testing (ET) are combined, such as single wire excitation, magnetoresistive (MR) sensor arrays, and heterodyning to build up a system that can be used for online process monitoring of laser powder bed fusion. In addition to detailed information about the developed ET system and underlying signal processing, the first results of magnetoresistance-basedonline ET during the laser powder fusion process are presented. While producing a step-shaped cuboid, each layer is tested during recoating. Test results show that not only the contours of the topmost layer are detected but also the contours of previous layers covered by powder. At an excitation frequency of 1 MHz, a penetration depth of approx. 400 μm is obtained. To highlight the possibilities of ET for online process monitoring of laser powder bed fusion, results are compared with postexposure images of the integrated layer control system (LCS). KW - Process monitoring KW - Eddy current testing KW - Giant magneto resistance (GMR) KW - Additive manufacturing KW - Laser powder bed fusion PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-560881 VL - 22 IS - 20 SP - 19293 EP - 19300 PB - IEEE CY - New York, NY AN - OPUS4-56088 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Stegemann, R. A1 - Lyamkin, V. A1 - Cabeza, S. A1 - Evsevleev, S. A1 - Pelkner, Matthias A1 - Bruno, Giovanni T1 - Subsurface and Bulk Residual Stress Analysis of S235JRC + C Steel TIG Weld by Diffraction and Magnetic Stray Field Measurements N2 - Background Due to physical coupling between mechanical stress and magnetization in ferromagnetic materials, it is assumed in the literature that the distribution of the magnetic stray field corresponds to the internal (residual) stress of the specimen. The correlation is, however, not trivial, since the magnetic stray field is also influenced by the microstructure and the geometry of component. The understanding of the correlation between residual stress and magnetic stray field could help to evaluate the integrity of welded components. Objective This study aims at understanding the possible correlation of subsurface and bulk residual stress with magnetic stray field in a low carbon steel weld. Methods The residual stress was determined by synchrotron X-ray diffraction (SXRD, subsurface region) and by neutron diffraction (ND, bulk region). SXRD possesses a higher spatial resolution than ND. Magnetic stray fields were mapped by utilizing high-spatial-resolution giant magneto resistance (GMR) sensors. Results The subsurface residual stress overall correlates better with the magnetic stray field distribution than the bulk stress. This correlation is especially visible in the regions outside the heat affected zone, where the influence of the microstructural features is less pronounced but steep residual stress gradients are present. Conclusions It was demonstrated that the localized stray field sources without any obvious microstructural variations are associated with steep stress gradients. The good correlation between subsurface residual stress and magnetic signal indicates that the source of the magnetic stray fields is to be found in the range of the penetration depth of the SXRD measurements. KW - Residual stress KW - Magnetic stray field KW - Synchrotron X-ray diffraction KW - Neutron diffraction KW - TIG welding PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-547419 VL - 62 IS - 6 SP - 1017 EP - 1025 PB - Springer AN - OPUS4-54741 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - D'Accardi, E. A1 - Krankenhagen, Rainer A1 - Ulbricht, Alexander A1 - Pelkner, Matthias A1 - Pohl, Rainer A1 - Palumbo, D. A1 - Galietti, U. T1 - Capability to detect and localize typical defects of laser powder bed fusion (L‑PBF) process: an experimental investigation with different non‑destructive techniques N2 - Additive manufacturing (AM) technologies, generally called 3D printing, are widely used because their use provides a high added value in manufacturing complex-shaped components and objects. Defects may occur within the components at different time of manufacturing, and in this regard, non-destructive techniques (NDT) represent a key tool for the quality control of AM components in many industrial fields, such as aerospace, oil and gas, and power industries. In this work, the capability of active thermography and eddy current techniques to detect real imposed defects that are representative of the laser powder bed fusion process has been investigated. A 3D complex shape of defects was revealed by a μCT investigation used as reference results for the other NDT methods. The study was focused on two different types of defects: porosities generated in keyhole mode as well as in lack of fusion mode. Different thermographic and eddy current measurements were carried out on AM samples, providing the capability to detect volumetric irregularly shaped defects using non-destructive methods. KW - Additive Manufacturing KW - Defect detection KW - Thermography KW - Eddy-current testing KW - Micro-computed tomography PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-546680 SN - 2363-9512 VL - 7 IS - 6 SP - 1239 EP - 1256 PB - Springer AN - OPUS4-54668 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Maierhofer, Christiane A1 - Altenburg, Simon T1 - Process monitoring in metal AM@BAM, the project ProMoAM N2 - In this presentation we give an overview of activities regarding non-destructive testing of AM components during the manufacturing process. For this purpose, we installed different NDT methods inside the AM systems. The results obtained during the manufacturing process are presented and discussed. T2 - 74th IIW Annual Assembly and International Conference CY - Online meeting DA - 07.07.2021 KW - Non-destructive testing KW - Additive manufacturing KW - Online monitoring PY - 2021 AN - OPUS4-53186 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Ehlers, Henrik A1 - Casperson, Ralf A1 - Thewes, R. A1 - Jutkuhn, D. T1 - Hochauflösende online Wirbelstromprüfung von PBF LB/M Bauteilen mit GMR Arrays N2 - In den letzten Jahren haben additive Fertigungstechnologien an Bedeutung gewonnen. Für komplexe Funktionsbauteile oder die Produktion von Werkstücken in kleinen Stückzahlen kann das Laser-Pulverbettschmelzen eingesetzt werden. Hohe Sicherheitsanforderungen, z. B. in der Luft- und Raumfahrt, erfordern eine umfassende Qualitätskontrolle. Daher werden nach der Fertigung zerstörungsfreie Offline-Prüfverfahren wie die Computertomographie eingesetzt. In jüngster Zeit wurden zur Verbesserung der Rentabilität und Praktikabilität zerstörungsfreie Online-Prüfverfahren wie die optische Tomographie entwickelt. In diesem Beitrag wird die Anwendbarkeit der Wirbelstromprüfung mit GMR Sensoren für die online Prüfung von PBF-LB/M Teilen demonstriert. Die Ergebnisse einer online Wirbelstromprüfung mit GMR Sensoren und einer Ein-Draht-Anregung werden gezeigt. Während des Produktionsprozesses wird für jede Lage eine Wirbelstromprüfung durchgeführt. Trotz hochauflösender Arrays mit 128 Elementen wird durch eine angepasste Hardware die Prüfdauer geringgehalten. So kann die Messung während des Beschichtungsvorgangs durchgeführt werden, ohne den Fertigungsprozess signifikant zu verlangsamen. Eine online Wirbelstromprüfung eines stufenförmigen Testkörpers aus Haynes282 über 184 Lagen zeigt, dass die Kanten nicht nur in der aktuellen Lage detektiert werden können, sondern auch in einer Tiefe von 400 µm, wenn eine Anregungsfrequenz von 1,2 MHz gewählt wird. T2 - 2. Fachseminar Wirbelstromprüfung CY - Schweinfurt, Germany DA - 14.09.2022 KW - Wirbelstromprüfung KW - Additive Fertigung KW - Online Monitoring KW - GMR Arrays PY - 2022 AN - OPUS4-55895 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Bauer, R. A1 - Pham, M. A1 - Becker, T. A1 - Melzer, Michael A1 - Pelkner, Matthias A1 - Böhle, B. A1 - op den Winkel, F. A1 - Kliche, K. A1 - Welker, F. A1 - Becker, P. A1 - Pfeffer, A. A1 - Gerber, J. A1 - Holzhey, R. A1 - Wenzel, B. A1 - Slatter, R. A1 - Grönefeld, M. A1 - Nasaruk, M. A1 - Buß, R. A1 - Hille, P. A1 - Bartos, A. A1 - Schreiner, I. T1 - Anforderungen an die technische Darstellung von magnetischen Maßverkörperungen in Konstruktionszeichnungen N2 - Dieses Dokument legt Anforderungen an die technische Darstellung von Geometrie und magnetischen Eigenschaften in Konstruktionszeichnungen von magnetischen Maßverkörperungen fest und definiert die dazu notwendige Terminologie. KW - Magnetische Maßverkörperungen KW - Konstruktionszeichnungen KW - Terminologie KW - Magnetische Messsysteme PY - 2022 U6 - https://doi.org/10.31030/3359425 IS - DIN SPEC 91411:2022-08 SP - 1 EP - 48 PB - Beuth CY - Berlin AN - OPUS4-56631 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Stegemann, Robert A1 - Sonntag, Nadja A1 - Cabeza, Sandra A1 - Lyamkin, Viktor A1 - Bruno, Giovanni A1 - Skrotzki, Birgit A1 - Kreutzbruck, Marc T1 - Evaluation of high spatial resolution imaging of magnetic stray fields for early damage detection N2 - Metal magnetic memory (MMM) technique with associated ISO 24497-1:3 is gaining considerable interest in the magnetic NDT community. In contrast to traditional Magnetic Flux Leakage (MFL) testing, the inspection objects are not intentionally magnetized by an external magnetic field. Due to the physical coupling between mechanical stress and magnetization of ferromagnetic materials, it is assumed that the distribution of the residual MFL correspond to the internal stress of the specimen, or in the most general sense, to a degradation of the material. Usually, MMM measurements are performed by relatively bulky magnetic inspection sensors. The evaluation of local magnetic field distribution is limited thereby. Highprecision GMR (Giant Magneto Resistance) measurements in the micrometer regime can provide a higher degree of information due to better spatial resolution. We present a concise summary of studies on the correlation of magnetic structure and microstructure of steels. In particular, we compare residual stress measurements in S235JRC steel welds by means of neutron diffraction with high resolution magnetic field mappings. Results indicate a qualitative correlation between residual stresses and local stray field variation. In addition, stray field measurements of plastically deformed specimens for quasi-static and cyclic loading cases are discussed. The present study concludes that GMR sensors can detect inhomogeneous plastic deformations of S235JR steel in a very early stage, without specific signal processing according to the ISO 24497-1:3. T2 - QNDE - Review of Progress in Quantitative Nondestructive Evaluation CY - Atlanta, Georgia, USA DA - 18.07.2016 KW - NDT KW - MMM KW - GMR PY - 2016 AN - OPUS4-37101 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pohl, Rainer A1 - Kreutzbruck, Marc A1 - Commandeur, Colin A1 - Pelkner, Matthias T1 - Development of adapted GMR-probes for automated detection of hidden defects in thin steel sheets N2 - Thin steel sheets with a thickness of 0.3 mm and less are the base materials of many everyday life products (cans, batteries, etc.). Potential inhomogeneities such as non-metallic inclusions inside the steel can lead to a rupture of the sheets when it is formed into a product such as a beverage can. Therefore, there is a need to develop automated NDT techniques to detect hidden defects and inclusions in thin sheets during production. For this purpose Tata Steel Europe and BAM, the Federal Institute for Materials Research and Testing (Germany), collaborate in order to develop an automated NDT-system. Defect detection systems have to be robust against external influences, especially when used in an industrial environment. In addition, such a facility has to achieve a high sensitivity and a high spatial resolution in terms of detecting small inclusions in the μm-regime. In a first step, we carried out a feasibility study to determine which testing method is promising for detecting hidden defects and inclusions inside ferrous thin steel sheets. Therefore, two methods were investigated in more detail – magnetic flux leakage testing (MFL) using giant magneto resistance sensor arrays (GMR) as receivers [1,2] and eddy current testing (ET). The capabilities of both methods were tested with 0.2 mm-thick steel samples containing small defects with depths ranging from 5 μm up to 60 μm. Only in case of GMRMFL-testing, we were able to detect parts of the hidden defects with a depth of 10 μm trustworthily with a SNR better than 10 dB. Here, the lift off between sensor and surface was 250 μm. On this basis, we investigated different testing scenarios including velocity tests and different lift offs. In this contribution we present the results of the feasibility study leading to first prototypes of GMR-probes which are now installed as part of a demonstrator inside a production line. T2 - Review of Progress in Quantitative Nondestructive Evaluation CY - Minneapolis, MN, USA DA - 26.07.2015 KW - GMR KW - NDT PY - 2016 U6 - https://doi.org/10.1063/1.4940464 VL - 1706 SP - Article Number: 020018 PB - Amer institute physics CY - Melville, New York, USA AN - OPUS4-36100 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pelkner, Matthias A1 - Reimund, Verena A1 - Erthner, Thomas A1 - Kreutzbruck, Marc T1 - Size adapted GMR arrays for the automated inspection of surface breaking cracks in roller bearings N2 - Their small size together with a remarkable field sensitivity are the most prominent features of present-day GMR sensors paving the way for various applications in automated non-destructive testing (NDT). This work presents a prototype for fast and automated magnetic testing of roller bearings. A local magnetization unit excites the magnetic field inside the bearing. As a result of a design study and the following wafer fabrication the probe was equipped with NDT-adapted GMR sensor arrays in which 48 elements measures the field response. The detection of artificial and 40 µm deep defects could be resolved with a SNR better than 20 dB. In addition, we report of first results of a POD (Probability of Detection) analysis using GMR sensors to investigate bearings with EDM (electronic discharge machining) notches having depths down to 10 µm. Finally, we estimate successfully the depth of a 57 µm notch from the measured data. KW - Giant magneto resistance KW - Non-destructive testing KW - Magnetic flux leakage KW - Sensor array PY - 2014 U6 - https://doi.org/10.3233/JAE-141866 SN - 1383-5416 SN - 0925-2096 VL - 45 IS - 1-4 SP - 473 EP - 479 PB - IOS Press CY - Amsterdam, The Netherlands AN - OPUS4-31278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sergeeva-Chollet, N. A1 - Decitre, J.-M. A1 - Fermon, C. A1 - Pelkner, Matthias A1 - Reimund, Verena A1 - Kreutzbruck, Marc ED - Chimenti, D.E. ED - Bond, L.J. ED - Thompson, D.O. T1 - Development of eddy current probes based on magnetoresistive sensors arrays N2 - Eddy Current Technique is a powerful method for detection of surface notches and of buried flaws during inspection of metallic parts. Recent EC array probes have demonstrated a fast and efficient control of large surfaces. Nevertheless, when the size of flaws decreases or the defect is rather deep, traditional winding coil probes turn out to be useless. Magnetoresistive sensors present the advantages of flat frequency response and micron size. These sensors are hence very attractive for the detection of buried defects that require low frequencies because of skin depth effect. An optimization of the probe with magnetoresistive sensors as receivers has been made by simulations using CIVA software and finite elements methods with OPERA. EC probes for buried flaw detection have been designed. Experimental results have been compared with simulations. T2 - 40th Annual review of progress in quantitative nondestructive evaluation CY - Baltimore, Maryland, USA DA - 2013-07-21 KW - Eddy current KW - Magnetic sensor PY - 2014 SN - 978-0-7354-1212-5 SN - 978-0-7354-1211-8 U6 - https://doi.org/10.1063/1.4864981 SN - 0094-243X N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings VL - 1581 33B SP - 1374 EP - 1379 PB - AIP Publishing AN - OPUS4-31279 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Reimund, Verena A1 - Erthner, Thomas A1 - Panke, Nicolai A1 - Kreutzbruck, Marc ED - Chimenti, D.E. ED - Bond, L.J. ED - Thompson, D.O. T1 - Automated inspection of surface breaking cracks using GMR sensor arrays N2 - We present a prototype for automated magnetic stray field testing of ferromagnetic roller bearings. For this purpose NDE-adapted GMR sensor arrays (giant magneto resistance) are used for the detection of surface breaking cracks. The sensors are miniaturized down to the lower µm-regime to achieve adequate spatial resolution. In doing so, sensor arrays with up to 48 elements are used to inspect the bearing surface within a few seconds only. In contrast to magnetic particle inspection (MPI), where the global magnetization requires a further inspection step and succeeding demagnetization, the presented prototype only locally magnetize the surface area in the vicinity of the GMR Sensors. For the local magnetization, the applied sub-surface magnetic field was simulated and proofed for detecting flaws with a depth of a few 10 µm. By multiplexing the sensor array with an adapted read out electronics we quasi simultaneously detect the normal field component of about 100µm above the surface. The detection of artificial notches with a depth of 40 µm and more could be resolved with a SNR better than 20 dB. The presented testing facility is fast and provides a step towards automated testing of safety relevant steel components. T2 - 40th Annual review of progress in quantitative nondestructive evaluation CY - Baltimore, Maryland, USA DA - 2013-07-21 KW - GMR KW - Magnetic flux leakage KW - Sensor array KW - Non-destructive testing PY - 2014 SN - 978-0-7354-1212-5 SN - 978-0-7354-1211-8 U6 - https://doi.org/10.1063/1.4864984 SN - 0094-243X N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings VL - 1581 33B SP - 1393 EP - 1399 PB - AIP Publishing AN - OPUS4-31280 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Reimund, Verena A1 - Blome, Mark A1 - Thomas, Hans-Martin A1 - Kreutzbruck, Marc T1 - 3D-GMR-Messung an Referenzbauteilen und Rekonstruktion der Rissparameter N2 - Zunehmend werden hochpräzise Magnetfeldsensoren in der Materialprüfung verwendet. Aus dem Zoo der Magnetfeldsensoren eignen sich GMR-Sensoren (Giant Magneto Resistance) aufgrund ihrer hohen Feld- Empfindlichkeit, ihrem hohen Signal-Rausch-Verhältnis sowie ihrer kleinen Sensorflächen (verbunden mit einer hohen Ortsauflösung) hierfür im Besonderen. Mit GMR-Sensoren wurden Risse untersucht und konnten mit einer Tiefe ≤ 50 µm noch mit einem guten Signal-Rausch-Verhältnis aufgelöst werden. Die an Prüfkörpern mit künstlich eingebrachten Defekten gemessenen Streufeldsignale wurden anhand von analytischen Lösungen verifiziert. Anhand der analytischen Lösungen wurden auch Defektparameter zu den aufgezeichneten Signalen rekonstruiert. T2 - DGZfP-Jahrestagung 2010 CY - Erfurt, Deutschland DA - 2010-05-10 PY - 2010 SN - 978-3-940283-26-9 IS - DGZfP-BB 122 (Mo.3.A.4) SP - 1 EP - 9 CY - Berlin AN - OPUS4-21881 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Blome, M. A1 - Reimund, Verena A1 - Thomas, Hans-Martin A1 - Kreutzbruck, Marc T1 - Flux Leakage Measurements for Defect Characterization Using a High Precision 3-Axial GMR Magnetic Sensor T2 - The 15th International Workshop on Electromagnetic Nondestructive Evaluation (ENDE) CY - Szczecin, Poland DA - 2010-06-13 PY - 2010 AN - OPUS4-23365 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Blome, Mark A1 - Reimund, Verena A1 - Thomas, Hans-Martin T1 - 3D-GMR-Messungen an Referenzbauteilen und Rekonstruktion von Rissgeometrien T2 - DGZfP-Jahrestagung 2010 CY - Erfurt, Germany DA - 2010-05-10 PY - 2010 AN - OPUS4-21759 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Blome, Mark A1 - Pelkner, Matthias A1 - Reimund, Verena A1 - Kreutzbruck, Marc T1 - Flux leakage measurements for defect characterization using a high precision 3-axial GMR magnetic sensor T2 - 15. ITG/GMA-Fachtagung - Sensoren und Messsysteme 2010 CY - Nürnberg, Deutschland DA - 2010-05-18 PY - 2010 SN - 978-3-8007-3260-9 IS - 151/A6 SP - 809 PB - VDE-Verl. CY - Berlin; Offenbach AN - OPUS4-22963 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Pohl, Rainer A1 - Kreutzbruck, Marc A1 - Commandeur, C. T1 - Development of adapted GMR-probes for automated detection of hidden defects in thin steel sheets T2 - Review of Progress in Quantitative Nondestructive Evaluation CY - Minneapolis (USA) DA - 2015-07-27 PY - 2015 AN - OPUS4-33863 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Pohl, Rainer A1 - Erthner, Thomas A1 - Stegemann, Robert A1 - Kreutzbruck, Marc A1 - Sergeeva-Chollet, N. T1 - Eddy current testing with high-spatial resolution probes using MR arrays as receivers T2 - 7th International Symposium on NDT in Aerospace CY - Bremen DA - 2015-11-16 PY - 2015 AN - OPUS4-34913 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Pohl, Rainer A1 - Erthner, Thomas A1 - Kreutzbruck, Marc A1 - Commandeur, C. T1 - Detection of hidden defects in thin steel plates using GMR sensor arrays N2 - At BAM, the Federal Institute for Materials Research and Testing, a group of scientists develops NDT-applications based on GMR sensor technology. In particular, the knowledge gained in the field of automated testing systems based on the magnetic flux leakage (MFL) were combined with GMR sensors to achieve high resolution testing of ferromagnetic materials. In cooperation with Europe's second largest steel producer, Tata Steel Europe, BAM is working on solutions for the detection of small inhomogeneities in thin steel plates. The objective is to incorporate an automated testing facility in a production line. Before setting up an automated testing system, a feasibility study was carried out in order to verify the ability of GMR-MFL-testing and eddy current testing (ET) for the detection of hidden defects in thin steel plates. For this purpose, Tata Steel Europe fabricated in a first step test samples of 0.2 mm thick steel plates in which defects of different depth (5 – 60 µm) were introduced. Only in case of GMR-MFL-testing, we were able to detect parts of the hidden defects trustworthily with a SNR better than 10 dB. The lift off between sensor and surface was 250 ìm. On this basis, we investigated different testing scenarios including velocity tests and different lift offs. The achieved results for this special testing problem were presented leading to a practical example for GMR-based testing and paving the way to an automated testing system in a production line. T2 - ECNDT 2014 - 11th European conference on non-destructive testing CY - Prague, Czech Republic DA - 2014-10-06 KW - Magnetic flux leakage KW - GMR KW - Hidden defects PY - 2014 UR - http://www.ndt.net/events/ECNDT2014/app/content/Paper/286_Pelkner.pdf SN - 978-80-214-5018-9 SP - 1 EP - 7(?) AN - OPUS4-32234 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Reimund, Verena A1 - Pelkner, Matthias A1 - Kreutzbruck, Marc A1 - Haueisen, J. T1 - Sensitivity analysis of the non-destructive evaluation of micro-cracks using GMR sensors N2 - Micro-cracks in a magnetized ferromagnetic material cause stray fields that can be observed using giant magnetoresistive (GMR) sensors. This work investigates the applicability of GMR sensors to the non-destructive evaluation of micro-cracks via the observation of stray fields. For this purpose, our measurement setup is assessed using a fast new sensitivity analysis based on adjoint states, employing the finite-element method. A model for the GMR sensor is developed and verified. We are able to resolve micro-cracks with an opening of 3 µm and a depth of 30 µm. GMR positioning inaccuracies are analyzed. KW - Adjoint sensitivity analysis KW - Inverse problem KW - Magnetic stray field KW - Magneto-statics PY - 2014 U6 - https://doi.org/10.1016/j.ndteint.2014.02.003 SN - 0963-8695 VL - 64 SP - 21 EP - 29 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-32236 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Erthner, Thomas A1 - Kreutzbruck, Marc A1 - Commandeur, C. A1 - Pohl, Rainer T1 - Detection of hidden defects in thin steel plates using GMR sensor arrays T2 - ECNDT 2014 CY - Prag (Tschechien) DA - 2014-10-06 PY - 2014 AN - OPUS4-32154 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Erthner, Thomas A1 - Kreutzbruck, Marc A1 - Commandeur, C. A1 - Pohl, Rainer T1 - Detektion verdeckter Defekte in dünnen Stahlblechen mit GMR-Sensoren T2 - DGZfP-Jahrestagung 2014 CY - Potsdam DA - 2014-05-26 PY - 2014 AN - OPUS4-32155 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Erthner, Thomas A1 - Kreutzbruck, Marc A1 - Sergeeva-Chollet, N. A1 - Reimund, Verena T1 - MR-based eddy current probe desing for hidden defects T2 - ECNDT 2014 CY - Prag (Tschechien) DA - 2014-10-06 PY - 2014 AN - OPUS4-32156 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Commandeur, C. A1 - Erthner, Thomas A1 - Kreutzbruck, Marc A1 - Pohl, Rainer T1 - Detektion verdeckter Defekte in dünnen Stahlblechen mit GMR-Sensoren N2 - Seit einigen Jahren beschäftigt sich eine Gruppe der BAM mit der Entwicklung angepasster GMR-Sensorik (giant magneto resistance, Riesenmagnetwiderstand) für spezielle ZfP-Probleme. Hierbei wurden reichhaltige Erfahrungen auf dem Gebiet der automatisierten Streuflussprüfung mit GMR-Sensoren gesammelt (DACH-Tagung 2012, Graz). Die an der BAM gewonnenen Erkenntnisse veranlassten Europas zweitgrößten Stahlhersteller, Tata Steel Europe, mit der BAM eine Lösung für ein spezielles Prüfproblem zu finden. Ziel ist es, dünne Bleche im Fertigungsprozess auf kleinste Inhomogenitäten automatisiert zu prüfen. In einem ersten Schritt wurden durch die Tata Steel Europe 0,2 Millimeter starke Testbleche hergestellt, in die Fehler von 5-60 Mikrometern Tiefe eingebracht wurden. Anschließend wurden von der BAM vergleichende Prüfungen mit Wirbelstrom und GMR-Streufluss durchgeführt. Nur mit letzterer Methode gelang es, einen Teil der verdeckten Testfehler sicher zu detektieren. In einem zweiten Schritt wurden verschiedene Untersuchungen zur Praxistauglichkeit der Sensorik (Prüfgeschwindigkeit; Sensorabstand etc.) durchgeführt. Die Ergebnisse der verschiedenen Untersuchungen und ein möglicher Weg zum praktischen Einsatz der Sensorik werden vorgestellt. T2 - DGZfP-Jahrestagung 2014 CY - Potsdam, Germany DA - 2014-05-26 KW - GMR KW - Streufluss KW - Zerstörungsfreie Prüfung PY - 2014 UR - http://jt2014.dgzfp.de/portals/jt2014/BB/mo3b2.pdf SN - 978-3-940283-61-0 IS - DGZfP-BB 148 SP - Mo.3.B.2, 1 EP - 10 AN - OPUS4-32229 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Erthner, Thomas A1 - Reimund, Verena A1 - Kreutzbruck, Marc A1 - Sergeeva-Chollet, N. T1 - MR-based eddy current probe design for hidden defects N2 - We present a simulation study which pursues the objective to find probe geometries for a MR-based eddy current (EC) probe (MR magneto resistance, e.g., GMR giant magneto resistance, TMR tunnel magneto resistance). MR sensor technology exhibits two significant advantages compared with conventional coil systems. First, MR sensors are relatively frequency-independent within common EC-frequency ranges which enable us to operate them in hidden defects testing problems. Secondly, MR technology is well suited for miniaturization helping us to design small elements in the order of below 100 µm. In this paper simulation and experimental results obtained with the probes for low frequency application, i.e. for hidden defects detection are discussed. Our simulations are based on two different approaches for a better validation, a commercial finite element method software (Opera, Vectorfields) and the semi-analytical software CIVA. We investigated both coil arrangement in order to excite sufficient high eddy currents inside the test samples and position of MR-elements at the array chip. In doing so the MR sensors were positioned that they are not exposed to excitation fields. In addition, different coil geometries, in particular coil length, e.g. Ι = 20 mm, were analyzed in order to generate a consistent eddy current distribution beneath an array of up to 32 MR-elements. To prove obtained probe principles we built GMR-EC-probes. The first test measurements are in good agreement with the simulations performed by BAM and CEA. On basis of our findings the IMAGIC consortium developed new MR-EC-probes using integrated ASIC technology. T2 - ECNDT 2014 - 11th European conference on non-destructive testing CY - Prague, Czech Republic DA - 2014-10-06 KW - Magneto resistance (MR) KW - Eddy current (EC) KW - Simulation KW - GMR KW - Magnetic flux leakage KW - Hidden defects PY - 2014 UR - http://www.ndt.net/events/ECNDT2014/app/content/Paper/409_Pelkner.pdf SN - 978-80-214-5018-9 SP - 1 EP - 8(?) AN - OPUS4-32231 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pohl, Rainer A1 - Commandeur, C. A1 - Erthner, Thomas A1 - Kreutzbruck, M. A1 - Pelkner, Matthias T1 - GMR-Streufluss-Prüfsystem zur Detektion verdeckter Fehler in Feinblechen N2 - BAM und TATA Steel untersuchen gemeinsam, ob sich die Prüfung von ferritischen Feinblechen mit einer Stärke von etwa 0,2 mm während der Fertigung durch den Einsatz von GMR-Sensorik verbessern lässt. Hierzu wurde eine Vorstudie an Feinblechen mit eingebrachten Mikronuten durchgeführt. Diese Nuten variieren in ihrer Tiefe zwischen 5 μm und 60 μm und wurden verdeckt mit ZfP-angepassten GMR-Sensorarrays geprüft. Die Ergebnisse der Vorstudie zeigten, dass bei verdeckter Prüfung schon kleinste Defekte mit einer Tiefe von 10 μm - gleichbedeutend mit einer Restwanddicke von 90 % – mit einem SNR > 6 dB detektiert werden konnten, wobei der Abstand der Prüfsonde zur Oberfläche bis zu 500 μm betrug. Zudem wurden in der Vorstudie Untersuchungen zur Prüfgeschwindigkeit und Praxistauglichkeit durchgeführt. Basierend auf den hier gewonnenen Ergebnissen wird ein erster Demonstrator für eine zuverlässige Prüfung eines Teilbereiches von 50 mm des Feinbleches innerhalb einer Produktionslinie aufgebaut. Zum Einsatz kommen Prüfsonden mit jeweils 24 GMR-Sensorelementen. Hierbei wird das Ziel einer umfassenden Prüfung des Feinblechs über die gesamte Breite von 1200 mm angestrebt. Eine besondere Herausforderung stellt dabei die hohe Anzahl von mehr als 1000 Sensorelementen dar. Das hierfür entwickelte Prüfkonzept umfasst neben einer angepassten Erzeugung des Magnetfeldes die Entwicklung einer geeigneten schnellen und sicheren Elektronik für die neuen Mehrkanalprüfköpfe. Neben der Vorstellung des Prüfkonzeptes und seiner Eigenschaften vergleichen wir die erzielten Prüfergebnisse an verschiedenen Vergleichsfehlern mit denen der Vorstudie. T2 - DACH-Jahrestagung 2015 CY - Salzburg, Austria DA - 11.05.2015 KW - Streuflussprüfung KW - GMR PY - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-343354 SN - 978-3-940283-68-9 IS - DGZfP BB 152 SP - Mi.2.B.3, 1 EP - 9 AN - OPUS4-34335 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias T1 - Zerstörungsfreie Prüfung von Feinblechen T2 - Sensor & Test CY - Nürnberg DA - 2015-05-19 PY - 2015 AN - OPUS4-34648 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias T1 - Zerstörungsfreie Prüfung von Feinblechen T2 - Control CY - Stuttgart DA - 2015-05-05 PY - 2015 AN - OPUS4-34649 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 - Pelkner, Matthias A1 - Casperson, Ralf A1 - Pohl, Rainer A1 - Becker, Ben T1 - Conventional and HF Eddy Current Testing of Composite Pressure Vessels N2 - Composite pressure vessels consist of an internal liner (Steel, aluminum, or plastic) which stores the liquid or gas and CFRP (carbon fiber reinforced plastics) which serves as pressure resistance. These vessels comprise some advantages compared with conventional vessels made of steel or aluminum and their application grew strongly over the last decade. The reason for this trend is the tremendous weight saving. However, the long-time behavior for filling and discharging cycles and the creep strength of composite vessels is not fully understood. Therefore, BAM started an internal project to investigate degradation of these material systems. Normally, high-frequency eddy current testing (HF-ET, f > 10 MHz) is deployed for CFRP due to the low conductivity of the fibers, which is in the order of 0.01 MS/s, and the capacitive coupling between them. Nevertheless, in some cases conventional ET can be applied. Some first results using conventional ET for detecting leakages in the internal liners are already presented. This contribution gives an update of our investigation using both conventional and high-frequency ET. Therefore, we developed an ET equipment based on a vector network analyzer using frequencies between 300 kHz and 2 GHz. The focus concerns the study of the aging effects. T2 - 12th European conference on Non-Destructive Testing (ECNDT) CY - Gothenburg, Sweden DA - 11.06.2018 KW - Eddy current testing KW - Composite KW - Pressure vessel PY - 2018 AN - OPUS4-45302 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Stegemann, Robert A1 - Sonntag, Nadja A1 - Pohl, Rainer A1 - Kreutzbruck, Marc T1 - Benefits of GMR sensors for high spatial resolution NDT applications N2 - Magneto resistance sensors like GMR (giant magneto resistance) or TMR (tunnel magneto resistance) are widely used in industrial applications, examples are position measurement and read heads of hard disk drives. However, in case of non-destructive testing (NDT) applications these sensors, although their properties are outstanding like high spatial resolution, high field sensitivity, low cost and low energy consumption, never reached a technical transfer to an application beyond sci-entific scope. This paper deals with benefits of GMR/TMR sensors in terms of high spatial resolution testing for different NDT applica-tions. The first example demonstrates the preeminent advantages of MR-elements compared with conventional coils used in eddy current testing (ET). The probe comprises one-wire excitation with an array of MR elements. This led to a better spatial resolution in terms of neighboring defects. The second section concentrates on MFL-testing (magnetic flux leakage) with active field excitation during and before test-ing. The latter illustrated the capability of highly resolved crack detection of a crossed notch. This example is best suited to show the ability of tiny magnetic field sensors for magnetic material characterization of a sample surface. Another example is based on characterization of samples after tensile test. Here, no external field is applied. The magnetization is only changed due to external load and magnetostriction leading to a field signature which GMR sensors can resolve. This gives access to internal changes of the magnetization state of the sample under test. T2 - QNDE 2017 CY - Provo, Utah, USA DA - 16.07.2017 KW - GMR KW - Non-destructive testing KW - Sensor arrays KW - Spatial resolution PY - 2018 SN - 978-0-7354-1644-4 U6 - https://doi.org/10.1063/1.5031535 SN - 0094-243X VL - 1949 SP - UNSP 040001, 1 EP - 10 AN - OPUS4-45050 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Casperson, Ralf A1 - Pohl, Rainer A1 - Munzke, Dorit A1 - Becker, Ben A1 - Pelkner, Matthias T1 - Eddy current testing of composite pressure vessels N2 - The use of composite pressure vessels instead of conventional vessels made of steel or aluminum grew strongly over the last decade. The reason for this trend is the tremendous weight saving in case of composite vessels. However, the long-time behavior is not fully understood for filling and discharging cycles and creep strength and their influence on the CFRP coating (carbon fiber reinforced plastics) and the internal liner (steel, aluminum, or plastics). The CFRP ensures the pressure resistance while the inner liner is used as container for liquid or gas. To overcome the missing knowledge of ageing BAM started an internal project to investigate degradation of these material systems. Therefore, applicable testing methods like eddy current testing are needed. Normally, high-frequency eddy current testing (HF-ET, f > 10 MHz) is deployed for CFRP due to its low conductivity of the fiber, which is in the order of 0.01 MS/s, and the capacitive coupling between the fibers. Nevertheless, in some cases conventional ET can be applied. We show a concise summary of studies on the application of conventional ET of composite pressure vessels. T2 - QNDE 2017 CY - Provo, Utah, USA DA - 16.07.2017 KW - Eddy current KW - Composite KW - Pressure vessel PY - 2018 SN - 978-0-7354-1644-4 U6 - https://doi.org/10.1063/1.5031622 SN - 0094-243X VL - 1949 SP - UNSP 160004, 1 EP - 8 AN - OPUS4-45051 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Caetano, D. M. A1 - Rabuske, T. A1 - Fernandes, J. A1 - Pelkner, Matthias A1 - Fermon, C. A1 - Cardoso, S. A1 - Ribes, B. A1 - Franco, F. A1 - Paul, J. A1 - Piedade, M. A1 - Freitas, P. P. T1 - High-Resolution Nondestructive Test Probes Based on Magnetoresistive N2 - This paper discloses two high-sensitivity probes for Eddy Current Nondestructive Test (NDT) of buried and surface defects. These probes incorporate eight and 32 magnetoresistive sensors, respectively, which are optimized for high sensitivity and spatial resolution. The signal processing and interfacing are carried out by a full-custom application-specific integrated circuit (ASIC). The ASIC signal chain performs with a thermal input-referred noise of 30 nV/√Hz at 1 kHz, with 66 mW of power consumption, in a die with 3.7 × 3.4 mm 2 . NDT results are presented, showing that there is an increase in spatial resolution of surface defects when contrasted to prior art, enabling the probes to resolve defects with diameters of 0.44 mm, pitches of 0.6 mm, and minimum edge distance as low as 0.16 mm. The results also show that the probe for buried defects is a good all-round tool for detection of defects under cladding and multiple-plate flat junctions. KW - ASIC KW - Magnetoresistive sensor KW - Nondestructive testing KW - Eddy current testing KW - High resolution PY - 2019 U6 - https://doi.org/10.1109/TIE.2018.2879306 VL - 66 IS - 9 SP - 7326 EP - 7337 PB - IEEE AN - OPUS4-48239 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Pohl, Rainer A1 - Casperson, Ralf A1 - Ehlers, Henrik A1 - Pelkner, Matthias T1 - Elektromagnetische zerstörungsfreie Prüfverfahren N2 - Übersicht über die die im FB 8.4 bearbeiteten elektromagnetischen Prüfverfahren mit den Schwerpunkten bildgebende Wirbelstromprüfung, sensorbasierte Streuflussprüfung, magnetische Materialcharakterisierung und Sondenentwicklung. KW - Wirbelstromprüfung KW - Wirbelstromsenoren KW - GMR-Sensoren KW - Magnetische Materialcharakterisierung PY - 2020 SP - 1 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-51033 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Pohl, Rainer A1 - Erthner, Thomas A1 - Stegemann, Robert A1 - Kreutzbruck, Marc A1 - Sergeeva-Chollet, N. T1 - Eddy current testing with high-spatial resolution probes using MR arrays as receiver N2 - Magneto-resistive (MR) sensor arrays are suited for high resolution eddy current testing (ET) of aerospace components due to two significant advantages compared to conventional coil systems. First, to obtain high spatial resolution they can be manufactured down to the µm-regime without losing their outstanding field sensitivity. Secondly, MR technology has a relatively frequency-independent sensitivity in the range of common ET-frequencies thus providing a benefit for low frequency applications. This paper presents measurements using MR array probes consisting of 32 TMR-elements (tunnel magneto resistance), an ASIC, and subsequent readout components. A source for generating the eddy currents inside the material under test is also implemented onboard of the PCB. These probes were developed in the IMAGIC-project* for detection and imaging of surface breaking defects. The performance of the new sensor system has been investigated for several mock-ups, Aluminum and Titanium plate specimens having small adjacent boreholes with diameter of 0.44 mm and micro notches in the µm-range, respectively. To compare our results we used conventional eddy current probes. The MR sensor elements have a length of around 60 µm leading to a nearly 'point like' measurement. Neighbouring boreholes (depth 0.25 mm) with a separation of 0.6 mm between their centres could be resolved with a good SNR, and more important, the boreholes could be confidently distinguished using the TMR-probes. In case of conventional probes a reliable separation was not possible. In this paper we present the MR-ET-probes of the IMAGIC consortium and a comparison with conventional techniques. *The IMAGIC-project ('Integrated Magnetic imagery based on spIntronics Components', 2011 – 2014, project reference: 288381) was funded by the European Commission, Seventh Framework Programme. Further partners involved in the consortium beside BAM and CEA were INESC-ID and INESC-MN (Portugal), Sensitec GmbH (Germany), Tecnatom S.A. (Spain), and Airbus Group (France). T2 - 7th International symposium on NDT in aerospace CY - Bremen, Germany DA - 16.11.2015 KW - TMR KW - GMR KW - Sensor array KW - Eddy current testing (ET) KW - Aerospace PY - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-344254 SN - 978-3-940283-76-4 N1 - Serientitel: DGZfP-Proceedings – Series title: DGZfP-Proceedings IS - DGZfP-BB 156 SP - We.5.A.4, 1 EP - 8 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung e.v. (DGZfP) AN - OPUS4-34425 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Casperson, Ralf A1 - Heideklang, René A1 - Myrach, Philipp A1 - Onel, Yener A1 - Pelkner, Matthias A1 - Pohl, Rainer A1 - Stegemann, Robert A1 - Ziegler, Mathias A1 - Kreutzbruck, Marc T1 - Vergleich konventioneller und neuer Oberflächenprüfverfahren für ferromagnetische Werkstoffe N2 - Sicherheitsrelevante und zyklisch hoch belastete Bauteile erfordern zur Vermeidung von kostenintensiven Ausfällen besonders stabile Prozessparameter. Bereits sehr kleine Randzonenfehler können unter zyklischer Bauteilbelastung zu Risswachstum und letztendlich zum Bauteilversagen führen. Die frühzeitige Erkennung von Randzonenfehler in Hochleistungsbauteilen wie z.B. Zahnräder, Ritzelwellen und Kurbelwellen erfordert daher eine leistungsfähige zerstörungsfreie Oberflächenrissprüfung, die es ermöglicht in den hochbeanspruchten Funktionsflächen auch Härterisse, Schleifrisse oder Zundereinschlüsse zu detektieren. Hierzu sind in den letzten Jahren einige neue, innovative Oberflächenprüfverfahren wie die laserangeregte Thermografie und die Streuflussprüfung mit hochauflösenden GMR-Sensoren oder magnetooptischen Verfahren entwickelt worden. Zusätzlich zur hohen Empfindlichkeit zeichnen sich diese innovativen Verfahren durch einen schnellen und teils auch berührungslosen Einsatz aus. Da die noch relativ neu-en Verfahren naturgemäß noch nicht normativ verankert sind, wurden auch bereits erste Validierungen durchgeführt. Um die Leistungsfähigkeit der Verfahren eingehend zu untersuchen, erfolgten Testreihen an verschiedenen Testkörpern in Bezug auf Ortsauflösung, Empfindlichkeit, Automatisierung und Bewertung der Messsig-nale. Neben den neuen Verfahren und ihren ersten Schritten hin zur Validierung kamen als Referenz auch die „klassischen“ Verfahren der Magnetpulver- und Wirbelstromprüfung zum Einsatz, deren Leistungsfähigkeit durch angepasste Sondenentwicklung auch für sehr kleine Oberflächendefekte nochmals unter Beweis gestellt wurde. Zusätzlich wurde an einigen Testkörpern eine hochauflösende CT durchgeführt. Die Ergebnisse dieses Vergleiches werden vorgestellt und Möglichkeiten sowie Grenzen der einzelnen Verfahren herausgearbeitet. T2 - DACH-Jahrestagung 2015 CY - Salzburg, Austria DA - 11.05.2015 KW - Zerstörungsfreie Prüfung KW - Oberflächenprüfung KW - Vergleichskörper 1 KW - Sichtprüfung KW - Magnetpulverprüfung KW - Streuflussprüfung KW - Farbeindringprüfung KW - Wirbelstromprüfung KW - Thermografie KW - Radiografie PY - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-344262 SN - 978-3-940283-68-9 IS - DGZfP BB 152 SP - Mi.2.B.4, 1 EP - 11 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) AN - OPUS4-34426 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ehlers, Henrik A1 - Pelkner, Matthias A1 - Thewes, R. T1 - Heterodyne Eddy Current Testing Using Magnetoresistive Sensors for Additive Manufacturing Purposes N2 - In recent years additive manufacturing technologies have become widely popular. For complex functional components or low volume production of workpieces, laser powder bed fusion can be used. High safety requirements, e.g. in the aerospace sector, demand extensive quality control. Therefore, offline non-destructive testing methods like computed tomography are used after manufacturing. Recently, for enhanced profitability and practicality online non-destructive testing methods, like optical tomography have been developed. This paper discusses the applicability of eddy current testing with magnetoresistive sensors for laser powder bed fusion parts. For this purpose, high spatial resolution giant magnetoresistance arrays are utilized for testing in combination with a single wire excitation coil. A heterodyne principle minimizes metrology efforts. This principle is compared to conventional signal processing in an eddy current testing setup using an aluminum test sample with artificial surface defects. To evaluate the influence of the powder used in the manufacturing process on eddy current testing and vice versa, a laser powder bed fusion mock-up made from stainless steel powder (316L) is used with artificial surface defects down to 100 µm. This laser powder bed fusion specimen was then examined using eddy current testing and the underlying principles. KW - Eddy current testing KW - Heterodyning KW - Laser powder bed fusion KW - Giant magnetoresistance KW - Additive manufacturing KW - 316L PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-506140 SN - 1530-437X VL - 20 IS - 11 SP - 5793 EP - 5800 PB - IEEE AN - OPUS4-50614 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias T1 - Non-Destructive Testing - Electromagnetic Methods N2 - This presentation contains a short summary about the basics of eddy current testing and magnetic flux leakage testing. In addition, the main focus of the talk lies on the application of point-like sensors like GMR for NDT. T2 - 1st Training Event - ITN project GW4SHM CY - Online meeting DA - 23.11.2020 KW - GMR KW - Magnetic flux leakage testing KW - Eddy current testing PY - 2020 AN - OPUS4-51889 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Casperson, Ralf A1 - Pohl, Rainer T1 - Wirbelstromprüfung von Komposit-Druckbehältern N2 - Komposit-Druckgefäße für den Gefahrguttransport sowie für Wasserstoff-und Erdgasfahrzeuge bestehen aus einem lasttragenden Komposit und einer gasdichten, metallischen oder polymeren Barriereschicht (Liner). Zur Untersuchung der Integrität der Druckflaschen wurde die Wirbelstromprüfung eingesetzt. Hierbei wurden verschiedene Frequenzbereiche angewendet, um so die unterschiedlichen Materialien untersuchen zu können. Ziel der Untersuchungen war es, alterungsbedingte Schädigungen rechtzeitig zu detektieren. Der Vortrag stellt diese Ergebnisse vor. T2 - Carbon United - Gemeinsame Sitzung 3er-AG Zerstörungsfreie Werkstoff- u. Bauteilprüfung, Verbindungstechnik, Engineering CY - Online meeting DA - 07.12.2020 KW - Wirbelstromprüfung KW - CFK KW - Druckbehälter PY - 2020 AN - OPUS4-51892 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Ehlers, Henrik T1 - Electromagnetic testing for additive manufacturing N2 - With rising popularity and availability of additive manufacturing (AM), companies mainly in the aerospace sector, set high requirements on quality control of AM parts, especially produced with selective laser melting (SLM). Since it was shown that those parts are prawn to flaws like pores or cracks, every part needs to be tested. Therefore, NDT Methods, like eddy current testing (ET), could help to characterize SLM parts. Research on ET has shown, that offline ET with high spatial resolution MR (magneto resistive) sensor arrays is possible and that flaws as small as 50 µm could be detected while significantly reducing testing time. A first approach on automated online ET method for testing SLM parts is proposed in this contribution. T2 - IIW 2019 CY - Bratislava, Slovakia DA - 08.07.2019 KW - Additive manufacturing KW - Giant magneto resistance KW - Online monitoring KW - Eddy current testing PY - 2019 AN - OPUS4-50244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Ehlers, Henrik A1 - Pohl, Rainer A1 - Thewes, R. T1 - Hochauflösende Wirbelstromprüfung in der additiven Fertigung N2 - In den letzten Jahren wurden enorme Fortschritte bei der additiven Fertigung erzielt. So sind heutzutage industrielle Kleinserienfertigungen mit den 3D-Druckverfahren wirtschaftlich und konkurrenzfähig. Allerdings ist der Einsatz in Bezug auf sicherheitsrelevante Komponenten noch nicht vollumfänglich möglich. Grund hierfür sind die Materialeigenschaften 3D-gedruckter Komponenten, welche sich von den Eigenschaften konventionell gefertigter Materialien unterscheiden (Variationen im Gefüge, der Härte usw.). Ein Ansatz zur Lösung dieses Problems ist der Einsatz geeigneter online-Prüfverfahren zur Qualitätssicherung. Diese befinden sich –abgesehen von kamerabasierten Verfahren– aber noch im Entwicklungsstadium. Bei metallischen Werkstoffen stellt die Wirbelstromprüfung ein geeignetes Verfahren zur lagenweisen Online-Überprüfung des Fertigungsprozesses dar. Der Beitrag gibt einen Überblick über die derzeitige Patentlage sowie den Stand der Forschung zum Einsatz der Wirbelstromprüfung beim 3D-Druck metallischer Komponenten. Am Beispiel des pulverbasierten SLM-Verfahrens (selective laser melting; selektives Laserschmelzen) werden zudem Arbeiten der BAM und erste Ergebnisse einer angepassten Wirbelstromtechnik unter Verwendung von GMR-Sensoren (giant magneto resistance) vorgestellt. Hier wird das Ziel verfolgt, hochauflösend kleinste Fehler und Poren (im Bereich ≈100 µm) in der Oberfläche zu detektieren und durch lagenweises Abrastern einen 3D-Datensatz für die Qualitätskontrolle zu erstellen. Schließlich soll das System in der Lage sein, aktiv in den Fertigungsprozess einzugreifen, wodurch entweder die Produktion fehlerhafter Bauteile gestoppt wird oder durch geeignete Maßnahmen Fehler ausgeheilt werden. T2 - Wirbelstromprüfung – Aktuelle Anwendungen und Entwicklungen CY - Celle, Germany DA - 10.09.2019 KW - Additive Fertigung KW - Wirbelstromprüfung KW - Onlinemonitoring KW - Riesenmagnetwiderstand KW - GMR PY - 2019 AN - OPUS4-50245 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Casperson, Ralf A1 - Pohl, Rainer A1 - Munzke, Dorit A1 - Becker, Ben T1 - Eddy current testing of compsite pressure vessels N2 - An internal project at BAM (Bundesanstalt für Materialforschung und -prüfung) pursue the goal to develop methods and models to investigate ageing of CFRP (carbon fiber reinforced plastic) composites pressure vessels. One main challenge is the application of appropriate testing methods for detecting the influences of pressure cycles and creep behavior on the material. This contribution presents results we achieved using conventional eddy current testing (ET) and high frequency ET. Before investigating pressure vessels, we studied test samples with artifcial defects. Here, we could show that also conventional ET with low frequencies are useable for CFRP samples which have at bottom holes of different size and depth. On the basis of the received results we deployed conventional ET besides high-frequency applications in order to investigate pressure vessels of different material combinations like steel-CFRP, Aluminum-CFRP and synthetics-CFRP. The thickness of the CFRP varies from 4 mm up to 8 mm. Here, we could detect both defects in the metal liner and in the CFRP. T2 - ISEM 2017 CY - Chamonix, France DA - 03.09.2017 KW - CFRP KW - Eddy current testing high frequency PY - 2017 AN - OPUS4-43279 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pohl, Rainer A1 - Casperson, Ralf A1 - Maierhofer, Christiane A1 - Müller, Jan A1 - Pelkner, Matthias T1 - Gegenüberstellung von Wirbelstromprüfung und aktiver Thermografie an CFK-Versuchskörpern N2 - In vielen Bereichen der Technik haben Konstruktionen unter Einsatz von CFK-Bauteilen und Komponenten die klassischen Metalle abgelöst. Die zerstörungsfreie Prüfung solcher CFK-Bauteile gewinnt somit zunehmend an Bedeutung. Ein mögliches Prüfverfahren ist dabei die Wirbelstromprüfung. Aufgrund der relativ geringen elektrischen Leitfähigkeit von CFK-Komponenten kommt hierbei häufig die sogenannte HF-Wirbelstromprüfung zum Einsatz. In verschiedenen Untersuchungen der BAM konnten jedoch auch mit Wirbelstromprüfsystemen in niedrigen Frequenzbereichen gute Ergebnisse erzielt werden. Um die Möglichkeiten und Grenzen dieser konventionellen Wirbelstromprüfung auszuloten, wurden Messungen an Versuchskörpern durchgeführt, welche bereits bei der Validierung der Blitz- und Lock-in-Thermografie für neue Verfahrensnormen erfolgreich eingesetzt wurden. Ein Typ dieser Versuchskörper sind Flachproben aus CFK von 6 mm Dicke. In diesen wurden Flachbodenbohrungen mit Durchmessern zwischen 4 mm und 24 mm eingebracht. Die Restwandstärken liegen zwischen 0,06 mm und 3,66 mm. Ein weiterer CFK-Versuchskörper hat die Geometrie eines Stufenkeiles. Bei verschiedenen Stufenkeilen sind Wanddicken zwischen 1,4 mm und 5,4 mm realisiert worden. In diesen wurden künstliche quadratische Delaminationen mit Kantenlängen zwischen 2 mm und 20 mm eingebracht. Die Ergebnisse der Wirbelstromprüfung werden denen der aktiven Thermografie gegenübergestellt. Zur Nachbildung von Kompositwerkstoffen wurden die flachen Versuchskörper mit geeigneten Versuchskörpern aus Aluminium und Stahl kombiniert. Die Wirbelstromprüfungen wurden mit einem handelsüblichen Prüfgerät im Frequenzbereich zwischen 500 Hz und 3 MHz und entsprechend angepassten Sensoren durchgeführt. T2 - DGZfP Jahrestagung 2017 CY - Koblenz, Germany DA - 22.05.2017 KW - Wirbelstromprüfung KW - Aktive Thermografie KW - CFK PY - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-403607 SN - 978-3-940283-85-6 VL - 162 SP - 1 EP - 10 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) CY - Berlin AN - OPUS4-40360 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Stegemann, Robert T1 - GMR Sensor Arrays for High-Spatial Resolution Measurements in NDT-Applications N2 - Magneto resistive (MR) sensors are suited for a wide range of different applications. Especially due to their small sizes and their frequency-independent behaviour, they are eligible candidates for non-destructive testing methods where high spatial resolution is required. The use of specialized magnetic field probes enables not only a defect evaluation, but also a localized characterization of ferromagnetic materials. This paper presents some NDT (non-destructive testing) examples concerning magnetic flux leakage applications (MFL) and eddy current testing (ET). For MFL-testing we used an NDT-adapted GMR (Giant MR) sensor array for the detection of small inclusions in thin steel sheets. We also investigated the effects of microstructure on magnetic properties using GMR sensors. The ET-example describes an MR array probe consisting of 32 MR-elements, an ASIC, subsequent readout components and a one-wire excitation to generate eddy currents inside the material (developed in the EU-funded IMAGIC-project, 2011-2014, 7th Framework Programme). Using this MR-probe we achieved results with a better spatial resolved defect detection of neighbouring boreholes compared to “conventional” ET-probes. T2 - 14th Symposium Magnetoresistive Sensors and Magnetic Systems CY - Wetzlar, Germany DA - 21.03.2017 KW - GMR KW - Eddy current testing KW - Magnetic flux leakage PY - 2017 SP - 146 EP - 153 AN - OPUS4-39557 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Stegemann, Robert A1 - Pohl, Rainer T1 - GMR Sensor Arrays for High-Spatial Resolution Measurements in NDT-Applications N2 - Magneto resistive (MR) sensors are suited for a wide range of different applications. Especially due to their small sizes and their frequency-independent behaviour, they are eligible candidates for non-destructive testing methods where high spatial resolution is required. The use of specialized magnetic field probes enables not only a defect evaluation, but also a localized characterization of ferromagnetic materials. This paper presents some NDT (non-destructive testing) examples concerning magnetic flux leakage applications (MFL) and eddy current testing (ET). For MFL-testing we used an NDT-adapted GMR (Giant MR) sensor array for the detection of small inclusions in thin steel sheets. We also investigated the effects of microstructure on magnetic properties using GMR sensors. The ET-example describes an MR array probe consisting of 32 MR-elements, an ASIC, subsequent readout components and a one-wire excitation to generate eddy currents inside the material (developed in the EU-funded IMAGIC-project , 2011-2014, 7th Framework Programme). Using this MR-probe we achieved results with a better spatial resolved defect detection of neighbouring boreholes compared to “conventional” ET-probes. T2 - 14th Symposium Magnetoresistive Sensors and Magnetic Systems CY - Wetzlar, Germany DA - 21.03.2017 KW - GMR KW - Eddy current testing KW - Magnetic flux leakage PY - 2017 AN - OPUS4-39560 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stegemann, Robert A1 - Cabeza, Sandra A1 - Pelkner, Matthias A1 - Lyamkin, Viktor A1 - Sonntag, Nadja A1 - Bruno, Giovanni A1 - Skrotzki, Birgit A1 - Kreutzbruck, Marc T1 - Evaluation of high spatial resolution imaging of magnetic stray fields for early damage detection N2 - The paper discusses the evaluation of elastic and plastic strain states in two low-carbon steels of the same steel group with high spatial resolution GMR (giant magneto resistance) sensors. The residual stress distributions of tungsten inert gas welded plates were determined by means of neutron diffraction as a reference. The normal component of local residual magnetic stray fields arise in the vicinity of the positions of maximum stress. The experiments performed on flat tensile specimen indicate that the boundaries of plastic deformations are a source of stray fields. The spatial variations of magnetic stray fields for both the weld and the tensile samples are in the order of the earths magnetic field. T2 - 43rd Annual Review of Progress in Quantitative Nondestructive Evaluation, Volume 36 CY - Atlanta, Georgia, USA DA - 17.07.2016 KW - Plastic deformation KW - GMR KW - Neutron diffraction KW - Residual stress KW - Microstructure KW - Low carbon steel KW - TIG weld PY - 2017 SN - 978-0-7354-1474-7 U6 - https://doi.org/10.1063/1.4974688 SN - 0094-243X VL - 1806 IS - 1 SP - Article UNSP 110010-1 EP - 10 PB - AIP Publishing CY - Melville, NY 11747 AN - OPUS4-39279 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Pelkner, Matthias A1 - Kreutzbruck, Marc ED - Fermon, C. ED - Van de Voorde, M. H. T1 - Spin Electronics for Non Destructive Testing N2 - Electromagnetic methods are widely used in Non-destructive Testing industries (NDT). In order to meet the requirements, safety-relevant products and structures have to be tested reliably during production or within subsequent maintenance cycles. For this purpose industrial users call for adapted testing methods which allow the detection of relevant defects such as cracks and pore in ferromagnetic or conductive materials. Automated testing systems and the application of sensor arrays are of great interest in order to enhance inspection quality and to decrease testing time and costs. Magneto resistance (MR) sensors like giant magneto resistance (GMR) or tunnel magneto resistance sensor (TMR) have proofed their suitability in many NDT-applications due to their extraordinary properties which combine high field sensitivity, a high spatial resolution and low costs. Due to their small size these sensors can be useful – in addition to the pure detection task – for a more detailed defect characterization and defect reconstruction providing defect size, orientation and geometry. This chapter gives a brief introduction of electromagnetic testing methods, i.e., magnetic particle inspection (MPI) and eddy current testing (ET), followed by two different approaches for which MR sensor arrays were successfully adapted. KW - Magneto resistance KW - GMR KW - TMR KW - Non-destructive testing KW - Magnetic flux leakage KW - Eddy current PY - 2017 SN - 978-3-527-33985-3 SP - 81 EP - 102 PB - Wiley-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-41463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Stegemann, Robert A1 - Pohl, Rainer A1 - Casperson, Ralf A1 - Kreutzbruck, Marc T1 - Benefits of GMR sensors adapted for NDT applications N2 - Main concept of magnetism and, therefore, of magnetic imaging can be subdivided into different levels, macroscopic, magnetic domain, and atomic. While conventional sensor solutions cover only the macroscopic level, the spatial resolution of GMR (Giant Magneto Resistance) sensors go down to the domain scale. In addition, those low cost sensors are well suited for automotive and industrial applications, particularly high-speed solutions. Main reason is their outstanding performance in terms of high spatial resolution, high accuracy, high bandwidth combined with field sensitivity, energy efficiency and durability. In contrast to industrial use, down to the present day GMR sensors do not get beyond scientific scope in case of non-destructive testing (NDT) applications. Nevertheless, there are scientific and industrial NDT applications in which adapted GMR sensor can be promising compared to the conventional NDT methods. This contribution summarizes findings at the BAM over the last decade which demonstrates the preeminent properties of GMR-based testing solutions. This comprises the active and passive testing of different materials with hidden defects and flaws near geometric boundaries like edges where conventional methods meet their limits. Another promising application for adapted GMR sensors is the characterization of magnetic materials, where the sensors provide additional information on microstructure, mechanical stress state, phase transformations and their interaction with magnetic fields. The examples show the need and benefit of NDT adapted GMR sensors. T2 - QNDE - 44th Annual Review of Progress in Quantitative Nondestructive Evaluation CY - Provo, Utah, USA DA - 16.07.2017 KW - NDT KW - GMR KW - Magnetic flux leakage KW - Eddy current KW - Residual stress PY - 2017 AN - OPUS4-41465 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Casperson, Ralf A1 - Pohl, Rainer A1 - Munzke, Dorit T1 - Eddy Current testing of Composite Pressure Vessels N2 - The use of composite pressure vessels instead of conventional vessels made of steel or aluminum grew strongly over the last decade. The reason for this trend is the tremendous weight saving in case of composite vessels. However, the long-time behavior is not fully understood for filling and discharging cycles and creep strength and their influence on the CFRP coating (carbon fiber reinforced plastics) and the internal liner (steel, aluminum, or plastics) [1]. The CFRP ensures the pressure resistance while the inner liner is used as container for liquid or gas. To overcome the missing knowledge of ageing BAM started an internal project to investigate degradation of these material systems [2]. Therefore, applicable testing methods are needed. Normally, high-frequency eddy current testing (HF-ET, f > 10 MHz) is deployed for CFRP due to its low conductivity of the fiber, which is in the order of 0.01 MS/s, and the capacitive coupling between the fibers. Nevertheless, in some cases conventional ET can be applied. We show a concise summary of studies on the application of conventional ET of composite pressure vessels. T2 - QNDE - 44th Annual Review of Progress in Quantitative Nondestructive Evaluation CY - Provo, Utah, USA DA - 16.07.2017 KW - eddy current KW - composites KW - pressure vessels KW - CFRP PY - 2017 AN - OPUS4-41466 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pelkner, Matthias A1 - Casperson, Ralf A1 - Pohl, Rainer A1 - Munzke, Dorit A1 - Becker, Ben T1 - Eddy current testing of composite pressure vessels N2 - The application of composite pressure vessels is of great interest due to tremendous weight saving. Nevertheless, ageing of CFRP (carbon fiber reinforced plastic) composites pressure vessels underlies complex interactions between metallic liner and composite and is not fully understood yet. One main challenge is the application of appropriate testing methods for detecting the influences of pressure cycles and creep behavior on the material. This contribution presents results achieved by using conventional eddy current testing (ET) and high frequency ET. Here, we could show that also conventional ET with low frequencies are useable to investigate pressure vessels of different material combinations like aluminum-CFRP and synthetics-CFRP. KW - CFRP KW - Eddy current KW - Ageing KW - Composite PY - 2019 U6 - https://doi.org/10.3233/JAE-171044 VL - 59 IS - 4 SP - 1221 EP - 1226 PB - IOP Publ. Ltd. AN - OPUS4-47803 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Gaal, Mate A1 - Hufschläger, Daniel T1 - PALUP: Phased-Array-Technik für Luftultraschall-Prüfungen N2 - Im Forschungsvorhaben PALUP werden luftgekoppelte Phased-Array-Sender und -Empfänger entwickelt. Die Wandler basieren auf geladenen zellulären Polymeren, auch Ferroelektrete genannt, die piezoelektrische Eigenschaften und eine sehr geringe spezifische akustische Impedanz aufweisen, womit sie sich für den Bau von luftgekoppelten Ultraschallwandlern sehr gut eignen. T2 - 10. Forum Leichtbau CY - Berlin, Germany DA - 28.09.2023 KW - Luftultraschall KW - Phased Array Technik PY - 2023 AN - OPUS4-58529 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias T1 - Wirbelstromprüfung für die additive Fertigung N2 - Überblick über die derzeitige Entwicklungen für das Online-Monitoring additiver Fertigungsverfahren für metallische Werkstoffe mittels der Wirbelstromprüfung. Hierbei wird eine Einführung in die Wirbelstromprüfung gegeben sowie erste Entwicklungen hinsichtlich eines Online-Monitoring thematisiert. T2 - BAM Akademie: Qualitätssicherung in der additiven Fertigung CY - Online meeting DA - 26.10.2023 KW - Wirbelstromprüfung KW - Additive Fertigung KW - Online Monitoring PY - 2023 AN - OPUS4-58917 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Nicolicea, Alberto A1 - Kreuter, D. A1 - Melzer, Michael T1 - Einsatz neuartiger, flexibler Magnetfeldsensoren für die ZfP N2 - Die Magnetpulverprüfung ist eine weit verbreitete Prüfmethode für ferromagnetische Bauteile. Hierbei werden Oberflächenfehler wie Risse mit ferromagnetischem Pulver sichtbar gemacht, wodurch eine qualitative Bewertung des Bauteils ermöglicht wird. Allerdings können die Anzeigen kaum zu einer quantitativen Bewertung herangezogen werden. Hierfür sind Magnetfeldsensoren nötig, die die Stärke der Streufelder messen, wodurch z. B. die Tiefe der Risse abgeschätzt werden kann. Bei kommerziellen Magnetfeldsensoren sind die sensitiven Elemente auf Platinen angebracht bzw. in eine Verkapselung integriert. Hierdurch erhöht sich der Abstand der Elemente zur Oberfläche und kleine Fehler können unter Umständen nicht mehr detektiert werden. Auch wird eine automatisierte Prüfung komplexer Geometrien durch die starren Sonden erschwert. Um Streufelder von kleinen Fehlern in komplexen Bauteilen quantitativ bewerten zu können, validiert die BAM den Einsatz neuartiger, flexibler Magnetfeldsensoren. Hierbei sind die sensitiven Elemente auf flexiblen Folien aufgebracht und lassen sich verformen, wodurch sie auf viele mögliche Oberflächenformen appliziert werden können. Es wird ein geringerer Abstand der Elemente zur Oberfläche erreicht und Streufelder von kleinen Defekten können besser aufgelöst werden. Zudem verlieren die Sensoren durch Verformung weder ihre Sensitivität noch werden sie hierdurch zerstört. Dies macht diese Sensoren zu perfekten Kandidaten für die quantitative Bewertung von Rissstreufeldern in komplex geformten, ferromagnetischen Bauteilen. Der Beitrag präsentiert die Charakterisierung der Sensoren sowie erste Versuche an komplexen Bauteilen. Schließlich wird eine Einschätzung hinsichtlich weiterer Anwendungsmöglichkeiten gegeben. T2 - DGZfP Jahrestagung 2023 CY - Friedrichshafen, Germany DA - 15.05.2023 KW - Flexible Elektronik KW - Flexible Sensorik KW - Magnetischer Streufluss KW - GMR KW - ZfP PY - 2023 AN - OPUS4-58081 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pelkner, Matthias A1 - Ehlers, Henrik A1 - Thewes, R. T1 - Online Eddy Current Testing of PBF LB/M Parts Using GMR Sensor Arrays During Manufacturing N2 - In recent years, additive manufacturing technologies have gained in importance. Laser powder bed fusion can be used for complex functional components or the production of workpieces in small quantities. High safety requirements, e.g. in aerospace, demand comprehensive quality control. Therefore, non-destructive offline inspection methods such as computed tomography are used after production. Recently, online non-destructive testing methods such as optical tomography have been developed to improve profitability and practicality. In this presentation, the applicability of eddy current inspection using GMR sensors for online inspection of PBF-LB/M parts is demonstrated. Eddy current testing is performed for each layer during the production process at frequencies uo to 1.2 MHz. Despite the use of high-resolution arrays with 128 elements, the testing time is kept low by an adapted hardware. Thus, the measurement can be performed during the manufacturing process without significantly slowing down the production process. In addition to the approach, the results of an online eddy current test of a step-shaped test specimen made of Haynes282 are presented. T2 - European Conference on Non-Destructive Testing (ECNDT) 2023 CY - Lisbon, Potugal DA - 03.07.2023 KW - Eddy current KW - GMR KW - Additive manufacturing KW - In-situ monitoring KW - NDT PY - 2023 AN - OPUS4-58082 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stegemann, Robert A1 - Cabeza, Sandra A1 - Pelkner, Matthias A1 - Lyamkin, Viktor A1 - Pittner, Andreas A1 - Werner, Daniel A1 - Wimpory, R. A1 - Boin, M. A1 - Kreutzbruck, Marc A1 - Bruno, Giovanni T1 - Influence of the microstructure on magnetic stray fields of low-carbon steel welds N2 - This study examines the relationship between the magnetic mesostructure with the microstructure of low carbon steel tungsten inert gas welds. Optical microscopy revealed variation in the microstructure of the parent material, in the heat affected and fusion zones, correlating with distinctive changes in the local magnetic stray fields measured with high spatial resolution giant magneto resistance sensors. In the vicinity of the heat affected zone high residual stresses were found using neutron diffraction. Notably, the gradients of von Mises stress and triaxial magnetic stray field modulus follow the same tendency transverse to the weld. In contrast, micro-X-ray fluorescence characterization indicated that local changes in element composition had no independent effect on magnetic stray fields. KW - TIG-welding KW - GMR sensors KW - Magnetic stray field KW - Neutron diffraction KW - Residual stress KW - Microstructure KW - Low carbon steel PY - 2018 U6 - https://doi.org/10.1007/s10921-018-0522-0 SN - 0195-9298 SN - 1573-4862 VL - 37 IS - 3 SP - 66,1 EP - 18 PB - Springer US CY - New York AN - OPUS4-45855 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -