TY - CONF A1 - Krankenhagen, Rainer A1 - Chaudhuri, Somsubhro A1 - Pittner, Andreas A1 - Winterkorn, Rene A1 - de Finis, Rosa A1 - Palumbo, Davide A1 - Galietti, Umberto T1 - Thermographic investigation of the anisotropic behaviour of additively manufactured AISI316 steel using DED-Arc N2 - Additive manufacturing is one of the most promising techniques for industrial production and maintenance, but the specifics of the layered structure must be considered. The Direct Energy Deposition-Arc process enables relatively high deposition rates, which is favourable for larger components. For this study, specimens with different orientations were prepared from one AISI316 steel block – parallel and orthogonal to the deposition plane. Quasistatic tensile loading tests were carried out, monitored by an infrared camera. The obtained surface temperature maps revealed structural differences between both orientations. The consideration of surface temperature transients yields more details about the behaviour of the material under tensile loading than the conventional stress-strain-curve. These preliminary investigations were supplemented by thermographic fatigue trials. Although the anisotropy was also observed during fatigue loading the fatigue behaviour in general was the same, at least for both inspected specimens. The presented results demonstrate the abilities and the potential of thermographic techniques for tensile tests. T2 - 17th Quantitative Infrared Thermography Conference CY - Bologna, Italy DA - 07.07.2025 KW - Thermoelastic effect KW - Wire-arc-additive manufacturing KW - thermal stress analysis KW - fatigue testing PY - 2026 DO - https://doi.org/10.21611/qirt-2024-029 SP - 1 EP - 8 AN - OPUS4-65372 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witte, Julien A1 - Treutler, Kai A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Influence of Microstructure on the Machinability and Surface Integrity of Additively Manufactured Iron Aluminides N2 - The increasing global focus on energy and resource efficiency has stimulated a growing interest in additive manufacturing. AM offers economic advantages and enables an efficient use of materials. However, AM components often require subsequent mechanical post-processing, such as machining (e.g. milling), to achieve the final contours or surfaces. This is a particular challenge due to the heterogeneous and anisotropic nature of AM structures, which affect machining and the resulting component properties. High-performance materials such as iron aluminide represent a promising alternative to conventional high-temperature materials with a significant economic advantage. However, the strength and hardness properties, which are advantageous for applications in highly stressed lightweight components, pose a challenge for economical machining in addition to the AM microstructure properties. The difficult-to-cut material causes accelerated tool wear and insufficient surface quality. This study shows that crack-free additive manufacturing of the three-component system of iron-nickel-aluminum is possible, and advantages in terms of machinability compared to FeAl-AM components are achieved. The more homogeneous microstructure leads to a reduction in cutting forces, with positive effects on the machinability and optimized surface integrity. Ultrasonic assisted milling (USAM) offers great potential to address the major challenges posed by difficult-to-cut materials and additively manufactured weld structures. Therefore, this study focuses on assessing the transferability of previous positive results by USAM to the selected iron aluminide alloys. The machinability of the aluminides is analyzed by varying significant influencing variables in finish milling experiments and evaluated in terms of the loads on the tool and the resulting surface integrity. T2 - AA Meeting of Commission IX ‘Behavior of Metals subject to Welding’ CY - Rhodes, Greece DA - 08.07.2024 KW - Iron aluminide KW - Additive manufacturing KW - Machinability KW - Surface integrity KW - Ultrasonic-assisted milling PY - 2026 SP - 1 EP - 16 AN - OPUS4-65530 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bär, J. A1 - Kanna, N.K. A1 - Duarte, Larissa A1 - Madia, Mauro T1 - Determination of the Kitagawa-Takahashi Diagram using DC Potential Drop Measurements N2 - The Kitagawa-Takahashi Diagram is an important tool for describing the fatigue limit of components containing defects. The models used for its description differ, particularly in the transition region corresponding to the short crack regime. Therefore, for a reliable statement about the fatigue limit in this area, an experimental validation of the models is necessary. However, the standardized staircase method requires a large number of samples and has a long test duration. In this work, a method is presented that allows a simpler and faster validation of the Kitagawa-Takahashi Diagram in the region of short cracks. Rectangular notches with a defined width and depth were manufactured in flat samples of a low-alloyed steel with two different heat treatments using an engraving laser. This method allows a rapid production of very sharp notches without plastic deformation and with only a slight thermal influence on the surrounding material. The samples prepared in this way were fatigued with block wise increasing loads until failure. Cracks are detected by means of a Direct Current Potential Drop method. The length of the loading block (number of cycles) is determined by the measured potential drop. This procedure enables a reliable and precise determination of the limit stress for the respective notch size with low experimental effort and time consumption. The tests have shown that in case of the normalized steel none of the models describes the determined values for the fatigue limit. For the hardened steel, the plot of the fatigue limit as a function of the Murakami parameter √area in combination with the El Haddad model allows a satisfactory description of the measured values. T2 - 5th International Symposium on Fatigue Design and Material Defects CY - Trento, Italy DA - 14.05.2025 KW - Kitagawa-Takahashi diagram KW - Damage tolerance KW - Fatigue KW - Potential drop KW - Fracture mechanics PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655519 DO - https://doi.org/10.1016/j.prostr.2025.12.283 VL - 76 SP - 27 EP - 34 PB - Elsevier B.V. AN - OPUS4-65551 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Eddah, Mustapha A1 - Markötter, Henning A1 - Mieller, Björn A1 - Widjaja, Martinus Putra A1 - Beckmann, Jörg A1 - Bruno, Giovanni T1 - Multi-Energy High Dynamic Range (HDR) Synchrotron X-ray Computed Tomography applied to LTCC samples N2 - Synchrotron X-ray computed tomography (SXCT) is regularly used in materials science to correlate structural properties with macroscopic properties and to optimize manufacturing processes. The X-ray beam energy must be adapted to the sample properties, such as size and density. If both strongly and weakly absorbing materials are present, the contrast to the weakly absorbing materials is lost, resulting in image artifacts and a poor signal-to-noise ratio (SNR). One example is a low-temperature co-fired ceramics (LTCC), in which metal connections are embedded in a ceramic matrix and form 3-dimensional conducting structures. This article describes a method of combining SXCT scans acquired at different beam energies, significantly reducing metal artifacts, and improving image quality. We show how to solve the difficult task of merging the scans at low and high beam energy. Our proposed merging approach achieves up to 35% improvement in SNR within ceramic regions adjacent to metallic conductors. In this way, previously inaccessible regions within the ceramic structure close to the metallic conductors are made accessible. The paper further discusses methodological requirements, limitations, and potential extensions of the presented multienergy SXCT merging technique. T2 - iCT 2026 CY - Linz, Austria DA - 10.02.2026 KW - Synchrotron x-ray CT KW - Multi-energy CT KW - Low-Temperature cofired ceramics PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655848 SP - 1 EP - 7 CY - e-Journal of Nondestructive Testing AN - OPUS4-65584 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa A1 - Madia, Mauro A1 - Kanna, Naveen A1 - Bär, Jürgen ED - Ricoeur, Andreas T1 - Anwendung der zyklischen R-Kurven-Analyse zur Abschätzung des Kitagawa-Takahashi-Diagramms N2 - Die ausgeprägte Langzeitfestigkeit eines Werkstoffes entspricht der maximalen Spannung, unterhalb derer alle ursprünglich wachstumsfähigen Mikrorisse arretieren. Für fehlerbehaftete Werkstoffe stellt das Kitagawa-Takahashi (KT)-Diagramm die Abhängigkeit der ausgeprägten Langzeitfestigkeit von der Defektgröße dar. Das KT-Diagramm kann mit großem Aufwand experimentell bestimmt oder durch verschiedene Modelle abgeschätzt werden. Solche Ansätze ergeben oft nichtkonservative Prognosen und berücksichtigen weder den Aufbau der Rissschließeffekte noch lokale Spannungen. In dieser Arbeit wird ein Kurzrissmodell auf Grundlage der zyklischen R-Kurve und des Rissarrestphänomens zur Abschätzung des KT-Diagramms vorgestellt. Die Abschätzungen werden mit experimentellen Daten validiert, die mit gekerbten Proben nach dem Treppenstufenverfahren ermittelt wurden. T2 - 57. Tagung des DVM-Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Köln, Germany DA - 18.02.2025 KW - Langzeitfestigkeit KW - KT-Diagramm KW - zyklische R-Kurven-Analyse PY - 2025 DO - https://doi.org/10.48447/BR-2025-512 VL - 257 SP - 93 EP - 104 PB - Deutscher Verband für Materialforschung und -prüfung e.V. CY - Berlin, Deutschland AN - OPUS4-62603 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Geburtig, Anja A1 - Wachtendorf, Volker A1 - Trubiroha, P. T1 - Simulationsdaten zur photooxidativen Beanspruchung an verschiedenen geografischen Freibewitterungs-Standorten N2 - Freibewitterungen weisen grundsätzlich eine hohe Variabilität der jeweiligen Intensität der Beanspruchungsparameter auf; sie sind nicht einfach wiederholbar. Um dennoch die Ergebnisse einer Beanspruchung vergleichen zu können, ist eine aussagekräftige Charakterisierung der Freibewitterung wichtig. Traditionell werden Daten bekannter Einflussgrößen wie Globalstrahlung, Temperatur oder Feuchtewerte herangezogen. Obwohl man weiß, dass diese Größen an den exponierten Oberflächen wechselwirken und kombiniert als Mikroklima Einfluss auf Degradationsprozesse nehmen, werden schon aus Praktikabilitätsgründen diese separat als klimatische Messgrößen angegeben. Die Aussagekraft dieser Daten ist mäßig. Ziel dieses Beitrags ist es, die Aussagekraft und damit Vergleichbarkeit zu erhöhen, indem diese Messdaten als Stundendaten zu Wirkintegralen vorverarbeitet und jahresweise akkumuliert werden. Betrachtet wird dafür der Prozess der Photooxidation, da dieser Alterungs-mechanismus bei allen Kunststoffen auftritt. Für eine einfache Modellierung wird die wirksame UV-Bestrahlung, gewichtet mit einer Arrhenius-abhängigen Ober¬flächen-temperatur (TOF), über den Beanspruchungszeitraum von hier je einem Jahr akkumuliert. Die Idee einer solchen Messgröße für photooxidative Ober¬flächen¬alterung wurde bereits vorgestellt [1]. Dort wurde ein Gerät vor¬geschlagen, mit dem dieser Wert für verschieden absorbierende Oberflächen für die Dauer einer Exposition akkumuliert wird, und ergänzend eine Abschätzung der Betauungs¬zeiten dieser Referenz-Oberflächen erfolgen könnte. Hier soll es um eine rechnerisch generierte Zusammenstellung dieser photo¬oxidativen 1-Jahres-Alterungswerte für verschiedene Standorte gehen. Ein Temperaturfaktor erfasst dabei den Einfluss der Strahlungserwärmung auf eine weiße, graue bzw. schwarze Referenzoberflächen, spiegelt also die Kopplung von solarer Strahlung und Temperatur wider [1]. Ermittelt wird er aus Stunden¬daten der Globalstrahlung und der Lufttemperatur. Die spektrale Wirkung wird aus Sonnenhöhenständen entsprechend der geografischen Breite mit Hilfe der FastRT-Oberfläche [2] als PiT·h-Wert abgeschätzt [3]. Anhand der errechneten Jahreswerte können die Schweregrade der photo¬oxidativen Beanspruchung an den verschiedenen Standorten unmittelbar verglichen werden. Die gezeigten Simulationsdaten für ein solches „elektronisches Referenzmaterial“ für photooxidative Degradation zeigen die prinzipielle Möglichkeit einer Kartografierung solcher Daten auf. T2 - 53. Jahrestagung der GUS CY - Stutensee-Blankenloch, Germany DA - 26.03.2025 KW - Polymer 3R, UV, Bestrahlung, Bewitterung PY - 2025 SN - 978-3-9826129-2-8 VL - 53 SP - 19 EP - 28 PB - Gesellschaft für Umweltsimulation e.V. CY - 76327 Pfinztal (Berghausen) AN - OPUS4-62902 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Paul, Nathalie A1 - Kister, Alexander A1 - Schnellhardt, Thorben A1 - Fetz, Maximilian A1 - Hecker, Dirk A1 - Wirtz, Tim ED - Meo, Rosa ED - Silvestri, Fabrizio T1 - Reinforcement Learning for Segmented Manufacturing N2 - The manufacturing of large components is, in comparison to small components, cost intensive. This is due to the sheer size of the components and the limited scalability in number of produced items. To take advantage of the effects of small component production we segment the large components into smaller parts and schedule the production of these parts on regular-sized machine tools. We propose to apply and adapt recent developments in reinforcement learning in combination with heuristics to efficiently solve the resulting segmentation and assignment problem. In particular, we solve the assignment problem up to a factor of 8 faster and only a few percentages less accurate than a classic solver from operations research. T2 - European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases 2023 CY - Turin, Italy DA - 18.09.2023 KW - Reinforcement Learning KW - Assignment Problem KW - Large component manufacturing PY - 2025 DO - https://doi.org/10.1007/978-3-031-74640-6_38 VL - 1 IS - 1 SP - 470 EP - 485 PB - Springer Cham AN - OPUS4-63031 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Siefke, Lennart A1 - Linden, Anna T1 - Towards a robust automated surface inspection method for CT-scanned cannulas N2 - For certain cardiovascular diseases, cannulas are implanted into the blood circuit. To match the patients individual anatomy of the heart, there is research for cannulas to be custom-designed and manufactured aided by 3D printing. However, cannulas have to hold very high standards with regard to the smoothness of their surfaces, as rough patches can lead to formation of blood clots. Therefore, this work uses computer vision to detect such patches as part of quality assurance. First, the produced cannula is scanned using a precise CT scanner and transformed into a 3D mesh object. Rough patches in an otherwise smooth but curved surface are detected by using cosine similarity between neighboring faces and a statistical evaluation. In the end, this method is able to raise a warning when curved surfaces are not smooth enough and visualizes the problematic patches. However, there is just limited access to test data currently and the scanner used needs to be upgraded. T2 - 3D in Science & Applications (3D-iSA) 2024 CY - Berlin, Germany DA - 26.11.2024 KW - Algorithm KW - Additive manufacturing KW - Surface evaluation PY - 2025 UR - https://www.gfai.de SN - 978-3-942709-34-7 SP - 66 EP - 70 AN - OPUS4-63057 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bulling, Jannis A1 - Gravenkamp, H. A1 - Birk, C. T1 - On the efficient simulation of ultrasonic waves on polygonal meshes N2 - At many stages of technology development in ultrasonic Non-Destructive Testing (NDT) and Structural Health Monitoring (SHM), simulation tools are essential. Many modern approaches to ultrasonic testing, such as Model Assisted Probability of Detection, inverse problems with iterative optimization, or the generation of data for AI training, benefit from highly efficient simulation tools in terms of simulation time. In this talk, we investigate explicit time stepping with the Scaled Boundary Finite Element Method (SBFEM) for approximating the linear elastic wave equation on 2D polygonal meshes, enhanced with a mass lumping technique for faster simulation times. We present the proposed changes to the formulation to successfully use mass lumping. Examples are used to demonstrate that there is no loss of quality due to the approximated mass matrix. Furthermore, mass lumping reduces the simulation time and makes the simulation more efficient. In addition, the proposed simulation method has the advantages of SBFEM meshing techniques. These advantages include fast meshing using an image-based quadtree algorithm or polygonal meshing by transforming triangular meshes based on a CAD model. The latter meshing method can include special crack tip elements that efficiently handle the crack tip singularity. T2 - DAS | DAGA 2025 CY - Copenhagen, Denmark DA - 17.03.2025 KW - Non-Destructive Testing (NDT) KW - Scaled Boundary Finite Element Method (SBFEM) KW - Structural Health Monitoring (SHM) KW - Numerical simulation PY - 2025 UR - https://pub.dega-akustik.de/DAS-DAGA_2025/imprint.html SN - 978-3-939296-23-2 SP - 1592 EP - 1595 AN - OPUS4-63017 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bintz, Thilo A1 - Kruschwitz, Sabine T1 - Non-destructive Testing for the Determination of Durability-Relevant Material Properties of Clinker-Reduced Building Materials N2 - In the quest to combat climate change, the construction industry, heavily reliant on cement-based materials, faces scrutiny due to significant CO2 emissions, mainly from clinker production. To address this, there’s a need to strategically reduce clinker content in cement. However, these new formulations must meet the same requirements as the original ones, so their durability must be investigated. In this study, we determined material parameters that enable an assessment of moisture and ion transport. These methods offer advantages over conventional approaches, including non-destructiveness, reduced measurement time, simplified setup, enhanced resolution, and improvement of detection limits. Our investigation utilizes NDT techniques, using 1H NMR relaxometry for moisture transport and LIBS for ion transport in various clinker-reduced materials. The NMR tomograph provides spatial insights into internal moisture transport, correlated with weight change assessments for the capillary transport coefficient. Additionally, based on NMR relaxometry data the chloride diffusion coefficient is estimated. Chloride migration tests are performed, and results are evaluated using LIBS and indicator tests for the chloride migration coefficient. Our findings highlight NMR relaxometry and LIBS advantages over conventional methods, showcasing superior spatial resolution, non-destructiveness, and, in some cases, expedited results with independence from the formulation of the cement matrix. Thus, these new methods can be used to test the durability of new, more heterogeneous cementbased building. T2 - Rilem Spring Convention 2024 CY - Milano, Italy DA - 10.04.2024 KW - NMR relaxometry KW - LIBS KW - Clinker reduced cement KW - Durability parameters PY - 2025 SN - 978-3-031-70281-5 DO - https://doi.org/10.1007/978-3-031-70281-5_48 VL - 56 SP - 426 EP - 434 AN - OPUS4-61824 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -