TY - CONF A1 - Müller, Ralf T1 - Sintering and Foaming of Silicate Glass Powders N2 - The lecture focuses on the mechanisms of non-desired gas bubble formation and foaming during the sintering of glass powder compacts. It is shown that foaming is driven by carbon gases and that carbonates, encapsulated in micropores or mechaniacally dissolved beneath the glass surface, provide the major foaming source. T2 - Sandanski Workshop Sinter crystallization 27th-29th September 2021 PROJECT “THEORY AND APPLICATIONS OF SINTER-CYSTALLIZATION” DN 19/7 CY - Online meeting DA - 27.10. 2021 KW - Sintering KW - Non-desired foaming PY - 2021 AN - OPUS4-53772 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heuser, Lina T1 - Silver in low-melting alkali zinc borate glasses N2 - Ein aktuelles Forschungsziel ist die Substitution von Bleioxid in niedrig schmelzenden Gläsern z.B. zur Anwendung in Silber-Metallisationspasten. Im Fokus steht hier die Untersuchung der Silberdiffusion in Alkali-Zink-Boratgläsern (X2O-ZnO-B2O3, X = Li, Na, K, Rb). Zudem wird der Redoxzustand des Silbers (Ag) und somit die Art der diffundierenden Silberspezies bestimmt. Hierzu wurde eine metallische Silberschicht mittels Sputterns auf Glaswürfel aufgebracht. Die Wärmebehandlung erfolgte nahe der Glasübergangstemperatur bei 470 °C über 2 h unter Luft und Stickstoffatmosphäre. Die Schichtdicke der Silberbeschichtung betrug 1.8 µm nach der Wärmebehandlung, gemessen mittels Weißlicht-Interferometer. Die Silberdiffusionsprofile wurden mittels Sekundär-Neutral-Teilchen-Massenspektrometrie gemessen. Die Diffusionskoeffizienten des Silbers liegen in der Größenordnung von ~10-14 cm2/s und unterscheiden sich nur gering in Abhängigkeit des Alkali-Ions im Glas. Mittels Fluoreszenz-Spektroskopie ließen sich gelöste Ag+-Ionen und [Agm]n+-Cluster nach der Wärmebehandlung unterscheiden. Zusätzlich konnten ausgeschiedene metallische Silber-Partikel im Natrium-enthaltenden Glas mittels Transmissionselektronenmikroskopie beobachtet werden. Diese haben einen mittleren Durchmesser von ~6 nm. N2 - Substitution of lead oxide in low-melting glasses, e.g., for application in silver metallization pastes, is a current research goal. This work is focused on the investigation of silver diffusion in alkali zinc borate glasses (X2O-ZnO-B2O3, X = Li, Na, K, Rb). In addition, the redox state of silver (Ag) and thus the type of diffusing silver species were studied. For this purpose, a metallic silver coating was applied on glass cubes by means of sputtering. Heat treatment of the samples was performed close to the glass transition temperatures at 470 °C for 2 h under air and nitrogen atmosphere. Coating thickness was 1.8 µm after heat treatment, measured by a white light interferometer. Silver diffusion profiles were measured by means of secondary neutral mass spectrometry. The silver diffusion coefficients are in the range of ~10-14 cm2/s and indicate no significant differences depending on the type of alkali ions in the glass. Dissolved Ag+-ions and [Agm]n+-clusters in the glasses were differentiated using fluorescence spectroscopy. Precipitated metallic silver particles in the sodium containing glass were observed by means of transmission electron microcopy. Their mean particle diameter was ~6 nm. T2 - Living Glass Surfaces XI - Year of Glass CY - Ilmenau, Germany DA - 14.09.2022 KW - Alkali zinc borate glasses KW - Silver diffusion KW - Transmission electron microscopy KW - Fluorescence spectroscopy KW - Silver cluster PY - 2022 AN - OPUS4-55736 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heuser, Lina T1 - Silver diffusion in low-melting alkali zinc borate model glasses studied by means of SNMS, TEM and XAS N2 - In many late-breaking research fields as in photovoltaics, microelectronics, nuclear waste glasses or at least mirror glasses silver diffusion in glasses is relevant to the issues of high-level functionality and recycling. The present study is focused on silver diffusion in innovative, low-melting alkali zinc borate glasses (X2O-ZnO-B2O3, X = Li, Na, K, Rb) potentially usable for silver metallization-pastes in solar cells. The glasses were coated with a thin metallic silver layer and heat treatments in air and nitrogen close to Tg at 470 °C for 2 h were performed. After heat treatment under air and nitrogen atmospheres the coating thickness, measured by a white light interferometer, was about 1.8 µm thick. Silver depth profiles determined by means of secondary neutral mass spectrometry (SNMS) indicate the fastest silver diffusion to a depth of 3.5 µm for Li2O-ZnO-B2O3 (LZB) glass. Nevertheless, the influence of the different alkali ions on the silver diffusion is small. The oxygen availability determines the silver diffusion into the glasses. The oxygen promotes the oxidation of the silver layer enabling Ag+ to diffuse into the glass and to precipitate as Ag0. Both species were detected by x-ray absorption spectroscopy (XAS). The precipitated metallic silver particles in Na2O-ZnO-B2O3 (NZB) glass have a mean size of 5.9 nm ± 1.2 nm diameter, which was determined using transmission electron microscopy (TEM). Phase separation in zinc-rich and zinc-poor phases with a mean diameter of 75 nm ± 20 nm occurred in NZB glass after heat treatment. Ion diffusion of the glasses into the silver layer was suggested by EDX-line scans. T2 - 94. Glastechnische Tagung CY - Online meeting DA - 10.05.2021 KW - Silver diffusion KW - Alkali zinc borate glass KW - Metallic silver precipitates KW - Phase separation PY - 2021 AN - OPUS4-52861 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heuser, Lina T1 - Silver - alkali borate glass pastes N2 - Network modifier ions can decisively influence properties and structure of low melting alkali-zinc-borate glasses and thus cause complex effects on the liquid phase sintering of silver-glass metallization pastes. This effect was studied for X2O-ZnO-B2O3 (X = Li, Na, Rb) glasses for silver-glass metallization pastes. Viscosity and the glass transition temperature, Tg, were measured with rotational viscometry and dilatometry. Dried model pastes with 30 vol% LZB, NZB or RZB glass were prepared for sintering studies by means of heating microscopy measuring the silhouette area shrinkage of uniaxially pressed powder compacts during heating at 5 K/min. For comparison, the silhouette area shrinkage of pure glass and silver powder compacts were determined. Glass-silver wetting was investigated during heating of bulk glass cylinders placed on silver substrates. Glass RZB turned out to have the lowest viscosity among the glasses under study. Its glass transformation temperature, Tg, was found at 444 °C and it caused the lowest sintering onset for its glass and paste powder compacts. Slightly increased values of Tg were found for NZB and LZB (468 °C and 466 °C, respectively) and a slightly retarded sintering was found for both paste powder compacts. These results indicate that liquid phase sintering of silver-glass pastes under air atmosphere is mainly influenced by glass viscosity. T2 - GLASS MEETING 2020 CY - Online meeting DA - 07.12.2020 KW - Silver-glass metallization paste KW - Sintering KW - Alkali ions KW - Viscosity KW - Silver precipitates PY - 2020 AN - OPUS4-52871 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Short fatigue crack propagation in L-PBF 316L stainless steel N2 - Fracture mechanics is a key to fatigue assessment in AM metal components. Short fatigue cracks are initiated at defects and pronounced surface roughness intrinsic to AM. The subsequent crack-propagation is strongly influenced by microstructural interactions and the build-up of crack-closure. The aim of the present study is to give an insight into short-crack propagation in AM-metals. Fatigue crack propagation resistance curves were determined experimentally for AISI 316L manufactured by Laser Powder Bed Fusion (L-PBF) which was heat treated at three different temperatures. Differences in the build-up of the fatigue-crack propagation threshold in between the L-PBF specimens and compared to wrought material are due to the residual stress states, a pronounced roughness of the crack-faces in the L-PBF specimens and phase transformation in the vicinity of the crack-tip, resulting in increased crack-closure. This, together with crack-branching found along the crack path, enhances the resistance to the propagation of fatigue cracks. T2 - ASTM International Conference on Additive Manufacturing 2020 CY - Online meeting DA - 16.11.2020 KW - Additive Manufacturing KW - Cyclic R-Curve KW - Component assessment KW - L-PBF KW - 316L KW - Residual Stress KW - Fatigue Crack Growth PY - 2020 AN - OPUS4-51585 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana T1 - Separation of the impact of residual stress and microstructure on the fatigue performance of LPBF Ti-6Al-4V at elevated temperature (Keynote) N2 - Ti-6Al-4V alloy is intensively used in the aerospace industry because of its high specific strength. However, the application of Laser Powder Bed Fusion (LPBF) Ti-6Al-4V alloy for structurally critical load-bearing components is limited. One of the main limiting factors affecting the structural integrity, are manufacturing defects. Additionally, the high cooling rates associated with LPBF process result in the formation of large residual stress (RS) with complex fields. Such RS can cause cracking and geometrical distortions of the part even right after production. Also, the microstructure of LPBF Ti-6Al-4V in the as-built condition is significantly different from that of the conventionally produced alloy. All these factors affect the mechanical behavior of the material. Therefore, to improve the material performance it is important to evaluate the individual effect of RS, defects, and microstructure on fatigue life. To this aim Ti-6Al-4V LPBF material in as-built condition and subjected to different post-processing, including two heat treatments (for stress relief and microstructural modification) and Hot Isostatic Pressing (HIP, for densification), were investigated. Prior to fatigue tests at elevated temperature, the microstructure, the mesostructure, and subsurface RS on the fatigue samples were investigated. It was found that the fatigue performance of HIPped samples is similar to that of conventionally produced Ti-6Al-4V. The tensile RS found at the surface of as-built samples decreased the fatigue life compared to heat-treated samples. Additionally, the modification of the microstructure (by heat treatment) did not affect the fatigue performance in the regime of mostly elastic strain. This shows that in the absence of tensile RS the manufacturing defects solely control the failure of LPBF components and densification has the strongest effect on the improvement of the mechanical performance. T2 - EUROMAT 2021 CY - Online meeting DA - 12.09.2021 KW - Additive manufacturing KW - Ti-6Al-4V KW - Residual stress KW - Fatigue performance PY - 2021 AN - OPUS4-53278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schilling, Markus T1 - Semantic Technologies in Action: Integrating Mechanical and Microstructure Data in MSE N2 - Semantic technologies (ST) are a powerful tool for storing, processing, and querying data in a contextualized and interoperable manner. They enable machine-actionable and human-readable knowledge representations essential for advanced data management, retrieval, and reuse. As one of the key factors within the frame of the collaborative project platform MaterialDigital (PMD), the establishment of a virtual material data space and the semantic modeling of hierarchical, process-dependent material data is aimed at to serve as best-practice examples of knowledge representation through ontologies and knowledge graphs. In this presentation, the application of ST to a specific use case from the field of materials sciences and engineering (MSE) is demonstrated: the integration and analysis of data related to a 2000 series age-hardenable aluminum alloy. By semantically representing mechanical and microstructural data obtained from tensile tests and dark-field transmission electron microscopy across various aging times, an expandable knowledge graph was constructed that is aligned with the PMD Core Ontology (PMDco) and enriched through the Tensile Test (TTO) and Precipitate Geometry Ontologies. This semantically integrated dataset enables advanced analytical capabilities via SPARQL queries and reveals microstructure–property relationships consistent with the well-known Orowan mechanism. The approach highlights the potential of semantic data integration to support FAIR data principles and to foster a more data-centric and interoperable research infrastructure in MSE. T2 - MSE Research Data Forum 2025 CY - Siegburg, Germany DA - 08.07.2025 KW - Semantic Data KW - Data Integration KW - Digitalization KW - Data Interoperability PY - 2025 AN - OPUS4-63666 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schilling, Markus T1 - Semantic Technologies for Digital Transformation in Materials Science: From PMDco to Prototypical Applications N2 - The digital transformation of Materials Science and Engineering (MSE) is accelerating the adoption of structured, interoperable, and FAIR data practices, in particular with respect to an advanced research data management. Semantic technologies play a pivotal role in this transformation, as the enable the integration, contextualization, and automation of diverse data sources across experimental, computational, and simulation domains. Central to these efforts is the Platform MaterialDigital Core Ontology (PMDco), now in version 3.0, which provides a robust mid-level semantic framework tailored for MSE. PMDco bridges abstract high-level ontologies, such as the Basic Formal Ontology (BFO) standardized in ISO/IEC 21838-2, with domain-specific terminologies to ensure consistency and interoperability across applications. This presentation explores the application of PMDco and its integration into workflows within the Platform MaterialDigital (PMD) initiative. Through its deployment in electronic laboratory notebooks (ELNs), PMDco enables semantic representation of experimental data, such as tensile test results compliant with ISO 6892-1:2019-11, transforming them into machine-actionable knowledge graphs. Prototypical implementations demonstrate how semantic technologies enhance laboratory processes, improve data reuse, and streamline documentation which offers opportunities for automation and education. Further extending its versatility, PMDco serves as a linking point for semantically representing simulation data, enabling comprehensive integration of experimental and computational datasets. This creates structured data spaces that support advanced digital workflows. Beyond PMDco, the presentation highlights the design of graph patterns and semantic shapes, showcasing generalizable methods for managing diverse data in MSE being based on data structuring and formatting. By presenting best practices in ontology development, data acquisition, and knowledge graph generation, this talk underscores the transformative potential of semantic technologies in MSE. It offers a forward-looking perspective on the role of structured data spaces as a driver for innovation, ensuring that materials science continues to advance through rigorous, interoperable, and automated digital methodologies. T2 - FEMS Euromat 2025 CY - Granada, Spanien DA - 14.09.2025 KW - Semantic Data KW - Data Integration KW - Digitalization KW - Data Interoperability KW - PMD Core Ontology KW - Graph Patterns PY - 2025 AN - OPUS4-64165 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schilling, Markus T1 - Seamless Science: Navigating Daily Lab Life through Semantic Data Integration, Electronic Lab Notebooks, and Knowledge Graphs in the Era of MSE Digitalization N2 - The field of materials science and engineering (MSE) is currently experiencing a significant paradigm shift towards enhanced digitalization which imposes a huge challenge on researchers, scientists, engineers, and technicians. In this respect, the quality assurance of processes and output data as well as the interoperability between applications following FAIR principles are to be ensured. For storage, processing, and querying of data in contextualized form, Semantic Web technologies (SWT) are used as they allow for machine-actionable and human-readable knowledge representations needed for data management, retrieval, and (re)use. The collaborative project ‘platform MaterialDigital’ (PMD) aims to solve digitalization tasks and implement digital solutions in the field of MSE in a prototypical manner. Therefore, the establishment of a virtual material data space and the systematization of the handling of hierarchical, process-dependent material data are focused. In this respect, selected MSE methods are semantically represented which are supposed to serve as best practice examples with respect to knowledge representation and the creation of knowledge graphs used for material data. Accordingly, this presentation shows the efforts taken within PMD to store data in accordance with a testing standard compliant semantic representation of a tensile test of metals at room temperature (ISO 6892-1:2019-11). A semantic link of the corresponding tensile test ontology (TTO) and data leads to enhanced data useability and interoperability. The PMD core ontology (PMDco), developed in PMD and used as mid-level ontology in TTO, is also presented briefly. Moreover, as a best practice example, the acquisition of tensile test data with subsequent generation of knowledge graph data by semantic interconnection using TTO was realized by applying an electronic laboratory notebook (ELN). Corresponding tensile tests were performed by undergraduate MSE students at the Technical University of Darmstadt. The resulting data pipeline, also illustrated in the presentation, enabled a fully-fledged digitally integrated experimental procedure, the approach of which may be transferred to other test series and experiments. In addition to facilitating the acquisition, analysis, processing, and (re)usability of data, this also raises the awareness of students with respect to data structuring and semantic technologies in terms of education and training. T2 - Materials Science and Engineering Congress 2024 CY - Darmstadt, Germany DA - 24.09.2024 KW - FAIR KW - Plattform Material Digital KW - Digitalization KW - Data Interoperability KW - Electronic Lab Notebook KW - Education PY - 2024 AN - OPUS4-61138 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bettge, Dirk A1 - Klinger, Christian T1 - Schadensanalyse an Fahrradkomponenten - Fraktographie, Ursachen, Prävention N2 - Komponenten von Fahrrädern werden im Betrieb vorwiegend schwingend beansprucht. Typische Werkstoffe sind Stahl, Aluminiumlegierungen, Messing, CFK und thermoplastische Kunststoffe. Da es sich, unabhängig von der Preiskategorie, um konstruktiven Leichtbau handelt, werden einige Bauteile betriebsfest mehr oder weniger weit oberhalb der Dauerfestigkeit ausgelegt. Die im normalen Betrieb auftretenden Schäden sind daher weit überwiegend Schwingbrüche. Andere Schadensmechanismen wie z.B. Korrosion spielen quantitativ eine untergeordnete Rolle. Schwingbrüche treten nach einer Periode unbemerkten Risswachstums oft ohne Vorwarnung und ohne makroskopische Verformung auf. Im Falle von sicherheitsrelevanten Komponenten wie Rahmen, Gabeln, Lenkern, Sattelstützen, Kurbelarmen oder Pedalen kann dies zu erheblichen Personenschäden führen, die den Wert des ursächlichen Bauteilschadens weit überschreiten. Über einen langjährigen Zeitraum wurden gebrochene Komponenten aus dem Alltag und aus Gerichtsverfahren analysiert. Das Hauptaugenmerk lag hierbei auf der fraktographischen Analyse, teilweise wurden die zu Grunde liegenden Schadensursachen ermittelt. Einflussfaktoren sind beispielsweise konstruktive Kerben an ungünstigen Stellen, aber auch Werkstoffwahl und Fertigungsqualität spielen eine Rolle. In den meisten Fällen wurde jedoch die konstruktive Lebensdauer überschritten. Diese wird praktisch nie mitgeteilt, und eine wiederkehrende Prüfung sicherheitsrelevanter Bauteile findet nicht statt. Im Sinne der Vermeidung von Schäden und Unfällen könnte darauf hingewirkt werden, für sicherheitsrelevante Komponenten Lebensdauern besser abzuschätzen und von der Laufleistung abhängige Sichtprüfungen zu empfehlen. T2 - DGM Tagung Werkstoffprüfung CY - Dresden, Germany DA - 26.10.2022 KW - Fraktographie KW - Fahrrad KW - Lebensdauer KW - Öffentliche Sicherheit KW - Schadensanalyse KW - Schadensprävention PY - 2022 AN - OPUS4-56122 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Trappe, Volker T1 - Scarf-joint repairs under fatigue loading investigated for sandwich shell applications N2 - Wind turbine rotor blades are produced as aerodynamic, three-dimensionally formed sandwich shell structures using mainly glass fiber reinforced plastics (GFRP). The GFRP used today have the potential to withstand the harsh operating conditions of rotor blades over the projected service life of 20 years. Premature damages that occur can be traced primarily back to design and/or manufacturing imperfections, as well as unusually high load scenarios (for instance lightning strikes, or strong winds combined with system control errors). Therefore, rotor blades have to be repaired several times (on average 2-3 times) during their projected service life. Approximately 70% of these are repairs of small- to medium-sized sandwich shells, carried out by technicians directly accessing the blade by suspended roping at the wind turbine location. The goal is to execute repairs that will last over the remaining service life, i.e. be sustainable. Within the framework of a research project carried out at BAM, Division 5.3 Polymer Matrix Composites, Department 5 for Materials Engineering, not only was the geometric shape (round vs. square in relation to the top view) varied, but also the layup of the scarf repair structure, variables that have not been studied systematically to-date. Sub-component scale sandwich shell specimens with representative repairs were used in this work in addition to coupon-scale specimens that are more commonly seen in literature. These sub-component shell specimens were tested using a unique shell test bench under loading conditions representative of wind turbine blade shell operating conditions with respect to fatigue strength. Using non-destructive testing methods (field strain measurement and thermography), damage development and distribution was monitored and analyzed in-situ. As a result, a concept was developed in which the repaired areas showed at least equivalent if not higher fatigue strength than the reference shells that were not repaired. T2 - ICFC9 - The 9th International Conference on the Fatigue of Composites CY - Vicenza, Italy DA - 21.06.2023 KW - Repair of sandwich shell structures KW - Non-destructive testing KW - Wind turbine blades PY - 2023 AN - OPUS4-57929 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kuchenbecker, Petra T1 - Sample Preparation of Nano-Powders for Particle Size Determination N2 - The use of increasingly finer starting powders up to nanopowders can also be observed in the field of ceramics. Their advantages consist, for example, in their lower activation energy, an increase in strength or unique optical properties. However, handling and characterization of the powders are much more difficult. The main reason for this is the very high adhesive forces between the particles and between particles and other surfaces, too. Therefore, submicron and even more so nanoparticles tend to agglomerate and their separation into primary particles during sample preparation prior to particle sizing is of particular challenge. A representative measurement sample is only obtained when it no longer contains agglomerates. The evaluation of the dispersion process and a decision on whether it was successful thus increases in importance for the reliability of the measurement results of particle sizing. The presentation uses examples to show possible approaches and provides information on possible sources of error. It is shown that successful granulometric characterisation of fine powders requires both an improved dispersion technique and very often an effective combination of two or more measurement methods. T2 - 96. Jahrestagung der Deutschen Keramischen Gesellschaft CY - Online Meeting DA - 19.04.2021 KW - Agglomerates KW - Nano-powder KW - Dispersion process PY - 2021 AN - OPUS4-52503 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Trappe, Volker T1 - Roving-Alterung und mechanische Eigenschaften N2 - Im statistischen Mittel steht eine Windkraftanlage (WKA) in Deutschland alle 6 Jahre wegen eines Schadens an den Rotorblättern und verursacht Kosten von 20k€-40k€ infolge Ertragsausfall und Reparaturkosten. Bei über 30.000 WKA in Deutschland verursacht dies jährlichen Kosten von 100-200 Mio. €. Zu 70% sind die Ursachen Fertigungsfehler. Diesem Themenkomplex widmet sich FB-5.3 in Kooperation mit FBs der Zerstörungsfreien Prüfung (Abt. 8) schon seit Jahren. Im aktuellen Projekt geht es um einen vorzeitigen Verschleiß der Rotorblätter infolge der Verwendung gealterter Glasfaser-Rovings. (GF). Die Entwicklung moderner Windkraftanlagen hatte in Europa seinen Ursprung in den 90er Jahren. OEMs und GF-Hersteller waren dicht beisammen. Die Globalisierung des Marktes führt heute zu einer weltweiten Verschiffung der GF in feucht-warmen Containern. Je nach Beschaffenheit (Chemie) der Schlichten (Oberflächenbehandlung) von GF können diese stark altern (Hydrolyse-Effekte) und die Festigkeit kann im Bauteil um bis zu 50% abgemindert sein. In einer Kooperation mit der Rotorblattallianz, einem Zusammenschluss der OEMs, Halbzeugherstellern und Forschungsinstituten, wurden schon vor 5 Jahren in einem Forschungsprojekt (FB-5.3; VH 5538) die chemischen Mechanismen der Alterung exemplarisch für eine Glasfaser-Roving-Type aufgeklärt. Im aktuellen Projekt (FB-5.3; VH 5304) wird ein beschleunigtes Alterungsverfahren (erhöhte Temperatur und Feuchte) am Roving im un-impregnierten Zustand entwickelt und die Festigkeit nachfolgend nach Einbettung in eine Epoxid-Harz-Matrix bestimmt. Je nach Alterungszustand zeigt sich eine Abnahme der Zwischenfaserbruchfestigkeit von bis zu 50%. Nicht alle Glasfaser-Roving-Typen zeigen diesen Effekt. Es ist gelungen für OEMs und Halbzeughersteller ein handhabbares Verfahren zur innerbetrieblichen Qualitätssicherung zu entwickeln, da die wenigsten Firmen über komplexe Analyseverfahren, wie an der BAM, verfügen. T2 - Composite United - AG Faserverbund in der Windenergie CY - Braunschweig, Germany DA - 09.05.2023 KW - Faserkunststoffverbunde KW - Windenergie KW - Alterung PY - 2023 AN - OPUS4-58409 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bhadeliya, Ashok T1 - Rissfortschrittsuntersuchungen an gefügten Nickelbasiswerkstoffen bei hoher Temperatur N2 - Nickelbasierte Superlegierungen werden in großem Umfang für Gasturbinenschaufeln verwendet, da sie einer Kombination aus hoher Belastung und hohen Temperaturen widerstehen können. Um die Effizienz moderner Gasturbinen zu verbessern, werden hohe Betriebstemperaturen angestrebt. Diese hohen Temperaturen verbunden mit mechanischen Belastungen führen zu Materialschäden aufgrund von Kriechen, Ermüdung und anderen Schadensmechanismen. Aus diesem Grund werden Turbinenschaufeln regelmäßig im Rahmen von Wartungs- und Instandsetzungsmaßnahmen geprüft und falls erforderlich ausgetauscht, um ein katastrophales Versagen im Betrieb zu vermeiden. Ein kompletter Austausch ist mit sehr hohen Kosten verbunden, weshalb geeignete Reparaturverfahren entwickelt wurden und werden. Neue Reparaturtechnologien wie die Additive Fertigung, Lötverfahren und der Einsatz von vorgesinterten Vorformen (Presintered Preform PSP) sollen eine effiziente Reparatur und optimale Eigenschaften der reparierten Bauteile sichterstellen. Im Allgemeinen stellen die Fügezonen typische Schwachstellen dar, da sie die Anrissbildung und Rissausbreitung erleichtern und die Anzahl der Lastzyklen bis zum Bruch reduzieren können. Aus diesem Grund ist eine umfassende Untersuchung des Rissfortschrittsverhaltens in diesen, durch neue Reparaturtechnologien entstandenen Bereichen erforderlich, um die Restlebensdauer der Turbinenschaufeln vorherzusagen. Als ein erster Beitrag zu dieser Fragestellung werden Ergebnisse von Rissfortschrittsversuchen (Fig. 1) an SENT-Proben vorgestellt, die durch Engspaltlöten gefügt wurden. Die Versuche wurden bei einer Temperatur von 950 °C und einem Spannungsverhältnis R = 0,1 durchgeführt. Die Erfassung des Rissfortschritts erfolgte mit dem Gleichstrom-Potentialsonden-Verfahren. Mit der Finite-Element-Methode konnte der Spannungsintensitätsfaktor für gefügte SENT-Proben berechnet werden, der dann zur Berechnung der Risswachstumskurven verwendet wurde. Eine abschließende licht- und rasterelektronenmikroskopische Untersuchung der Bruchflächen soll einen Beitrag zum Verständnis der Bruchmechanismen liefern und klären, ob der Riss sich im Lotwerkstoff, im Grundwerkstoff oder in der Grenzfläche ausbreitet. Die Ergebnisse werden zur Kalibrierung des Rissfortschrittsmodells und der Auslegung zukünftiger Komponenten verwendet. T2 - Werkstoffprüfung Tagung 2022 CY - Dresden, Germany DA - 27.10.2022 KW - Rissfortschritts KW - Gelötete Nickel-Basis-Legierungen PY - 2022 AN - OPUS4-60894 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kupsch, Andreas T1 - Rissentwicklung in CFK-Laminaten nachgewiesen durch in situ Röntgen-Refraktion N2 - In Leichtbauanwendungen sind Materialien mit geringen Dichten und hohen Festigkeiten gefragt. Insbesondere Faser-Kunststoff-Verbunde (FKV) erfüllen diese Anforderungen und werden zunehmend für Strukturbauteile eingesetzt. Die Oberflächen moderner Rotorblätter von Windkraftanlagen werden aus FKV gefertigt. Das Versagen dieser Materialien hat massiven Einfluss auf die Einsatzfähigkeit der gesamten Windkraftanlage. Daher ist die Kenntnis des Versagensverhaltens dieser Komponenten unter statischer und zyklischer Belastung von großem Interesse, um die Betriebsbeanspruchung abzuschätzen. Im Idealfall wird die Schadensentwicklung unter Betriebslast mit zerstörungsfreien in-situ-Prüfverfahren ermittelt. Hier berichten wir über die Beobachtung der Rissentwicklung in Carbon-Faserverstärkten Kunststoffen (CFK) unter kontinuierlicher Zugbelastung durch in-situ Synchrotron-Röntgenrefraktionsradiographie. Eine selbst entwickelte elektromechanische Zugprüfmaschine mit einem Kraftbereich bis zu 15 kN wurde in den Strahlengang an der BAMline (BESSY II) integriert. Da in herkömmlichen (Absorptions-) Radiographien Defekte wie Zwischenfaserbrüche oder Faser-Matrix-Enthaftung keinen ausreichenden Kontrast verursachen, wird zur Kontrastanhebung die Röntgenrefraktion benutzt. Hier wird das sogenannte Diffraction Enhanced Imaging (DEI) angewandt, um Primär- und gebrochene Strahlung mit Hilfe eines Analysatorkristalls zu trennen. Diese Technik ermöglicht schnelle Messungen mit einem Gesichtsfeld von einigen Quadratmillimetern (hier: 14 mm × 7.2 mm) und ist ideal für in-situ Untersuchungen. Die Bildgebung und der Zugversuch erfolgen mit einer Bildfrequenz von 0.7 / s und einer Dehnrate von 0.00055 / s . Bei 0°/90° Fasergelegen treten die ersten Zwischenfaserrisse bei 380 MPa (Dehnung 0.8 %) auf. Vor dem Versagen bei ca. 760 MPa (Dehnung 2.0 %) beobachten wir die Ausbildung eines nahezu äquidistanten Rissmusters (Risse in ca. 1 mm Abstand), das sich im geschädigten Zustand über die gesamte Probe erstreckt. T2 - DACH-Jahrestagung 2023 CY - Friedrichshafen, Germany DA - 15.05.2023 KW - Röntgen-Refraktion KW - Synchrotronstrahlung KW - CFK KW - Rissentwicklung PY - 2023 AN - OPUS4-57622 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo T1 - Revealing the Nature of Melt Pool Boundaries in Additively Manufactured Stainless Steel by Nano-sized Modulation N2 - Additive manufacturing (AM) of metallic alloys has gained momentum in the past decade for industrial applications. The microstructures of AM metallic alloys are complex and hierarchical from the macroscopic to the nanometer scale. When using laser-based powder bed fusion (L-PBF) process, two main microstructural features emerge at the nanoscale: the melt pool boundaries (MPB) and the solidification cellular substructure. Here, details of the MPB are revealed to clearly show the three-dimensional nature of MPBs with changes of cell growth of direction and their relation to their surrounding cellular substructure, as investigated by transmission electron microscopy (TEM) for L-PBF 316L austenitic stainless steel (cf. Figure 1). A hitherto unknown modulated substructure with a period of 21 nm is further discovered within cells as the result of a partial Ga+-focused ion beam-induced ferritic transformation of the austenite. Cell cores and cell boundaries differ notably regarding the modulated substructure. T2 - 3. Fachtagung Werkstoffe und Additive Fertigung 2022 CY - Dresden, Germany DA - 11.05.2022 KW - Additive manufacturing KW - Austenitic steel 316L KW - Melt pool boundary KW - Microstructural characterization KW - Transmission electron microscopy PY - 2022 AN - OPUS4-54836 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ghafafian, Carineh T1 - Restoring lightweight strength - Effect of localized repairs on the mechanical properties of composites sandwich structures N2 - As a type of high-performance composite material, glass-fiber reinforced plastics (GFRP) are favored for the construction of wind turbine rotor blades due to their high specific strength and stiffness properties (Grasse et al, 2010). During the blade manufacturing process, however, imperfections are often introduced, then further propagated due to harsh environmental conditions and a variety of loads (Caminero et al, 2013; Trappe et al, 2018). This leads to failure significantly before their designed lifespan. Since replacement of entire blades can be a costly potential outcome, localized repairs of the damaged region to restore structural integrity and thus lengthen its lifespan can executed in the field by technicians accessing the blades directly by suspended roping. These methods involve replacing the lost load path with a new material that is joined to the parent structure. In recent years, considerable studies have been conducted to investigate the influence of different repair parameters on the stress distribution, ultimate strength, impact behavior, and residual stresses of bonded repaired structures [Caminero et al, 2013; Trappe et al, 2018; Shufeng et al, 2014; Harman and Rider, 2011; Ahn and Springer, 2000; Lekou and Vionis, 2002). However, there currently do not exist any standardized repair procedures for wind turbine rotor blades. Namely, there is a lack of understanding about the effects of the layup of various repair methods, especially on the damage mechanism and fatigue life of the shells of rotor blades (Caminero et al, 2013; Trappe et al, 2018). This work therefore aims to begin to enrich this knowledge gap by testing the influence of different variables among repair patches on the mechanical properties of sandwich composite structures. Manufactured with the vacuum-assisted resin infusion (VARI) process, the test specimens are produced as a GFRP structure to represent the outer shell portion of a wind turbine blade, then repaired with a scarf joint. Scarf repairs are favored as the most efficient of the common structural joints, as the removal of the damaged area with angled walls leads to a nearly uniform shear stress distribution along the bond surface and no eccentricity in the load distribution (Caminero et al, 2013; Lekou and Vionis, 2002; Siener, 1992). The performance of specific layup methods of repair patches, namely a large-to-small versus small-to-large scheme of repair layers, is studied with static and load-controlled fatigue testing, then compared to pristine test specimens as well as to each other in terms of mechanical property restoration. The transition layer between repair and parent material is especially of interest in the performance of the structure. Damage onset, crack development and eventual failure are monitored in-situ with non-destructive testing methods, including thermography with an infrared camera system and a 3D deformation analysis system, to develop a more robust understanding of the effects of these repair concept variables on wind turbine blade shell structures. T2 - Wind Energy Science Conference CY - Online Meeting DA - 25.05.2021 KW - Glass fiber reinforced polymers KW - Wind turbine blade shell structures KW - Scarf joint repair PY - 2021 AN - OPUS4-52687 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Manzoni, Anna Maria T1 - Reliable welding of high-entropy alloys N2 - The importance of high-entropy alloy (HEAs) in the field of materials research is increasing continuously and numerous studies have been published, recently. These are mainly focused on manufacturing of different alloy systems having excellent structural properties from low to high temperatures. Therefore, HEAs are of high potential for many applications in very demanding conditions. However, this is so far limited by poor knowledge and experience regarding economic and reliable component manufacturing. The processability of HEAs has hardly been investigated so far, indicated by the small number of publications worldwide: welding <30 and machining <5. Hence, this contribution provides an overview about the current state of the art on processing of HEAs. Fundamental principles are shown for safe weld joints while ensuring high component integrity. For safe welding, the combined consideration of complex interactions of material, construction and process is necessary. Recent studies on different HEAs showed the influence of heat input by means of different welding processes on the microstructure and respective properties. Based on intensive literature survey and on our initial study, the main research objectives of processing HEAs are presented. T2 - ICHEM 2020 - Third International Conference on High Entropy Materials CY - Berlin, Germany DA - 27.09.2020 KW - High Entropy Alloy KW - Welding KW - Welding processing influences PY - 2020 AN - OPUS4-51591 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nguyen, Ngoc Tam Thi T1 - Reinventing Piping for Hydrogen Applications – A Composite Approach N2 - A key step towards achieving climate neutrality in the European Union (EU) by 2050 is the transition to renewable energy sources. Green hydrogen plays a central role in this shift but remains costly, particularly through the utilization of PEM electrolysis. Currently, around 50% of the costs associated with electrolyser systems are attributed to system peripherals, underscoring the potential for cost savings through standardization and the use of cost-effective materials [Tja17, IRE20]. In the collaborative project "PolyH2Pipe", the Institute of Plastics Processing in Industry and Craft (IKV), the Welding and Joining Institute (ISF) and BAM Division 5.3 are developing media-carrying pipe systems made of continuous fiber-reinforced thermoplastics (TP-FR) for hydrogen applications. The project aims to design these pipes, develop suitable joining techniques and validate the requirements for these piping systems. This research initiative serves as a foundational basis for the subsequent market introduction of large-scale TP-FR pipe systems for electrolysers and fuel cell systems. Initial test results will be presented as a part of the talk during the colloquium. T2 - H2Safety Colloquium - Materials compatibility and properties CY - Online meeting DA - 14.05.2025 KW - Hydrogen KW - Polymer Matrix Composites KW - Electrolyser KW - Piping PY - 2025 AN - OPUS4-63134 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bresch, Sophie T1 - Reaction sintering and sintering additives for cost-effective production of thermoelectric oxides N2 - Thermoelectric oxides attract much interest recently. Although their thermoelectric properties are inferior to non-oxides, they exhibit distinct advantages. Thermoelectric oxides are stable in air at higher temperatures, their raw materials are less toxic, and more abundant. To enhance attractivity of these materials for industrial applications, production costs need to be reduced. Conventionally, the legs of thermoelectric generators are sintered from green bodies of previously synthesized powder. Reaction-sintering is a fabrication method without a powder synthesis step, as the final phase is formed during the sintering from a raw material mixture. Moreover, the reduction of chemical potential during reaction-sintering is effective as an additional driving force for sintering. We show that reaction-sintering increases the densification of CaMnO3 (n-type, Sm doped). Consequently, the electrical conductivities improved by about 100 % leading to superior power factors (PF = 230 µW/mK² for CaMnO3). Another approach to reduce the production costs is to lower the sintering temperature by adding sinter additives. The addition of 4 wt% CuO to CaMnO3 lowers the sinter temperature from 1250 °C to 1050 °C. The achieved power factor PF = 264 µW/mK is more than two times higher as reported in literature for the same dopant. T2 - Virtual Conference on Thermoelectrics (VCT) CY - Online meeting DA - 21.07.2020 KW - Thermoelectrics KW - Reaction sintering KW - Sintering additives KW - Calcium manganate KW - Calcium cobaltite PY - 2020 AN - OPUS4-51070 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -