TY - CONF A1 - Hübner, Martin T1 - Verbesserung der Ermüdungsfestigkeit von Längssteifen durch Low Transformation Temperature (LTT) Schweißzusätze N2 - In diesem Beitrag wird die gezielte Applikation zusätzlicher LTT-Schweißraupen zur Erhöhung der Ermüdungsfestigkeit in Schweißverbindungen erläutert. Der Einfluss der Eigenspannungen auf die Ermüdungsfestigkeit kann besonders durch Längssteifen verdeutlicht werden, da diese durch Verzugsbehinderungen oftmals hohe Eigenspannungen in der ermüdungskritischen Wärmeeinflusszone (WEZ) aufweisen. Daher wurden konventionell einlagig geschweißte Längssteifen aus hochfestem Baustahl mit LTT-Zusatzlagen an den Stirnseiten versehen, um lokal Druckeigenspannungen zu erzeugen, welche durch Schweißparametervariationen geometrisch variierten. Zusätzlich wurde als Kontrolle auch der Fall der zweilagig konventionell geschweißten Längssteife betrachtet. Die mittels XRD bestimmten Schweißeigenspannungen konnten in der WEZ durch die zusätzliche LTT-Naht reduziert werden. Je weiter weg die Nahtspitze der Zusatzlage ist, umso geringer sind die Schweißeigenspannungen in der WEZ. Bei konstanter Amplitudenlast und einem R-Verhältnis von 0,1 konnte die Ermüdungsfestigkeit der LTT-Proben deutlich verbessert werden. Die Ermüdungsfestigkeit bei 2 Millionen Lastwechsel beträgt für konventionelle Proben 87 MPa und für die LTT-Proben 156 bis 196 MPa. Auch eine Steigung der Zeitfestigkeitsgeraden konnte an den LTT-Proben beobachtet werden. Der Umfang dieser Steigerung war ähnlich bzw. höher als bei höherfrequenten gehämmerten Proben. Ein Zusammenhang zwischen der bestimmten Eigenspannung und der Ermüdungsfestigkeit konnte beobachtet werden, wenn auch nur im geringeren Umfang. LTT-Schweißzusätze können verwendet werden, um die Ermüdungsfestigkeit in Längssteifen zu erhöhen. T2 - 15. Vollversammlung des SFB 1120: Summer School 2025 CY - Kall, Germany DA - 08.07.2025 KW - Low transformation temperature (LTT) KW - Eigenspannungen KW - Ermüdungsfestigkeit KW - Längssteife PY - 2025 AN - OPUS4-63710 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Karapanagiotis, Christos A1 - Schukar, Marcus A1 - Breithaupt, Mathias A1 - Hicke, Konstantin T1 - Toward a Digital Twin of Hydrogen Pressure Vessels Enabled by Distributed Fiber Optic Sensors N2 - We present a digital replica of a hydrogen pressure vessel enabled by distributed fiber optic sensors (DFOS). This digital replica dynamically displays and updates the vessel’s structural condition by calculating strain residuals defined as the difference between the measured DFOS strain and the expected strain based on pressure data. As an example, we show the ability of the DFOS to detect and localize damage caused by drilling six holes into the vessel’s body. This digital replica represents a foundational step toward a fully integrated digital twin for predictive maintenance and remaining lifetime prognosis. T2 - Sensor and Measurement Science International (SMSI) 2025 CY - Nuremberg, Germany DA - 06.05.2025 KW - fiber optic sensors KW - digital twin KW - structural health monitoring KW - hydrogen KW - machine learning PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-633885 UR - https://www.ama-science.org/proceedings/details/5962 SN - 978-3-910600-06-5 DO - https://doi.org/10.5162/SMSI2025/C6.1 SP - 165 EP - 166 PB - AMA Service GmbH CY - Wunstorf AN - OPUS4-63388 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin T1 - Einfluss der Low Transformation Temperature-Schweißzusätze auf die Ermüdungsfestigkeit von Längssteifen N2 - In dem vorliegenden Beitrag wird die gezielte Applikation zusätzlicher LTT-Schweißlagen zur Einbringung von Druckeigenspannungen in ermüdungskritischen Bereichen an Schweißverbindungen untersucht. Ziel ist die Entwicklung eines wirtschaftlichen Verfahrens zur Erhöhung der Ermüdungslebensdauer, ohne die strukturelle Integrität einer Schweißnaht zu beeinträchtigen. Zu diesem Zweck wurden zunächst Längssteifen aus hochfestem Stahl in der ersten Lage mittels Metall-Lichtbogenschweißen unter Verwendung eines konventionellen Schweißzusatzwerkstoffs geschweißt. Anschließend erfolgte die Auftragung eines Chrom-Nickel-legierten LTT-Schweißzusatzwerkstoffs an die Stirnseiten der Längssteifen. T2 - OVGU BMDK Seminar CY - Magdeburg, Germany DA - 17.06.2025 KW - Low transformation temperature (LTT) Schweißzusätze KW - Schweißeigenspannungen KW - Ermüdungsfestigkeit PY - 2025 AN - OPUS4-63702 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin T1 - Bericht zum Fortschritt des laufenden Projekts: "Hybrider Einsatz von LTT-Schweißzusätzen zur Schwingfestigkeitsverbesserung hochfester Stahlbauteile" N2 - Dieses Dokument fasst den Projektfortschritt des BAM-Projektes "Hybrider Einsatz von LTT-Schweißzusätzen zur Schwingfestigkeitsverbesserung hochfester Stahlbauteile" im Rahmen des Sitzung des DVS Fachausschuss FA09 - Konstruktion und Festigkeit für die Projektquartale Q4 2024 und Q1 2025 zusammen und stellt die wichtigsten Ergebnisse in Kurzform vor. T2 - Sitzung des DVS Fachausschuss FA09 - Konstruktion und Festigkeit CY - Berlin, Germany DA - 21.05.2025 KW - Low transformation temperature (LTT) KW - Eigenspannungen KW - Ermüdungsfestigkeit KW - Makroproben PY - 2025 AN - OPUS4-63699 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin T1 - Enhancement of the Fatigue Strength by Application of a Low Transformation Temperature Welding Consumable N2 - To improve the fatigue strength of weld seams, a project is being carried out at BAM using Low Transformation Temperature (LTT) welding consumables to reduce residual stress at weld seams. Longitudinal stiffeners, which were welded conventionally in the first layer and additionally with an LTT or conventional layer on the end faces, were tested for fatigue strength. The mean fatigue strength at 2 million load cycles was increased from 87 MPa to at least 156 MPa. A comparison of HFMI-treated samples with conventional filler metal showed an increase in fatigue strength of 146 MPa. This means that LTT filler metals achieve a similar increase in fatigue strength as conventional post-treatment methods. T2 - The 78th IIW annual assembly and international conference on welding and joining CY - Genua, Italy DA - 22.07.2025 KW - Low transformation temperature (LTT) KW - Fatigue strength KW - Weld geometry PY - 2025 AN - OPUS4-63704 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gleim, Tobias T1 - AI-Based Documentation Analysis for Safety Assessment of Packages for Radioactive Material N2 - The transportation of radioactive material requires, dependent on type und quantity of the radioactive material, a regulatory approval based on the type of the package. Safety assessments shall be conducted in compliance with the IAEA regulations and documented in a comprehensive package design safety report to obtain approval from authority. This comprehensive safety report evaluates a broad range of requirements from the regulations, including mechanical, thermal, shielding, criticality and transport requirements and controls, and testing assessments. Additionally, it encompasses supporting documents such as specifications, inspections, certifications, drawings, and guidelines in a variety of complex documents. Safety and manufacturing reports contain multiple interconnected sub-reports covering various topics. Changes, such as component modifications, material property updates, or regulatory revisions, often impact multiple sections of the safety analysis reports, making even minor adjustments complex and time-consuming. Each transport package has unique requirements, making every safety report distinct, despite following the same regulatory framework. Most documentation exists in standard digital formats but is often not machine interpretable. This lack of interpretability means individuals must manually identify and address dependencies within the reports. An AI-based documentation system that visualizes these dependencies would significantly enhance the efficiency of safety assessments. By linking interpretable content directly to datasheets, tables, simulations, experimental results, standards, and regulations, such a system would automatically identify changes and interdependencies. Related conditions could be validated using AI-based tools, reducing the need for manual intervention, improving both efficiency and safety. Human error plays a significant role in drafting, reviewing, and revising safety reports, often requiring iterative review cycles and multiple reviewers before approval. A digital quality infrastructure could reduce iterations and further improve efficiency. Integrating AI into this process could optimize safety assessments and enhance their robustness by leveraging interpretability to enhance safety. This preliminary study explores the readiness and requirements for using LLMs and RAG in the context of regulatory compliance for transport of radioactive material. By analyzing current documentation workflows, we identify how LLM-based tools can interpret complex safety reports and highlight critical interdependencies. We stress the importance of robust data governance, confidentiality measures, and AI reliability in this highly regulated context. T2 - BAM – Fraunhofer Materials LLM Days CY - Würzburg, Germany DA - 03.07.2025 KW - KI KW - RAG KW - LLM PY - 2025 AN - OPUS4-63727 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Karapanagiotis, Christos A1 - Breithaupt, Mathias A1 - Duffner, Eric A1 - Schukar, Marcus T1 - Real-time monitoring of hydrogen composite pressure vessels using surface-applied distributed fiber optic sensors N2 - In this paper, we report to the best of our knowledge for the first time on continuous real-time monitoring of composite overwrapped pressure vessels (COPVs) designed for hydrogen storage using surface-applied distributed fiber optic sensors (DFOS). We conducted continuous and real-time DFOS measurements during pressure cycling tests consisting of periodic pressure fluctuations between 20 bar and 875 bar, with a rate of 5 cycles min−1. During pressure cycling, the DFOS system measured strain changes, that under normal operating conditions were linearly correlated to changes in pressure. To detect and quantify damage-related anomalies, we trained a simple regression model to predict strain from pressure data and used the difference between predicted and measured values as a damage indicator. With our approach, the DFOS system not only detected and localized the damage but also continuously tracked its evolution in real time under dynamic pressure conditions. Furthermore, unlike previous studies where optical fibers were embedded within the composite structure, we applied them on the COPV surface, reducing both implementation cost and time while eliminating the need to modify the COPV manufacturing process. Based on our results, we are confident that DFOS can enhance safety and facilitate the transition from time-consuming periodic inspections to more efficient, machine learning-based predictive maintenance. KW - Fiber optic sensors KW - Hydrogen KW - Structural health monitoring KW - Pressure vessels KW - Predictive maintenance PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-627644 DO - https://doi.org/10.1088/2515-7647/adb9ac SN - 2515-7647 VL - 7 IS - 2 SP - 2 EP - 10 PB - IOP Publishing Ltd CY - Bristol, UK AN - OPUS4-62764 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Czeskleba, Denis T1 - Experimental determination of hydrogen diffusion in high-strength submerged arc welded joints by electrochemical permeation N2 - High-strength structural steels are increasingly used in modern steel construction for economic and design reasons, e.g., in building, plant or mobile crane construction. By using steels with higher yield strengths (≥690 MPa), significant weight reductions and lower processing costs can be achieved by reducing the wall thickness. For example, substituting S235J2 with S960QL can reduce weight by up to 78%. Current efforts in lightweight design result from the goal of reducing greenhouse gas emissions by up to 65% by 2030 compared to 1990. These demands mean a significant reduction in process emissions in industry by increasing the efficiency of energy and raw materials. Submerged arc welding (SAW) offers high deposition rates and the welding of sheet thicknesses of up to 200 mm. Due to their special microstructure to achieve strength, high strength steels have reduced ductility and are susceptible to hydrogen-assisted cold cracking (HACC), which can also form with delay. In addition, large plate thicknesses lead to high residual welding stresses and long diffusion paths for hydrogen introduced via the welding process, for example. Furthermore, H-diffusion coefficients for submerged arc multi-layer weld metal are very limited as a basis for estimating the time interval of a possible delayed cold cracking (thus HACC) or for post-heating procedures for hydrogen reduction (no HACC). Reliable H-diffusion coefficients are therefore an adequate tool for assessing the risk of delayed HACC. This study characterizes the hydrogen diffusion behavior in submerged arc multi-pass weld metal, heat-affected zone and base metal of a two different S690 steels (TM and QT condition). Samples were extracted from the weld metal, heat-affected zone and base material to investigate the microstructure-specific influence on the diffusion of hydrogen. Using electrochemical permeation at room temperature and carrier gas hot extraction in the temperature range up to 400 °C, the corresponding diffusion coefficients were determined. From the experimental data, hydrogen diffusion coefficients and absorbed hydrogen concentrations had been calculated. In contrast e.g. to GMA welds, the hydrogen diffusion coefficients did not exhibit significant differences in the two base materials (TM and QT) or the heat-affected zone or weld metal, although quite different welding heat inputs were investigated. From the practical viewpoint, thick-walled SAW joints can be assessed for delayed hydrogen diffusion only by the base material coefficients. The calculated diffusion coefficients will be further used for numerical modelling of the hydrogen diffusion in welded joints. T2 - IIW Intermediate Meeting 2025 CY - Trollhätten, Sweden DA - 10.03.2025 KW - Hydrogen Cracking KW - Submerged Arc Welding KW - Hydrogen Diffusion KW - Cold Cracking PY - 2025 AN - OPUS4-63124 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Assessment of in-service welding conditions for pressurized hydrogen pipelines via component test N2 - Hydrogen is the energy carrier of tomorrow for a fossil-free future. This requires a reliable transport infrastructure capable of transporting large quantities of hydrogen. In addition to the construction of new pipelines, the conversion of existing natural gas (NG) networks is an essential part of global hydrogen strategies. The transport of hydrogen is fundamentally different from that of NG, as hydrogen can be absorbed into the pipeline material. Given the known effects of hydrogen embrittlement, the compatibility of the materials for the proposed pipelines (typically low alloy steels in a wide range of strengths and thicknesses) must be investigated. However, pipelines require frequent maintenance, repair, or the need to install additional outlets. In some cases, it is necessary to perform welding on or to the pipelines while they are in-service, i.e. with active gas flow under high pressure. This in-service welding poses challenges for hydrogen operations in terms of additional hydrogen absorption during welding and material compatibility. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, which can lead to sufficient hydrogen absorption, and the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility of the respective materials compared to room temperature. In this context, knowledge about welding on hydrogen pipelines is scarce due to the lack of operational experience. Fundamental experimental investigations are required to investigate the transferability from natural gas to hydrogen pipeline networks. For this reason, the present study presents a specially designed demonstrator concept for the realistic assessment of the welding process conditions. The demonstrator was designed ex-post sample extraction for quantification of the absorbed hydrogen concentration. For safety reasons, the required volume of pressurized hydrogen was limited by inserting a solid cylinder. Welding experiments on the DN50 and DN200 pressurized demonstrators showed an increased hydrogen uptake in the welded area of several ppm. T2 - Materials Week/Steel Innovation CY - Frankfurt am Main, Germany DA - 02.04.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding KW - Component test PY - 2025 AN - OPUS4-62941 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heimann, Jan A1 - Mustapha, Samir A1 - Yilmaz, Bengisu A1 - Prager, Jens T1 - Guided Waves in Composite Overwrapped Pressure Vessels and Considerations for Sensor Placement Toward Structural Health Monitoring—An Experimental Study N2 - The utilization of composite overwrapped pressure vessels (COPVs) to store hydrogen, especially at high pressures, is gaining more popularity due to their lightweight design and high storage density, offering significant economic advantages. However, the presence of material defects or fatigue can lead to critical failures, requiring an innovative and robust approach to ensure safe operation and system integrity. Developing a continuous structural health monitoring (SHM) system for COPVs can provide comprehensive realtime information about their condition, facilitating a shift away from periodic inspections. This study scrutinizes the behavior of guided waves (GWs) within COPVs to design a sensor ,network for damage detection and localization. First, the dispersive and multimodal propagation behavior of GWs is experimentally investigated. Subsequently, important parameters for the network design are derived and finally a sensor network consisting of 15 piezoelectric transducers is designed to cover the entire cylindrical area. The effectiveness is then evaluated experimentally by placing artificial defects on the surface of the COPV. The multi-layered dataset of GW signals was analyzed using both commonly used ultrasonic features (e.g., amplitude, frequency, time of flight) as well as statistical features (kurtosis, skewness, variance, etc.). These features were utilized to compute a damage index, and the effectiveness of the detection performance was assessed using receiver operating characteristic curves. It can be seen that some features are more sensitive and robust under varying experimental conditions. The results show that ultrasonic GW SHM system is a promising solution for damage detection and localization in COPVs. KW - Composite Overwrapped Pressure Vessels KW - Guided Waves KW - Structural Health Monitoring KW - Sensors Placement KW - Damage Detection KW - Damage Localization KW - Elastic Wave KW - Testing Methodologies KW - Ultrasonics PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625239 DO - https://doi.org/10.1115/1.4067667 SN - 2572-3898 VL - 8 IS - 3 SP - 031007-1 EP - 031007-13 PB - The American Society of Mechanical Engineers (ASME) CY - New York, USA AN - OPUS4-62523 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wille, Frank T1 - KI-Einsatz im gefahrgutrechtlichen Kontext N2 - Der Vortrag behandelt den Einsatz von Künstlicher Intelligenz im gefahrgutrechtlichen Kontext und beleuchtet deren Potenzial zur Effizienzsteigerung in ressourcenlimitierten Umgebungen. Anwendungsfelder an der BAM umfassen die Datenanalyse zur Verpackungssicherheit, die Automatisierung von Zulassungs- und Genehmigungsprozessen, die Unterstützung bei der Mitarbeit an Normen und Regelwerken sowie die Bearbeitung komplexer Forschungsfragen. Herausgestellt wird die wachsende Datenmenge und Komplexität in der Gremienarbeit (z. B. UN-Regelwerke), die manuelle Auswertung ineffizient macht. KI-gestützte Methoden wie LLM, RAG und Knowledge Graphs sollen digitale Qualitätsinfrastrukturen unterstützen, die Dokumenten- und Datenanalyse beschleunigen, ohne die menschliche Verantwortung für Sicherheitsbewertungen zu ersetzen. Zentrale Herausforderungen sind die Black-Box-Natur von KI, mögliche Halluzinationen, sowie die Sicherstellung von Reliabilität und Compliance. Ein innovativer Ansatz wird für die wiederkehrende Prüfung von Gasdruckspeichern vorgestellt: Durch die Kombination zerstörungsfreier Prüfungen mit ML-gestützter Datenanalyse können Sicherheitsreserven ausgewiesen und Kosten deutlich reduziert werden. T2 - 20. Gefahrgut-Technik-Tage CY - Berlin, Germany DA - 13.11.2025 KW - Artificial Intelligence KW - RAG KW - LLM PY - 2025 AN - OPUS4-64864 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nagelschmidt, Sven A1 - Herbrich, Uwe A1 - Keller, Christian A1 - Qiao, Linan T1 - Re-evaluation of tensile and creep rupture data of metals using a modified Larson–Miller approach N2 - More than 70 years ago, in 1952 Larson and Miller adapted an existing relationship whichevaluates the relative effects of time and temperature on creep rupture behavior of various alloys by using existing data and by constructing so-called master curves. Since that time, the formulated Larson–Miller relation, commonly known as Larson–Miller parameter, is a widely used time–temperature parameter for various applications, e.g. for rupture life, creep and relaxation analyses of metals and some other materials such as polymers, concrete and ceramics.Nevertheless, the physical meaning of this parameter as well as the determination of master curves are still the subject of major criticism. In this work, both aspects are reviewed and analyzed with data originally considered in thepaper of Larson and Miller based on the following approach: (a) the parameter was modifiedregarding a reference time and a reference temperature according to the time–temperature superposition principle; (b) master curves were generated for five materials investigated originally by Larson and Miller, based on a stretched exponential function type. It has been shown, that: (1) With normalized time and temperature, the Larson–Miller parameter corresponds to real logarithmic rupture time. (2) For the relationship between Creep rupture stress and the modified Larson–Miller parameter, the stretched exponential function is a good choice as a master function. (3) Corresponding model parameters have physical meaning and can be easily determined based on data from creep test data. The investigations provide a better understanding and applicability of Larson–Miller approach. KW - Larson–Miller parameter KW - Creep rupture time KW - Time–temperature equivalence KW - Stretched exponential function KW - Extrapolation of short-term data PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-644486 DO - https://doi.org/10.1016/j.engfracmech.2025.111582 SN - 0013-7944 VL - 329 SP - 1 EP - 16 PB - Elsevier Ltd. AN - OPUS4-64448 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Popiela, Bartosz T1 - Better with age? Discussion of creep phenomena during initial loading of type 4 composite pressure vessels N2 - To maintain the highest safety standards for compressed gas storage in composite pressure vessels, a deeper understanding of their ageing mechanism is required. In the present study, the impact of an initial loading under increased temperature and sustained pressure on the safety of type 4 composite pressure vessels is investigated. Two designs of type 4 cylinders were manufactured, the only difference being the internal pressure function used during the filament winding process. Hence, their residual stress state and the quality of the composite layers varied. Ten pressure vessels were initially loaded under sustained pressure and increased temperature, and later subjected to slow burst tests. Comparing the results with cylinders tested in a pristine state underlines a significant improvement in the performance of initially loaded cylinders of one of the designs. This phenomenon was caused by a significant decrease of the scattering of burst pressures within a sample. At the same time, a slight decrease of the burst pressures could be observed. An explanation of this behavior could be supported by strain measurements with fiber optic sensors, which were embedded in the composite material. The strains measured during the initial loading indicate a stress redistribution, which has an impact on the strength of the pressure vessel. Moreover, an increased stiffness during the slow burst tests after initial loading was observed that indicates a better exploitation of the individual layers of the composite structure. The study supports previous observations on the increased performance after initial loading and provides new insights into the strain development in creep effects in type 4 pressure vessels. T2 - AZL Aachen Composite Pipes & Vessels Workgroup Meeting CY - Aachen, Germany DA - 11.11.2025 KW - Composite KW - Pressure vessel KW - Filament winding KW - Creep PY - 2025 AN - OPUS4-64667 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lozano-Martín, Daniel A1 - Tuma, Dirk A1 - Chamorro, César R. T1 - Evaluation of Reference Equations of State for Density Prediction in Regasified LNG Mixtures Using High-Precision Experimental Data N2 - This study evaluates the performance of three reference equations of state (EoS), AGA8-DC92, GERG-2008, and SGERG-88, in predicting the density of regasified liquefied natural gas (RLNG) mixtures. A synthetic nine-component RLNG mixture was gravimetrically prepared. High-precision density measurements were obtained using a single-sinker magnetic suspension densimeter over a temperature range of (250 to 350) K and pressures up to 20 MPa. The experimental data were compared with EoS predictions to evaluate their accuracy. AGA8-DC92 and GERG-2008 showed excellent agreement with the experimental data, with deviations within their stated uncertainty. In contrast, SGERG-88 exhibited significantly larger deviations for this RLNG mixture, particularly at low temperatures of (250 to 260) K, where discrepancies reached up to 3 %. Even at 300 K, deviations larger than 0.4 % were observed at high pressures, within the model’s uncertainty, but notably higher than those of the other two EoSs. The analysis was extended to three conventional 11-component natural gas mixtures (labeled G420 NG, G431 NG, and G432 NG), previously studied by our group using the same methodology. While SGERG-88 showed reduced accuracy for the RLNG mixture, it performed reasonably well for these three mixtures, despite two of them have a very similar composition to the RLNG. This discrepancy is attributed to the lower CO2 and N2 content typical in RLNG mixtures, demonstrating the sensitivity of EoS performance to minor differences in composition. These findings highlight the importance of selecting appropriate EoS models for accurate density prediction in RLNG applications. KW - Regasified LNG KW - Equation of state KW - Density KW - Gravimetric preparation PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-646506 DO - https://doi.org/10.1007/s10765-025-03669-4 SN - 0195-928X VL - 46 SP - 1 EP - 25 PB - Springer Science and Business Media LLC CY - Heidelberg AN - OPUS4-64650 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stamm, Michael T1 - The KI-VISIR Reference Dataset: A Compilation of Thermal and Visual Inspection Data for Quantifying Leading Edge Rain Erosion N2 - This presentation introduces thermography (thermal imaging) as a key method for non-destructive testing (NDT) of wind turbine rotor blades. By leveraging solar heating and aerodynamic effects, passive thermography detects internal defects, delaminations, and surface issues like leading edge erosion. We discuss field measurements, the role of AI/Machine Learning (LATODA) for automated defect classification, and its importance for improving O&M efficiency and lifetime extension in the wind energy sector. T2 - WindEurope Annual Event 2025 CY - Copenhagen, Denmark DA - 08.04.2025 KW - Thermography KW - Wind Turbine Blades KW - AI KW - NDT KW - KI-VISIR PY - 2025 AN - OPUS4-64721 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krenek, S. A1 - Eisermann, R. A1 - Failleau, G. A1 - Lu, Xin A1 - Thomas, P. A1 - Kjeldsen, H. A1 - Anhalt, K. T1 - Fibre-optic thermometry to support the clean energy transition N2 - The measurement and control of temperature plays a key role in achieving the European Green Deal targets for a low carbon energy system. Fibre-optic thermometry is an emerging technology that can improve temperature measurement in extreme environments for energy providers and industry due to its distributed sensing and immunity to electromagnetic fields. Various applications for optimisation and monitoring in the energy sector are described, covering the whole range from energy generation to transmission and consumption. However, fibre-optic thermometers have cross sensitivities to other quantities (e.g., strain and humidity) and ageing effects that need to be investigated, quantified and minimised to obtain traceable and reliable measurements. This is particularly important so that applications in critical infrastructure can benefit from future measurements that are not possible with conventional sensors. The European INFOTherm project aims to overcome the limitations that currently prevent the widespread use of fibre-optic thermometry by creating a dedicated European metrology infrastructure for research, development and calibration. First results on measurement uncertainty, improvement of measurement techniques and practical field tests are presented. KW - Industrial processes optimisation KW - Fibre-optic thermometry KW - Distributed temperature sensing KW - Traceability KW - Thermal energy storage KW - Electrical grid resilience PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-640075 DO - https://doi.org/10.1515/teme-2025-0044 SN - 2196-7113 VL - 92 IS - 9-10 SP - 392 EP - 405 PB - De Gruyter Brill AN - OPUS4-64007 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scharf-Wildenhain, R. A1 - Engelking, Lorenz A1 - Hälsig, A. A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas A1 - Hensel, J. T1 - Effect of heat control on mechanical properties and residual stresses at the transition zone of component and substrate in hybrid DED‑arc manufacturing N2 - In hybrid additive manufacturing, components or semi-finished products manufactured by conventional primary forming are enhanced or modified by additive manufactured structures. However, systematic investigations focusing on the critical transition area between the specific properties of the substrate (like high-strength) and the additively manufactured component, made of specific filler material, are still lacking. The focus of the present study was to determine the influence of heat control on the Δt8/5 cooling time, the distortion, the mechanical properties, and the residual stresses in the transition area of hybrid-additive components. This contributed to the knowledge regarding the safe avoidance of cold cracking, excessive distortion, a reduction in yield stress, and the implementation of hybrid DED-arc manufacturing. The heat control was varied by means of heat input and working temperature such that the Δt8/5 cooling times corresponded to the recommended processing range. The heat input has a greater influence on the cooling time in the transition area than the working temperature. Working temperature and the total energy applied per layer have a significant effect on component distortion. The lowest working temperature of 100 °C in combination with the highest total energy per layer leads to significantly greater distortion compared to manufacturing with a high working temperature of 300 °C and low total energy per layer. In addition, the longitudinal residual compressive stresses in the sensitive transition area are reduced from − 500 MPa to approx. − 200 MPa by adjusting the working temperature from 100 to 300 °C. Such complex interactions must be clarified comprehensively to provide users with easily applicable processing recommendations and standard specifications for an economical hybrid additive manufacturing of components made, for example, of high-strength steels in the transition area. T2 - IIW Annual Assembly and International Conference CY - Rhodes Island, Greece DA - 07.07.2024 KW - Hybrid additive manufacturing KW - DED-arc KW - Heat control KW - High-strength metals KW - Residual stress PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-630415 DO - https://doi.org/10.1007/s40194-025-02036-z SN - 1878-6669 SP - 1 EP - 15 PB - Springer AN - OPUS4-63041 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Masoud Nia, Niloufar A1 - Nietzke, Jonathen A1 - Kannengiesser, Thomas T1 - Ti and Nb microalloying of HSLA steels and its effect on hydrogen diffusion and trapping N2 - Fine-grain, high-strength, low-alloy (HSLA) structural steels with yield strengths > 600 MPa are now the state of the art in construction applications such as mobile cranes and civil engineering. HSLA grades derive their strength from a combination of specific heat treatment and the underlying chemical composition. In this context, Ti or Nb are essential to obtain a fine-grained microstructure as well as the necessary carbides or nitrides for precipitation strengthening. In this context, the specific effect of Ti or Nb-rich compounds on hydrogen trapping and diffusion is well known for special laboratory cast alloys, but unknown for realistic steel compositions. For this reason, a series of S690Q-based alloys were synthesized, close to a real steel composition, but with well controlled Ti or Nb additions in different amounts. Specimens were obtained from these alloys by electrochemical discharge machining (EDM). The specimens were tested using the well-established electrochemical permeation technique. From the experimental results, the hydrogen diffusion coefficients and the analytical subsurface hydrogen concentration were calculated. In addition, the hydrogen trapping behavior at elevated temperatures was interpreted by thermal desorption analysis (TDA) using different heating rates of hydrogen charged samples. The results showed that in contrast to metallurgically "pure" laboratory cast alloys, realistic chemical compositions were similar in their hydrogen trapping behavior, despite some small differences. All investigated steel grades exhibited shallow and reversible hydrogen trapping, regardless of their chemical composition. Of course, the experiments only allowed the calculation of effective diffusion coefficients and trapping energies, which represent an average of the entire microstructure. Nevertheless, HSLA steels are typically joined by arc welding, which includes the risk of delayed hydrogen assisted cracking. From the point of view of welding practice, however, a more or less identical hydrogen diffusion behavior means that no special "metallurgically specific", justifiable measures need to be considered, despite the well-established processes such as "soaking" or dehydrogenation heat treatment. T2 - MPAC 2025 CY - Stuttgart, Germany DA - 06.10.2025 KW - HACC KW - Hydrogen KW - HSLA PY - 2025 AN - OPUS4-64337 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin A1 - Schroepfer, Dirk A1 - Kromm, Arne A1 - Kannengiesser, Thomas T1 - Stress-Optimised Welding Repair for High-Strength Offshore Steel Joints N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future. To achieve these high outputs, turbines far from the coast are required, featuring large subsea jacket structures (30 m up to 50 m) and tall towers (up to 200 m). High-strength steels with a yield strengths up to 500 MPa and wall thicknesses of up to 120 mm are increasingly being used for these structures. During manufacture, weld defects detected by non-destructive testing (NDT) require localized repair (gouging and rewelding). To date, there is a lack of repair concepts and information in standards and guidelines. Therefore, BAM initiated the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal. This research aims to develop a stress-optimized repair concept for thick plate joints, using controlled high-performance GMAW processes and optimized, narrow gouging grooves. Thermal and mechanical gouging are performed, allowing the groove configuration to be modified. Modern welding processes provide deep root penetration and focused energy input capable of welding narrow seams. The aimed residual stress reduction can be attributed to the lower input of weld metal due to the changes in groove configuration and to the reduction in heat input per layer due to the controlled arc process. The experimental analyses take into account the interaction of process, material, and design-related influences on the formation of weld induced stresses. Concluding with recommendations for guidelines elaborated for steel-processing SMEs. T2 - MPA Stuttgart 2025 CY - Stuttgart, Germany DA - 06.10.2025 KW - Repair welding KW - Residual stress KW - High-strength steels KW - Gouging KW - Modern welding processes PY - 2025 AN - OPUS4-64347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tschirschwitz, Rico T1 - Stromspeicher in der Hausanwendung - Auswirkungen im Versagensfall N2 - Im Vortrag wird zunächst eine kurze Einleitung zum Aufbau der Batteriespeicher, Ursachen des thermischen Durchgehens sowie den Auswirkungen anhand bisheriger Versuchsdaten gegeben. Schwerpunkt im Folgenden sind Versuche zu den Auswirkungen beim Versagen von einzelnen Modulen. Darüber hinaus werden weitere Versuche zur Propagation mit mehreren Modulen sowie PoC hinsichtlich der brandschutztechnischen Abtrennung zwischen den einzelnen Modulen vorgestellt. T2 - Forum Schadenverhütung 2025 CY - Berlin, Germany DA - 14.10.2025 KW - Auswirkungsbetrachtungen KW - Thermisches Durchgehen KW - Stationäre Energiespeicher KW - Lithium-Ionen-Batterie KW - Elektrische Energiespeicher PY - 2025 AN - OPUS4-64363 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -