TY - JOUR A1 - Griesche, Axel A1 - Pfretzschner, B. A1 - Taparli, Ugur Alp A1 - Kardjilov, N. T1 - Time-Resolved Neutron Bragg-Edge Imaging: A Case Study by Observing Martensitic Phase Formation in Low Temperature Transformation (LTT) Steel during GTAW N2 - Polychromatic and wavelength-selective neutron transmission radiography were applied during bead-on-plate welding on 5 mm thick sheets on the face side of martensitic low transformation temperature (LTT) steel plates using gas tungsten arc welding (GTAW). The in situ visualization of austenitization upon welding and subsequent α’-martensite formation during cooling could be achieved with a temporal resolution of 2 s for monochromatic imaging using a single neutron wavelength and of 0.5 s for polychromatic imaging using the full spectrum of the beam (white beam). The spatial resolution achieved in the experiments was approximately 200 µm. The transmitted monochromatic neutron beam intensity at a wavelength of λ = 0.395 nm was significantly reduced during cooling below the martensitic start temperature Ms since the emerging martensitic phase has a ~10% higher attenuation coefficient than the austenitic phase. Neutron imaging was significantly influenced by coherent neutron scattering caused by the thermal motion of the crystal lattice (Debye–Waller factor), resulting in a reduction in the neutron transmission by approx. 15% for monochromatic and by approx. 4% for polychromatic imaging. KW - Austenite-to-martensite transformation KW - Neutron radiography KW - Bragg-edge imaging KW - Gas tungsten arc welding (GTAW) KW - Debye–Waller factor KW - Low transformation temperature (LTT) steel PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538016 DO - https://doi.org/10.3390/app112210886 VL - 11 IS - 22 SP - 10886 PB - MDPI CY - Basel AN - OPUS4-53801 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kempf, A. T1 - Correlation between quasistatic und fatigue properties of additively manufactured AlSi10Mg using Laser Powder Bed Fusion N2 - In order to find a resource efficient approach for the fatigue lifetime prediction of laser powder bed fusion (L-PBF) processed AlSi10Mg material, results of tensile and fatigue tests were compared. The specimens were manufactured with three different L-PBF machines and studied in different heat treatment conditions (as-built, annealed, T6 heat treated). The investigations showed that the high attainable tensile strength properties after the manufacturing process are not beneficial in the high cycle fatigue (HCF) regime. In contrast, the applied heat treatments, which lead typically to a decrease of ultimate tensile strength, improved dramatically the fatigue behavior. Additionally, a clear correlation between the elongation at fracture and HCF resistance has been found for individual heat treatment conditions. This empiric relationship provides an estimation of the fatigue resistance in the presence of material defects and can be implemented in part and process approvals. T2 - Fatigue Design 2021 CY - Online meeting DA - 17.11.2021 KW - Additive Manufacturing KW - Laser powder bed fusion KW - AlSi10Mg KW - Tensile properties KW - Fatigue properties PY - 2021 AN - OPUS4-53792 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Short fatigue crack propagation in additively manufactured stainless steel 316L 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 - In-situ Monitoring and Microstructure Development in Additive Manufactured Alloys CY - Online meeting DA - 19.04.2021 KW - AM KW - Cyclic R-Curve KW - Fatigue Crack Propagation PY - 2021 AN - OPUS4-52587 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thomas, Maximilian T1 - Digitalisierung in der Heißrissprüfung - Wie viel Information steckt in einer MVT-Probe? N2 - Die im MVT-Test standardmäßig erfasste Gesamtrisslänge erlaubt keine direkten Rückschlüsse auf die Heißrissanfälligkeit des untersuchten Werkstoffs. Der vorliegende Beitrag erläutert, inwiefern aus der Morphologie von Oberflächenrissen an MVT-Proben dennoch auf das Werkstoffverhalten geschlossen werden kann. T2 - Jährl. Sitzung des DIN/DVS Normenausschuss 092-00-05 GA CY - Online meeting DA - 10.03.2021 KW - MVT KW - Varestraint KW - Heißriss KW - Erstarrungsriss PY - 2021 AN - OPUS4-52243 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Comparison of the fatigue behavior of wrought and additively manufactured AISI 316L N2 - Additively Manufactured (AM) parts are still far from being used in safety-relevant applications, mainly due to a lack of understanding of the feedstock-process-propertiesperformance relationship. This work aims at providing a characterization of the fatigue behavior of the additively manufactured AISI 316L austenitic stainless steel and a direct comparison with the fatigue performance of the wrought steel. A set of specimens has been produced by laser powder bed fusion (L-PBF) and a second set of specimens has been machined out of hot-rolled plates. The L-PBF material shows a higher fatigue limit and better finite life performance compared to the wrought material, accompanied by an extensive amount of cyclic softening. T2 - Fatigue Design 2021 CY - Online meeting DA - 17.11.2021 KW - Additive Manufacturing KW - AM KW - 316L KW - Fatigue KW - High Cycle Fatigue KW - Low Cycle Fatigue PY - 2021 AN - OPUS4-53780 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kempf, Andreas A1 - Kruse, Julius A1 - Madia, Mauro A1 - Hilgenberg, Kai T1 - Correlation between quasistatic und fatigue properties of additively manufactured AlSi10Mg using Laser Powder Bed Fusion N2 - In order to find a resource efficient approach for the fatigue lifetime prediction of laser powder bed fusion (L-PBF) processed AlSi10Mg material, results of tensile and fatigue tests were compared. The specimens were manufactured with three different L-PBF machines and studied in different heat treatment conditions (as-built, annealed, T6 heat treated). The investigations showed that the high attainable tensile strength properties after the manufacturing process are not beneficial in the high cycle fatigue (HCF) regime. In contrast, the applied heat treatments, which lead typically to a decrease of ultimate tensile strength, improved dramatically the fatigue behavior. Additionally, a clear correlation between the elongation at fracture and HCF resistance has been found for individual heat treatment conditions. This empiric relationship provides an estimation of the fatigue resistance in the presence of material defects and can be implemented in part and process approvals. T2 - FATIGUE DESIGN 2021 CY - Online meeting DA - 17.11.2021 KW - Additive Manufacturing KW - Laser powder bed fusion KW - AlSi10Mg KW - Tensile properties KW - Fatigue properties PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-544921 DO - https://doi.org/10.1016/j.prostr.2022.03.009 SN - 2452-3216 VL - 38 SP - 77 EP - 83 PB - Elsevier B.V. AN - OPUS4-54492 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Werner, Tiago A1 - Madia, Mauro A1 - Zerbst, Uwe T1 - Comparison of the fatigue behavior of wrought and additively manufactured AISI 316L N2 - Additive manufacturing (AM) is becoming increasingly important in engineering applications due to the possibility of producing components with a high geometrical complexity allowing for optimized forms with respect to the in-service functionality. Despite the promising potential, AM components are still far from being used in safety-relevant applications, mainly due to a lack of understanding of the feedstock-process-properties-performance relationship. This work aims at providing a full characterization of the fatigue behavior of the additively manufactured AISI 316L austenitic stainless steel and a direct comparison with the fatigue performance of the wrought steel. To this purpose, a set of specimens has been produced by laser powder bed fusion (L-PBF) and subsequently heat treated at 900 °C for 1 hour for complete stress relief, whereas a second set of specimens has been machined out of hot-rolled plates. Low cycle fatigue (LCF) and high cycle fatigue (HCF) tests have been conducted for characterizing the fatigue behavior. The L-PBF material had a higher fatigue limit and better finite life performance compared to wrought material. Both, LCF and HCF-testing revealed an extensive cyclic softening. T2 - FATIGUE DESIGN 2021 CY - Online meeting DA - 17.11.2021 KW - Additive manufacturing KW - L-PBF KW - 316L KW - Fatigue KW - LCF KW - HCF PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-544952 DO - https://doi.org/10.1016/j.prostr.2022.03.056 SN - 2452-3216 VL - 38 SP - 554 EP - 563 PB - Elsevier B.V. AN - OPUS4-54495 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Fracture mechanics fatigue life assessmente based on effective crack propagation data obtained at closure-free conditions N2 - The use of effective crack propagation data, i.e. not affected by the crack closure mechanisms, is proposed as a reliable and robust alternative for the fatigue life assessment of cyclically loaded components. T2 - 43rd Materials Mechanics Seminar CY - Sani, Greece DA - 05.06.2022 KW - Effective crack propagation data KW - Crack-closure KW - Component assessment PY - 2022 AN - OPUS4-55044 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Roveda, Ilaria T1 - Investigation of residual stresses and microstructure effects on the fatigue behaviour of a L-PBF AlSi10Mg alloy N2 - Laser Powder Bed Fusion (L-PBF) allow the fabrication of lightweight near net shape AlSi10Mg components attractive to the aerospace, automotive, biomedical and military industries. During the build-up process, high cooling rates occur. Thus, L-PBF AlSi10Mg alloys exhibit a Si-nanostructure in the as-built condition, which leads to superior mechanical properties compared to conventional cast materials. At the same time, such high thermal gradients generally involve a deleterious residual stress (RS) state that needs to be assessed during the design process, before placing a component in service. To this purpose post-process heat treatments are commonly performed to relieve detrimental RS. In this contribution two low-temperature stress-relief heat treatments (SRHT) are studied and compared with the as-built state: a SRHT at 265°C for 1 hour and a SRHT at 300°C for 2 hours. At these temperatures microstructural changes occur. In the as-built state, Si atoms are supersaturated in the α-aluminium matrix, which is enveloped by a eutectic Si-network. At 265°C the Si precipitation from the matrix to the pre-existing network is triggered. Thereafter, above 295°C the fragmentation and spheroidization of the Si branches takes place, presumably by Al–Si interdiffusion. After 2 hours the original eutectic network is completely replaced by uniformly distributed blocky particles. The effect of the heat and the microstructure modification on the RS state and the fatigue properties is investigated. Energy dispersive x-ray and neutron diffraction are combined to investigate the near-surface and bulk RS state of a L-PBF AlSi10Mg material. Differences in the endurance limit are evaluated experimentally by high cycle fatigue (HCF) tests and cyclic R-curve determination. T2 - 43rd Materials Mechanics Seminar CY - Sani, Chalkidiki, Greece DA - 05.06.2022 KW - AlSi10Mg KW - Fatigue KW - Neutron diffraction KW - X-ray diffraction PY - 2022 AN - OPUS4-55090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhu, Jiangchao A1 - Schurig, M. A1 - Schlums, H. A1 - Madia, Mauro A1 - Zerbst, Uwe T1 - Bruchmechanische Bewertung der Integrität einer Turbinenscheibe bei Überdrehzahl N2 - Turbinenscheiben sind thermisch und mechanisch hochbeanspruchte, sicherheitsrelevante Komponenten in Gasturbinen. Ihre Integrität wird in Bauteiltests unter Überdrehzahlbedingungen nachgewiesen. Kontext des Aufsatzes ist die Erarbeitung einer zusätzlichen Bewertungsebene auf der Grundlage von Versuchen unter monotoner Beanspruchung, die die Beanspruchung im Bauteil realistisch wiedergeben soll. Betrachtet wird ein halbelliptischer Riss, der bei der weiteren Ausbreitung als Umfangsriss wächst (rim peeling). Die Simulation dieser Stelle im Bauteil schließt die mechanische und thermische Beanspruchung sowie sie Dehnungsbehinderung ein. Letztere wird anhand zweier Parameter, der Spannungsmehrachsigkeit ℎ und des (allerdings modifizierten) Constraint-Parameters nach Newman, der die Spannungen über den plastisch verformten Bereich mittelt, bestimmt. Erwartungsgemäß zeigt sich, dass die höchste Dehnungsbehinderung weder an den Oberflächenpunkten, noch an den tiefsten Punkten, sondern an einer Stelle zwischen beiden auf der Rissfront auftritt. Als Versuchsgeometrie für die monotonen Tests soll eine Kreuzprobe mit wanddurchdringenden Rissen ausgehend von einer Innenbohrung dienen. Durch geeignete Wahl der Risstiefe sowie der in beiden Richtungen angreifenden Kräfte gelingt es, bauteiladäquate Zustände zu erzeugen. T2 - 54. Tagung des DVM-Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Online meeting DA - 22.02.2022 KW - Bruchmechanik KW - Struktur Integrität KW - Turbinenscheibe KW - Constraint PY - 2022 SP - 13 EP - 22 AN - OPUS4-54403 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhu, Jiangchao T1 - Burst behaviours of aero-engine turbine disk at overspeed conditions N2 - This presentation focuses on the basic ideas and current status of the development of an arithmetical method to predict the failure rotational speed of turbine disks. The certification specification requires that a gas turbine aero-engine must hold 5 minutes at overspeed conditions without critical failure. Therefore, instead of experimental proof from spin-tests using test-disks similar to engine components, it is considered to use simple specimen with similar test conditions compared to real overspeed scenarios. These test conditions, or stress fields are determined using arithmetical method, e.g. finite element method, with consideration of fracture mechanics under quasi-static conditions with a given rotational speed. Failure modes like hoop burst and rim peeling are considered during determination of stress fields. Various crack-tip parameters are used to explore the similarity of stress field between simple specimen and real overspeed scenarios. Additionally, probabilistic aspects and the implementation of a global stability criterion for overspeed analysis are also considered. T2 - 43rd Materials Mechanics Seminar CY - Sani, Chalkidiki, Greece DA - 06.06.2022 KW - Structural integrity KW - Fracture mechanics KW - Turbine disk KW - Overspeed PY - 2022 AN - OPUS4-55081 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhu, Jiangchao T1 - Fracture mechanics-based structural integrity assessment of aero-engine turbine disks under overspeed conditions N2 - Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on production-similar disks. While these tests provide, on the one hand, a reliable definition of the critical conditions for real components, on the other hand they represent a relevant cost item for engine manufacturers. The aim of this work is to present part of a fracture mechanics-based procedure under development which aims at replacing the tests on production-similar disks with lab tests on fracture mechanics specimens. In particular, the rim-peeling failure mode is considered as case study. A semi-circular surface crack is modelled at the most stressed region at the diaphragm of a turbine disk, with the crack plane perpendicular to the radial direction. The crack is therefore subjected to a biaxial stress state and grows under increasing rotational speed until it triggers the rim-peeling failure. The finite element simulation of the cracked disk considers the real thermal and mechanical loading conditions. In order to design a lab representative specimen, beside the crack driving force, expressed in terms of J-integral, also the constraint to plastic deformation e.g., stress triaxiality, at the crack-tip must be similar for the same crack in the specimen and in the disk. This has been achieved and as expected, both the highest J-integral and constraint factor are calculated at the same location along the crack front for both disk and specimen. The results of the structural integrity assessment in the form of a Failure Assessment Diagram (FAD) show good agreement between designed specimen and disk both in terms of expected failure mode and value of the critical speed. Probabilistic aspects are also considered in the calculations. T2 - Turbo Expo 2022 CY - Rotterdam, Netherlands DA - 13.06.2022 KW - Structural integrity KW - Fracture mechanics KW - Turbine disk KW - Overspeed PY - 2022 AN - OPUS4-55082 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Griesche, Axel A1 - Pfretzschner, Beate A1 - Taparli, Ugur Alp A1 - Kardjilov, N. T1 - Time-Resolved Neutron Bragg-Edge Imaging: A Case Study by Observing Martensitic Phase Formation in Low Temperature Transformation (LTT) Steel during GTAW N2 - Polychromatic and wavelength-selective neutron transmission radiography were applied during bead-on-plate welding on 5 mm thick sheets on the face side of martensitic low transformation temperature (LTT) steel plates using gas tungsten arc welding (GTAW). The in situ visualization of austenitization upon welding and subsequent α’-martensite formation during cooling could be achieved with a temporal resolution of 2 s for monochromatic imaging using a single neutron wavelength and of 0.5 s for polychromatic imaging using the full spectrum of the beam (white beam). The spatial resolution achieved in the experiments was approximately 200 µm. The transmitted monochromatic neutron beam intensity at a wavelength of λ = 0.395 nm was significantly reduced during cooling below the martensitic start temperature M s since the emerging martensitic phase has a ~10% higher attenuation coefficient than the austenitic phase. Neutron imaging was significantly influenced by coherent neutron scattering caused by the thermal motion of the crystal lattice (Debye–Waller factor), resulting in a reduction in the neutron transmission by approx. 15% for monochromatic and by approx. 4% for polychromatic imaging. KW - Neutron radiography KW - Debye–Waller factor KW - Austenite-to-martensite transformation KW - Low transformation temperature (LTT) steel KW - Bragg-edge imaging KW - Gas tungsten arc welding (GTAW) PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-559077 DO - https://doi.org/10.3390/app112210886 VL - 11 IS - 22 PB - MDPI AN - OPUS4-55907 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bergant, M. A1 - Larrosa, N. A1 - Yawny, A. A1 - Madia, Mauro T1 - Short crack growth model for the evaluation of the fatigue strength of WAAM Ti-6Al-4V alloy containing pore-type defects N2 - The role of defects in the fatigue strength of Wire Arc Additively Manufactured (WAAMed) Ti-6Al-4V is analysed by means of the IBESS model, a fracture mechanics short crack growth approach based on the cyclic R-curve. Pores and crack-like defects are analysed. Estimations of the role of pore shape and size agree well with published fatigue data of WAAM Ti-6Al-4V with pores. The model is also used to explain the effect of fabrication defects on the scatter of experimental data. This demonstrates that short crack growth models represent a suitable engineering tool for the fatigue assessment of defective AM materials. KW - WAAM Ti-6Al-4V KW - Cyclic R-curve KW - IBESS model for short cracks KW - Kitagawa-Takahashi (K-T) diagram PY - 2023 DO - https://doi.org/10.1016/j.engfracmech.2023.109467 SN - 0013-7944 VL - 289 SP - 1 EP - 21 PB - Elsevier Ltd. AN - OPUS4-57963 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Liepold, Philipp T1 - Bewertung der Erstarrungsrissanfälligkeit hochfester Schweißverbindungen mittels MVT-Test N2 - Der modifizierte Varestraint-Transvarestraint-Test (MVT-Test) ist die an der BAM vorherrschende Version des Varestraint-Tests der weltweit Anwendung findet. Die Auswertung des Tests erfolgt durch Messen von Risslängen unter dem Lichtmikroskop. Der Vortrag beleuchtet Theorien über die Aussagekraft der Messung, stellt neue Herangehensweisen vor und vergleicht diese anhand von Beispielen. T2 - BMDK CY - Magdeburg, Germany DA - 24.05.2023 KW - MVT KW - Varestraint PY - 2023 AN - OPUS4-57620 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Spannungen beim Schweißen von Bauteilen N2 - Der Vortrag gibt einen Überblick über das Phänomen der Schweißeigenspannungen. Es wird auf die Bedeutung und Entstehungsursachen eingegangen. Mit besonderem Fokus auf die Eigenspannungen beim Schweißen von Komponenten werden Messmöglichkeiten und Anwendungsbeispiele vorgestellt. T2 - Jahresmitgliederversammlung DVS Bezirksverbandes Berlin CY - Berlin, Germany DA - 24.04.2024 KW - Eigenspannungen PY - 2024 AN - OPUS4-59944 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Liepold, Philipp T1 - Anwendung von CNNs zur verbesserten Auswertung von MVT-Tests N2 - Durch die Anwendung von Convolutional Neural Networks (CNNs) kann die Auswertung von Modifizierten Varestraint-Transvarestraint-Tests (MVT) erheblich verbessert werden. Im MVT-Test werden Proben während des Schweißvorgangs über einen Zylinder gebogen. Die auf der Oberfläche der Probe sichtbare Rissstruktur gibt über Parameter wie die Gesamtrisslänge Auskunft über die Erstarrungsrissbeständigkeit der verwendeten Kombination aus Grundstoff, Schweißzusatz und Schweißparametern. Jedoch kann eine Auswertung unter dem Mikroskop sehr aufwendig sein und je nach Beobachter unterschiedliche Ergebnisse liefern. Mit Hilfe von CNNs wird die Auswertung der Risse automatisiert was Genauigkeit, Geschwindigkeit und Vergleichbarkeit verbessert. T2 - BMDK CY - Magdeburg, Germany DA - 05.12.2022 KW - CNN KW - MVT KW - KI PY - 2022 AN - OPUS4-56839 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhu, Jiangchao A1 - Madia, Mauro A1 - Schurig, M. A1 - Schlums, H. A1 - Zerbst, Uwe T1 - Fracture mechanics-based structural integrity assessment of aeroengine turbine disks under overspeed conditions N2 - Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on productionsimilar disks. While these tests provide, on the one hand, a reliable definition of the critical conditions for real components, on the other hand they represent a relevant cost item for engine manufacturers. The aim of this work is to present part of a fracture mechanics-based procedure under development which aims at replacing the tests on production-similar disks with lab tests on fracture mechanics specimens. In particular, the rimpeeling failure mode is considered as case study. A semi-circular surface crack is modelled at the most stressed region at the diaphragm of a turbine disk, with the crack plane perpendicular to the radial direction. The crack is therefore subjected to a biaxial stress state and grows under increasing rotational speed until it triggers the rim-peeling failure. The finite element simulation of the cracked disk considers the real thermal and mechanical loading conditions. In order to design a lab representative specimen, beside the crack driving force, expressed in terms of � -integral, also the constraint to plastic deformation e.g., stress triaxiality, at the crack-tip must be similar for the same crack in the specimen and in the disk. This has been achieved and as expected, both the highest � -integral and constraint factor are calculated at the same location along the crack front for both disk and specimen. The results of the structural integrity assessment in the form of a Failure Assessment Diagram (FAD) show good agreement between designed specimen and disk both in terms of expected failure mode and value of the critical speed. Probabilistic aspects are also considered in the calculations. T2 - ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition (GT2022) CY - Rotterdam, The Netherlands DA - 13.06.2022 KW - Fracture mechanics KW - Burst KW - Turbine disk PY - 2022 SP - 1 EP - 7 PB - ASME AN - OPUS4-55903 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhu, Jiangchao T1 - Kennwertermittlung für die Bewertung der Integrität einer Turbinenscheibe bei Überdrehzahl N2 - Turbinenscheiben sind thermisch und mechanisch hochbeanspruchte, sicherheitsrelevante Komponenten in Gasturbinen. Ihre Integrität wird in Bauteiltests unter Überdrehzahlbedingungen nachgewiesen. Kontext des Aufsatzes ist die Erarbeitung einer zusätzlichen Bewertungsebene auf der Grundlage von Versuchen unter monotoner Beanspruchung, die die Beanspruchung im Bauteil realistisch wiedergeben soll. Dazu werden zwei Typen von bruchmechanischen Proben anwendungsnah ausgelegt und aus einer Turbinenscheibe ausgeschnitten: Der erste Typ ist eine biaxiale Probe, die die Beanspruchung und den Dehnungsbehinderungszustand am Diaphragm der Turbinenscheibe abbildet, die zweite eine bruchmechanische Probe, die die einachsige Beanspruchung und den Dehnungsbehinderungszustand am Bore der Turbinenscheibe wiedergibt. Im Rahmen eines Schadentoleranzansatzkonzepts ist anschließend jeweils ein halbelliptischer Riss an den genannten Stellen der Turbinenscheibe zu betrachten. Mittels numerischer Berechnungen wird ein kritischer Punkt auf der Rissfront des Risses am Diaphragm bestimmt, dort wo die höchste Rissspitzenbelastung (J-Integral) auftritt. Auf der Basis der Rissspitzenbelastung, des Dehnungsbehinderungszustands und des entsprechenden Spannungsverhältnisses an diesem kritischen Punkt wird eine Kreuzprobe mit einem Durchriss konzipiert, die diese Verhältnisse im Bauteil widerspiegelt. Die Versuche werden unter der Temperatur am Diaphragm der Turbinenscheibe durchgeführt. Die J-R-Kurve und die plastische Kollapsgrenze werden bestimmt. Auch die einachsigen Versuche werden unter der Temperatur am Bore der Turbinenscheibe durchgeführt. Die Zugprobe enthält halbelliptische Oberflächenrisse. Ähnlich wie bei der Auslegung der Kreuzproben werden die Rissspitzenbelastung, der Dehnungsbehinderungszustand und das Spannungsverhältnis vergleichbar mit der Turbinenscheibe eingestellt. Die J-R-Kurve und die plastische Kollapsgrenze werden bestimmt. Mit den Versuchsergebnissen werden die kritischen Lasten für verschiedene Versagensmechanismen (instabiles Risswachstum, plastischer Kollaps) der bruchmechanischen Proben ermittelt, die der kritischen Überdrehzahl der Turbinenscheibe entsprechen. T2 - 40. Vortrags- und Diskussionstagung Werkstoffprüfung 2022 CY - Dresden, Germany DA - 27.10.2022 KW - Turbine disk KW - Fracture mechanics KW - Biaxial test KW - Burst PY - 2022 AN - OPUS4-56148 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strauß, Lea T1 - Empirical Model for Fatigue Life Prediction N2 - Laser-based powder bed fusion (PBF-LB) is an advanced additive manufacturing technique renowned for its precision and capability to fabricate complex metal components. However, the high thermal gradients and rapid cooling rates intrinsic to this process introduce significant process-induced effects, such as inhomogeneities, surface roughness, anisotropy, and residual stress, all of which critically influence the fatigue behavior of the produced parts. This study investigates the fatigue performance of AlSi10Mg samples produced by PBF-LB, examining the impact of varying surface conditions, geometries, and residual stress levels. Fatigue life prediction models are formulated based on nominal stress amplitude, residual stress, notch factor, crackinitiating inhomogeneity, and surface roughness, with smooth samples serving as a baseline reference. The study presents two empirical models for predicting fatigue life and fatigue strength using S-N curves and the Kitagawa-Takahashi diagram with the El Haddad approach, derived from comprehensive experimental data, including finite element modelling, fatigue life measurements, surface roughness evaluations, and residual stress analysis. T2 - ICAM2024 CY - Atlanta, GA, USA DA - 28.10.2024 KW - AlSi10Mg KW - Kitagawa-Takahashi diagram KW - Equivalent stress KW - Fatigue life prediction KW - PBF-LB/M PY - 2024 AN - OPUS4-61538 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro T1 - Fatigue Strength of Aerospace Parts Repaired by Cold Spray N2 - Aerospace components are safety critical parts, which are often replaced when found defective after the fabrication process or after periodic inspection in-service. Cold spray repair is a promising and cost-saving alternative to replacing worn parts. Depositing materials in decent quality fill machined damage volumes can enhance the performance of refurbished parts and extend their working life. Furthermore, repair represents a resource-efficient and green process in a world targeting at decarbonization of many industrial sectors. Component repair consists of a defined sequence of operations. First, damage is removed by machining, then new material is applied by cold spray on the machined substrate. Usually, the original functional shape of the component is restored by machining. Post-spraying heat treatments can be applied where required. Despite the advantages, cold spray repair still suffers from major limitations which prevent its application in safety relevant parts. The main challenges are posed by the poor adhesion strength, the porosity inherent in the manufacturing process, the reduced ductility and the presence of residual stresses. This work presents recent results obtained in the frame of the cluster project CORE devoted to the development of automatized repair of aerospace parts by cold spray. The investigations consider high-strength aluminum alloys typically used in structural applications in the aerospace industry. As the fatigue properties are crucial to the safe application of repaired components, and given the presence of process-induced defects, a damage tolerant framework is peculiarly suitable for the structural integrity assessment of repaired commponents and give an indication of the permissible defects to optimize the parameters of the cold spray process. Several high cycle fatigue and fatigue crack propagation tests have been performed to compare the fatigue performance of base and repaired materials. The mechanical tests are corroborated by fractographic and microstructural investigations. T2 - ICAM2024 CY - Atlanta, GA, USA DA - 28.10.2024 KW - Cold Spray KW - Aerospace KW - Repair KW - Structural Integrity KW - Fatigue Strength PY - 2024 AN - OPUS4-61539 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kardjilov, Nikolay T1 - Neutron Thermo Tomography N2 - This study presents an investigation of the neutron transmission signal as a function of martensitic steel sample temperature and phase transformation during a welding process. A theoretical description that includes the Debye-Waller factor was used to describe the temperature influence on the neutron cross-sections. Neutron imaging using a monochromatic beam helps to observe transmission variations related to the martensitic-austenitic phase transformations before the Bragg-edge and to the material temperature above the Bragg-edge. In-situ neutron imaging of welding experiments show the distribution of the phase transformation and of the temperature in bulk steel samples. The performed finite element modelling of expected temperature distributions shows good agreement with the obtained experimental data. T2 - Neutron Wavelength-Dependent Imaging Workshop (NEUWAVE-12) CY - Lund, Sweden DA - 01.09.2024 KW - Neutron Imaging KW - Energy Selective KW - Neutron Thermo Tomography PY - 2024 AN - OPUS4-61265 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Möglichkeiten zur Optimierung von schweißbedingten Beanspruchungen durch Einsatz von LTT-Zusatzwerkstoffen N2 - Der Vortrag gibt einen Überblick zum Thema Low Transformation Temperature (LTT) Zusatzwerkstoffe. Es wird gezeigt, wie mit einem Experiment unter Nutzung von Sychrotronstrahlung das Phänomen der Umwandlungsplastizität untersucht werden kann. T2 - 12. Vollversammlung des SFB 1120: Summer School 2024 CY - Steinfeld (Kall), Germany DA - 11.06.2024 KW - Eigenspannungen KW - LTT-Zusatzwerkstoffe KW - Hochfester Stahl PY - 2024 AN - OPUS4-60259 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel T1 - Crystallographic phase transformations and corresponding temperature distributions during gtaw of supermartensitic stainless steel visualized by nbei N2 - We investigated the phase transformations during butt-welding of supermartensitic steel plates with help of Neutron-Bragg-Edge Imaging (NBEI). Gas tungsten arc welding (GTAW) was used with a motorized torch allowing for automated weldments. The austenitization in the heat affected zone (HAZ) could be clearly visualized at λ = 0.39 nm, a wavelength smaller than the Bragg edge wavelengths of both austenite and martensite. The re-transformation into the martensitic phase during cooling was clearly detected. However, we observed an unexpected additional change in transmission at λ = 0.44 nm, a wavelength larger than the wavelength of the Bragg edges of both the martensitic and austenitic phases. We attribute this change to the Deybe-Waller-Factor that describes the temperature dependence of coherent scattering at a crystal lattice. The observed two-dimensional attenuation map corresponds well with a temperature distribution modelling by software macros in ANSYS [3]. Here, the absolute temperature values could be achieved by calibrating the modelled attenuation with help of a thermocouple placed at the steel plate. This allows in return for a direct two-dimensional temperature reading based on the Debye-Waller-relation between neutron attenuation and sample temperature. T2 - WCNR-12 CY - Idaho Falls, Id, USA DA - 02.06.2024 KW - Neutron KW - Radiography KW - Welding PY - 2024 AN - OPUS4-60242 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Best practice: How to work with a mobile diffractometer N2 - Beginning with a general overview about resdiual stress determination by X-ray diffraction, the presentation is focussing on some does and dont's when working with a portable diffractometer. T2 - European Conference on Residual Stresses 11 - Tutorial 1: Residual stresses in additive manufacturing CY - Prague, Czech Republic DA - 03.06.2024 KW - Residual stress KW - X-ray diffraction PY - 2024 AN - OPUS4-60287 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 - JOUR A1 - Strauß, Lea A1 - Duarte, Larissa A1 - Kruse, Julius A1 - Madia, Mauro A1 - Löwisch, Günther T1 - An equivalent stress approach for predicting fatigue behavior of additively manufactured AlSi10Mg N2 - Laser-based powder bed fusion (PBF-LB) is an advanced additive manufacturing technique renowned for its precision and capability to fabricate complex metal components. However, the high thermal gradients and rapid cooling rates intrinsic to this process introduce significant process-induced effects, such as inhomogeneities, surface roughness, anisotropy, and residual stress, all of which critically influence the fatigue behavior of the produced parts. This study investigates the fatigue performance of AlSi10Mg samples produced by PBF-LB, examining the impact of varying surface conditions, geometries, and residual stress levels. Fatigue-life prediction models are formulated based on nominal stress amplitude, residual stress, form factor, crack-initiating inhomogeneity, and surface roughness, with smooth samples serving as a baseline reference. The study presents two empirical models for predicting fatigue life and fatigue strength using S–N curves and the Kitagawa–Takahashi diagram with the El Haddad approach, derived from comprehensive experimental data, including finite element modeling, fatigue-life measurements, surface roughness evaluations, and residual stress analysis. KW - AlSi10Mg KW - Kitagawa–Takahashi diagram KW - El Haddad KW - Equivalent stress KW - Fatigue-life prediction KW - PBF-LB/M PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625176 DO - https://doi.org/10.1007/s40964-025-00974-0 SP - 1 EP - 16 PB - Springer Science and Business Media LLC AN - OPUS4-62517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hilgenberg, Kai A1 - Madia, Mauro T1 - Additive Fertigung von Bauteilen und Strukturen – Grenzen, Risiken, Chancen N2 - Dieser Eröffnungsvortrag des DVM-Tages beleuchtet Herausforderungen in der additiven Fertigung und plädiert für eine enge Zusammenarbeit von Fertigungstechnik und Bruchmechanik für die Vorhersage der Lebensdauer AM-gefertigter Komponenten. T2 - DVM-Tag CY - Berlin, Germany DA - 08.04.2025 KW - Additive Fertigung KW - Digitale Qualitätssicherung KW - Ermüdungsfestigkeit PY - 2025 AN - OPUS4-62971 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Kurzrisswachstum in additiv gefertigtem austenitischem Edelstahl 316L N2 - Diese Untersuchung beschäftigt sich mit der Charakterisierung von Kurzrisswachstum in mittels Laser-Pulverbett-Verschmelzen (LPBF - Laser Powder Bed Fusion) hergestelltem rostfreien austenitischen Stahl. Spezifischer wird die Ermittlung zyklischer R-Kurven untersucht. Diese beschreiben den Aufbau des Widerstands gegen Ermüdungsrisswachstum - d.h. des Schwellenwertes - aufgrund von Rissschließeffekten bei physikalisch kurzen Rissen. Mit Hilfe der zyklischen R-Kurven kann die Fähigkeit eines Bauteils, physikalisch kurze Risse zu arretieren, charakterisiert werden. Wir verfügen damit über eine Schnittstelle zwischen klassischer Ermüdung und Bruchmechanik. Das ist gerade auch für additiv gefertigte (AM – Additive Manufacturing) Materialien von Interesse. Diese weisen prozessintrinsische Defekte auf, die als Initiierungsstellen kurzer Ermüdungsrisse agieren. Im Rahmen der experimentellen Untersuchungen wurden zyklische R-Kurven für konventionellen und LPBF AISI-316L-Stahl ermittelt. Insbesondere wurde der Einfluss verschiedener Wärmebehandlungen (WB1: 450°C, WB2: 800°C und WB3: 900°C) auf das Wachstumsverhalten physikalisch kurzer Risse im LPBF-Material untersucht. Aufgrund hoher Eigenspannungen war die Ermittlung des Kurzrisswachstumsverhaltens bei WB1 nicht möglich. Für WB2 und WB3 ergaben sich sehr unterschiedliche zyklische R-Kurven. Untersuchungen der Eigenspannungen, der Bruchfläche (insbesondere der Rauheit) und der Mikrostruktur sollen die Ursachen für das unterschiedliche Verhalten erklären. Die Ergebnisse werden mit den Verhältnissen in konventionellem Material verglichen. T2 - 41. Werkstoffmechanikseminar TU Darmstadt CY - Online meeting DA - 26.10.2020 KW - AM KW - Additiv KW - Zyklische R-Kurve KW - 316L KW - Ermüdung KW - Ermüdungsrisswachstum KW - Risswachstum PY - 2020 AN - OPUS4-51603 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Ermittlung des intrinsischen Schwellenwerts und dessen Validierung als Werkstoffparameter N2 - Die schadenstolerante Bewertung von zyklisch beanspruchten Bauteilen auf bruchmechanischer Grundlage ist von großer praktischer Bedeutung, insbesondere für die Spezifizierung von Inspektionsintervallen. Eine Schwachstelle der gegenwärtigen Vorgehensweise bildet der nur ungenügend verstandene Schwellenwertbereich der da/dN-ΔK -Kurve. Relevant ist das deshalb, weil viele Bauteile bei Lasten betrieben werden, die in eben diesen Bereich fallen. Der Vortrag beschäftigt sich mit Unsicherheiten bei der Ermittlung des Schwellenwertes, mit Einflussparametern, die dabei zu berücksichtigen sind, und mit einem Vorschlag zur konservativen Einbeziehung des Schwellenwertbereichs in die Bauteilauslegung. Der Schwellenwert gegen Ermüdungsrissausbreitung ist als der zyklische Spannungsintensitätsfaktor definiert, unterhalb dessen kein Risswachstum mehr stattfindet. Dabei ist zu beachten, dass der Wert in der konventionellen da/dN-ΔK -Kurve auf Langrisswachstum beschränkt ist und, strenggenommen, auch das nur dann, wenn das Rissschließphänomen voll ausgebildet ist. Unter Rissschließen versteht man das Schließen des zyklisch beanspruchten Risses in der Regel oberhalb des Nulldurchgangs der Last. Wichtige Rissschließmechanismen sind das plastizitäts-, das rauheits- und das oxid-induzierte Schließen wobei die beiden letztgenannten im Schwellenwertbereich dominierend sind. Der Schwellenwert selbst besteht aus zwei Anteilen, einem intrinsischen, der von den elastischen Konstanten und vom Gittertyp abhängt und einem extrinsischen, der mit dem Aufbau der Rissschließeffekte zusammenhängt und von Parametern wie der Mikrostruktur, dem Spannungsverhältnis aus Unter- und Oberlast und der Risstiefe beeinflusst wird. In Fällen, bei denen oxid-induziertes Rissschließen eine Rolle spielt, hängt der erhaltene Wert des Schwellenwerts vom experimentellen Verfahren ab, wobei die konventionelle Lastabsenkung nach Standard nicht-konservative Werte ergeben kann. Der Vortrag thematisiert die unterschiedlichen Optionen der experimentellen Ermittlung mit besonderem Fokus auf dem intrinsischen Schwellenwert und, davon ausgehend, die Anbindung an den rissschließkorrigierten Paris-Bereich der da/dN-ΔK -Kurve. T2 - Werkstoffmechanikseminar 2020 CY - Online meeting DA - 26.10.2020 KW - Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung KW - Schadenstolerante Bauteilauslegung KW - Restlebensdauer PY - 2020 AN - OPUS4-51604 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Der Schwellenwert der da/dN-∆K-Kurve als Auslegungskriterium für die Bauteilbewertung N2 - Für die Bestimmung der Restlebensdauer zyklisch beanspruchter Bauteile kommt dem Schwellenwert für Ermüdungsrissausbreitung ΔKth und dem sich anschließenden Schwellenwertbereich der dadN⁄-ΔK-Kurve große Bedeutung zu. Dem stehen Unsicherheiten bei der Bestimmung und Analyse gegenüber. Der Aufsatz befasst sich mit der Ermittlung des sogenannten intrinsischen Schwellenwerts, der als robuster Eingangsparameter für eine „rissschließfreie“ Analyse der Restlebensdauer von entscheidender Bedeutung ist. T2 - Tagung Werkstoffprüfung 2020 CY - Online meeting DA - 03.12.2020 KW - Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung KW - Schadenstolerante Bauteilauslegung KW - Restlebensdauer PY - 2020 AN - OPUS4-51754 LA - deu 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 - Duarte, Larissa T1 - Einflussfaktoren auf die Bestimmung von Rissfortschrittsdaten N2 - Rissfortschrittsdaten sind notwendig für die bruchmechanische Bewertung zyklisch beanspruchter Bauteile. Deren zuverlässige experimentelle Ermittlung wird von verschiedenen Faktoren beeinflusst, was wiederum zur Unsicherheit bei der Restlebensdauerprognose führen kann. Der Vortrag befasst sich mit der Untersuchung der Einflussfaktoren auf die Ermittlung von Rissfortschrittsdaten. Eine Prozedur zur Berechnung der Restlebensdauer wird eingeführt, die auf rissschließfrei Rissfortschrittsdaten basiert. T2 - 42. Werkstoffmechanikseminar 2021 CY - Online meeting DA - 11.10.2021 KW - Rissfortschrittsdaten KW - Einflussfaktoren KW - Restlebensdauerprognose PY - 2021 AN - OPUS4-53615 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Giese, Marcel T1 - Experimentelle Charakterisierung der WIG-Schweißeignung einer Hoch- und Mediumentropie-Legierung N2 - Equiatomic multi-element systems with defined entropy are a relatively new mate-rial concept for alloy production. These alloys consist of at least five elements in equiatomic distribution in the case of high entropy alloys (HEA) and three to four elements in equiatomic distribution in the case of medium entropy alloys (MEA). Previous studies on these alloys have focused primarily on their production, micro-structure and the resulting material properties. Meanwhile, the focus here is on the processing of the alloys and their influence on future applications. Up to now, there has been insufficient knowledge of the materials and processes involved in weld-ing. In this work, therefore, the weldability of a CoCrFeMnNi-HEA and a CoCrNi-MEA by means of a TIG welding process was investigated as a basic system. To this end, the welding parameters were first determined on a reference alloy (Ni-based: 2.4858) and transferred to the welding of the CoCrFeMnNi-HEA and CoCrNi-MEA. Weldability was assessed by testing the absence of defects and microstructures obtained. The weld metal exhibited the dendritic microstructure typical of TIG, with microsegregations forming as interdendritic phases. Increased hardness was de-tected in the weld metal compared to the base metal. In the heat-affected zone, there was little grain growth and, in both alloys, the formation of hot cracks after welding. The cause of the cracks was to be found in the specimen preparation, which had an influence on the subsequent processing. After elimination of this in-fluence, no welding process-related imperfections were found in the CoCrFeMnNi-HEA and CoCrNi-MEA. In summary, both materials show good fusion weldability by TIG welding. The re-sults of this work thus contribute to the understanding of the weldability of HEA and in particular for CoCrNi-MEA, which was considered in this depth for the first time. T2 - Verteidigung Masterarbeit Otto von Guericke Universität Magdeburg CY - Magdeburg, Germany DA - 20.10.2021 KW - Hochentropielegierung KW - Mediumentropielegierung KW - WIG-Schweißen PY - 2021 AN - OPUS4-53643 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Investigation on the influence of different testing methods and parameters on the determination of fatigue crack growth data N2 - The correct determination of fatigue crack propagation data is of great importance for the damage tolerance design of engineering components, especially with regard to the calculation of residual lifetime and the establishment of inspection intervals. The fatigue crack propagation threshold Δ𝐾th, in this respect, is a crucial input parameter for simulating crack growth, since it corresponds to the stress intensity factor range at which a non-growing crack starts to propagate. However, the experimental determination of Δ𝐾th, as well as its application, is still confronted with few issues related among others to the load ratio (R) dependency of Δ𝐾th, the testing procedure, and environmental effects. These can lead to large scatter and significant errors in the prediction of component failure. In this context, the use of the intrinsic fatigue crack propagation threshold Δ𝐾th,eff in component assessment is a promising alternative, since it does not depend on a number of factors that affect Δ𝐾th, but only on the elastic properties (𝐸-modulus) and the lattice (Burger’s vector ‖𝑏‖) of the material. The aim of the present work is therefore to investigate different experimental procedures for the determination of Δ𝐾th,eff, namely: (a) conventional load reduction (LR) procedures, (b) the 𝐾max procedure and (c) compression pre-cracking load reduction and constant amplitude (respectively CPLR and CPCA) methods. Furthermore, the determination of Δ𝐾th has been carried out varying some testing parameters, such as test frequency, Δ𝐾 at the beginning of the crack propagation test (Δ𝐾0) and stress ratio (R). The results are statistically analyzed and a discussion about the use of Δ𝐾th and Δ𝐾th,eff for the component fatigue assessment is presented. T2 - 6th. International Virtual Conference of Engineering Against Failure CY - Online meeting DA - 23.06.2021 KW - Crack closure KW - Damage tolerance assessment KW - Residual lifetime KW - Intrinsic fatigue crack propagation threshold PY - 2021 AN - OPUS4-52899 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Vergleichende Untersuchungen zum intrinsischen Schwellenwert der da/dN-∆K Kurve N2 - Für die Bestimmung der Restlebensdauer zyklisch beanspruchter Bauteile kommt dem Schwellenwert für Ermüdungsrissausbreitung, Δ𝐾𝑡ℎ, und dem sich anschließenden Schwellenwertbereich der 𝑑𝑎𝑑𝑁⁄−Δ𝐾-Kurve große Bedeutung zu. Dem stehen Unsicherheiten bei der Bestimmung und Analyse gegenüber. Der Aufsatz befasst sich mit der Ermittlung des sogenannten intrinsischen Schwellenwerts, der als robuster Eingangsparameter für eine „rissschließfreie“ Analyse der Restlebensdauer von entscheidender Bedeutung ist. T2 - DVM-Arbeitskreis „Bruchmechanik und Bauteilsicherheit“ 2021 CY - Online meeting DA - 18.02.2021 KW - Schadenstolerante Bauteilauslegung KW - Restlebensdauer KW - Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung PY - 2021 AN - OPUS4-52263 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - The effect of the environmental conditions on the threshold against fatigue crack propagation N2 - The threshold against fatigue crack propagation (ΔKth) is a crucial parameter for the damage tolerance assessment of engineering components subjected to cyclic loading and it is composed by two distinct components, one intrinsic, dependent on the elastic material properties and the lattice type, and one extrinsic, related to the occurrence of crack closure effects. An important issue is that several factors can influence ΔKth and, in general, the fatigue crack propagation behavior. In this work, the influence of the experimental procedure, air humidity and test parameters on da/dN-ΔK data has been investigated. Results are discussed with their potential causes and consequences on the calculations of the residual lifetime. T2 - Conference Fatigue Design 2021 CY - Online meeting DA - 17.11.2021 KW - Fatigue crack propagation threshold KW - Crack closure effect KW - Experimental procedure KW - Environmental conditions PY - 2021 AN - OPUS4-53770 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro T1 - Estimation of the Kitagawa-Takahashi diagram by cyclic R-curve analysis N2 - The Kitagawa-Takahashi (KT) diagram is a proven concept for describing the fatigue limit in presence of a defect or crack. It can be determined empirically with great experimental effort. It can also be estimated by means of the El Haddad relationship if the endurance limit and the long fatigue crack propagation threshold are available in reasonable accuracy. A third option is the determination using the cyclic R-curve, which describes the dependency of the fatigue crack propagation threshold on the crack growth at the short crack propagation stage. This can be experimentally determined using a closure-free initial pre-crack. It can then be applied to the determination of crack arrest for a given applied load and a given defect or crack size. Compared to the other two methods mentioned above, this option has considerable advantages: It can be applied to any component and any stress ratio. It allows the treatment of multiple cracks and provides estimations of the S-N curve in the finite life regime as well as at the endurance limit. Compared to the empirical determination of the KT diagram, the experimental effort is significantly lower and compared to the El Haddad approach it avoids problems such as the use of non-conservative long fatigue crack propagation thresholds (when the conventional load reduction method is applied to materials prone to corrosion) and the mathematical predetermination of the curve shape. The work introduces the method and provides a critical discussion as well as quantitative comparison between the different methods. T2 - Fatigue Design 2021 CY - Online meeting DA - 17.11.2021 KW - Fatigue life KW - Endurance limit KW - Kitagawa-Takahashi diagram KW - Cyclic R-curve PY - 2021 AN - OPUS4-53778 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönherr, J. A. T1 - Robust Determination of Fatigue Crack Propagation Thresholds from Crack Growth Data N2 - To assess the ability of cracks to grow, a robust determination of the threshold against fatigue crack propagation ∆Kth is of paramount importance. The standards ASTM E647 and ISO 12108 introduce operational definitions of ∆Kth based on the crack propagation rate da/dN. For evaluating ∆Kth, both suggest fitting a linear function to a defined subset of the logarithmic ∆K – da/dN test data, where ∆Kth follows by evaluating the linear function at da/dN = 10-7 mm/cycle and da/dN = 10-8 mm/cycle, respectively. In general, this kind of fit suffers from a bad representation of the actual curvature of the crack propagation curve. Therefore, we propose a robust method for evaluating ∆Kth using a non-linear function that reduces the artificial conservativeness induced by the evaluation method as well as the susceptibility to scatter in test data and the influence of test data density. The method is calibrated against a large set of S690QL crack growth data obtained from a total of 48 specimens, and validated against a set of S355NL and S960QL data (3 specimens each), obtained as a part the IBESS (integral fracture mechanics determination of the fatigue strength of welds) project. T2 - ECF23 (European Conference on Fracture 2022) CY - Madeira, Portugal DA - 27.06.2022 KW - Fatigue crack propagation threshold KW - ISO 12108 KW - ASTM E647 KW - Data evaluation methods KW - Experimental determination PY - 2022 AN - OPUS4-55252 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhu, Jiangchao T1 - Bruchmechanische Bewertung der Integrität einer Turbinenscheibe bei Überdrehzahl N2 - Turbinenscheiben sind thermisch und mechanisch hochbeanspruchte, sicherheitsrelevante Komponenten in Gasturbinen. Ihre Integrität wird in Bauteiltests unter Überdrehzahlbedingungen nachgewiesen. Kontext des Aufsatzes ist die Erarbeitung einer zusätzlichen Bewertungsebene auf der Grundlage von Versuchen unter monotoner Beanspruchung, die die Beanspruchung im Bauteil realistisch wiedergeben soll. Betrachtet wird ein halbelliptischer Riss, der bei der weiteren Ausbreitung als Umfangsriss wächst (rim peeling). Die Simulation dieser Stelle im Bauteil schließt die mechanische und thermische Beanspruchung sowie sie Dehnungsbehinderung ein. Letztere wird anhand zweier Parameter, der Spannungsmehrachsigkeit ℎ und des (allerdings modifizierten) Constraint-Parameters nach Newman, der die Spannungen über den plastisch verformten Bereich mittelt, bestimmt. Erwartungsgemäß zeigt sich, dass die höchste Dehnungsbehinderung weder an den Oberflächenpunkten, noch an den tiefsten Punkten, sondern an einer Stelle zwischen beiden auf der Rissfront auftritt. Als Versuchsgeometrie für die monotonen Tests soll eine Kreuzprobe mit wanddurchdringenden Rissen ausgehend von einer Innenbohrung dienen. Durch geeignete Wahl der Risstiefe sowie der in beiden Richtungen angreifenden Kräfte gelingt es, bauteiladäquate Zustände zu erzeugen. T2 - 54. Tagung des Arbeitskreis Bruchmechanik und Bauteilsicherheit CY - Online meeting DA - 22.02.2022 KW - Struktur Integrität KW - Turbinenscheibe KW - Constraint KW - Bruchmechanik PY - 2022 AN - OPUS4-54402 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pfretzschner, Beate A1 - Schaupp, Thomas A1 - Hannemann, Andreas A1 - Schultz, Michael A1 - Griesche, Axel T1 - On the Genesis of Artifacts in Neutron Transmission Imaging of Hydrogenous Steel Specimens N2 - Hydrogen-charged supermartensitic steel samples were used to systematically investigate imaging artifacts in neutron radiography. Cadmium stencils were placed around the samples to shield the scintillator from excessive neutron radiation and to investigate the influence of the backlight effect. The contribution of scattered neutrons to the total detected intensity was investigated by additionally varying the sample-detector distance and applying a functional correlation between distance and intensity. Furthermore, the influence of the surface roughness on the edge effect due to refraction was investigated. KW - Refraction KW - Neutron imaging KW - Hydrogen KW - Supermartensitic steel KW - Backlight KW - Scattering PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506587 DO - https://doi.org/10.3390/jimaging6040022 VL - 6 IS - 22 SP - 1 EP - 10 PB - MDPI CY - Basel, Switzerland AN - OPUS4-50658 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Vecchiato, Luca T1 - Fatigue limit estimation of welded joints under constant amplitude uniaxial loading adopting the cyclic R-curve analysis N2 - Most of the in-service failures of welded structures are due to fatigue damage occurring in the joints. Damage tolerant approaches based on the principles of Fracture Mechanics have been shown to play a key role in this framework, as the fatigue limit is defined by the non-propagating condition of multiple defects at the weld toe. The fatigue limit assessment can be performed using the cyclic R-curve analysis which consists in comparing the driving force of a crack propagating into a component, which depends on the geometry, material and external loads, with its resistance curve, i.e. the cyclic R-curve. The crack propagation occurs whenever the crack driving force is higher than the resistance to fatigue crack propagation, while the crack is arrested in the opposite case. Consequently, this suggests that the fatigue limit of a component is defined as that stress level at which the crack driving force curve is tangent to the crack resistance curve. In the present work, the cyclic R-curve analysis has been adopted for determining the fatigue limit of stress-relieved transverse non-load-carrying joints made of S355 structural steel and subjected to fatigue axial loadings. Experimental tests have been performed to evaluate the fatigue limit of the joints. The driving force, identified by the applied Stress Intensity Factor (SIF), has been evaluated by means of linear elastic finite element analysis taking advantage of the Peak Stress Method for its rapid estimation. Based on the experimental observations that the crack initiation and early crack growth phases in welded joints occur within the Heat Affected Zone (HAZ) the cyclic R-curve has been experimentally derived for both the base metal and HAZ material. T2 - European Conference on Fracture 2022 (ECF23) CY - Funchal, Portugal DA - 27.06.2022 KW - Welded Joints KW - Fatigue Limit KW - Cyclic R-curve PY - 2022 AN - OPUS4-55254 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro T1 - Fraucture mechanics-based probablistic structural integrity assessment for aero-engine turbine disk N2 - Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The aim of this work is to present part of a fracture mechanics-based probabilistic assessment procedure under development which aims at calculating the critical rotational speed of the turbine disk based on the numerical-analytical solutions and regulations for the failure probability. In particular, the rim-peeling failure mode is considered as case study. A semi-circular surface crack is modelled at the most stressed region at the diaphragm of a turbine disk. In order to design a lab representative specimen, beside the crack driving force, expressed in terms of J-integral, also the constraint to plastic deformation e.g., stress triaxiality, at the crack-tip must be similar for the same crack in the specimen and in the disk. The analytical solutions to calculate the crack driving force for the lab representative specimen are used for the Monte Carlo simulations, the result of which has been assessed in the form of a Failure Assessment Diagram (FAD). The results of the probabilistic structural integrity assessment show good agreement between Monte Carlo simulations and certification values for the disk in terms of expected failure mode and value of the critical speed. T2 - ICF15 - International Conference on Fracture CY - Atlanta, GA, USA DA - 12.06.2023 KW - Fracture Mechanics KW - Failure Assessment Diagram KW - Finite Element Analysis KW - Component Assessment PY - 2023 AN - OPUS4-57727 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro T1 - Probabilistic structural integrity assessment of welded joints N2 - The fatigue assessment of welded joints requires several input data, which can be subdivided into three categories: geometry, material and loading. The number of input data depends essentially on the complexity of the models employed and on the level of accuracy of the analysis. It is common practice to use safety factors in design to account for the scatter of the input parameters. Nevertheless, overly-conservative factors lead often to unrealistic estimations of fatigue life. This work presents a fracture mechanics-based model for the structural integrity assessment of welded joints under constant amplitude fatigue loading, in which the local geometry at the weld toe and the fatigue crack growth properties are considered statistically distributed. The approach is validated against a large number of experimental data. T2 - ICF15 - International Conference on Fracture CY - Atlanta, GA, USA DA - 12.06.2023 KW - Fatigue KW - Fracture Mechanics KW - Weldments KW - Short crack KW - Probabilistic Assessment PY - 2023 AN - OPUS4-57726 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro T1 - Progress in the determination of the fatigue propagation resistance in metals and its application to fatigue assessment N2 - This plenary lecture aims at showing the progress in the experimental determination of the fatigue propagation resistance in metals and its application to fatigue assessment. In particular, different new experimental techniques are introduced, which allow a better description of the crack propagation resistance from short to long crack regime. These data can be then applied in the fatigue assessment to predict the fatigue limit and the total life of metallic components. T2 - 5th Iberian Conference on Structural Integrity CY - Coimbra, Portugal DA - 30.03.2022 KW - Crack propagation resistance KW - Cyclic R-Curve KW - Fatigue assessment KW - Kitagawa-Takahashi diagram KW - S-N diagram PY - 2022 AN - OPUS4-54603 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Teske, Tanita T1 - Untersuchung des Potentials des Kaltgasspritzens für die Reparatur zyklisch belasteter Bauteile N2 - Das Kaltgasspritzen als Reparaturverfahren bietet die Möglichkeit den teuren Austausch beschädigter Bauteile in der Luft- und Raumfahrt zu vermeiden. In dieser Arbeit wurden das Potential an der Aluminiumlegierung AL6061-T6, unter Verwendung von Stickstoff als Prozessgas, untersucht. Mit Fokus auf das In-situ Kugelstrahlen, zur Verbesserung der mechanischen Eigenschaften, wurden quasi-statische Zugversuche und einachsige Zeitfestigkeitsversuche durchgeführt. Im Ergebnis zeigte sich die Verbesserung der Adhäsion zwischen Grundwerkstoff und aufgebrachten Material als entscheidendes Kriterium für eine erfolgreiche Anwendung. Zur Verbesserung der Adhäsion wurden die Substratoberflächen laserstrukturiert und der Einfluss mit Adhäsionsversuchen überprüft. T2 - 9. Tagung des DVM-Arbeitskreises Additiv gefertigte Bauteile und Strukturen CY - Stuttgart, Germany DA - 06.11.2024 KW - Kaltgasspritzen KW - Reparatur KW - Ermüdungsfestigkeit KW - Laserstrukturierung KW - Luft- und Raumfahrt PY - 2024 AN - OPUS4-63179 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kruse, Julius T1 - Anwendung der IBESS-Prozedur zur Berechnung der Schwingfestigkeit geschweißter bauteilähnlicher Proben mit künstlichen Defekten N2 - Im Rahmen eines Kooperationsprojekts mit der Schottel GmbH wurde eine bauteilnahe Probengeometrie entwickelt, mit der sich unter Verwendung einer einachsigen Prüfmaschine das Spannungstiefenprofil in dem unter überlagerter Biege- und Zugspannung beanspruchtem Querschnitt im Schweißnahtübergang des Bauteils reproduzieren ließ. Proben dieser Geometrie wurden vom Kooperationspartner im geschweißten bzw. geschweißten und spannungsarmgeglühten Zustand bereitgestellt. An der BAM wurden je Wärmebehandlungszustand mittels Senkerodieren zwei verschiedene künstliche Defektgeometrien im Schweißnahtübergang eingebracht. Anhand der Proben wurden experimentell für alle vier Probenzustände Wöhlerlinien für ein Spannungsverhältnis von R = 0,1 ermittelt. Zusätzlich wurde das u.a. an der BAM entwickelte IBESS-Verfahren angewandt, um die Wöhlerlinien analytisch zu bestimmen. Hierbei wurde eine sehr gute Übereinstimmung von Berechnung und Experiment erreicht, wobei die Berechnung zu einer leicht konservativen Lebensdauervorhersage führte. T2 - 56. DVM Tagung "Bruchmechanik und Bauteilsicherheit" CY - Kassel, Germany DA - 20.02.2024 KW - Bruchmechanik KW - Ermüdung KW - Schwingfestigkeit KW - Schweißverbindungen PY - 2024 AN - OPUS4-59781 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scacco, F. A1 - Zerbst, Uwe A1 - Meneghetti, G. A1 - Madia, Mauro T1 - Comparison between PSM and IBESS approaches for the fatigue life estimation of weldments N2 - In the framework of the fatigue assessment of welded components, several methods are available in design standards such as the nominal stress, hot-spot stress, notch stress and linear elastic fracture mechanics approaches. The present paper aims at comparing two advanced local approaches for the fatigue strength assessment of different welded joints made of steel. The first one is IBESS which is based on short crack fracture mechanics. The second one is the PSM which instead involves the strain energy density approach. Both methods will be briefly presented, and the fatigue life prediction results discussed. The results obtained for the joint geometries considered in this work show advantages and drawbacks of the approaches, which are thoroughly analysed as well. KW - Fatigue KW - Welded joints KW - FAT class KW - IBESS KW - Peak stress method (PSM) KW - Finite element (FE) PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-545139 DO - https://doi.org/10.1007/s40194-022-01284-7 SP - 1 EP - 23 PB - Springer AN - OPUS4-54513 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Werner, Tiago T1 - Estimation of the Kitagawa-Takahashi diagram by cyclic R curve analysis N2 - The Kitagawa-Takahashi (KT) diagram is a proven concept for describing the fatigue limit in presence of a defect or crack. It can be determined empirically with great experimental effort. It can also be estimated by means of the El Haddad relationship if the endurance limit and the long fatigue crack propagation threshold are available in reasonable accuracy. A third option is the determination using the cyclic R-curve, which describes the dependency of the fatigue crack propagation threshold on the crack growth at the short crack propagation stage. This can be experimentally determined using a closure-free initial pre-crack. It can then be applied to the determination of crack arrest for a given applied load and a given defect or crack size. Compared to the other two methods mentioned above, this option has considerable advantages: It can be applied to any component and any stress ratio. It allows the treatment of multiple cracks and provides estimations of the S-N curve in the finite life regime as well as at the endurance limit. Compared to the empirical determination of the KT diagram, the experimental effort is significantly lower and compared to the El Haddad approach it avoids problems such as the use of non-conservative long fatigue crack propagation thresholds (when the conventional load reduction method is applied to materials prone to corrosion) and the mathematical predetermination of the curve shape. The work introduces the method and provides a critical discussion as well as quantitative comparison between the different methods. T2 - FATIGUE DESIGN 2021 CY - Online meeting DA - 17.11.2021 KW - Fatigue life KW - Endurance limit KW - Kitagawa-Takahashi diagram KW - Cyclic R-curve PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-544931 DO - https://doi.org/10.1016/j.prostr.2022.03.032 SN - 2452-3216 VL - 38 SP - 309 EP - 316 PB - Elsevier B.V. AN - OPUS4-54493 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönherr, J. A. A1 - Duarte, Larissa A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Geilen, M. B. A1 - Klein, M. A1 - Oechsner, M. T1 - Robust determination of fatigue crack propagation thresholds from crack growth data N2 - The robust determination of the threshold against fatigue crack propagation DKth is of paramount importance in fracture mechanics based fatigue assessment procedures. The standards ASTM E647 and ISO 12108 introduce operational definitions of DKth based on the crack propagation rate da/dN and suggest linear fits of logarithmic DK– da/dN test data to calculate DKth. Since these fits typically suffer from a poor representation of the actual curvature of the crack propagation curve, a method for evaluating DKth using a nonlinear function is proposed. It is shown that the proposed method reduces the artificial conservativeness induced by the evaluation method as well as the susceptibility to scatter in test data and the influence of test data density. KW - Fatigue crack propagation threshold KW - ISO 12108 KW - ASTM E647 KW - Data evaluation methods KW - Experimental determination PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-552153 DO - https://doi.org/10.3390/ma15144737 SN - 1996-1944 VL - 15 IS - 14 SP - 1 EP - 21 PB - MDPI CY - Basel AN - OPUS4-55215 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Analytische Prozedur zur Berechnung der Ermüdungslebensdauer basierend auf effektiven Rissfortschrittsdaten und zyklischer R-Kurve N2 - Bruchmechanik-basierende Methoden können für die Ermüdungsbewertung von mechanischen Bauteilen angewendet werden, die Defekte oder Risse enthalten und zyklischen Belastungen ausgesetzt sind. Die Kenntnis des Risswachstumsverhaltens für kurze und lange Risse ermöglicht die Bestimmung sowohl endlicher als auch unendlicher Lebensdauer. Ein erstes Problem ergibt sich jedoch aus der empirischen Bestimmung von Ermüdungswerkstoffkennwerten, die je nach Prüfbedingungen, z. B. Prüfmethode, Frequenz und Spannungsverhältnis R, variieren. Dies ist auf die Rissschließeffekte und weitere Umgebungsphänomene zurückzuführen, die das Rissfortschrittsverhalten beeinflussen. Ein zweites Problem ist das Fehlen von Standardversuchsverfahren zur Bestimmung des Schwellenwerts gegen Ermüdungsrissausbreitung ΔKth in Abhängigkeit von der Rissausbreitung. Dies ist problematisch, da ΔKth mit der Zunahme der Rissschließeffekte im Kurzrissbereich zunimmt und seine ungenaue experimentelle Bestimmung zu großen Abweichungen bei der Bewertung und, was noch kritischer ist, zu nicht konservativen Vorhersagen führt. Mit dem Ziel, zuverlässigere und sicherere Bewertungsverfahren bereitzustellen, wird in dieser Arbeit eine Methode vorgeschlagen, die auf effektiven Risswachstumsdaten basiert, die bei hohen Spannungsverhältnissen (R ≈ 0,8) ermittelt wurden. Zur Beschreibung der Entwicklung der Rissschließeffekte wird ein Kurzrissmodell auf der Grundlage von zyklischen R-Kurven und CPLR-Daten verwendet. Die analytischen Vorhersagen werden mit experimentellen Daten verglichen, die zur Validierung des Verfahrens durchgeführt wurden, und die daraus entstandenen Unterschiede werden diskutiert. Übersetzt mit DeepL.com (kostenlose Version) T2 - BMDK-Seminar SS24 CY - Magdeburg, Germany DA - 10.04.2024 KW - Schwellenwert gegen Ermüdungsrissausbreitung KW - Rissschließeffekte KW - Ermüdungslebensdauer KW - Zyklische R-Kurve PY - 2024 AN - OPUS4-59876 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Duarte, Larissa A1 - Madia, Mauro A1 - Zerbst, Uwe T1 - The effect of the environmental conditions on the threshold against fatigue crack propagation N2 - The threshold against fatigue crack propagation (ΔKth) is a crucial parameter for the damage tolerance assessment of engineering components subjected to cyclic loading and it is composed by two distinct components, one intrinsic, dependent on the elastic material properties and the lattice type, and one extrinsic, related to the occurrence of crack closure effects. An important issue is that several factors can influence ΔKth and, in general, the fatigue crack propagation behavior. In this work, the influence of the experimental procedure, air humidity, stress ratio and test frequency on da/dN-ΔK data has been investigated. Results are discussed with their potential causes and consequences on the calculations of the residual lifetime. KW - Fatigue crack propagation threshold KW - Crack closure effect KW - Experimental procedure KW - Environmental conditions PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-544905 DO - https://doi.org/10.1016/j.prostr.2022.03.030 VL - 38 SP - 292 EP - 299 PB - Elsevier B.V. AN - OPUS4-54490 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro T1 - Determination of the Kitagawa-Takahashi diagram for the EA4T railway axle steel by means of the cyclic R-curve method N2 - The Kitagawa-Takahashi (KT) diagram is a well-established tool in the fatigue community for the prediction of the fatigue limit of metallic materials in presence of defects. Nevertheless, its determination is associated with a large number of fatigue tests carried out on specimens with artificial defects (notches) to describe the fatigue limit-defect size relationship in the short crack regime. The preparation of the specimens and the execution of the tests is time expensive. Therefore, few phenomenological models have been introduced in the past to provide a first approximation of the KT diagram based solely on the fatigue limit for smooth specimen and the fatigue crack propagation threshold for long cracks. Despite the use of such models is widely spread, these suffer from problems related to the uncertainties of the material parameters. Furthermore, the mechanics of short cracks, which is the physical mechanism behind the concept of the fatigue limit, is not considered. This work discusses the advantages and drawbacks of using short fatigue crack propagation models for predicting the fatigue limit of flawed metallic materials. The KT diagrams for a EA4T railway axle steel in as-received and full-hardened condition are approximated by means of the cyclic R-curve method. T2 - 13th International Fatigue Congress CY - Hiroshima, Japan DA - 06.11.2023 KW - Fatigue limit KW - Crack propagation KW - Short crack KW - Cyclic R-curve KW - EA4T railway axle steel PY - 2023 AN - OPUS4-58867 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Fatigue assessment procedure based on effective crack propagation data and cyclic R-curve N2 - Fracture mechanics-based methods can be applied to the fatigue assessment of mechanical components containing defects or cracks subjected to cyclic loading. The knowledge of the crack growth behavior for short and long cracks enables the determination of both finite and infinite life regimes. Nevertheless, a first problem arises from the empirical determination of the fatigue data, which vary according to the test conditions, e.g., the test method, frequency and the stress ratio R. This is due to crack closure and further environmental phenomena affecting crack propagation behavior. A second issue regards the lack of standard experimental procedures for the determination of the fatigue crack propagation threshold ΔKth dependency on the crack size. This is problematic, since ΔKth increases with the build-up of the closure effects in the short crack regime and its inaccurate experimental determination leads to large deviations in the assessment and, even more critical, to non-conservative predictions. Aiming at providing more reliable and safer assessment procedures, the present work proposes a method based on effective crack growth data obtained at high stress ratios (R ≈ 0.8). A short-crack model based on the cyclic R-curve and CPLR data is employed for describing the development of the closure effects. The predictions are compared to established methods and validated by experimental tests. T2 - Fatigue 2022+1 CY - Hiroshima, Japan DA - 06.11.2023 KW - Component assessment KW - Fatigue crack propagation KW - Fatigue threshold KW - Crack closure KW - Cyclic R-curve PY - 2023 AN - OPUS4-58842 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa A1 - Zerbst, Uwe A1 - Madia, Mauro T1 - Vergleichende Untersuchungen zum intrinsischen Schwellenwert der da/dN-ΔK-Kurve N2 - Für die Bestimmung der Restlebensdauer zyklisch beanspruchter Bauteile kommt dem Schwellenwert für Ermüdungsrissausbreitung, Δ𝐾𝑡ℎ, und dem sich anschließenden Schwellenwertbereich der 𝑑𝑎𝑑𝑁⁄−Δ𝐾-Kurve große Bedeutung zu. Dem stehen Unsicherheiten bei der Bestimmung und Analyse gegenüber. Der Aufsatz befasst sich mit der Ermittlung des sogenannten intrinsischen Schwellenwerts, der als robuster Eingangsparameter für eine „rissschließfreie“ Analyse der Restlebensdauer von entscheidender Bedeutung ist. T2 - 53. Tagung des DVM-Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Online meeting DA - 18.02.2021 KW - Schadenstolerante Bauteilauslegung, Restlebensdauer, intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung PY - 2021 SN - 2366-4797 SP - 211 EP - 220 PB - Deutscher Verband für Materialforschung und -prüfung e.V. (DVM) CY - Berlin AN - OPUS4-52704 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa A1 - Zerbst, Uwe A1 - Madia, Mauro T1 - Der Schwellenwert der da/dN-∆K-Kurve als Auslegungskriterium für die Bauteilbewertung N2 - Für die Bestimmung der Restlebensdauer zyklisch beanspruchter Bauteile kommt dem Schwellenwert für Ermüdungsrissausbreitung ∆Kth und dem sich anschließenden Schwellenwertbereich der da/dN-∆K-Kurve große Bedeutung zu. Dem stehen Unsicherheiten bei der Bestimmung und Analyse gegenüber. Der Aufsatz befasst sich mit der Ermittlung des sogenannten intrinsischen Schwellenwerts, der als robuster Eingangsparameter für eine „rissschließfreie“ Analyse der Restlebensdauer von entscheidender Bedeutung ist. T2 - Tagung Werkstoffprüfung 2020 CY - Online meeting DA - 03.12.2020 KW - Schadenstolerante Bauteilauslegung, KW - Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung KW - Restlebensdauer PY - 2020 DO - https://doi.org/10.48447/WP-2020-025 SP - 1 EP - 8 AN - OPUS4-52788 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vecchiato, L. A1 - Madia, Mauro A1 - Meneghetti, G. T1 - Extension of the peak stress method to estimate the fatigue limit of welded joints by means of the cyclic R-curve method N2 - A new simplified and effective method has been formalised to estimate the Constant Amplitude Fatigue Limit (CAFL) of stress-relieved steel welded joints subjected to uniaxial push–pull loading and failing from the weld toe. Starting from the sharp V-notch assumption of the NSIF approach and the cyclic R-curve of the material in the heat affected zone, the proposed method identifies the CAFL as threshold level of the local stress field at the V-notched weld toe in the uncracked configuration. Such threshold stress field assures the crack arrest at the V-notched weld toe, according to the cyclic R-curve analysis. The method has been validated against experimental results and proved effective for a straightforward assessment of the CAFL of welded joints, as the stable crack propagation analysis of classical fracture mechanics approaches can be avoided. KW - Cyclic R-curve KW - Welded joint KW - Fatigue limit KW - Peak stress method KW - Finite element analysis PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-581059 DO - https://doi.org/10.1016/j.tafmec.2023.104039 SN - 0167-8442 VL - 127 SP - 1 EP - 19 PB - Elsevier AN - OPUS4-58105 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhu, Jiangchao A1 - Madia, Mauro A1 - Schurig, Michael A1 - Kruse, Julius A1 - Conrad, Fabian A1 - Schlums, Hartmut A1 - Kontermann, Christian A1 - Zerbst, Uwe T1 - On the use of representative specimens for the structural integrity assessment of safety-relevant rotating components N2 - Safety-relevant components, for which a failure in service could have catastrophic consequences, are usually designed for extremely low probability of failure and they are subjected to stringent part qualification procedures according to guidelines set by regulatory agencies. Manufacturers are often forced to perform tests on full scale or scaled components to ensure the structural integrity under defined loading conditions, which usually implies a huge experimental and financial effort. Therefore, companies try to develop new strategies such as digital twins, which allow to massively reduce costs, without compromising safety. This work presents a new quasi-static testing and assessment concept, the main idea of which is to replace, or at least reduce, the experimental testing on components by testing specimens representative of the component. Fracture mechanics specimens have been designed iteratively by numerical simulations to match the stress state at the crack-tip of the maximum permissible defect defined by regulatory agencies for the component. Potentially, the major benefit of the proposed approach is that the tests can be performed on conventional laboratory testing machines. The effectiveness of the methodology is demonstrated in case of the structural integrity assessment of a Ni-base superalloy aero-engine turbine disk at overspeed conditions. KW - Structural integrity KW - Turbine disk KW - Burst KW - Fracture mechanics KW - Representative specimens KW - Quasi-static testing PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-624208 DO - https://doi.org/10.1016/j.engfracmech.2024.110710 SN - 0013-7944 VL - 314 SP - 1 EP - 23 PB - Elsevier Ltd. AN - OPUS4-62420 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Damage tolerant design of metallic AM parts N2 - Additive Manufacturing (AM) opens new possibilities in the design of metallic components, including very complex geometries (e.g. structures optimized for certain loads), optimization of materials (e.g. gradient materials) and cost-effective manufacturing of spare parts. In the recent years, it has been used for the first safety-relevant parts, but the consideration of cyclic mechanical behavior in AM is still at the very beginning. The reason for this is the complexity of mechanical material properties, i.e. inhomogeneity, anisotropy and a large number of defects frequently textured and characterized by large scattering in size. Additionally, high surface roughness and residual stresses with complex distributions are typical of AM. Due to these reasons, the transferability of experimentally determined properties from specimens to components is a challenge. This presentation provides an overview of the questions concerning the application of AM to safety-relevant components. Possible strategies for the fatigue design of such components are presented. Besides the Kitagawa-Takahashi-diagram method and the cyclic R-curve analysis as approaches for damage-tolerant design, the identification of critical locations, the problem of representative material properties and the handling of residual stresses are addressed. T2 - 4th international symposium on Fatigue Design and Material Defects CY - Online meeting DA - 26.05.2020 KW - Additive Manufacturing KW - Cyclic R-Curve KW - Component assessment PY - 2020 AN - OPUS4-50938 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro T1 - Influence of defects on the fatigue strength of parts repaired by cold spray N2 - Cold spray repair is a promising and cost-saving alternative to replacing worn parts. Depositing of materials into machined damage volumes in decent quality can restore the performance of refurbished parts and extend their working life. Furthermore, repair counts as resource-efficient and green process in a world targeting at decarbonization of many industrial sectors. Despite the advantages, cold spray repair still suffers from major limitations which prevent its application in safety relevant parts. The main factors influencing the structural integrity concern the adhesion strength, inherent non-bonded internal interfaces, the reduced ductility by work hardening during the manufacturing process, and the presence of residual stresses. This work presents the results of the collaborative project CORE devoted to the development of automatized repair of aerospace parts by cold spray. The investigations considered the aluminum alloy Al6061-T6 which combines medium-high strength, good workability, and high corrosion resistance. Quasi-static tensile tests, high cycle fatigue and fatigue crack propagation tests were performed to compare the performance of base and repaired materials. These were complemented by fractographic and microstructural investigations. T2 - 5th International Symposium on Fatigue Design and Material Defects CY - Trento, Italy DA - 14.05.2025 KW - Cold Spray KW - Component Repair KW - Fatigue Strength KW - Defects KW - Surface Treatment PY - 2025 AN - OPUS4-63146 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago A1 - Teske, Tanita A1 - Hilgenberg, Kai A1 - Mauro, Madia A1 - Nielsen, S. A1 - Gärtner, F. A1 - Klassen, T. T1 - Untersuchung des Potenzials von Kaltgasspritzen für die Reparatur zyklisch belasteter Bauteile T1 - Investigation on the capability of cold-spray for repair of cyclically loaded components N2 - Die Reparatur mittels Kaltgasspritzen ist eine vielversprechende Alternative zum teuren Austausch fehlerbehafteter Bauteile in der Luft- und Raumfahrt. Im Rahmen dieser Arbeit wurde das Potential des Verfahrens an der hochfesten Aluminiumlegierungen Al6061-T6 unter Anwendung von Stickstoff als kostengünstiges Prozessgas untersucht. Es wurden quasi-statische Zugversuche und einachsige Zeitfestigkeitsversuche mit besonderem Fokus auf das in-situ Kugelstrahlen zur Verbesserung der mechanischen Eigenschaften durchgeführt. Im Ergebnis wurde die Verbesserung der Adhäsion zwischen Substrat und aufgebautem Werkstoff als entscheidendes Kriterium für eine Anwendbarkeit ermittelt. Die Laserstrukturierung von Substratoberflächen ist hierfür vielversprechend und wurde im Rahmen der Arbeit mittels Adhäsionsversuchen untersucht. N2 - Repair by cold-spray is a promising alternative to the costly replacement of flawed components in aerospace applications. In the present work this process was investigated on the high-strength aluminum alloy Al6061-T6. For the cold-spray process, inexpensive Nitrogen was used as process-gas. Quasi-static tensile and highcycle- fatigue tests (HCF) were performed, focusing on in-situ shot peening to improve the mechanical properties of the repaired part. An improved adhesion between substrate and built-up material was identified as a key-factor for the applicability of the process. Under this respect laser-structuring of the substrate surface was applied and its effect on the mechanical performance of the restored samples were examined by adhesion tests. T2 - 9. Tagung des DVM-Arbeitskreises Additiv gefertigte Bauteile und Strukturen CY - Stuttgart, Germany DA - 06.11.2024 KW - Kaltgasspritzen KW - cold-spray KW - Reparatur KW - Repair KW - Ermüdungsfestigkeit KW - Fatigue KW - Luft- und Raumfahrt KW - Aerospace KW - Substratvorbehandlung KW - Substrate pre-treatment PY - 2024 DO - https://doi.org/10.48447/ADD-2024-BB VL - 409 SP - 67 EP - 79 AN - OPUS4-63182 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bergant, M. A1 - Werner, Tiago A1 - Madia, Mauro A1 - Yawny, A. A1 - Zerbst, Uwe T1 - Short crack propagation analysis and fatigue strength assessment of additively manufactured materials: An application to AISI 316L N2 - This paper presents the application of short crack propagation models based on the cyclic R-curve for assessing the fatigue strength of additively manufactured (AM) materials containing fabrication defects. Chapetti’s and IBESS models were implemented in combination with Murakami’s √area parameter, considering recently published data on laser powder bed fusion processed AISI 316L stainless steels. Estimated S-N curves and Kitagawa-Takahashi diagrams predict fairly well the experimental data, especially the origin of the failure from internal or surface defects. These results provide an indication that the methods based on the cyclic R-curve constitute suitable tools for fatigue behavior assessment of AM materials. KW - AM 316L stainless steel KW - Cyclic R-curve KW - Chapetti’s and IBESS model KW - S-N curve KW - Kitagawa-Takahashi diagram PY - 2021 DO - https://doi.org/10.1016/j.ijfatigue.2021.106396 VL - 151 PB - Elsevier Ltd. AN - OPUS4-53082 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schork, B. A1 - Zerbst, Uwe A1 - Kiyak, Yusuf A1 - Kaffenberger, M. A1 - Madia, Mauro A1 - Oechsner, M. T1 - Effect of the parameters of weld toe geometry on the FAT class as obtained by means of fracture mechanics-based simulations N2 - The fracture mechanics-based IBESS approach is applied to the determination of FAT classes of butt welds with crack Initiation along the weld toe. The aim is an investigation of the effect of the geometrical parameters toe radius, flank angle, reinforcement and secondary notches such as roughness or undercuts. The influence of these parameters is discussed both individually and in combination; however, excluding statistical distributions of them and the material data. The results, when compared with conventional FAT classes for butt welds, are encouraging with respect to a potential contribution of IBESS to the discussion of more advanced quality criteria for welds. To that purpose, demands for further research are proposed. KW - Fracture mechanics KW - Weld toe geometry KW - Fatigue crack initiation KW - FAT class approach PY - 2020 DO - https://doi.org/10.1007/s40194-020-00874-7 IS - 64 SP - 925 EP - 936 PB - Springer AN - OPUS4-53079 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa A1 - Madia, Mauro A1 - Zerbst, Uwe T1 - The use of effective fatigue crack propagation data obtained at closure-free conditions for component assessment N2 - The knowledge of fatigue crack propagation data in terms of their effective values is important for a conservative and safe life assessment of components subjected to cyclic loading. To overcome issues related to the precise consideration of the crack-closure effects on experimental data obtained at small R ratios, closure-free data have been obtained at R ≈ 0.8 by different experimental procedures. The statistical analysis of the intrinsic fatigue crack propagation threshold obtained experimentally has shown a small data scatter and good agreement between procedures. When compared with effective values obtained from analytical corrections of closure-affected data, the data obtained at R ≈ 0.8 should lead to a conservative life estimation. T2 - 43rd International Conference on Materials Mechanics CY - Sani, Greece DA - 05.06.2022 KW - Component assessment KW - Effective crack propagation data KW - Experimental procedure KW - Crack-closure PY - 2022 SP - 104 EP - 108 AN - OPUS4-56851 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhu, J. A1 - Madia, Mauro A1 - Schurig, M. A1 - Kruse, Julius A1 - Conrad, F. A1 - Schlums, H. A1 - Kontermann, C. A1 - Zerbst, Uwe T1 - Anwendung von repräsentativen Proben zur Bewertung der Strukturintegrität von sicherheitsrelevanten Komponenten N2 - Sicherheitsrelevante Bauteile, bei denen ein Versagen im Betrieb katastrophale Folgen haben könnte, sind in der Regel für eine sehr geringe Ausfallwahrscheinlichkeit ausgelegt und unterliegen strengen Qualifizierungsverfahren gemäß den von den Aufsichtsbehörden festgelegten Richtlinien. Die Hersteller sind oft gezwungen, Tests an realen oder skalierten Komponenten durchzuführen, um die Strukturintegrität unter definierten Belastungsbedingungen sicherzustellen, die in der Regel strenger sind als die im Betrieb zu erwartenden. Dies ist in der Regel mit einem enormen experimentellen und finanziellen Aufwand verbunden. Daher versuchen die Unternehmen, neue Strategien wie digitale Zwillinge zu entwickeln, mit denen die Kosten massiv gesenkt werden können, ohne die Sicherheit zu beeinträchtigen. In dieser Arbeit wird ein neues quasistatisches Prüf- und Bewertungskonzept vorgestellt, dessen Hauptidee darin besteht, die experimentelle Prüfung von Bauteilen durch die Prüfung von für das Bauteil repräsentativen Proben zu ersetzen oder zumindest zu reduzieren. Der größte Vorteil des vorgeschlagenen Konzepts besteht darin, dass die Versuche auf Laborprüfmaschinen durchgeführt werden können. Die Wirksamkeit der Methodik wird anhand der Bewertung der Strukturintegrität einer Turbinenscheibe aus einer Ni-Basis-Superlegierung für Flugzeugtriebwerke bei Überdrehzahl demonstriert. T2 - 57. Tagung des DVM-Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Köln, Germany DA - 18.02.2025 KW - Strukturintegrität KW - Bruchmechanik KW - Turbinenscheibe KW - Repräsentative Proben PY - 2025 DO - https://doi.org/10.48447/BR-2025-536 SP - 231 EP - 240 PB - DVM CY - Berlin AN - OPUS4-62602 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kanna, Naveen A1 - Bär, Jürgen A1 - Duarte, Larissa A1 - Madia, Mauro ED - Ricoeur, Andreas T1 - Ermittlung von Kitagawa-Takahashi-Diagrammen mittels Gleichstrompotentialsondenmessungen N2 - Das Kitagawa-Takahashi Diagramm ist ein wichtiges Werkzeug zur Beschreibung der ausgeprägten Langzeitfestigkeit fehlerbehafteter Bauteile. Insbesondere im technisch relevanten Übergangsbereich unterscheiden sich jedoch die verwendeten Modelle. Daher ist für eine sichere Aussage eine experimentelle Absicherung in diesem Bereich zwingend notwendig. In dieser Arbeit wird eine Methode vorgestellt, die eine einfache und schnelle Absicherung des Verlaufs im Übergangsbereich erlaubt. Hierzu werden in Flachproben mittels eines Gravierlasers scharfe Kerben mit einer definierten Breite und Tiefe eingebracht. Die so präparierten Proben werden mit blockweise steigender Last bis zum Bruch ermüdet. Die Erkennung von Anrissen erfolgt mittels einer Gleichstrom-Potentialsonde mit der auch die Länge des Lastblocks gesteuert wird. T2 - 57. Tagung des DVM-Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Cologne, Germany DA - 18.02.2025 KW - Ausgeprägte Langzeitfestigkeit KW - Materialdefekte KW - KT-Diagramm KW - Gleichstrom-Potentialsonde PY - 2025 DO - https://doi.org/10.48447/BR-2025-513 VL - 257 SP - 105 EP - 112 PB - Deutscher Verband für Materialforschung und -prüfung e.V. CY - Berlin, Deutschland AN - OPUS4-62604 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hadley, I. A1 - Zerbst, Uwe A1 - Coules, H. A1 - James, P. A1 - Sharples, J. A1 - Bath, S. A1 - Larrosa, N. T1 - Knowledge gaps in fitness-for-service assessment procedures; summary of the 2nd ‘mind the gap’ workshop N2 - In 2015, the University of Manchester hosted a workshop (‘Mind the Gap’) aimed at identifying gaps in a number of structural integrity fitness-for-service procedures, including R5, R6, BS 7910 and API/ASME. The findings were subsequently summarised in a journal paper and shared with the relevant stakeholders. A second workshop, this time hosted by the University of Bristol in 2017, was intended to build on the findings of the earlier event, identifying which gaps had been filled, which remain and whether new ones have been identified in the meantime. ‘Mind the Gap 2’ was wide-ranging, including consideration of failure by fracture, fatigue crack growth, hightemperature creep and environmentally assisted crack growth, along with the use of innovative techniques to follow the progress of crack growth from the atomic to the macroscopic scale. A summary of the whole event is thus outside the scope of a single paper, so here we concentrate mainly on advances in fracture assessment, on the interface between inspection and ECA, and on how developments are being incorporated into structural integrity procedures. There is a particular emphasis on the energy transition in the UK, where the planned energy mix will include both nuclear power and offshore wind. KW - Flaw assessment procedures KW - Non-sharp defects KW - Flaw interaction KW - Codes and standards KW - Nuclear reactor systems PY - 2023 DO - https://doi.org/10.1016/j.ijpvp.2022.104883 SN - 0308-0161 VL - 202 SP - 1 EP - 14 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-56846 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hensel, J. A1 - Kromm, Arne A1 - Nitschke-Pagel, T. A1 - Dixneit, Jonny A1 - Dilger, K. T1 - Capability of martensitic low transformation temperature welding consumables for increasing the fatigue strength of high strength steel joints N2 - The use of low transformation temperature (LTT) filler materials represents a smart approach for increasing the fatigue strength of welded high strength steel structures apart from the usual procedures of post weld treatment. The main mechanism is based on the effect of the low start temperature of martensite formation on the stress already present during welding. Thus, compressive residual stress formed due to constrained volume expansion in connection with phase transformation become highly effective. Furthermore, the weld metal has a high hardness that can delay the formation of fatigue cracks but also leads to low toughness. Fundamental investigations on the weldability of an LTT filler material are presented in this work, including the characterization of the weld microstructure, its hardness, phase transformation temperature and mechanical properties. Special attention was applied to avoid imperfections in order to ensure a high weld quality for subsequent fatigue testing. Fatigue tests were conducted on the welded joints of the base materials S355J2 and S960QL using conventional filler materials as a comparison to the LTT filler. Butt joints were used with a variation in the weld type (DY-weld and V-weld). In addition, a component-like specimen (longitudinal stiffener) was investigated where the LTT filler material was applied as an additional layer. The joints were characterized with respect to residual stress, its stability during cyclic loading and microstructure. The results show that the application of LTT consumables leads to a significant increase in fatigue strength when basic design guidelines are followed. This enables a benefit from the lightweight design potential of high-strength steel grades. KW - Low transformation temperature KW - Welding KW - Fatigue strength KW - Residual stress PY - 2020 DO - https://doi.org/10.3139/120.111562 VL - 62 IS - 9 SP - 891 EP - 899 PB - Carl Hanser Verlag AN - OPUS4-51180 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sonego, M. A1 - Madia, Mauro A1 - Eder, M. A1 - Fleck, C. A1 - Pessan, L. A. T1 - Microstructural features influencing the mechanical performance of the Brazil nut (Bertholletia excelsa) mesocarp N2 - Brazil nut (Bertholletia excelsa) fruits are capable of resisting high mechanical forces when released from trees as tall as 50 m, as well as during animal dispersal by sharp-teethed rodents. Thick mesocarp plays a crucial part in seed protection. We investigated the role of microstructure and how sclereids, fibers, and voids affect nutshell performance using compression, tensile and fracture toughness tests. Fractured specimens were analyzed through scanning electron microscopy (SEM) and microtomography (microCT). Mesocarp showed high deformability (strain at max. stress of ~30%) under compression loading, a critical tensile strength of ~24.9 MPa, a Weibull modulus of ~3, and an elastic modulus of ~2 GPa in the tensile test. The fracture toughness, estimated through the work of fracture of SENB tests, reached ~2 kJ/m2. The thick and strong walls of mesocarp cells, with a weaker boundary between them (compound middle lamella), promote a tortuous intercellular crack path. Several toughening mechanisms, such as crack deflection, breaking of fiber bundles, fiber pullout and bridging as well as crack branching, occur depending on how fiber bundles and voids are oriented. KW - Toughening mechanisms KW - Brazil nut Mesocarp KW - Microstructure KW - Mechanical properties PY - 2021 DO - https://doi.org/10.1016/j.jmbbm.2020.104306 VL - 116 SP - 104306 PB - Elsevier Ltd. AN - OPUS4-52081 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pourheidar, A. A1 - Patriarca, L. A1 - Madia, Mauro A1 - Werner, Tiago A1 - Beretta, S. T1 - Progress in the measurement of the cyclic R-curve and its application to fatigue assessment N2 - The cyclic R-curve describes the resistance of a material to fatigue crack propagation fromthe short to the long crack regimes and it is therefore an essential ingredient in any fracturemechanics-based fatigue assessment procedure. This work presents different testing proceduresemployed in the experimental determination of the cyclic R-curve, especially focusing onthe comparison with long fatigue crack propagation thresholds obtained by means of thecompression precracking load reduction (CPLR) procedure. The tests were performed on theEA4T steel considering different stress ratios. The results show a good reproducibility of thecyclic R-curves at every stress ratio and for any testing procedure. In addition, the cyclicR-curves were used in a fracture mechanics-based assessment to predict the fatigue limits ofspecimens containing micro-notches. KW - Cyclic R-curve KW - Fatigue limit KW - Fatigue propagation threshold KW - EA4T steel KW - Digital image correlation PY - 2022 DO - https://doi.org/10.1016/j.engfracmech.2021.108122 SN - 0013-7944 VL - 260 SP - 1 EP - 17 PB - Elsevier CY - Kidlington AN - OPUS4-54208 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Duarte, Larissa A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Schönherr, J. A. A1 - Geilen, M. B. A1 - Klein, M. A1 - Oechsner, M. T1 - Recent developments in the determination of fatigue crack propagation thresholds N2 - The impact of crack closure and environmental effects on the experimental determination of the fatigue crack propagation threshold is a major problem for the assessment of cyclically loaded components, especially at low stress ratios 𝑅. In this work, the influence of the experimental procedure and air humidity on d𝑎∕d𝑁 − 𝛥𝐾 data at different 𝑅 is discussed. Unlike the results at 𝑅 = −1, the threshold values obtained at 𝑅 ≈ 0.8, i.e. under negligible crack closure levels, show a very small scatter band regardless of the variation of the test parameters and environmental conditions. KW - Fatigue crack propagation threshold KW - Component assessment KW - Crack closure KW - Environmental effects KW - Testing parameters PY - 2022 DO - https://doi.org/10.1016/j.ijfatigue.2022.107131 SN - 0142-1123 VL - 164 SP - 1 EP - 15 PB - Elsevier Ltd. AN - OPUS4-55403 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Application of the cyclic R-curve analysis to determine the Kitagawa-Takahashi Diagram N2 - The fatigue limit of metallic materials corresponds to the maximum stress below which all microcracks that were originally able to grow still arrest. In technical alloys, microcracks are normally initiated at material defects. As a result, the fatigue limit of these materials is a function of the defect size. The Kitagawa-Takahashi Diagram (KT-diagram) provides a useful description of this dependency. However, the established methods for its determination are associated with great uncertainties, especially in the technically interesting region corresponding to the short crack regime. In addition, the effect of crack closure and the influence of local stresses are not considered. For this reason, short crack models offer a better alternative for estimating KT-diagrams. In this work, a methodology is presented that incorporates the determination of the fatigue limit based on crack arrest (cyclic R-curve analysis). The crack driving force is determined by FE simulations, while the increase in material resistance with cyclic crack propagation in the region of physically short cracks is described experimentally by the cyclic R-curve. To validate the procedure, fatigue limit tests based on the staircase method are carried out on smooth and notched specimens with 3 different notch sizes. Furthermore, tests are carried out on a low-alloyed steel with two different heat treatments for considering different strengths. The experimental results are compared with the simulations and the possible differences are discussed. T2 - 5th International Symposium on Fatigue Design and Material Defects CY - Trento, Italy DA - 14.05.2025 KW - Fatigue limit KW - Material defects KW - Kitagawa-Takahashi Diagram KW - Cyclic R-curve analysis PY - 2025 AN - OPUS4-63144 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bär, Jürgen 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 curve is necessary. However, the standardized stair-case 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. 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 to produce 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 a low experimental effort and time consumption. T2 - 5th International Symposium on Fatigue Design and Material Defects CY - Trento, Italy DA - 14.05.2025 KW - Fatigue limit KW - Material defects KW - Kitagawa-Takahashi Diagram KW - DC Potential Drop PY - 2025 AN - OPUS4-63145 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Duarte, Larissa A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Schönherr, J. A. T1 - Ermittlung des intrinsischen Schwellenwerts und dessen Validierung als Werkstoffparameter N2 - Die Anwendung bruchmechanischer Methoden zur schadenstoleranten Bauteilauslegung ist für zyklische Lasten im Bereich der Paris-Geraden Stand der Technik. Technisch relevant sind jedoch häufig geringere Lasten im Schwellenwertbereich der d𝑎/d𝑁-Δ𝐾-Kurve. Aufgrund des großen Einflusses von Rissschließeffekten ist dessen Bestimmung jedoch nicht nur aufwändig, sondern auch potenziell fehlerbehaftet. Die Bauteilauslegung erfolgt zweckmäßigerweise auf der Basis effektiver, d. h. rissschließkorrigierter Rissfortschrittsdaten. Von großer Bedeutung ist auch der intrinsische Schwellenwert, unterhalb dessen keine Risserweiterung mehr eintritt. In diesem Forschungsprojekt erfolgte eine Untersuchung des Einflusses verschiedener Prüfverfahren und Umgebungsbedingungen auf die Ermittlung des Schwellenwerts gegen Ermüdungsrissausbreitung Δ𝐾th. Es wurden statistisch abgesicherte Empfehlungen zur experimentellen Ermittlung des intrinsischen Schwellenwerts Δ𝐾th,eff abgeleitet. Dieser dient auch als Eingangsparameter einer weiterentwickelten Prozedur zur Bauteilauslegung auf der Basis bei einem Lastverhältnis von 𝑅 ≈ 0,8 ermittelter, effektiver, Rissfortschrittsdaten. Es zeigte sich, dass die bei einem Lastverhältnis von 𝑅 ≈ 0,8 in Laborluft bei höherer Prüffrequenzen (≥90 Hz) ermittelten Schwellenwerte eine konservative Abschätzung des intrinsischen Schwellenwerts erlaubten. Bei Lastverhältnissen 𝑅 ≪ 0,8 wurde ein teilweise stark ausgeprägter Einfluss extrinsischer Effekte auf das Rissfortschrittsverhalten festgestellt. Eine Untersuchung der Bruchflächen ergab Oxidschichtdicken in der Größenordnung mehrerer hundert Nanometer. Bei Reduktion der Prüffrequenz auf ≈55 Hz und Prüfung in feuchter Luft (60 % r.F. und 80 % r.F.) konnte auch bei 𝑅 = 0,8 Rissschließen beobachtet werden. Die weiterentwickelte Prozedur zur Bauteilauslegung auf Basis effektiver Rissfortschrittsdaten lieferte aber stets konservative Ergebnisse in einem tolerierbaren Fehlerbereich und ist deshalb zur Anwendung geeignet. Die im Projekt gewonnenen Erkenntnisse tragen zu einer robusten Bauteilauslegung auf bruchmechanischer Basis bei. Der stark reduzierte Versuchsumfang bei Nutzung effektiver Rissfortschrittsdaten gegenüber der Ermittlung von spannungsverhältnisabhängigen Rissfortschrittskurven beschleunigt und vereinfacht die Bauteilauslegung auf Basis bruchmechanischer Methoden. KW - Schwellenwert gegen Ermüdungsrissausbreitung KW - Einflussfaktoren auf Rissfortschrittsdaten KW - Bauteilauslegung KW - Rissschließeffekte PY - 2023 SN - 978-3-96780-151-4 SP - 1 EP - 190 PB - Forschungsvereinigung Stahlanwendung e. V. CY - Düsseldorf AN - OPUS4-58459 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Giese, Marcel T1 - Experimentelle Charakterisierung der WIG-Schweißeignung einer Hoch- und Mediumentropie-Legierung N2 - Equiatomic multi-element systems with defined entropy are a relatively new mate-rial concept for alloy production. These alloys consist of at least five elements in equiatomic distribution in the case of high entropy alloys (HEA) and three to four elements in equiatomic distribution in the case of medium entropy alloys (MEA). Previous studies on these alloys have focused primarily on their production, micro-structure and the resulting material properties. Meanwhile, the focus here is on the processing of the alloys and their influence on future applications. Up to now, there has been insufficient knowledge of the materials and processes involved in weld-ing. In this work, therefore, the weldability of a CoCrFeMnNi-HEA and a CoCrNi-MEA by means of a TIG welding process was investigated as a basic system. To this end, the welding parameters were first determined on a reference alloy (Ni-based: 2.4858) and transferred to the welding of the CoCrFeMnNi-HEA and CoCrNi-MEA. Weldability was assessed by testing the absence of defects and microstructures obtained. The weld metal exhibited the dendritic microstructure typical of TIG, with microsegregations forming as interdendritic phases. Increased hardness was de-tected in the weld metal compared to the base metal. In the heat-affected zone, there was little grain growth and, in both alloys, the formation of hot cracks after welding. The cause of the cracks was to be found in the specimen preparation, which had an influence on the subsequent processing. After elimination of this in-fluence, no welding process-related imperfections were found in the CoCrFeMnNi-HEA and CoCrNi-MEA. In summary, both materials show good fusion weldability by TIG welding. The re-sults of this work thus contribute to the understanding of the weldability of HEA and in particular for CoCrNi-MEA, which was considered in this depth for the first time. KW - WIG-Schweißen KW - Hochentropielegierung KW - Mediumentropielegierung PY - 2021 SP - 1 EP - 79 CY - Otto von Guericke Universität AN - OPUS4-53644 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madia, Mauro A1 - Vojtek, T. A1 - Duarte, Larissa A1 - Zerbst, Uwe A1 - Pokorný, P. A1 - Jambor, M. A1 - Hutař, P. T1 - Determination of fatigue crack propagation thresholds for steel in presence of environmental effects N2 - The experimental determination of the resistance to fatigue crack propagation in steel, particularly in the socalled near-threshold regime, is a crucial issue for safety-relevant components which are designed to operate for a large number of loading cycles before undergoing periodic inspections. This work summarizes the most relevant results of extensive experimental campaigns conducted at BAM and IPM over the last years, which have been devoted to the determination of fatigue crack propagation characteristics on medium and high strength steels. The influence of environment, oxide-induced crack closure and test methodologies in the near-threshold regime are discussed. KW - Steel KW - Fatigue crack propagation threshold KW - Oxide-induced crack closure KW - Environmental effect PY - 2021 DO - https://doi.org/10.1016/j.ijfatigue.2021.106449 SN - 0142-1123 VL - 153 SP - 1 PB - Elsevier Ltd. AN - OPUS4-53525 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Zerbst, Uwe A1 - Madia, Mauro ED - Yadroitsev, I. ED - Yadroitsava, I. ED - Du Plessies, A. ED - McDonald, E. T1 - Structural integrity II: fatigue properties N2 - If a component is cyclically loaded, its load carrying capacity is considerably lower than in the monotonic loading case. This general observation applies in particular to L-PBF parts. The causes of this are mainly material defects such as pores and unwelded regions (Chapter 8) and a pronounced surface roughness in the as-built condition (Chapter 9). In addition, effects due to the anisotropy of the microstructure (Chapter 6) and a complex residual stress pattern (Chapter 7) play an important role. A consequence is that common strategies of fatigue assessment cannot be transferred to L-PBF applications without modifications. Due to the inhomogeneity of the material, the determination of representative material properties and the transfer to the component is a problem, and this is also the case with regard to the consideration of defects, surface roughness and residual stresses. The chapter gives a brief introduction to these problem areas. KW - Fatigue crack propagation stagesdefects KW - Fatigue strength KW - Fatigue life KW - Fracture mechanics PY - 2021 SN - 978-0-12-824090-8 DO - https://doi.org/10.1016/B978-0-12-824090-8.00015-9 SP - 377 EP - 394 PB - Elsevier Inc. CY - Amsterdam ET - 1 AN - OPUS4-52854 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Structural integrity of cold spray repaired aerospace components N2 - Components in aircrafts are usually replaced when critical defects are present. An alternative approach is repairing using gas dynamic cold spraying: metal particles are shot at a surface at supersonic speeds to selectively rebuild damaged material. Compared to other material-deposition techniques, its advantage is the small thermal impact on the component, preserving its mechanical properties. Component-repair can save considerable amounts of energy and resources. However, its industrial application at large scale needs reproducible, good repair-material properties to guarantee a safe component life. The aim of this project is the development of safe, automatized repair-procedures considering the mechanical fatigue properties of the repair. T2 - ICEAF VII Conference 2023 CY - Spetses, Greece DA - 21.06.2023 KW - Cold Spray KW - Repair KW - Fatigue KW - Fatigue Crack Growth KW - Slow Strain Rate Testing PY - 2023 AN - OPUS4-57784 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - BOOK A1 - Zerbst, Uwe A1 - Madia, Mauro T1 - Bruchmechanische Bauteilbewertung N2 - Die sichere Auslegung von Bauteilen kommt an der Anwendung bruchmechanischer Methoden heute nicht mehr vorbei. Das vorliegende Buch bietet eine Einführung in diese Methoden mit besonderen Schwerpunkten auf dem aktuellen Stand der bruchmechanischen Kennwertermittlung und den Methoden der analytischen bruchmechanischen Bauteilbewertung. Es beschreibt die Mechanismen von Risswachstum und Bruch, die grundlegenden Konzepte der Bruchmechanik, die analytische Ermittlung der Rissspitzenbelastung in Bauteilen sowie die Anwendung der Bruchmechanik in unterschiedlichen Kontexten. Der Schwerpunkt liegt dabei auf der praktischen Anwendung u. a. anhand von Demonstrationsbeispielen, die im Detail nachvollzogen werden können. KW - Rissausbreitung KW - Bruch KW - Bruchmechanische Konzepte KW - Bruchmechanische Kennwerte KW - Rissspitzenbelastung KW - Failure Assessment Diagram KW - Rissschließfunktion KW - Kritische Last KW - J-Integral KW - Risswiderstand KW - Stretch-Zone KW - IBESS-Prozedur KW - Constraint faktor KW - Mismatch KW - Ligamentplastifizierung KW - Crack Tip Opening Displacement (CTOD) PY - 2022 SN - 978-3-658-36150-1 SN - 978-3-658-36151-8 DO - https://doi.org/10.1007/978-3-658-36151-8 SP - C1 EP - 372 PB - Springer CY - Heidelberg AN - OPUS4-56004 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nietzke, Jonathan A1 - Rhode, Michael A1 - Mente, Tobias A1 - Kannengießer, Thomas T1 - Experimental and numerical characterization of hydrogen diffusion in thick-walled submerged arc welded joint of S420G2+M offshore steel grade N2 - Offshore wind turbines are an important goal in national energy strategies worldwide. Foundation structures are manufactured from submerged arc welded (SAW) plates with thicknesses up to 200 mm. In that connection, high-strength steels like the S420G2+M are more and more applied offering the possibility for increased stability and load-bearing capacity of the foundations. These offshore steel grades can show a susceptibility for delayed hydrogen assisted cold cracking of the weld joints. For that purpose, a minimum waiting time (MWT) of up to 48 h (dependent on applied standards) is recommended before non-destructive testing is allowed and conducted. But this concept is based on older steel grades that have been used for three or more decades. Nowadays, the metallurgical improvements (clean steels, proper rolling, and heat treatment) of base materials and well as welding consumables must be anticipated. Hence, the MWT concept should be critically discussed as it is assumed to be very conservative. For that reason, the focus of this study was to investigate the diffusion behavior in S420G2+M steel and its multi-layer SAW joint. Electrochemical permeation experiments were carried at room temperature. Boundary conditions were anticipated in terms of using different sample thicknesses. From the experimental data, hydrogen diffusion coefficients and absorbed diffusible hydrogen concentrations had been calculated. It was shown that hydrogen diffusion in the base material is increased compared to the weld metal. In addition, the sample thickness had a significant on the calculated diffusion coefficients. The minimum and maximum diffusion coefficients had been used for numerical modelling of the hydrogen diffusion in the welding joint. It became clear that a MWT must be always regarded together with a critical initial diffusible hydrogen concentration for the evaluation of a possible delayed cracking as diffusion times were mostly > 48 h due to the thick plates. T2 - 4th International Conference on Metals and Hydrogen - Steely & Hydrogen 2022 CY - Ghent, Belgium DA - 11.10.2022 KW - Hydrogen KW - Submerged arc welding KW - Diffusion KW - Minimum waiting time KW - Electrochemical permeation PY - 2022 SP - 1 EP - 11 CY - Ghent, Belgium AN - OPUS4-56075 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Nietzke, Jonathan A1 - Czeskleba, Denis A1 - Kannengießer, Thomas T1 - Untersuchung von Spannungsrelaxationsrissmechanismen mittels Simulation einachsiger Spannungszustände in der Grobkornzone von UP-geschweißtem CrMoV-Stahl N2 - Druckbehälter mit großen Wandstärken (250+ mm) aus hochwarmfesten, niedriglegierten Stählen werden hauptsächlich Mehrdraht-Unterpulver-(UP) geschweißt. Der damit verbundene hohe Energieeintrag führt unter anderem zu hohen lokalen Schweißeigenspannungen, welche bei unsachgemäßer Prozessführung der notwendigen Wärmenachbehandlung (PWHT) zu Spannungsrelaxationsrissen (SRR) führen. In den Bewertungskriterien zur Spannungsrelaxationsrissanfälligkeit finden weder die, mit klassischen, freischrumpfenden Schweißversuchen nicht abbildbaren, erhöhten Eigenspannungen aus der Schrumpfbehinderung der Bauteilsteifigkeit Beachtung, noch die damit einhergehenden metallurgischen Effekte wie bspw. das Ausscheidungswachstum während der PWHT und damit einhergehende Härteunterschiede an den Korngrenzen bzw. die vorzeitige Alterung durch Bildung differenter Sonderkarbide. Die Aufheizrate des PWHT als Einflussfaktor für die SRR-Bildung bleibt derzeit ebenfalls unbeachtet. Daher wurde eine Versuchsmethodik entwickelt, die eine mögliche SRR-Anfälligkeit durch die Kopplung von thermischer und mechanischer Beanspruchung untersucht. Dazu wurden Proben mit unterschiedlichen Gefügen thermisch simuliert und während des PHWT repräsentativ mit sehr hohen Lasten/Eigenspannungen mechanisch beansprucht. Dazu wurde an Kleinzugproben für das as-welded UP-Schweißgut und die thermisch simulierte GKZ eines 13CrMoV9-10 die Dehnung des Prüfbereichs bei variablen Querspannungen und Aufheizraten gemessen. Diese aufheizraten- und gefügeabhängige Längenänderung der Probe wurde durch mathematische Prozeduren analysiert. Damit war es möglich, singuläre werkstoffliche Effekte auf μm-Ebene (Ausscheidungswachstum) als summarische Längen- bzw. Volumenänderung per klassischer Kurvendiskussion zu beschreiben. Die erste und zweite Ableitung zeigten eine ausscheidungsabhängige Härtezunahme, welche von der Spannung und Aufheizrate im geringen Maß linear abhängig war. Gleichzeitig sind Volumenänderungen bei Bildung und Wachstum differenter Sonderkarbide bekannt, welche zusammen mit gefügespezifischen Untersuchungen und der neuen Versuchsmethodik zu einer verbesserten Beurteilung der SRR-Anfälligkeit von geschweißten CrMoV-Stählen beitragen sollen. Prinzipiell ist die vorgestellte Methodik jedoch werkstoff- und zustandsoffen, d.h. sowohl für Grundwerkstoff e als auch definierte Wärmebehandlungsbedingungen geeignet. Dies ermöglicht erstmals die Schaffung einer Transfergröße zwischen Labor und realen Schweißungen, unter Beibehaltung der Bauteilsteifigkeit, d.h. vereinfachte, aber realistische Eigenspannungsabbildung als Grundlage für weitergehende gefügespezifische metallurgische Effekte während des PWHT. T2 - DVS Congress 2022 CY - Koblenz, Germany DA - 19.09.2022 KW - UP-Schweißen KW - Spannungsrelaxationsriss KW - Wärmenachbehandlung KW - Ersatzgeometrie KW - Prüfverfahren PY - 2022 SN - 978-3-96144-190-7 VL - 382 SP - 69 EP - 75 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-55946 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Czeskleba, Denis T1 - Entwicklung von Wärmenachbehandlungskonzepten zur Vermeidung von Spannungsrelaxationsrissen - Endbericht (DVS-Nr. 01.2261, IGF-Nr. 20171 N) N2 - Komponenten aus dickwandigen, hochwarmfesten CrMoV-Stählen erfordern eine anspruchsvolle UP-Schweißverarbeitung. Dabei muss die notwendige Wärmenachbehandlung der Schweißnaht (PWHT) sicher beherrscht werden. Hier kann u.U. Bauteilversagen infolge von Spannungsrelaxationsrissbildung (SRR) auftreten. Bislang erfolgt die Beurteilung der SRR-Neigung primär über Ersatzgrößen, wie temperaturbedingte Änderung der Härte und Duktilität. Die Wirkung der konstruktiven Schrumpfbehinderung einer Schweißnaht auf die SRR ist bislang völlig unbekannt. Hier setzt das Forschungsprojekt an, hinsichtlich der Gewinnung und Optimierung der Parameter für die PWHT unter realitätsnahen Bauteilsteifigkeiten (definierte Einspannbedingung) mit dem Ziel der SRR-Vermeidung. Am Beispiel des niedriglegierten, hochwarmfesten Stahls 13CrMoV9-10 wurden UP-Schweißungen unter industriepraktischen Bedingungen freischrumpfend bzw. unter definierter Schrumpfbehinderung durchgeführt. Diese wurden mit unterschiedlichen PWHT-Szenarien (Variation der Aufheizrate und Endtemperatur) beaufschlagt. Die Ergebnisse des Projektes DVS 01.2261 / IGF 20171 N werden in diesem Beitrag vorgestellt. T2 - DVS Congress 2022 CY - Koblenz, Germany DA - 19.09.2022 KW - UP-Schweißen KW - Spannungsrelaxationsriss KW - Forschung KW - Wärmenachbehandlung PY - 2022 AN - OPUS4-55945 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Czeskleba, Denis T1 - Untersuchung von Spannungsrelaxationsrissmechanismen mittels Simulation einachsiger Spannungszustände in der Grobkornzone von UP geschweißtem CrMoV Stahl N2 - Druckbehälter mit großen Wandstärken (250+ mm) aus hochwarmfesten, niedriglegierten Stählen werden hauptsächlich Mehrdraht-Unterpulver-(UP) geschweißt. Der damit verbundene hohe Energieeintrag führt unter anderem zu hohen lokalen Schweißeigenspannungen, welche bei unsachgemäßer Prozessführung der notwendigen Wärmenachbehandlung (PWHT) zu Spannungsrelaxationsrissen (SRR) führen. In den Bewertungskriterien zur SRR-Anfälligkeit finden weder die, mit klassischen, freischrumpfenden Schweißversuchen nicht abbildbaren, erhöhten Eigenspannungen aus der Schrumpfbehinderung der Bauteilsteifigkeit Beachtung, noch damit einhergehende metallurgischen Effekte. Die Aufheizrate des PWHT als Einflussfaktor für die SRR-Bildung bleibt blieb bisher unbeachtet. Daher wurde eine Versuchsmethodik entwickelt, die eine mögliche SRR-Anfälligkeit durch die Kopplung von thermischer und mechanischer Beanspruchung untersucht. Dazu wurden Proben mit unterschiedlichen Gefügen thermisch simuliert und während des PHWT repräsentativ mit sehr hohen Lasten/Eigenspannungen mechanisch beansprucht. Dazu wurde das as-welded UP-Schweißgut und die thermisch simulierte GKZ eines 13CrMoV9-10 Stahls untersucht und an Kleinzugproben, die Dehnung bei variablen Querspannungen und Aufheizraten gemessen. T2 - DVS Congress 2022 CY - Koblenz, Germany DA - 19.09.2022 KW - UP-Schweißen KW - Spannungsrelaxationsriss KW - Wärmenachbehandlung KW - Prüfverfahren KW - CrMoV-Stahl PY - 2022 AN - OPUS4-55947 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nietzke, Jonathan A1 - Konert, Florian T1 - Experimental and numerical characterization of hydrogen diffusion in thick-walled submerged arc welded joint of S420G2+M offshore steel grade N2 - Offshore wind turbines are an important goal in national energy strategies worldwide. Foundation structures are manufactured from submerged arc welded (SAW) plates with thicknesses up to 200 mm. In that connection, high-strength steels like the S420G2+M are more and more applied offering the possibility for increased stability and load-bearing capacity of the foundations. These offshore steel grades can show a susceptibility for delayed hydrogen assisted cold cracking of the weld joints. For that purpose, a minimum waiting time (MWT) of up to 48 h (dependent on applied standards) is recommended before non-destructive testing is allowed and conducted. But this concept is based on older steel grades that have been used for three or more decades. Nowadays, the metallurgical improvements (clean steels, proper rolling, and heat treatment) of base materials and well as welding consumables must be anticipated. Hence, the MWT concept should be critically discussed as it is assumed to be very conservative. For that reason, the focus of this study was to investigate the diffusion behavior in S420G2+M steel and its multi-layer SAW joint. Electrochemical permeation experiments were carried at room temperature. Boundary conditions were anticipated in terms of using different sample thicknesses. From the experimental data, hydrogen diffusion coefficients and absorbed diffusible hydrogen concentrations had been calculated. It was shown that hydrogen diffusion in the base material is increased compared to the weld metal. In addition, the sample thickness had a significant on the calculated diffusion coefficients. The minimum and maximum diffusion coefficients had been used for numerical modelling of the hydrogen diffusion in the welding joint. It became clear that a MWT must be always regarded together with a critical initial diffusible hydrogen concentration for the evaluation of a possible delayed cracking as diffusion times were mostly > 48 h due to the thick plates. T2 - 4th International Conference on Metals and Hydrogen - Steely & Hydrogen 2022 CY - Ghent, Belgium DA - 11.10.2022 KW - Hydrogen KW - Submerged arc welding KW - Minimum Waiting Time KW - Cold Cracking KW - Offshore steel grade PY - 2022 AN - OPUS4-56008 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - LTT-Zusatzwerkstoffe zur Optimierung von Schweißeigenspannungen N2 - Der Vortrag gibt eine Einführung zum Thema LTT-Zusatzwerkstoffe. Anhand experimenteller Befunde werden die Mechanismen erläutert und die Auswirkungen auf die Schweißeigenspannungen verdeutlicht. T2 - 1. LTT-Workshop des ISF RWTH Aachen CY - Aachen, Germany DA - 11.05.2022 KW - LTT-Zusatzwerkstoff KW - Hochfester Stahl KW - Eigenspannungen KW - Martensit KW - Phasenumwandlung PY - 2022 AN - OPUS4-56267 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel T1 - The debye waller factor for temperature distribution determination in NBEI experiments: a case study for GTAW N2 - We could show in GTAW experiments with steel samples that the attenuation of neutron transmission underneath the welding torch due to the Debye-Waller-effect correlates well with sample temperatures obtained by FE numerical simulations. This would allow principally to determine sample temperatures by measuring the neutron beam attenuation. T2 - ITMNR-9 CY - Buenos Aires, Argentina DA - 17.10.2022 KW - Debye waller factor KW - GTAW KW - Temperature distribution determination PY - 2022 AN - OPUS4-56150 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Repair welding of pressurized in-service hydrogen pipelines - A review on current challenges and strategies N2 - As energy carrier of the future, green hydrogen can make a decisive contribution to a sustainable energy supply. Particularly important is the decarbonization of heavy industry. Therefore, a reliable supply of hydrogen must be guaranteed. A hydrogen pipeline grid can achieve this purpose. In Europe concrete plans for a hydrogen pipeline grid already exist, as the so called “European Hydrogen backbone”. As building a completely new pipeline grid is economically not justifiable, a dual-way strategy of repurposing natural gas (NG) pipelines and newly built pipelines is intended. Long distance pipeline grids require regular maintenance and repairs. For natural gas (NG) pipelines in-service welding is state of the art. Concepts such as hot-tapping (drilling into pressurized pipelines) and “stoppling” (sealing off pipeline sections after installing bypasses or pressure relieves) allow the repair of damaged pipeline sections or the installation of new branches without shutting the pipeline down, which in most cases isn’t possible from an economic standpoint. The EIGA 121/14 guideline already pointed out in 2014 that “a hydrogen hot-tap shall not be considered a routine procedure”. This shows that the determination of the transferability of these repair concepts to hydrogen pipelines is of utmost importance. Due to the degrading effects of hydrogen on mechanical proper-ties, commonly referred to as “hydrogen embrittlement” it is necessary to understand and investigate the occurring effects. In the special case of repair welding on in-service hydrogen pipelines an increased hydro-gen uptake due to a large heat input and microstructural changes in the material needs to be considered. Therefore, material degradation must be investigated to determine whether modifications of repair procedures are necessary to ensure a reliable and safe hydrogen transportation via pipelines. For this reason, this paper gives an overview on existing weld repair concepts and its risks and limitations in terms of hydrogen absorption and possible embrittlement effects when transferred to hydrogen pipelines. The complexity lies in a large variety of materials (low alloyed steels), pipeline diameters and corresponding welded joints. The material compatibility of materials in used (repurposed NG-pipelines) and new condition must be investigated. Particularly for repurposed/used pipelines the effect of a pre-matured/corroded inner surface and sometimes insufficient documentation of the material “history” needs to be considered. An overview on ongoing and completed R&D-projects with respect to repair concepts for hydrogen pipelines and hydrogen effects on pipeline materials is given. The focus hereby lies on possible methods of material testing and modeling. Its current difficulties, limits and possible solution will be discussed. T2 - IIW Intermediate Meeting, Com. II-A CY - Incheon, Republic of Korea DA - 12.03.2024 KW - Hydrogen KW - Repair welding KW - Pipelines KW - In-service PY - 2024 AN - OPUS4-59674 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Combined effect of heating rate and restraint condition on stress relief cracking susceptibility during PWHT of thick-walled Cr-Mo-V steel submerged arc welded joints N2 - Contemporary steels creep-resistant steels like the 13CrMoV9-10 are used as thick plates e.g., for applications in hydrocrackers. The large plate thickness requires high efficiency welding processes like submerged arc welding (SAW) and a mandatory post weld heat treatment (PWHT). The PWHT-parameters stem from a combination of empirical knowledge and traditional experiments on free shrinking (FS) welds. In that connection, the formation of so-called stress-relief cracking (SRC) must be anticipated. The SRC susceptibility of a welded component is a complex combination and interaction of com-ponent specific, thermal, and metallurgical factors. Many of which have to date not been conclusively researched. For example, it is well known that SRCs develop during PWHT due to formation and growth of carbides on prior austenite grain boundaries, resulting in a significant hardness increase (secondary hardening) and toughness decrease. This leads to a high SRC susceptibility of the coarse grain heat-affected zone (CGHAZ) of the last weld bead during PWHT. This is intensified in case of high residual stresses from the component-specific, structurally induced stiffness. In combination with multi-layer welding this leads to a multiaxial stress distribution. Nonetheless, the combined effect of PWHT and high-residual stresses on the SRC formation is merely unknown. For that reason, this study presents the effect of different heating rates in conjunction with a certain component stiffness. For that reason, SAW joints of 13CrMoV9-10 steel were investigated under FS and defined external restraint condition. T2 - IIW Intermediate Meeting, Com. II-A CY - Incheon, Republic of Korea DA - 12.03.2024 KW - Stress relief cracking KW - Welding KW - Post weld heat treatment KW - Submerged arc welding KW - Cr-Mo-V steel KW - Creep-resisting steel PY - 2024 AN - OPUS4-59673 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Call for interested people to contribute to series of comprehensive papers on welding and joining of components for sustainable energy systems N2 - Joining and welding technologies are of high importance for the manufacturing of components and parts used in sustainable energy generation, conversion, and transport. In that connection, offshore and on-shore installed wind turbines are of high interest for the generation of electrical energy as well as photo-voltaic systems (solar cells). The electricity can be either directly transported or conversed via power-to-gas e.g., to hydrogen. In that scope, electrolyzer up to MW-range are of interest as well as the conver-sion back to electricity via fuel cells. In addition, hydrogen is a key element of the decarburization of in-dustries as well as the mobility sector encompassing sea, air and land transportation driven by hydrogen or its derivates. Well-known examples cover the direct reduction of iron ore to replace the conventional blast furnace process up to gas turbines or fuel cells for home-end use. All mentioned technologies re-quire reliable components, which are to a high extend dependent on joining and especially welding pro-cessing of materials. Especially, the (petro-) chemical industry has many years of experience with both materials used in hydrogen applications. The challenge is e.g., the transition to mass production of sys-tem components of electrolyzers/fuel cells and for distribution grids. At this point, the scalability of cur-rently applied joining processes often limits the economic efficiency, whereas especially laser welding or additive manufacturing will be of high interest. In that connection, it is very important to provide answers by joint research of universities, institutes, and industrial companies. Very often, solutions are already available and “just” have to be investigated and adapted for the new application, like repair welding of NG pipelines. For that reason, we want to set up a series of comprehensive papers with the aforementioned title. The idea is to get an in-depth but manageable overview of the importance of joining technologies in sustaina-ble energy generation, conversion, and transport encompassing current processes, limitations, and fur-ther perspectives. In that connection, the additive manufacturing is gaining more and more attention. If applicable, current challenges in the adaption or creation of new standards/regulations shall be addressed. T2 - IIW Intermediate Meeting, Com. II-A CY - Incheon, Republic of Korea DA - 12.03.2024 KW - Hydrogen KW - Welding KW - Comprehensive study KW - Component manufatcturing KW - Additive manufacturing PY - 2024 AN - OPUS4-59676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Liepold, Philipp T1 - CTS Testing of High-Strength Filler Materials N2 - Controlled Thermal Severity (CTS) tests are known for applicatying high restraint intensity to fillet welds. Due to two different variations of the test it was possible to apply different amounts of restraint intensity to high-strength GMAW fillet welds at a high level of restraint. The results show the effect of heat input, filler material and restraint intensity on solidification cracking susceptibility. T2 - DIN Sitzung NA 092-00-05 GA „Zerstörende Prüfung von Schweißverbindungen“ (DVS AG Q 4/Q 4.1) CY - Berlin, Germany DA - 20.03.2024 KW - CTS PY - 2024 AN - OPUS4-59773 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Eigenspannungsabbau mittels LTT - Schweißzusätzen unter Berücksichtigung der Nahtgeometrie N2 - Der Vortrag befasst sich mit der gezielten Einbringung zusätzlicher LTT-Lagen zur Erzeugung von Druckeigenspannungen in ermüdungskritischen Bereichen von konventionellen Schweißverbindungen. Dies ermöglicht eine wirtschaftliche Lösung, ohne die Integrität der Schweißverbindungen zu beeinträchtigen. Dazu wurden Längssteifen aus hochfestem Stahl in der ersten Lage mit konventionellem Schweißzusatzwerkstoff mittels Metall-Lichtbogenschweißen geschweißt. Anschließend wurde ein Chrom-Nickel-legierter LTT-Schweißzusatz auf die Stirnseiten der Steifen aufgebracht. Durch Variation der Schweißparameter konnten verschiedene Schweißnahtgeometrien des LTT-Zusatzwerkstoffs analysiert werden. T2 - NA 092-00-05 GA "Gemeinschaftsarbeitsausschuss NAS/NMP: Zerstörende Prüfung von Schweißverbindungen (DVS AG Q 4/Q 4.1) CY - Berlin, Germany DA - 20.03.2024 KW - LTT KW - Eigenspannungen KW - hochfester Stahl PY - 2024 AN - OPUS4-59752 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Investigation of hot cracking susceptibility via Modified Varestraint Transvarestraint testing of high-strength filler material N2 - MVT testing was conducted in Transvarestraint mode in multiple welding conditions and under a range of bending speeds. The materials observed were high strength filler metals used in GTAW namely DIN EN ISO 16834-A G 69 4 M21 Mn3Ni1CrMo (G69), 16834-A G 89 6 M21 Mn4Ni2CrMo (G89 6), 16834-A G 89 5 M21 Mn4Ni2,5CrMo (G89 5) and a filler wire 18276-A T 89 4 ZMn2NiCrMo M M21 1 H5 (T89). For evaluation light optical microscope pictures were used. Pixels containing cracks were manually segmented using a self-written program. Out of the segmented images data including crack length, position and area can be calculated for every crack. The results show dependencies of solidification cracking on the test parameters. T2 - IIW Intermediate Meeting Comission II-C CY - Incheon, Republic of Korea DA - 12.03.2024 KW - Solidification cracking KW - High strength steel KW - Varestraint test PY - 2024 AN - OPUS4-59749 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröder, Nina T1 - Ti and Nb influence on the HAZ microstructures of weld-simulated high strength structural steel S690QL N2 - High-strength low-alloyed (HSLA) steels with yield strength / proof stress ≥ 600 MP are the basis of modern light-weight steel constructions. Indeed, the economic and ecological benefits strongly depend on their processability in terms of welding. In this context, he use of highly productive welding processes, suitable welding consumables is of vital interest and requires a fundamental understanding of the microstructural changes in the HSLA steel and especially the heat-affected zone (HAZ) of the welded joint. Microalloying elements, such as Ti or Nb, are essential to achieve the desired mechanical properties. In this context, the underlying standards such as EN 10025-6 only specify maximum values, resulting in different manufacturer customized microalloy concepts. Furthermore, even small deviations can have a drastic effect expressed by an excessive hardening or softening despite identical welding conditions and filler metal. The reason is the different thermal stability of the Ti and Nb-related precipitates (typically carbides or carbon nitrides). As a result, it is difficult (or even impossible) to adequately predict the weldability. Against this background, different microalloying routes with varying Ti and Nb contents for a S690QL reference grade were systematically investigated in terms of lab-cast alloys close to realistic chemical compositions. To investigate the influence of the welding heat input on the HAZ microstructure formation, physical simulations were carried with specified peak temperatures and cooling times (by a dilatometer, see Fig. 1a). The focus was the identification of the occurring phase transformations during cooling and the final HAZ microstructure, see Fig. 1b. In this context, a double welding cycle was simulated to further identify the behavior of the so-called intercritical HAZ (where softening is likely to occur) in case of the common multi-layer welding for thick plates, see Fig. 1c. The results showed: (1) microalloying has significant influence on the formation of the individual HAZ dependent on (2) the thermal stability of the Ti or Nb-precipitates and (3) synergistic effects of further elements such as Mo and their effect on phase transformations in the HAZ. The results represent a microstructure-based validation of welding processing of such HSLA-steels e.g. in terms of preferred microalloy and weld heat input combinations. T2 - MaterialsWeek/SteelInnovation 2025 CY - Frankfurt am Main, Germany DA - 02.04.2025 KW - HSLA KW - Dilatometry KW - Microalloying elements KW - HAZ-Softening KW - Digital Image Correlation (DIC) PY - 2025 AN - OPUS4-62938 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Simulation der Wasserstoffverteilung in UP-geschweißten Grobblechen als Bewertungstool für die Kaltrissanfälligkeit von Offshorestrukturen N2 - Gründungsstrukturen für Offshore-Windkraftanlagen bestehen in der Regel aus hochfesten Stahlgrobblechen, die im UP-Verfahren geschweißt werden, durch den u.U. größere Mengen an Wasserstoff eingebracht werden können. Die große Blechdicke führt zudem zu langen Diffusionswegen und einer verlängerten Diffusionszeit für den Wasserstoff. Infolgedessen kann sich der Wasserstoff in Bereichen mit hoher mechanischer Spannung und Dehnung ansammeln und daher zu einer verzögerten Kaltrissbildung führen. Aufgrund der verzögerten Diffusion muss daher eine Mindestwartezeit von bis zu 48 h eingehalten werden, bevor eine zerstörungsfreie Prüfung durchgeführt wird. Darüber hinaus ist die Beurteilung möglicher Kaltrissstellen sehr komplex. Es wurde daher ein numerisches Modell zur Abbildung einer bauteilähnlichen Schweißnahtprüfung entwickelt. Dazu wurde das Temperaturfeld während des Schweißens und der anschließenden Abkühlung experimentell bestimmt und numerisch simuliert. Auf dieser Grundlage wurde Diffusionsmodell zur numerischen Simulation der zeitlich-örtlichen Wasserstoffkonzentration erstellt. Mit diesem Modell wurden zwei Anwendungsfälle simuliert: (1) Veränderung der Wasserstoffverteilung als Funktion des Temperaturzyklus während des Mehrlagenschweißens und (2) für das Wartezeitintervall ≤ 48 h. Ein Vorteil des Diffusionsmodells ist die Simulation einer normierten Konzentration, d.h. zwischen „0“ (kein Wasserstoff) und „1“ (max. Konzentration), die auf experimentell ermittelte Wasserstoffkonzentrationen skaliert werden kann. T2 - 6. Symposium Materialtechnik CY - Clausthal-Zellerfeld, Germany DA - 20.02.2025 KW - Gründungsstrukturen KW - Offshore KW - Kaltrissbildung KW - Wasserstoff KW - Numerische Simulation PY - 2025 AN - OPUS4-62616 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Reichel, Levin A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Modern welding processes for optimising repair welds on high strength offshore steels 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 coast are required with large subsea jacket structures (30 m up to 50 m) and tall towers (up to 200 m). High-strength steels with a yield strength up to 500 MPa and wall thicknesses up to 150 mm are increasingly being used for these structures. This plac-es high demands on welding manufacturing, especially for high-strength offshore steels. During the manu-facturing process detected defects by NDT require localized repair of welds by gouging and rewelding. Due to a lack of investigations, there are no repair concepts and information in standards and guidelines, par-ticularly for high-strength thick plate joints made of high-strength offshore steels. However, these are ur-gently needed to enable manufacturers, especially SMEs, to carry out safe and economical repairs. There-fore, BAM started 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 with controlled high-performance GMAW pro-cesses and optimized narrow gouging grooves. The experimental analyses take into account the complex interaction of process, material, and design-related influences on the formation of weld induced stresses and the special microstructure of high-strength fine-grain structural steels. Welding-related material degra-dation and crack-critical residual tensile stresses need to be avoided to ensure high component safety and performance. A reduction in residual stress in the presence of high restraint conditions can be achieved by adapted heat control (if no disassembly measures are possible). The repair process involves manual thermal gouging, which allows the groove configuration to be modi-fied. Modern welding processes using high frequency arc control provide deep root penetration and focused energy input capable of welding narrow seams. A comparison was made between the traditional weld con-figuration with a wide 45° groove and transition arc welding and a narrow 30° groove with modern welding process. Even in the case of free shrinkage specimens, the narrow groove weld exhibits a significant reduc-tion of residual stresses, cf. Figure 1, especially in the HAZ and toward the adjacent base material. This can be attributed to the lower weld metal volume needed and the reduction of heat input per layer due to the controlled arc process. For the purposes of this comparison, the same weld seam build-up (but different number of layers) has been applied to both seam configurations. Note that in industrial application (manu-al welding), the wider groove would be welded with several off-center weld beads with conventional weld-ing process. In this analysis this would cause asymmetric effects regarding the residual stress state, diffi-cult to compare to each other. Component-related welding experiments on special testing equipment, adapted process and heat control concepts along with variable groove configurations will be developed and recommendations for guidelines elaborated. This is the prerequisite for fully utilizing the strength potential of high-strength steels and making a valuable contribution to the energy transition in Germany, especially for steel-processing SMEs. T2 - IIW Intermediate Meeting CII CY - Trollhättan, Sweden DA - 10.03.2025 KW - Repair welding KW - Gouging KW - Residual stress KW - Offshore wind turbines KW - High-strength steels PY - 2025 AN - OPUS4-62743 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Dittmann, Florian A1 - Varfolomeev, Igor T1 - Untersuchung der Ermüdungsfestigkeit von LTT-geschweißten Längssteifen mit variierender Nahtausführungen N2 - Low Transformation Temperature (LTT) Schweißzusätze erzeugen während der Abkühlung Druckeigenspannungen in die Schweißnaht und Wärmeeinflusszone durch eine Volumenexpansion, wodurch die Ermüdungsfestigkeit erhöht werden kann. Um das Potential dieser neuartigen Schweißzusätze besser zu quantifizieren, wurden konventionelle Längssteifen als Probenkörper verwendet, welche an den Stirnseiten mit einer LTT-Zusatznaht geschweißt wurden. Durch Variation der Schweißparameter konnten unterschiedliche Nahtformen realisiert werden. Es konnte, je nach Nahtausführung, eine Erhöhung der Ermüdungsfestigkeit bei 2 Millionen Lastwechsel von 64 MPa bis 100 MPa in Gegensatz zu konventionellen Proben festgestellt werden. Somit sind LTT-Zusätze grundsätzlich geeignet, um die Ermüdungsfestigkeit zu erhöhen. T2 - Frühjahrssitzung 2025 des Fachausschusses Eigenspannungen der AWT CY - Karlsruhe, Germany DA - 07.04.2025 KW - LTT (Low Transformation Temperature) KW - Eigenspannungen KW - Ermüdungsfestigkeit KW - Aufmischung PY - 2025 AN - OPUS4-62930 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Dittmann, Florian A1 - Varfolomeev, Igor T1 - Wechselwirkung zwischen Nahtgestaltung und Ermüdungsfestigkeit in LTT-geschweißten Längssteifen N2 - Schweißzusätze mit niedriger Martensitstarttemperatur (Low Transformation Temperature, LTT) induzieren während der Abkühlphase infolge einer volumeninduzierten Martensitumwandlung Druckeigenspannungen in der Schweißnaht sowie in der angrenzenden Wärmeeinflusszone (WEZ). Diese Spannungen können zu einer signifikanten Erhöhung der Ermüdungsfestigkeit führen. Zur quantitativen Bewertung des Potenzials dieser innovativen Werkstoffe wurden konventionelle Längssteifen als Versuchsproben herangezogen, bei denen an den Stirnseiten Schweißnähte unter Verwendung von LTT-Zusatzwerkstoffen appliziert wurden. Durch gezielte Variation der Schweißparameter konnten unterschiedliche Nahtgeometrien realisiert werden. In Abhängigkeit von der Nahtausführung zeigte sich bei einer Belastungszahl von 2 Millionen Zyklen eine Steigerung der Ermüdungsfestigkeit im Bereich von 64 MPa bis 100 MPa im Vergleich zu Referenzproben mit herkömmlichen Schweißzusätzen. Die Ergebnisse belegen, dass der Einsatz von LTT-Schweißzusätzen grundsätzlich geeignet ist, die Ermüdungsfestigkeit geschweißter Strukturen zu verbessern. T2 - Din Sitzung: Gemeinschaftsarbeitsausschuss NAS/NMP, Zerstörende Prüfung von Schweißverbindungen CY - Online meeting DA - 20.03.2025 KW - LTT (Low Transformation Temperature) KW - Eigenspannungen KW - Ermüdungsfestigkeit KW - high-strength steels PY - 2025 AN - OPUS4-62929 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fey, Gero T1 - Dilatometer-based welding simulation: CCT-Diagram and investigation of heat-affected zones in pipeline steels N2 - Presentation of the research project “Hydrogen-dependent mechanical properties of the weld microstructure of low-alloy steels for long-distance gas pipelines” and the present results at the Young Professionals International Conference (YPIC) of the International Institute of Welding (IIW) T2 - 2nd Online Young Welding Professional International Conference - YPIC2025 CY - Online meeting DA - 06.02.2025 KW - Pipeline steel KW - CCT KW - Dilatometry KW - Heat-affected zone PY - 2025 AN - OPUS4-62583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fey, Gero T1 - Dilatometerbasierte Schweißsimulation: ZTU-Diagramme und Untersuchung der Wärmeeinflusszonen in Pipelinestählen N2 - Präsentation des Forschungsprojekts "Wasserstoffabhängige mechanische Eigenschaften der Schweißnahtgefüge niedriglegierter Stähle für Ferngasleitungen" und der bisherigen Ergebnisse auf der 28. Konferenz aller Werkstofftechnischen und Materialwissenschaftlichen Studiengänge (KaWuM) an der TU Ilmenau. T2 - 28. Konferenz aller Werkstofftechnischen und Materialwissenschaftlichen Studiengänge CY - Ilmenau, Germany DA - 07.11.2024 KW - ZTU-Diagramm KW - Wärmeeinflusszone KW - WEZ KW - Dilatometer KW - Pipelinestahl PY - 2024 AN - OPUS4-62418 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Fügetechnik für Wasserstofftechnologien: Ausgewählte Themen und Herausforderungen N2 - Die Präsentation fasst die Bedeutung der Fügetechnik für Wasserstofftechnologien im Rahmen der Arbeiten für einer Studie (DVS-Berichte Nr. 373) mit besonderer Berücksichtigung der Normung und Regelwerkssetzung zusammen. T2 - Sitzung des DIN-Gemeinschaftsarbeitsausschusses NA 092 00 05 GA, NAS/NMP: Zerstörende Prüfung von Schweißverbindungen CY - Online meeting DA - 10.03.2022 KW - Wasserstoff KW - Fügetechnik KW - Schweißen KW - Wasserstofftechnologien KW - Bedeutung PY - 2022 AN - OPUS4-54447 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witte, Julien T1 - Ultraschallunterstütztes Fräsen von Eisenaluminid N2 - Eisenaluminide eignen sich als Werkstoff für sicherheitsrelevante Komponenten welche hohen thermischen, mechanischen und korrosiven Belastungen ausgesetzt sind. Mit ihrer geringen Dichte und der kostengünstigen Verfügbarkeit der Legierungsbestandteile bieten sie ein hohes Marktpotenzial und eignen sich als Substitutionswerkstoff konventioneller Hochtemperaturwerkstoffe. Durch die Verwendung von Dauerformen im Kokillenguss lassen sich FeAl-Bauteile bereits äußerst wirtschaftlich herstellen. Das dabei entstehende komplexe, mehrphasige, sehr feinkörnige Gefüge mit harten Ausscheidungen und hohen Festigkeiten erschwert jedoch eine nachfolgende spanende Bearbeitung mit hohen Belastungen auf Werkzeug und Bauteiloberfläche. Um eine gesamtheitlich wirtschaftliche Herstellungsroute zu ermöglichen, sollen im Hinblick auf die erschwerte Zerspanbarkeit geeignete Werkzeuge und Fräsprozesse entwickelt werden. Durch die Verwendung des hybriden Bearbeitungsverfahrens des ultraschallunterstützten Fräsens können diese Ziele unter Einhaltung der hohen Anforderung an die Oberflächenintegrität sicherheitsrelevanter Bauteile erreicht werden. T2 - Bachelor-, Master-, Doktoranden-Kolloquium der Otto-von-Guericke Universität Magdeburg CY - Online meeting DA - 01.12.2021 KW - Eisenaluminid KW - Zerspanung KW - Ultraschallunterstütztes Fräsen KW - Oberflächenintegrität PY - 2021 AN - OPUS4-54268 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -