TY - CONF A1 - Holzwarth, Marcel A1 - Baer, Wolfram A1 - Mayer, Uwe A1 - Weihe, Stefan T1 - On the Applicability of the Master Curve Concept for Ductile Cast Iron based on experimental and microstructural results N2 - Based on the state-of-the-art research and regulations, the application of the fracture mechanics master curve (MC) concept to ferritic ductile cast iron (DCI) is being investigated in a joint research project (MCGUSS) between BAM Berlin and MPA Stuttgart. The experimental program included a basic mechanical-technological material characterization consisting of tensile, Charpy and Pellini tests. To determine the relevant loading rate for brittle fracture, instrumented C(T)25 fracture tests were performed at different loading rates at a temperature of -40°C. The relevant loading rates are 5x10^3 MPa√ms-1 and 5x10^4 MPa√ms-1. A series of dynamic fracture tests consisting of DC(T)9, C(T)25 and C(T)50 specimens were performed at MPA. BAM performed corresponding test series with SE(B)10 (pre-cracked Charpy), SE(B)25 and SE(B)140 specimens to cover the influence of specimen geometry. In total about 400 tests were performed during this project. The experimental program is complemented by extensive fractographic and metallographic studies using scanning electron microscopy and cross sectioning, as well as characterizations of the chemical composition of the material and of the morphology and distribution of the graphite particles. KJcd values were evaluated for all C(T)25 specimens and some C(T)50 and DC(T)9 specimens. First Master Curve analyses suggest that modifications on the Master Curve setup will be neccessary for instance changing the coefficient from 0.019 to 0.045. This modification requires further validation and is only one of many possible modifications. The SE(B) specimen results clearly show an inverse size effect. This does not correlate with the weakest link effect attributed to steels which dictates lower fracture toughness values for larger specimens. Due to the presence of graphite particles in the DCI material, it is currently assumed that these particles play a significant role in the failure behavior of DCI materials and the following fracture mechanism is proposed: “Specimen size-dependent arrest of local brittle fracures before global brittle failure by weakest link”. T2 - 9th SEDS Workshop: Safety of Extended Dry Storage, 20.-22. Mai 2025 CY - Garching, Germany DA - 20.05.2025 KW - Statistics KW - Dynamic fracture toughness KW - Ductile cast iron KW - Master curve KW - Safety assessment PY - 2025 SP - 1 EP - 3 AN - OPUS4-63566 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baer, Wolfram T1 - On the assessment of dynamic fracture toughness of ferritic ductile cast iron using the master curve concept N2 - An established and validated method to determine and assess dynamic fracture toughness values of ferritic ductile cast iron (DCI) in the ductile-to-brittle transition regime is currently not available. Although the ASME-Code, Sect. III, Div. 3, WC-2330 explicitly requires safety assessment considerations for dynamic loading, sufficiently substantial information on the procedure is not given. Therefore, the applicability of the probabilistic Master Curve (MC) concept according to ASTM E1921 to DCI is being investigated in the joint German research project MCGUSS conducted by BAM Berlin and MPA Stuttgart. Using a tailored manufacturing specification, a DCI material of grade GJS-400 has been casted to provide a test material which is very homogeneous but typical for heavy-sections. The experimental test program covers test specimens of various geometries and sizes (Tensile, Charpy-V, Pellini, SE(B)10, SE(B)25, SE(B)140, DC(T)9, C(T)25 and C(T)50). In total about 500 specimens will be tested to investigate and validate the Master Curve concept and its background for DCI (e.g. size effects, weakest-link, Weibull distribution, microstructure-property correlation). While the whole project has not yet concluded, several work packages have already been completed. This presentation is focused on dynamic large-scale fracture mechanics test series using SE(B)140 specimens and instrumented Charpy impact testing using ISO-V specimens. T2 - European Conference on Fracture 2024 CY - Zagreb, Croatia DA - 26.08.2024 KW - Dynamic fracture toughness KW - Ductile cast iron KW - Master curve concept PY - 2024 AN - OPUS4-61452 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baer, Wolfram T1 - Recent Results on the Investigation of the Master Curve Concept for Ferritic Ductile Cast Iron N2 - Within the current framework for safety assessment of ferritic ductile cast iron (DCI) containers for transport as well as interim and final storage of radioactive materials, the IAEA guidelines SSG 26 apply fracture mechanics principles. Crack initiation in either, stable or unstable modes is generally forbidden. Additionally, for DCI, the ASME-Code, Sect. III, Div. 3, WC-2330, explicitly requires a safety proof regarding dynamic loading conditions. Nevertheless, corresponding information given in the ASME Code does not seem to be sufficient to appropriately perform a dynamic fracture mechanics safety assessment for DCI. To address and improve this status of the dynamic brittle fracture safety assessment framework for DCI, the application of the fracture mechanics master curve (MC) concept to DCI is being investigated in an ongoing joint research project (acronym MCGUSS) between BAM Berlin and MPA Stuttgart. For ferritic DCI, the MCGUSS project addresses the currently lacking systematic review of applicability and potential modifications to the assumptions and the procedure according to ASTM E1921. The aim is to establish a methodology to determine and assess dynamic fracture toughness values of DCI in the ductile-to-brittle transition regime using small samples extracted from a component. The research approach and the planned investigations were outlined in more detail earlier. This paper is focused on the discussion of recent experimental results to establish the dynamic fracture mechanics toughness data base and its MC analyses. MCGUSS fracture mechanics test setups and the dynamic fracture toughness data base achieved at the time of abstract submission is discussed (covering 128 specimens). Current application limits of ASTM E1921 MC to DCI are discussed, and planned investigations to further investigate and modify the MC procedure for DCI are outlined. T2 - ASTM 23rd International ASTM/ESIS Symposium on Fatigue and Fracture Mechanics CY - Atlanta, GA, USA DA - 12.11.2025 KW - Dynamic fracture toughness KW - Ductile cast iron KW - Safety assessment KW - Master curve KW - Statistics PY - 2025 AN - OPUS4-64746 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Holzwarth, Marcel A1 - Baer, Wolfram T1 - Investigation of the Master Curve Concept for Ferritic Ductile Cast Iron N2 - The current framework for safety assessment of ferritic ductile cast iron (DCI) containers for transport and storage of radioactive materials applies fracture mechanics principles. As established by the IAEA safety standard SSG 26, prevention of crack initiation is the governing criterion and no reliance in design should be placed on any predicted ductile tearing resistance. Similarly, the ASME-Code, Sect. III, Div. 3 explicitly deals with DCI and requires a safety proof for dynamic loading conditions. However, information given in the guidelines does not seem to be sufficient to appropriately perform such dynamic fracture mechanics safety assessments. The ongoing German research project MCGUSS is tailored to tackle this status. In MCGUSS, the application potential of the probabilistic fracture mechanics master curve (MC) concept according to ASTM E1921 is being systematically investigated and potential modifications specific for dynamic brittle fracture of DCI will be identified. While MCGUSS covers testing of a high number of SE(B)- and C(T)-type specimens, this poster focuses on preliminary C(T) results. The obtained data was statistically analyzed, and current results of MC analyses are discussed. Special emphasis of MCGUSS is on using optical and scanning electron microscopy to link microstructural damage and failure processes to the fracture toughness data gained. A fracture mechanism called "specimen size-dependent arrest of local brittle fractures before global brittle failure by weakest link" is proposed to describe the established dynamic toughness data. Concerning the MC concept, it was shown that the ASTM E1921 procedure cannot simply be adopted to dynamic DCI toughness data on a one-to-one basis. Material specific modifications are being investigated and the DCI dynamic fracture toughness data base is to be expanded. T2 - MPA Conference 2025 CY - Stuttgart, Germany DA - 06.10.2025 KW - Dynamic fracture toughness KW - Ductile cast iron KW - Safety assessment KW - Master curve KW - Statistics PY - 2025 AN - OPUS4-64367 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Kiyak, Yusuf A1 - Breidung, Marc A1 - Baer, Wolfram A1 - Küppers, M. ED - Madia, Mauro T1 - Stiffness/constraint effects in analytical flaw assessment - A technical note N2 - Using the case study of a fail-safe design criterion for a steering knuckle of a commercial vehicle, the effect of stiffness/constraint on the crack driving force in the component is discussed. The problem arises when assessment procedures such as R6, BS 7910 or SINTAP/FITNET are applied in conjunction with substitute geometries for determining the model parameters K-factor and limit load (or a substitute for the latter), as it is common practice. In the example, the conservatism was so pronounced that this procedure was in fact unusable. A way out could be the finite element-based determination of the model parameters and their use in the analytical framework. This procedure is useful and effective if the finite element-based calculations are used in parameter sensitivity analyses. KW - Fail-safe design KW - Fracture resistance KW - Fracture assessment KW - Stiffness KW - Constraint PY - 2022 DO - https://doi.org/10.1016/j.engfracmech.2022.108728 SN - 0013-7944 IS - 273 SP - 1 EP - 15 PB - Elsevier Science CY - Kidlington AN - OPUS4-55544 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baer, Wolfram T1 - Was Sie schon immer über Chunky-Graphit wissen w(s)ollten, aber bisher nicht zu fragen wagten N2 - Duktile Gusseisenwerkstoffe mit Kugelgraphit (GJS) haben ein erhebliches technisches Potenzial und sind von wirtschaftlicher Bedeutung. Nicht zuletzt daher ist es ökonomisch sinnvoll, gesellschaftlich nachhaltig und wissenschaftlich interessant, ihren Herstellungsprozess zu optimieren. Eine maßgebliche Rolle kommt hierbei der Vermeidung von Qualitätsabweichungen in Form von Gefügefehlern zu. Dieser Beitrag befasst sich mit der – leider vielfach nicht richtig oder zu wenig verstandenen, aber insbesondere bei kostenintensi-ven dickwandigen Gussteilen relevanten - Graphitentartung Chunky-Graphit (CG). Die metallurgischen Ursachen von CG werden noch immer kontrovers diskutiert. Eine allgemein akzeptierte Theorie zur Bildung und dem Wachstumsmechanismus von CG existiert nicht, in der Gießereipraxis wird gleichwohl eine Fülle spezifischer technologischer Abhilfemaßnahmen praktiziert [1]. Der Schwerpunkt dieses Beitrages liegt jedoch nicht auf der metallurgischen Seite, sondern auf der Beschrei-bung der spezifischen Morphologie von CG (Bild 1), dessen Detektion im Werkstoff bzw. Bauteil sowie den Auswirkungen von CG auf die Werkstoffeigenschaften. Detailliert werden Möglichkeiten und Grenzen zer-störungsfreier und zerstörender Untersuchungsverfahren zur Identifikation und Quantifizierung von CG aufgezeigt. Ausgehend von der charakteristischen Morphologie von CG wird dessen Einfluss auf das Ver-formungs- und Bruchverhalten von GJS behandelt. Beispielhaft werden dabei die Eigenschaften Festigkeit, Verformbarkeit, das Risswachstumsverhalten und die Bruchzähigkeit diskutiert und Schlussfolgerungen für die Bewertung von mit CG behafteten GJS-Bauteilen abgeleitet. T2 - Ledebur-Kolloquium 2023 CY - Freiberg, Germany DA - 26.10.2023 KW - Gusseisen mit Kugelgraphit GJS KW - Chunky-Graphit KW - Graphitentartung KW - Duktiles Gusseisen PY - 2023 AN - OPUS4-58636 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baer, Wolfram T1 - Investigation of the Master Curve Concept for Ferritic Ductile Cast Iron (DCI) N2 - Based on state-of-the-art research and regulations, the application of the fracture mechanics master curve (MC) concept to ferritic ductile cast iron (DCI) is being investigated in a recently started German joint research project between BAM Berlin and MPA Stuttgart. This paper outlines the research approach and the planned investigations and provides first results. According to the IAEA guidelines SSG 26, the safety assessment of DCI containers for transport as well as interim and final storage of radioactive materials is based on the fracture mechanics criterion of general crack initiation exclusion. Within this context, the focus of the current research project is on the further development of brittle fracture safety assessment methods under dynamic loading conditions. Within fracture mechanics safety assessments for steels in nuclear technology, the probabilistic MC concept according to ASTM E1921 is currently used for quasi-static loading conditions as a supplement to the established deterministic ASME reference curve concept. The MC concept allows for an effective statistical consideration of the scatter of the material toughness in the transition regime. Furthermore, the MC can also be used for elevated loading rates as they occur in accident or crash scenarios. However, for DCI, a systematic review of potential modifications to the MC assumptions and procedure according to ASTM E1921 and an associated validation are still lacking. Therefore, a corresponding methodology shall be established to determine and assess dynamic fracture toughness values of DCI in the ductile-to-brittle transition regime, using samples extracted from a component. For the experimental program, a DCI material was produced as it is generally used for transport and storage containers. A basic mechanical-technological material characterization consisting of tensile, Charpy, and Pellini tests is planned. A comprehensive fracture mechanics test program was compiled covering dynamic testing of DC(T)9, C(T)25, C(T)50, SE(B)10, SE(B)25, and SE(B)140 specimens. Moreover, numerical analyses of different specimen geometries and test setups are planned to investigate the influences of stress triaxiality and loading rate. Throughout the experimental program, the microstructure-property relationship will be investigated based on quantitative metallographic and fractographic analyses. Finally, different MC assessment strategies will be considered, and modifications will be made if necessary. T2 - PATRAM22 Conference CY - Juans-les-Pins, France DA - 11.06.2023 KW - Dynamic Fracture Toughness KW - Ductile Cast Iron KW - Master Curve Method PY - 2023 AN - OPUS4-57766 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baer, Wolfram T1 - Aspekte der analytischen bruchmechanischen Bauteilbewertung N2 - Am Beispiel eines abgesetzten zylindrischen Bauteils (Achsschenkel) werden Probleme der analytischen bruchmechanischen Bauteilbewertung diskutiert. Als Basis-philosophie wird ein Fail Safe-Kriterium (kontrolliertes Versagen) angesetzt. Die Forderung ist, dass sich der Achsschenkel, bevor er bricht, in einem Ausmaß plastisch verformen kann, bei dem der Fahrer bemerkt, dass mit seinem Fahrzeug etwas nicht in Ordnung ist. Um das zu gewährleisten, muss der Werkstoff einen bestimmten Riss-widerstand aufweisen. Dazu werden im hier vorgestellten ersten Teil des Projektes mittels FEM Rissspitzenbeanspruchungen in Abhängigkeit von der Auslenkung des Zylinders und angenommener Rissgrößen ermittelt. Diese finden als Zielgrößen in der weiteren Analyse Anwendung. Da eine einfach umzusetzende Lösung angestrebt wird, werden zusätzlich analytische Rechnungen an Ersatzgeometrien (halbunendliche Platte und Vollzylinder), aber mit den realen Spannungen am Bauteil durchgeführt. Es zeigt sich, dass die Ergebnisse wegen des Steifigkeitsunterschieds zwischen Bauteil und Ersatzgeometrie unvertretbar konservativ sind. Alternativ wird ein hybrides Konzept vorgestellt, für das die Modellparameter mittels FEM bestimmt werden. Es liefert sehr genaue Ergebnisse. Im Rahmen der analytischen Rechenvorschrift können die Lösungen auf andere Werkstoffe übertragen werden, ohne dass zusätzliche FEM-Analysen notwendig sind. T2 - 54. Tagung des DVM-Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Online meeting DA - 22.02.2022 KW - Bauteilbewertung KW - Fail-safe KW - Analytisches Modell KW - FEM PY - 2022 AN - OPUS4-54408 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Holzwarth, Marcel A1 - Baer, Wolfram A1 - Mayer, Uwe A1 - Weihe, Stephan T1 - Investigation of the Master Curve Concept for Ferritic Ductile Cast Iron N2 - Within fracture mechanics safety assessment for steels in nuclear technology, the probabilistic master curve (MC) concept according to ASTM E1921 is currently used for quasi-static loading conditions as a supplement to the established deterministic ASME reference curve concept. However, for ductile cast iron (DCI), a systematic review of potential modifications to the assumptions and the procedure according to ASTM E1921 and an associated validation are still lacking. For this reason, the application of the fracture mechanics MC concept to ferritic ductile cast iron is being investigated in a recently started joint research project between MPA Stuttgart and BAM Berlin. According to the IAEA guidelines SSG 26, the safety assessment of DCI containers for transport as well as storage of radioactive materials is based on the fracture mechanics criterion of general crack initiation exclusion. Within this context, the focus of the current research project is on the further development of brittle fracture safety assessment methods. Therefore, a methodology shall be established to determine and assess dynamic fracture toughness values of DCI in the ductile-to-brittle transition regime, using samples extracted from a component. For the experimental program, a DCI material will be produced as it is generally used for transport and storage containers. A basic mechanical-technological material characterization consisting of tensile, Charpy and Pellini tests is planned and a comprehensive fracture mechanics test program was compiled covering dynamic testing of DC(T)9, C(T)25, C(T)50, SE(B)10, SE(B)25, and SE(B)140 specimens. Numerical analyses of different specimen geometries and test setups are planned to investigate the influences of stress triaxiality and loading rate. Throughout the experimental program, the microstructure-property relationship will be investigated based on quantitative metallographic and fractographic analyses. Finally, different MC assessment strategies will be considered and modifications will be made if necessary. T2 - 21st International Symposium ASTM/ESIS Symposium on Fatigue and Fracture Mechanics CY - Washington, DC, USA DA - 08.11.2023 KW - Ductile Cast Iron KW - Dynamic Fracture Toughness KW - Cleavage Fracture KW - Master Curve Concept PY - 2023 SP - 1 EP - 5 PB - ASTM International CY - West Conshohocken, PA AN - OPUS4-59064 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Holzwarth, Marcel A1 - Baer, Wolfram A1 - Mayer, Uwe A1 - Weihe, Stefan T1 - Master Curve-Auswertungen und Untersuchung des Größeneffekts für c(t)-proben - Aktuelle Erkenntnisse zur Untersuchung des Master Curve Konzepts für ferritisches Gusseisen mit Kugelgraphit bei dynamischer Beanspruchung N2 - Ausgehend vom Stand des Regelwerkes und der Forschung wird in einem BMUV-Verbundprojekt zwischen der MPA Stuttgart und der BAM Berlin die Anwendung des Master Curve (MC)-Konzepts auf ferritisches Gusseisen mit Kugelgraphit (DCI) untersucht. Ziel des Verbundprojekts ist die Anwendbarkeit des MC-Konzepts näher zu untersuchen und ggf. Modifikationen vorzunehmen, um eine Bewertungsmethode für die dynamische Bruchzähigkeit von DCI im Übergangsbereich zu erarbeiten. Auf den Jahrestagungen 2023 und 2024 des DVM-AK Bruchmechanik und Bauteilsicherheit wurden bereits der Forschungsansatz sowie erste Ergebnisse des Projekts MCGUSS präsentiert. Der Beitrag für die diesjährige Tagung soll nun MC-Auswertungen und den Größeneffekt für C(T)-Proben aus DCI diskutieren. T2 - 57. Tagung des DVM-Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Köln, Germany DA - 18.02.2025 KW - Versuche KW - Master Curve KW - Bruchmechanik KW - Dynamische Beanspruchung KW - Gusseisen mit Kugelgraphit PY - 2025 DO - https://doi.org/10.48447/BR-2025-495 SP - 123 EP - 129 PB - DVM-Verlag CY - Berlin AN - OPUS4-62555 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Holzwarth, Marcel A1 - Mayer, Uwe A1 - Baer, Wolfram T1 - Investigating the Applicability of the Master Curve Concept for Ductile Cast Iron – Early Results for 2 Different Test Temperatures N2 - Based on the state-of-the-art research and regulations, the application of the fracture mechanics master curve (MC) concept to ferritic ductile cast iron (DCI) is being investigated in a joint research project between MPA Stuttgart and BAM Berlin. This paper outlines the research approach, the planned investigations and first results of the experimental program. T2 - 8th SEDS Workshop: Safety of Extended Dry Storage CY - Garching, Germany DA - 15.05.2024 KW - Dynamic fracture KW - Brittle fracture KW - Ductile cast iron KW - Master Curve PY - 2024 SP - 1 EP - 4 AN - OPUS4-60013 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baer, Wolfram T1 - Statistische Auswertung der SE(B)-Bruchzähigkeitsdatenbasis und Untersuchungen zum Bruchmechanismus - Neue Ergebnisse zur Untersuchung des Master Curve Konzepts für ferritisches Gusseisen mit Kugelgraphit bei dynamischer Beanspruchung (Projekt MCGUSS) N2 - Die Zielstellung des laufenden Kooperationsprojektes MCGUSS zwischen der BAM Berlin und der MPA Stuttgart ist es, das probabilistische Master Curve (MC)-Konzept hinsichtlich seiner Übertragbarkeit auf ferritisches Gusseisen mit Kugelgraphit (DCI) zu untersuchen. Über Teilergebnisse der Arbeiten wurde bereits auf den Jahrestagungen 2023 bis 2025 des DVM-AK Bruchmechanik und Bauteilsicherheit berichtet. Der vorliegende Beitrag hat zwei Schwerpunkte. Zum einen wurde die Datenbasis der dynamischen Bruchzähigkeit für SE(B)-Proben der Dicken 10 mm, 25 mm und 140 mm auf insgesamt 101 Versuche bei Temperaturen von -40 °C bis -140 °C erweitert, statistisch ausgewertet sowie MC-Analysen unterzogen. Die Ergebnisse zeigen, dass die Daten sich zwar mit einer Weibullverteilung gut beschreiben lassen, die MC-Methode nach ASTM E1921 jedoch nicht ohne Weiteres anwendbar ist, sondern Modifikationen erforderlich sind. Des Weiteren werden neue Ergebnisse zum werkstoffspezifischen Bruchmechanismus bei dynamischer Belastung im unteren Übergangsbereich der Zähigkeit diskutiert. Die fraktographische Datenbank wurde durch REM-Analysen weiterer Bruchflächen von SE(B)25-Proben bei -40 °C, -60 °C und -80 °C ergänzt. Die Ergebnisse unterstreichen die prägende Rolle, die Rissarrestereignissen im Verlauf des dynamischen Sprödbruchversagens bei DCI zukommt. Der in MCGUSS zur Erklärung eines gegenüber Stahl inversen Probengrößeneinflusses vorgeschlagene Mechanismus „Specimen size-dependent arrest of local brittle fractures before global brittle failure by weakest link“ wird dadurch weiter unterstützt. T2 - DVM-Jahrestagung 2026 des Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Stuttgart, Germany DA - 24.02.2026 KW - Dynamic fracture toughness KW - Ductile cast iron KW - Safety assessment KW - Master curve KW - Statistics PY - 2026 AN - OPUS4-65593 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baer, Wolfram A1 - Ohm, Katrin A1 - Holzwarth, Marcel T1 - Statistische Auswertung der SE(B)-Bruchzähigkeitsdatenbasis und Untersuchungen zum Bruchmechanismus – neue Ergebnisse zur Untersuchung des Master Curve Konzepts für ferritisches Gusseisen mit Kugelgraphit bei dynamischer Beanspruchung (Projekt MCGUSS) N2 - Die Zielstellung des laufenden Kooperationsprojektes MCGUSS zwischen der BAM Berlin und der MPA Stuttgart ist es, das probabilistische Master Curve (MC)-Konzept hinsichtlich seiner Übertragbarkeit auf ferritisches Gusseisen mit Kugelgraphit (DCI) zu untersuchen. Über Teilergebnisse der Arbeiten wurde bereits auf den Jahrestagungen 2023 bis 2025 des DVM-AK Bruchmechanik und Bauteilsicherheit berichtet. Der vorliegende Beitrag hat zwei Schwerpunkte. Zum einen wurde die Datenbasis der dynamischen Bruchzähigkeit für SE(B)-Proben der Dicken 10 mm, 25 mm und 140 mm auf insgesamt 101 Versuche bei Temperaturen von -40 °C bis -140 °C erweitert, statistisch ausgewertet sowie MC-Analysen unterzogen. Die Ergebnisse zeigen, dass die Daten sich zwar mit einer Weibullverteilung gut beschreiben lassen, die MC-Methode nach ASTM E1921 jedoch nicht ohne Weiteres anwendbar ist, sondern Modifikationen erforderlich sind. Des Weiteren werden neue Ergebnisse zum werkstoffspezifischen Bruchmechanismus bei dynamischer Belastung im unteren Übergangsbereich der Zähigkeit diskutiert. Die fraktographische Datenbank wurde durch REM-Analysen weiterer Bruchflächen von SE(B)25-Proben bei -40 °C, -60 °C und -80 °C ergänzt. Die Ergebnisse unterstreichen die prägende Rolle, die Rissarrestereignissen im Verlauf des dynamischen Sprödbruchversagens bei DCI zukommt. Der in MCGUSS zur Erklärung eines gegenüber Stahl inversen Probengrößeneinflusses vorgeschlagene Mechanismus „Specimen size-dependent arrest of local brittle fractures before global brittle failure by weakest link“ wird dadurch weiter unterstützt. T2 - DVM-Jahrestagung 2026 des Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Stuttgart, Germany DA - 24.02.2026 KW - Statistics KW - Dynamic fracture toughness KW - Ductile cast iron KW - Master curve KW - Safety assessment PY - 2026 SP - 1 EP - 12 PB - DVM-Verlag CY - Berlin AN - OPUS4-65591 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo T1 - Low-Cycle Fatigue Behavior of Laser Powder Bed Fused Inconel 718 at Room and High Temperature N2 - The nickel-base superalloy Inconel 718 (IN718) is one of the most commonly used Ni-based superalloys for high temperature structural applications for its remarkable strength, as well as creep, fatigue, and corrosion resistance up to 650 °C. While IN718 has traditionally been employed as cast or wrought material, it is difficult to machine because of its high strength and toughness. The additive manufacturing of IN718 components made by metal AM has thus gained extensive attention to produce expensive near-net shaped components of high-temperature alloys such as IN718, for it saves material and costs in processing and machining steps. Among all metal additive manufacturing (AM) technologies, laser powder bed fusion (PBF-LB/M) is the most widespread, IN718 being one of the most common alloys produced with it. However, high cooling rates associated to the PBF-LB/M process, hinders the primary strengthening phases γ’’ and γ’ to form, as these cooling rates induce a dislocation cellular substructure, at which walls primary Laves phases bind segregating Nb, Ti and Mo. Many of the therefore needed heat-treatment strategies can then promote Laves-phase transformation into the stable δ phase along the cell and grain boundaries. Laves and δ phases, as well as grain-boundary primary carbides may have adverse effects on mechanical properties. The mostly needle-shaped δ phase was namely found to have a detrimental effect on creep rupture life while no direct effect on LCF fatigue life was evident. In this work room- and high-temperature (650 °C) low-cycle fatigue behavior of PBF-LB/M IN718 is investigated in the four-step heat-treated state and compared to wrought IN718. The microstructure of both materials is characterized across length scales via microscopy methods. The fatigue life at room temperature of the PBF-LB/M IN718 material is slightly lower than that for the wrought material, which is reversed at 650 °C. The cyclic stress response for both materials is marked by cyclic softening that is more pronounced at higher test temperatures. Multiple secondary cracks form at high strain amplitudes, at both room and high temperatures. High testing temperatures enhance specially crack formation at the transitions of regions between elongated grains and columns of stacked grains with ripple patterns in the PBF-LB/M material. Additional to this behavior, pronounced crack branching and deflection indicate that the cracks are controlled by sharp micromechanical gradients. T2 - EUROMAT 2025 CY - Granada, Spain DA - 14.09.2025 KW - Additive manufacturing KW - Low-cycle fatigue KW - Microstructural characterization KW - Ni-base superalloy PY - 2025 AN - OPUS4-64354 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mohr, Gunther T1 - R&D insights into sustainable additive manufacturing for high-temperature applications (HTA) N2 - Im Rahmen des AM Forums Berlin 2026 wird durch diesen Vortrag ein Einblick in FuE-Aktivitäten der BAM auf dem Gebiet der additiven Fertigung für Hochtemperaturanwendungen gegeben. Es werden dabei insbesondere Aspekte der nachhaltigen Verwendung von Pulverausgangswerkstoff und der Einfluss von Sauerstoff im Pulverwerkstoff auf die Degradation resultierender mechanischer Eigenschaften von Probekörpern beleuchtet. Die präsentierten Arbeiten sind im Rahmen des Pro FIT Projektes HTA2.0 entstanden. T2 - 10. AM Forum 2026 CY - Berlin, Germany DA - 10.03.2026 KW - Additive Manufacturing KW - Sustainability KW - Powder recycling KW - Powder degradation PY - 2026 AN - OPUS4-65725 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suarez Ocano, Patricia T1 - Effect of the powder composition on the microstructure and mechanical properties of 316L stainless steel fabricated by laser powder bed fusion N2 - Additive manufacturing (AM) has seen rapid growth in recent decades, with Laser Powder Bed Fusion (PBF-LB/M) emerging as the leading technique for producing high-density, geometrically complex metal parts. Austenitic stainless steel 316L is one of the most studied alloys for PBF-LB/M due to its excellent strength, ductility, and corrosion resistance [1]. The microstructure formed during PBF-LB/M processing can improve certain mechanical properties compared to conventionally manufactured 316L [2]. However, the current 316L standards allow broad ranges for key alloying elements, particularly Cr and Ni. While such variations have little effect on conventionally produced alloys, emerging evidence shows that they can markedly alter the microstructure and mechanical properties in PBF-LB/316L—even within specification limits [3]. This study investigates through microstructural and thermodynamical assessment, how two powders of nominally standard 316L composition (Alloys A and B) respond to identical PBF-LB/M processing parameters. Despite identical printing conditions, Alloy A exhibited twice the grain size and five times higher low-angle grain boundary (LAGB) density compared to Alloy B . Conversely, Alloy B showed a significantly higher density of Σ3 twin boundaries, nearly absent in Alloy A. These microstructural differences are attributed primarily to variations in Cr and Ni content in the liquid, which may influence icosahedral short-range ordering (ISRO) mechanism [4]. ISRO potentially facilitates twin boundary formation, ultimately refining grain structure [5]. This work highlights the critical impact of compositional control on final part microstructures and consequent mechanical properties and emphasizes the need to reassess compositional tolerances for AM-specific applications. T2 - 5th Symposium on Materials and Additive Manufacturing (Additive 2026) CY - Kassel, Germany DA - 24.03.2026 KW - Additive manufacturing KW - 316L stainless steel KW - Chemical composition KW - Lcosahedral short-range ordering mechanism KW - Grain size PY - 2026 AN - OPUS4-65738 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Raute, J. A1 - Schmidt, J. A1 - Bhadeliya, A. A1 - Rehmer, B. A1 - Olbricht, J. A1 - Jokisch, T. A1 - Biegler, M. A1 - Rethmeier, M. T1 - Investigation on seam quality and fatigue crack propagation in electron beam welded additive manufactured Inconel 939 N2 - Laser powder bed fusion of metals (PBF-LB/M) offers great potential for the production of new and spare parts for stationary gas turbines made of nickel superalloys such as Inconel 939 (IN939). In order to enable integration into existing assemblies and overcome design limitations, the additive manufacturing process chain must be expanded by suitable joining techniques. This study compares the electron beam welding of cast IN939 sheets and sheets produced additively using PBF-LB/M. The investigation focuses on the achievable seam quality with regard to geometric irregularities and internal defects in the form of liquation cracks on the microscale in the heat-affected zone. The evaluation of the welded samples shows no differences in the formation of the seam shape between the additively manufactured material and the cast material. For both materials, the highest quality category for beam-welded seams according to DIN EN ISO 13,919–1 was achieved at high welding speeds of 20 mm/s. Regardless of the manufacturing method, both materials show an increase in crack formation with increasing welding speed. However, due to its microstructure, the PBF-LB/M material exhibits significantly fewer microcracks overall. Final crack propagation tests on welded PBF-LB/M samples that were treated using HIP also show stable crack growth without sudden failure, which opens up potential for practical application. KW - Electron beam welding KW - Inconel 939 KW - PBF-LB/M KW - Liquation cracking KW - Fatigue crack propagation PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-657015 DO - https://doi.org/10.1016/j.jajp.2026.100389 SN - 2666-3309 VL - 13 SP - 1 EP - 10 PB - Elsevier B.V. AN - OPUS4-65701 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -