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 - 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 - Baer, Wolfram A1 - Mayer, Uwe A1 - Weihe, Stefan ED - Vormwald, Michael T1 - Untersuchung des Master Curve-Konzepts für ferritisches Gusseisen mit Kugelgraphit: Kritische Belastungsrate und erste Ergebnisse an C(T)-Proben N2 - Im laufenden Verbundprojekt MCGUSS untersuchen dieProjektpartner MPA Stuttgart und BAM Berlin das probabilistische Master Curve (MC) Konzept nach ASTM E1921 hinsichtlich seiner Übertragbarkeit auf ferritisches Gusseisen mit Kugelgraphit (DCI). Ziel des Projektes ist die Entwicklung einer Methode zur Bestimmung und Bewertung der dynamischen Bruchzähigkeit von DCI im Übergangsbereich. In diesem Beitrag werden die Eigenschaften des verwendeten Werkstoffs der Festigkeitsklasse GJS-400 vorgestellt und die sich daraus ergebenden Probenentnahmestellen näher erläutert. Weiterhin werden erste Ergebnisse der C(T)25-Versuchsserien vorgestellt, die bei Belastungsraten von ca. 5∙103 MPa√ms-1, 5∙104 MPa√ms-1 und 5∙105 MPa√ms-1 und einer Temperatur von -40 °C durchgeführt wurden. T2 - 56. Tagung des DVM-Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Kassel, Germany DA - 20.02.2024 KW - Dynamische Belastung KW - Master Curve KW - Gusseisen KW - C(T)-Proben PY - 2024 SP - 37 EP - 47 PB - DVM Verlag CY - Berlin AN - OPUS4-59519 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Holzwarth, Marcel A1 - Mayer, Uwe A1 - Baer, Wolfram A1 - Weihe, Stefan 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 joint research project between MPA Stuttgart and BAM Berlin. According to Hojo et al. (2008) the MC concept is already in use for the brittle fracture safety assessment of ferritic forged steel containers, which would suggest an extension to ductile cast iron containers. In compliance with IAEA 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 exclusion of crack initiation. 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 only a low number of small fracture mechanics test specimens extracted from a component. For the experimental program, a DCI material of grade GJS-400 (GGG-40) has been produced as it is generally used for transport and storage containers for nuclear material. A basic mechanical-technological material characterization consisting of tensile, Charpy, and Pellini tests has been 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 at various loading rates and temperatures. The specimen testing is divided between the project partners based on specimen geometry. MPA Stuttgart has been tasked with the testing of the C(T), DC(T) and Pellini specimens, while BAM Berlin was assigned the SE(B), Charpy and tensile tests. These tests allow for the determination of the loading rate relevant for brittle fracture via C(T)25 specimens and an assessment of size effects by transferring the relevant loading rate to other specimen geometries and sizes. Numerical analyses of different specimen geometries and test setups are planned to investigate the influence of stress triaxiality and loading rate. Furthermore, the time-dependent course of the Weibull stress is assessed via these numerical analyses. Throughout the experimental program, the microstructure-property relationship will also be investigated based on quantitative metallographic and fractographic analyses like scanning electron microscope images and metallographic sections. With the acquired experimental database fundamental assumptions of the MC concept, like the weakest link model and the Weibull distribution, will be assessed for the application to DCI. In the end, the applicability of the MC concept will be evaluated and if necessary, modifications to the MC concept for DCI will be proposed. This paper will present the preliminary results of the GJS400 material characterization and the related selection of test specimen extraction points. First results of the C(T)25 and SE(B)140 specimen testing will also be discussed supported by first metallographic analyses. T2 - SMiRT27 Conference CY - Yokohama, Japan DA - 03.03.2024 KW - Ductile Cast iron KW - Dynamic Fracture Toughness KW - Safety Assessment KW - Master Curve Concept PY - 2024 SP - 1 EP - 10 AN - OPUS4-59302 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -