Digital Repository, ECF14, Cracow 2002

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Investigations on the Dynamic Fracture Toughness Behaviour of Nodular Cast Iron

Last modified: 2013-02-10


Fracture mechanics characteristics of nodular cast iron are required forstructural safety analysis within the component design and for production control and qualityassurance programmes. In consideration of the specific demands required for heavy-sectionnodular cast iron, the fracture mechanics research programme of BAM is focused on anextensive material characterization under static and dynamic loading conditions with respectto such parameters as microstructure, test temperature, sample size and loading rate.Especially, the fracture toughness behaviour of nodular cast iron is strongly influenced bymicrostructural parameters like the pearlite content as well as size, morphology anddistribution of graphite nodules in the ferritic matrix.In the present study, nodular cast iron from an original thick -walled component with awide variety of microstructural characteristics was investigated in order to determine thefracture toughness characteristics under dynamic loading conditions in the temperaturerange from -50 °C to +22 °C using three-point bending specimens with thicknesses of140 mm and 15 mm, respectively. Dynamic crack resistance curves of SE(B)15 specimenswere determined in Charpy instrumented impact tests by applying the low-blow multiplespecimen technique. The fracture resistance curves are strongly affected by the pearlitecontent, as increasing pearlite content leads to a lower crack resistance. In comparison tostatic test results, an increasing loading rate leads to a higher transition temperature sothat the change from elastic-plastic to linear-elastic material behaviour in ductile cast ironis observed.

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