Dynamic Fracture Toughness Tests Of Dynamically Loaded Ductile Cast Iron

For a complete review of component safety, especially under accident conditions where as a result of rupture load conditions, rapid changes of stresses and deformations occur. For this characteristic dynamic fracture material values are necessary in order to calculate the stress conditions and to determine the margins against brittle fracture. The structure of Ductile Cast Iron (DCI) has a significant influence on the fracture toughness values. For the experimental determination of dynamic fracture toughness values, the existing guidelines deliver only initial approaches; they are orientated on the rule for static tests. The paper describes an evaluation procedure that considers the influence of the structure on the behaviour of crack-propagation of Ductile Cast Iron at -40 °C regarding the experimental determination of dynamic R-curves, the definition of physical and technical crack initiation values and describes the influence of the graphite size, the correspondent ferrite grain size of the tensile properties and the fracture mechanic crack initiation values. The assessment of the micro-structural-dependent crack resistance behaviour at room temperature and at -40 °C was done on static and dynamic crack resistance curves using the J-Integral concept. In the discussion it is shown that for the static case, the model of growing porosities and for the dynamic load case the micro cleavage fracture stress can describe the material behaviour.