Micromechanical Modelling of the Damage and Toughness Behaviour of Nodular Cast Iron Materials

The strength and toughness of nodular cast iron materials is described by a micromechanically based damage model for porous plastic materials. Two ferritic nodular cast iron materials of the type GGG-40 with different graphite morphology are investigated. Quantitative metallurgy and cell model calculations are used to determine the characteristic parameters of the Gurson-Tvergaard-Needleman-model (GTN-model). The stress strain behaviour of the matrix is obtained from tensile tests on a pure ferritic material. The influence of stress triaxiality and void shape on the critical void volume fraction is studied. Tensile tests with smooth and notched specimens are simulated to verify the load-deformation behaviour. The effect of the graphite morphology on fracture toughness is studied by tests and simulations of SE(B)-specimens.. Fracture resistance curves can be well predicted. A correlation between element size and particle distance is found