Microstructure-based modelling of cast iron with lamellar graphite inclusions under cyclic plastic loadings

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Cast iron with lamellar graphite inclusions is used for many components that are exposed to low-cycle fatigue loading conditions. Thus, at highly loaded regions in the components cyclic plasticity occurs. It is the goal of the project to investigate the influence of the microstructure of the graphite on cyclic plasticity of cast iron with lamellar graphite inclusions. To this end, representative volume elements (RVEs) are analysed which are generated from 3D-reconstructions of the real microstructure. For different microstructures of graphite (distribution, size, portion) yield surfaces are numerically computed and their evolution under cyclic loadings is followed. Moreover, the corresponding flow directions are evaluated. The probabilistic nature of the microstructure is allowed for by analyzing, besides RVEs, many smaller, not-representative test volume elements (TVEs) which in their collectivity are statistically representative and allow an analysis of scatter and upper and lower bounds of yield loci. The findings should be used to formulate a material model for cast iron with lamellar graphite inclusions. In the future, it should be possible with this model to take the local material properties into account in the computational component design.