On the influence of steel microstructure on short crack growth under cyclic loading

The fatigue behaviour of microstructurally short cracks in a structural steel was experimentally characterised. The so-called load increasing testing technique was applied on notched bending specimens and allowed for initiation of short micro cracks. Propagation of these cracks was observed and analysed using light optical and scanning electron microscopes in defined intervals of load cycles. A 2D mechanism-oriented model to simulate the fatigue growth of micro cracks is presented. The bulk material is discretised by extended finite elements which allow for crack initiation and propagation along an arbitrary, solution-dependent path. The two-phase microstructure morphology and the elastic crystal anisotropy in the neighbourhood of the crack are considered. An overview of the strategy for analysis of the influence of several microstructural features on fatigue damage development using the presented model is given.