Fracture initiation and propagation along phase and grain-boundaries
Based on microstructural properties like grain size, orientation, inclusion distributions or other features a scheme is established to evaluate the cycle time to crack initiation of the material.
Starting with a model based on statistical information on the material’s microstructure and adding information about the material cyclic plasticity behaviour, the cycle time to crack initiation can be estimated. This is performed by the accumulation of irreversible strains, which are assumed to be the key parameter for fatigue crack initiation. Based on this model, changes in the microstructure will be linked to the cycle time to fatigue crack initiation so that the microstructure can be tuned in desired directions.
Starting with the prior austenite grain size distribution an RVE is built where the Kurdjumov–Sachs relationships are used for the subgrain lath structure. Based on this microstructure the proposed method will be used to study the accumulation of irreversible strains and to identify hot-spots for fatigue crack initiation. Successive investigations will focus on tuning the microstructure to avoid irreversible strain localization and thus extending the period to crack initiation of the microstructure.