Modelling of microstructure-sensitive short fatigue crack propagation in Zircaloy-4: influence of microstructure, hydrides, and irradiation

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Rates of fatigue crack growth (FCG) and crack paths in Zircaloy-4 are highly microstructurally sensitive and dependent upon texture. This work is aimed at gaining mechanistic understanding of these microstructural effects. Crystal plasticity finite element modelling with the eXtended Finite Element Method and a stored energy density (SED) fracture criterion is used to simulate crack propagation in polycrystalline microstructures for comparison with experimental data. A new analytic solution for FCG rate is developed, facilitating rapid estimates. The model is based on a SED fracture criterion but is linked with classical fracture mechanics, enabling crack tip SED calculations at higher rates. Other work which is underway is aimed at capturing irradiation effects on short FCG rate. Dislocation channel clearing is being investigated in the presence of a crack. Additional experimental work is aimed at understanding the influence of hydrides on short FCG in Zircaloy-4. The first of a series of studies has begun. Lastly, studies will be carried out which will link previous work. The first aim will be to simulate previously mentioned experiments from incorporating the delta-hydride phase. The second aim will then be to incorporate the irradiation damage model for a theoretical assessment of irradiation damage on hydrided Zircaloy-4.