Project title: Modelling methodologies for microstructure-sensitive crack growth in aero-engine PM Ni alloys
Supervisor: Dr Daniel Balint and Prof Fionn Dunne
A life-limiting factor of engineering alloys in service is the nucleation and growth of defects which sometimes originate from key microstructural features. The overall goal of this project is to develop a computational model to aid the mechanistic understanding of fatigue crack nucleation in engineering alloys by coupling Discrete Dislocation Plasticity (DDP) with high fidelity Crystal Plasticity (CP) modelling. This will lead to a mechanistic understanding of crack nucleation under cyclic loading regimes in PM Ni alloys. The role of geometrically necessary dislocations (GNDs) as precursors to fatigue crack nucleation will be understood, both by developing a method of quantifying GND development using discrete dsilocation plasticity, and by correlating GNDs to stored energy in the vicinity of suspected nucleation cites; the latter will be compared in turn to available experimental data in PM Ni alloys. The DDP model will be used to interrogate the dislocation structure, accumulated slip, stresses and the stored energy in the context of the experimental measurements, and compared with a corresponding crystal plasticity (CP) model in order to provide an underpinning understanding and assess if CP is an accurate representation of the process for use in industrial design.