Abstract:

Short, microstructurally-sensitive crack growth in engineering alloys may contribute a significant fraction of fatigue life but is not yet fully mechanistically understood. Nucleation site, crack path tortuosity and rates of initiation and growth remain key questions to address and solutions at the microstructural length scale could offer the potential of substantive improvement in safety-critical component design.

In this presentation, studies based on integrated small-scale experiment, high-resolution characterisation and discrete dislocation and crystal plasticity modelling will be presented to address hypothesised aspects of the mechanistic bases of the above phenomena. Quantification of slip, lattice curvature and dislocation density, and stored energy density have provided insights in to strain localisation, crack nucleation site [1] and crack paths, and propagation rates in a range of engineering alloys [2]. As a particular example, the crystallographic nature of short crack growth in HCP zirconium alloy is addressed, and its relationship to slip activation and crack tip stored energy density considered by comparison of experimental measurements of crystallographic growth rates and crack paths with crystal plasticity modelling.

[1]  Nikoletta Prastiti et al. Discrete dislocation, crystal plasticity and experimental studies of fatigue crack nucleation in single-crystal nickel. Intl. Jnl. Plasticity, 126, 2020. https://doi.org/10.1016/j.ijplas.2019.10.003.

[2] Yilun Xu et al. Microstructural fracture mechanics: stored energy density at fatigue cracks. Jnl. Mech. Phys. Solids. 146, 104209, 2021. https://doi.org/10.1016/j.jmps.2020.104209.

Biography:

Professor Fionn Dunne researches in micromechanics of microstructure-level deformation and the mechanistic drivers of fatigue crack nucleation and growth, including Titanium cold dwell fatigue. A particular focus is bringing together quantitative characterisation (DIC and EBSD) with computational discrete dislocation and crystal plasticity. He was RAEng/Rolls-Royce Research Chair, Rolls-Royce Nuclear UTC Director, served on MOD’s Research Programmes Group, and currently on MPI's Intl. Sci. Advisory Board. He led the HexMat EPSRC programme grant (£5m), and is partner on the USAF MAI Dwell Programme. He was elected Fellow of the UK’s Royal Academy of Engineering in 2010, and awarded the IoM3’s Harvey Flower Prize 2016.

ALL INTERESTED ARE WELCOME