Microstructurally-sensitive fatigue crack growth in HCP, BCC and FCC polycrystals

Microstructurally sensitive fatigue crack growth in four material systems with BCC, FCC and HCP crystallography was investigated through integrated crystal plasticity eXtended Finite Element (XFEM) modelling and experiment. The mechanistic drivers for crack path tortuosity and propagation rate have...

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Bibliographic Details
Published in:Journal of the mechanics and physics of solids 2019-05, Vol.126, p.204-225
Main Authors: Wilson, David, Wan, Weifeng, Dunne, Fionn P.E.
Format: Article
Language:English
Subjects:
Body centered cubic lattice
Crack propagation
Crack tips
Crystal plasticity
Crystallography
Face centered cubic lattice
Fatigue
Fatigue failure
Ferritic stainless steels
Finite element method
Fracture mechanics
Grain boundaries
Internal energy
Microstructural sensitivity
Nickel base alloys
Polycrystals
Short crack propagation
Short cracks
Slip
Superalloys
Titanium alloys
Titanium base alloys
Tortuosity
XFEM
Zircaloys (trademark)
Zirconium alloys
Zirconium base alloys
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Summary:Microstructurally sensitive fatigue crack growth in four material systems with BCC, FCC and HCP crystallography was investigated through integrated crystal plasticity eXtended Finite Element (XFEM) modelling and experiment. The mechanistic drivers for crack path tortuosity and propagation rate have been investigated and crack propagation found to be controlled by crack tip stored energy and the crack direction by anisotropic crystallographic slip at the crack tip. Experimentally observed microstructurally-sensitive fatigue crack path tortuosities and growth rates in titanium alloy (Ti–6Al–4V), ferritic steel, nickel superalloy and zirconium alloy (zircaloy 4) have been shown to be captured, supporting the underpinning mechanistic arguments. Very short crack growth is dominated by local slip, but with increasing length, crack tip stresses begins to predominate, increasing the availability of slip systems and giving smaller amplitude oscillations between slip systems. This leads to overall crack paths which are in fact crystallographic but which appear not to be. Key features of crack retardation at grain boundaries, changes in rate resulting from crystallography, and intragranular crack path deflections have been experimentally observed and captured.
ISSN:0022-5096
1873-4782
DOI:10.1016/j.jmps.2019.02.012