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

Microstructure-interacting short crack growth in blocky alpha Zircaloy-4

“…While no obvious surface evidence of prism slip was observed in Sample D, there was evidence of this slip system activation in Sample C which has similar crystal orientations (ie c-axes normal to loading). Independent modelling work [31,32] addressing both Ti and Zr alloy crack growth suggests that at the crack tip, prism slip can be the most favourable in these orientations and leads to crack growth within the prism planes. In addition, independent experimental evidence supports this for Ti, as reported in [31,32].…”

The dislocation configurational energy density in discrete dislocation plasticity

“…A quantity determined at the crystal plasticity length scale, but motivated by the idea that fatigue crack nucleation may be driven by dislocation configurational energy, was recently introduced and demonstrated to predict the fatigue crack nucleation sites in a range of alloys at the microstructural length scale [4,6,48] and to capture the microstructural sensitivity of fatigue crack growth [35,49,50]. Termed the stored energy density, this quantity assumed a small fraction (typically 5%) of the plastic work was stored in the form of dislocation structures (and hence the link to dislocation configurational energy) over a length scale given by the dislocation mean free distance, thus providing a local energy area density, given by = � :…”

Effects of Grain Size, Orientation, and Source Density on Dislocation Configurational Energy Density

“…The average dislocation spacing in the latter is shorter. Higher (positive) configurational energies are associated with earlier fatigue crack nucleation in crystal plasticity studies [9][10][11][12][13].…”

“…This term is different to the energy stored in the dislocation structure which also contains the dislocation self energy and core energy. The configurational energy density in DDP provides underpinning insight into the higher level crystal plasticity quantity called stored energy density [9] which has been demonstrated to capture accurately the site of fatigue crack nucleation [10], the cycles to crack nucleation [11], and the microstructure-sensitive growth paths [12] and rates of growth in BCC, FCC and HCP metals [13]. There are several modelling parameters in DDP which are potentially important in determining the plastic behaviour and hence the energy distribution.…”

“…The aforementioned studies indicate that the size effect is an important aspect in affecting the stress responses under various loading conditions. Hence it is important to study how it affects the configurational energy density which in turn underpins the crystal plasticity stored energy density demonstrated to be important in the nucleation and microstructurallysenstive growth of fatigue cracks [10,12,13,20].…”