Discrete dislocation modeling of fracture in plastically anisotropic metals

Fatigue crack nucleation: Mechanistic modelling across the length scales

“…In the single crystal analyses, the stress intensity was verified to be independent of the crystallographic orientation, but in the bicrystal study, the grain to grain influence was found to lead to a dependence of the stress intensity on the crystallographic orientation of the adjacent grain, as in [55]. The analysis of an edge crack in an hcp single crystal in [12] employs a 2D discrete dislocation modelling approach in which basal and pyramidal slip systems are incorporated and arranged in order to satisfy the plane strain requirement. The fracture toughness is found to be largely independent of the plastic anisotropy, as in the CP analysis in [56].…”

“…A particular advantage of the discrete dislocation technique is that it facilitates highly localised plastic strains, and hence the formation of PSBs which, in the main, higher-level techniques like crystal plasticity cannot capture. An example of the discrete dislocation calculation by Olarnrithinum et al [12] of slip band development in a 2D edge-cracked hcp single crystal allowing basal and pyramidal slip is shown in figure 3(b). However, a remaining limitation of the DD approach is its inability to capture core dislocation interactions, and some details of the structure of dislocation cells, ladders, veins and stacking faults applicable to low SFE materials.…”

“…~400 m Figure 3(c) Axial stress (left) and accumulated slip (right) calculated using the crystal plasticity approach of Sweeney et al [13] for a bcc ferritic steel polycrystalline notched beam for which the experimentally observed crack nucleation and growth have been superimposed. [12]. Dimensions shown are m.…”

“…Again, the highly localised slip observed demonstrates the difficulties for conventional crystal plasticity approaches but provides opportunities for discrete dislocation plasticity. Depres et al [29] have used DD to investigate slip localisation in single crystal 316 steel and have shown that highly localised slip bands are predicted to develop (similar to that of [12] shown in figure 3(b)), and that cross slip is an important mechanism. The work also shows that the DD technique leads to the prediction of intrusions and extrusions developing on the model sample free surface.…”

Strain hardening in 2D discrete dislocation dynamics simulations: A new ‘2.5D’ algorithm

“…The Peierls barrier for glide is usually neglected, which is reasonable for edge dislocations in FCC metals, but can be included when dominant (Olarnrithinun et al, 2013).…”