Multiscale analysis of defect initiation on the atomistic crack tip in body-centered-cubic metal Ta
H. B. Lu, J. W. Li, Y. S. Ni, J.-F. Mei and H.-S. Wang
Acta Physica Sinica, 60, 106101 (2011).

ABSTRACT
The quasi-continuum method (QC), a multiscale method, is used to analyze
body-centered-cubic (bcc) metal tantalum (tantalum, Ta) type II crack-tip
dislocation nucleation. Based on the relationship curves between dislocations
emission position and stress intensity factor, the processes of dislocation
defect initiation and development are investigated. Dislocation travels forward
with different characteristics in different stages and the new nucleated
dislocations expedite the already nucleated dislocation to move away from the
crack tip. The analysis of initiation of the crack tip defects shows that they
are the local defects that first appear, and with loading, more local defects
emerge, which eventually move to the boundary, and lead to the type If fracture.
Furthermore, dislocation dissociation as well as extended dislocation is
discussed. The partial dislocation nucleating before the perfect dislocation
nucleation and emission is full proof that the dissociation of perfect
dislocation takes place step by step, which means that the two minimum points on
the energy curve have different formation mechanisms.