Abstract:
The ductile versus brittle fracture in crystalline materials depends on the
relative values of KIc and KIe as defined by well-known Rice theory, where KIc
and KIe are the critical values of stress intensity factor corresponding to
cleavage and dislocation emission, respectively. For KIc < KIe, the brittle
fracture (or cleavage) takes place in atomically sharp pre-cracked crystal
subjected to Mode I loading. For KIe < KIC, the dislocations are emitted from
the crack front resulting in ductile fracture. To this end, molecular static
simulations are used to explain the crystal orientation dependent fracture
behaviour of FCC single crystal and its contradiction with respect to Rice
theory based on stress triaxiality at the crack front. The stress triaxiality at
crack front changes with crystal orientation due to transformation of stiffness
tensor Cijkl. It is shown that high stress triaxiality suppressed the dislocation
initiation leading to cleavage failure even for the case when KIe < KIc.
