Abstract :
The author is involved in a wide-ranging
research programme, the objective being to extend the
fracture mechanics methodology for sharp cracks to
blunt flaws, so as to take credit for the blunt flaw
geometry. The approach is based on the cohesive
process zone representation of the micro-mechanistic
processes that are associated with fracture. An earlier
paper has derived a blunt flaw fracture initiation
relation which gives the critical elastic flaw-tip peak
stress rpcr (a ‘‘signifier’’ of a critical condition in the
process zone) in terms of the process zone material
parameters, subject to the proviso that the process
zone size s is small compared with the flaw depth
(length) and any characteristic dimension other than
the flaw root radius q. The relation has been derived
using a ‘‘two-extremes’’ procedure, whereby the separate
rpcr solutions for small and large s/q are blended
together to give an all-embracing relation that is valid
for all s/q. A key feature of the relation is that rpcr
essentially depends on only one geometrical parameter:
the flaw root radius q. Though the relation has
evolved from a consideration of the characteristics of
one model, i.e. that of an elliptical flaw in an infinite
solid that is subjected to an applied tensile stress, it is
anticipated that the relation can be applied equally
well for a wide range of geometrical configurations
involving different flaw shapes. It is against this
background that the present paper demonstrates that
the relation also applies to the behaviour of an
intrusion type flaw in the surface of a semi-infinite
solid subjected to an applied tensile stress
