This paper describes a preliminary examination of the effect of in plane co
nstraint on creep crack growth under widespread creep conditions using the
Q stress. Plane strain is assumed. Damage models for fracture of the proces
s zone based on both ductility exhaustion and stress rupture are shown to p
redict a variation of the crack growth rate with Q. Lower levels of constra
int lead to lower crack growth rates for a given C*. The results are used t
o outline a high temperature failure assessment diagram approach to constra
int dependent creep crack growth.