Creep crack growth

On the background of the historical evolution of the subject area, the current knowledge on creep crack growth is reviewed. The discussion is grouped around the C-integral, which is the appropriate load parameter for describing creep crack growth in ductile materials. Crack growth by coalescence with grain boundary cavities is modeted and the lifetimes of cracked specimens are calculated by integrating the resulting laws for crack growth. Limitations to C-integral arise from the initial elastic-plastic material response, from primary creep, from cracktip blunting and from widespread cavitation damage. All these bounds are shown on a load parameter map. This is a diagram in the stress-time plane indicating the regimes in which different load parameters are applicable: K, for predominantly elastic deformation; J if plasticity plays a role; C-Integral for primary creep; and C-Integral for steady-state creep. Tertiary creep is included in a damage-mechanics analysis of creep crack growth. The final section discusses a few three-dimensional aspects of fracture mechanics in general and of creep crack growth in particular.