STEADY-STATE CREEP CRACK-GROWTH BY CONTINUALLY NUCLEATING CAVITIES

For creep crack growths by the nucleation and growth of grain boundary cavities, steady-state crack growth rates (ȧ) are derived when the cavity nucleation is assumed to be continual and strain controlled. For the crack growth under HRR fields, a is linearly proportional to C* as reported in other models. However, when the crack growth occurs under elastic fields, a ̇K1 2 + 3n 5 (n > 8 3) for diffusional cavity growth and a ̇ ∼ Kn1 (n > 2) for cavity growth by power law creep. Predictions of the model are applied to a Ni-Cr steel and a Nimonic 80A, and compared with other models through analyses on the dependence of a on macroscopic load parameters and the activation energy of a. © 1989.