Crack propagation during steady state creep

A model is proposed tor the steady propagation of a creep crack under steady state creep conditions. Creep is envisaged to take place everywhere in the solid, though higher creep rates at the crick tip lead to a local concentration of the creep strain. A critical local strain criterion is used to describe the condition for crack advance. Local damage is envisaged to accumulate at the crack tip as a result of, or in parallel with the creep strain. The model correctly predicts a dependence of crack propagation rate with the nett section stress varied to the power m, where m is the exponent of stress in the creep equation, for large values of m. An approximate dependence of propagation rate on the elastic stress intensity factor is also shown. Tnese predictions are in accord with experimental work.