Crack growth under primary and secondary creep conditions, numerical and experimental investigations

In the two alloys investigated, creep crack growth under steady-state conditions can be described by power laws using the C-Integral. The correlations are in agreement with theoretical considerations if plane-stress conditions are assumed. For both alloys, creep crack growth takes already place immediately after loading the fatigue-precracked specimens. Finite-element calculations on the basis of a Norton power law are, already, in good agreement with experimental results for stationary creep conditions. The use of an exponential fit, which considers stress dependence of Norton's creep exponent yields an even better description of the experimental results. The consideration of primary creep, in addition, leads to a realistic simulation of the transient region, the first time interval after loading of the specimen.