AN ALTERNATIVE ANALYTICAL APPROXIMATION OF THE C-T PARAMETER

The C-t parameter has proven very useful in correlations of creep crac k growth behaviour under both transient and steady state creep conditi ons. In this paper, we investigate the implications of adopting a diff erent definition of the creep zone based on an absolute measure of cre ep strain rather than a measure that is relative to the elastic strain . The analytical equations for small-scale creep and transition times from small-scale creep to extensive creep conditions are derived for t he C-t parameter using this alternative definition, considering both p rimary and secondary creep strain. It is shown that this alternative d efinition gives a reasonable starting point for the theory, approximat ely in accordance with the transient evolution of the C-t parameter ba sed on the more conventional definition of the creep zone, and removes the somewhat artificial limit of applicability imparted by the classi cal creep zone definition used in creep fracture mechanics. Accordingl y, diffusional creep processes with a power law exponent n less than o r equal to 3 are admitted in the C-t description.