CREEP MODELING USING SEMIEMPIRICAL DEFORMATION AND DAMAGE EQUATIONS - FCC METALS

A scheme is presented for describing the creep behaviour of f.c.c. metals by combining semiempirical equations modelling deformation behaviour and damage accumulation. Deformation is described in terms of the Dorn equation which has been modified by assuming that the activation energy for creep (i.e. that the probability that a climb event occurs) depends on the applied stress and on the structure, a measure of the latter being the accumulated strain. This models hardening behaviour and leads to a falling strain rate with increasing time or strain. Tertiary creep is described in terms of the increase in applied stress which occurs owing to damage accumulation with time. In terms of the scheme, steady state creep does not occur but the creep rate may remain approximately steady over a time interval during which hardening and damage accumulation effects combine suitably.