A mechanistic based cavitation model that considers nucleation,
early-stage growth and sintering under creep-fatigue interaction is
proposed. The number density of cavities ρ and their evolution
during multi-cycle creep-fatigue loading are predicted. Both the cavity
nucleation and early-stage growth rates, controlled by grain boundary
(GB) sliding mechanism during the tension phase, are formulised as a
function of local normal stress σ. The cavity
sintering that occurs during the compression phase is described as a
function of σ, but the mechanism switches to
the unconstrained GB diffusion. By examining various load waveform
parameters, results provide important insights into experimental design
of studying the creep-dominated cavitation process under creep-fatigue
interaction. First, creep-fatigue test with initial compression will
promote higher ρ value compared to that with initial tension, if
the unbalanced stress hold time in favour of tension is satisfied.
Second, the ρ value does not have a monotonic dependence on
either the compressive hold time or stress level, because of their
competing effect on nucleation and sintering. Third, the optimum value
of stress variation rate exists in terms of obtaining the highest
ρ value due to sintering effect.
Modelling of cavity nucleation under creep-fatigue interaction
