Modeling of cavity nucleation, early-stage growth, and sintering in polycrystal under creep-fatigue interaction

A mechanistic-based cavitation model that considers nucleation, early-stage growth, and sintering under creep-fatigue interaction is proposed to predict the number density of cavities rho. Both the nucleation and early-stage growth rates, controlled by grain boundary (GB) sliding under tension, are formulized as a function of local normal stress sigma(n). Cavity sintering that occurs during the compression is governed by the unconstrained GB diffusion depending on the sigma(n). Modeling results provide important insights into experimental load-waveform design. First, test with initial compression promotes higher rho compared to the initial tension, if the unbalanced hold time in favor of tension is satisfied. Second, the rho value does not have a monotonic dependence on either the compressive hold time or stress, because of their competing effect on nucleation and sintering. Third, the optimum value of stress variation rate exists in terms of obtaining the highest rho value due to sintering effect.