Diffusion-induced stress concentrations in diffusional creep

Saša Kovačević

doi:10.1016/j.ijsolstr.2022.111440

2022-03-01

Saša Kovačević *

Sinisa Dj. Mesarovic

DOI：10.1016/j.ijsolstr.2022.111440

原文链接

查看原文

摘要

En 中文

The lattice continuum formulation for diffusional creep is implemented into the computational framework based on the finite difference method for space and the predictor-corrector algorithm for time discretization, to solve the coupled elasticity-diffusion problem with moving boundaries. The numerical scheme is implemented and tested considering 3D periodic structures without grain boundary sliding. Of primary interest in this paper are the stress non-uniformities resulting from nonuniform composition eigenstrains. We consider two regimes: the one where the rate limiting process is bulk diffusion of vacancies, and the one where the rate is controlled by vacancy nucleation/annihilation at grain boundaries (nucleation-controlled creep). We found that the stress concentration factor for diffusion-controlled creep is independent of the applied stress and grain size. No stress concentrations are present for the nucleation-controlled creep case. Stress and grain size dependence of minimum strain creep rates are determined by the present model for a variety of applied stresses, grain sizes, different driving processes (diffusion and nucleation-controlled creep) and compared with the classical theory for diffusional creep. We found that steady-state creep rates varied linearly with applied stresses for both diffusion and nucleation-controlled creep. The numerical results show good correspondence to analytical predictions for idealized diffusional Nabarro-Herring creep. Significantly lower steadystate strain rates were computed for nucleation-controlled creep. These results demonstrate the ability of the present model to reproduce the stress and grain size dependence of the steady-state strain creep rates.

Keyword:

Lattice continuum

Vacancy diffusion

Moving boundary problem

Stress concentration factor

Diffusion-controlled creep

Nucleation-controlled creep