Numerical analysis of plastic deformation mechanisms in polycrystalline copper under cyclic loading with different frequencies

Abstract

The frequency of cyclic loading has a strong effect on the fatigue lifetime of materials. High loading frequencies allow reaching very high cycle fatigue regimes. The effects of cyclic loading with different frequencies are studied using the finite element method within the framework of crystal plasticity. The numerical study represents copper polycrystal that undergoes tension-compression loading with frequencies 80 Hz and 20 kHz respectively. The spatial distributions of stresses, strains, and plastic slip are used for estimation of volume fraction, morphology, and plasticity mechanism of persistent slip bands. The results show that at 80 Hz cyclic loading, plasticity in persistent slip band cells is dominated by the creation and annihilation of dislocations while at 20 kHz cyclic loading, plasticity is driven by the back-and-forth movement of dislocations inside the persistent slip band cells. The numerical study shows a correlation between amplitude and frequency of loading with spatial distribution and morphology of persistent slip bands that can be related to the fatigue lifetime.