Size effect on cyclic torsion of micro-polycrystalline copper considering geometrically necessary dislocation and strain gradient

To predict the cyclic plasticity behavior of polycrystalline copper on the micro scale for fully reversed torsion, a model, which expresses back stress in an Armstrong-Frederick form, is developed. The model parameters are size dependent and correlate with the critical density of geometrically necessary dislocations (GNDs). For monotonic loading, the flow stress satisfies the parabolic Taylor relation, and a mathematical equation is derived that...