Size effect in cyclic torsion of micron-scale polycrystalline copper wires

Cyclic torsion of micron-scale polycrystalline copper wires was experimentally studied. It was found that cyclic hardening is more pronounced with larger strain amplitude under symmetric cyclic straining. The mean stress relaxation is accelerated with larger initial strain and smaller strain amplitude under asymmetric cyclic straining. Meanwhile, both sample size and grain size effects were observed. That is the mean stress relaxation increases...