Accounting for the recoverable plasticity and size effect in the cyclic torsion of thin metallic wires using strain gradient plasticity

摘要

The Bauschinger effect (BE), i.e. asymmetric plastic flow, and partial recoverable plasticity were observed in both copper and gold polycrystalline wires under cyclic torsion tests. These experiments provide a direct evidence for a class of strain gradient plasticity theories involving both energetic and dissipative length scales. Systematic experimental observations imply that the geometrically necessary dislocations (GNDs) induced by the plastic strain gradients give rise not only to the size effect, but also to the Bauschinger effect and plastic strain recovery at small scales. The back stress generated from the long-range interaction of GNDs plays an important role in the asymmetrical plastic flow. The observed anomalous plasticity in cyclic torsion is interpreted in the light of a strain gradient plasticity involving both energetic and dissipative length scales.