Thermodynamic dislocation theory: Size effect in torsion

The thermodynamic dislocation theory developed for non-uniform plastic deformations is used for the analysis of twisted copper wires. With a small set of physical parameters, assumed to be independent of strain rate and temperature, we can simulate the torque-twist curves that match the experimental ones of Liu et al. [2012]. It is shown that the size effect results from the nucleation and pile-up of excess dislocations. •The thermodynamic dislocation theory for polycrystalline copper wires undergoing torsion is proposed.•The torque-twist curves are simulated that agree with the experimental ones by Liu et al. [2012].•The size effect is caused by the nucleation and pile-up of excess dislocations.