Simulation of torsion of thin FCC single crystal wires by mechanism-based strain gradient crystal plasticity1

摘要

The size effects observed in the torsion of thin FCC single crystal wires is modelled by the employment of mechanism-based strain gradient crystal plasticity (MSG-CP). In the formulation the total slip resistance in each active slip system is assumed to be due to a mixed population of forest obstacles arising from both statistically stored and geometrically necessary dislocations. The MSG-CP constitutive model is implemented into the Abaqus/Standard FE platform by developing the User MATerial subroutine UMAT. By implementing the formulation, the relationship between the non-dimensional torque and the surface strain of the thin copper single crystal wires of different diameters is obtained with the [001] direction along that of the wire axis. The simulation results of torsion reveal size effects, which is in a qualitative agreement with those reported in existing literatures. An appreciable axial elongation is also found in the torsion of single crystal wires.