Simulation of the Behaviour of FCC Polycrystals during Reversed Torsion

Taylor-type polycrystal plasticity models with various single slip hardening laws are evaluated by studying the large strain behaviour of FCC polycrystals during reversed torsion. The hardening laws considered include an earlier model as well as a power-law and an exponential version of that, and a more recent model. The material parameters for the various hardening laws are fitted to experimental compression data for copper and then used to predict reversed large strain torsion of tubes. Differences under "free-end" (axially unconstrained) or "fixed-end" (axially constrained) conditions between predictions and experimental observations are discussed in detail. In addition to the torque response, the Swift effects upon twist reversal are studied.