Analysis of the inverse Swift effect using a rate-sensitive polycrystal model

Complementary to the Swift effect, namely the elongation of specimens during large strain elastic-plastic torsion with free ends, the inverse Swift effect refers to the free twisting of specimens during uniaxial tension after a previous large strain twisting history. In this paper, this intriguing phenomenon in solid cylindrical bars or wires is studied numerically using special purpose finite elements that allow for an accurate and efficient analysis of large strain torsion and simultaneous tension problems. The constitutive model used is a micromechanics polycrystal model based on a large strain crystal plasticity model accounting for rate-sensitive crystallographic slip in face-centered cubic crystals. The description of crystallographic texture development during all stages of the deformation process is inherent in the model. The influence of the material strain-rate sensitivity on the inverse Swift effect is investigated for varying amounts of shear strain imposed during pre-twisting. The simulations are compared with experimental results for copper wires reported in the literature. The marked sensitivity to initial textures as well as a number of constitutive assumptions are discussed in connection with the observed differences between theoretical predictions and experimental observations.