Effect of Swift effect in finite torsion deformation on torsion constitutive models

Abstract

The determination of large strain isotropic hardening elasto-plastic constitutive model was studied by using solid circular shaft torsion test when taking into account Swift effect of specimen which showed permanent axial length changes in torsion of a solid shaft with free end. Jaumann stress rate of Kirchhoff stress was employed in large strain constitutive model. The deformation rate and Jaumann stress rate were derived, respectively, for free-end torsion deformation and fixed-ends torsion deformation of a solid circular shaft in the large strain range, and the plasticity rigidity function of constitutive model was formulated by the aid of the true shearing stress-shearing strain relationship, axial elongationshearing strain relationship and axial normal stress-shearing strain relationship obtained from solid circular shaft torsion test. The results show that both the axial elongation in free-end solid shaft torsion and the axial normal stress developed in fixed-ends solid shaft torsion has an effect upon large strain constitutive models, and the margin of the effect is mainly related to the slope of axial extension rate-shearing strain curve, the axial normal stress value and the slope of axial normal stress-shearing strain curve.