Non-linear mechanical response of various metals. III. Swift effect considered in relation to the stress-strain behaviour in simple compression, tension and torsion

Abstract

For pt.II see ibid., vol.10, no.4, p.533 (1977). The correlation of the stress-strain behaviour in simple compression, tension and torsion is considered for various metals in relation to the Swift (1947) effect, here observed as the permanent lengthening of a tubular specimen along the principal axis about which it is being twisted. The proposed correlation is based on an incremental-type constitutive equation for an isotropic incompressible strain-hardening elastic-plastic solid with large deformation. Formulation of the proposed constitutive equation involves a modified Mises yield condition and the assumption that the total deformation gradient can be decomposed into a matrix product of the local elastic and plastic deformation tensors. Since the Swift effect appears to be absent at high strain rates, the metals of present interest should appear stronger at high strain rates, a conclusion in accord with the observation that the dynamic yield stress is frequently observed to be higher than the static yield stress in all three simple modes of deformation.