Material response, localization and failure of an aluminum alloy under combined shear and tension: Part II analysis

Abstract

The responses of the tubular specimens loaded under combined tension and torsion in Part I exhibited limit load instabilities followed by extensive localized deformation prior to failure. The present manuscript outlines an analytical framework that aims to establish the extent to which plasticity can reproduce the measured responses up to the onset of failure without the introduction of damage-induced softening effects. The analysis incorporates a suitably calibrated non-quadratic anisotropic yield function, a material hardening response extracted to large strains from a simple shear test, and a finite element model with refined 3-D elements. The analysis successfully reproduces the shear and axial stress levels during the homogeneous deformation parts of the response, the stresses and deformations at the load maxima, and the parts with decreasing stress associated with localized deformation. Furthermore, the geometry of the necked zones and the rapid growth of strain inside them are reproduced to levels that correspond to the recorded failure strains. Critical aspects of this successful effort are the non-quadratic anisotropic yield function and the material hardening adopted. It is concluded that the framework developed, combined with a suitable failure criterion based on results like those in Part I, constitute a viable tool for establishing the end of life of structures in engineering practice.