Anisotropic hardening theory and the Bauschinger effect

Abstract

A review of anisotropic hardening theory is presented with particular reference to the Bauschinger effect in reversed torsion and anisotropic yield loci in σ, τ space associated with plastic shear strain history.

The Bauschinger effect is obtained experimentally from a series of torsion tests on En3B steel tubes prestrained to a maximum of 10 per cent plastic shear strain. The effect, measured from the stress in reversed torsion at the proportionality limit, is analysed from the theory. It is shown to be consistent with experimental observations made on the translation and contraction of an initial yield locus, that are in marked contrast to the rigid translation of kinematic hardening rules.

The degree of shear prestrain is shown to considerably influence the magnitude of the effect, an observation in full support of a theoretical Bauschinger parameter. The present test data together with existing published data for commercially pure aluminium 1100-F and the aluminium alloy Noral 19 S confirm that the controlling parameter is a scalar coefficient of plastic prestrain. The investigation supports a scalar function that is parabolic in the second invariant of plastic prestrain.

The effect of yield point definition is examined and a comparison between theoretical and experimental yield loci is presented.