Anisotropy and the Bauschinger Effect in Cold Rolled Aluminium

Abstract

The paper deals with a study of the development of anisotropy and the Bauschinger effect in cold rolled aluminium. In the first instance, the development of a yield criterion considering both of these phenomena is discussed. By following a recent development by Yoshimura, a criterion involving only two parameters, one for anisotropy and the other for the Bauschinger effect, is developed. Considering the simple homogeneous rolling deformation model of Orowan, the yield criterion is applied to the case where cold rolled metal is subsequently tested in tension and compression at various orientations. Experimental procedures are described and the method of correlating the experimental results with the yield criterion is discussed. As a result of the analysis of the experimental results, it may be concluded that the yield criterion provides satisfactory correlation with experiment. The anisotropy parameter and a Bauschinger modulus are then specified in terms of rolling strain and the order of their magnitude considered. The last part of the paper is concerned with a discussion of additional factors which have a bearing on the results obtained. In the first place, the question of inhomogeneous deformation is considered. One of the consequences, the development of residual stresses, is shown to have little effect. However, additional evidence shows that the mode of deformation exerts a considerable influence on the Bauschinger modulus. It is concluded that anisotropy is probably not greatly influenced by the details of deformation, but the manifestation of the Bauschinger effect certainly is.