On the subsequent yielding of an aluminum alloy following cyclic prestraining

Abstract

Thin-walled tubular samples of 6061 aluminum alloy are cycled in the axial direction between reversed stress limits until a steady-state condition is achieved. Following cyclic loading, the samples are subjected to internal pressure to determine the subsequent hoop tensile yield strength. A small-offset definition of yield is employed to relate the onset of plastic flow to dislocation processes. Samples in the -T651 and -0 tempers are studied, and, it is found that the subsequent yield strength determined in this way may be greater than, less than, or nearly equal to the initial hoop tensile yield strength depending on the interaction of three factors: i) the relationship between the Bauschinger effect and the cross effect under plane, biaxial stress loading, ii) the initial state of the material (i.e., degree of initial anisotropy), and iii) the final state of the material after axial cyclic loading (i.e., dislocation structure and deformation history).