Evolution of anisotropy under plane stress

Yield loci have been measured for cold rolled steel sheets prestrained by two stage loading. During the first loading, the sheets have been stretched by 3 and 6% tensile strain in the rolling direction. The second loading was at angles to the rolling direction with varying amounts of tensile strain. Then a set of tensile test specimens has been prepared from each of the prestrained sheets. From tensile tests, effects of the two-stage prestrains on the subsequent yielding has been investigated. Experiments show that initial orthotropic symmetry is maintained and that the orientations of orthotropy axes change continuously throughout the prestraining process. A simple phenomenological rule for the rotation of orthotropy axes is suggested.