On pre-straining and the evolution of material anisotropy in sheet metals

Uniaxial tension tests have been carried out along different angles from the rolling direction for both as-received and pre-strained sheet. By comparing the differences in the flow stress vs. orientation curves between the as-received and pre-strained sheets, the effect of pre-straining on material anisotropy is studied. It is demonstrated that the conventional methodology for determining material anisotropy would overestimate the pre-straining effect and would result in a completely erroneous yield surface.