Abstract
The development of planar anisotropy and the abrupt change in the mechanical properties of sheet steels (four Al-stabilized and one rimmed) due to the increase of prestrain are investigated in relation to the variation of crystallographic texture for different prestraining modes of uniaxial tension, biaxial tension, tension-compression, and bending-unbending.
The mechanical properties of those variously prestrained sheet steels may be explained more reasonably by employing the latent workhardening theory in a macroscopic deformation model having the active and latent slip systems resolved into width and thickness components in addition to the information from the variation of pole figure.
A concept of “re-formability”, the formability of prestrained sheet metal having a certain deformation texture developed in it, is proposed for more systematic understanding of press formability, where it is distinguished from the ordinary or primary formability of sheet metal in terms of the variation of deformation path from the first forming to the subsequent one.
The variation of mechanical properties including the r value during the first forming of monotonic deformation path is generally increased by increasing the difference in the mode of deformation between the first forming and the subsequent one, and also by increasing the difference between the strain ratio (r value) of the virgin material and that forcedly given in the first forming, that is, the difference between the preferred orientation of sheet metal and the stable end orientation in the forming.
