Revolution of Principal Axes of Plastic Anisotropy Developed during Deformation Process

The anisotropies of sheet metals originate from the texture developed by a cold rolling process. In the texture, the crystal grains assume a partial direction, and so the strength of the texture is different from that of the surrounding material. When the sheet metals are deformed with changes of the strain path, the difference in strength produces a new texture and defines a new anisotropic principal axis. Therefore, it is supposed that the principal axis of anisotropies does not behave like the material fiber printed on the sheet metals. To confirm the above assumption, a measuring method of revolution angles of principal axes is proposed by using a laser speckle surface strain meter. The revolution angle is measured by investigating the distribution of r-values with respect to the tensile directions. Finally, a dynamical revolution model of the principal axes is derived and its parameters are identified.