Evolution of r-Value During the Tensile Deformation of Aluminium

The elastic strain ratios associated with specific ideal orientations as well as with particular experimentaltextures were derived from the second order Hill approximation. The single crystal elastic constantsfor pure aluminum and copper were used. Plastic strain ratios were then calculated for the experimentaltextures using the FC (full constraint), RC (relaxed constraint) and LW (least work) crystal plasticity codes. Tests were also carried out to determine the r- values along various directions in the sheet during Lüders band propagation, as well as the dependence on strain of the plastic r- value. It is shown that the observed strain dependence of the r- value is related to Lüders band propagation and to the evolution of the texture and not to the elastic-plastic transition.