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The elastic strain ratios associated with specific ideal orientations as well as with particular experimental textures were derived from the second order Hill approximation. The single crystal elastic constants for pure aluminum and copper were used. Plastic strain ratios were then calculated for the experimental textures 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 Liiders 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 Liiders band propagation and to the evolution of the texture and not to the elastic-plastic transition.KEY WORDS: Texture, ODF coefficients, elastic anisotropy, plastic anisotropy, r-value, Ltiders bands. I INTRODUCTIONIt has been commonly observed that the conventional or cumulative plastic strain ratio rpi changes fairly rapidly during the initial stages of straining, finally adopting a near constant value at tensile strains of 15% or 20% (Welch et al., 1983;Daniel and Jonas, 1992). Such changes in r-value could have their origin in the difference between rel and rpt, where rel is the elastic strain ratio. However, it has recently been shown (Daniel and Jonas, 1992) that the evolution of r-value during the tensile deformation of steels is not primarily associated with the difference between rel and rnl although it may be affected by the propagation of Liiders bands. Instead, it appears to be a direct consequence of the evolution of the texture during the early stages of tensile deformation.Depending on the actual texture present in the sheet, as well as on the inclination O of the axis of the tensile specimen with respect to the initial rolling direction, the texture changes can lead to increases or decreases in r-value, as well as to the relative absence of change.The conclusions described above were based on crystal plasticity calculations and texture measurements carried out on bcc materials and on the occurrence of combined 110 <111> and 112 <111> slip. Of interest in the present investigation was the extent to which the general phenomenology outlined above applies to fcc metals such as aluminum, in which 111 <110> glide is taking place instead. It will be shown below that, while rel and rnl generally differ in fcc as well as bcc materials, the dependence of rnt on strain observed in samples of aluminum sheets is again related to Liiders band propagation and to texture evolution and not to the elastic-plastic transition.

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