Yield loci of Zircaloy tubing with different textures

Improvement of Yield Locus Calculation From Pole Figures of Zircaloy Tubes

“…From the calculated yield loci it can be concluded that different twinning systems depending on the orientation and stress condition are activated (Dressier et al 1973). Indirect confirmation of this conclusion could so far be obtained only from the asymmetry of the complete yield locus derived by experiments (Dressier et al 1974) and from the qualitative agreement between calculated and measured yield loci (Dressier et al 1972, 1973. Dressier and Matucha 1977, Matucha 1978).…”

“…These tubes show due to their production route marked anisotropy under two-axial stresses. Plane-stress measurements resulted in yield loci having different shapes compared with the v. Mises ellipse (Mehan 1981, Miller and Swota 1963, Dressier et al 1972. Texture was found to be the primary cause for anisotropic elasticity and yielding (Dressier et al 1972, Dressier et al 1973 1974, Dressier and Matucha 1977).…”

“…However, an attempt to calculate the yield loci of Zircaloy tubes from their texture in a similar way as it had proved successfully for fcc metals and alloys, ran into difficulties because mechanical twinning has to be considered in addition to slip as further crystallographic deformation mechanism active already at the onset of plastic flow. These problems could largely be overcome if, considering the unipolar deformation, the twin systems were formally treated as slip systems, and certain conditions appropriate to the experimental yield loci were assumed for the critical resolved shear sthresses (CRSS) of prismatic slip and twinning (Dressier et al 1972(Dressier et al , 1973.…”

“…A semiempirical yield lines model for the yield locus of Zircaloy-4 tubes was proposed by Ciurchea (1985) using the C2 coefficient found from the {10il}-pole figure. To fit the experimental yield loci of Dressier et al (1972Dressier et al ( , 1973) specific rotation angles of the deformation systems, measured yield strengths in the axial and tangential directions and the C2-coefficient of the cold worked specimen determined by Ciurchea (1985) were used. Due to the fit procedure the agreement of experimental and fitted data was good, although the real textures of the tubes were not taken into account.…”

“…This phenomemon was used to estimate the ratio of the CRSS by comparison with experimental yield loci leading to the ratios of CRSS for {li00}slip, {10i2}-, {11.1}-, {ll.2}-twinning of 1" 1.25" 1.35" 1.4 resp. (Dressier et al 1972(Dressier et al , 1973). For these ratioswhich were used in Figure 4---the intersection with the positive or-axis is defined by prismatic slip for tilt angles of the basal pole y 0 to 30.…”