Anisotropy of yielding in a Zr-2.5Nb pressure tube material |
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Authors: | N Christodoulou M Resta Levi P A Turner E T C Ho C K Chow |
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Affiliation: | (1) Deformation Technology Branch, the CRL, AECL, K0J 1J0 Chalk River, ON, Canada;(2) Materials and Mechanics Branch, the CRL, AECL, K0J 1J0 Chalk River, ON, Canada;(3) IFIR, 2000 Rosario, Rosario, Argentina;(4) the Zirconium Metallurgy Department, Ontario Hydro Technologies, M8Z 5S4 Toronto, ON, Canada;(5) the Fuel Channel Engineering Branch, AECL, L5K 1B2 Mississauga, ON, Canada |
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Abstract: | The anisotropy of yielding, as measured by the ratio of yield stress in the axial and transverse directions of Zr-2.5Nb pressure
tubes used in Canada Deuterium Uranium (CANDU) nuclear reactors, was determined experimentally by testing samples in uniaxial
tension. The yield anisotropy was measured in uniaxial tension in samples obtained from the three directions of a Zr-2.5Nb
plate and in shear, by testing in torsion “mini” pressure tubes from the same material. From these experiments, the temperature
and strain-rate dependence of the yield stress and the dependence of the anisotropy of yielding on temperature were also determined.
It is shown that the yield anisotropy of pressure tube material is constant for temperatures up to about 800 K and that the
strain-rate sensitivity is also constant up to about 700 K and is equal to ∼0.02. In addition, the activation energy (Q) of this material was estimated by using the temperature dependence and rate sensitivity of the yield stress. It was found
to be of the same order of magnitude as that determined earlier by other investigators. A polycrystalline, nonlinear self-consistent
model that takes into account the crystallographic texture of the material was used to derive the values of the critical resolved
shear stress (CRSS) which are consistent with prismatic, basal, and pyramidal glide and the values of the Hill’s plastic anisotropy
coefficients which are consistent with the observed anisotropy of yielding. The model provided an estimate of the complete
stress tensor, describing yielding of a Zr-2.5Nb pressure tube material. |
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