SYMPOSIA PAPER Published: 01 January 1996
STP16181S

A Unified Model to Describe the Anisotropic Viscoplastic Behavior of Zircaloy-4 Cladding Tubes

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This paper presents the constitutive equations of a unified viscoplastic model and its validation with experimental data. The mechanical tests were carried out in a temperature range of 20 to 400°C on both cold-worked stress-relieved and fully annealed Zircaloy-4 tubes. Although their geometry (14.3 by 1.2 mm) is different, the crystallographic texture was close to that expected in the cladding tubes. To characterize the anisotropy, mechanical tests were performed under both monotonic and cyclic uni- and bi-directional loadings, i.e., tension-compression, tension-torsion, and tension-internal pressure tests. The results obtained at ambient temperatures and the independence of the ratio Rp = εp θθp zz. with respect to temperature would seem to indicate that the set of anisotropy coefficients does not depend on temperature. Zircaloy-4 material also has a slight supplementary hardening during out-of-phase cyclic loading.

We propose to extend the formulation of a unified viscoplastic model, developed and identified elsewhere for other initially isotropic materials, to the case of Zircaloy-4. Generally speaking, anisotropy is introduced through fourth order tensors affecting the flow directions, the linear kinematical hardening components, as well as the dynamic and static recoveries of the forementioned hardening variables. The ability of the model to describe all the mechanical properties of the material is shown. The application of the model to simulate mechanical tests (tension, creep, and relaxation) performed on true CWSR Zircaloy-4 cladding tubes with low tin content is also presented.

Author Information

Delobelle, P
Laboratoire de Mécanique Appliquée R. Chaléat, U.A. CNRS, UFR Sciences, BESANCON, France
Robinet, P
Laboratoire de Mécanique Appliquée R. Chaléat, U.A. CNRS, UFR Sciences, BESANCON, France
Bouffioux, P
Electricité de France, Direction des Etudes et Recherches, MORET/LOING, France
Geyer, P
Electricité de France, Direction des Etudes et Recherches, MORET/LOING, France
Le Pichon, I
Electricité de France, Direction des Etudes et Recherches, MORET/LOING, France
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Developed by Committee: B10
Pages: 373–393
DOI: 10.1520/STP16181S
ISBN-EB: 978-0-8031-5343-1
ISBN-13: 978-0-8031-2406-6