An evaluation of mechanical anisotropy of zircaloy using impression testing

Abstract

A knowledge of the mechanical anisotropy is important for predictability of dimensional changes and stability of fuel rods in service. In addition, the anisotropy parameters control formability and the ease with which Zircaloy tubing can be pilgered from tube-reduced extrusions (TREX). The mechanical anisotropy parameters are usually determined using tensile and internal pressurization tests while monitoring the biaxial (hoop and axial) strains; the parameters are evaluated INDIRECTLY from stresses and strains. We report here the application of the recently developed impression test method in evaluating these anisotropy parameters relatively more DIRECTLY from yield and flow stresses along the three orthogonal directions, namely axial, hoop and radial directions of the tubing. In addition, this type of testing can be made on relatively small specimens, which is of great advantage in investigating radiation effects on materials.