A New Methodology to Evaluate High Temperature Mechanical Properties of Thin-Walled Tubes Using Ring Tension Specimen and Its Validation with Conventional Tests

The process of evaluation of mechanical properties of thin-walled small diameter tubes is cumbersome, especially, when the material exhibits significant anisotropy in the mechanical properties. For Zircaloy fuel clad tubes, the mechanical properties in the transverse or hoop direction are very different when compared to those along the length direction. As the diameter of the tubes is small, it is difficult to carry out conventional tensile tests and hence, ring tension tests are widely used. However, the ring tension test usually suffers from several drawbacks, such as the effect of friction between the ring and the loading mandrel on the stress-strain data and the existence of multi-axial state of stress in the gauge region. In this work, the effects of friction and state of stress have been taken into account in a new methodology, where the original load-displacement data is corrected for these effects using a correlation, which in turn has been derived from results of prior finite element analysis. The results of the new methodology have been validated by comparing data with those of conventional tensile tests. The new correlation has been used to evaluate transverse mechanical properties of Zircaloy-4 fuel clad over a wide temperature range, i.e., from 25oC to 900oC. This correlation has been used successfully for the first time in literature to evaluate the mechanical properties of Zircaloy-4 at such a high temperature environment. The data presented in this work is useful for safety analysts involved in simulation of severe accident progression and the correlation can be used to evaluate high temperature properties of similar thin-walled tubular components in industry.