Determination of transverse mechanical properties from the ring type of specimens directly machined from the nuclear reactor pressure tubes is not straightforward because of the presence of combined membrane as well as bending stresses arising in the loaded condition.
In this work, ring-tensile tests were carried out on the unirradiated ring specimens using two split semi-cylindrical mandrels as the loading device. An inverse 3-D finite element (FE) analysis was carried out in order calculate the material stress-strain curve. The effect of geometry of the loading mandrel (i.e., 2-piece vs. 3-piece type of mandrel) on the load-deformation behavior of the test-setup has been studied.
It was observed that the values of maximum load as well as the deformation behavior in the post-necking region differ significantly when only the geometry of the loading-mandrel is changed keeping all the other parameters same. However, finite element analysis have been able to correctly predict these variations as it takes into account of the effect of geometry, material properties as well the interaction between the mandrel and the specimen. Hence, the use of finite element method is essential in the inverse analysis procedure where the material properties can be determined from these complex test-setups.

Keywords: Material stress-strain curve, Transverse mechanical properties, Finite element analysis, Zircaloy-2, Zr-2.5%Nb, Indian PHWR.