Calibration of hoop stress in ring tensile test with Zircaloy-4 tube

Abstract

Since Zirconium (Zr) alloys have been widely used as cladding material in a nuclear fuel rod, material properties of Zr are essential in prediction of failure and undesirable deformation. This paper mainly concerns calibration procedure to obtain the hoop stress of Zircaloy-4 tube with a simple ring tensile (RTT) test linking with a Digital image correlation (DIC) technique since it is substantially difficult to obtain, directly, with specialized experiment such as burst test with internal pressure. The uniaxial tensile tests along the axial and RTT along the hoop directions were conducted with Zircaloy-4 tube in which anisotropic stains were analyzed with a DIC technique to validate appropriate deformation history. Anisotropic yield criterion based on the measured R-values (R-theta = 1.88 and R-z = 0.814) is able to capture the precise deformation mode in the ring tensile test. The flow curve along the hoop direction is calibrated by converting F, G, and H material parameters based on the R-values to the function of stress ratios.