Load separability and ηpl factor determination for CT specimen of Zr-2.5Nb pressure tube material

Abstract

For fracture testing of pressure tubes, specimens are machined directly from the pressure tube without disturbing its curvature. The compact tension (CT) specimens thus obtained are called curved compact tension (CCT) specimens. Apart from being curved, the CCT specimens do not satisfy width/thickness criteria as mentioned in ASTM E1820-15. In spite of these differences, CCT specimens use the same ηpl and χpl factors as that of standard CT specimens for fracture toughness evaluation. In this work, 17 mm wide blunt notched CT specimens of different crack length obtained from a Zr-2.5Nb pressure tube, which were not meeting the thickness criteria, were used to investigate load separation and to evaluate the ηpl factor experimentally. Load separation existed between a/W of 0.45 and 0.70. The ηpl factor had a constant value of 2.078 in this range when calculated using the load separation method by power law fit. The ηpl factor calculated using a third order polynomial fit passing through the origin showed linear increase with b/W similar to but marginally lower than standard CT specimen.