A Comparison Between BS7448-CTOD and ASTM E1290-CTOD in Linepipes

ASTM E1290 previously used the plastic hinge model for the calculation of CTOD, but has changed its CTOD calculation to J-based conversion since 2002. In this study, the ratio of ASTM-CTOD to BS-CTOD was analytically predicted and experimentally evaluated in linepipes. It was demonstrated that the CTOD ratio changed according to CTOD itself, and took a minimum in a CTOD ratio curve. The minimum value of the CTOD ratio was lower than 1 for low yield-to-tensile ratios, but higher than 1 for high yield-to-tensile ratios. The CTOD ratio tends to be higher than 1 for high CTOD caused by plastic instability, but around or less than 1 for low CTOD possibly caused by brittle fracture in X65 and X80. A CTOD transformation equation, which was proposed by the authors, can transform BS-CTOD into ASTM-CTOD with reasonable accuracy.