Determination of Critical CTOD in X65 Grade Steel Using Circumferentially Cracked Bar

In oil and gas industry, structural integrity assessment design is based on the critical CTOD concept as parameter characterizing material fracture resistance. Several design codes provides indication about the geometry of laboratory samples (SENT and SENB) to be used for the determination of the critical CTOD in order to ensure the same loss of constraint as for the flaws in service conditions. Unfortunately, there is a number of situations where it is difficult or impossible to machine such geometry samples. The authors have investigated the possibility to use the circumferentially crack bar (CCB) as a possible alternative specimen geometry