Most client specifications now require CTOD values of 0.
In the HAZ, the variable nature of the material sampled under the fatigue pre-crack, results in a variable performance of CTOD values.
Inevitably, when an ECA is conducted, the requisite value of the longitudinal weld CTOD actually needed to ensure a safe design is usually very low; around 0.
It would appear that the "safe" approach is to determine the CTOD value required for the more critical girth weld, and impose this on the longitudinal weld at the same time.
A better solution would be to understand the factors that give the best possible performance in terms of CTOD.
As mentioned previously, a high CTOD requirement can drive the need for a SAW welding consumable that will deliver a high CTOD value, but that is more susceptible to hardening when being repaired or on interaction with the girth weld.
Another interesting feature of this method is that it allows determining the CTOD and the mean maximal stress in the ligament directly from the load-displacement curves.
They act as stress concentrators initiating damage, which lowers the critical CTOD, as indicated by the decrease of [[Delta].