Experience with compact tension specimens for creep crack growth measurements in weldments

Creep crack growth tests have been performed on CT specimens machined from weldments in 1/2Cr1/2Mo1/4V, P22 and P91 pipe sections. The test set-up and conditions need to be carefully considered to produce service representative damage. The pre-crack is best located in the specific HAZ sub-region of interest. As with conventional cross-weld creep testing of ferritic welds, temperature acceleration may be required if service-like damage is to be generated in short-term tests. Checks on the correpsondence between the experimental and theoretical values of C* demonstrate that consideration of primary creep and process zone transition times can be more important than HAZ creep properties variations.