Abstract
The results of a round-robin programme to evaluate crack-tip parameters such as K, C* and Ct for characterizing creep crack growth behaviour are presented. The programme was sponsored by the E24 Committee on Fracture Mechanics Test Methods of the American Society for Testing and Materials (ASTM). The tests were made on a 1Cr-1Mo-0.25V turbine rotor steel (ASTM grade A470 class 8) and included specimens of two thicknesses from the compact type (CT) and the centre crack tension (CCT) geometries. The test temperatures were 538°C and 593°C (1000°F and 1100°F). All tests were found to be in the extensive creep regime where the C*-integral and the Ct parameter are identical. It was shown that all creep crack growth data from CT specimens correlated uniquely with the C*-integral or the Ct parameter and no unique correlation was found between creep crack growth rate and K. The creep crack growth rates in 6.3 mm (0.25 in) plane-sided CT specimens were about two to three times slower than those in 25.4 mm (1 in) th...
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