Advances in the R5 and R6 defect assessment procedures

The R5 and R6 defect assessment procedures address crack growth at high and low temperatures, respectively. These procedures continue to be developed. In R5, the methods for treating stress relaxation have been extended to combined primary and secondary stresses allowing for both creep deformation and crack growth. The transient crack tip field parameter C(t) has also been evaluated for combined primary and secondary loading allowing for plastic as well as creep deformation. In both cases, the results have been derived in terms of a reference stress and these are presented in the paper. Although the basic R6 procedures remain unchanged, revisions have been made to a number of the advanced approaches, including the treatment of constraint and the use of global limit loads. These revisions are described. Finally, the paper discusses how the advances in R5 and R6 are being incorporated in other procedures, including the British Standard Guide BS7910 and the FITNET procedure being produced by a European network. (authors)