Present study on FCG behavior in austenite SS pipes and pipe
welds can be summarized as
1) Fatigue crack growth rates of pipe (base) and pipe weld
(SMAW) differ significantly as brought out from CT specimen
tests.
2) Two schemes based on the evaluations of effective stress
intensity factors, result in marginally different fatigue crack
growth life predictions. Scheme-C based on KRMS gives
comparable resultsw.r.t. experiments whereas scheme-B based
on K at two points gives marginally conservative predictions.
These predictions have been validated with experiments on full
scale pipe welds for three cases.
3) Prediction of fatigue crack growth life for notched pipe welds
using Paris constants obtained for pipe (base metal) will lead to
non-conservative results. It is suggested that Paris constants for
actual product can be used for realistic fatigue crack growth
assessment.
4) Prediction using FCGR curve given in ASME Section XI is very
conservative for pipe (base) but compares well for pipe weld
(SMAW).
5) The final crack will have the notch aspect ratio nearly 3 irrespective
of the initial crack size and aspect ratio. This observation
is of high importance for demonstrating Leak-Before-
Break applicability of pressurized primary components of
Nuclear Power Plant.