marginally lower crack growth in depth direction. In length direction
(Fig. 9(b)), both the schemes marginally underestimate the
crack growth. This marginal under estimation could be due to the
use of Paris constants evaluated from the 324 mm outer diameter
pipe which is of different heat.
Crack growth in depth direction for pipe weld SSPW 12-10 has
been shown in Fig.10. This figure indicates that scheme-C compares
well with experimental results and scheme-B resulted in over
estimation of crack growth in depth direction. Experiment and
analysis show that there is negligible growth along c-direction.
Crack growth in depth direction for pipe SSPB12-12 has been
shown in Fig. 11. The figure indicates that scheme-C compares well
with experimental results and scheme-B predicts marginally
higher crack growth in depth direction.
Crack growths in SSPW-6-1 pipe specimen having initial crack
aspect ratio as 2, are shown in Fig. 12(a) and (b). Before 2c/a equals
5, Fig. 12(a) shows almost no growth in depth direction and
Fig. 12(b) shows higher crack growth in circumferential direction.
This is apparent from curve between 2c/a and a/t also, as shown in
Fig. 13. Higher crack growth in length direction is due to the higher
stress intensity factor at the outer surface of the crack tip compared
to that of maximum crack depth. However, the crack growth rate in
length direction decreases with number of cycles.
Decrease in crack growth rate with increase in crack length
could be due to the stress concentration effect because of the
presence of geometrically smaller notch which leads to higher local
stress field at the notch tip. For geometrically smaller crack, the
local stress/strain field dominates the stress intensity solution. As