_3 ss ¼ Asn (4)
The general form between the creep crack growth rate (da/dt)
and the C* can be expressed by
da=dt ¼ B
h
C*
iq
(5)
where n is the creep exponent, and the B and q coefficients are
material constants, which are generally obtained from a regression
line of the CCGR data. They are related to the intercept and slope,
respectively, of the da/dt vs. C* relationship on a logelog plot. To
calculate the da/dt in Eq. (5), material data obtained in Table 2 were
used to calculate the C* values. The relationship between da/dt and
C* was obtained for all samples.
In the CT specimen, the C* valuewas calculated using Eq. (6), and
load-line displacement rate (V_ c) due to creep strain was calculated
by Eq. (8).