4. Model
applications
4.1 Nucleation incubation
time
An incubation time is required to nucleate cavities 5.
The underlying mechanism is the time consumed for vacancies gathering
into the nuclei to form a stable cavity 40. In our
model predictions, there is a threshold value oft t for creep-fatigue tests without applying
compressive stress hold (t c=0 s), Fig. 7a. This
can be considered as the equivalent nucleation incubation time. Fig. 10
presents the calculated values for Type 316 stainless steel under
compressive/tensile stresses of (in MPa): -150/+150, -100/+150, and
-150/+100 at different temperatures. The increase of temperature by 50
˚C reduces the incubation time more than one-half. This agrees with the
experimental data trend on dispersion-strengthened copper alloy between
700 and 800 ˚C 41. If we take the prediction curve of
-150/+150 MPa as the comparison reference, decreasing the tensile stress
by 50 MPa results in doubling the incubation time, Fig. 10. On the other
hand, the incubation time is shortened by 25%, when the compressive
stress is decreased by 50 MPa.