Fig. 11 Prediction of the present simulation against the corresponding
experimental fatigue lifetime 3 for six repeated
two-step loading block tests, T1-T6, with the parameters listed in Table
1(b); Each virtual test was carried out seven times with different
specimen configurations.
The stresses listed in Table 1 are higher than the material fatigue
limit. The cracks analyzed in the present work are short and subjected
to relatively high stresses. Most of those cracks grow in surface grains
experiencing plastic deformation in the course of the tensile and
compressive parts of the loading cycles. Thus, the well-known effect of
the high load on the retardation behavior of the tips advancing in those
grains as a result of changing the load to the low level is ignored58, 59 in the present work. The results presented in
Fig. 11 indicate that the lower load of a loading block is applied for a
number of cycles less than that required for the full development of
such an effect.