Fig. 1 FCG in PVC pipe grade
material tested at 1Hz at 20oC. a) rates as a function
of ΔK and b) Kmax. c) ΔK-R plots for selected crack
growth rates and d) ΔK-Kmax plots showing an L-shaped
type of behavior with limiting values of ΔK* and Kmax*.
e). The crack growth trajectory map in terms of ΔK* and
Kmax*.
Fig.2a. The data spread is more extensive in terms of
Kmax than in terms of ΔK. The ΔK-R plots at low crack
growth rates, Fig. 2c, seem to indicate two mechanisms governing the
behavior, one at low R and the other at high R. The corresponding
ΔK-Kmax plots, Fig. 2d, indicate the possible two
L-shaped curves corresponding to the two mechanisms involved. Fig. 2e
shows the crack growth trajectories at both test frequencies. The two
mechanisms operating at a higher frequency are shown, one following the
pure fatigue behavior with ΔK=Kmax, and the other
deviating from