Fig. 2. FCG rates in Pipe grade PVC at 10 Hz at 20oC. a) in terms of Kmax and b) in terms of ΔK. c) ΔK-R plots at low crack growth rates showing possible two mechanisms one at low R and the other at high R. d) ΔK-Kmax plots showing two L-shaped curves. e) Comparison of crack growth trajectories for PVC-PIPE GRADE material.
the pure fatigue line. At a lower frequency, the mechanism falls between the two. Osorio has also tested another PVC material, DARVIC110 at several R-ratios. Fig. 3a shows the da/dN curves in terms of ΔK and Fig. 3b in terms of Kmax. The data for this PVC material seem to spread out in terms of both parameters, indicating that the response of this material differs from that of the Pipe grade material. The ΔK-R cures at low crack growth rates are shown in Fig.3c. Again, there seem to be two governing mechanisms operating, one at low R and the other at high R. The