Page 386 - Biaxial Multiaxial Fatigue and Fracture

370 M. FONTE ETAL.

In Figures 6 (a) and (b), the threshold values of and K,, are plotted for different R-
ratios in ambient air and vacuum, respectively. They show that at low (and negative) R-ratios
IC- is the crack growth governing process, whereas it is A&, at higher R-values. This is the
case for both environments, ambient air as well as vacuum.

Fig. 6. Thresholds dKth - KmaX values of UA and OA alloy for
different stress ratios R in ambient air (a) and in vacuum (b).