Mixed-mode fatigue crack growth thresholds of a Ni-based single crystal alloy

This investigation examined the effects of stress state and crystal orientation on the near threshold fatigue crack growth (FCG) response of PWA 1484 single crystal material. Mixed mode FCG on (0 1 0) and (1 1 1) planes was characterized in air at 593degreesC, using an asymmetric four-point bend test technique. Stress intensity factor solutions of the crack specimen were obtained using anisotropic fracture mechanics. The influence of mode mixity on the FCG threshold was determined as a function of stress state, ranging from pure Mode I to pure Mode H. This paper summarizes the progress in applying the analytical and experimental results to develop a fracture mechanics approach for treating mixed-mode FCG in single crystal materials.