Crack closure of Ni-based superalloy 718 at high negative stress ratios

Fatigue crack growth damage mechanisms for nickel-based superalloys at high, negative stress ratios challenge classical tip shielding and closure concepts. rate single-edge notch Ni-based superalloy 718 specimens 100 °C were evaluated several (0.5, 0.1, ?1, ?2). Multiple methods used to calculate the effective driving force rates in region II (i.e., Paris or power law regime). The relationships between forces, experimentally-measured levels, fractographic evidence of are discussed.