Crack Initiation and Propagation in a Forged Nickel-Base Alloy Under High Mechanical and Thermal Loading

The technically relevant mechanical properties of a commercially produced large diameter forging of Nimonic 901 have been determined. Results from low and high cycle fatigue tests on both round and fracture mechanics type specimens could be plotted on a common curve by using the Smith Watson Topper stress-strain parameter. Mean stress effects were also accounted for. A comparison of the threshold value for fatigue crack propagation with the high cycle fatigue limit of plain specimens shows that crack nuclei of size comparable with the grain size must be initially formed.