Fatigue Crack Initiation in Nonferrous Materials: A Model Assessment

Elastic stress concentration (Ktdapproach), fracture mechanics, and local strain approaches were evaluated for predicting fatigue crack initiation for a 2024-T3 aluminum alloy, commeretally pure copper. 70–30 brass, and Cu-Be alloy 25 Blunt (keyhole) and sharp (V-notched) compact tension specimens were subjected to cyclic loading in ambient laboratory air to produce crack initiation in the range 104to 106cycles.The results show that the best initiation model. Ktdapproach is based on computed estimates of strain at some distance ahead the notch root. This distance was shown to be inversely related to the material's strength. This model properly described the influence of both material and geometry over the full range of initiation cycles. Ni. Local strain and fracture mechanics models were less sensitive and exhibited greater variability.