The assessment of fatigue life of notched components at uniaxial pulsating loading using the fracture mechanics approach

The growth of a microstructurally short and physically small cracks in the fatigue process zone of size d∗ and the formation of initial macrocrack of length ai = d∗ in compact tension notched specimens are investigated. As a result, the base notch fatigue curve for the assessment of the period of macrocrack initiation in notched specimens of various shape is considered. The prediction results of the fatigue life Nf of notched specimens (a strip with a central hole or a slit and a strip with a U-notch of various tip radius) at the stress ratio R = 0.1 and 0.5 are presented. The new procedures for Nf = Ni + Np assessment, where Ni is the period to macrocrack initiation and Np is the period of macrocrack propagation up to specimen failure, basing on the known unified model of fatigue fracture are elaborated. It is shown that Nf values calculated by two procedures using proposed base notch fatigue curve and standard fatigue macrocrack growth rates diagram are in good agreement with experimental data. The accuracy of received specimens fatigue life is larger than predicted by the preferred methods.