The total period Nf, to failure is considered, which includes the periods of fatigue macrocrack initiation, N_i and propagation, N_p, i.e.: Nf = N_i + N_p. Fatigue fracture of materials has been modelled as a process of initiation of a macrocrack of length a_i =d~* (the magnitude of d~* is a material constant), which is successively repeated (step-by-step) during its growth. As a result the "local stress range, Δσ_y~* , versus macrocrack initiation period, N_i " relationship, which was established for notched specimens, might be applied to the determination of the "macrocrack growth rate, da/dN, versus effective stress intensity factor range, ΔK_(eff)" relationship and vice versa.
展开▼
