Assessment of the fatigue failure period of a notched component O.P. Ostash and R.V. Chepil Karpenko Physico-Mechanical Institute, National Academy of Sciences of Ukraine, 5, Naukova Str., 79601, Lviv, Ukraine ABSTRACT: The total period, N f , to failure is considered, which includes the periods of fatigue macrocrack initiation, N i , and propagation, N p , i.e.: N f = 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, * y σ ∆ , 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, ∆K eff " relationship and vice versa. INTRODUCTION For life time estimation of a structural component with an initial long crack, when at cyclic loading crack of length a ≥ a i grows to the critical length a = a c , macrocrack growth rates are studied only, see Figure 1(a). Figure 1: Material endurance characteristics at various stages of fatigue.