The Uncracked Situation

Abstract

In plain metallic specimens, such as those shown in Figures 3.2 and 3.4, or in the presence of a mild notch, such as that shown schematically in Figure 4.18, fatigue lives are dominated by fatigue crack initiation, rather than by fatigue crack propagation (Frost et al. 1974). If fatigue crack initiation is defined as the development of a small crack, say 0.5 mm deep, then typically 80 per cent of the fatigue life is occupied by fatigue crack initiation.