Small cracks—nucleation, growth and implication to fatigue life

The nucleation and early propagation of fatigue cracks are smoothly consequential processes, which can occupy a major part of the fatigue life of structural materials. Nevertheless, their quantitative description is at present not yet sufficient to perform reliable life calculations. The paper summarizes the present state of the art in the recent advancement of nucleation and early propagation of cracks in metals both as for the mechanisms and as for their quantitative description. The following items are treated: Sites of crack nucleation, prerequisites and mechanisms of the nucleation, end of nucleation stage and transition to propagation stage, plasticity of small cracks and growth of microstructurally and mechanically small cracks.