Fatigue Crank Initiation and Propagation

The fatigue process may be considered as the progressive development of a crack from the submicroscopic phases of cyclic slip and crack initiation, through the macroscopic crack propagation period, to final fracture. Experimental data indicate that the significance of each of these phases, in relation to the total fatigue life, is primarily dependent upon the cyclic stress amplitude, and that a more fundamental understanding can be achieved by separate studies of the crack initiation and propagation period.