THE APPLICATION OF MICROSTRUCTURAL FRACTURE-MECHANICS TO VARIOUS METAL-SURFACE STATES

The fatigue crack initiation period, previously thought to be a necess ary precursor to fatigue crack propagation and eventual failure: is co nsidered here to be a negligible phase in the fatigue failure of polyc rystalline metals. Rather this period is considered to be the propagat ion of a defect of microstructural dimensions by a variety of processe s. The significance of this alternative view is examined in relation t o corrosion fatigue, models of short crack growth, different loading m odes and the enhancement of fatigue resistance by surface shot-peening treatments.