Effect of stress concentration factor and residual stresses on the delay of fatigue crack propagation

The aim of this paper was to study the effects of expanded hole and non expanded hole on the delay of fatigue crack propagation. Aluminium alloys 6005A T6 and 6082 T6 with a single edge pre-cracked were used to perform the crack arresting tests under cyclic stress loading. This improvement, attributed to the effect of a compressive residual stresses induced by expanding process in the neighbourhood of the hole, is the result of an increase of the delay of crack propagation. The observation of microstructure at the fatigue failure section reveals that the hole expanding process modifies the mechanical properties at the surface of a material and affects significantly the length of the nucleation stage of the fatigue process.