Fatigue of sintered steel

Abstract

A cloud of microcracks opens plastically around the tip of a long fatigue crack in sintered steel as it propagates. Because of the dilatation caused by the plastic opening of the microcracks, a negative stress intensity factor is induced at the crack tip which reduces the maximum crack tip stress intensity factor. At low values of the stress ratio the minimum crack tip stress intensity factor can be less than zero causing the crack to close and thus reducing the effective crack tip stress intensity factor range and retarding crack growth. Short cracks growing from pores do not have a systematic shield of microcracks and so propagate faster than long cracks at low stress ratios. © 1993.