There is no infinite fatigue life in metallic materials

Generally, the shape of the S-N curve beyond 10(7) cycles is unknown except in some statistical approaches, and this is also true for the fatigue limi t. In the case of a statistical approach, the standard deviation applied to the average fatigue limit is certainly not the best way to reduce the risk of rupture in fatigue. Only the exploration of the life range between 10(6 ) and 10(10) cycles will create a safer basis for modelling. Today, some piezoelectric fatigue machines are very reliable, capable of pr oducing 10(10) cycles in less than 1 week. We based our research on acceler ated fatigue tests which were performed at 20 Hz in the gigacyclic fatigue regime in order to study several typical alloys from the aeronautical and s pace industries.