Abstract
Research on fatigue behavior in the ultra high cycle regime has been recently focused since the fatigue mechanism and S-N behavior different from those observed less than (10)^7 cycles have been observed. It is also of importance from the viewpoint of the long-term service use of structures and machines. Limited research works have been available on fretting fatigue in the ultra high cycle regime, while lots of studies have been done on plain fatigue even in this regime. In the present study, a new machine for ultra high cycle fatigue test has been developed with an electro-magnetic vibrator. It was confirmed that fretting fatigue strength, lives, frictional force and relative slip amplitude were not significantly influenced by the cyclic loading rate up to 300 Hz, which was the present test condition for ultra high cycle fretting fatigue. The fretting fatigue strengths defined at (10)^7 cycles were effective up to (10)^8 and (10)^9 cycles for titanium alloy and aluminum alloy. The fretting fatigue crack initiated at the end region of fretting contact area even in the ultra high cycle regime, which indicated that the fatigue mechanism would not change even in the ultra high cycle regime. This might result from the singular stress field near the contact edge in fretting fatigue.
