Abstract
Fretting fatigue tests in ultra high cycle region up to 10^9 cycles were performed to investigate whether the fatigue limit which means infinite life really exists in fretting fatigue. S-N curve had knee point around 2×10^7 cycles and it was verified that clear fatigue limit was observed up to10^9 cycles. An electric potential drop technique was developed to detect the crack under contact pad. The real time measurement of crack depth during fretting fatigue showed that initiated crack ceased to grow at about 2×10^7 cycles and the crack became a non-propagating crack at least up to 10^9 cycles. These results indicated that the fatigue limit can exist also in fretting fatigue. The infinite endurance can be achieved by the mechanism to become a non-propagating crack.
