Ultra-high Cycles Fatigue Properties of Titanium Alloy with Different Slight Damages on Surface

Ultra-high cycles fatigue tests of titanium alloy with and without different slight damages on surface was performed using ultra-high cycle bending fatigue system under the condition of 20 kHz excitation frequency, and the fracture images were observed by optical microscopy. The results show that the fatigue life of TC6 alloy without damage and with slight damages increased continuously with the decrease of stress levels. The sample still appeared fatigue failure when the cycles were more than 107, so there was no fatigue limit. Slight point stress damage could decrease the sample′s fatigue life, but the line scratches made little changes under low stress condition. Fatigue cracks initiated on sample surface, and the fatigue source initiation position was not affected by the stress damge and line scratches on samples surface.