Effect of low cycle fatigue pre-damage on high cycle fatigue strength of TA11 alloy

The effect of pre-damage of low cycle fatigue (LCF) on high cycle fatigue (HCF) strength of TA11 alloy was experimentally investigated. Three factors were considered, including cyclic max stress, stress ratio and the life ratio in LCF experiment. The effect of LCF pre-damage on high cycle fatigue strength of standard specimen was obtained using rotation bending fatigue experiment according to a step-by-step procedure. Result shows that the previous LCF cycles with the max stress of 900 MPa generate a larger cyclic plastic strain. Therefore, even applying few LCF pre-damage can still reduce the HCF strength. Different stress ratios of LCF pre-damage will reduce the HCF strength. For different max stress in LCF pre-damage, when the LCF pre-damage max stress is far lower than the yield strength, it has less effect on the HCF strength. However, the effect on TA11 alloy must be considered when the LCF pre-damage max stress is close to or greater than the yield strength.