Foreign Object Damage Effect on the Fatigue Strength of Ti–6Al–4V Specimens

The fatigue strength deterioration in Ti–6Al–4V specimens impacted by steel sphere was experimentally investigated. Based on the test data of Peterson’s formula and the fatigue notch factor, the relationships linking the fatigue notch factor, fatigue strength, injury notch size, and stress ratio were derived. The effect of the notch dimension, residual stress, and stress ratio on the fatigue strength is discussed. The main conclusion is that the impact damage-induced reduction of the fatigue strength depends on the ratio between notch depth and notch radius: the greater the ratio, the more pronounced the reduction. Furthermore, the greater the stress ratio, the less id the reduction. These findings have a certain reference value for blade protection design against foreign object damage, the standard-setting, and maintenance guidelines.