Based on the air-gun impact test device

the foreign object damage (FOD) simulation test of TC4 titanium alloy plate specimens was conducted at different impact angles. The high cycle fatigue (HCF) strength of smooth and impact damage samples was obtained with the step-test method. The relationship among the impact angles

impact positions

macroscopic geometry of impact damage and HCF strength of the damaged samples was studied. Results show that

the effect of impact damages on the HCF strength at different impact angles is not the same. When the impact damage appears at the edge of sample

the maximum decrease of HCF strength occurs in the impaction of 30°; while the impact damages appear at the middle of sample

the maximum decrease of HCF strength occurs in the impaction of 60°. In most cases

impact notches at the samples' edge compared to impact pits at the sample's intermediate surface have a more seriously effect on the HCF strength. However

at the impaction of 60°

the impact pit damage has a more serious effect. The geometry of the impact damage to a certain extent can characterize the changes of the HCF strength severity of damaged sample.