For the dent-type foreign object damage (FOD) suffered by the concave side/convex side of fan/compressor blades

experimental study on FOD simulation

analysis of damage characteristics and stress concentration were carried out under different impact angles

while high cycle fatigue tests and fatigue strength prediction of as-impacted and residual stress relief annealed specimens were conducted. Conclusions were drawn as follows: damage depths and stress concentration factors increased with the increase of the impact angle. The range of the damage depth was 0.1-0.5mm

and the range of the stress concentration factors was 1.3-1.7. Under the condition of different impact angles

the fatigue strength of the dent-type damage declined relative to smooth specimens within the range of 50%-70%

and didnt show a monotonic decreasing relationship with stress concentration factors. The worst angle was 60°. The high cycles fatigue(HCF) behavior of residual stress relief annealed specimens was improved

which indicated that effect of residual stress could not be ignored. The HCF behavior of residual stress relief annealed specimens did not decrease with the increase of stress concentration factors

which validated the effect of microstructure damage. It showed that the damage depth as the single parameter to build allowable limits and repair limits had some limitations. Prediction accuracy of fatigue strength for dent-type damaged specimens was within ±20%.