| Foreign object damage(FOD)occurs during the usage of aero-engine as a result of fan blades are impacted by small hard debris.FOD usually shows as little damage may result in High cycle fatigue(HCF)failures of fan blades under complex loads condition due to the blades vibrations and resonant airflow dynamics,which seriously affect the safety of aircraft and property.In the stage of FOD tolerance design,changing the geometry of blades is an effect way to increase the blades HCF strength.In this paper,the leading edge specimen designed according to the geometry of real fan blades are made of TC4 titanium alloy.FOD damage characteristics and the effect of leading edge geometry on the HCF strength of the damaged blades were systematically studied under laboratory conditions.The main work and conclusions are as follows:(1)The method of High-speed ballistic impact based on air gun is used to simulated FOD in library.Under the same compact condition,most of the damages are showed as nicks,some are dent-nicks and others are dents.The impact position has a great influence on the features of the damage.View the damages,the influence of leading edge radius on damage size is larger than that of leading edge wedge angle.(2)The failure strain for erosion of Bammann damage model were calibrated by trial and error method,the result is 0.2.Compare the numerical simulation with the physical simulation,the results show that the damage size decreases with the increase of the leading edge radius,while the leading edge wedge angle has no obvious effect on the damage size.The maximum equivalent plastic strain of the specimen appears at the bottom of the notch.(3)Specimens impacted under the FOD laboratory simulation were tested using step-loading method to determine HCF strength.The results show that leading edge radius and wedge angle have no obvious effect on the decrease of HCF strength.Fatigue notch factor predicted by Peterson’s fatigue notch factor formula is lower than true value. |
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