Research On Evaluate Technology About Resistance To Foreign Object Damage Of Engine Blade

In the taking-off, landing and near-ground operation state, aircraft engine inhales a variety ofhigh-speed hard foreign objects with the high-speed flow, such as mental, small stone, gravel, etc, whichwill produce the impact damage to fan/compressor blade. The impact damage caused by hard foreignobjects is called foreign object damage, commonly referred to as FOD. It is found that resistance to highcycle fatigue (HCF) is markedly reduced，primarily due to earlier fatigue crack initiation and subsequentearly growth caused by four prominent factors: the stress concentration, residual stress, smallmicrocracks and microstructural damage. This may lead to blade fatigue fracture failure in inspectionperiods, thus becoming a serious threat to flight. Therefore, it is of great significance to investigate theinfluence of FOD on HCF and evaluate the HCF of damaged blade to avoid accidents which caused byFOD.This thesis is focused on the resistance to FOD of fan and compressor baldes. Three aspects havebeen accomplished as follows:(1) Through analyzing the damage characteristics of FOD, the type of machined notch isdetermined. Sizes of two kinds of machined notch were confirmed by finite element calculation. Thefatigue strength of two kinds of machined notch was determined by step loading test method.(2) FOD of14plane speciments was simulated by gas gun test system. It is found that the macrodamage characteristics of damaged speciments involve material extrusion, pile up, loss of materials etc.These characteristics can easily induce the fatigue crack initiation and subsequent early growth. Throughscanning electron microscope (SEM) we can find that the micro damage characteristics of damagedspeciments involve micro cracks, plastic deformation, micro notches and lamellar structure etc.(3) The fatigue strength of14damaged speciments was determined by step loading test method.The results indicate that the fatigue strength of damaged speciments appears clearly downward. Themaximum serviceable limit of blades was obtained through analysis of the relationship between foreignobject damage and machined notch.