Effects Of Micro-Damage And Residual Stress Of Foreign Object Damage To Blades On Fatigue Properties

The sand or metal impact plane in taking-off, landing or low altitude flight, causing foreign object damage.Foreign object damage can cause macro-damage in impact location, accompanied with the micro-damage and residual stress, leading the fatigue strength of engine blade decreasing, doing damage to the aircraft flight safety. So the research on the effect of foreign object damage, micro damage and residual stress on fatigue properties has an important significance.The paper studies on FOD, including the following:(1)In this paper, plate specimen is simulated FOD by using gas gun, the macro damage is measured by using 3d numerical microscope and observed by using SEM. There are micro damage characteristics on the surface of damage, such as the smooth region, plastic deformation, micro cracks, micro gap, shear zone, loss of material..(2)The fatigue strength of the smooth specimens and FOD specimens is tested in the paper. FOD causes the decrease on fatigue strength, and makes it be discreted. The damage parameter L4, foreign object size, the impact velocity is the factor affecting on fatigue life. The damage parameter L1 and L3 has little effect on fatigue strength of plate specimen.(3)Foreign object damage will change the microstructure of material in damage area, makes the phase to be slender and have a certain arrangement direction. Stress relief annealing can eliminate the residual stress and improve microstructure of samples, enhance the fatigue strength. The average fatigue strength of machined specimens is better than stress relief annealing samples.