Effect of foreign object damage on high-cycle fatigue strength of titanium alloy for aero-engine blade

To address the fatigue behavior of damaged aero-engine blade, in the current paper, the research on high cycle fatigue (HCF) strength of TC11 titanium alloy after subjected to foreign object damage (FOD) were presented. First of all, FOD simulation tests were carried out on simulated flat blade samples using gas cannon test system. The macro and micro impact damage of samples were examined in detail. The FOD test results shows that the microscopic characteristics of damage area include smooth area, micro cracks, micro notches, shear bands and loss of material (LOM). Then, HCF tests were carried out on the damaged flat blade samples using HCF fatigue testing machine through stepping method. The undamaged standard test specimens were also tested for HCF limit as baseline. The fatigue results show that the damage depth L2 related to impact velocity has a great influence on fatigue limit. The greater the impact velocity, the lower the fatigue limit. Microscopic observation on fatigue fracture was conducted by metallographic microscope and found that FOD would change the microstructure of material in damage area, made the phase to be slender and in a certain arrangement direction.