Investigations on fretting fatigue in aircraft engine compressor blade

An investigation of several cracked blade tangs in the military aircraft engine compressor was conducted to identify the root cause of the failure. These cracks were found during the scheduled maintenance with fluorescent penetration inspection. The engine compressor blade made of Ti–6Al–4V is attached to compressor rotor by means of inserting retaining pin through rotor and blade tang. By analyzing the fracture surface of the failed blade tang, it is found that the crack in the blade tang was initiated by fretting fatigue and propagated under low cycle fatigue. Stress analysis of the blade using a non-linear finite element method is coincident with the results of fractography. The clearance between retaining pin and tang hole caused small amplitude of sliding motion leading to fretting wear during engine operation. Consequently, the damaged area due to fretting wear acts as a stress raiser inside tang hole and contributes to accelerate fretting fatigue.