Crack propagation analysis of mechanically damaged compressor blades subjected to high cycle fatigue

This paper presents results of experimental crack propagation analysis of damaged compressor blades of the helicopter engine, subjected to high cycle fatigue. The blades used in investigations were preliminary defected to simulate the foreign object damage. The blades during experiment were entered into transverse vibration. The crack propagation process was conducted in resonance condition. During fatigue investigations the crack length and amplitude of the blade tip displacement were monitored. The fatigue beach marks were not well visible on the fracture. For better determine of crack front shape in the early stage of fatigue fracture, a few blades were vibrated only to the first crack detection. Next the blades were statically tensioned and ruptured with use the testing machine. During performing of an experiment, different schemes of fatigue fracture of the blades were observed. The main result of presented investigation is the crack growth plot obtained for the blade including defects similar to foreign object damage. The attention of this work is also devoted to methodical side of experimental crack propagation analysis of the blade subjected to high cycle fatigue.