Crack propagation analysis of compressor blade subjected to resonant vibrations

In this work the crack propagation analysis of the compressor blade of aero engine was performed. During investigations the blade with mechanical defect (notch) was considered. In experimental analysis the blade was subjected to resonant vibration. During transverse vibrations, a high stress occurs in the blade. Pulsation of stress causes the fatigue of material. In results of proposed investigations both the number of load cycles to initiation and also the crack growth dynamics was obtained for the blade working in resonance condition. In second part of work the maximum principal stress distributions in the vibrated blade were determined using nite element method. and are particularly susceptible to HCF. During work of engine, blades are excited by an unbalanced rotor. The worst case is when the frequency of excitation overlaps with the resonant frequency of the blade. During resonance, large amplitude of stress causes that the blade can be damaged in relatively short time. The fatigue process is often acceler- ated by mechanical defects (notches) created during collision of rotated blade with hard objects suctioned from a ground. If aproblem arises in the compressor section it will signicantly aect the whole engine function and safety of the aircraft. The broken blade could cause the puncture of the engine casing. Failures of any high speed rotating components (jet engine rotors, centrifuges, high speed fans, etc.) can be very dangerous to passengers, personnel and surrounding equipment and must always be avoided. The failure analysis of the compressor blade has received the attention of several investigations. The problem of fatigue fracture of the aero engine blades was described in works (1-10). The objective of presented investigation is to determine both the number of load cycles to crack initiation and also the crack growth dynamic for the compressor blade of aero engine (including articially created mechanical defects), subjected to resonant vibrations. Created defects (notches) simulate the foreign object dam- age (FOD) of the blade. An additional aim of work is numerical determination of maximum principal stress values in the blade with the notch subjected to resonant vibration.