Simulation and experimental research on vibration response of microcracked compressor blades under variable working conditions

Compressor blades play a crucial role in aero-engines, experiencing complex alternating loads under variable working conditions (VWC). Resonance is inevitable under these conditions, leading to the development of blade crack faults. To understand and analyze this phenomenon, a finite element (FE) model of a microcracked blade was created using ANSYS. The model's accuracy was verified through a hammering experiment. Additionally, a resonance fatigue test was used to accurately obtain dynamic characteristics for prefabricated breathing cracks. The experiment demonstrated that cracked blades exhibit smaller responses in the time domain compared to intact blades, while showing super-harmonics in the frequency domain, thus validating the effectiveness of numerical simulation. The effects of VWC on the nonlinear vibration characteristics (VC) of the blade with a breathing microcrack were investigated. These VWC included variable speed, the amplitude of the exciting force (F0), depth of the microcrack (D), and length of the microcrack (L). The results revealed significant increases in the frequency domain response amplitude of the blade at super-harmonics with the increase of F0, D, and L at variable speeds. Furthermore, the breathing behavior of microcracked blades diminished with increasing rotating speed (N), D, and L. The observed decrease in frequency and the emergence of super-harmonic serves as indicators of the presence and severity of blade cracks. These findings are of great significance for the development of online monitoring technology for blade faults.