No abstract

The vibration stress caused by resonance is the main cause of failure in aircraft engine blades. The study investigated the vibration stress of a single-stage fan blade influenced by the interaction of aerodynamic and structural behavior at multiple critical speeds. A numerically based analysis through the interfacing of computational fluid dynamics and finite element modeling analysis, referred to as fluid-structure interaction was performed. A three-dimensional finite element model of the blade which was verified by modal test was established to carry out response analysis when blade resonates. A single flow channel model of the blade was constructed to simulate the aerodynamic pressure loads that result in vibration of the fan blades. The Campbell diagram was introduced to determine the critical conditions of the blade. The results show that resonance phenomenon appears for several times between 2000 and 3600 r/min, and further analyses of the blade mode shape as well as dynamic stress at these speeds indicate that vibration stress at critical speed is obviously higher than those at the adjacent speeds. But there is no positive correlation between the peak stress and critical speed, while it is determined by the comprehensive action of critical speed, vibration mode and synchronous excitation. The peak stress distribution is closely linked to the mode shape of the blade, and it always appears at the leading edge and changes along the blade height. It also illustrates that the leading edge of the blade is most prone to vibration fatigue.

Abstract. The linear damage model (LDM) is widely applied in engineering calculation, but it does not consider the relationship between damage variable and load parameters. Therefore, the life prediction based on LDM is not satisfied for the aero-engine blades. Besides, it easily brings about error in predicting fatigue life by common nonlinear damage model which neglect the influence of torsional stress. Hence, a modified nonlinear continuum damage model (CDM) is put forward based on Chaboche nonlinear damage model in this research. And to determine the damage and fatigue life of TC4 material used in aero-engine blades, axial tension and compression fatigue test is conducted. Compared with LDM results, the fatigue life prediction results of the modified CDM in this work show a good agreement with the tests data. So the correctness of the modified model is verified. Finally, the fatigue life of a certain aero-engine high pressure compressor blade is predicted by the modified nonlinear continuum damage model.