Comparison of nonlinear vibration responses induced by edge crack and surface crack of compressor blades

Abstract

The edge crack and surface crack are two typical cracks of blades. To accurately compare and analyze nonlinear dynamic responses induced by edge cracks and surface cracks of the rotating blade with varying sections and twisted shapes, a modeling method based on solid elements is proposed and validated by measured natural frequencies of an intact blade. The dynamic models of both the blade with edge cracks (BEC) and the blade with surface cracks (BSC) are established considering breathing effects and the proposed dynamic model is also validated by ANSYS software in three aspects, including natural frequencies, vibration characteristics, and contact characteristics between crack surfaces. Finally, the effects of crack depths, crack positions, aerodynamic amplitudes, and rotating speeds on the nonlinear vibration responses of cracked blades are investigated, and the vibration characteristics between BEC and BSC are compared and analyzed. The results show that with the increase of crack depth ratio and the decrease of crack position ratio, the first resonance frequency of the BEC significantly decreases, but that of BSC only fluctuates within a narrow range. In addition, the response amplitude of BEC consistently surpasses that of BSC under the same excitation conditions, which indicates that BEC is more dangerous than BSC.