An assembly tightness detection method for bolt-jointed rotor with wavelet energy entropy

Abstract

The jointed rotor is a representative rotor structure widely used in gas turbine and aero-engine, in which two or more adjacent parts are pressed together by bolted joints with sufficient preload force. However, the assembly tightness states of bolted joints are prone to be affected by frictional factor and workers' experience when they are assembled by axial elongation control method, leading to preload inconsistency in the whole rotor and having a significant effect on rotor dynamics. At present, the current assembly tightness detection method mainly focuses on whether bolt looseness fault occurs but ignores the effect of assembly tightness degree on rotor vibration. Therefore, an assembly tightness detection method is proposed based on wavelet energy entropy to detect different assembly tightness degree of bolted rotor with six different assembly tightness states. By means of vibration test on jointed rotor, various vibration response signals are acquired with bolted rotor from tightness to looseness. The vibration response signals of rotor are decomposed and reconstructed by db wavelet and finally a quantitative index based on wavelet energy entropy is defined to realize the identification of tightness degree of bolted joints. The result shows that the quantitative index tends to monotonously increase with bolt joints assembled from tightness to looseness, which is also proved to be stable, applicable and efficient in comparative experiment.