Analysis of Fatigue Crack Propagation Law and Fault Characteristics on the Outer Edge of Aeroengine Compressor Disk

The expansion of crack in aeroengine disk to a certain extent can lead to sudden disk rupture, which is a serious fault that may lead to major safety accidents. The impact of disk cracks on shaft vibration is weak, so it is difficult to detect through monitoring shaft vibration. However, they induce regular vibrations of nearby blades. Therefore, the study of the influence of cracks on blade tips” vibration characteristics can provide a theoretical basis for online monitoring and fault diagnosis of disk cracks. In this study, a blisk analysis model was established based on a certain type of aeroengine rotor system. Firstly, the propagation path of cracks is studied, and it can guide us on what kind of cracks to be implanted at the outer edge of disk. Considering the influence of the position and angle of the initial crack on the crack propagation path, it was found that the position of the crack played a major role. And the crack will deflect towards the nearest blade. Secondly, the natural frequencies and blade tip spacing of the disk with different cracks of different depths were studied. The results indicate that the influence of disk cracks on low-order modes is relatively small. But as the depth of the crack increases, the influence on the natural frequency of the dominant mode of the disk gradually increases. Disk with cracks is more prone to exciting blade-disk coupled vibrations. Disk cracks can cause regular changes in blade tip spacing. The blade tip spacing curve near the crack looks like a slightly deformed “W” character. Comparing the above situation with the crack on the blade, it was found that cracks on the blades caused the blade spacing curve to resemble a “Z” character tilted to the left. The differences are distinct, and it is easy to differentiate between the two cracks based on blade tip spacing.