Abstract
Cracks are common failures of aeroengine rotated blades. Online monitoring of rotated blades through their vibration to identify cracks early in various working conditions is significant for operational safety. Breathing crack is a practical form of early cracks and results in nonlinear vibration response. Tenon connection and shroud contact are common structures in aeroengine rotated blades, which can also lead blades to vibrate nonlinearly and seriously interfere online identification of early cracks. Thus, it is important to extract vibration features due to breathing crack considering these two structures. Firstly, a blade with tenon and shroud is simplified and a lumped parameter model of the bladed disk is built. Then, dry friction and coupling force on a blade are analyzed and dynamics equations of the lumped parameter model are established. Next, the stiffness of the blade trunk with a breathing crack is analyzed. Finally, the vibration response of blade trunks with the occurrence of breathing crack is analyzed in time and frequency domains by numerical simulation. Effective features due to breathing crack for online identification are extracted. 2x components of spectrums can be the criterion to judge whether breathing crack occurs. Besides, by comparing the changes in vibration amplitudes with 1x component peaks of spectrums, the cracked blade trunk can be distinguished. These findings can provide important theoretical guidance for online identification of early cracks in aeroengine rotated blades.
Highlights
Aeroengine is a power source and a core component of aviation equipment
Location of vibration response is a phenomenon randomly existing between blades in different bladed disks. us, whether breathing crack occurs cannot be judged by comparison between amplitudes especially when the distance is short or the depth is shallow
As common structures of aeroengine blades, tenon connection and shroud contact can lead the blades to vibrate nonlinearly, which can seriously interfere with online identification of early cracks. us, it is necessary to extract features due to breathing crack in consideration of tenon connection and shroud contact and to provide a theoretical guidance for online identification
Summary
Aeroengine is a power source and a core component of aviation equipment. As one of the most fatigue and essential parts in aeroengine, rotated blades are important components for energy conversion. ey suffer various loads including centrifugal force, airflow impact, and alternating forces transferred from other parts of the engine. Wu et al [23] characterized dry friction between shrouds with a nonlinear model to study the effects on blades vibration characteristics under various normal loads and external force. It can be concluded that tenon connection and shroud contact can both cause nonlinear vibration response on blades, which can seriously interfere online identification of early cracks. When these two structures exist, online identification of cracks based on vibration response of blades can be a big challenge. Effects of breathing crack on vibration responses of blades are investigated by numerical simulation considering tenon connection and shroud contact.
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