Modeling and Identification Method of Bolt Loosening of Joint Surface under Axial Tension of Multistage Disk-Drum Rotor

Individual bolt at key connection positions is prone to loose when the engine is cycle-operating under complex loads. A joint surface equivalent stiffness model is derived and developed based on the connection characteristics of bolt screwing in the multi-exciting environment of the high pressure rotor. The model is used to analyze the effect of bolt missing at circumferential positions with the equivalent stiffness loss. Vibration experiments under both axial force and lateral impact were carried out to obtain the dynamic response feature of the multistage disk-drum simulated rotor with missing one bolt at different positions. The Spearman correlation coefficient was applied to evaluate the identification effect of different measuring points on the bolt loosening position. The study shows that the eigenfrequencies of experimental results have a consistent trend with the equivalent stiffness variation caused by single bolt missing model. This method also provides a theoretical basis for the detection of bolt deviation position with multi-exciting vibration detection.