Application of dynamic model and output spectrum to diagnose loose connections in bolted rotor-support systems

Bolted rotor-support systems in rotating machines frequently encounter loose connections caused by dynamic loads, which may inevitably induce extremely large vibration magnitudes and coupling faults. However, there are a few vibration feature-based methods to detect and localise loose connections up to now. Therefore, by considering real situations of bolted rotor-support systems and referring to existing methods for non-rotating bolted structures, this study develops a reliable method, which is based on rotor dynamic model and nonlinear output spectrum. Firstly, the bolted rotor-support system’s nonlinear dynamic model is established by considering influences of loose connection forces. Then, related loose connection forces are computed applying the rotor dynamic model and limited nonlinear output spectra to define sensitive diagnostic indexes. After that, lab testing on a bolted rotor-support system with loose connections at single/multiple disks are performed, and comparative results fully indicate the applicability of the newly developed method. Compared with exiting methods, the proposed method in this study, which considers real situations of bolted rotor-support systems and requires fewer sensors and less vibration data, provides an effective tool to determine both existence and position of potential loose connections in bolted rotor-support systems.