A nonlinear transmissibility function-based diagnosis approach for multi-disks rub-impact faults in rotor systems with nonlinear supports

For diagnosing rub-impact faults in rotor systems, numerous advanced methods leveraging nonlinear vibration features such as Frequency Response Function (FRF), Output Frequency Response (OFR), and Transmissibility Function (TF) have been developed and implemented. Addressing limitations in existing methods, such as the need for reference data from healthy rotors, neglect of nonlinear supports, and focus on single-disk rub-impact faults, this paper introduces a novel systematic approach using nonlinear TF-based indexes. Initially, a comprehensive nonlinear rotor dynamic model is established, incorporating unbalance forces, rub-impact forces, and nonlinear support forces. The nonlinear TF is then defined through nonlinear output spectra. By exciting the rotor system four times with varying unbalance force magnitudes and focusing on a single-disk rotor sub-model, two fault features based on nonlinear TFs and rub-impact fault forces are identified. This innovative approach, featuring sensitive fault indexes and detailed operational procedures, is validated through extensive numerical studies and experimental comparisons on a lab rotor system with multi-disk rub-impact faults and nonlinear supports. The study presents a groundbreaking and effective method for detecting and localizing multi-disk rub-impact faults in rotor systems, even with nonlinear supports.