Dynamic modeling and simulation analysis of inter-shaft bearing fault of a dual-rotor system.

• A Lagrangian energy equation containing kinetic energy, potential energy, Rayleigh dissipation energy and generalized force virtual work is derived from the dynamics universal equation, based on which a fault dynamics model of an 8-degree-of-freedom dual-rotor inter-shaft bearing system is developed. • Validate the model to be accurate in simulating local defects. • Accurately simulated the time-frequency characteristics of the dual-rotor inter-shaft bearing system when failures occur. • Based on the discrete characteristics of Lagrange's equation, the analysis of different structural vibration characteristics in the same system increases the efficiency of work. • It is found that the rotor vibration signal is accompanied by high harmonic vibration signal when there is a fault in the system, and this conclusion provides theoretical support for aero-engine fault vibration analysis. In order to study the vibration characteristics of inter-shaft bearing failures of a dual-rotor system, an eight-degree-of-freedom dynamic model of dual-rotor system containing inter-shaft bearings is established. The Newmark-β method is used to solve the proposed model equations. The dynamic characteristics of the rotor system when the inner ring and outer ring of the inter-shaft bearing has single-point failures or composite failures are analyzed. The comparison results show that the fault frequency distribution pattern in the envelope spectrum of the dynamic simulation results is consistent with that of the test results, which proves the effectiveness of the proposed dynamic model. It is found that when the inter-shaft bearing fails, a combination of rotor rotation frequency, multi-frequency, and fault frequency modulation frequency occurs in the fault characteristic frequency of the dual-rotor system. In addition to the speed-synchronized vibration components caused by the eccentricity, the rotor vibration signal is usually accompanied by a high-order harmonic vibration signal. [ABSTRACT FROM AUTHOR]