Dynamic modeling of the rotor system with bolted joints considering microscopic contact and nonuniform preloads

The intense vibration of rotor system assembled with bolted joints in high rotational speed brings a potential harm to aero-engine. However, the microscopic contact between disks, coupled with nonuniform preloads, introduces complex nonlinear properties to the rotor system, complicating vibration analysis. This study develops a novel dynamic model of rotor system with bolted joints, considering microscopic contact and nonuniform preloads. Specifically, sub-regions are divided based on pressure distribution under nonuniform preloads, and a multi-scale contact model is deduced based on the fractal theory and semi-analytical method. Subsequently, the lateral and bending stiffness models of bolted-joint disk are refined to incorporate nonuniform preload effects. After solving the motion equations, time/frequency-domain analyses are conducted to reveal the influence of nonuniform preloads and surface roughness on the vibration responses. Through numerical simulation, a comparative analysis is conducted with the traditional dynamic model without microscopic contact and nonuniform preloads. Finally, a bolted-joint rotor test rig is designed to verify the simulation results, and the vibration characteristics under rub-impact faults are analyzed numerically and experimentally.