Influence mechanism of multi-bolt-flange-spigot structure on the vibration response of dual-rotor system: Numerical and experimental investigations

A resonance-like peak emerges at supercritical speed in dual-rotor system, which will bring a harm to aero-engine. Currently, the mechanism of this abnormal vibration at non-resonant condition remains unclear. In this study, a novel dynamic model of dual-rotor system with a multi-bolt-flange-spigot (BFS) structure is established, incorporating the microscopic contact stiffness and local slippage at interfaces. Based on microscopic contact model and thick-walled cylinder theory, a trans-scale mechanical model of BFS structure is deduced. The microscopic topography and contact pressure of the interfaces at flange and spigot are fully considered. In this way, the lateral and bending stiffness of BFS structure are improved, and the skewness angle of inertial principal is derived to update load excitation vectors. Subsequently, the overall motion equations are obtained and numerically solved. Vibration responses at different speeds are analyzed, including the effects of bolt preloads, interference values of spigot, and surface roughness. Results show that the irreversible local slippage at spigot interface induces the skewness of inertial principal axis, which mainly contributes to the resonance-like peak at supercritical speed. Finally, a dual-rotor test rig is designed to validate the numerical results.