Nonlinear dynamics of rotor-support-casing system with support looseness fault

This paper proposes a time-domain numerical method combining explicit and implicit schemes for efficiently solving high-dimensional systems with localized nonlinearities. This method is applied to investigate the nonlinear dynamic characteristics of a rotor-support-casing system with support looseness fault. A dynamic model incorporating multi-interface nonlinear supports is developed, which includes nonlinear bearings, a squeeze film damper (SFD), and the contact interaction between the bearing and its housing. The model is validated through modal testing and vibration response experiments. To obtain the vibration response of the system, a hybrid numerical integration method is proposed, with its core focused on optimizing the iterative solution process. This method separates the linear and nonlinear parts of the system, predicts the coupling node response using an explicit scheme, and solves the linear and nonlinear parts using an implicit numerical method and a quasi-Newton iterative algorithm, respectively. Compared with conventional approaches, this method significantly improves computational efficiency. Subsequently, the effects of rotor speed, fit clearance, and oil film clearance in SFD on the dynamic response of the rotor-support-casing system under support looseness faults are investigated. The results show that support looseness alters system stability, leading to periodic, multi-periodic, and quasi-periodic responses. Both fit clearance and oil film clearance significantly influence the system's nonlinear behavior. Under serious fault conditions, fractional-order rotational speed harmonics appear in the casing vibration response. The proposed modeling approach and hybrid numerical method demonstrate strong potential for engineering applications in aero-engine vibration prediction.