Nonlinear dynamic characteristics induced by inter-shaft rub-impact in a counter-rotational dual-rotor system of aeroengine

The influence and mechanism of inter-shaft rub-impact have not been given a wide attention in exciting literature. This paper aims to insight into the coupled bending-torsional analysis of a counter-rotational dual-rotor system nonlinear vibration characteristics under inter-shaft rubbing fault. Firstly, a dual-rotor finite element model is established, which is based on Timoshenko beam element considering torsional deformations. In particular, the impact force is described by the nonlinear cylindrical collision model. Secondly, the modal characteristics are clarified in detail by the Campbell diagram and modal shapes diagram. Finally, the Newmark-β method is applied to solve the dual-rotor system governing equations with inter-shaft rub-impact numerically. Bifurcation diagram, three-dimensional spectrum, whirl orbit, spectrum plot, and Poincare map are used to preliminarily demonstrate the rotor system dynamic behaviors with inter-shaft rub-impact and the influences of friction coefficient and elastic modulus of the coating. Results reveal the vibration coupling effect and complicated vibration characteristics caused by inter-shaft rub-impact.