Modeling and dynamic analysis for rotors with curvic-coupling looseness

Abstract

The joint structures, such as flanges with bolts and curvic-couplings, are commonly applied in aero-engine rotors. Those joints tend to loosen when subjected to heavy load, and the local deformation of the joints can induce nonlinearities to the rotor and further affect its dynamic characteristics. However, much research focuses on the bolted joint loosening, while the studies of curvic-coupling loosening in rotor systems are seldom reported. In this paper, the modeling and dynamics analysis for rotors with curvic-coupling loosening are performed. First, an analytical model is proposed to describe the nonlinear stiffness caused by looseness at the joint interface. Then, a rotor with curvic-coupling looseness is modeled and the related dynamic equations are derived. Finally, the modal characteristics of the rotor with curvic-coupling looseness are analyzed based on the complex nonlinear modes method, and the rotor’s steady-state response is obtained using numerical methods. The results show that the softening behavior introduced by joint looseness can lead to eigen frequency reduction in modal analysis, amplitude jump in response, and bifurcation around the critical speed. The above dynamic characteristics can provide reference for fault diagnosis in the rotor system with curvic-coupling loosening.