Abstract
The elastic support with adjustable dry friction damper has prospects for vibration reduction of aero-engine rotors under variable working conditions. In this work, we propose a harmonic balance method for predicting the unbalanced response of the elastic supported rotor damped by a frictional damping structure. Distributed 3D contact models are used to describe the nonlinear constitutive relationship of the contact interface. Thus, both the time-varying normal force induced by the coupling of normal/tangential vibration and the curvilinear in-plane relative motion trajectory driven by the rotor whirl can be captured. A multi-step ROM technique is realized and used to reduce the model dimension. The analytical Jacobian matrix is derived to enhance the convergence. The in-house codes work well for predicting the unbalanced response of large-scaled rotor systems containing non-smooth local nonlinearities. Taking a finite element model of a frictionally damped rotor as an example, the accuracy of the proposed method is verified against the Newmark-β integration. The reduced model retains 12 DOFs from the original 172,158 nodes, with an average simulation time of 1.01 seconds per frequency point. Results also indicate that the distribution of contact state on the elastic support friction surface is not uniform, and there are fluctuations in normal force. This proves the necessity of discretizing the friction interface and adopting 3D contact models.
