Characteristics of stick-slip oscillations in dry friction backward whirl of piecewise smooth rotor/stator rubbing systems

Self-excited dry friction backward whirl, or shortly denoted as DFBW, are the most destructive rotor/stator rubbing response. From the point of view of sliding bifurcations, this paper first unveils the characteristics of stick-slip oscillations exhibited in the response of self-excited dry friction backward whirl. By studying a four-dimensional piecewise smooth rotor/stator rubbing system, which has a switching manifold defined by the zero relative velocity on the rubbing point, three types of sliding regions on the curved hypersurface of the switching manifold are identified according to the characters of the two discontinuous vector fields near it. The influence of the system parameters on the stick-slip transitions in DFBW is also explored, which shows the interplay of the different parameters and reveals the phenomenon observed experimentally. On basis of the relation between the existence boundaries of DFBW and the characters of sliding motions on it, a new way, from the theory of non-smooth dynamics, to analytically derive the existence condition of the self-excited dry friction backward whirl (DFBW) is presented and coincident with the existing formula in the literature. The work provides a deeper insight into the more detailed response characteristics in the self-excited dry friction backward whirl of rotor/stator rubbing systems. (C) 2019 Elsevier Ltd. All rights reserved.