CHAOTIC RESPONSES OF UNBALANCED ROTOR-BEARING STATOR SYSTEMS WITH LOOSENESS OR RUBS

The first part of this paper presents results of numerical simulation of the dynamic behavior of a one-lateral-mode unbalanced and radially side-loaded rotor with either a loose pedestal (looseness in a station ary joint), or with occasional rotor-to-stator rubbing. The nonlineari ties of these systems (variable stiffness, impacting, and friction) ar e associated with the rotor intermittent contacts with the stationary element. The results, based on a newly developed local impact model [P . Goldman and A. Muszynska, Analytical and experimental simulation of loose pedestal dynamic effects on a rotating machine vibrational respo nse, Rotating Machinery Dynamics, DE-Vol. 35, ASME, Miami, Florida, pp . 11-17 (1991); P. Goldman and A. Muszynska, Analytical model of the i mpact between rotating and nonrotating elements and its application in rotor-to-stator rubbing, BRDRC Report 1, (1992); P. Goldman and A. Mu szynska, Chaotic behavior of rotor-to-stator systems with rubs, ASME T urbo EXPO Conference, 93-GT-34, Cincinnati, Ohio, Transactions of the ASME (to appear); P. Goldman and A. Muszynska, Dynamic effects in mech anical structures with gap and impacting: Order and chaos, Trans. of A SME, J. Vibration and Acoustics (1994)] exhibit regular periodic vibra tions of synchronous (1x) and subsynchronous (1/2x, 1/3x, ...) orders, as well as chaotic vibration patterns of the rotor, all accompanied b y higher harmonics. The second part of the paper presents experimental vibration characteristics of rotors with looseness or rubs, Obtained from rotor rigs. The results display similar patterns as those obtaine d analytically.