Nonlinear Friction-Induced Vibration in Water-Lubricated Bearings

Abstract

The problem of friction-induced vibration and squeal in water-lubricated shipboard bearings has received extensive studies during the 1970s. These studies were dominated by experimental tests of section models that emulated the actual bearing dynamics. Linear analytical models were analyzed to predict stability boundaries of the equilibrium position. The role of nonlinearity due to the friction-speed curve as well as the time variation of the friction coefficient was not considered. The purpose of the present study is to develop and analyze a nonlinear two-degree-of-freedom model that emulates the dynamics of water-lubricated bearings. Different dynamic characteristics are predicted from the numerical simulation of the equations of motion. A bifurcation diagram is constructed and exhibits different regimes. These regimes include modulated response signals characterized by two frequency responses, on-off intermittent motion representing the incipient of squeal behavior, and limit cycles accompanied with high frequency components. The squeal is revealed by the presence of a high frequency vibration superimposed on the fundamental system frequency. The occurrence of each regime mainly depends on the value of the slope of the friction-speed curve. Other parameters such as natural frequencies, damping ratios, mass ratio, and the initial conditions have less influence on the incipient of squeal.