Study on the Self-excited Oscillation of a Propeller-shaft System under Friction Excitation

Friction-induced self-excited vibration in a propeller-shaft system supported by water-lubricated stern-tube bearing was studied. Nonlinear dynamic equations of the propeller-shaft system were formulated by using the Lagrange approach in conjunction with the modal superposition technique to exhibit the excitation mechanism. The model accounted for the lateral-torsional vibrations interaction of the shaft and the bearing-shaft friction represented by the velocity-dependent Stribeck friction model in the low velocity region. Dynamic analyses were carried out using the Newmark- β method with the Newton-Raphson iteration. Analytical and numerical investigations reveal that the instability induced by the negative friction damping gives a rise to the self-excited vibrations and the lateral-torsional vibrations interaction is a reasonable source to enhance the instability.