Influence of different parameters on nonlinear friction-induced vibration characteristics of water lubricated stern bearings

To investigate the mechanism of friction-induced vibration and noise of ship water lubricated stern bearings, a two-degree-of-freedom (2-DOF) nonlinear self-excited vibration model is established. The novelty of this work lies in the detailed analysis of influence of different parameters on the stability and nonlinear vibration characteristics of the system, which provides a theoretical basis for the various friction vibration and noise phenomenon and has a very important directive meaning for low noise design of water lubricated stern bearings. The results reveal that the change of any parameter, such as rotating speed of shaft, contact pressure, friction coefficient, system damping and stiffness, has an important influence on the stability and nonlinear response of the system. The vibration amplitudes of the system increase as (a) rotating speed of shaft, contact pressure, and the ratio of static friction coefficient to dynamic friction coefficient increase and (b) the transmission damping between motor and shaft decreases. The frequency spectrum of the system is modulated by the first mode natural frequency, which is continuous multi-harmonics of the first mode natural frequency. The response of the system presents a quasi-periodic motion. •A mechanism model considering the relative velocity-friction force nonlinearity is established.•Influence of parameter variations on the instability criterion of the system is investigated.•Friction-induced self-excited vibration occurs in a certain speed range.•Frequency spectrum of the system is modulated by the first mode natural frequency.•Friction-induced self-excited vibration of the system presents a quasi-periodic motion.