Stability of a journal bearing system with a divided and piezoelectrically controlled bearing shell

In the paper the problem of stability of a journal bearing system with divided and movable shell actively controlled by piezoelectric elements is considered. The shell consists of three segments - two fixed and the middle one connected with a piezoelectric actuator. The actuator shifts the movable part in the direction normal to the bearing axis. Hence, the whole support loses its co-axiality. A slightest displacement of the middle segment yields in fact a change in the oil gap - the most influential factor deciding about the stability. The paper presents the concept and provides one with the theoretical fundamentals. The equations of motion are derived and examined in terms of the stability of the non-trivial equilibrium, so that the critical rotation speed, at which self-excited vibration appears, could be determined. The plane model based on the simplified Reynolds Equation is employed in the investigations. Results of numerical simulations prove that the method is quite effective and brings considerable growth of the critical speed.