Dynamic Modeling and Analysis of Propeller Shaft Supported on Rolling Element Bearings

This paper presents modeling and dynamic analysis of marine propulsion shaft supported on three radial and one thrust bearings. The motions of rotor and bearings are under the influence of each other, and therefore, such a system requires structural dynamic studies. Initially, the rotor bearing system is analyzed with finite element model to obtain the modal properties. Internal unbalance force due to mass eccentricity acts on the propeller. Unbalance response of the rotor is obtained numerically from Neumark time integration scheme. Effect of speed and bearing stiffness on the dynamic response is studied. In further case, the radial springs are replaced with three ball bearings, which are modeled by Hertz contact forces expressed in terms of the corresponding nodal displacements. The effects of disk imbalance, thrust bearing stiffness and number of propeller blades on system response are illustrated for different speeds in terms of time and frequency responses. The generalized interactive approach is useful for carrying out parametric studies.