Dynamic Responses of Ship Propulsion Shaft Under Hull Excitations at Bearings

Abstract

With the development of ship enlargement and economization, dynamic interaction of a propulsion shaft and ship hull is more and more evident, especially when it is travelling in rough seas. Bearings, as the connection between propulsion shaft and ship hull, transmit the forces from ship hull to propulsion shaft. Thus, the model of shaft with the excitations at bearings can be seen as a simplified propulsion shaft-ship hull system to analyze the effect of hull deformation. Based on the theory of vibration of shaft, in this paper, equations of shaft motion and boundary conditions are presented. Moreover, in the continuity conditions equations at each support, harmonic forces from hull is included. Dynamic responses of propulsion shaft under hull deformation excitations are gained by analytical method. The effects of supports stiffness, locations of hull deformation excitations, the amplitude of excitations and shaft size are discussed by comparing the response displacements of observed points. At the same time, numerical calculation is set to validate the accuracy and feasibility of analytical method. The conclusions could apply the accordance for design and optimization of the ship propulsion shaft, when the hull deformation excitations at bearings are considered.