Abstract： [Objectives] The Stern bearing is an important part of marine propulsion shafting. Due to the cantilever action of propeller, the transverse deformation of shaft on this section is obvious. Due to the relatively large length and diameter of the stern bearing, it is difficult to reflect the actual operating conditions of the bearing when simplified to the traditional equivalent model of single-point support. Therefore, the influence of the equivalent form of the stern bearing on the transverse vibration characteristics of the shafting is investigate. Based on this, the influence of the change of support stiffness equivalent to the liquid film pressure on the lateral vibration of the shafting and the influence of the propeller excitation on the vibration response of the shafting are further analyzed.
[Methods] The improved Fourier series was introduced to describe the lateral vibration displacement of propulsion shafting. Then, the calculation model of lateral vibration performance of propulsion shafting under various equivalent forms,such as single point support, multi-point support or continuous distribution support, was constructed based on the energy principle.
[Results] Compared with the results of related references and FEM, the correctness of the calculation model is verified. At the same time, combined with the calculation results of the equivalent stiffness of the bearing affected by the inclination of the shafting, the influence of factors such as the equivalent form of the stern bearing and the pressure distribution on the lateral vibration was studied. In addition, the influence of the propeller excitation on the vibration response of the shafting is also discussed.
[Conclusions] The form of point support converges to the continuous distribution with the increase of the number of support points; The first natural frequency of shafting is obviously affected by the number of support points; After considering the influence of the inclination of the stern bearing support, the equivalent method of three-point support can be considered at low frequencies to approximate continuous distributed support; When discussing the influence of the propeller excitation on the vibration response of the shafting, it is necessary to consider the influence of the rotation speed on the excitation and the influence of the rotation speed on the stiffness of the bearing.