Nonlinear vibration characteristics of marine propulsion shafting under bending-longitudinal coupling effect

Abstract

[Objectives]The propulsion shafting system of large ships usually has the characteristics of long shafting, large span, and small slenderness ratio. Therefore,there is often elastic coupling effect between the bending deformation and longitudinal deformation,which is easy to cause abnormal vibration of the shafting,and affect the safe and stable operation of the shafting system. In order to study the nonlinear vibration characteristics of the shaft under bending-longitudinal coupling effect,[Methods]the nonlinear vibration equations of the propulsion shafting under bending-longitudinal coupling effect were derived by using the principle of variation,and then solved by numerical methods such as Finite Element Method(FEM)and shooting method and by approximate analysis method such as multi-scale method. Then the influence of bending-longitudinal coupling effect on the nonlinear vibration characteristics of shafting was analyzed and compared.[Results]The results show that the bending-longitudinal coupling effect causes complex vibration phenomena such as multi-frequency response,jumping phenomenon and energy transfer in the shafting response,and increases the natural frequencies in the bending and longitudinal direction of the shafting.[Conclusions]The study in this paper can provide reference for engineering design of large ship propulsion shafting.

Keywords

• propulsion shafting
• bending and longitudinal coupling
• FEM
• shooting method
• multi-scale method