Research On Vibration Characteristics Of Coupled System Of Shaft And Conical-Cylindrical Combined Shell

Acoustic stealth performance is one of the important indicators to measure the advanced nature of modern submarines.It is of great engineering significance to study the mechanism of submarine structural vibration,and to reduce the submarine navigation noise.For the vibration of submarine structures,the propulsion shaft is simplified as a multi-span beam,and the hull is simplified as a conical-cylindrical shell combined model.The submarine is thus abstracted into a coupled shaft-conicalcylindrical shell model.Bearings are simplified as springs and shaft-shell continuous conditions are established at the bearing connections.A semi-analytical calculation method for complex coupled vibration performance of submarine structures was developed.The vibration characteristics of the system under the external excitation of the propeller and the hull are mainly studied.First,the equations of motion for the shaft and shell structures in the model are established.The Euler-Bernoulli beam theory and the one-dimensional wave equation are used to establish the equations for the lateral and longitudinal vibrations of the shaft,respectively.The equations of motion for cylindrical and conical shells are established using Flügge shell theory.The wave propagation method and power series method are used to represent the displacement functions of cylindrical and conical shells,respectively,and the numerical method is used to solve the equations.Triangular transformation and other methods are used to establish the continuity conditions between conical-cylindrical shells at the junction of conical-cylindrical shells.A vibration model of a conical-cylindrical composite shell in fluid was established.Based on the foregoing,radial bearings and thrust bearings are simplified as springs,and lateral and longitudinal continuous conditions between the shaft and the shell are established respectively.The lateral and longitudinal vibration equations of the shaft-shell coupled system are formed simultaneously,and their correctness is verified by the finite element / boundary element method.The lateral and longitudinal vibration characteristics of a shaft-shell coupled system under vacuum and water are mainly studied.The effects of point excitation,boundary conditions,bearing stiffness,and shell thickness on vibration characteristics are discussed.Finally,the experimental model of the small-scale shaft-shell coupled system is designed and processed.Based on the existing loading and measuring devices,a shaftshell coupled model vibration test is designed and tested.The correctness of the semianalytical method is verified,and the causes of the errors are analyzed.