Research On The Nonlinear Vibration Characteristics Of Spiral Bevel Gears In Propulsion Shaft Of Azimuth Thrusters

The spiral bevel gear transmission system has been widely used in ships,aviation,aerospace,automotive and other engineering fields,whose performance have a great influence on the whole system.Especially the gear transmission system of ship propulsion shafting,there are not only its own internal incentive,but also the complex propeller incentive and many other external incentive effects.The requirements such as vibration,noise,reliability and so on,still have limited its application.In order to satisfy the requirements of high velocity,heavy load and high reliability,it is necessary to do the further researches on the coupled nonlinear vibration mechanism and dynamic modeling of spiral bevel gears under complex excitation.This thesis mainly focuses on the nonlinear vibration characteristics of the spiral bevel gear transmission system in propulsion shafting of azimuth thrusters.By using the lumped mass method,the dynamic model of the system is established.The vibration characteristics of the system under the coupling of internal and external excitation as well as the dynamic characteristics resulted from the parametric excitation are studied.The researc h results could provide theoretical guidance for the dynamic research of the multi-stage gear drive system under complex excitation,and provide the optimization design for the vibration and noise reduction of the propulsion shafting of azimuth thrusters.The main works and achievements are as follows:Based on the principle of load contact analysis,taking 5 pairs of meshing teeth in a pair of spiral bevel gears as the object,the time variant meshing stiffness of spiral bevel gears is accurately solved wi th the help of ABAQUS software.The 8 degree of freedom nonlinear dynamic analysis model of spiral bevel gear pair is established,which not only considering the influences of external excitation,such as torsional and axial excitation of propeller and mai n engine excitation,but also considering some other internal excitation,such as time-varying mesh stiffness,backlash,dynamic transmission error,then the dynamic differential equations of the system are obtained.Through Runge-Kutta numerical integration method,the dynamic response of the system is obtained.Taking the influence of mutual coupling between two-stage spiral bevel gear pairs and the influence of the torsional stiffness of the connecting shaft on the system into account,based on the study of dynamic model of single-stage spiral bevel gear pair,the dynamic model of 13 degree of freedom of two-stage spiral bevel gear transmission system is established according to the propulsion shafting model of azimuth thruster.The dynamic differential e quations of the system are obtained.After analyzing and solving these equations,the factors that may affect the state of the spiral bevel gear transmission system are analyzed,especially the influence of meshing frequency,the influence of internal fact ors,such as time-varying stiffness,error excitation,and other external factors such as load excitation are studied.Through researches,it can be found that the meshing frequency have a great influence on the steady response of spiral bevel gear,so the steady-state response can be changed by adjusting the meshing frequency.In addition,it was also found that two-stage gear transmission system are coupled with each other and the torsional stiffness of connection shaft have significant effects on vibration response of the front and rear gear pairs,it could through changing materials and length of the connecting shaft to choose appropriate torsional rigidity.