Research On The Friction Characteristics Of Water-lubricated Rubber Bearing And Vibration Of Shafting System

Water-lubricated rubber bearings are important components of the propulsionshafting system in ships. The mutual friction between the rubber bearing and thepropulsion shaft can cause radiation noise through propeller excited by shaftingsystem or shell structure excited by support configuration. For propulsion shaftingcontaining water-lubricated rubber bearings, the coupling vibration mechanism ofpropeller-shafting-supporting system is very complex and not yet fully understood.The main reason for this question is the theoretical and experimental research is stillnot done enough. Therefore, it is necessary to do theoretical and experimentalresearch on the friction characteristics of water-lubricated rubber bearing and thefriction-induced vibration of shafting system.Concerning the problem of water-lubricated rubber bearing friction excitedvibration in shafting system, this paper mainly discusses the inherent characteristics ofrubber bearing and shafting system, as well as the effects of friction on shaftingvibration, which combines theoretical analysis, numerical simulation and testverification methods. The main research contents are given in detail as follows:In Chapter1, the background and significance of the study are discussed first.Then it summarizes the research status of the water-lubricated rubber bearings, rotordynamics and other aspects at home and abroad.In Chapter2, the material properties and stiffness characteristics ofwater-lubricated rubber bearing are first introduced. The methods to obtain them arethrough material tensile tests and finite element method respectively. Then thecorresponding fixture application of rubber bearing is designed to do experiments ofbearing stiffness, which can be used to verify the accuracy of the calculation results.The results of this chapter indicate the nonlinear stiffness property of rubber bearings.In Chapter3, the natural characteristics of multi-span continuous beam andmulti-span shaft, including modal frequencies and mode shapes, are given usingtransform matrix method. Thus, with the help of this method, the characteristics of bending vibration and torsional vibration analysis on shafting system can be obtained.In order to verify the validity and accuracy of the method, this chapter gives twoexamples to compare the results acquired by transform matrix method and finiteelement method, which confirms the consistency between these two methods.In Chapter4, it describes that the coupling between nonlinear friction andbending-torsion vibration can induce self-excited vibration in shafting system withwater-lubricated rubber bearing. The present researches are mainly based onsingle-point bearing to establish the dynamic model, which cannot analyze theinfluence of distributed bearing force and bearing inclination on the vibrationcharacteristics of shaft system. In order to solve this problem, this part of the thesisdevelops the dynamic model of a shaft system, which is based on distributed bearingmodel and velocity dependent friction represented by Stribeck curve. The equation ofmotion is derived using Lagrangian approach and Modal Synthesis Method. Usingnumerical method, it analyzes the relationship between the nonlinear dynamicresponse and the system’s physical parameters. What’s more, the effects of contactforce, rotational speed and the inclination of bearing are also discussed. According tothe simulation results, the self-excited vibration in shafting system can be easilyobtained for the inclined bearing if other conditions, like contact force, rotationalspeed and friction parameters, are the same.In Chapter5, it mainly introduces the design and working principles of thewater-lubricated rubber bearing friction testing system, including power drive controlsystem, loading system, rotor-bearing system, lubrication system, measurementsystem, etc. Then it discusses the friction and vibration experiments on this testingsystem. The result shows that the friction and vibration characteristics ofwater-lubricated bearing can be affected by parameters like loading force, speed,bearing material, etc.In Chapter6, the whole work of this thesis is summarized. Then it discusses thedeficiencies of the thesis and what needs further study, etc.