| Propellers and propulsion shafts are the power core of ship operation,and the dynamic characteristics of the propeller-shaft system affect the running state of the ship.At present,abnormal vibration and noise often occur in the process of ship propeller-shaft system operation.Abnormal vibration will affect the stability of system operation,and the appearance of noise also threatens the concealment and safety of underwater vehicle.Therefore,this paper studies the bending-torsional coupled vibration characteristics of the ship's propeller-shaft system under the effect of propeller mass eccentricity,analyzes the relationship between the response characteristics of the system and the external excitation force frequency and system parameters,and explores ways to reduce the system's abnormal vibration,and provides a theoretical basis and method for improving the stability of the ship's paddle-shaft system.In this paper,the following aspects are studied:(1)The finite element modeling method is introduced.The unit of the ship's propeller-shaft system is divided and the modeling method of each unit is given.The units are combined to obtain the overall motion equation of the propeller-shaft system.It provides a modeling basis for the analysis of the coupled bending and torsional vibration characteristics of the system.(2)The method of modal analysis based on ANSYS software platform is introduced.The natural frequency and mode shape of the ship's propeller-shaft system model under free state are obtained by modal analysis.Based on the MATLAB software analysis platform,the natural frequencies of the model are obtained under free state,and the analysis results in MATLAB are compared with the analysis results in ANSYS to verify the correctness of MATLAB modeling.It provides the correct modeling method for the analysis of the bending and torsion coupled vibration characteristics of the system.(3)The scale-down model of the ship's paddle-shaft system is used as the research object to carry out the modal test.The natural frequency and mode shape of the scale-down model is obtained,and the natural frequency and mode shape of the actual model are derived by the scale-down model.The modal correlation analysis between the actual model and the finite element model is carried out to verify the correctness of the finite element model in MATLAB.It provides the correct model for the analysis of bending-torsional coupled vibration characteristics of the propeller-shaft system.(4)Considering the influence of the eccentric mass of the propeller,the coupled bending and torsion dynamics model of the ship's propeller-shaft system is established.The newmark-? method is used to analyze the bending-torsional coupled vibration response characteristics of the ship's propeller-shaft system.The influence of the system rotation frequency on the bending vibration and torsional vibration is studied under the action of the propeller mass eccentricity;the influence of external excitation force on the coupled bending and torsional vibration of the system is studied when the rotation speed of the paddle-shaft system is constant;the influence of the system rotation frequency on the bending-torsional coupling vibration under the action of the external excitation force is studied. |
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