Research On The Vibration Control Method Of Ship Stern

With the development of modern ship design in the direction of lightweight,large scale and rapid,the vibration problem of ship is becoming more and more serious.Especially for the stern part of ship,because the propeller and power equipment always are arranged in the stern of ship,the vibration excitation of the stern is too large that causes serious vibration problems.Therefore,the research on the characteristics of ship stern vibration and vibration control methods has become a hot spot and focus of ship engineering research.However,at present,the control methods of ship vibration are mostly confined to structural design and strengthening.Facing the increasingly severe vibration problem,this passive vibration control method has gradually been unable to meet the requirements of ship engineering.Based on the above background of ship hull vibration,this paper studies the vibration characteristics of the stern of a ship,and carries out relevant vibration control methods,which also provides some reference for future ship vibration control.In this paper,theoretical analysis and numerical calculation methods are used to study the vibration characteristics of the stern of a ship,and on this basis,research on the control methods of the stern vibration is carried out.Firstly,the variable cross-section composite beam system of the ship's stern is established,and the analytical solution of the vibration of the ship's stern beam is deduced theoretically by the transfer matrix method.Then,three finite element models of the stern part of the ship,namely,the beam model,the three-dimensional model and the mixed model of the stern part,are established by the finite element software.The vibration modes of the stern part of the ship are calculated and the differences of different calculation models are compared.In this paper,the acoustic-solid coupling method is used to apply the attached water quality of ship hull,and its accuracy is verified by comparing with the classical Lewis attached water quality theory.By applying the calculated propeller excitation to the finite element model of the stern section,the vibration response of the stern section of the ship under the excitation of the propeller is calculated and analyzed,and the stern vibration is evaluated by using the relevant ship vibration standards.Based on the research and analysis of the stern vibration characteristics of the ship and the vibration control methods of other engineering industries,two methods for the stern vibration control of the ship are put forward in this paper,the one is the whole modal vibration of the stern treated by dynamic vibration absorber and the another is the vibration response of the local deck of the stern treated by MR ship-column.The Dynamic vibration absorber is widely used in Construction Engineering,whichs working mechanism is mainly depending on the dynamic effect of the mass of the slave system attached to the main system,which transfers the vibration of the main system to the slave system so as to reduce the vibration of the main system.In this paper,the basic principle of dynamic vibration absorber is introduced in detail,and a marine dynamic vibration absorber system for the first two modes of stern part is designed.The system includes base structure,spring damper and vibration absorber mass.Based on the relevant design specifications,the whole system is designed from the perspective of practical engineering application,including all parameters and the connection between components.Form.Magnetorheological(MR)column is a new method proposed in this paper to control the vibration of ship's stern deck.The MR damper is the core component of the MR damper.By combining with the design of the hull column structure,the MR damper can form a vibration reduction system which can take corresponding measures to reduce the vibration of ship's stern deck.In this paper,the theoretical basis and working mechanism of MR damper,which is the core component,are introduced in detail,and the relationship between its working performance and current is studied.Based on the relevant specifications of hull design,a MR damper column structure for a certain section of the stern of the ship is designed.The main design contents include the column structure,spring structure,MR damper and connection form.Plan.In this paper,finite element simulation is used to calculate the effect of the designed dynamic absorber and MR damper column on the stern vibration and the stem deck vibration.The simulation results verify the effectiveness of the two vibration control methods.