Theoretical Analysis And Experimental Study On Dynamic Vibration Absorber Based On The Second Kind Of Levitation Characteristics Of Ferrofluid

Ferrofluid is a new functional material with magnetic properties and flow characteristics.The levitation characteristics of ferrofluid is widely used in the field of vibration control.Compared with the traditional dynamic vibration absorber,the ferrofluid dynamic absorber is sensitive to the inertia force,without the fatigue of metal elements.So it can be more effective to control the low frequency and small amplitude vibration of the flexible elements,such as solar panels in the spacecraft.Based on the second kind of levitation characteristics of ferrofluid,this thesis designs a novel type of dynamic vibration absorber.The influence of stiffness coefficient on the damping performance of the ferrofluid vibration absorber is studied.The specific work of this thesis is as follows:(1)The vibration model with two degrees of freedom is established.Based on the magnetic charge model,the magnetic field distribution in the ferromagnetic fluid dynamic absorber and the magnetic force between the permanent magnets are theoretically derived.(2)The design scheme of the ferrofluid dynamic vibration absorber is presented.By theoretical calculation and static magnetic field simulation,the magnetic field distribution and the magnetic force between permanent magnets under different magnetic pole arrangement modes are compared.The correctness of the theoretical model is verified.On this basis,the magnetic pole arrangement of permanent magnets is selected,and the structure and size parameters of the inertial mass block and the shell are determined.(3)The magnetization characteristics of ferrofluid is calibrated by experiments,and the variation of viscosity of ferrofluid with magnetic field intensity is studied.Through the flow field and magnetic field multi-physics coupling analysis,the influences of the viscosity of ferrofluid and surface tension coefficient on the surface distribution of ferrofluid is analyzed.The results show that the influence of the viscosity and the surface tension coefficient on the surface distribution of the ferrofluid in stable state can be ignored.Besides,the of the surface of ferrofluid coincides with the contour of magnetic induction intensity.The surface distribution of ferrofluid with different geometry parameters is observed,and three kinds of levitation conditions of the inertia mass block are obtained.(4)The formulas for calculating the vertical force and restoring force exert on the inertia mass block are derived.The influence of geometric parameters on the vertical force of the inertia mass block is discussed,and the levitation height of the inertia mass block is obtained.Base on the levitation height,the restoring force of the inertia mass block is measured,and the stiffness coefficient of the ferrofluid dynamic absorber is obtained.The research shows that the stiffness coefficient of the ferrofluid dynamic absorber decreases with the decrease of the mass of ferrofluid and the increase of end gap.(5)The influences of the geometric parameters and the initial amplitude on the damping performance of the ferrofluid dynamic vibration absorber are studied.The results show that in the range of selected parameters,when the end gap is 38mm and the mass of ferrofluid on each permanent magnet is 5.5g,the damping performance of dynamic vibration absorber is best,the attenuation percentage of which is 93.69%.