| The friction between components of mechanical equipment is one of the causes of mechanical failure and energy consumption,and the use of tribology knowledge to reduce and prevent the friction is an effective way to solve these problems.Along with the development of the electromagnetic technology,mechanical equipment is needed to work in magnetic field environment,which can affect friction of components.Therefore,the study of friction properties of material under the influence of magnetic field is very necessary,to ensure that mechanical equipment can work stably and accurately in magnetic field environment.This thesis takes magnetorheological elastomers as study object.Magnetorheological elastomer /copper as a pair,the experimental platform is used to study the influence of magnetic induction intensity,magnetic particle volume ratio and stress on magnetorheological elastomer friction properties.Based on the friction theory of elastomers and the mechanical properties of magnetorheological elastomers,the two parameters of magnetic particle volume ratio and magnetic induction intensity are introduced into the friction theory,which can partly explain the experimental phenomena.The main work of this thesis is as follows:1.This thesis expounds the significance of tribology research on reducing resource consumption,prolonging the service life of the mechanical,and introduces the research status of magnetic field of tribology.It analyzes the advantages and disadvantages of several ways of applying magnetic field.It introduces the characteristics of magnetorheological elastomers briefly.Subsequently,several existing problems in this field are discussed and the main work of this thesis is put forward.2.Starting from the principle of friction,this thesis puts forward design scheme of the experimental platforms.The experimental conditions,study content,the interference of magnetic field on the sensor and other requirements are fully considered in the design scheme.This thesis puts forward the design schemes of two kinds of sliding friction testing machine and a rolling friction testing machine.Considering study progress,feasibility and economic factors,the design scheme of push friction test machine is decided to implement.According to the design scheme,after mechanical calculation,the key components are selected.According to the physical dimension of selected components,3d simulation design of the experimental platform is designed by SolidWorks software,which verified the feasibility of design scheme.Then purchase equipment and set up the experimental platform.3.Under the condition of light load and low speed,the anisotropic and isotropic magnetorheological elastomers friction experiments are carried out.Experimental data show that anisotropy and isotropic magnetorheological elastomers show similar friction properties.When ferromagnetic particles volume ratio is less than 20%,the friction coefficient decreases with the increase of the magnetic induction intensity;When ferromagnetic particles volume ratio is greater than or equal to 20%,the influence of magnetic field on the friction coefficient is small.From the general trend,the friction coefficient decreases with the increase of the ferromagnetic particles volume ratio,and increases with the increase of pressure,but a little part doesn't conform to the trend.4.On the basis of elastomers friction theory,combining with magnetorheological effect of anisotropy magnetorheological elastomers,the friction properties of anisotropy magnetorheological elastomers is studied.The friction mechanism of elastomer is analyzed.Then a conclusion that the friction coefficient of elastomer is proportional to the loss factor is obtained.Based on the fact that friction is associated with the shearing action of contact surface,it is necessary to analyze the shear modulus of anisotropy magnetorheological elastomer.Under the effect of magnetic field,the shear modulus of anisotropic magnetorheological elastomers can be divided into zerofield shear modulus and magnetic-induced shear modulus.The relationship between the zero-field shear modulus,magnetic-induced shear modulus and ferromagnetic particle volume ratio,magnetic induction intensity is derived.Zero-field shear modulus and magnetic-induced shear modulus as parameters,Kelvin model of anisotropic magnetorheological elastomer is established.By analyzing Kelvin model,the relationship between magnetic induction intensity,ferromagnetic particle volume ratio and the loss factor is obtained.Then the zero-field shear modulus and magnetic-induced shear modulus are introduced into friction theory of anisotropic magnetorheological elastomer.The theory can explain the phenomenon that the friction coefficient decreases with the increase of magnetic induction intensity and ferromagnetic particles volume ratio. |
PDF Full Text Request