Mechanical Modeling And Damping Research Of Asperity In Elastic-plastic Deformation Stage

There are a lot of joint surfaces in the mechanical structure,which makes the mechanical system no longer continuous.It will cause the deviation between the actual performance and the design requirements of the mechanical system,and even affect the normal use of the mechanical system.Therefore,it is important to study the joint part.The research of joint surfaces has great significance in theoretical and engineering application.When the mechanical system is loaded,a small relative motion is generated between the surfaces,so that the mechanical joint will store energy with energy consumption,which means that stiffness and damping exist simultaneously.There are a lot of asperities on the joint surface,so it is necessary to study the contact characteristics of one single asperity,which is the basis for the study of the static and dynamic characteristics of the joint surfaces.The deformation of asperity contains elastic stage,elastic-plastic stage,and plastic stage.Many scholars have studied the elastic-plastic contact of single asperity mainly by numerical fitting and finite element simulation,and established the mechanical model which contains both elastic and plastic deformation mechanism.In this paper,the elastic plastic deformation stage of the asperity is treated ideally by elastic mechanics,and the theoretical elastic model of asperity in the elastic-plastic deformation is established.Compared with the finite element models which are widely used,the loading and unloading mechanical characteristics and damping mechanism of a single asperity in contact with rigid plane during elastic-plastic deformation are studied.The main work includes the following:Firstly,The Hertz theory is extended from the elastic deformation stage to the elastic-plastic deformation stage.Combined with the distribution law of contact pressure and elastic mechanics,the theoretical elastic contact pressure distribution of the single asperity in the elastic-plastic deformation stage is proposed.The theoretical elastic model of a single asperity in the elastic-plastic stage is first established,in which the dimensionless relationships of contact load,contact area,the mean contact pressure and interference are revealed.Secondly,the loading models of the asperity are studied.The KE finite element loading model is expounded.The further deduction about the average contact pressure is made by analyzing the results of KE model.Then compared KE model with theoretical elastic model,the reasons for the difference of contact load,contact area and deformation caused by different deformation mechanisms in the elastic-plastic stage are analyzed.Thirdly,the unloading models of the asperity are studied.The unloading model established by Etsion is introduced.The theoretical elastic unloading model is also derived.A comparative study about the theoretical elastic unloading model and Etsion unloading model is carried out.It is verified that the theoretical elastic unloading model is reasonable for solving the unloading process of single asperity contacted with a rigid plane.Finally,the damping mechanism of the joint surface is elaborated.The classification of damping which is according to the loading and unloading condition of the surface is put forward.Based on the energy principle,a damping energy dissipation model for the contact between a single asperity and a rigid plane is established,which fills the blank of solving method for damping energy of single asperity under static load.The damping methods for different kinds of joint surfaces are also discussed.