Modeling Research On Contact Characteristics Of Ellipsoidal Microconvex Mechanical Contact Surface

The mechanical contact surface is common in the mechanical structure,and the contact characteristics of the contact surface will directly affect the performance,machining accuracy and stability of the mechanical processing equipment.From the microscopic point of view,the machined part surface is not smooth,and there are a large number of different shapes of convex bodies.In this paper,the asperity is equivalent to an ellipsoid,and the deformation characteristics of each stage of a single ellipsoid asperity and the normal contact characteristics including the elastic-plastic deformation stage are studied.The fractal models of the normal contact stiffness and the normal contact damping of the ellipsoid asperity contact surface considering the elastic-plastic contact are established,and the simulation comparison and analysis with the classical model and the experimental data are carried out to verify the correctness and effectiveness of the theoretical model.The main research work is as follows :(1)The asperity on the rough surface is equivalent to an ellipsoid.Aiming at the shortcomings of the normal contact model of the existing ellipsoidal asperity,the analytical contact mechanics model of the elastic-plastic stage of a single ellipsoidal asperity is constructed,and the contact characteristics of the asperity in the deformation process are continuous and smooth at the critical point.Using fractal theory and joint density distribution function of contact area and eccentricity,a fractal model of normal contact stiffness of ellipsoidal asperity considering elastic-plastic contact is established.The established model was compared with the classical model and experimental data,and the results showed that the model was closer to the experimental data,indicating the accuracy of the model.(2)The characteristics of contact load in elastic-plastic stage of ellipsoidal micro-convex are studied and analyzed,and the elastic potential energy and plastic deformation loss energy of ellipsoidal micro-convex in elastic,elasticplastic and plastic deformation stages are calculated respectively.Combined with the energy dissipation mechanism and normal dynamic model of contact surface normal contact damping,the fractal model of ellipsoidal micro-convex normal contact damping considering elastic-plastic contact is established.Through numerical simulation,the influence of fractal parameters of rough surface,normal contact load and material plasticity index on normal contact damping and damping loss factor is analyzed.(3)By comparing the simulation of the established model with the existing model,it is found that the normal contact load of the contact surface decreases first and then increases with the increase of the fractal dimension,and the normal contact load is the smallest at the fractal dimension D = 2.51.Normal contact load increases with the increase of fractal roughness parameters.The normal contact stiffness of the contact surface increases with the increase of fractal dimension,and increases first and then decreases with the increase of fractal roughness parameters.The normal contact damping of the contact surface increases with the increase of fractal dimension and fractal roughness parameters.The damping loss factor of contact surface increases with the increase of fractal dimension,and increases first and then decreases with the increase of fractal roughness parameter.