Research On Tangential Static And Dynamic Characteristic Parameters Of Anisotropic Contact Surfaces

"Made in China 2025" plans a strategic blueprint for high-end equipment manufacturing.In the high-end machinery and equipment,the mechanical interface is a key factor to consider,and the static and dynamic contact stiffness and damping of the part joint surface affect the performance of the whole machine.50% of the machine stiffness is due to the stiffness of the joint surface,and the overall machine damping is 50%~80% comes from the damping caused by the contact of the contact surfaces.Therefore,it is very important to study the contact stiffness and damping of the mechanical interface.Generally,the researches of scholars mainly focus on the isotropic surface assumption to calculate the normal contact stiffness and damping parameters of the joint surface.There are few studies on the tangential contact characteristic parameters of the anisotropic surface in practical conditions.In this paper,we first establish a joint probability density function that characterizes the height of anisotropic random surface asperities,and then establish a theoretical model of tangential static and dynamic contact of microscopic asperities based on the combined effects of normal and tangential loads.The contact stiffness and damping model are established on the entire joint surface and finally verified by experiments.Its main content is as follows:(1)First,the characteristics of anisotropic surfaces are described.Secondly,based on the theories of Buczkowski and P.Ranganath Nayak et al.,the relationship between power spectral density and autocorrelation functions is derived using stochastic process theory and Fourier transform theory.Obtain the description form of the parameters of each variable of the micro-convex,and use two-dimensional random variables to represent the height distribution of the micro-convex,and finally establish the joint probability density function of the random distribution of the height of the surface micro-bump,and lay the theoretical foundation for the following chapters.(2)On the basis of the normal loading force,simultaneous tangential static loads are applied,and the KE model,Mindlin and Fujimoto theories are used to establish the three stages of normal contact(elasticity,elastoplasticity,plasticity)and tangential contact state(stick-slip,slippery)The unloaded tangential static contact stiffness model of the frictional behavior of the coupled surface.Through the MATLAB simulation of the non-dimensionalized model,the effects of normal contact load,normal deformation amount,plasticity index,friction coefficient,surface hardness and other factors on the tangential static contact stiffness are analyzed,and the surface contrast of isotropic and anisotropic properties are performed.The study shows that the tangential static contact stiffness with different isotropic and anisotropic surface contact is similar with each factor;the tangential static contact stiffness is increased under the factors such as normal contact load and normal deformation.With the increase,and under the normal contact load caused by the same external load,the tangential static stiffness presents a nonlinear increase with the increase of plasticity index.(3)Based on the tangential static contact model,consider the effect of applying tangential dynamic excitation loads,introduce tangential simple harmonic dynamic displacement,establish the tangential dynamic contact stiffness model of micro convexity,and then obtain the micro convex according to Mindlin and Fujimoto theory.The energy dissipation and equivalent viscous damping of the body during a vibration cycle are extended to the entire joint surface.Through immeasurable,The simulation model was simulated by MATLAB.The effects of normal load,tangential relative displacement amplitude,excitation frequency,friction coefficient,surface hardness on the tangential dynamic contact stiffness and contact damping of the interface were analyzed,and the isotropy and heterogeneity were performed.The contrast.The results show that the tangential dynamic contact stiffness and the tangential contact damping change law are similar under the isotropic and anisotropic contact with different surface textures;the tangential dynamic contact stiffness with normal contact load,excitation frequency,and dynamic relative The displacement amplitude,surface hardness and other variable values increase while the tangential contact damping increases with the increase of the normal contact load,and decreases with the increase of the excitation frequency,relative displacement amplitude and hardness.(4)The surface morphology of the experimental specimens was measured to obtain the isotropic and anisotropic surface morphology parameters.On the combined surface experimental platform,the tangential surfaces of the 45 steel paired joints of turning,milling and EDM were tangentially processed.Static and dynamic experiments obtained the relationship between tangential static contact stiffness and normal load,and experimental lawsbetween tangential dynamic contact stiffness and contact damping and normal contact load,dynamic relative displacement amplitude,and excitation frequency,Finally the experimental data curve fitting is compared with the theoretical model simulation results.research shows:Milling(anisotropic)Machining the surface The texture is clear,and the EDM(isotropic)machined surface has no noticeable texture.The tangential static and dynamic contact stiffness and damping model considering the anisotropic and isotropic surface contact are the same as those obtained by experiment.The tangential static contact stiffness of the isotropic surface is greater than the anisotropic surface stiffness,dynamic contact stiffness and damping to the opposite.