Study On Normal Contact Stiffness And Damping Model Of Solid-liquid Bonding Surface

In recent years,the modernization level of the machinery industry has been increasing at a high speed,and it has been developing in the direction of high speed,high precision,high efficiency,integration,and intelligence.Therefore,the requirements for the static and dynamic performance of mechanical equipment are becoming more and more demanding.There are a large number of joint surfaces between the mechanical parts of machine tools and other mechanical parts.The joint surface stiffness accounts for about 60%of the machine stiffness,and the joint surface damping accounts for more than 90%of the whole machine damping.It can be seen that the mechanical joint surface is static.The dynamic contact characteristics have important academic research significance and practical application value for the manufacturing precision and quality control of high-end equipment.In the past,scholars mainly studied the characteristic parameters based on the interface of no medium,but there are few researches on the characteristic parameters of the medium-bonded surface,it can be named the solid-liquid interface,under actual working conditions.In this paper,the contact stiffness and contact damping of the solid-liquid interface basic characteristic parameters are studied.Under normal static conditions,starting from the microscopic single closed crater and single micro-convex modeling analysis,the high probability density function of the random surface is extended to the whole j oint surface to obtain the normal static contact theoretical calculation model;Under the condition,combined with the static micro-convex contact loading and unloading model,and the fluid extrusion film lubrication model considering the surface roughness effect is established,and the theoretical calculation model of normal dynamic contact is obtained.The main research contents are as follows.(1)Under the assumption of a single rough plane,the lubrication state of the solid-liquid joint surface is determined according to the film thickness ratio,and then the closed oil sump concept is derived based on the mechanical-rheological model,and the single closed oil pit contact model and micro under the static condition will be established.The contact model of the elastic,elastoplastic and plastic deformation of the convex body is connected in parallel to the entire joint surface to obtain a static contact model of the solid-liquid joint surface.After the model is dimensionless,matlab simulation is carried out to obtain the influence of contact deformation and contact load on contact area and contact stiffness.The results show that the variation between the dimensionless contact characteristic parameters of the solid-liquid interface is basically the same as that of the no-media interface.With the contact deformation and contact load increasing,the contact area and contact stiffness increase nonlinearly.Under the same contact deformation or contact load,the solid-liquid bonding surface contact stiffness is numerically larger than the no-medium bonding surface,but the contact area is smaller than the no-medium bonding surface;and under other conditions,the viscosity of the lubricant is greater.The solid-liquid bonding surface contact load and contact stiffness are larger,and the solid contact area is smaller.(2)Unlike the solid-liquid interface contact model under normal static conditions,the fluid portion exhibits extrusion stiffness and extrusion damping under normal dynamic conditions.Firstly,based on the Reynolds equation,the average Reynolds model considering the influence of surface roughness is established.Meanwhile,the contact probability factor and the joint surface shape correction coefficient are introduced to complete the model.The fluid part model under normal dynamic load is obtained,which is the theoretical basis for the study of the subsequent solid-liquid interface normal dynamic contact model.(3)The dynamic contact of solid-liquid interface refers to the application of a normal dynamic exciting load on the basis of the equilibrium position of the normal static load,showing the normal harmonic dynamic displacement Δδ.For the solid contact part,based on the static contact model of the joint surface,it is possible to establish a contact stiffness model under excitation load,and then the contact load during static unloading is counted,and then the statistical contact model is statically unloaded by establishing the j oint surface method,and the normal dynamics of the surfaces in contact with each other is obtained by combining the energy method.Viscous damping.For the liquid contact part,the dynamic extrusion stiffness and extrusion damping calculation model of the oil film is established by solving the analytical solution of the above fluid part model.Finally,the excitation contact stiffness and contact damping of solid-liquid interface under different normal relative displacement amplitudes,excitation frequencies and touch loads are simulated and analyzed by matlab.The research shows that for the excitation contact stiffness of the solid-liquid interface,the initial contact decreases with the increase of the preload.Compared with the static contact stiffness,there is a contact load critical point,which is smaller than the excitation contact stiffness.Large,greater than this point,the static touch stiffness is large,meanwhile it increases with the increase of the normal relative displacement amplitude,linear law at low load,and the nonlinear load is nonlinear;it increases linearly with the increase of the excitation frequency,and the larger the load,the smaller the linear slope.For normal contact damping,it increases nonlinearly with the relative displacement amplitude and contact load increase.As the excitation frequency increases,it shows a slight decrease.The oil film damping phase is one to two orders of magnitude larger than the micro-convex contact damping.(4)Experimental verification of the features in different states of the solid-liquid interface.After EMD treatment,the rough bonding surface is selected for pairing,and Kunlun Tianhong lubricant is selected as the lubricant medium in the solid-liquid bonding surface.The surface of the rough surface was measured by Leica white light interferometer,and the shape parameter values were obtained.The variation law between the static force change with displacement and the contact load,the normal excitation force change with displacement and the energy consumption and preload,the amplitude and the excitation frequency of the solid-liquid interface are obtained by the characteristic parameter experimental platform,and the theoretical simulation results are obtained.Conduct a comparative analysis.