Analysis Of Grinding Surface Topography And Contact Characteristics

This paper is based on the grinding surface of specimen,the statistical characteristics of rough surface profile are analyzed and the relevant statistical parameters are obtained.The factors that affect the contact characteristics of the contact surface are discussed through the calculation of FEM and experimental measurement.The main researches can be presented in following aspects:1 The probability density distribution histogram of rough surface is shown according to analyzing the 45 grinding surface profile data with statistical method,which is shown that 45 grinding surface profile is approximately normal distribution,combining with skewness and gradient of surface and the relevant statistical parameters are obtained.At the same time,the fractal characteristics of the surface are analyzed,and the fractal parameters are obtained with the combination and derivation of the fractal formula and the statistical parameters.Finally,the profile data of 45 grinding surface in different directions are analyzed.It is shown that the statistical law of the grinding surface is anisotropic.2 The high frequency components of rough surface profile are gradually filtered by using median filter,the probability density distribution and spectrum characteristics of rough surface profile are analyzed before and after filtered.The 2D FEM contact model is established based on the surface profile before and after filtered,and the variation of the contact stiffness and contact area with the decrease of the high frequency components of rough surface profile is analyzed.It is shown that the contact stiffness and the real contact area increases with the decrease of the high frequency components(such as the surface texture details),but the real contact area is still smaller than the nominal area.In the meantime,if the texture details of rough surface are rich enough to meet the fractal characteristics,the deformation of contact surface will be plastic even the load is very small.3 A modeling method for the normal elastic-plastic contact of rough surface is presented.Based on elastic-plastic finite element contact model of asperity,normal contact characteristics between asperities of 40 Cr,45,Q235 and rigid plane are studied and unified function expression of contact variables of asperity are built in three stages: elastic,elastic-plastic,plastic deformation.In finite element model,the true stress-strain relationships of the three materials are used and the influences of the different hardening behaviors on contact characteristics of asperity are investigated.Based on the contact analysis of asperity,a normal elastic-plastic contact model of rough surfaces is built by probabilistic statistics method.In the model,the changes of contact variables of asperity depend entirely on results of elastic-plastic finite element and it is unnecessary to divide deformation process of asperity into different deformation stages,which avoids non-continuity and non-smoothness of contact variables between different stages and arbitrariness of choice of interpolation function in elastic-plastic deformation stage.Compared with other contact models,the calculating results of the model are confirmed.4 The probability density distribution and spectrum characteristics of rough surface profile at different scales are analyzed.It is shown that the low frequency components are reduced gradually with the decrease of the surface profile,but it is still much larger than the high frequency components.On this basis,the 2D finite element contact model is established,and the variation of real contact point and contact area ratio with the profile scale is studied.The relationship between contact stiffness and profile scale of rough surface is a power function.The result shows that contact stiffness of the small rough surface can't be used in stiffness calculation of large surface simply.5 The profile features of grinding surface are studied by means of the statistical method,and the average angle of surface profile is about 10 degrees,which is explained by analyzing the degrees of grinding wheel profile and the characteristics of the diamond end.On the basis,the finite element model is built and the relevant experiments are carried out to study the effect of this feature on the normal and tangential contact stiffness.It is shown that the results of finite element and experiment have good consistency,and the stiffness of the contact surface is random(phase difference),but a coupling relationship between the normal and tangential contact stiffness is existing,which is related to average angle of the profile curve and does not change with the friction coefficient and the Poisson ratio.