Characteristic Of Funcetional Parameters Of Surface Roughness On Guide Way And Its' Effects On Tribological Properties

Friction exists in everywhere,and almost all of the friction process is accompanied by wear.One of the most significant reasons for mechanical system failure is the excessive wear of contact surfaces.Ideal smooth surface does not exist,and amount of micro-strucutures and macro shape errors are included in all real surface.The existence of these features can affect the continuity of lubricating oil film,contact stress,pressure distribution,and so on.Accordingly,surface topography plays an important role for the wear resistance,corrosion resistance,and other performance of parts.As one of the main processing methods for parts finish machining,grinding has significant effect on tlhe formation of surface topography.However,most of the researches on grinding surface characteristic only pay attention to two-dimisional(2D)profile parameters or few commonly used three-dimisional(3D)surface parameters.Unfortunately,the surface performances can not be intuitively reflected by these surface parameters,and it is also unrelizable to combine surface topography and its'tribological properties effectively.Therefore,it has important realistic significance and engineering value to carry out a series of researches aiming at characteristic of functional parameters of surface roughness on guide way surface,tribological behaviors of surface functional parameters under different lubrication state,and other related topics.Based on the usability of sliding guide way surface,this paper characterized guide way surface using surface functional parameters,and finished 3D solid modelling for real surface topography.And then,the tribological behaviors of surface functional parameters under different lubrication state were analyzed.On this basis,optimization and prediction modelling about grinding parameters,surface topography,and tribological properties was carried out.The mainly researches are as follows.First,one surface amplitude parameter(arithmetic mean deviation Sa)and three surface functional parameters(surface bearing index Sbi,core fluid retention index Sci,and valley fluid retention index Svi)were selected to characterize grinding surface.Effects of grinding parameters(wheel linear speed Vs,workpiece linear speed Vw,grinding depth ap,longitudinal feed rate fa)on surface topography parameters were analyzed.The study demonstrated that the most significant factors of four grinding parameters influence surface topography parameters are Vs?fa?fa?fa,respectively.Moreover,based on these researches,prediction model for surface topography parameters by grinding parameters were obtained using BP neutral network.After that,in order to solve the difficulty of the measurement for surface functional parameters in engineering,the relationship between surface functional parameters and surface amplitude parameters(Sa,Sz,St)were modeled respectively,and the verification of these models were conducted.Secondly,3D rough surface was modeled accurately using wavelet transform(WT)based on the measured data of real rough surface topography,which the detail features were filtered out.and the shape features were extracted,coalesced,and reconstructed.In view of the status that the selection criterion of wavelet functions are confused and low accuracy,a new selection criterion of wavelet functions used in WT,which is based on the whole reconstruction error of signal after WT,definition of reconstructed image,deviation of arithmetic average deviation Sa between reconstructed signal and original signal,and simplification of asperities after wavelet analysis was confirmed and applied.This selection criterion has the characteristics of simple calculation,fine accuracy,and well adaptability.Based on the feature of multi-scale analysis for WT,the surface topography was decomposed into three components by analysis for the mutational point of root mean square deviation and wavelet energy in different scale level.The study demonstrated that the first component is mainly affected by tool wear and workpiece material.The second component is determined by machining parameters.The third component is mainly influenced by machine tool condition and machine environment.After that,a universal rough surface finite element model was built by extracting the second component signal.Thirdly,effects of surface topography micro structures on tribological behaviors were researched using the method combining finite element simulation with verification experiment under different lubrication state.Moreover,the surface micro structures were optimized.Under hydrodynamic lubrication state,influence of surface topography parameters(Sa,Sbi,Sci,and Svi)on friction force Fy*,mean pressure Fz',and friction coefficient f were analyzed and discussed.The research reveals that the most significant factor affecting friction force Fy*and friction coefficientfare Sa and iSvi,while the influence of Sa and sbi on mean pressure Fz*are more significant.On this basis,an accurate prediction model of surface topography parameters on friction force was finished with the use of multiple linear regression analysis.Subsequently,surface topography micro structures were optimized and redesigned aiming at different tribological properties.Under mixed lubrication state?first,the calculation equations of flow factors,which are used in average Reynolds equation,were fitted and revised aiming at grinding surface,and the new calculatioti equations were applied in the numerical simulation.Afterwards,in view of the influence of velocity,load,and micro-peaks deformation on lubricating oil film,effects of surface topography parameters on solid-solid contact area,friction coefficient,and surface flattening were studied,and the changing reason of surface friction performance was analyzed from surface modification mechanism.On this basis,single target optimization and multiple targets optimization for surface parameters were both conducted to obtain exceptional lubricating performance.The results show that the multiple targets comprehensive optimization results in smaller friction coefficient,solid-solid contact area,and surface flattening,so the comprehensive performance is superior to other surfaces.Finally,the relationship among grinding parameters,surface topography,and tribological behaviors was modelled.Based on surface topography parameters(Sa,Sbi,Sci and Svi),a reverse optimization model for grinding parameters(Vs,Vw,fa,and ap)was finished using the genetic algorithm-artificial neural network method,and the accuracy of this model was verified.It is helpful to determine suitable machining parameters fleetly and accurately based on the specific surface roughness parameters of friction pair.Moreover,optimization design of grinding parameters aiming at different performance,such as friction properties,bearing of oil film,surface flattening,et al.,was achieved using this model under hydrodynamic lubrication state and mixed lubrication state respectively.A verification experiment was conducted to examine the credibility and accuracy of the optimization results.Accordingly,the successful application of this optimization model shows its engineering value and universality.The works finished by this paper are beneficial to the accurate characterization of sliding guide way surface topography,which is closely related to the tribological and lubrication properties.Meanwhile,by using the tribological behavior model of the functional parameters of surface roughness and the optimization model of grinding parameters aiming at surface friction properties,the parts surface abrasion can be reduced effectively,and the service life of products can be extended enormously.Therefore,this research has significant practical value and realistic meaning.