Investigation On Tribological Properties Of Rough Surfaces With Micro-Dimples

Surface texture can significantly improve the mechanical properties of mechanical parts,it has become a hot spot of surface engineering and tribology.In recent years,people study the effect of the texture on the tribological properties,they mostly ignore the impact of roughness.However,when the average film thickness of the lubricating oil film and surface roughness are on the same order of magnitude,the effect of roughness on the lubricating property is not negligible,and it increases with the decrease of the film thickness.Therefore,it has great scientific significance and engineering value to study the effect of roughness on the tribological properties of micro-dimples textured surface.Firstly,the concept of deterministic model is introduced.The sinusoidal wave is applied to the simulation of the rough surface.Based on the mass conservation law,the deterministic model for hydrodynamic lubrication of rough surface is established,calculate the distribution of hydrodynamic pressure by a multi-grid algorithm.Based on the change of the amplitude and wavelength of sinusoidal waves,the influence of roughness on the oil film carrying capacity is obtained.The results show that the two parallel motion slider surfaces with a certain roughness can produce a hydrodynamic lubrication effect and form a lubricating oil film with a certain load carrying capacity.There is an optimum value of the roughness to maximize the bearing capacity,wavelengths of the sinusoidal wave has less effect on the optimum value of the roughness value.The greater the wavelength,the more significant the effect of the amplitude on the bearing capacity.Then,considering the mutual influence of roughness and micro-dimples textures,a deterministic model for hydrodynamic lubrication of micro-dimples textured roughness surface is established.By analyzing the surface pressure distribution of oil film and the average pressure,the influence of the geometrical parameters of the micro-dimples on the bearing capacity of the oil film under the roughness of the sinusoidal model is studied.The results show that the interaction between the two adjacent micro-pit textures can not be simply ignored.The dimensionless average pressure decreases with the increase of roughness in textured sinusoidal roughness surface.The average dimensionless pressure decreases with the increase of amplitude of the sinusoidal wave,but the average dimensionless pressure is almost unaffected by the wavelength.There isthe optimal depth and area density,so that the average dimensionless pressure to the maximumFinally,the tribological characteristics of micro-dimples are tested by the friction pair with conformal contact.The untextured surfaces with different roughness are studied by friction test on MMW-1A friction and wear tester.The Stribeck curves is calculated according to the test results,the results show that the surface roughness has the most obvious effect on the friction performance in the mixed lubrication area.Thus,the greater the roughness value of the untextured rough surface,the smaller the coefficient of friction.Then,the orthogonal test was conducted to study the coupling effect of roughness and micro-dimples’ parameters on the friction performance under mixed lubrication.The results show that the influence of the initial roughness on the surface roughness of the texture is the most important in the mixed lubrication area,followed by the area and the depth of the micro dimples.