The Effect Of Asymmetric Micro-texture On Lubrication Characteristics Of Friction Pairs

Surface texture is a means to improve lubricity of friction pairs.So far,there are many experiments to study the friction properties of texture,such as friction reduction and wear resistance and there are also some simulations for studying micro-texture wear reduction.However,most of the studies on micro-texture cavitation are focused on symmetrical texture.Empirical values are often used to calculate the cavitation pressure of lubricating oil in simulation study.Most of them only study the influence of texture parameters and working conditions and the strength of cavitation effect.However,the related research is still very limited.Based on the above two points,this study will carry out simulation and experimental research on the effect of asymmetric micro-texture on the lubrication characteristics of friction pairs.The pressure,cavitation phase diagram,bearing capacity and friction coefficient of asymmetric micro-texture under two-dimensional conditions were simulated.A numerical test device was designed to measure the initial cavitation pressure of lubricating oil.A new jet cavitation tube with various pipe diameters and inner walls of micro-channel tubes was used to collect the cavitation effect diagrams under different parameters,and the influence of oil temperature and viscosity on the cavitation effect was considered.The experimental device for observing lubrication and cavitation phenomena between reciprocating friction pairs with asymmetric texture was improved and designed,and the friction coefficient,cavitation phenomena and simulation results were analyzed together.The simulation results show that during friction process,a negative pressure and vortex region is formed inside the texture,and a high pressure zone is generated near the outlet of the texture.The morphology parameters of asymmetric micro-texture affect the magnitude of bearing capacity and friction coefficient by changing the distribution characteristics of pressure and vortex of the lubricant.With the increase of the slope at outlet of asymmetric triangular texture,the original vortex center gradually shifts downwards to the right;meanwhile,a prominent vortex region and a high pressure region are generated near the inlet of the texture.As a result of aforementioned redistribution of pressure and flow field,the bearing capacities gradually increase,while the friction coefficients continuously decline.For the experiment of measuring the initial cavitation pressure of lubricating oil,with the increase of needle diameter in a certain range,the minimum pressure which can produce cavitation effect also increases,and spiral streamlines produce in the micro-channel tube under suitable pressure.With the increase of temperature,the viscosity of the same kind of oil decreases gradually,and the difficulty of cavitation effect increases gradually.For different kinds of oil,under the same conditions,the initial pressure of cavitation induced by the oil with low viscosity is larger.Reciprocating experimental results show that cavitation occurs only when the velocity and load reach a certain level.While the cavitation occurs,the friction coefficient decreases,and with the increase of load and speed,the cavitation phenomenon becomes more intense.The texture perpendicular to the inclined plane of the texture outlet obtain a smaller friction coefficient.With the increase of load,the influence of texture morphology is gradually weakened.