Construction And Experimental Study On The Universal Theory Of Surface Texture Hydrodynamic Lubrication

In recent years,as a kind of effective anti-friction and anti-wear method applied to the surface of friction pair,surface texture has been continuously developed and innovated,especially with the deepening of bionic tribology research,the research on surface texture has reached a new level height.There are many kinds of surface textures,different sizes,various arrangements,and the application conditions vary widely.Different surface textures form the different hydrodynamic lubrication mechanism.How to choose the appropriate surface texture according to different working conditions is the key to exert its antifriction and antiwear properties.In this thesis,the mathematical model of hydrodynamic lubrication is established through theoretical analysis,and the key variables of the mathematical model are solved by simulation.The experimental results are used to verify and check the mathematical model to explore the mechanism and basis of different surface textures.The purpose of selecting the optimal surface texture.In terms of theoretical analysis,this thesis uses the Navier-Stokes equation as the theoretical cornerstone,sets the Couette flow as the model boundary condition,and establishes the mathematical model of hydrodynamic lubrication based on the actual experimental conditions.Since there are no variables in the fluid mechanics equation that indicate friction and friction coefficient,it is necessary to relate it to parameters such as friction coefficient through an intermediate formula.In the solution of the intermediate formula,it is necessary to fully consider the dimensions of the test piece in the actual experiment,the size of the grinding piece,the loading force and the rotational speed to ensure the accuracy and identity of the mathematical model.After transforming and simplifying the established mathematical model of hydrodynamic lubrication,the key variables related to speed are unknown,and it is not easy to measure in actual experiments.It is necessary to obtain the variable value through simulation.In terms of simulation,this thesis uses SOLIDWORKS software to establish threedimensional models of V-shaped,composite,grooved and circular textures based on actual experimental conditions.The hydrodynamic lubrication effect is formed by the surface texture of the moving friction pair was simulated by FLUENT,and the tribological properties of different surface textures were analyzed.The simulation results show that the V-shaped texture has strong pressure bearing capacity,but the improvement of the fluidity of the lubricating oil is limited.It is suitable for medium-speed and high-load working conditions.The composite texture is made of grooved and circular nested,which can withstand the load of a certain strength can ensure the fluidity of the lubricating oil,but the range of action of the two is limited.The grooved texture has strong correlation between different textures,which can effectively improve the flow speed,but the pressure bearing capacity is weak,suitable for medium-speed and low-load.The circular texture has the largest average dynamic pressure value,and the lubricating oil can form a high pressure zone above the texture to ensure that it can maintain oil film integrity when subjected to large loads,and is suitable for high load conditions.When the key variables are solved,the different surface texture data obtained by the simulation are imported into MATLAB for fitting,and the key variable equation is obtained.In the friction and wear experiment,the surface texture was processed by laser etching to the surface of YT15 alloy steel,and the friction and wear test was carried out in the MMG-10 friction and wear tester.The experimental factors select the loading force and the rotation speed,the loading force selects 4 levels,and the rotational speed selects 6 levels.The results show that the friction coefficient of V-texture decreases when the loading force increases,and the friction coefficient is small and stable under high-load,which is the same as the simulation result;the friction coefficient of composite texture will increase with the increase of rotation speed.However,the friction coefficient is small and stable when the loading force is 100 N,150N,which indicates that it is suitable for medium and high-speed,medium-load conditions.The friction coefficient of the groove texture does not change greatly when the loading force increases.But the exception is when the rotation speed increases,the friction coefficient will be reduced,indicating that the groove texture is suitable for medium and high speed and low load.The circular texture has the lowest friction coefficient at medium and low speed,medium and high load,which is suitable for high load conditions,which is consistent with the simulation results.In the mathematical model solving,the key variables obtained from the simulation are substituted into the mathematical model of hydrodynamic lubrication established by theoretical analysis,and the friction coefficient obtained from the experimental results is compared with the results obtained by the universality theory.The wear characteristics are basically the same in terms of the order of the wear and tear.There are 10%-40% errors in the friction coefficient values,and the error values vary with the working conditions and texture types.