Analysis Of Oil Film Characteristics Of Hydrodynamic Bearing Considering Thermal Effect And Surface Roughness

Hydrodynamic sliding bearing is widely used in the main shaft support of rotating machinery,its working surface is not ideal smooth surface,the machined bearing working surface often has uneven surface geometry characteristics,and the working surface of the bearing will change due to wear in the service process.The surface roughness is the most commonly used parameter to describe the surface geometric characteristics.When the amplitude of the surface roughness reaches the same magnitude as the minimum oil film thickness of the bearing,the influence of the surface morphology on the performance of the sliding bearing cannot be ignored.In addition,the thermal effect will also affect the oil film characteristics.In this paper,the effects of thermal effect and surface roughness on the lubrication characteristics of hydrodynamic bearing oil film are analyzed and verified by experiments.The main research contents and results are as follows:Firstly,the Reynolds equation,the energy equation,the viscosity temperature equation and the corresponding boundary conditions of the oil film pressure distribution,the temperature distribution energy equation,the viscosity temperature equation and the corresponding boundary conditions were established.On this basis,the finite difference method was used to discretize the control equations.The pressure distribution and the temperature distribution of the hydrodynamic bearing under different surface roughness were obtained by iterative calculation,and the characteristic parameters were further calculated.Secondly,the dynamic friction pairs with different surface roughness were designed and manufactured,and the test platform was built to measure the friction resistance and friction coefficient of the dynamic friction pairs under different speed,temperature and surface roughness.The results show that when the temperature of lubricating oil increases from 20 ? to 40 ?,the friction resistance and friction coefficient of sliding bearing become smaller under the same load;when the roughness increases from 0.312 ?m to 0.350 ?m,the friction resistance and friction coefficient increase with the increase of rotating speed under the same load;with the increase of roughness,the upward trend of friction resistance bearing capacity curve is more obvious;under the same load,the greater the roughness,the greater the friction resistance and friction coefficient.When the load is 400 N,the friction coefficient of 0.312 ?m specimen is 38.3% lower than that of 1.714 ?m specimen.Comparing the theoretical calculation results with the experimental results,the two are basically consistent,which verifies the correctness of the numerical calculation.At the same temperature,when the roughness value of the bearing is small,the roughness has no obvious influence on the bearing characteristics;when the roughness value is large,the oil film temperature increases with the increase of the roughness;under the same roughness,the temperature has significant influence on the bearing characteristics;when the roughness value is less than 0.2 ?m,the friction resistance can get a small range,so it is recommended to use the surface roughness Ra ? 0.2 ?m working surface of hydrodynamic sliding bearing.