Research Of Lubrication Property And Surface Sulfurizing Modification Of Bilayer Oil Bearing

Oil bearing is widely used in astronautics,engineering machinery and transportation for its remarkable energy saving and oil self-lubrication.In working process,oil bearing is easy to fail prematurely.And its friction and wear is severe for the contradictory of strength and antifriction performance caused by its porous structure.The bilayer bearing has obvious advantages in improving the comprehensive mechanical and tribological properties by adjusting the porosity distribution between layers.For clarifying the lubrication mechanism and improving the comprehensive mechanics and tribological properties under different lubrication conditions,the mechanism of seepage lubrication,coupled analysis of multi-factors,tribological characteristics and modification of the friction interface were carried out in this paper.The main work and achievements of this paper are as follows:1)The hydrodynamic lubrication model of bilayer oil-bearing system is established,based on the hydrodynamic and seepage theory.The lubrication mechanism of oil film is revealed.Results show that: compared with the single layer oil bearing,bilayer oil bearing can prevent oil infiltrating into the porous medium,and have better lubricating performance.The lubrication performance of the bilayer bearing becomes worse with the increase of the surface thickness or porosity,and becomes better with the decrease of speed or central film thickness.With the increase of speed or load,the temperature of bearing system increase after considering the thermal effect.The lubricating performance is significantly affected by the rised temperature.The friction test results are consistent with the theoretical analysis.And the calculated results of the thermohydrodynamic lubrication are close to the experimental value.2)The average flow model is used to establish the thermal mixed lubrication model of the bilayer oil bearing.The mixed Lubrication mechanism and the influence mechanism are revealed.Results show that: the hydrodynamic pressure mainly occurs in the convergence area,and the contact pressure mainly occurs near the minimum film thickness.The highest contact pressure existed in the minimum film thickness.Under the condition of mixed lubrication,with the increase of the speed,the contact force and the friction coefficient decrease.With the increase of the external load or the surface porosity,the contact force and the friction coefficient increase.Numerical simulation and friction test show that the friction coefficient of the bilayer bearing is lower than that of the single layer bearing under mixed lubrication condition.The lower the porosity of the surface layer,the smaller the friction coefficient.And it is easier to change the lubrication state from mixed lubrication to hydrodynamic lubrication.3)The tribological properties of bilayer oil-bearing under boundary Lubrication condition were studied based on experimental method.The friction and wear mechanism were revealed through detecting the microscopic wear morphology and analysing the pore action mechanism.Increasing surface porosity properly can improve the lubrication performance of the bilayer oil bearing.Compared with the ordinary single layer oil bearing,the bilayer oil bearing with relatively porous surface has good antifriction and self-lubrication performance under higher load conditions.The bearing surface was modified by the low temperature liquid sulphur technology.The liquid-solid synergistic lubrication achieved by the synthetic action of the sulphur modified layer and the stored oil in the pores after vulcanized modified.The vulcanization further improves the tribological performance and carrying capacity of the bilayer oil bearing under the boundary lubrication condition.The unity of high strength and good lubricity of oil bearing is realized.This paper provides theoretical guidance for pore control of bilayer oil bearings under different lubrication conditions.So as to provides certain technical support for realizing the unification of high bearing capacity and good lubrication under different lubricating conditions.