Mixed Elastohydrodynamic Lubrication Theory And Wear Analysis Of Bearings

Wear is the common problem of bearings in engineering practice.Wear,roughness and other surface topographies have great influence on the lubrication state between the two contact surfaces.At the same time,pressure and thermal effect are also important factors affecting the lubrication state.It is of great significance to study the wear of the bearing under the thermal elastohydrodynamic lubrication.In this dissertation,based on the elastohydrodynamic lubrication theory,the characteristics of wear with bearings surface roughness is studied systematically through theoretical modeling and analysis.The main research contents are as follows:Based on the mixed elastohydrodynamic lubrication,the contact behavior of oil-lubricated bearing within a certain range of worn width is investigated.By using the finite difference method,the Reynolds equation with oil lubrication is solved,and the partial derivatives in the Reynolds equation are substituted by some line algebraic equations.The contact behavior of bearing is analyzed under different wear depths and rolling speeds.The numerical results indicate that the variation of film thickness in the wear zone is significantly related to the rolling speeds.The position of maximum film thickness varies with the rolling direction of bearing.The influence of worn depth on the bearing contact behavior is more evident when the rolling speed is lower.Based on mixed thermal-elastohydrodynamic lubrication and energy conservation law,the wear of the thermoelastohydrodynamic lubrication of point contact rolling bearings is investigated.By establishing the temperature-pressureviscoelasticity equation of the lubricant,the interaction between temperature and bearing pressure is considered.The Reynolds equation is solved by the finite difference method and the composite direct iterative method,and the oil film thickness and pressure are obtained.Scanning step method is used to solve the energy equation and energy boundary conditions are solved by scanning step method,and the numerical solution of interface temperature is obtained.Through numerical solution,the effects of surface roughness and wear area on film thickness,pressure and surface temperature under different entrainment speeds are discussed.The lubrication characteristics of functionally graded wear bearing shell based on mixed elastohydrodynamic lubrication condition are studied.Combined with elastohydrodynamic lubrication theory,two-dimensional Fourier transform method and Papkovich-Neuber potential function,the displacement and stress equations of the functionally graded bearing shell are achieved.The functionally graded material is transformed into multi-layered structure by uniform layering method.The effects of different surface topography and functional gradient index on the lubrication and stress distribution of rolling bearings are analyzed.The results show that the variability of surface can increase the local pressure of the bearing,and the functional gradient index can reduce the value of the rigid body displacement.