Research On The Mechanical Performance And Fatigue Life Of Hub Bearing Based On The Theory Of Elastohydrodynamic Lubrication

At present,the third generation hub bearings are widely used in middle and high grade passenger cars and heavy trucks.Because of its bad operating conditions and novel structure,higher requirements for the bearing capacity and fatigue life of the hub bearing are raised.At the same time,for rolling bearings,which are separated from rolling body and raceway by lubricating oil film,the thickness of oil film and tangential friction of oil film have a significant influence on the mechanical properties and fatigue life of hub bearings.The elastohydrodynamic theory can effectively calculate the thickness of the oil film and the tangential friction of the oil film.Therefore,it is of great theoretical and engineering significance to study the mechanical performance and fatigue life of the automobile hub bearing based on the theory of elastohydrodynamic lubrication.This paper takes the third generation hub bearing as the research object.Under two conditions of the combined effects of three forces(radial and axial load and bending moment)and pure bending,the contact load and deformation between the rolling body and the inner and outer raceways are derived.A more accurate calculation model of contact load distribution is proposed.The circumferential distribution of contact load and contact angle of wheel hub bearing under different working conditions is analyzed: the difference of the internal load distribution between the wheel bearing and the two working conditions is small.On the basis of the distribution of the internal load of the hub bearing,the contact fatigue of the raceway and the rolling body of different position angles is considered.A modified L-P model for the fatigue life of the third generation hub bearings is obtained by the use of the product law.The influence of bending moment on bearing life under two operating conditions is analyzed.At the same time,the fatigue life model of the third generation wheel hub bearing lubricated is corrected based on the ISO281-2007 life correction calculation method and the two amendment to the lubrication phenomenon.Finally,the bending fatigue test of the hub bearing was carried out by the rotary bending fatigue test machine.The results of the test are compared and analyzed.The error of the theoretical value calculated by the proposed fatigue life model is less than 10%,which proves the validity of the bearing life model in this paper.The geometric model of the third generation hub bearing unit is established.Using ANSYS Workbench,the contact pressure in the different position angle and the yield shear stress of the grease are considered to set up the friction contact in the finite element model.The finite element analysis of hub bearing is carried out under the condition of bending test.Based on the results of finite element stress analysis,the fatigue life of hub bearing is simulated by Fatigue Tool module,and the location and the minimum life value of fatigue failure of hub bearing unit are determined.The correctness of the finite element model and the fatigue simulation analysis results are verified by comparison with the experimental results above.Finally,considering the centrifugal force,gyroscopic moment and fluid resistance force,including friction to oil film elastohydrodynamic lubrication theory based on nonlinear,hub bearing quasi dynamic equations is established and a pure bending condition of the third generation hub bearing the quasi dynamic analysis model is built.A numerical calculation of hub bearing under different speed conditions is carried out.The pseudo dynamic parameters such as normal contact load,contact angle and tangential friction of oil film are studied,and the influence of rotational speed on each pseudo dynamic parameter is obtained.