Research On Fatigue Influence Factors And Bearing Stiffness Of Elastohydrodynamic Lubricated Deep Groove Ball Bearing

Elastohydrodynamic lubrication(EHL)is the common lubrication type that takes place in the contact areas of the rolling element bearings.The lubrication film separates the rolling element and raceways completely,which is very different from the dry contact and has a significantly influence on the contact stress and mechanical properties in rolling element bearing.The two important problems including contact fatigue life and bearing stiffness are worthy to be investigated deeply for lubricated rolling element bearing.For fatigue life prediction of lubricated rolling element bearing,the lubrication factor(determinated by the ratio of the minimum lubricant film thickness between rolling elements and raceways and the rms roughness of the contacting surfaces)is usually introduced to represent the effect of lubrication film on the roller-raceway contact fatigue life.But the effects of the skidding between rollers and raceways and the difference of rough surface profiles(geometrical morphology)at the roller-raceway contact at different times due to the running of the bearing are seldom considerated.For bearing stiffness under EHL condition,most works mainly focus on the discussion of radial stiffness coefficients but seldom on the analysis of bearing stiffness matrix of dimension five which can demonstrate comprehensively the dynamic behavior of bearing.Taking deep groove ball bearing as research objective,the two above mentioned problems are analyzed in this paper.The main works are shown as follows:(1)Based on the EHL numerical algorithm,the lubrication characteristics at ball element-raceway contact for deep groove ball bearing is analyzed.The effect of the skidding on the contact fatigue life of the ball element is discussed.The variation of the fatigue lives of the volumes at different depths under the lubricated ball element surface is analyzed.(2)The characteristics of distribution of film pressure,shear stress,film thickness and von Mises stress under the lubricated surface are analyzed for the rough raceway surface.The influences of surface roughness and surface profiles on the contact fatigue life of the raceway are discussed.The variation of fatigue lives of micro volumes at different depths under the lubricated raceway surface with the depths and surface roughness is investigated.The shorts of the lubrication factor in the load-life model are pointed out by analyzing the contact fatigue lives for the lubricated ball element-raceway contact on the condition of skidding and roughness surface.The current works are helpful for modifying the lubrication factor and improving the accuracy of prediction of load-life model.(3)Based on the principle of minimum potential energy derived from the theory of elasticity,a fast and reliable numerical scheme,energy method,is proposed to solve rolling element bearing displacements under dry contact condition.Energy method links bearing potential energy and bearing displacements.The potential energy formula of the bearing is established as the function of the bearing displacements and the global optimization algorithm is applied to solve the bearing displacements.The energy method takes full advantage of the ability of the global optimization algorithm to seek the initial estimates automatically and yield the correct solution fast and reliably,and also guarantees that bearing displacements under EHL condition can be obtained efficiently and accurately.(4)The influence of EHL on the five dimenssional stiffness matrix for deep groove ball bearing is analyzed.The central film thickness and elastic deformation for lubricated ball element-raceway contact at two different bearing speeds are computed.Based on the contact force and mutual approach relation,the mechanical model for lubricated deep groove ball bearing is set up and the five dimenssional stiffness matrix is derived.The effects of EHL on stiffness coefficients are discussed when different combination of loads are loaded on the bearing.The results show that the effect of EHL on bearing stiffness can be ignored if the bearing is loaded only with radial force,but EHL has a remarkable effect on the coupling stiffness coefficients when the combination of loads is applied on the bearing.