Study On The Effect Of Ball-Raceway Contact Movement On Raceway Fatigue Life

Rolling contact fatigue is one of the main failure forms of rolling bearings.The stress and strain distribution on the surface and subsurface of the ball and raceway affect the fatigue life of the bearing.The friction between the ball and the raceway greatly affects stress and strain distribution of the raceway.The motions between the ball and raceway in a ball bearing involve rolling,gyroscopic and spin slide.These complex motions cause different friction between the rolling element and raceway.In order to improve the durability of the bearing,it is necessary to understand the influence of the motion and friction between the ball and the raceway on the fatigue life of the rolling ball bearing.For this reason,based on point contact theory,structure fatigue theory,and linear elastic fracture mechanics,the effect of ball and raceway contact motion on the fatigue life of rolling bearings is studied.The main research contents and conclusions are as follows:First of all,the equivalent model of ball-raceway contact was studied and established based on the Hertz contact theory for the convenience of finite element calculation.The raceway in the real model is curved,while the contact surface in the equivalent model is a cylindrical surface.The contact stress in the equivalent model is consistent with the contact stress distribution in the real model.At the same time,the stress distribution of the raceway surface and the subsurface in the two models is the same.Therefore,the equivalent model can be used in experiments and finite element simulation instead of the real model.The raceway after equivalence is more simplified.At the same time,it can greatly improve the efficiency of finite element simulation.The stress components concerned in this paper are maximum Mises stress,maximum Tresca stress,and maximum orthogonal shear stress.Secondly,the stress distribution of the raceway under various motions with the friction coefficient from 0 to 0.3 was studied.When the friction coefficient is 0,the maximum values of the three stresses are on the subsurface.As the friction coefficient increases,the maximum Mises stress and the maximum Tresca stress get closer to the surface until they appear on the surface.Based on different structure fatigue life algorithms,the raceway’s fatigue crack initial life of the cases with the friction coefficient 0,0.05,0.1,and 0.3 were studied.The raceway’s fatigue life based on ISO 281-2007 bearing life theory is studied.Results show that the friction force on the contact surface has some influence on the stress and fatigue life to a certain extent.Especially,the ball’s spin has the greatest influence on the stress distribution and fatigue life of the raceway.Crack initiation life is more conservative than ISO 281-2007 bearing fatigue life.Thus,for the cases of heavy load and high friction coefficient,the effect of the friction force of ball-raceway contacts can’t be neglected.Finally,based on the three-dimensional fatigue fracture software FRANC3 D,the crack propagation life of the raceway is studied.The crack propagation angle is calculated based on the maximum shear stress criterion,and the crack propagation life is calculated based on the Paris formula.When the friction coefficient is 0,the initial crack angle is 45o.On the symmetrical surface of the raceway,the crack first propagates upward and downward at 45o relative to horizontal.It then expends upward in the direction of approximately 60o.At the same time,it expend downward in a direction of approximately 30o.There is a trend of horizontal expansion.The life from crack initiation to the raceway surface is 12912 times.