Research On Contact Characteristics Between Rolling Element And Variable Radius Raceway Of Cageless Ball Bearings

Cageless ball bearing is extensively applied in magnetic bearing as back-up bearings because of its large number of rolling elements,good stiffness and high bearing capacity.When the magnetic field disappears,the rotor will fall on the backup bearing and the back-up bearing can reduce dropping impact of trochanter.However,for the cageless ball bearing,there is contact among the rolling elements.To solve this problem,the team have designed a kind of variable radius raceway in outer ring locally to make rolling elements disperse automatically and reduce wear between rolling elements.However,the contact state between rolling element and raceway changes because the variable radius raceway changes the shape of the original bearing outer ring.Therefore,in this thesis,stress betwixt the variable radius raceway and rolling element of cageless ball bearing is studied.By analyzing the contact properties betwixt rolling element and the variable radius raceway,and utilizing the methods of theoretical pattern,numerical solution and test checking,to research transformation of stress of variable radius raceway,and then to analyze the wear of the variable radius raceway which leads to discrete failure of rolling elements.Firstly,contact state betwixt the variable radius raceway and rolling element of cageless ball bearing is analyzed,and the effect element of contact stress betwixt the variable radius raceway and rolling element are determined.Then,the contact stress distribution pattern betwixt rolling element and variable radius raceway in ideal state is set up utilizing Hertz theory.The stress model between the rolling element and the variable radius raceway considering the simultaneous action of load and centrifugal force and frictional force is set up on the established ideal state model.Lastly,combining with the studies,the effect elements of contact stress are determined.Secondly,the effect of rolling element load on alternating stress of the variable radius raceway.And the change of alternating stress of rolling element under different motion states is analyzed,to determine the stress variation law of rolling element passing through variable radius raceway at different time intervals.The above theoretical equations are solved by combination with MATLAB programming,and the influence of the determined factors on the contact stress between the variable radius raceway and rolling element is researched.Finally,the maximum value of alternating stress on the variable radius raceway is determined,and combined with Archard model,the wear failure analysis and calculation of cageless ball bearing with variable radius raceway are carried out.Finally,for verifying the correctness of the contact theoretical model betwixt the variable radius raceway and rolling element,the flexible model is set up and then transformation regular pattern of stress when the rolling element enters and exits the variable radius raceway is analyzed.The contact test of cageless ball bearing is carried out on bearing measuring machine.Variable radius raceway of cageless thin-walled ball bearing is machined and the equivalent contact strain test is made to confirm the correctness of the contact theoretical model betwixt the variable radius raceway and rolling element of cageless ball bearing.In this thesis,the contact characteristics between the variable radius raceway and rolling element of cageless ball bearing is researched,and the effect factors and its influence law on the contact stress between the variable radius raceway and rolling element are fixed.The maximum value of alternating stress and the discrete failure time of variable radius raceway caused by wear is obtained.This research has great significance to the layout and majorization of variable radius raceway of cageless ball bearing.