Research On Fatigue Life And Reliability Of High-speed Train Axle Box Bearing

With the rapid development of high-speed railway technology,high-speed train performance continues to increase.Axle box bearing as the key mechanical parts of high-speed train traction drive system,its service environment is complex,the impact of load is severe.The quality of state during operation directly affects the safety of the train.At present,high-speed train axle box bearings all imported from abroad.Bearing localization has become a bottleneck to limit the development of high-speed train in China.In order to meet the needs of the new generation of high-speed train development,it is urgent to develop the axle box bearings which could adapt to operating conditions and operating maintenance environment of high-speed train.Only in-depth studying of the bearing fatigue damage mechanism,can be able to reasonably guide the bearing design to ensure the accuracy of the bearing life reliability.Centering on the high-speed train axle box bearing fatigue life and reliability,the study carried out the following work with measured data:(1)The structural characteristics of the axle box bearing and the radial and axial loads in the operation are analyzed.Two load test schemes of axle box bearing are put forward:the axle box spring and the tumbler are made into force sensor to test the load of the spring and the tumbler,and the bearing load is obtained by analysis of the spring and the tumbler load.In another way,the outer ring of the bearing is slotted,then the measuring point is arranged at the slot,and the bearing load is recognized by the stress signal of the measuring point.Based on the study of bearing load identification method,the test scheme of bearing load of high speed train axle box is determined and applied to the load tracing test of high speed train.It provides data support for bearing reliability evaluation and fatigue life prediction.(2)The mechanical analysis model of double row tapered roller bearing is established by numerical method and the finite element method respectively.The load distribution characteristic of the bearing is studied,and the influence of different structural parameters and load parameters on the contact load distribution,deformation and contact stiffness are analyzed.The results show that the load distribution characteristics obtained by the two methods are basically the same,the finite element method has advantages in terms of computational accuracy,and the numerical method has advantages in terms of computational efficiency.(3)Based on the measured load data of axle box bearing,the fatigue life prediction model of bearing under time varying load is established by combining traditional bearing fatigue life theory and linear cumulative damage criterion.Then,the fatigue life of the axle box bearing is calculated by using this prediction model and the traditional theoretical life calculation model.The results show that the fatigue life of the new model is smaller than that of the traditional methods under the same load and operation condition,which shows that the new life prediction model is relatively conservative and safe.In addition,the concept of axle box bearing per kilometer damage is raised.And the damage value per kilometer of high-speed train is calculated under the conditions of in and out maintenance library using the linear damage theory.The results show that the per kilometer damage in the condition of daily in and out maintenance library with low speed is much higher than that of the normal high speed operation condition,which shows that the bearing condition is worse when the train is under the conditions of in and out maintenance library,and this condition can not be neglected when calculating the bearing life.(4)The finite element contact model of tapered roller is established.The contact stress state is simulated by finite element software.And the relationship between bearing load and stress is studied.Then the simulation results are compared with Hertz theoretical results.Based on the bearing load-stress transfer coefficient and the structural stress fatigue criterion,the fatigue life evaluation method of axle box bearing is put forward.And the evaluation of the bearing is carried out by using the proposed life assessment method.(5)According to the interference relationship between the equivalent stress and the fatigue strength,the equivalent stress-fatigue strength reliability model of the bearing is established.The reliability model directly reflects the relationship between the reliability and the stress and fatigue strength of the structure.Under the condition of known stress and fatigue strength correlation data,the model can be used to calculate the reliability at any time(service life).In addition,the reliability evaluation method of bootstrap and maximum entropy combining weighted norm is proposed,and the bearing reliability and its confidence interval are evaluated by bearing fatigue life data.In summary,theoretical analysis,finite element and numerical simulation and experimental research methods are used to study the load identification,internal load distribution,deformation and stiffness of the double row tapered roller bearing of high speed train axle box,and the fatigue life prediction and reliability of the bearing were systematically studied.The research results can provide the theoretical direction for design,manufacture,using and maintenance of high speed train axle box bearings,which possess an important theoretical significance and application value in engineering.