Fatigue Crack Initiation Mechanism And Reliability Evaluation Method Of Rolling Bearing Based On Microcrystalline Model

Aviation bearings have a harsh working environment and high-reliability requirements.With the development of science and technology,the demand for high-performance bearings in the aviation industry increasing.The bearing's service performance is affected by the complex working conditions of the bearing and the microstructure of the bearing steel.At present,the related research is seriously separated for bearing and bearing steel.Combining the bearing's complex working conditions with the bearing steel's microstructure to reveal the bearing's failure mechanism is the key to achieving an accurate personalized design of high-performance bearings.In this paper,first establishes a multi-field coupling dynamic model of the bearing to obtain the dynamic load information.Then establishes a numerical model containing the bearing steel's microstructure characteristics,revealing the mechanism of the bearing microscopic crack initiation under actual working conditions from the perspective of mechanics and lattice motion.This work will provide theoretical guidance for the bearing's production,and it provides an effective method for studying the micro-evolution process under complex working conditions.The main contents are as follows:(1)A dynamic model of bearing heat-fluid-solid multi-field coupling is established.The bearing's initial motion conditions are obtained to establish the bearing model by solving the quasi-dynamics method.A parameterized bearing thermal-solid coupling dynamic model is established on the ABAQUS platform by Python scripts.It lays the foundation for establishing a multi-field coupling model and reliability evaluation.A bearing fluid lubrication model was established based on the CFD method,and the lubricant pressure distribution during the bearing operation process was calculated.Finally,a thermal-fluid-solid multi-field coupling dynamics model is established by the calculation results coupled to the thermal-solid coupling model through the grid mapping method.The dynamic load information of the bearing under thermal-fluid-solid coupling is obtained by solving the model.(2)The micro characterization experiment of SKF 6406 bearing(M50 steel)was carried out.The microstructure characteristics of bearing steel are determined,and the grain heterogeneity is produced.The program to establish the bearing steel microstructure model was compiled based on the Voronoi method.And the bearing macro and microstructure models containing micro grains were established.(3)The bearing microscopic stress distribution characteristic is calculated by the multi-field coupling dynamic load is applied to the bearing microstructure characteristic model.The results show that the grain heterogeneity will lead to the microscopic stress distribution in the bearing is inhomogeneous,the stresses at the boundaries of the adjacent grains change abruptly,and the more significant the difference in the mechanical properties between grains is,the more pronounced the change.The apparent stress mutation appears around inclusions due to the mechanical properties of inclusions are higher than that of all kinds of grains in the surface layer of the rolling element.And massive difference of stress components around some inclusions.(4)The response surface model was established by the BBD method.A multivariate random parameter evaluation method was proposed by the response surface method combined with the Monte Carlo method and the SPEA coefficient.The influence of inclusions on the stress distribution of the bearing steel microstructure was quantitatively evaluated.The results show that the distance between the inclusion and the surface of the rolling element has a significant effect on the microscopic stress distribution,and the effect of the inclusion morphology is minimal.(5)The microscopic failure mechanism of the rolling element surface layer is further revealed from the lattice movement's perspective based on the crystal plasticity finite element method.The results show that the grain movement around inclusions with a more massive stress component difference is larger.The lattice motion analysis and mechanical analysis results are mutually corroborated,which fully proves that inclusions with large stress component differences will develop into fatigue cracks.According to the results of micromechanics and motion,a calculation model of contact fatigue life is established to predict the bearing's life.