Parameters Optimization And Surface Anti-damage Design Of Three Point Contact Ball Bearing For Aeroengine Mainshaft

As the core supporting component of an aeroengine,mainshaft bearing should not only meet the requirements of long service life and high reliability,but also continuously adapt to the continuous development of extreme working conditions,such as high speed,heavy load,high temperature,low oil and broken oil and complex cycling conditions.Three point contact ball bearing,as a typical mainshaft bearing type for aeroengine,often suffers from fatigue,pitting,wear and even ring and cage's fracture under complex and harsh working conditions.In addition,multiple failure modes coexist and interconvert with each other,which seriously restricts the life extension and reliability growth of aeroengine bearing.This article mainly from the bearing service condition and structural features,typical failure mechanism,the optimization of structural parameters,the surface anti-damage design and test evaluation,to research on the analysis and verification of the three contact ball bearing design.The design system has important guiding to the the long life parameters optimization and anti-damage design.The typical service conditions,core structure characteristics and typical failure modes of three point contact ball bearings for aeroengines are systematically analyzed.The typical cycle parameters,oil supply mode,structure characteristics and working state characteristics are presented,as well as the macro and micro morphology of the failure modes under service conditions.On this basis,the roller contact analysis model in the main bearing zone is established,the force-thermal coupling response of instantaneous temperature rise,stress distribution and shear plastic deformation of surface material in the main bearing zone is studied,and the causes and evolution process of typical failures such as bearing surface fatigue and wear are analyzed.The results show that the failure of aeroengine mainshaft bearing under well lubrication condition follows the traditional rule the failure is mainly caused by the maximum shear stress.However,when the speed and load are suddenly changed,the oil is cut off and depleted,the bearing lubrication state deteriorates and the friction coefficient increases,which causes the stress and temperature of the contact interface increase sharply and the surface material to undergo plastic deformation accumulation,leading to the wear and failure of the bearing contact surface.Therefore,the design of mainshaft bearing should not only consider the service performance such as dynamic load and lubrication,but also cover the evaluation analysis and optimization design method of bearing anti-fatigue and anti-wear performance.Regard to mainshaft bearing's high speed and micro area contact characteristics,based on dynamics,thermal and finite element analysis method,analyzes the bearing performance under the typical service condition.The three contact performance is analyzed such as maximum contact stress of inner and outer ring,rolling body "drift".The cage movement characteristics,lubricating state,friction power consumption and temperature is analyzed.The results provide the input to parameter optimization and anti-damage design.The results show that under typical service conditions,such as take-off,climbing and cruising,the bearing's three point contact behavior,high-speed performance and lubrication state show the following characteristics of working conditions.Moreover,at high speed,inner ring and cage may cause strength and stability problems.Therefore,the optimization of bearing structure parameters and anti-damage design of working condition envelope are the necessary premise and foundation to maximize the performance and life of three point contact ball bearing.The fatigue and wear failure of the main bearing surface and guide surface of the three point contact ball bearing is closely related to the state characteristics of the typical contact surface of the ring/cage.This article considers the manufacturing process of surface state and material properties,adopts the numerical simulation method and the rough surface membrane system contact analysis method,analyzes the rough surface morphology,the residual stress distribution and surface coating on the bearing performance of the micro contact area,to obtain the rough contact interface of optimal residual stress gradient and the gradient coating structure parameters,provides a quantitative surface anti-damage design input parameters.The results show that the local stress concentration on the rough surface will lead to increase of the optimal residual stress in the subsurface layer,and the extreme position of the optimal residual stress tends to the surface.For the point contact state with low friction coefficient,the optimal elastic modulus of the main bearing surface gradient coating decreases gradually along the depth direction,while at high friction coefficient,the optimal elastic modulus increases first and then decreases.It is preferred that the elastic modulus of the coating increases first and then decreases.The long life optimization design model of three point contact ball bearing with six design parameters is established,and the order of bearing structure parameters' influence on life is analyzed for typical service conditions.The optimal design parameter combination under cyclic conditions is determined.The design software for bearing performance analysis and parameter optimization is developed,which provides a system platform and a fast optimization scheme for bearing optimization design and analysis.The rolling contact fatigue properties of test samples with different surface morphology and residual stress were evaluated by double roller contact fatigue testing machine,and the life correction coefficients of surface roughness and residual stress were determined.Based on the optimized bearing structural parameters and surface state,the trial-production of three point contact ball bearing was completed.The simulated working condition life assessment test of the optimized bearing was carried out by using a high-speed bearing tester.The optimized bearing's life increased from 440 h to 6560 h,which verified the reliability of the optimized design method.