Study On Rolling Fatigue Damage Expansion Mechanism Of High Temperature Bearing Steel

Spindle bearing is the supporting part of the rotary spindle of aero-engine.It is mostly used in complex and harsh working conditions,such as the continuous effect of high and heavy load,super high dn value,high temperature,high and low temperature alternation,and the change of lubrication state of the friction pair.These will cause high shear stress and high surface contact stress of the contact pair,resulting in accelerated rolling contact fatigue damage of the contact pair material and early fatigue failure.With the continuous development of the aviation industry,the temperature of the main shaft bearing of the aero-engine exceeds the working condition,and the dn value exceeds the working condition.Under this condition,the life performance and reliability of the main shaft bearing of the aero-engine have become an important factor restricting the development of the aero-engine.With the continuous improvement of structural optimization and dynamic calculation of spindle bearing,the main means to improve the bearing performance is to explore the material performance.At present,the phase transition temperature of bearing steel used in China is above 800 °C,which can avoid the performance degradation of ordinary bearing steel under high temperature conditions,and is widely used in aero-engine spindle bearings.The rolling contact fatigue test of G13Cr4Mo4Ni4 V and 8Cr4Mo4 V is a way to explore the fatigue performance of materials by simulating the service environment of the main shaft bearing of aeroengine through bench test.Before carrying out the rolling contact fatigue test,it is necessary to improve the lubrication,cooling and monitoring system of the ball-and-rod rolling contact fatigue tester and adjust the dynamic characteristics of the tester,so that the tester can reliably and stably carry out the rolling contact fatigue test,and realize the performance index of the ball-and-rod contact pair with the maximum Hertz contact pressure of 4.8 GPa and the rotational speed of 10000 r / min.The control program is written based on Lab VIEW software to realize the state monitoring of the testing machine,so that the testing machine can complete the signal acquisition,data analysis and signal storage,and realize the automatic shutdown of the testing machine in abnormal state and fatigue failure.The rolling contact fatigue life test of 8Cr4Mo4 V test rod was carried out.The stability and reliability of the test machine were high,which met the test standards.The rolling contact fatigue test of G13Cr4Mo4Ni4 V and 8Cr4Mo4 V bearing steels was carried out by the improved ball-rod rolling contact fatigue testing machine,and the fatigue test was completed for 700 h.The rolling contact fatigue characteristics of G13Cr4Mo4Ni4 V and 8Cr4Mo4 V bearing steels under mixed lubrication were studied.The microstructure of rolling contact fatigue failure was observed by scanning electron microscope,and the fatigue failure mechanism was analyzed.The three-parameter Weibull distribution curve was drawn according to the fatigue life obtained from the test.By establishing the fatigue damage accumulation model based on lattice finite element,the evolution process of fatigue crack initiation,expansion and failure of high temperature bearing steel under test conditions is analyzed,and the fatigue damage evolution test is carried out.The microstructure morphology of the surface and subsurface of the rod raceway,the evolution of fatigue crack and grain size in the process of fatigue damage are observed.