Dynamic Modeling Of Angular Contact Ball Bearing With Local Defects Considering Multiple Factors

With the improvement of modern machinery manufacturing technology,the intelligent manufacturing equipment industry has also made rapid development.NC machine tool is a basic,complex and strategic material in modern industry,which has the development trend of high performance,multi-function,customization,intelligence and green.The motorized spindle is the kernel component of NC machine tool,and its dynamic distinguishing features are the critical factors influencing the smooth and highspeed rotation of NC machine tool.Angular contact ball bearing(ACBB)has the distinguishing features of simple structure,high rotation accuracy,low noise,so it can be used as a supporting part of NC machine spindle.When the main shaft is running,it is inevitable that plastic deformation,crack,pitting,peeling and other failure forms of the bearing raceway or rolling body surface will occur due to improper lubrication,contact stress,temperature change and other factors,resulting in bearing failure.When the bearing fails,it will not only make the whole spindle system vibrate,but also seriously affect the working performance of the whole equipment,resulting in the equipment failure and abnormal operation.Therefore,it is necessary to consider the thermal effect,impact force and elastohydrodynamic lubrication of rolling bearing,and build the dynamic model of ACBB with local defects,the dynamic performance of ball bearing with local defects and the effect law of various elements are studied.and the vibration properties of ACBB with local defects are deeply studied.The research contents are as follows:(1)A generalized representation model of time-varying displacement excitation of local defects in ACBB is established,the discrimination methods of different local defect contours is proposed,the evolution process of local defects and its displacement excitation mechanism are studied.Considering the influence of time-varying displacement caused by bearing defects on dynamic response characteristics,a fault dynamic model of ACBB is built based on Hertz contact theory.The dynamic equation is solved and the vibration response signal is acquired.The results show that the rectangular local defects will eventually evolve into trapezoidal shape.The change trend of displacement excitation induced by different defect morphology is different.Compared with the length of the local defect,the width has a greater influence on thedisplacement excitation.(2)According to the time-varying displacement excitation model of ACBB with local defects,the instantaneous impact force function related to defect size and bearing speed is established.Then,based on Hertz contact theory and impact force function,the dynamic calculation method of ACBB with local defect in outer ring is presented.Finally,the vibration characteristics of the ball bearing with faults are investigated,and the dynamic response of the bearing under diverse working conditions is analyzed.The results show that with the raise of defect size and load,the fault characteristics frequency of bearing is unchanged,but its amplitude increases.With the raise of speed,the frequency of bearing also increases and the amplitude changes.The increase of three factors will aggravate the vibration of the bearing.(3)A comprehensive stiffness model of ACBB considering the effect of elastohydrodynamic lubrication is proposed.At the same time,the oil film thickness considering the spin motion is combined with the contact deformation,and the sliding friction is introduced.The dynamic model of angular contact ball bearing with local defects is set up.The vibration characteristics of the ball bearing with faults in the presence of sliding friction are researched.Finally,the effect of different parameters on the dynamic response of the bearing is analyzed.The results show that the minimum oil film thickness decreases and the oil film stiffness increases when the spin is considered,which will slightly increase the total contact deformation and friction of the bearing;When the influence of friction is considered,the amplitude of bearing fault characteristic frequency increases.With the increase of defect size and load,the frequency of bearing fault characteristics remains unchanged,but its amplitude increases;With the increase of spindle speed,the frequency of bearing fault characteristics increases and the amplitude changes.