Research On Dynamic Mechanism And Experiment Of Rolling Bearings In Strip Mill With Local Defect

Rolling bearing is one of the core parts of strip mill.Its health condition and stability affect the safe operation of the whole machine.In order to meet the needs of users and the market,strip rolling mill is developing towards the direction of high speed,heavy load,high precision and high reliability,which puts forward higher requirements on the bearing capacity,stability and service life of rolling bearings.The excessive axial thrust,rolling force deviation and other unsteady conditions in the rolling process cause the bearing to be in an abnormal bearing environment,which inevitably leads to the characteristics of excessive local stress and high temperature rise.These characteristics lead to bearing cracks,pits,spalling and other local faults,and even bring the bearing locked roller and other serious consequences.Dynamic mechanism is the core basic theory for studying local faults,and the current research focuses on the two-dimensional plane of universal single-row rolling bearings.However,there are few studies on the local fault dynamics mechanism of high-speed and heavy-load multi-row rolling bearings with spatial contact relationship as the core.In order to reveal the mapping relationship between the formation,development and dynamic response of rolling bearing local faults under unsteady rolling conditions,and to detect and suppress local faults as soon as possible,it is urgent to study the dynamic mechanism of rolling bearing local faults in strip mill.It includes the non-uniform contact mechanism of rolling element/raceway which causes the local fault of bearing,the integrated dynamic model considering the interaction of roller,bearing and housing,the dynamic mechanism of the influence of local fault is considered on the basis of the integrated dynamic model,and the typical fretting fault dynamic mechanism in the local fault.The research provides theoretical basis and practical engineering value for ensuring the safe operation of rolling bearings in strip mill.For the rolling element/raceway non-uniform contact mechanism that causes bearing local fault under non-stationary rolling conditions,contact mechanics model of bearing under biased load condition is established.The mechanism of bias load effect formation is revealed by discretizing the load contact area.The rolling element/raceway contact stress peak is simulated.The rolling element asymmetric logarithmic curve shaping method is proposed.The study shows that the non-uniform contact of rolling element/raceway causes the stress peak at the end of rolling element,which in turn leads to local faults such as pits and plastic deformation.The dynamic mechanism of bearing local fault is accurately and rationally analyzed,the roll,bearing and housing interaction relationship is comprehensively considered,and the integrated system dynamics modeling method is proposed.The interaction mechanism of the internal components of the integrated system is revealed By considering the dynamic contact stiffness and dynamic damping of the bearing,the integrated coupled dynamics analysis model of the roll,bearing and bearing seat is constructed.It is shown that the mutual coupling mechanism of the components in the integrated system is revealed by the integrated system dynamics model,and the accuracy of the dynamics model is verified by combining simulation and experiment.The study lays the theoretical model and experimental foundation for the study of the local fault dynamics mechanism.The mapping relationship between the formation,development and dynamic response of bearing local faults is studied.Geometric boundaries and impact forces are mathematically expressed as local fault models are constructed.Based on the integrated dynamic model,the spatial contact relationship between rolling element and raceway is considered,and the dynamic response mechanism of rolling bearing local faults in strip rolling mill is revealed,including dynamic contact deformation mechanism,dynamic contact force mechanism and dynamic relative displacement mechanism.Finite element analysis and experiments show that different local fault types represent the evolution process of weak faults,and the classification of fault types depends on the fault size.The dynamic contact force in the load area will change when the rolling element passes through the fault area.Local faults such as cracks,pits and spalling are defined by the spatial dimension of the fault zone.The dynamic contact force in load zone changes dynamically when the rolling element passes through the fault zone.When the rolling element enters and leaves the fault area,it will lead to the complete impulse response of the bearing system under single fault.When there are many fault areas,different columns of scroll will repeatedly enter and leave the fault area.The evolution mode of axial fretting fault is proposed and the dynamic mechanism of axial fretting fault is revealed according to the extremely special and highly hidden fretting fault type in the local faults of rolling bearings in strip mill.The axial thrust and radial force models causing the axial fretting fault are established.The coupling load distribution is calculated by combining the pre-displacement principle and elastic contact theory,and the evolution mechanism of axial fretting fault under different loads is revealed.The results show that the superposition of multiple loads is the essential factor causing the fretting fault.When the axial thrust is greater than the friction force,the contact area is the total slip,otherwise it is the partial slip.The cross angle of roll system,the position angle of rolling element and the radial load determine the evolution state of axial fretting fault.Finally,the results of local fault dynamics mechanism are applied to engineering practice.The fault data and axial thrust data of the engineering test platform are successfully applied to the dynamic response analysis of local faults such as pits and end deformation of rolling bearings in roughing mill.The rolling bearing disassembly strategy of strip mill is optimized,the dynamic axial thrust measurement method of strip mill is provided,and the accuracy of local fault type identification is improved.