Dynamic Modeling And Fault Feature Analysis Of Rolling Bearings With Damage

Rolling bearings are important support parts widely used in rotating machinery.They are used in a wide range of applications,from mechanical structures in daily life to high-end equipments such as industrial gas turbines and helicopter reducers.Since the birth of the rolling bearing,they have been serialized,normalized and standardized in the development process of the past hundred years.The value of the rolling bearing itself is not large,but in the event of a failure,it may affect the normal operation of the entire equipment,and can cause significant economic losses.During the long service life of rolling bearings,various local faults such as indentation,spalling,wear,pitting,etc.may occur,which may induce abnormal vibration of the system and lead to degradation of equipment performance.According to statistics,in rotating machinery supportted by rolling bearings,nearly about 30%of mechanical failures are caused by failure of rolling bearings.Therefore,the research on the dynamics of rolling bearings and its fault diagnosis has important theoretical and engineering significance.This paper focuses on the dynamic modeling and fault characteristics analysis of rolling bearings with local damage.The main research contents are listed as follows:(1)Taking the cylindrical roller bearing as the research object,based on the contact dynamics theory,the explicit finite element method is used to calculate the vibration response of the inner and outer rings of the bearing with the straight slot local spalling failure.Firstly,a two-dimensional explicit finite element model of healthy bearings is established,and the model is verified from the perspective of rolling bearing kinematics.On this basis,the proposed finite element model with inner ring fault and outer ring fault is established,respectively.The stress state and vibration characteristics of the fault bearing are analyzed.The simulation results are compared with the experimental results to further verify the validity of the model.On the basis of fully verifying the model,the effects of fault parameters,such as spalling width and depth on the vibration characteristics of the bearing,are studied.(2)According to the working state of the bearing under variable speed conditions,the bearing vibration response under certain working conditions is analyzed based on the twodimensional explicit finite element model.Considering the case that the bearing works under time-varying speed which is more difficult to be determined,a vibration signal analysis method for the variable speed fault rolling bearing without tachometer is proposed.Based on the simulation faulty signal under varing speed conditions the analysis is carried out and the fault types are successfully identified.The correctness of the model and the effectiveness of the proposed method are verified by experiments.(3)In order to simulate the uneven spalling of the inner and outer rings of the bearing along the axial direction,a three-dimensional explicit finite element model of rolling bearing is established.The proposed model is verified from the aspects of the kinematics.of the rolling bearing.In addition,the model is also verified by comparing with the contact force between roller and the raceway,and the stress distribution of the loaded roller.The contact stress analysis and vibration response under different lengths of axial spalling and different levels of point spalling were analyzed.The results show that the severe stress concentrations occur at the edge of the fault zone as the roller rolls over the fault zone.(4)The time domain vibration signal is regarded as a graph signal(Graph Signal),and the graph theory is introduced into the vibration analysis of rolling bearing.The original time domain vibration signal is transformed into the eigenvalue domain by the Fourier transform of the graph signal,and the eigenvalue domain statistical index is constructed by emulating the frequency domain statistical index of the vibration signal.These characteristic indexes are used to analyze the simulated signal of the fault rolling bearing,the experimental signal of artificial fault bearing,and the accelerated life test signal.The results show that the characteristic value domain index of the vibration signal based.on graph theory is convenient to be implemented compared with the traditional time domain index.