Research On Failure Mechanism Of Bearing Raceway Defect And Rotor Unbalance Faults Coupling

Rolling bearing-rotor system(RBRS)is a key component of the rotating machinery.Its performance directly affects the stability of the machine.Once the RBRS breaks down,it may lead to the failure of the machine resulting in serious losses.Therefore,the dynamic characteristic simulation analysis of the RBRS can be used to study the fault characteristics and mechanism of the RBRS under various fault conditions.It is great significance to ensure the normal operation of rolling bearing-rotor system and to diagnose the faults of rotating machinery.This paper presents a dynamic contact finite element simulation method for explicit dynamic contact surface refinement of rolling bearing-rotor system.Based on the method,LS-DYNA is used to study the fault characteristics and mechanism in two conditions including the outer raceway defect and the coupling fault between the outer raceway defect and the rotor imbalance.It mainly includes three parts:(1)Based on the existing theory of the rolling bearing motion and mechanical relationship,the elastic deformation,contact deformation and friction relationship between contact interfaces of the system all parts are considered.Based on the augmented Lagrange method of virtual displacement principle and the explicit center difference method,a dynamic contact finite element simulation method of explicit dynamic contact surface refinement for studying the dynamic characteristics of rolling bearing-rotor system is proposed.The validity of the method is verified by comparing the simulation results of the motion characteristics and the theoretical results.The results show that the model not only improves the calculation efficiency of the model,but also reduces the instability of the movement and dynamic contact during the dynamic contact process of rolling bearing components.(2)The fault characteristics and mechanism of the rolling bearings outer raceway defects are studied and verified by experiments.The rolling bearing-rotor system model with the defects in the outer raceway of rolling bearing is taken as the research object.By analyzing the motion and dynamic contact characteristics of each component,the fault characteristics and mechanism are studied.Then,the dynamic characteristics variation law of each component in the condition of different defect sizes in rolling bearing outer raceway are compared and analyzed.Study on the variation law of system fault characteristics and the reason of difference.Finally,a fault simulation experiment is designed.The validity of the simulation conclusion is verified by comparing the experimental data with the simulation data.The results show that the reason of the fault impacts is the impact between the rolling elements and the edge of the defect,and the"beating" of the rolling element between the inner and outer raceways.When the working condition of rolling bearing is constant,the magnitude of the fault impact is directly proportional to the height of the rolling element in the defect at which the rolling element passes through the defect instantly.The fault impact amplitude will increase with the increase of defect size when there is no "double impacts" phenomenon in the time domain waveform of vibration acceleration.When there is "double impacts" phenomenon,the impact amplitude will decrease correspondingly.And there is no obvious correlation with the defect size.(3)Its explains that the fault characteristics mechanism of the coupling faults between the outer raceway defect of the rolling bearing and the rotor unbalance.Analyze the changes law of the motion characteristics and the system stress in the faults coupling state and the single action of the two faults.The system fault characteristics in faults coupling state are studied.In the condition of faults coupling,the motion trajectories,element stress and contact force of the rolling bearing are extracted.And the coupling faults mechanism is studied.Then,the simulation results are compared with the experimental results to verify the effectiveness of the simulation results.Finally,the simulation results are used to diagnose the real fault cases,which verifies that the research results of this paper have auxiliary or supporting role in fault diagnosis.The results show that the impact amplitude of outer raceway defect is modulated by rotation frequency when the outer raceway defect of rolling bearing and rotor unbalance faults exist at the same time.The reason of the fault impacts is the "beating" of the rolling element between the inner and outer raceways.The impact amplitude increases with the increase of the inner raceway loading force of the rolling element.