Analysis Of Defect Mechanism And Vibration Characteristics Of The Cylindrical Rolling Bearing

The rolling bearing is an important basic component in modern machinery and equipment,and operating state of it directly affects the accuracy and life of mechanical system.When there is a local defect in the rolling bearing,the contact between the component and the fault will destroy the motion stability of the rolling element and cause an impact pulse directly related to the degree of fault inside the bearing.Therefore,in order to accurately predict and identify early defect of bearing,it is particularly important to improve the understanding of the mechanism of bearing failure vibration and its transmission characteristics.However,due to the diversity of fault locations and morphologies and the fact that the bearing is often operating under complex variable conditions,and the contact relationship within the bearing is a complex nonlinear problem,the dynamic modeling of the rolling bearing and the acquisition of internal dynamic characteristics are difficulty.Aiming at the problem of the defect mechanism and vibration characteristics of the cylindrical roller bearing,the establishment and verification of the explicit dynamic finite element model of the rolling bearing,the analysis of the contact characteristics and vibration response during the fault evolution process,the analysis of motion characteristics and time-varying displacement excitation modeling of the rolling element passing through the defect,the vibration transmission characteristics of the bearing-housing system and the analysis of measurement points were studied.The main research contents are as follows:(1)In view of the problem that the vibration change mechanism during the fault evolution process of the rolling bearing has not been clarified,which restricts the accuracy of fault diagnosis,a nonlinear explicit dynamic finite element model of rolling bearing with defect was established.The three most representative types in the fault evolution process were selected,and the typical faults that can reflect all five contact relationships were analyzed.The displacement excitations caused by the fault evolution process were obtained,the change laws of the contact force between the rolling element and the races during the entire fault evolution process were revealed,and the relationship between the contact force and vibration and the mechanism of vibration during the fault evolution process were explained,which can provide a theoretical basis for predicting the remaining life and fault diagnosis of the rolling bearing based on the dynamic characteristics.(2)In view of the problem that the current bearing defect displacement excitation is generally described by a single function,which cannot accurately reflect the fault form.The contact deformation of the rolling element and the races was considered,the displacement androtation speed of the rolling element during the defect and its variation with operating conditions were analyzed.The displacement excitation which can accurately reflect the fault form was proposed,which can provide a reference basis for the dynamic modeling of the partially defective rolling bearing.(3)In view of the problem that the sensor installation position is unfounded due to the vibration transmission characteristics of the bearing-housing system are not yet understood,an explicit dynamic model of an elastic interface rolling bearing-housing system based on the interference fit was established,which overcame the shortcomings of the existing models that cannot accurately describe the difference of vibrations between the bearing outer race and the housing.Based on the analysis of the difference between the vibration signal obtained from the defect point and the test points on the bearing surface,the transmission mechanism of the defect excitation and the mechanism of the structural vibration of the bearing were explained.The change law of defect excitation through interface and the influence of load and speed on the signal of test point were summarized,which can provide a theoretical basis for the arrangement of sensors and improvement of fault diagnosis accuracy under different operating conditions.