Research On The Relationship Between The Fault Shape And Vibration Characteristics Of Rolling Bearings

Rolling bearings are a kind of precision basic components.According to statistics,nearly one-third of the faults of rotating equipment are caused by bearing faults.It is necessary to carry out real-time condition monitoring of bearings to find and identify early faults in time,so as to prevent further deterioration of bearings leading to catastrophic faults of rotors and even the whole equipment.The prerequisite for effective early fault diagnosis of rolling bearings is to accurately grasp the fault mechanism and vibration characteristics under fault excitation.Dynamic modeling of local faults of rolling bearings is a common method to study the mechanism of bearing faults.There is a complicated contact process when the rolling elements pass through the fault area,so the accuracy of the local fault excitation function directly affects the accuracy of the entire dynamic model.Because the local fault excitation is related to the bearing fault size,bearing speed and other conditions,the existing single simplified excitation function cannot accurately reflect the actual contact between the rolling elements and the fault.Taking the bearing outer ring fault as the research object,this paper proposes the time-varying excitation function of the rolling element passing through the fault area,establishes the dynamic model of the rolling bearing outer ring local fault,and studies the influence of the fault shape on its vibration characteristics.The main research contents are as follows:(1)The change of contact clearance of rolling element passing through the fault area is analyzed in detail,and a time-varying displacement excitation function related to the relative position of the rolling elements is established.According to the impact force generated by the contact between the rolling elements and the fault edge,an instantaneous impact force excitation function considering the fault size and bearing speed is proposed.The effects of fault size and bearing speed are introduced into the impact force function.The contact process between the rolling element and the fault area can be described more accurately.Based on the above excitation function,the dynamic model of rolling bearing local fault is established.This model can more accurately simulate the actual impact when the rolling elements pass through the raceway fault zone.Compared with the traditional model,the bearing model established in this paper changes more obviously with the speed and can more effectively simulate the vibration characteristics of the actual rolling bearing.(2)In order to carry out the state monitoring of bearings based on vibration characteristics,the bearing dynamic model considering local fault damage degree is established based on time-varying excitation function,and the bearing fault simulation experiment is carried out.The simulation and experimental signal characteristics are compared and analyzed to verify the effectiveness of the model.Based on the dynamic model,the characteristic parameters of bearing vibration response under different damage degrees are solved.The influence of fault size on one-dimensional and multi-dimensional vibration characteristic parameters in time domain and frequency domain is analyzed.The sensitivity of different fault characteristic parameters in different fault stages is different.Therefore,the sensitivity of each characteristic parameter to fault damage degree is analyzed in this paper.When monitoring and diagnosing bearing faults,it is necessary to use the vibration characteristic parameters with consideration of sensitivity and stability.(3)The number of contact points and the change of contact position of rolling elements have certain influence on vibration response when different roller path faults occur.Therefore,in order to explore the influence of the local fault form of rolling bearing on vibration characteristics,a dynamic model of rolling bearing is established which takes into account the characteristics of local fault profile.According to the excitation characteristics of different fault profiles,the time-varying displacement excitation function and instantaneous impact force function are proposed firstly.Considering that the local contact form of spherical rolling elements is sensitive to the change of fault profile,a dynamic model of deep groove ball bearing considering local fault profile is established and verified by experimental data.The dynamic model of bearing with different fault forms is solved to study the change of vibration characteristic parameters with fault profile.