| Hub bearing is an important support for vehicles,which has the characteristics of small contact area and relative stress concentration.Once the hub bearing failure,it will affect the safety and comfort of the vehicle.As an important reason for bearing failure,surface crack has great research value.In this paper,a vehicle rear axle bearing is taken as the research object,its model is 32218.Under different working conditions,finite element simulation is used to investigate the failure mechanism of early cracks.And through the experiment,the crack fault feature is extracted.It is of great significance to study the early fault diagnosis of bearing.Firstly,the contact problem of finite element is introduced,and the mechanical analysis of bearing is carried out.Then according to the measurement parameters of the bearing,the finite element model of the bearing is established under reasonable assumptions,the correctness of the model is determined by finite element calculations.Under the static condition,the stress characteristics of the bearing at the crack and the stress distribution along the crack bearing unit are obtained,so as to deduce the cause of the failure.Based on the explicit dynamics of ABAQUS,the finite element dynamic analysis is carried out.Firstly,the instantaneous stress of the bearing is analyzed.Then,the change of the stress at the crack and the influence of the crack on the acceleration of the bearing are analyzed under the condition that the speed constant load increases and the load constant speed increases in two cases,the reasons for the effect of load and rotational speed on bearing performance are found,which lay the theoretical foundation for the study of crack under test conditions.The intelligent test platform for bearing performance is built,and the data acquisition system is improved.It determines the crack type,test load and speed of the bearing,and the orthogonal test of three factors and three levels is designed and completed.The influence degree of the factors on the bearing performance is determined as follows: bearing speed,crack direction and bearing load.By introducing signal processing method in the time domain,frequency domain and time-frequency domain,and the advantages and disadvantages of these methods,it is found that the wavelet packet analysis method is the most suitable for the experimental analysis,and it is used to obtain the most needed feature information.Though the analysis of vibration and acoustic emission signal by wavelet packet and orthogonal experiment method,It is concluded that the best vibration characteristic frequency band of the crack is 2.73kHz-3.12 kHz,and the best acoustic emission characteristic frequency band of the crack is: 93.78 kHz-109.41 kHz,These frequency bands are related to the occurrence and variation of bearing cracks,and are not affected by other external factors.In this paper,finite element simulation is used to obtain the mechanism of early crack of bearing,which provides a theoretical basis for the study of crack propagation and failure analysis;the characteristic frequency band of bearing crack was obtained by orthogonal test and wavelet packet data processing,it provides the most effective source of data for the next step of data fusion and intelligent identification of bearing failure and has some practical value. |
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