Feature Analysis And Extraction Of The Loosening Of Bolted Joints With Transverse Vibration

Bolted joint is one of the most widely used forms of connection. However, in the process of using, the long time vibration may cause the loosening of the bolted joints. Studies have shown that the cyclic transverse loading which is perpendicular to the bolt axis is an important factor causing loosening. Based on the achievements of domestic and international, this paper theoretically analyzed the slip of the contact surfaces of bolted joint and the process of loosening under the transverse vibration. Then, setting up a vibration test machine, and using experimental methods to study the influence of the transverse load factors on the loosening characteristics. In addition, for the purpose of guiding the application, it extracted the loosening feature of bolted joints by using signal processing technology based on the theoretical and experimental researches. The main researches of this paper are as follows:Firstly, introduced the research status of the influence of the transverse load on the loosening of bolted joints, and the application of the signal processing technology in the fault feature extraction and recognition. Then, based on the basic theory of the loosening of the bolted joint under transverse vibration loose, researched the slip of contact surface during loosening, analyzed the influencing factors of the slip, and expounded the processing of the slip of the bolted joint contact surface under the transverse vibration.Secondly, according to the national standards and using requirements, a transverse vibration testing machine used for bolted joints loosening test was developed. Based on this device, the following researches have been done: the effects of transverse vibration on bolt connection under different lubrication condition, analysis of the stage characteristics of the bolted joints loosening curve, numerical simulation of characteristic curves, analysis of the amplitude characteristics of the connected parts in the process of bolted joints loosening, analysis of the relationship between the transverse load and bolted joints loosening. The above experimental research has further verified the theoretical analysis.Finally, in order to explore the application of the study on the loosening characteristics of bolted joint, this paper built a vibration signal acquisition system for collecting the vibration signals of the connected parts of bolted joint, and processed the signals by using the fast Fourier transform and wavelet analysis technology respectively. The frequency response characteristics of the bolt are obtained in the frequency domain. And in the time-frequency domain, the energy distribution characteristics are obtained by wavelet decomposition. As a result, this paper extracted the loosening feature of bolted joint under transverse vibration.