Study On Acoustic Emission Signal Propagation Characteristics Of Rolling Bearing

As an important part of rotating machinery,rolling bearing has been widely used in various fields of industrial production.However,rolling bearing is also a mechanical part prone to failure.Bearing in the early stage of a minor fault will affect the operation of the entire mechanical equipment.thereby affecting the production efficiency and even threat to production safety,bringing huge economic property losses.So it is very important to perform the fault diagnosis of rolling bearing running state.As a nondestructive testing method,acoustic emission technique is used to detect the acoustic emission signal which is generated by the displacement of fault in crystal and elastic wave.The high frequency elastic wave signal makes the acoustic emission technology more timely to monitor the fault signal in damage small and intervent it than other nondestructive testing technology,which has an important significance to ensure the reliability of the equipment and the safety of industrial production.This thesis mainly studied the propagation characteristics of acoustic emission signals,and reviewed the research progress of acoustic emission testing of rolling bearings and acoustic emission wave propagation characteristics at home and abroad.It also introduced the generation,propagation form and attenuation mechanism of acoustic emission waves.The basic idea of finite element theory was expounded and the finite element simulation was applied to study the propagation characteristics of acoustic emission signals.The simulation experiment was carried out by COMSOL,a large finite element multi-physical field disaster simulation software.The acoustic emission wave belonged to elastic wave,and the propagation characteristics of elastic wave in solid could be explained by solid mechanics theory.Firstly,the characteristics of acoustic emission waves were understood by simulating their propagation in simple structures.By studying the propagation of elastic wave in three dimensional plate structure,the attenuation characteristics of sound wave were revealed in time domain and frequency domain.The reflection and transmission characteristics of acoustic emission waves at the interface of different media were studied by establishing a two-dimensional aluminum-steel interface.Secondly,the propagation characteristics of acoustic emission wave in the rolling bearing were studied.The two-dimensional bearing model was built for wave simulation by detailing the grid.The fault triggered acoustic emission wave was simulated.The displacement cloud map was drawn,and the propagation path of acoustic emission wave in the bearing and the interaction with various structures in the bearing were intuitively understood.Based on the actual size of bearing parameters for the simulation of the three-dimensional bearing,the acoustic emission signal propagation characteristics were studied from three aspects.Firstly,the fault source signals of three different fault positions were simulated.The response signals of sensors placed in different positions were compared.The differences between different types of fault signal were summarized from two aspects of time domain and frequency domain.The simulation results were validated by test.The types of AE sources were further changed by changing the crack length and direction,and simulating pitting AE sources.The differences in response signals were analyzed.Finally,the propagation characteristics of acoustic emission signals in rolling bearing structures were further revealed by the acoustic emission signals detected at a distance on the bearing bottom plate.