Application Research Of Acoustic Emission Technology In Damage Detection Of High Speed Train Gearbox Shell

As a key transmission component of high-speed trains,the gearbox must be overhauled once a failure occurs,and improper maintenance will likely lead to serious traffic safety accidents.As the external structure protecting the gearbox shell of high-speed trains,the gearbox shell is a key component to ensure the safe operation of the gearbox and the whole car.Traditional damage detection methods are difficult to detect under the premise of guaranteeing the gearbox shell is not damaged or the normal operation of the whole car,while acoustic emission detection technology,as a non-destructive testing technology,can both ensure real-time monitoring of the gearbox shell and damage location without damage to the gearbox shell.However,there are few studies on the damage detection of the gearbox shell by acoustic emission technology,and there is a lack of theoretical studies on gearbox shell.In this paper,we take high-speed train gearbox shell as the object of research,mainly including the derivation of reflection and transmission coefficients in multi-layer media,analyzing the influence of coating and rib plate on the acoustic emission wave propagation characteristics of high-speed train gearbox shell structure using ABAQUS finite element software,and conducting acoustic emission source localization research on the gearbox shell with coating and rib plate structure using lead break experiment,and using wavelet The sound source localization of the gearbox shell with ribbed plate structure is optimized by using wavelet transformation.In this paper,the following aspects are studied:(1)By establishing a theoretical model for the tilted incidence of acoustic emission waves into the multilayer structure,the matrix equations of displacement reflection coefficient and displacement transmission coefficient are solved,and the relationship between displacement reflection coefficient and displacement transmission coefficient with the incident wave and medium parameters is analyzed.The relational equations of acoustic pressure reflection coefficient and acoustic pressure transmission coefficient when the acoustic emission wave is incident vertically on the double-layer medium and the three-layer medium are derived,and the relevant parameters of aluminum alloy plate,coating and sensor ceramic layer are substituted to solve and analyze the acoustic pressure transmission coefficient under the double-layer medium and the three-layer medium.(2)Using ABAQUS finite element analysis software,a model of the box component of a high speed railway the gearbox with coating was established,and the generation and propagation process of acoustic emission waves in the double-layer structure of aluminum alloy plate and coating were analyzed by applying variable excitation force,and it was found that the X-directional velocity and acceleration in the aluminum alloy plate can characterize the propagation history of acoustic emission waves in the aluminum alloy plate with coating.The X-directional velocities were used to calculate the wave velocities of acoustic emission waves in uncoated aluminum alloy plates with theoretical wave velocities,and the effects of coating thickness,density,Poisson’s ratio and elastic modulus on the propagation characteristics of acoustic emission waves were analyzed separately.(3)In order to analyze the influence of the coated the gearbox shell on the acoustic emission wave velocity and positioning,the experimental analysis of the acoustic emission wave velocity under the threshold setting of the time-difference positioning method and the amount of coupling agent used were conducted through the lead break experiment,and the most suitable experimental conditions for the acoustic emission wave velocity measurement and positioning experiments were obtained,and the influence of the coating thickness on the acoustic emission wave velocity was verified through the experiments,and the influence of the coating thickness on the acoustic emission wave velocity was studied by wavelet analysis.The effect of coating thickness on acoustic emission wave velocity was verified and the effect of coating thickness on acoustic emission wave frequency band was investigated by wavelet analysis.The experiments of acoustic emission source positioning for gearbox shell with different coating thicknesses were conducted,and it was learned that the smaller the coating thickness,the smaller the positioning error would be.(4)In order to study the influence of ribs on the acoustic emission wave propagation characteristics on the surface of the gearbox shell,the ABAQUS finite element software was used to simulate the acoustic emission wave propagation characteristics of different shapes and numbers of ribs,and the influence of different shapes and numbers of ribs on the positioning accuracy was obtained through simulation.The experiment of lead breaking is used to locate the sound source of the gearbox shell with different number of ribs,and the comparison of experimental positioning and simulation results shows that the more the number of ribs,the worse the positioning accuracy.Finally,the band-pass filtering of the lead-break signal is performed by using wavelet transform,and the positioning results of the gearbox shell with rib structure are optimized by the obtained modal waves.