Research On Propagation Characteristics Of Acoustic Emission Signal At Aero-engine Components And Coupling Interface

As the components of aero-engine are complex and diverse,the phenomena such as reflection,transmission and diffraction will appear at the components and their interfaces when acoustic emission technology is used for fault detection,which will change the fault signal waveform and other features.It is necessary to study the changes of signal characteristics during the propagation process for increasing the reliability of the fault detection.In view of this,this article does some researches about the rule of signal that propagating at the interface of foundation components in aero-engine,mainly from the following aspects:(1)Simulation research about the rules of acoustic emission signals that propagate in various shapes of structures and their contact interfaces.Establish square,rectangle,round and round annular plate structure respectively,and analyze the influence of interface shape on the signal through waveform,time-frequency domain and dispersion curve.The result show that similar structure shape in the signal propagation characteristics is also similar,and when the interface shape similar to the wave-front the acquired signal attenuation produced by the spread is relatively small,it is also found that the signal in the transmission process instead of scattering area is closely associated with the degree of attenuation.(2)Simulation study on the influence of interface morphology on the propagation characteristics of acoustic emission signals.In order to approximate the characterization of the actual work piece surface topography,this paper set up different specifications and different shapes of micro convex body structure at the interface between component coupling respectively,and then analyze acquired signals through waveform,time-frequency domain and parameter method to observe the signal in the interface convex body and the diffraction effects caused by the contact position,The results show that the larger the gap between the interface specification of the convex body and the wavelength,the easier the signal is to be diffracted.By comparing the structure of the strip convex body and the square convex body,the diffraction effect of the square coconvex body is slightly stronger than the strip convex body under the same contact area structure.(3)Experimental research on the propagation characteristics of acoustic emission signals of components and their coupling interfaces.The single-plate structure and its dual-plate coupling connection structure were established respectively to verify the above simulation research;And then the characteristic coefficients related to energy and amplitude were constructed to characterize the attenuation change at the interface and the signal frequency.Through experimental research,it is verified that the presence of an appropriate amount of lubricating oil in the bearing structure will increase the transmission ability of the signal.