Research On Key Technologies Of Electromagnetically Excited Acoustic Emission

Electromagnetically Acoustic Emission(EMAE)technology is a new nondestructive testing technology.Due to it' s simple detection method and has the important application value,EMAE has a variety of application scenarios.In this paper we design a new electromagnetic loading experiment system,to achieve a more stable and reliable electromagnetic loading scheme for generate acoustic emission signals.Due to the nonlinear and non-stationary characteristics of acoustic emission signals,the time-frequency analysis is used to analyze the signals.The main research work is as follows:(1)The key step of electromagnetic loading acoustic emission signal is the electromagnetic loading mehod in the defective metal sample.Therefore,the stability of electromagnetic loading is particularly important.In this paper,a stable and efficient electromagnetic loading experimental platform is established.It's use CH130 electromagnet,MAN-10030 current source and SAEU2S acoustic emission system as the core electromagnetic loading device.Organic combination,good effect.The non-contact Electromagnetic loading of different materials specimens with or without defects.(2)In this paper,introduced the time-frequency analysis theory.According to the acoustic emission signal,analyzed the time-frequency characteristics of the signal by using the time-frequency analysis method.Comprehensive comparative study WVD?PWVD?SPWVD?WT time-frequency analysis technology.From many angle discussed the advantages and disadvantages of different time-frequency analysis techniques,such as time-frequency aggregation,cross term interference,time-frequency resolution,initial point,acoustic emission energy release level.(3)Time frequency analysis technology to further explore the use of Hilbert Huang Transform,This method starting from the electromagnetic acoustic emission signal,it is not necessary to select the window function and the basis function any prior condition.Moreover,it has high time-frequency aggregation,and has good time-frequency resolution and has excellent performance of local time-frequency characteristics.The signal can be decomposed into different IMF,reaction stage of electromagnetic acoustic emission signals has their frequency characteristics,amplitude and energe.(4)Through the algorithm of empirical mode decomposition,the complex nonlinear and non stationary signal to extract the singular point,the energy release time,coda duration of key physical variables.The important features of the original signal are described by the envelope spectrum and instantaneous frequency.