Research On Acoustic Emission Source Localization Method Of Plate-like Metallic Structures

Thin plate or plate-like metal structural parts are widely used in various industries such as chemical industry production,aerospace and marine automotive industries.With the improvement of industrialization in China,automation level,and high-level and high-tech requirements for industrial production,the demand for metal materials in various industries in China has increased year by year.During the process of forming and using the metal plate structure,defects in the structural parts are generated,which may pose a threat to the safety of the parts,thereby causing fatigue damage.With the support of the National Natural Science Foundation of China,this paper took the metal plate structure as the research object,and mainly did the following research work on acoustic emission signal velocity,separation of specific frequency signals and positioning of acoustic emission sources:(1)The multi-modality and dispersion phenomena of the acoustic emission signal in the process of propagation were analyzed.The separation of different modes of acoustic emission signals and the extraction of specific frequency components were studied.The Morlet wavelet was used to separate the lowest order symmetric mode S0 and the lowest order antisymmetric mode A0 existing in the acoustic emission signal,and the characteristics of their respective center frequencies were extracted.The on-site wave velocity measuring method was proposed.This method reduced the error in the positioning process while ensuring reliable wave velocity.(2)An acoustic emission source localization method based on time-reversed focusing was proposed,and the acoustic emission source was presented in a two-dimensional damage fluctuation image.The acoustic emission source localization experimental platform of metal thin plate parts was built.The acoustic emission source localization algorithm of signal time difference operation was studied.The fluctuation image of the whole monitoring area was established at the focus time,and the imaging result was thresholded to eliminate the pseudo peak pair positioning.The effect of the results,refined the resolution during imaging,and improved positioning and display accuracy.(3)The method of locating the acoustic emission source of the curved surface structure of the pipeline wall was studied and propoed.By studying the propagation process and mechanism of the acoustic emission signal on the curved surface structure,the acoustic emission source of the pressure pipeline leakage was proposed based on the positioning of the planar metal thin plate.The positioning imaging algorithm was used to construct the source positioning model of the cylindrical shell structure,which realized the positioning imaging of the acoustic emission source on the curved metal structure.The research shows that the positioning method of the acoustic emission source proposed in this paper is experimentally verified on the planar metal plate structure and the pressure pipe respectively,which can locate and display the position of the acoustic emission source well,and provide the reference of location of the damage source for large structural parts.