| Friction Stir Welding(FSW)is an emerging solid-phase welding technology.The high temperature generated by mechanical stirring makes the metal in the welding area plastically deform to complete the welding,which avoids the melting and crystallization of the metal during the welding process.So it can better meet the weldability requirements of aluminum alloys.Acoustic emission technology detects whether there is a problem in the welding process by detecting the acoustic emission signal generated by the plastic deformation inside the material,and evaluates the stability of the welding process,thereby improving production efficiency and saving production costs.In order to improve the performance and welding efficiency of friction stir welding joints,and to further control the welding process and welding process more accurately,it is of great significance to apply acoustic emission detection technology to the detection and evaluation of friction stir welding quality.In this paper,the friction stir butt welding experiment of 6061-T6 aluminum alloy plate is carried out,and different defect morphologies were prefabricated by adjusting different welding parameters,including flash defects and tunnel defects,and acoustic emission signal acquisition is carried out during the whole welding process.First of all,when analyzing the welding signal using the time domain analysis method and the frequency domain analysis method,it is found that the flash or groove defect will lead to a certain increase in the signal amplitude of the welding signal in the time domain and frequency domain.Then,by using wavelet analysis,wavelet packet decomposition,short-time Fourier transform and other combined timefrequency domain analysis methods to further analyze the effect of welding defects on the signal amplitude changes in each frequency band of the acoustic emission signal during the whole welding process,as well as on the energy of each frequency band,it found that there are certain differences in the identification effect of different analysis methods for different weld defects.After obtaining certain signal characteristics through this kind of signal analysis method,the marginal spectrum of the welding signal is obtained by the HHT transformation.And by the marginal spectrum,three main characteristic frequencies for evaluating the welding quality of the weld can be obtained,and it is found that in different welding shapes,there is a certain amplitude variation relationship among the three main characteristic frequencies. |
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