Ultrasonic Phased Array Post-Processing Imaging Technique Based On Coded Excitation

Ultrasonic phased array Total Focusing Method(TFM)attracts much interest because of high image resolution and large dynamic range,and has broad development prospects in the field of industrial nondestructive testing.However,the data acquisition method relied on by the TFM imaging algorithm is based on single-element independent excitation,which makes the echo data susceptible to attenuation and leads to lower signal-to-noise ratio(SNR)and imaging quality,making TFM in high-acoustic attenuation,coarse-grained material components and The application of actual non-destructive testing in noisy environments is limited.In this paper,the TFM SNR is improved by introducing coded excitation technology,and the Golay-coded excitation improvement scheme is proposed,which makes TFM more suitable for practical engineering applications of non-destructive testing.The main research work is as follows:According to the image reconstruction principle of TFM algorithm,the imaging program is programmed and improved based on MATLAB,and the reconstruction of the detection target image is realized in both simulation and experiment,and the imaging accuracy is about half wavelength.By analyzing different kinds of coding excitation techniques,the Golay code complementary sequence is selected to improve the SNR of TFM imaging,and the TFM based on Golay-coded excitation technology is realized.The feasibility verification is carried out in two aspects of simulation and experiment.In order to avoid the disadvantage of Golay-coded excitation,this paper proposes an modified Golay-coded excitation,proposes TFM based on modified Golay-coded excitation,and compares it with traditional Golay-coded excitation and single-pulse TFM.According to the result of simulations and experiments,TFM using modified Golay-coded excitation in phased array gives approximately the same performance as TFM using traditional Golay-coded excitation.,and can avoid the negative decoding performance due to the relative change of scanning positions in traditional double-excitation Golay-coded excitation.