부산대학교 도서관

Phased array ultrasonic total focusing method (TFM) imaging has attracted much attention due to its high detection image resolution and large dynamic range. However, due to the small emission energy of its single element, the echo signal is weak and susceptible to noise interference, resulting in a relatively low signal-to-noise ratio (SNR). Especially when detecting high sound attenuation carbon fiber reinforced polymer (CFRP) composites, the signal amplitude can decrease with depth to a level lower than the electronic noise introduced by the signal acquisition system. To solve this problem, a new imaging algorithm was proposed that combines the Golay code excitation using linear frequency modulation (LFM) signal as the carrier with the TFM algorithm (LFM-Golay TFM). Meanwhile, in order to further overcome the disadvantage of the LFM-Golay code encoding excitation method requiring two excitations, an AB code encoding excitation conversion factor was introduced, two sets of echo data were obtained through processing single excitation, and TFM imaging based on LFM-Golay code single excitation (IMP-LFM-Golay TFM) is realized. Simulation and experimental studies were conducted to compare the TFM imaging performance of single-pulse excitation (Pulse TFM), Barker coding excitation (Barker TFM), LFM excitation (LFM TFM), and improved LFM-Golay coding excitation. The results show that IMP-LFM-Golay TFM has the best SNR, axial resolution, and depth resolution.