A New Type of SH-Guided Wave EMAT based on Barker Code Pulse Compression Technology with Tone-Burst Excitation

When Barker code pulse compression technology is applied in a traditional SH-guided wave Electromagnetic Acoustic Transducer (EMAT), the duration of the Barker code excitation signal is so long that the pulse power generator parameters, such as the maximum duty cycle and maximum pulse width may restrict detection blind distance increases and the duration. Thus, we propose a new multi-array SH-guided wave EMAT based on Barker code pulse compression technology with tone-burst excitation. We establish a finite element model of a multi-array SH-guided wave EMAT detection process based on Baker code pulse compression technology with tone-burst excitation. The effects of Barker sequence length, permanent magnet pair, cycle number of sinusoidal subpulse, array element spacing, and other factors on the peak side-lobe level (PSL) and main lobe width after pulse compression are analyzed and verified by experiments. The results show that when the tone-burst signal is used to excite the new multi-array EMAT, the signal-to-noise ratio (SNR) of the 5-array EMAT and 7-array EMAT are 11.95 dB and 13.05 dB than the traditional 5-bit Baker code EMAT and 7-bit Barker code EMAT, respectively. Compared with the traditional 5-bit and 7-bit conventional Barker code EMATs, the main bang durations of the 5-array EMAT and 7-array EMATs are reduced by 67% and 72%. The optimum EMAT parameters obtained after optimization are a 7-bit barker code sequence, a single array element composed of 4 pairs of permanent magnets and 8 excitation cycles. The optimized EMAT can detect cracks with a length of 10 mm, a width of 1 mm, and a depth of 1 mm, and the defect wave SNR is 18.59 dB.