Application of pulse compression technique in metal materials cracks detection with LF-EMATs. Issue 1 (2nd January 2023)

• Record Type: Journal Article
• Authors: He, Min; Shi, Wenze; Lu, Chao; Chen, Yao; Zhao, Liping; Dong, Dexiu; Zeng, Guangdeng
• Is Part Of: Nondestructive testing and evaluation. Volume 38:Issue 1(2023)
• Page Start: 45
• Page End: 66
• Publication Date: 2023-01-02
• Subjects: Line-Focusing EMAT -- Barker code -- pulse compression technique -- signal-to-noise ratio -- spatial resolution; Non-destructive testing -- Periodicals; 620.112705
• DOI: 10.1080/10589759.2022.2066664
• Languages: English
• ISSNs: 1058-9759

Abstract

ABSTRACT: To address the problem of low signal-to-noise ratio (SNR) and poor spatial resolution of cracks detection of the angled SV wave electromagnetic acoustic transducer (EMAT), pulse compression technique (PCT) and line-focusing technique are introduced into the angled SV wave EMAT. A finite element (FE) model of the line-focusing (LF) EMAT detection process based on the Barker code excitation was established, and the effects of the design parameters of magnet and meander-line coil (MLC) on the main lobe amplitude and width of the defect echo after pulse compression were analysed. The optimal combination of LF-EMAT design parameters and excitation parameters was obtained, and it was compared with the traditional angled SV wave EMAT and the tone-burst excitation method by experimental measurements. The results shows that compared with angled SV wave EMAT with tone-burst excitation, LF-EMAT can improve the SNR by 14.9 dB with no synchronous average and be processed by PCT. The SNR from LF-EMAT with PCT is10 dB at 1.5 mm lift-off, while the SNR of the angled SV wave EMAT with tone-burst excitation is less than 0 dB at 1 mm lift-off. When the Barker code PCT is applied to the LF-EMAT detection, we can achieve the purpose of increasing EMAT lift-off and reducing the synchronous averages to meet the demand of online, rapid, and high-temperature detection.