A high-sensitivity and long-distance structural health monitoring system based on bidirectional SH wave phased array

Qiang Huan; Mingtong Chen; Faxin Li

doi:10.1016/j.ultras.2020.106190

A high-sensitivity and long-distance structural health monitoring system based on bidirectional SH wave phased array

Ultrasonics. 2020 Dec:108:106190. doi: 10.1016/j.ultras.2020.106190. Epub 2020 Jun 1.

Authors

Qiang Huan¹, Mingtong Chen¹, Faxin Li²

Affiliations

¹ LTCS and College of Engineering, Peking University, Beijing 100871, China; Center for Applied Physics and Technology, Peking University, Beijing, China.
² LTCS and College of Engineering, Peking University, Beijing 100871, China; Center for Applied Physics and Technology, Peking University, Beijing, China; Beijing Key Laboratory of Magnetoelectric Materials and Devices, Peking University, Beijing, China. Electronic address: lifaxin@pku.edu.cn.

PMID: 32526528
DOI: 10.1016/j.ultras.2020.106190

Abstract

When estimating a structural health monitoring (SHM) system, its defect sensitivity and area/distance coverage are most important factors. For commonly used guided wave sparse array system, it usually requires a reference state as the baseline which is not available in many cases. In comparison, phased array technique typically does not need the baseline in simple structures and it had been successfully used in nondestructive testing (NDT). However, currently developed phased array systems employed omni-directional transducers routinely, where the wave energy is distributed equally along all directions thus it is not favorable for long-distance detection. In this work, bidirectional piezoelectric transducers were used to form a linear phased array system, which can generate/receive shear horizontal (SH) wave with high energy concentration. Firstly, the configuration of the employed transducer composed by antiparallel d₁₅ piezoelectric strips (APS) was presented. Then the total focusing method (TFM) employed for defect detection was introduced. After validating the radiation pattern of SH wave generated by the APS, the properties of beam steering for the proposed phased array was investigated. Finally, experiments were carried out to validate its performance in detection of various defects. Results indicated that even for a 1 mm through-thickness hole 700 mm away, the proposed phased array system can still detect it accurately, which is much better than previous SHM systems. Dual defects including a crack and a hole can also be clearly detected without baseline. The high-sensitivity of the proposed system was attributed to the employed bidirectional transducer which can generate non-dispersive SH₀ wave with high energy concentration. This proposed SH wave phased array system will provide a high-performance SHM method for plate-like structures.

Keywords: Guided wave; Phased array; Piezoelectric transducer; Shear horizontal wave; Structural health monitoring.