Lower frequency ultrasonic guided wave (20 kHz–200 kHz) has obvious advantages in large area plate monitoring. It enables longer propagation distances because of low attenuation and simple modes. The present study utilized a Galfenol Rod Ultrasonic Transducer (GRUT) excite low-frequency ultrasonic guided waves in plate inspection. It was verified by finite element simulation and experiment that GRUT can excite S₀ mode Lamb wave, A₀ mode Lamb wave and SH₀ wave. A defects detection method based on A₀ mode and S₀ mode Lamb wave is proposed that “A₀ mode Lamb wave is used for defect determination by its amplitude variation in time domain, and utilized S₀ mode Lamb wave to locate the defect”. In this paper, utilize GRUT to detect a via hole with a radius of 2 cm, the experimental results show that the proposed method is convenient and fast with less signal processing, and the experimental error is 10.22 %.

低频超声导波（20 kHz–200 kHz）在大面积板监测中具有明显的优势。由于低衰减和简单模式，它可以实现更长的传播距离。本研究利用Galfenol棒式超声换能器（GRUT）在板检测中激发低频超声导波。通过有限元模拟和实验证明，GRUT可以激发S ₀型兰姆波，A ₀型兰姆波和SH ₀波。提出了一种基于A ₀模式和S ₀模式兰姆波的缺陷检测方法，即“通过使用A ₀模式兰姆波在时域中的幅度变化来确定缺陷，并利用S ₀模式兰姆波定位缺陷”。本文利用GRUT技术对半径为2 cm的通孔进行检测，实验结果表明，该方法简便，快速，信号处理量少，实验误差为10.22％。