Electromagnetic Acoustic Transducer for Generation and Detection of Guided Waves

This paper presents a study of the use of low frequency electromagnetic acoustic transducers (EMATs) to generate and detect the single mode of Lamb waves in steel plates and pipes of different thickness. Using a small EMAT of the Lorentz force type, the desired single mode of Lamb waves are generated and detected by tuning the center frequency of narrowband signals; the center frequency of the waves is below 1 MHz. The experimental work of mode excitation is performed on steel plates and pipes of different thickness, and the results indicate that this EMAT configuration for the excitation of the single mode of Lamb waves is valid. In order to evaluate the detection ability of this EMAT system, experiments are performed in the circumferential direction of a steel pipe sample containing a defect. The results show that this EMAT system realizes an effective detection of defects in reflection experiments.