EMAT generation and laser detection of single lamb wave modes

Abstract

Non-contact and couplant-free nondestructive testing methods are desired in certain situations. There are several designs of non-contact transducers that have been developed. Electromagnetic acoustic transducers (EMATs) and laser-based ultrasonic sensors are well known non-contact transducers. EMATs are typically of limited bandwidth. EMATs and LBU both have lower sensitivity than conventional piezoelectric transducers, and are therefore typically useful in situations where there is sufficient signal strength, but where non-contact is necessary (EMATs and LBU), or where high spatial resolution (LBU) is needed. Thus, ultrasonic NDE schemes with various configurations have been utilized; these configurations include using EMATs as both generator and receiver [1–2], using lasers as both generator and receiver[3–4], and using a laser as source and EMATs as receiver [5].