An inspection device based on multiple Lamb wave electromagnetic acoustic transducers

The accuracy and speed of nondestructive testing can be improved by using multiple Lamb wave electromagnetic acoustic transducers (EMATs) instead of a single one. However, the methods for the arrangement of the multiple transducers have been seldom reported. In this paper, the acoustic field excited by the Lamb wave EMAT is described by a 3-D finite element (FE) model. Based on this acoustic field, the effective detection region is obtained and the arrangement of EMATs can then be achieved. An inspection device with multiple Lamb wave EMATs for aluminum plate detection is developed, which consists of circuits for processing, transmitting and receiving signals via EMATs. LabWindows/CVI is adopted to display the received signals of each transducer. According to the experimental results, a through-hole of Φ2mm and a fillister of 4mm length can be identified, and there is no blind zone between adjacent transducers.