A portable inspection instrument based on electromagnetic acoustic transducers

Aluminum plate plays an important role in industrial manufacture. Recently, most of the flaw detection instruments are either too big or depending on couplant. In order to implement non-contact detection and make it more convenient for detecting thick aluminum plates, a portable inspection instrument is developed based on electromagnetic acoustic transducers (EMATs). A spiral coil is designed for improving the inspection ability. The numerical model of the EMAT is established for both electromagnetic and acoustic field analysis by finite element method. According to the acoustic field distribution, the EMAT is suitable for detecting small defects in thick aluminum plates. The accumulative average method and the cross-correlation algorithm are proposed for digital signal processing by FPGA. An embedded Linux operating system is used to develop the user interface by ARM. According to the experimental results, the inspection instrument can detect flat-bottom holes with diameter of 1.2mm and depth of 60mm.