Development of a flexible film electromagnetic acoustic transducer for nondestructive testing

Electromagnetic acoustic transducers (EMATs) have been widely applied for non-contact and coupling-free ultrasonic testing (UT) of metal structures. In this paper, a new EMAT of flexible film type with thickness less than 1 mm, which uses dual coil configuration but without a permanent magnet, is proposed for both ultrasound generation and detection. Instead of using permanent magnet, a planar magnetic coil fed with a rectangular-pulsed current with duration about 1.5 ms is used to generate magnetic flux in the test objects. The obvious advantages of the proposed flexible film EMAT are that it can be easily applied for non-contact and coupling-free UT of curved structures and objects with very narrow inspection space. Pulsed electromagnetic fields and the induced ultrasound waves are studied by simulation and experiment. The results show that the flexible film EMAT has a good performance for generating and receiving ultrasonic waves and can be easily applied for testing of curved structural component with narrow inspection space.