Development of a Movable Inspection Sensor for a Pipe Using an Electromagnetic Acoustic Transducer of the Magnetostriction Effect Type

Electromagnetic acoustic transducers (EMATs) using the magnetostriction effect have many advantages for nondestructive inspections. For example, this type of EMAT easily generates an ultrasonic wave in magnetic material samples without any contact, which does not require a coupling medium, and thus is movable and can easily be installed. The objective of this study is to develop a nondestructive inspection technique using a pipe wave, a type of ultrasonic wave that can travel a long distance along a pipe, which can be used as a nondestructive inspection method with an EMAT. The pipe wave must be selected to have an optimum mode to diagnose the shape or depth of defects. We developed EMATs for a torsional mode (T-mode) pipe wave and a longitudinal mode (L-mode) pipe wave. We then machined several defects in the test pipes and attempted to inspect them. The results show that the trial EMATs have the potential to distinguish the type, sizes and depth of defects.