Paul Davidson

Scanning Arrangement

EMAT, a non-contact transducer used to produce ultrasonic waves in test pieces. WIS has presented a number of papers about EMATs. One thing that has surprised are still questions like "Aren't EMATs still just a good lab tool ? There aren't any commercial applications out there."

This presentation showed the NDE industry that EMATs are a viable commercial inspection tool. They are widely used in variety of industries for everything from process control to field inspection. One reason for the apparent "recent" success of EMATs is that most people were not aware of many of the commercial systems that date back to the mid and late 1980s.

EMATs can solve many of the common problems encountered with traditional ultrasonic techniques. In addition to being non-contact, EMATs will work at high temperatures and pass through various coatings while scanning at high speeds. Because there is no incidence angle or crystal selection required, EMATs are less prone to operator error and will produce more repeatable results. Also EMAT's have the very real advantage of being able to easily generate a variety of ultrasonic wave modes. Besides the familiar longitudinal and SV waves (shear vertical), EMATs can also generate SH (shear horizontal) waves and Lamb waves (guided waves).