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Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

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The most important application of EMATs has been in nondestructive<br />

evaluation (NDE) applications such as flaw detection or material property<br />

characterization. Couplant free transduction allows operation without contact<br />

at elevated temperatures and in remote locations. The coil and magnet<br />

structure can also be designed to excite complex wave patterns and<br />

polarizations that would be difficult to realize with fluid coupled piezoelectric<br />

probes. In the inference of material properties from precise velocity or<br />

attenuation measurements, use of EMATs can eliminate errors associated<br />

with couplant variation, particularly in contact measurements.<br />

Differential velocity is measured using a T1-T2---R fixed array of EMAT<br />

transducer at 0, 45°, 90° or 0°, 90° relative rotational directions depending on<br />

device configuration:

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