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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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Comparison between EMAT and Piezoelectric Transducers<br />

As an <strong>Ultrasonic</strong> <strong>Testing</strong> (<strong>UT</strong>) method, EMAT has all the advantages of <strong>UT</strong><br />

compared to other <strong>NDT</strong> methods. Just like piezoelectric <strong>UT</strong> probes, EMAT<br />

probes can be used in pulse echo, pitch-catch, and through-transmission<br />

configurations. EMAT probes can also be assembled into phased array<br />

probes, delivering focusing and beam steering capabilities.<br />

Advantages<br />

Compared to piezoelectric transducers, EMAT probes have the following<br />

advantages:<br />

1. No couplant is needed. Based on the transduction mechanism of EMAT,<br />

couplant is not required. This makes EMAT ideal <strong>for</strong> inspections at<br />

temperatures below the freezing point and above the evaporation point of<br />

liquid couplants. It also makes it convenient <strong>for</strong> situations where couplant<br />

handling would be impractical.<br />

2. EMAT is a non-contact method. Although proximity is preferred, a physical<br />

contact between the transducer and the specimen under test is not required.

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