09.09.2014 Views

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

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

5.9.2.1 Pitch-Catch Methods- Through Transmission<br />

Through transmission testing uses two search units; one unit is used as a<br />

transmitter and the other unit is used as a receiver, as shown in Figure below.<br />

With this technique, the ultrasonic beam passes through the test piece or is<br />

attenuated by one or more discontinuities. Total or partial attenuation of the<br />

signal is possible depending on the severity of the discontinuity. Both<br />

transducers must be properly coupled with a liquid coupling agent to obtain<br />

reliable results. As with other techniques using two search units, greater<br />

efficiency may be obtained by using a ceramic element in the transmitting<br />

search unit and a lithium sulfate element in the receiving unit.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!