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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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In the applet below, the shear (transverse) wave ray path has been added.<br />

The ray paths of the waves can be adjusted by clicking and dragging in the<br />

vicinity of the arrows. Values <strong>for</strong> the angles or the wave velocities can also be<br />

entered into the dialog boxes. It can be seen from the applet that when a<br />

wave moves from a slower to a faster material, there is an incident angle<br />

which makes the angle of refraction <strong>for</strong> the longitudinal wave 90 degrees. As<br />

mentioned on the previous page, this is known as the first critical angle and<br />

all of the energy from the refracted longitudinal wave is now converted to a<br />

surface following longitudinal wave. This surface following wave is sometime<br />

referred to as a creep wave and it is not very useful in <strong>NDT</strong> because it<br />

dampens out very rapidly.

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