A means of locating defects in steel. When acoustic
energy in the ultrasonic range is passed through
steel, the sound waves tend to travel in straight
lines, rather than diffusing in all directions as they
do in the audible range. If there is a defect in the
path of the beam it will cause a reflection of some
of the energy, depleting the energy transmitted.
This casts an acoustic shadow which can be
monitored by a detector placed opposite the
transducer or energy source. If the acoustic energy
is introduced as a very short burst, then the
reflected energy coming back to the originating
transducer can also be used to show the size and
depth of the defect. Ultrasonic techniques can be
used to detect deeply located defects or those
contained in the surface layer. Skill and experience
are required in interpreting the results portrayed on
the cathode ray tube.