Advances in
ultrasonic testing have led to the widespread application of ultrasonic
scans to detect shrinkage, porosity, cracks, and other defects deep within
castings. In the simplest type of ultrasonic inspection ultrasonic waves
are initiated at the surface by a high frequency transducer, they reflect
from defects or from the rear surface of the casting and are picked up by
the transducer. A plot of the amplified reflected waves on a CRT shows
the presence of defects within the casting. More sophisticated ultrasonic
testing techniques involve immersion of the casting in a water bath
enhancing the pickup of the ultrasonic waves to provide a two dimensional
map of the defects present. These techniques are applied to a wide
variety of castings, ingots, and forgings. Ultrasonic testing is covered
in ASTM specifications:
ASTM
E11411
ASTM E 214
ASTM E 587
ASTM E 1001
Source:
Investment casting Institute Handbook 1997 Edition
