Ultrasonic methods are widely used in the non-destructive testing of
all manner of welded
joints. However, due to the practical difficulties involved in the NDT
of incomplete or hot welds,
much of this testing is undertaken after a joint is completed.
Alternatively, if defects could
be detected between weld runs then potentially large cost savings would
result from reduced
wastage of materials and gouging/repair times. In addition, if the NDT
results could be interpreted fast
enough (e.g. by an automated system) then weld process control may also
be possible.
This short artcicle describes some of the problems to be encountred
when using pulse echo methods
for flaw detection in incomplete welds. As an alternative, Time of
Flight Diffraction methods are
proposed and image processing techniques for automatic defect detection
are described.