Comparison of Phased Array Ultrasound to
Conventional Ultrasound and Radiographic Testing
for Bridge Welds
Publication: Publication Date: 1 January 2017Testing Method:
Phased array ultrasonic testing (PAUT) was
performed on nine complete joint penetration (CJP)
weld samples with internal and external weld
discontinuities to develop a discontinuity sizing
procedure using the backward tip diffraction
technique. The weld samples include flat plate CJP
welds, CJP T-joint welds, and a thickness transition
weld. The discontinuity sizing results were
compared to the physical size of the weld discontinuities
by sectioning the weld samples. It was
found that the response signal would vary greatly
depending on the scanning face and index offset.
Therefore, the combined results from first and
second leg scans from each available scanning
face were used to estimate the discontinuity size.
While the estimated discontinuity size was
typically quite close to the actual discontinuity
height and length for planar discontinuities, some
difficulties were encountered when there was
limited access for scanning, which caused the
discontinuity to be undersized. Oversizing was also
possible due to beam spread at long sound paths
or from misinterpretation of surface gouges.
Additional research is necessary to refine this
technique to determine the size of volumetric
discontinuities using PAUT. Additional testing was
performed using conventional ultrasonic testing
(UT) and radiographic testing (RT) to compare with
the PAUT results and the acceptability of each
sample under various acceptance criteria. It was
found that weld discontinuities that were
rejectable under combined conventional UT and RT
per AWS D1.5 may be acceptable under alternate
PAUT acceptance criteria. This typically occurred
when the weld discontinuity was volumetric in
nature such as internal porosity since UT is not as
effective at discerning the limits of volumetric
discontinuities compared with planar discontinuities.
The variation in acceptance criteria may also
be attributed to the fact that line scanning with
PAUT may not maximize the response amplitude
compared with raster scanning for conventional
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