| ABSTRACT: |
WELDS ULTRASONIC TOMOGRAPHY BASED ON THE PHASED ANTENNA ARRAYS WITH
SMALL-APERTURE TRANSDUCERS.
A.A. Samokrutov, and A. M. Lutkevich
JSC “Spectrum” – RII”, Moscow, Russia.
The use of antenna arrays in combination with the SAFT signal processing technique currently is rather
promising for welds ultrasonic examination as such an approach from one side - improves testing
productivity and from the other one - simplifies interpretation of UT results obtained in the form of the B-
scans.
One of the actual tasks is to form the acoustic field of shear wave with controlled focus area without use of
the intermediate angle prisms, which worsen the quality of tomographic images but at the same time are
necessary for conversion of wave types. This problem can be solved due to use of the antenna arrays based
on small-aperture transducers (SAT). After theoretical research works were obtained formulas describing
acoustic field of SAT for waves of longitudinal and shear type; determined are the structural transducer’s
parameters that provide effective excitation of the field of shear waves; formulated are requirements
imposed on antenna arrays using SATs.
Described are methods and results of experimental studies of directivity characteristic; results of practical
comparison of efficiency of longitudinal and shear waves forming by various SATs. Presented are the test
objects’ tomograms obtained for longitudinal and shear waves with the help of SAFT technique and use of
the same antenna array.Basing on these results was developed a handheld tomograph for UT of welds with
antenna array, based on SAT without intermediate prisms, and SAFT processor. The productivity rate of this
instrument is 20 frames per second.
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