Evaluation of ultrasonic volume- and underclad indications at long distances

Abstract

Analysis techniques are applied in UT examinations if the standard examination provides unacceptable indications and more exact parameters are required for the fracture mechanics evaluation. The necessity for analysis techniques is particularly great where long distances are involved, i.e. when sensitivity is too limited for crack tip detection or when focusing at the reflector location is insufficient, in order to correct the results of the standard examination, which are often too conservative. There are manual analysis procedures, using focusing transducers or time of flight reconstruction methods, and mechanized, computer-assisted procedures, based on the synthetic aperture principle. ALOK and SAFT measurements were performed by the IzfP (NDE Institute) and KWU on volume flaws and findings near the cladding. The results show that, compared with manual measurements, the computer-assisted methods have the advantage that the complete B-scan representation enables better interpretation of the examination interpretation of the examination results, thereby avoiding evaluation errors in individual cases. ALOK reconstructions have the advantage that they can be interpreted in the same way as a manual analysis, thus facilitating for the UT examiner the transition from the manual to the computer-assisted imaging method. Better image reproduction is a feature of the L SAFT reconstructions. Virtual independence from examination parameters is also advantageous.