Challenges Associated to Uultrasonic Techniques in Characterization of Friction Stir Weld Defects in 27 mm Thick Al 6061-O Plates

Phased array ultrasonic testing (PAUT) has widely emerged as an innovative and improved method of assessing critical flaws in safety critical equipments of industrial plants. The technology gives a clear advantage over a conventional ultrasonic testing (UT). The utilization of advanced form of UT however has associated disadvantages and pitfalls. An attempt has been made to address some of the challenges that are associated to PAUT techniques in characterization of defects in 27 mm Al 6061-O curvilinear welds made from friction stir welding process (FSW). Three distinct defect parameters, i.e., (a) defect length, (b) defect height, and (c) defect position was estimated using PAUT. Quality of results are significantly dependent on important factors. These factors affect the probability of detection (POD). X-ray radiography was carried as a complimentary technique for defect identification. Defect sizing results of PAUT has been assessed and compared against macro-examination results. While PAUT has a proven record of exhibiting better POD, incorrect selection of parameters like probe selection, operator competency, scanning method and defect orientation can result in inconsistent results.