Comparative Evaluation of Defect Sizing Accuracy for Internal Defects in Steel Multi-Pass Welded Joint by PAUT and TOFD

Abstract

To ensure the reliability of steel welds and the integrity of steel structures, it is important to detect defects by using ultrasonic testing and sizing their dimensions with high accuracy. Recently, Phased Array Ultrasonic Testing (PAUT) and Time of Flight Diffraction (TOFD) have been developed. Even when these methods are used, it is said that the location and shape of defects in welded joint affect detectability and sizing accuracy, so further accumulation of the knowledge on these effects is desirable. In this study, the detectability and sizing accuracy of defects were evaluated using PAUT and TOFD to steel multi-pass welded joint specimens with various artificial defects. The types of defects were internal defects, surface defects, and back-side defects, and the shapes were planar and cylinder. The defect detection results show that both methods can detect planar defects, while TOFD was superior in detecting internal cylinder defects. The accuracy of defect length sizing for planar defects was good in both methods. On the other hand, it was considered that the curved surface of the defect was a factor for the poor accuracy of defect length sizing. The accuracy of defect height sizing for planar defects was good in both methods regardless of the defect location, and TOFD accurately sized the height of cylinder defects.