Graphic Augmented Defect Recognition for Phased Array Ultrasonic Testing on Tubular TKY Joints
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Graphic Augmented Defect Recognition for Phased Array Ultrasonic Testing on Tubular TKY Joints H. Luo1 · Q. H. Chen1 · W. Lin1 Received: 3 January 2020 / Accepted: 22 June 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A graphic augmented defect recognition algorithm was developed for phased array ultrasonic testing (PAUT) on tubular TKY joints. Based on PAUT sector scan (S-scan), 2D maps of the scans are obtained in terms of signal intensity and locations using spatial clustering and segmentation. The transformed S-scan data was further mapped with weld geometrical model to discriminate defect indications from the signals due to weld boundaries. Geometrical features of the identified defect indications were extracted to estimate the size and depth of the defects. The algorithm was verified by experiments on a TKY artefact with purposely-made defects. It shows that our algorithm was able to identify and locate all the defects in the artefact. Compared with the results obtained manually using the standard ultrasonic testing method, the differences of our results in terms of the defect size and depth were within 2 mm. The algorithm, coded into a software tool, demonstrated that the defects in the tubular TKY welds can be detected automatically and visualized in an intuitive manner. Keywords Phased array ultrasonic testing (PAUT) · Sector scan (s-scan) · Density based spatial clustering · Geometrical features · Tubular TKY joint
1 Introduction Tubular T, K, Y joints between pipes or tubes are defined in AWS D1.1 2000 code [1]. As similar types of joints between one to one or one to two pipes or tubes at different intersection angle, they are always combined together and referred as TKY joints. TKY joints of high strength steel are most commonly found in offshore oil structures, such as legs of movable jack-up rigs or jackets of a fixed platform. The joints, fabricated by arc welding, are subject to severe stress and strain from heavy waves and currents in the sea. The joints are all single bevel, tee type joint with a root opening. Single bevel generally increases the strength and stiffness of the joints. However, welding of such joints becomes challenging due to the following reasons. First, no backing ring can be used and all the welding has to be made from outside the joint. Second, the welding is a multiple layer, multiple pass, and * H. Luo [email protected]‑star.edu.sg 1
Singapore Institute of Manufacturing Technology (SIMTech), A*STAR, 2 Fusionopolis Way, #08‑04, Innovis, Singapore 138634, Singapore
all-positioning process across toe to heel of the joint. Facing these difficulties, welding quality cannot be always assured. To ensure structural integrity, 100% inspection of the welds is required. In compliance to AWS and API standard codes [1, 2], tubular TKY weld testing is carried out by inspectors using conventional single element ultrasonic transducer with typical incidence angles of 45°, 60°, and 70°. In order to cover as much weld area as possible, the inspector ne
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