Long-Range Testing of Welded Elbow Pipe Using the T(0,1) Mode Ultrasonic Guided Wave

An experimental investigation of sensitivity in defect detection in welded elbow pipes using the T(0, 1) mode guided wave was carried out. A piezoelectric ring-shaped sensor system was cramped on one of the two straight parts in the straight-elbow-straight setting. An artificial defect was introduced into the other straight part. To evaluate the sensitivities, the depth of the artificial defect was gradually increased to 2.0 mm by 0.05 mm increments. The following are the obtained experimental results. (1) Spurious signals due to the two welds, which could be markedly changed by varying the welding conditions were found. (2) These spurious signals interfered with and masked the defect signal, but changes in signal amplitude owing to the incremental defect could be sufficiently detected. (3) Sensitivities of defect detection in welded elbow pipes were approximately 1/4–1/5 that in a straight pipe. At the end of the paper, the characteristics of the observed waveform in the welded elbow pipes are discussed for use in the guided wave inspection.