Long Range Ultrasonic Guided Wave Focusing in Pipe for Large Defect Circumferential Length Analysis

摘要

Planar saw cuts and volumetric elliptical corrosion with different circumferential lengths are studied using ultrasonic guided wave focusing techniques in steel pipe. A circumferential scan is achieved by focusing at 44 circumferential positions around the pipe at a specific distance. The maximum amplitude of the defect echo is recorded with respect to each circumferential focal position in producing an experimental angular profile of the reflected wave. The maximum amplitude of the angular profiles occurs at the angle of the defect circumferential location. The energy reflected from the defects with different cross sectional areas (CSA) for each focusing position can be calculated from the focused angular profile. Comparison between the experimental angular profiles and the theoretical ones provides us with a good estimate of the defect circumferential length.