Non-contact imaging of pipe thinning using elastic guided waves generated and detected by lasers

• Published in: The International journal of pressure vessels and piping Vol. 153; pp. 26 - 31
• Main Author: Hayashi, Takahiro
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2017
• Subjects: Defect imaging; Laser ultrasonics; Non-contact NDT; Pipe inspection; Laser ultrasonics; Defect imaging; Pipe inspection; Non-contact NDT
• ISSN: 0308-0161; 1879-3541
• DOI: 10.1016/j.ijpvp.2017.05.006

Defect images in a plate can be obtained by the generation and detection of flexural elastic waves using a pulsed laser and a laser Doppler vibrometer. The author has developed an experimental system—called an E-camera—that establishes extremely fast imaging. This paper describes the application of the E-camera to imaging of pipe thinning. The first experiments using a straight pipe revealed that resonance patterns appear significantly at certain frequencies due to guided waves propagating both in the longitudinal and circumferential directions, which is a unique characteristic of pipe structures. A pipe thinning located at various circumferential positions could also be visualized appropriately. Moreover, pipe thinning was successfully detected in both straight and branch pipes located at a distance of 6.0 m from the E-camera system. •Non-contact defect imaging system was applied to inspection of pipe thinning.•Circumferential resonance patterns were obtained at the cut-off frequencies.•A pipe thinning was visualized appropriately for straight and branch pipes.