Defect imaging with guided waves in a pipe

Abstract

Guided wave techniques are expected to become an effective means for rapid, long-range inspection of pipes. Such techniques still have many practical difficulties in application, however, due to the complex characteristics of guided waves such as dispersion and their multimodal nature. A defect imaging technique is developed in this study to overcome the complexities of guided wave inspection. Received signals are separated into single-mode waveforms with a mode extraction technique and then spatial waveforms on the pipe surface at an arbitrary time are reconstructed. The predicted waveforms can provide a defect image at the moment when an incident wave arrives at a defect region, which is based on a time-reversal technique. This defect imaging technique is experimentally verified using eight signals detected at eight different circumferential positions. Images of artificial defects are obtained with one-hole and two-hole test pipes, and increasing the frequency of incident waves increases the resolution of the images. Holes and pipe ends are recognizable in the images, but the reconstructed images contain some errors in the area behind the defects where guided waves do not propagate or do not reflect back to the receiving transducers.

Review of magnetostrictive patch transducers and applications in ultrasonic nondestructive testing of waveguides

“…The performance improvement of MPTs is, however, an issue, so studies on mechanical impedance matching [61], magnetic flux concentration [62], and phased arraying for the selection of a specific mode [63] have been conducted. Various MPT applications were also reported for rotating shafts [64], wire ropes/cables and anchor rods [65], pipelines with mechanical attachments [66], pipes with axial cracks [67], and inspections of various defects and imaging [68][69][70][71][72][73]. In terms of inspection applications, a method that uses the Joule effect to generate torsional waves which can be applied for the inspection of rotating shafts [74] was proposed [75][76][77], while a pipe-inspection method that uses in situ magnetostrictive tapes and torsional waves was also suggested [78].…”

Vibration energy analysis of a plate for defect imaging with a scanning laser source technique

“…Defect imaging techniques that use such guided wave signals need to achieve a trade-off between long-range propagation and sufficient image resolution. [8][9][10][11][12] The authors have studied defect imaging using a scanning laser source (SLS) technique as a new and efficient imaging method for inspecting plate-like structures. [13][14][15][16][17][18] The SLS technique is a measurement technique in which a laser source of elastic waves is scanned over a plate-like structure, and a large number of waveforms are detected for a large number of wave sources.…”

“…The results of experiments conducted to verify the energy variations in the vicinity of a crack were in good agreement with the numerical results for dipole loading. Guided waves are often used to inspect large plate-like structures, such as pipes, tanks, and airplane bodies and wings, [1][2][3][4][5][6][7][8][9][10][11][12] owing to such waves' prominent characteristic of long-range propagation. In most cases, rapid long-range inspections are conducted by measuring guided waves reflected or transmitted by defects.…”

Characterisation of hidden defects using the near-field ultrasonic enhancement of Lamb waves

“…The use of ultrasonic waves with displacements throughout the thickness of a material, such as Lamb waves in sheets and guided waves in pipes [14,15] , enables inspection of areas of the system that cannot be accessed directly, such as the internal surface of a pipe [8,16] . Several long-distance ultrasonic inspection methods exist that monitor in the defect far-field (defined as the region starting at a distance of several wavelengths away from the defect [17] ) through changes in the reflection or transmission of guided waves as they interact with surfacebreaking defects, and these methods are capable of estimating the position and depth of defects over a distance of several metres [8,9] .…”