SYNTHETIC FOCUSING FOR HIGH RESOLUTION GUIDED WAVE PIPE INSPECTION: FURTHER RESULTS AND ROBUSTNESS STUDIES

It is difficult to achieve high resolution for guided wave signals used in pipe inspection. The main reasons include overlap of the reflected waves, diversity of the guided wave’s mode and so on. This paper presents a minimum entropy deconvolution algorithm to solve the problem caused by low resolution of the measured signals. Some experiments were carried out to validate the algorithm. The experimental set-up consists of two pipes, one excitor and two accelerometers. The excitor was used to generate the guided wave signals. Two accelerometers were attached to the pipe end and pipe wall respectively，and were used to measure the guided wave signals. Results show that good estimate of the reflection coefficient is obtained and the resolution of measured signals has been improved. As a result, the length of two pipe samples has been calculated with a reasonable accuracy and the position of the defect in experimental pipe has also been acertained. All of these show a new efficient way for guided wave signal processing in pipe inspection.

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Guided Wave Focusing Mechanics in Pipe

Ultrasonic Nondestructive Evaluation for Material Science and Industries ◽

10.1115/pvp2003-1850 ◽

2003 ◽

Author(s):

Takahiro Hayashi ◽

Koichiro Kawashima ◽

Zongqi Sun ◽

Joseph L. Rose

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Guided Waves ◽

Wave Structure ◽

Guided Wave ◽

Pipe Inspection ◽

Specific Point ◽

Wave Focusing ◽

Beam Focusing ◽

Subsequent Time

Guided waves can be used in pipe inspection over long distances. Presented in this paper is a beam focusing technique to improve the S/N ratio of the reflection from a tiny defect. Focusing is accomplished by using non-axisymmetric waveforms and subsequent time delayed superposition at a specific point in a pipe. A semi-analytical finite element method is used to present wave structure in the pipe. Focusing potential is also studied with various modes and frequencies.

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Accurate Thickness Inversion of Corrosion Using A1 Lamb Wave

10.1115/qnde2021-75313 ◽

2021 ◽

Author(s):

Min Lin ◽

Yang Liu

Keyword(s):

High Resolution ◽

Oil And Gas ◽

Residual Life ◽

Early Stage ◽

Corrosion Damage ◽

Oil And Gas Industry ◽

Forward Modeling ◽

Guided Wave ◽

Velocity Inversion ◽

Wave Tomography

Abstract Corrosion is one of the most critical issues in the oil and gas industry, leading to severe environmental and economic problems. Due to the high cost and serious safety risk of corrosion, it is essential to improve current corrosion testing techniques to detect corrosion damages at an early stage. Guided wave tomography (GWT) demonstrates its great potential to inspect and quantify the corrosion damage. GWT is capable of determining the residual life of corrosion structures by quantifying the remaining wall thickness. In this paper, an accurate guided wave tomography technique incorporating full waveform inversion (FWI) and higher-order Lamb waves (A1 mode) is presented for plate-like structures, which is able to get high-resolution reconstruction results. The technique consists of three steps: forward modeling, velocity inversion and thickness reconstruction. The forward modeling is computed by solving the elastic full-wave equations in 2-D time domain by using the finite difference method. High-resolution phase velocity inversion can then be obtained by minimizing the waveform misfit function between simulated and recorded data using a second order optimization method, which updates the velocity model from low to high frequencies iteratively. Finally, the velocity variations can be transformed into depth profiles by using the dispersive characteristics of ultrasonic guided waves; therefore, the thickness reconstruction can be obtained. The numerical simulations are performed on an aluminum plate with a complicated corrosion defect. By comparing the thickness reconstruction maps using both A1 and A0 modes, the results demonstrate that FWI with A1 mode can achieve significantly better resolution of corrosion imaging than that with A0 mode.

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