Image registration guided wavefield tomography for shear wave velocity model building

Liu

et al. 2021

IEEE Access

Defect inspection in pipes at the early stage is of crucial importance to maintain the ongoing safety and suitability of the equipment before it presents an unacceptable risk. Due to the nature of detection methods being costly or complex, the efficiency and accuracy of results obtained hardly meet the requirements from industries. To explore a rapid and accurate technique for surface defects detection, a novel approach QDFT (Quantitative Detection of Fourier Transform) has been recently proposed by authors to efficiently reconstruct defects. However, the accuracy of this approach needs to be further improved. In this paper, a modified QDFT method with integration of an integral coefficient updating strategy, called QDFTU (quantitative detection of Fourier transform of updating), is developed to reconstruct the defect profile with a high level of accuracy throughout iterative calculations of integral coefficients from the reference model updated by a termination criteria (RMSE, root mean square error). Moreover, dispersion equations of circumferential guided waves in pipes are derived in the helical coordinate to accommodate the stress and displacement calculations in the scattered field using hybrid FEM. To demonstrate the superiority of the developed QDFTU in terms of accuracy and efficiency, four types of defect profiles, i.e., a rectangular flaw, a multi-step flaw, a double-rectangular flaw, and a triple-rectangular flaw, are examined. Results show the fast convergence of QDFTU can be identified by no more than three updates for each case and its high accuracy is observed by a smallest difference between the predicted defect profile and the real one in terms of mean absolute percentage error (MSPE) value, which is 6.69% in the rectangular-flaw detection example. INDEX TERMSCircumferential guided wave, Hybrid FEM, reconstruction, reference model, updating strategy. YIHUI DA received the B.S. degree in theoretical and applied mechanics from Henan Polytechnic University, Henan, China, in 2009, and the M.S. degree in general and fundamental mechanics and the Ph.D. degree in engineering mechanics from the Nanjing University of Aeronautics and Astronautics, Nanjing, China, in 2014 and 2018, respectively.Since 2019, he has been working as a Postdoctoral Researcher with the Nanjing University of Aeronautics and Astronautics. His research interests include the numerical modeling of ultrasonic guided waves, ultrasonic nondestructive evaluation, and signal processing.

Section: Introductionmentioning

confidence: 99%

A Rapid and Accurate Technique With Updating Strategy for Surface Defect Inspection of Pipelines

Liu

et al. 2021

IEEE Access

“…In the thickness maps of guided wave tomography, the iterative hybrid algorithm for robust breast ultrasound tomography (HARBUT) was used to improve the accuracy of reconstructions of defects [28]. An iterative S-wave velocity inversion method guided by image registration was developed by Yang [29]. A guided wave tomography method based on full waveform inversion (FWI) was considered to discretize the frequency components from low to high frequencies [30].…”

Section: Introductionmentioning

confidence: 99%

A More Accurate Reconstruction Method for Detecting Large-Depth Defects in Plates Using SH Guided Waves

et al. 2020

Acta Mech. Solida Sin.

The inspection of thickness thinning defects and corrosion defects is greatly significant for the health prediction of plate structures. The main aim of this research is to propose a novel and effective approach to achieve the accurate and rapid detection of arbitrary defects using shear horizontal (SH) guided waves, particularly for large-depth and complex defects. The proposed approach combines the quantitative detection of Fourier transform (QDFT) with a reference model-based strategy to improve the accuracy of large-depth defect detection. Since the shallow defect profile is theoretically constructed by inverse Fourier transform of the product of reflection coefficients and integral coefficients of reference models, the unknown large-depth defect can be initially assessed using the relevant information from a predefined reference model. By iteratively updating the integral coefficients of reference models, the accuracy of reconstruction of large-depth defects is much improved. To achieve the converged defect profile, a termination criterion, the root mean square error (RMSE), is applied to guarantee the construction of defects with a high level of accuracy. Moreover, the hybrid finite element method (HFEM) is used to simulate the propagation of SH guided waves in plates for calculating the reflection coefficients of plates with defects. Finally, to demonstrate the capability of the developed reconstruction method for defect detection in terms of accuracy and efficiency, three types of large-depth defect profiles, i.e., a rectangular flaw, a double-rectangular flaw, and a complex flaw, are examined. Results show that the discrepancy between the predicted defect profile and the real one is quite small, even in the largest-depth defect case where the defect depth is equal to 0.733 times the plate thickness, the minimal difference is observed. It is noted that the fast convergence of the proposed approach can be achieved by no more than ten updates for the worst case.

“…Unfortunately, the current traveltime inversion method in acoustic media is hard to straightforwardly implement in elastic case. Even using the reflection tomography, we need the a priori information of important horizons and employ the particular P or S events to constrain the inversion Broto et al (2003); Du et al (2012); Yang et al (2015).…”

Section: Introductionmentioning

confidence: 99%

Elastic wave-equation-based reflection kernel analysis and traveltime inversion using wave mode decomposition

Geophysical Journal International

Cheng

Guo

et al. 2018

Elastic reflection waveform inversion (ERWI) utilizes reflections to update the low and intermediate wavenumbers in the deeper part of elastic models and can provide good initial models for elastic full waveform inversion (EFWI). Although ERWI aims to mitigate the nonlinearity of inversion when starting from a poor initial model, it suffers from the cycle-skipping problem due to the objective function of waveform fitting. Building initial P-and S-wave velocity models for EFWI through elastic wave-equation reflection traveltime inversion (ERTI) would be effective and robust since traveltime information relates to the background model more linearly. However, the current implementations of acoustic traveltime inversion is not straightforward in elastic media due to the existence of S-wavefields. Wave mode decomposition, both on the recording surface and in the extrapolated wavefields, is important for ERTI. First, for seismic data with P-wave sources, the P/S separation of multicomponent seismograms isolates the PP and PS reflection events and thus make it possible to extract the event-to-event time-shifts of these isolated reflections through dynamic image warping (DIW). Then, we can use the traveltime residuals of PP and PS reflections to build the objective function for ERTI. Second, based on the investigation of the complicated reflection kernels in an elastic medium, we demonstrate the necessity of wave mode decomposition applied on the extrapolated elastic wavefields, to suppress the artefacts induced by the undesirable cross-correlations of the components in forward and back-propagated wavefields. Therefore, the decomposition of surface recording data and extrapolated wavefields guarantees the dominate contribution of the traveltime is included during the ERTI. Accordingly, we propose a two-stage method to first build the P-wave background velocity using the separated PP reflections and then build the S-wave background velocity using the separated PS reflections based on the well-recovered P-wave velocity model. A numerical example of the Sigsbee2A model shows the effectiveness of the proposed ERTI approach.