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Guided wave travel time tomography for bends

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Author: Volker, A.W.F. · Bloom, J.G.P.
Type:article
Date:2010
Publisher: AIP
Institution: TNO Industrie en Techniek
Source:37th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE 2010, 18-23 July 2010, San Diego, CA, USA, 1335, 223-230
series:
AIP Conference Proceedings
Identifier: 442949
ISBN: 9780735408883
Keywords: Materials · Corrosion Monitoring · Dispersion · Guided Wave · Inversion · Tomography · Travel Time · Ultrasonic · Industrial Innovation · Fluid Mechanics Chemistry & Energetics · PID - Process & Instrumentation Development · TS - Technical Sciences

Abstract

The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography has been developed to map the wall thickness using the travel times of guided waves. The method has been demonstrated for straight pipes. The extension of this method to bends is not straightforward because natural focusing occurs due to geometrical path differences. This yields a phase jump, which complicates travel time picking. Because ray-tracing is no longer sufficient to predict the travel times a recursive wave field extrapolation has been developed. The method uses a short spatial convolution operator to propagate a wave field through a bend. The method allows to calculate the wave field at the detector ring, including the phase jump as a consequence of the natural focusing. The recursive wave field extrapolation is done in the space-frequency domain. Therefore dispersion effects can be included easily in the forward modeling. Comparison with measurements shows the accuracy of the method.