An SH-wave EMAT technique for gas pipeline inspection
TL;DR: In this paper, a periodic-permanent-magnet (PPM) EMAT is placed inside the pipe, which generates and receives the SH guided waves traveling in the circumferential direction with the axial polarization.
Abstract: An EMAT technique has been developed to detect corrosion defects on the outer surfaces of steel pipelines. A periodic-permanent-magnet (PPM) EMAT is placed inside the pipe, which generates and receives the SH guided waves traveling in the circumferential direction with the axial polarization. Wheels installed on the PPM-EMAT facilitate the linear movement in the axial direction and are useful for a quick inspection. At each point in scanning, the amplitude and phase shift of the round-trip signals in the SH0 and SH1 modes are measured using a superheterodyne phase-sensitive detector. They respond uniquely to surface defects and provide relevant information for locating axial positions of defects and evaluating the depth. The amplitude and phase shift of the SH1 mode are more sensitive to the presence of the defects than those of the SH0 mode. This technique is useful even if the protective resin coating is tightly glued on the pipes and lowered the signal intensity.
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TL;DR: A comprehensive review on pipeline integrity management based on ILI data is provided, including physics-based models and data-driven methods for predicting defect growth for pipelines with different categories of defects.
141 citations
TL;DR: A meridional-array scheme which mimics a single line of transducers along the exterior surface of the pipe in the axial direction is described, and proof of concept results on a pipe sample with an internal wall-thinning are shown.
121 citations
TL;DR: A new variation called helical ultrasound tomography (HUT) is described that uses guided ultrasonic waves along with tomographic reconstruction algorithms that have been developed by seismologists for what they call "cross borehole" tomography.
Abstract: Ultrasonic guided waves have been used for a wide variety of ultrasonic inspection techniques. We describe here a new variation called helical ultrasound tomography (HUT) that uses guided ultrasonic waves along with tomographic reconstruction algorithms that have been developed by seismologists for what they call "cross borehole" tomography. In HUT, the Lamb-like guided waves travel the various helical criss-cross paths between two parallel circumferential transducer arrays instead of the planar criss-cross seismic paths between two boreholes. Although the measurement itself is fairly complicated, the output of the tomographic reconstruction is a readily interpretable map of a quantity of interest such as pipe wall thickness. In this paper we demonstrate HUT via laboratory scans on steel pipe segments into which controlled thinnings have been introduced.
100 citations
TL;DR: In this paper, the authors explored mode conversion of shear horizontal (SH) guided wave when it impinges on smooth defects in plates and found that the fundamental (SH 0 ) and the first higher (SH 1 ) modes exhibited unique mode conversion behaviors in tapered edge.
Abstract: The present study explores mode conversion of shear horizontal (SH) guided wave when it impinges on smooth defects in plates. The fundamental (SH 0 ) and the first higher (SH 1 ) modes were selectively generated by an electromagnetic acoustic transducer in aluminum plates and the propagating modes at various points were detected by a pinducer. The defects had a flat bottom region and tapered edges. Remaining thickness at the bottom defected region was smaller than the so-called cut-off thickness of SH 1 mode. Both modes exhibited unique mode conversion behaviors in tapered edge, which were interpreted with the dispersion relation. Total reflection of SH 1 mode was also observed at a specific condition. Numerical simulation revealed that the continuous wavenumber change in the tapered region and the consequent zero value at cut-off thickness cause this total reflection.
98 citations
TL;DR: In this paper, an elastic metasurface for splitting SV- and P-waves is designed and demonstrated using full wave finite element simulations, which is capable of modulating the phase change of SV-wave while keeping the phase of P-wave unchanged.
Abstract: Although recent advances have made it possible to manipulate electromagnetic and acoustic wavefronts with sub-wavelength metasurface slabs, the design of elastodynamic counterparts remains challenging. We introduce a novel but simple design approach to control SV-waves in elastic solids. The proposed metasurface can be fabricated by cutting an array of aligned parallel cracks in a solid such that the materials between the cracks act as plate-like waveguides in the background medium. The plate array is capable of modulating the phase change of SV-wave while keeping the phase of P-wave unchanged. An analytical model for SV-wave incidence is established to calculate the transmission coefficient and the transmitted phase through the plate-like waveguide explicitly. A complete 2π range of phase delay is achieved by selecting different thicknesses for the plates. An elastic metasurface for splitting SV- and P-waves is designed and demonstrated using full wave finite element simulations. Two metasurfaces for focusing plane and cylindrical SV-waves are also presented.
96 citations
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TL;DR: In this paper, the magnetic-field dependence of the wave amplitudes was studied by examining the magnetic field dependence of a spiral elongated coil placed on a thin plate of low carbon steel, which receives the longitudinal and the shear waves propagating in the thickness direction in the presence of bias magnetic field.
Abstract: The coupling mechanism of the electromagnetic acoustic transducer (EMAT) for bulk waves has been studied by examining the magnetic-field dependence of the wave amplitudes. A spiral elongated coil placed on a thin plate of low carbon steel excites and receives the longitudinal and the shear waves propagating in the thickness direction in the presence of the bias magnetic field. The field dependences of the bulk-wave amplitudes are measured using the electromagnetic acoustic resonance both for the normal and tangential bias fields, which showed different features, depending on the bias-field direction and the wave mode. A two-dimensional model is presented for the explanation of the observed results. The present analysis emphasizes the inclined total field in the derivation of the magnetostriction constants, which is revealed to play an essential role for the wave generation. Both the measurement and the model analysis conclude that the magnetostrictive effect dominates the EMAT phenomena for the bulk waves...
123 citations
Journal Article•
112 citations