Publications
321 results found
Van Pamel A, Huthwaite P, Brett CR, et al., 2015, Finite Element Modelling of Wave Propagation in Highly Scattering Materials, 42nd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: American Institute of Physics (AIP), ISSN: 1551-7616
Ultrasonic inspection of highly scattering materials presents challenges for industry. This article describes a Finite Element modelling methodology to simulate wave propagation within polycrystalline materials. Concerns are answered regarding its required mesh sampling and ability to capture the complex scattering physics. It is shown that grain scattering phenomena are closely reproduced across a range of scattering regimes. The procedure is subsequently applied to investigate the optimal configuration of an array inspecting such a material. It is found that in certain situations, separating emitter and receiver can be advantageous as this reduces the received backscatter.
Leinov E, Cawley P, Lowe MJS, 2015, Guided Wave Attenuation in Coated Pipes Buried in Sand, 42nd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: American Institute of Physics (AIP), ISSN: 1551-7616
Long-range guided wave testing (GWT) is routinely used for the monitoring and detection of corrosion defects in above ground pipelines in various industries. The GWT test range in buried, coated pipelines is greatly reduced compared to aboveground pipelines due to energy leakage into the embedding soil. In this study, we aim to increase test ranges for buried pipelines. The effect of pipe coatings on the T(0,1) and L(0,2) guided wave attenuation is investigated using a full-scale experimental apparatus and model predictions. Tests are performed on a fusion-bonded epoxy (FBE)-coated 8” pipe, buried in loose and compacted sand over a frequency range of 10-35 kHz. The application of a low impedance coating is shown to effectively decouple the influence of the sand on the ultrasound leakage from the buried pipe. We demonstrate ultrasonic isolation of a buried pipe by coating the pipe with a Polyethylene (PE)-foam layer that has a smaller impedance than both pipe and sand and the ability to withstand the overburden load from the sand. The measured attenuation in the buried PE-foam-FBE-coated pipe is substantially reduced, in the range of 0.3-1.2 dBm−1 for loose and compacted sand conditions, compared to buried FBE-coated pipe without the PE-foam, where the measured attenuation is in the range of 1.7-4.7 dBm−1. The acoustic properties of the PE-foam are measured independently using ultrasonic interferometry technique and used in model predictions of guided wave propagation in a buried coated pipe. Good agreement is found between the attenuation measurements and model predictions. The attenuation exhibits periodic peaks in the frequency domain corresponding to the through-thickness resonance frequencies of the coating layer. The large reduction in guided wave attenuation for PE-coated pipes would lead to greatly increased GWT test ranges, so such coatings would be attractive for new pipeline installations.
Haith MI, Ewert U, Hohendorf S, et al., 2015, Modelling Based Radiography for NDE of Subsea Pipelines, 42nd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: American Institute of Physics (AIP), ISSN: 1551-7616
This work presents the use of limited experimental measurements to develop a set of calibrated simulation parameters that can then be used for reliable simulation of subsea pipeline inspections. The modelling software aRTist is used as the simulation tool, and the calibration is through comparison with experimental images of a well characterised sample in a water tank. Image quality parameters such as signal-to-noise ratio, contrast and basic spatial resolution are compared with the aim of matching simulated values to experimental results. Currently the model is partially calibrated, with signal-to-noise ratio successfully matched while differences are still found in contrast-to-noise ratio comparisons. This means that measurements depending on absolute intensity are not accurate enough in the simulation at this stage. However, the simulation is found to be accurate for wall thickness measurements in tangential images, which are not based on absolute intensity, with simulated and experimental cases producing similar results
Ewert U, Tschaikner M, Hohendorf S, et al., 2015, Corrosion Monitoring with Tangential Radiography and Limited View Computed Tomography, 42nd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: American Institute of Physics (AIP), ISSN: 1551-7616
Accurate and reliable detection of subsea pipeline corrosion is required in order to verify the integrity of the pipeline. A laboratory trial was conducted with a representative pipe sample. The accurate measurement of the wall thickness and corrosion was performed with high energy X-rays and a digital detector array. A 7.5 MV betatron was used to penetrate a stepped pipe and a welded test pipe of 3 m length and 327 mm outer diameter, with different artificial corrosion areas in the 24 mm thick steel wall. The radiographs were taken with a 40 x 40 cm² digital detector array, which was not large enough to cover the complete pipe diameter after magnification. A C-arm based geometry was tested to evaluate the potential for automated inspection in field. The primary goal was the accurate measurement of wall thickness conforming to the standard. The same geometry was used to explore the ability of a C-arm based scanner in asymmetric mode for computed tomography (CT) measurement, taking projections covering only two thirds of the pipe diameter. The technique was optimized with the modelling software aRTist. A full volume of the pipe was reconstructed and the CT data set was used for reverse engineering, providing a CAD file for further aRTist simulations to explore the technique for subsea inspections.
Egerton JS, Lowe MJS, Halai HV, et al., 2015, Improved FE Simulation of Ultrasound in Plastics, 42nd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: American Institute of Physics (AIP), ISSN: 1551-7616
Some UK and US nuclear power stations have begun introducing high-density polyethylene (HDPE) pipes to certain cooling water circuits. HDPE offers improved performance over existing pipe materials, such as cast iron, by not corroding in-ternally or externally, yet occasional defects form in HDPE pipe fusion joints at the production stage. This necessitates suitable volumetric NDE to safely and reliably assess joint integrity. Ultrasonic NDE is the most viable current technique, but improved inspection capability is needed, given that the challenges of NDE of plastics differ significantly from those of metals. This also necessitates an accurate and reliable wave propagation simulation technique, such as finite-element (FE) modelling. Accurate FE modelling of ultrasound in high-density polyethylene (HDPE) must account for frequency-dependent behaviour but, the most ap-parent way to do so – frequency domain FE modelling – is prohibitively computationally expensive and potentially impossible to solve for all but the smallest models. Here we present a multiband time domain FE simulation technique to address this. The proposed multiband technique is a computationally efficient and accurate approach to time domain FE modelling of ultrasonic wave propagation. It could, for example, be used to validate the NDE of a large range of candidate fusion joint defects in HDPE. The proposed model uses a small number of time domain FE simulations at individual frequency bands that together cover the bandwidth of interest. The frequency dependence of acoustic properties of ultrasound is accurately represented for HDPE and could readily be applied to other media.
Huthwaite P, Lowe M, Cawley P, 2015, Guided Wave Tomography Performance Analysis, 42nd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: American Institute of Physics (AIP), ISSN: 1551-7616
Quantifying wall loss caused by corrosion is a significant challenge for the petrochemical industry. Corrosion commonly occurs at pipe supports, where surface access for inspection is limited. Guided wave tomography is pursued as a solution to this: guided waves are transmitted through the region of interest from an array, and tomographic reconstruction techniques are applied to the measured signals in order to produce a map of thickness. There are many parameters in the system which can affect the performance; this paper investigates how the accuracy varies as defect width and depth, operating frequency and guided wave mode are all changed. For the S0 mode, the best performance was seen around 170kHz on the 10mm plate, with poor performance seen at almost all other frequencies. A0 showed better performance across a broad range of frequencies, with resolution improving with frequency as the wavelength reduced. However, it was shown that the resolution limit did drop relative to the wavelength, limiting the performance at high frequencies slightly.
Quintanilla FH, Fan Z, Lowe MJS, et al., 2015, Dispersion Loci of Guided Waves in Viscoelastic Composites of General Anisotropy, 42nd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: American Institute of Physics (AIP), ISSN: 1551-7616
Guided waves play an important role in many applications of NDE to structures of flat and cylindrical geometry. In order to develop and optimise the inspection, it is essential to have a good understanding of the wave modes that can propagate in the target structure. These can be complicated, especially in structures composed of multiple layers, anisotropic properties or materials that exhibit damping that absorbs the energy of the waves. Dispersion curves in anisotropic viscoelastic media are presented here. They have been computed by using a pseudospectral collo-cation method, details of its implementation are briefly outlined and references to the relevant literature given.
Leinov E, Lowe MJS, Cawley P, 2015, Investigation of guided wave propagation and attenuation in pipe buried in sand, Journal of Sound and Vibration, Vol: 347, Pages: 96-114, ISSN: 0022-460X
Long-range guided wave testing is a well-established method for detection of corrosion defects in pipelines. The method is currently used routinely for above ground pipelines in a variety of industries, e.g. petrochemical and energy. When the method is applied to pipes buried in soil, test ranges tend to be significantly compromised and unpredictable due to attenuation of the guided wave resulting from energy leakage into the embedding soil. The attenuation characteristics of guided wave propagation in an 8 in. pipe buried in sand are investigated using a laboratory full-scale experimental rig and model predictions. We report measurements of attenuation of the T(0,1) and L(0,2) guided wave modes over a range of sand conditions, including loose, compacted, mechanically compacted, water saturated and drained. Attenuation values are found to be in the range of 1.65–5.5 dB/m and 0.98–3.2 dB/m for the torsional and longitudinal modes, respectively, over the frequency of 11–34 kHz. The application of overburden pressure modifies the compaction of the sand and increases the attenuation. Mechanical compaction of the sand yields similar attenuation values to those obtained with applied overburden pressure. The attenuation decreases in the fully water-saturated sand, and increases in drained sand to values comparable with those obtained for compacted sand. Attenuation measurements are compared with Disperse software model predictions and confirm that the attenuation phenomenon in buried pipes is essentially governed by the bulk shear velocity in the sand. The attenuation behaviour of the torsional guided wave mode is found not to be captured by a uniform soil model; comparison with predictions obtained with the Disperse software suggest that this is likely to be due to a layer of sand adhering to the surface of the pipe.
Seher M, Huthwaite P, Lowe MJS, et al., 2015, Model-Based Design of Low Frequency Lamb Wave EMATs for Mode Selectivity, Journal of Nondestructive Evaluation, Vol: 34, ISSN: 1573-4862
A low-frequency, omni-directional A0 Lamb wave ElectroMagnetic Acoustic Transducer (EMAT) is developed for applications in guided wave tomography, operating at 50 kHz on a 10 mm thick steel plate. The key objective is to excite an acceptably pure A0 wave mode in relation to the S0 mode, which can also be present at this operating point and is desired to be suppressed by approximately 30 dB. For that, a parametric Finite Element (FE) model of the design concept is implemented in a commercially available FE software, where the bias magnetic field is calculated initially, then combined with the eddy current caused by the induction coil to produce a force. A numerical optimization process employing a genetic algorithm is set up and the EMAT design is optimized to yield an improved A0 mode selectivity. The parameters subjected to optimization are the magnet diameter and the magnet lift-off, which control the direction of the exciting force in the skin depth layer and therefore the mode selectivity. Although there are three possible electromagnetic acoustic interaction mechanisms, the optimisation considers only the Lorentz force, as its performance surface contains a clear optimum and from the optimised design a physical prototype is built. The FE model is validated against measurements on an aluminium plate for the Lorentz force excitation mechanism and on a steel plate for both the Lorentz and magnetisation force. For the steel plate, it is found that only considering the Lorentz force leads to a significant overestimation of the mode selectivity, as the S0 amplitude is underestimated by the Lorentz force, but the A0 amplitude remains mainly uninfluenced. Further, it has been found that additionally including the magnetisation force into the optimisation leads to a better mode selectivity, however, the optimisation drives the optimum to a minimum magnet diameter and therefore reduces the EMAT sensitivity. In a numerical study robustness is shown for fair
Lan B, lowe M, dunne F, 2015, A generalized spherical harmonic deconvolution to obtain texture of cubic materials from ultrasonic wave speed, Journal of the Mechanics and Physics of Solids, Vol: 83, Pages: 221-242, ISSN: 0022-5096
In this paper, the spherical harmonic convolution approach for HCP materials (Lan et al., 2015) is extended into a generalised form for the principal purpose of bulk texture determination in cubic polycrystals from ultrasonic wave speed measurements. It is demonstrated that the wave speed function of a general single crystal convolves with the polycrystal Orientation Distribution Function (ODF) to make the resultant polycrystal wave speed function such that when the three functions are expressed in harmonic expansions, the coefficients of any one function may be determined from the coefficients of the other two. All three Euler angles are taken into account in the description of the ODF such that the theorem applies for all general crystal systems.The forward problem of predicting polycrystal wave speed with knowledge of single crystal properties and the ODF is solved for all general cases, with validation carried out on cubic textures showing strong sensitivity to texture and excellent quantitative accuracy in predicted wave speed amplitudes. Importantly, it is also revealed by the theorem that the cubic structure is one of only two crystal systems (the other being HCP) whose orientation distributions can be inversely determined from polycrystal wave velocities by virtue of their respective crystal symmetries. Proof of principle is then established by recovering the ODFs of representative cubic textures solely from the wave velocities generated from a computational model using these texture inputs, and excellent accuracies are achieved in the recovered ODF coefficients as well as the resultant pole figures. Hence the methodology is argued to provide a powerful technique for wave propagation studies and bulk texture measurement in cubic polycrystals and beyond.Keywords Texture; Generalised spherical convolution; Ultrasound; Cubic polycrystals
Shi F, Choi W, Lowe MJS, et al., 2015, The validity of Kirchhoff theory for scattering of elastic waves from rough surfaces, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 471, ISSN: 1364-5021
Quintanilla FH, Lowe MJS, Craster RV, 2015, Modeling guided elastic waves in generally anisotropic media using a spectral collocation method, Journal of the Acoustical Society of America, Vol: 137, Pages: 1180-1194, ISSN: 0001-4966
Guided waves are now well established for some applications in the non-destructive evaluation of structures and offer potential for deployment in a vast array of other cases. For their development, it is important to have reliable and accurate information about the modes that propagate for particular waveguide structures. Essential information that informs choices of mode transducer, operating frequencies, and interpretation of signals, among other issues, is provided by the dispersion curves of different modes within various combinations of geometries and materials. In this paper a spectral collocation method is successfully used to handle the more complicated and realistic waveguide problems that are required in non-destructive evaluation; many pitfalls and limitations found in root-finding routines based on the partial wave method are overcome by using this approach. The general cases presented cover anisotropic homogeneous perfectly elastic materials in flat and cylindrical geometry. Non-destructive evaluation applications include complex waveguide structures, such as single or multi-layered fiber composites, lined, bonded and buried structures. For this reason, arbitrarily multi-layered systems with both solid and fluid layers are also addressed as well as the implementation of interface models of imperfect boundary conditions between layers.
Pettit JR, Walker AE, Lowe MJS, 2015, Modelling NDE Pulse-Echo inspection Of Misorientated Planar Rough Defects Using An Elastic Finite Element Method, 41st Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 1730-1737, ISSN: 0094-243X
Shi F, Choi W, Skelton E, et al., 2015, Investigation of the Validity of the Elastic Kirchhoff Approximation for Rough Cracks Using a Finite Element Approach, 41st Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 1722-1729, ISSN: 0094-243X
Seher M, Huthwaite P, Lowe M, et al., 2015, Experimental Study of A0 Lamb Wave Tomography, 41st Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 245-253, ISSN: 0094-243X
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- Citations: 1
Leinov E, Cawley P, Lowe MJS, 2015, Guided Wave Attenuation in Pipes Buried in Sand, 41st Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 227-236, ISSN: 0094-243X
Pettitt JR, Walker A, Lowe MJS, 2015, An optimised stiffness reduction method for simulating infinite elastic space using commercial Finite Elements codes, 13th Anglo-French Physical Acoustics Conference (AFPAC), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
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- Citations: 1
Van Pamel A, Huthwaite P, Brett CR, et al., 2015, A Finite Element Model Investigation of Ultrasonic Array Performance for Inspecting Polycrystalline Materials, 41st Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 1007-1014, ISSN: 0094-243X
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- Citations: 1
Van Pamel A, Brett CR, Lowe MJS, 2015, An Initial Investigation into Pseudo-Coloring for Ultrasonic NDE of Polycrystalline Materials, 41st Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 1031-1036, ISSN: 0094-243X
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- Citations: 1
Quintanilla FH, Lowe M, Craster R, 2015, Dispersion Curves for Guided Elastic Waves in Multilayered Anisotropic Media Generated with the Spectral Method, 41st Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 739-745, ISSN: 0094-243X
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Huthwaite P, Shi F, Van Pamel A, et al., 2015, High-Speed GPU-Based Finite Element Simulations for NDT, 41st Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 1815-1819, ISSN: 0094-243X
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Van Pamel A, Brett CR, Lowe MJS, 2014, A Methodology for Evaluating Detection Performance of Ultrasonic Array Imaging Algorithms for Coarse-Grained Materials, IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, Vol: 61, Pages: 2042-2053, ISSN: 0885-3010
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- Citations: 11
Shi F, Choi W, Skelton EA, et al., 2014, A Time-Domain Finite Element Boundary Integration Method for Ultrasonic Nondestructive Evaluation, IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, Vol: 61, Pages: 2054-2066, ISSN: 0885-3010
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- Citations: 6
Mark AF, Fan Z, Azough F, et al., 2014, Investigation of the elastic/crystallographic anisotropy of welds for improved ultrasonic inspections, Materials Characterization, Vol: 98, Pages: 47-53, ISSN: 1873-4189
Pettit JR, Walker A, Cawley P, et al., 2014, A stiffness reduction method for efficient absorption of waves at boundaries for use in commercial Finite Element codes, Ultrasonics, Vol: 54, Pages: 1868-1879, ISSN: 0041-624X
Commercially available Finite Element packages are being used increasingly for modelling elastic wave propagation problems. Demand for improved capability has resulted in a drive to maximise the efficiency of the solver whilst maintaining a reliable solution. Modelling waves in unbound elastic media to high levels of accuracy presents a challenge for commercial packages, requiring the removal of unwanted reflections from model boundaries. For time domain explicit solvers, Absorbing Layers by Increasing Damping (ALID) have proven successful because they offer flexible application to modellers and, unlike the Perfectly Matched Layers (PMLs) approach, they are readily implemented in most commercial Finite Element software without requiring access to the source code. However, despite good overall performance, this technique requires the spatial model to extend significantly outside the domain of interest. Here, a Stiffness Reduction Method (SRM) has been developed that operates within a significantly reduced spatial domain. The technique is applied by altering the damping and stiffness matrices of the system, inducing decay of any incident wave. Absorbing region variables are expressed as a function of known model constants, helping to apply the technique to generic elastodynamic problems. The SRM has been shown to perform significantly better than ALID, with results confirmed by both numerical and analytical means.
Deschamps M, Lowe M, 2014, Preface, ULTRASONICS, Vol: 54, Pages: 1719-1719, ISSN: 0041-624X
Lan B, Lowe M, Dunne FPE, 2014, Experimental and computational studies of ultrasound wave propagation in hexagonal close-packed polycrystals for texture detection, Acta Materialia, Vol: 63, Pages: 107-122, ISSN: 1359-6454
Texture in hexagonal close-packed (hcp) polycrystalline metals, often developed during thermomechanical processing, affects ultrasonic wave velocity. In this study, the relationship between bulk texture and ultrasonic wave velocity in aggregates of (predominantly) hcp grains is investigated using theoretical, numerical and experimental methods. A representative volume element methodology is presented, enabling the effects of texture on ultrasonic wave speed to be investigated in two-phase polycrystals, and is employed to examine the ultrasonic response of random polycrystals, textured polycrystals and macro-zones often observed in titanium alloys. Numerical results show that ultrasonic wave speed varies progressively with changing texture, over a range of ∼200 m s−1, within bounds set by the two extreme single-crystal orientations. Experimental ultrasound studies and full electron backscatter diffraction (EBSD) characterization are conducted on unidirectionally rolled and cross-rolled Ti–6Al–4V samples in three orthogonal directions. In addition, the EBSD-determined textures are incorporated within the polycrystal model and predicted ultrasonic velocities compared directly with ultrasonic experiments. Good quantitative agreement is obtained and both the experimental and computed results demonstrate that ultrasonic velocity profiles exist for random, unidirectionally rolled and cross-rolled textures. The combined results indicate the possibility of the development of a methodology for bulk texture determination within Ti polycrystal components using ultrasound.
Pettit JR, Walker A, Lowe MJS, 2014, Improved Detection of Rough Defects for Ultrasonic NDE Inspections Based on Finite Element Modeling of Elastic Wave Scattering, 10th International Conference on Barkhausen and Micro-Magnetics (ICBM), Publisher: AMER INST PHYSICS, Pages: 521-528, ISSN: 0094-243X
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- Citations: 4
Pettit JR, Walker A, Lowe MJS, 2014, A Stiffness Reduction Method for Efficient Modelling of Waves in Unbound Media Using Commercially Available Finite Elements Packages, 10th International Conference on Barkhausen and Micro-Magnetics (ICBM), Publisher: AMER INST PHYSICS, Pages: 579-586, ISSN: 0094-243X
Leinov E, Cawley P, Lowe MJS, 2014, Investigation of Guided Waves Propagation in Pipe Buried in Sand, 10th International Conference on Barkhausen and Micro-Magnetics (ICBM), Publisher: AMER INST PHYSICS, Pages: 271-278, ISSN: 0094-243X
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- Citations: 6
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