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  • Conference paper
    Huthwaite P, Seher M, 2015,

    Helical Path Separation For Guided Wave Tomography

    , 41st Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 761-770, ISSN: 0094-243X
  • Journal article
    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
  • Journal article
    Shi F, Choi W, Skelton EA, Lowe MJS, Craster RVet 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
  • Journal article
    Escobar-Ruiz E, Wright DC, Collison IJ, Cawley P, Nagy PBet al., 2014,

    Reflection Phase Measurements for Ultrasonic NDE of Titanium Diffusion Bonds

    , JOURNAL OF NONDESTRUCTIVE EVALUATION, Vol: 33, Pages: 535-546, ISSN: 0195-9298
  • Journal article
    Mark AF, Fan Z, Azough F, Lowe MJS, Withers PJet al., 2014,

    Investigation of the elastic/crystallographic anisotropy of welds for improved ultrasonic inspections

    , Materials Characterization, Vol: 98, Pages: 47-53, ISSN: 1873-4189
  • Journal article
    Pettit JR, Walker A, Cawley P, Lowe MJSet 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.
  • Journal article
    Gajdacsi A, Jarvis AJC, Huthwaite P, Cegla FBet al., 2014,

    Reconstruction of Temperature Distribution in a Steel Block Using an Ultrasonic Sensor Array

    , Journal of Nondestructive Evaluation, Vol: 33, Pages: 458-470, ISSN: 1573-4862

    Permanently installed ultrasonic sensors have thecapability of measuring much smaller changes in the signalthan conventional sensors that are used for ultrasonic inspections.This is because uncertainties associated with couplingfluids and positional offsets are eliminated. Therefore it ispotentially possible to monitor the onset of material degradation.A particular degradation mechanism that we are keento monitor is high temperature hydrogen attack; where theamount of damage is linked to a drop in ultrasonic velocitywhich we hope can be monitored for with an ultrasonic array.The changes introduced in the ultrasonic propagation velocityare expected to be of the order of 1 % and in practice theyare observable only from a very limited field of view (i.e. fromthe outside of a pipe) and therefore the reconstruction is challengingto accomplish. In order to explore the feasibility ofthis, we are investigating the reconstruction of a non-uniformtemperature distribution which allows us to quickly evaluatethe sensitivity of our method to small spatial variations inultrasonic velocity of the material. Two reconstruction algorithmswere implemented and their performance comparedin simulated and real measurements. The results of the testswere encouraging: local temperature differences as low as10 ◦C could be detected, which corresponds to a local propagationvelocity change of 5 m/s (0.15 % relative velocitychange).
  • Journal article
    Deschamps M, Lowe M, 2014,

    Preface

    , ULTRASONICS, Vol: 54, Pages: 1719-1719, ISSN: 0041-624X
  • Journal article
    Leinov E, Jackson MD, 2014,

    Experimental measurements of the SP response to concentration and temperature gradients in sandstones with application to subsurface geophysical monitoring

    , JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Vol: 119, Pages: 6855-6876, ISSN: 2169-9313
  • Journal article
    Huthwaite P, 2014,

    Evaluation of inversion approaches for guided wave thickness mapping

    , Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 470, Pages: 1-28, ISSN: 1364-5021

    Accurate inversion is vital for quantitative imaging, including ultrasonic guided wave tomography, where thickness maps of plate-like structures are reconstructed to quantify corrosion damage. The dispersive properties of guided waves are often exploited to enable thickness maps to be produced from wave speed reconstructions. Ray tomography, diffraction tomography and a hybrid algorithm combining their features were investigated to reconstruct wave speed. Test data produced from simple defects of different sizes using a realistic full elastic guided wave model and the equivalent idealized acoustic model were passed to the imaging algorithms, generating wave speed maps, and, from these, thickness maps. For both datasets, ray tomography exhibited poor resolution. Diffraction tomography performed better, but was limited to shallow, small defects. The hybrid algorithm achieved the best results, giving a resolution around 1.5–2 wavelengths from the realistic test data compared to half wavelength from the idealized case. These results were validated with experimental data, and also extended to a realistic corrosion patch confirming the trends demonstrated with simple defects. The resolution loss with realistic data compared with idealized data indicates the acoustic model cannot accurately capture guided wave scattering and an alternative approach is necessary for better resolution reconstructions.
  • Journal article
    Escobar-Ruiz E, Ruiz A, Hassan W, Wright DC, Collison IJ, Cawley P, Nagy PBet al., 2014,

    Non-linear Ultrasonic NDE of Titanium Diffusion Bonds

    , JOURNAL OF NONDESTRUCTIVE EVALUATION, Vol: 33, Pages: 187-195, ISSN: 0195-9298
  • Journal article
    Attarian VA, Cegla FB, Cawley P, 2014,

    Long-term stability of guided wave structural health monitoring using distributed adhesively bonded piezoelectric transducers

    , STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL, Vol: 13, Pages: 265-280, ISSN: 1475-9217
  • Journal article
    Huthwaite P, 2014,

    Accelerated finite element elastodynamic simulations using the GPU

    , Journal of Computational Physics, Vol: 257, Pages: 687-707, ISSN: 0021-9991

    An approach is developed to perform explicit time domain finite element simulations of elastodynamic problems on the graphical processing unit, using Nvidiaʼs CUDA. Of critical importance for this problem is the arrangement of nodes in memory, allowing data to be loaded efficiently and minimising communication between the independently executed blocks of threads. The initial stage of memory arrangement is partitioning the mesh; both a well established ‘greedy’ partitioner and a new, more efficient ‘aligned’ partitioner are investigated. A method is then developed to efficiently arrange the memory within each partition. The software is applied to three models from the fields of non-destructive testing, vibrations and geophysics, demonstrating a memory bandwidth of very close to the cardʼs maximum, reflecting the bandwidth-limited nature of the algorithm. Comparison with Abaqus, a widely used commercial CPU equivalent, validated the accuracy of the results and demonstrated a speed improvement of around two orders of magnitude. A software package, Pogo, incorporating these developments, is released open source, downloadable from http://www.pogo-fea.com/ to benefit the community.
  • Journal article
    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.
  • Conference paper
    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
  • Conference paper
    Huthwaite P, Lowe MJS, 2014,

    High Speed Finite Element Simulations on the Graphics Card

    , 10th International Conference on Barkhausen and Micro-Magnetics (ICBM), Publisher: AMER INST PHYSICS, Pages: 2007-2014, ISSN: 0094-243X
  • Conference paper
    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
  • Conference paper
    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
  • Conference paper
    Seher M, Huthwaite P, Lowe M, Nagy P, Cawley Pet al., 2014,

    Numerical Design Optimization of an EMAT for A0 Lamb Wave Generation in Steel Plates

    , 10th International Conference on Barkhausen and Micro-Magnetics (ICBM), Publisher: AMER INST PHYSICS, Pages: 340-347, ISSN: 0094-243X
  • Conference paper
    Van Pamel A, Lowe MJS, Brett CR, 2014,

    Evaluation of Ultrasonic Array Imaging Algorithms for Inspection of a Coarse Grained Material

    , 10th International Conference on Barkhausen and Micro-Magnetics (ICBM), Publisher: AMER INST PHYSICS, Pages: 156-163, ISSN: 0094-243X

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