39 results found
Choi W, Shi F, Lowe MJS, et al., 2018, Rough surface reconstruction of real surfaces for numerical simulations of ultrasonic wave scattering, NDT and E International, Vol: 98, Pages: 27-36, ISSN: 0963-8695
The scattering of waves by rough surfaces plays a significant role in many fields of physical sciences including ultrasonics where failure surfaces are often rough and their accurate identification is critical. The prediction of the strength of scattering can be hampered when the roughness is not adequately characterised and this is a particular issue when the surface roughness is within an order of the incident wavelength. Here we develop a methodology to reconstruct, and accurately represent, rough surfaces using an AutoRegressive (AR) process that then allows for rapid numerical simulations of ultrasonic wave rough surface scattering in three dimensions. Gaussian, exponential and AR surfaces are reconstructed based on real surface data and the statistics of the surfaces are compared with each other. The statistics from the AR surfaces agree well with those from actual rough surfaces, taken from experimental samples, in terms of the heights as well as the gradients, which are the two main factors in accurately predicting the wave scattering intensities. Ultrasonic rough surface scattering is simulated numerically using the Kirchhoff approximation, and comparisons with Gaussian, exponential, AR and real sample surfaces are performed; scattering intensities found using AR surfaces show the best agreement with the real sample surfaces.
Skelton E, Craster RV, Colombi A, et al., 2018, The multi-physics metawedge: graded arrays on fluid-loaded elastic plates and the mechanical analogues of rainbow trapping and mode conversion, New Journal of Physics, Vol: 20, ISSN: 1367-2630
We consider the propagation and mode conversion of flexural-acoustic waves along a fluid-loaded graded array of elastic resonators, forming a metasurface. The multi-physics nature of the problem, coupling two disparate physical systems, brings both challenges and novel features not previously seen in so-called bifunctional metamaterials. In particular, by using an appropriately designed graded array of resonators, we show that it is possible to employ our metasurface to mode-convert sub-sonic surface flexural waves into bulk acoustic waves and vice-versa; transferring energy between two very different physical systems. Whilst the sub-sonic mechanical surface wave is dispersive, the bulk acoustic wave is dispersionless and radiates energy at infinity. We also show that this bifunctional metasurface is capable of exhibiting the classical effect of rainbow trapping for sub-sonic surface waves.
Shi F, Lowe M, Skelton EA, et al., 2018, A time-domain finite element boundary integral approach for elastic wave scattering, Computational Mechanics, Vol: 61, Pages: 471-483, ISSN: 0178-7675
The response of complex scatterers, such as rough or branched cracks, to incident elastic waves is required in many areas of industrial importance such as those in non-destructive evaluation and related fields; we develop an approach to generate accurate and rapid simulations. To achieve this we develop, in the time domain, an implementation to efficiently couple the finite element (FE) method within a small local region, and the boundary integral (BI) globally. The FE explicit scheme is run in a local box to compute the surface displacement of the scatterer, by giving forcing signals to excitation nodes, which can lie on the scatterer itself. The required input forces on the excitation nodes are obtained with a reformulated FE equation, according to the incident displacement field. The surface displacements computed by the local FE are then projected, through time-domain BI formulae, to calculate the scattering signals with different modes. This new method yields huge improvements in the efficiency of FE simulations for scattering from complex scatterers. We present results using different shapes and boundary conditions, all simulated using this approach in both 2D and 3D, and then compare with full FE models and theoretical solutions to demonstrate the efficiency and accuracy of this numerical approach.
Choi W, Skelton EA, Pettit J, et al., 2016, A generic hybrid model for the simulation of three-dimensional bulk elastodynamics for use in nondestructive evaluation, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol: 63, Pages: 726-736, ISSN: 0885-3010
A three-dimensional (3-D) generic hybrid model is developed for the simulation of elastic waves in applications in nondestructive evaluation (NDE) that efficiently links different solution strategies but, crucially, is independent of the particular schemes employed. This is an important step forward in facilitating rapid and accurate large-scale simulations, and this advances the two-dimensional (2-D) generic hybrid methodology recently developed by the authors. The hybrid model provides an efficient and effective tool for creating highly accurate simulations that model the wave propagation and scattering, enabling the interpretation of inspection data; the new methodology is verified against other numerical simulations. Furthermore, its deployment to simulate wave reflection from side-drilled holes (SDHs), comparing the results with experimental measurements, provides a realistic demonstration as well as further validation.
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
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
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
Antonakakis T, Craster RV, Guenneau S, et al., 2014, An asymptotic theory for waves guided by diffraction gratings or along microstructured surfaces, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 470, ISSN: 1364-5021
Choi W, Skelton EA, Shi F, et al., 2014, Rough Surface Reconstruction for Ultrasonic NDE Simulation, 10th International Conference on Barkhausen and Micro-Magnetics (ICBM), Publisher: AMER INST PHYSICS, Pages: 587-594, ISSN: 0094-243X
Choi W, Skelton E, Lowe MJS, et al., 2013, UNIT CELL FINITE ELEMENT MODELLING FOR ULTRASONIC SCATTERING FROM PERIODIC SURFACES, 39th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 83-90, ISSN: 0094-243X
Choi W, Skelton E, Lowe MJS, et al., 2012, GENERIC HYBRID MODELS FOR THREE-DIMENSIONAL ULTRASONIC NDE, 38th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 126-133, ISSN: 0094-243X
Rajagopal P, Drozdz M, Skelton E, et al., 2012, On the use of absorbing layers to simulate the propagation of elastic waves in unbounded isotropic media using commercially available Finite Element packages, NDT and E International, Vol: TBC
Rajagopal P, Skelton EA, Choi W, et al., 2012, A generic hybrid model for bulk elastodynamics, with application to ultrasonic non-destructive evaluation, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol: 59, Pages: 1239-TBC
Rajagopal P, Skelton E, Lowe M, et al., 2011, GENERIC TIME-DOMAIN HYBRID MODELS FOR ULTRASONIC NDE, 37th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 67-74, ISSN: 0094-243X
Skelton EA, Craster RV, Shanin AV, et al., 2010, Embedding formulae for scattering by three-dimensional structures, WAVE MOTION, Vol: 47, Pages: 299-317, ISSN: 0165-2125
Rajagopal P, Skelton E, Lowe M, et al., 2010, FINITE ELEMENT BASED HYBRID MODELS FOR ULTRASONIC NDE USING COMMERCIAL PACKAGES, 36th Annual Review of Progress in Quantitative Nondestructive Evaluation, Publisher: AMER INST PHYSICS, Pages: 662-+, ISSN: 0094-243X
Skelton EA, Craster RV, Shanin AV, 2008, Embedding formulae for diffraction by non-parallel slits, QUARTERLY JOURNAL OF MECHANICS AND APPLIED MATHEMATICS, Vol: 61, Pages: 93-116, ISSN: 0033-5614
Skelton EA, Adams SDM, Craster RV, 2007, Guided elastic waves and perfectly matched layers, WAVE MOTION, Vol: 44, Pages: 573-592, ISSN: 0165-2125
Drozdz M, Skelton E, Craster RV, et al., 2007, Modeling bulk and guided waves in unbounded elastic media using absorbing layers in commercial finite element packages, 33rd Annual Review of Progress in Quantitative Nondestructive Evaluation, Publisher: AMER INST PHYSICS, Pages: 87-94, ISSN: 0094-243X
Skelton EA, 2003, Acoustic scattering by a cylindrical shell with symmetric line constraints in the heavy fluid-loading limit, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, Vol: 113, Pages: 299-308, ISSN: 0001-4966
Skelton EA, 2002, Line force receptance of an elastic cylindrical shell with heavy exterior fluid loading, JOURNAL OF SOUND AND VIBRATION, Vol: 256, Pages: 131-153, ISSN: 0022-460X
Skelton EA, 2002, A new identity for the infinite product of zeros of Bessel functions of the first kind or their derivatives, JOURNAL OF MATHEMATICAL ANALYSIS AND APPLICATIONS, Vol: 267, Pages: 338-344, ISSN: 0022-247X
Skelton EA, 2001, Scattering of a normally incident plane wave by a rigid rectangle, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 457, Pages: 1757-1785, ISSN: 1364-5021
Skelton EA, 1999, Acoustic scattering by a closed semi-infinite fluid-loaded elastic cylindrical shell, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 455, Pages: 1637-1681, ISSN: 1364-5021
Skelton EA, James JH, 1997, Theoretical acoustics of underwater structures, Publisher: Imperial College Pr, ISBN: 9781860940859
This important book provides an account of the linear acoustics of basic isotropic/anisotropic structures excited by time-harmonic and transient mechanical forces and acoustic sources.
SKELTON EA, JAMES JH, 1995, APPROXIMATE THEORY OF SOUND-SCATTERING BY A PERIODICALLY PERFORATED PLATE WITH IMPEDANCE INSERTS, JOURNAL OF SOUND AND VIBRATION, Vol: 183, Pages: 421-434, ISSN: 0022-460X
SKELTON EA, 1995, ACOUSTIC SCATTERING BY A RIGID DISK OR ANNULUS CLAMPED TO 2 CONCENTRIC CYLINDRICAL ELASTIC SHELLS, JOURNAL OF SOUND AND VIBRATION, Vol: 181, Pages: 635-655, ISSN: 0022-460X
SKELTON EA, 1993, ACOUSTIC SCATTERING BY A FINITE ELASTIC PLATE CONNECTING 2 FLUID-LOADED PARALLEL PLATES, PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 443, Pages: 429-444, ISSN: 1364-5021
SKELTON EA, JAMES JH, 1993, ACOUSTICS OF AN ANISOTROPIC LAYERED CYLINDER, JOURNAL OF SOUND AND VIBRATION, Vol: 161, Pages: 251-264, ISSN: 0022-460X
Skelton EA, 1993, Theoretical models for predicting the acoustic characteristics of fibre-reinforced materials, Acoustics of Advanced Materials for Underwater Applications
The use of fibre-renofrced materials is becoming more common as they can be used to form strong lightweight structures.There is therefore a requirement to understand their acoustic properties. The theoretical methods outlined in this paper have been developed to provide a basis for computer programs to predict numerically the acoustic scattering by, or radiation from, certain relevant canonical problems.
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