Publications
247 results found
Sutton AP, 2016, Invited reply to the Comment by A Morawiec, Proceedings of the Royal Society A: Mathematical, Physical & Engineering Sciences, ISSN: 1364-5021
The points raised in Morawiec’s Comment areconsidered carefully. The question of the shortestdistance between two grain boundaries remainsunresolved and requires further research.
Gurrutxaga Lerma B, Balint DANIEL, Dini DANIELE, et al., 2015, Elastodynamic image forces on dislocations, Proceedings of the Royal Society A: Mathematical, Physical & Engineering Sciences, Vol: 471, ISSN: 1364-5021
The elastodynamic image forces on edge and screw dislocations in the presence of a planar-free surface are derived. The explicit form of the elastodynamic fields of an injected, quiescent screw dislocation are also derived. The resulting image forces are affected by retardation effects: the dislocations experience no image force for a period of time defined by the arrival and reflection at the free surface of the dislocation fields. For the case of injected, stationary dislocations, it is shown that the elastodynamic image force tends asymptotically to the elastotatic prediction. For the case of injected, moving dislocations, it is shown that the elastodynamic image force on both the edge and the screw dislocations is magnified by inertial effects, and becomes increasingly divergent with time; this additional effect, missing in the elastostatic description, is shown to be substantial even for slow moving dislocations. Finally, it is shown that the elastodynamic image force of an edge dislocation moving towards the surface at the Rayleigh wave speed becomes repulsive, rather than attractive; this is suggestive of instabilities at the core of the dislocation, and likely resonances with the free surface.
Sutton AP, Banks EP, Warwick AR, 2015, The five-dimensional parameter space of grain boundaries, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 471, ISSN: 1364-5021
To specify a grain boundary at a macroscopic length scale requires the specification of five degrees of freedom. We use a specification in which three degrees of freedom associated with the boundary misorientation are in an orthogonal subspace from two associated with the mean boundary plane. By using Rodrigues vectors to describe rotations, we show how paths through these subspaces may be characterized. Some of these paths correspond to physical processes involving grain boundaries during microstructural evolution. Exploiting the orthogonality of the subspaces, a metric to measure ‘distance’ between two boundaries is defined in terms of the minimum set of rotations required to map one boundary on to the other. We compare our metric with others that have appeared. The existence of rotational symmetry in face-centred cubic crystals leads to as many as 2304 equivalent specifications of a boundary. We illustrate this multiplicity of descriptions for the (111) twin and a more general boundary. We present an algorithm to evaluate the geodesic distance between two boundaries, and apply it to identify the path along which the distance between these two boundaries is minimized. In general, the shortest path does not involve descriptions of boundary misorientations with the smallest misorientation angles.
Gurrutxaga Lerma BENAT, Balint DS, Dini D, et al., 2015, The mechanisms governing the activation of dislocation sources in aluminum at different strain rates, Journal of the Mechanics and Physics of Solids, Vol: 84, Pages: 273-292, ISSN: 1873-4782
This article examines the time to activate Frank–Read sources in response to macroscopic strain rates ranging from 101 s−1 to 1010 s−1 in aluminium under athermal conditions. We develop analytical models of the bowing of a pinned dislocation segment as well as numerical simulations of three dimensional dislocation dynamics. We find that the strain rate has a direct influence on both the activation time and the source strength of Frank–Read sources at strain rates up to 106 s−1, and the source strength increases in almost direct proportion to the strain rate. This contributes to the increase in the yield stress of materials at these strain rates. Above 106 s−1, the speed of the bowing segments reaches values that exceed the domain of validity of the linear viscous drag law, and the drag law is modified to account for inertial effects on the motion of the dislocation. As a result the activation times of Frank–Read sources reach a finite limit at strain rates greater than 108 s−1, suggesting that Frank–Read sources are unable to operate before homogeneous nucleation relaxes elastic stresses at the higher strain rates of shock loading. Elastodynamic calculations are carried out to compare the contributions of Frank–Read sources and homogeneous nucleation of dislocations to plastic relaxation. We find that at strain rates of 5×107 s−1 homogeneous nucleation becomes the dominant generation mechanism.
Hammad A, Swinburne TD, Hasan H, et al., 2015, Theory of the deformation of aligned polyethylene, Proceedings of the Royal Society A: Mathematical, Physical & Engineering Sciences, Vol: 471, ISSN: 1471-2946
Solitons are proposed as the agents of plastic and viscoelastic deformation in aligned polyethylene. Interactions between straight, parallel molecules are mapped rigorously onto the Frenkel–Kontorova model. It is shown that these molecular interactions distribute an applied load between molecules, with a characteristic transfer length equal to the soliton width. Load transfer leads to the introduction of tensile and compressive solitons at the chain ends to mark the onset of plasticity at a well-defined yield stress, which is much less than the theoretical pull-out stress. Interaction energies between solitons and an equation of motion for solitons are derived. The equation of motion is based on Langevin dynamics and the fluctuation–dissipation theorem and it leads to the rigorous definition of an effective mass for solitons. It forms the basis of a soliton dynamics in direct analogy to dislocation dynamics. Close parallels are drawn between solitons in aligned polymers and dislocations in crystals, including the configurational force on a soliton. The origins of the strain rate and temperature dependencies of the viscoelastic behaviour are discussed in terms of the formation energy of solitons. A failure mechanism is proposed involving soliton condensation under a tensile load.
Gurrutxaga-Lerma B, Balint DS, Dini D, et al., 2015, The Role of Homogeneous Nucleation in Planar Dynamic Discrete Dislocation Plasticity, Journal of Applied Mechanics-Transactions of the ASME, Vol: 82, ISSN: 1528-9036
Homogeneous nucleation of dislocations is the dominant dislocation generation mechanismat strain rates above 108 s1; at those rates, homogeneous nucleation dominates theplastic relaxation of shock waves in the same way that Frank–Read sources control theonset of plastic flow at low strain rates. This article describes the implementation ofhomogeneous nucleation in dynamic discrete dislocation plasticity (D3P), a planarmethod of discrete dislocation dynamics (DDD) that offers a complete elastodynamictreatment of plasticity. The implemented methodology is put to the test by studying fourmaterials—Al, Fe, Ni, and Mo—that are shock loaded with the same intensity and astrain rate of 1010 s1. It is found that, even for comparable dislocation densities, the latticeshear strength is fundamental in determining the amount of plastic relaxation a materialdisplays when shock loaded. [DO
Gurrutxaga-Lerma B, Balint DS, Dini D, et al., 2015, Attenuation of the dynamic yield point of shocked aluminum using elastodynamic simulations of dislocation dynamics, Physical Review Letters, Vol: 114, Pages: 1-5, ISSN: 0031-9007
When a metal is subjected to extremely rapid compression, a shock wave is launched that generates dislocations as it propagates. The shock wave evolves into a characteristic two-wave structure, with an elastic wave preceding a plastic front. It has been known for more than six decades that the amplitude of the elastic wave decays the farther it travels into the metal: this is known as “the decay of the elastic precursor.” The amplitude of the elastic precursor is a dynamic yield point because it marks the transition from elastic to plastic behavior. In this Letter we provide a full explanation of this attenuation using the first method of dislocation dynamics to treat the time dependence of the elastic fields of dislocations explicitly. We show that the decay of the elastic precursor is a result of the interference of the elastic shock wave with elastic waves emanating from dislocations nucleated in the shock front. Our simulations reproduce quantitatively recent experiments on the decay of the elastic precursor in aluminum and its dependence on strain rate.
Gurrutxaga Lerma B, Balint DS, Dini D, et al., 2014, Dynamic Discrete Dislocation Plasticity, Advances in Applied Mechanics, Publisher: Elsevier, Pages: 93-224, ISBN: 978-0-12-800130-1
This chapter concerns with dynamic discrete dislocation plasticity (D3P), a two- dimensional method of discrete dislocation dynamics aimed at the study of plastic relaxation processes in crystalline materials subjected to weak shock loading. Traditionally, the study of plasticity under weak shock loading and high strain rate has been based on direct experimental measurement of the macroscopic response of the material. Using these data, well-known macroscopic constitutive laws and equations of state have been formulated. However, direct simulation of dislocations as the dynamic agents of plastic relaxation in those circumstances remains a challenge. In discrete dislocation dynamics (DDD) methods, in particular the two-dimensional discrete dislocation plasticity (DDP), the dislocations are modeled as discrete discontinuities in an elastic continuum. However, current DDP and DDD methods are unable to adequately simulate plastic relaxation because they treat dislocation motion quasi- statically, thus neglecting the time-dependent nature of the elastic fields and assuming that they instantaneously acquire the shape and magnitude predicted by elastostatics. This chapter reproduces the findings by Gurrutxaga-Lerma, Balint, Dini, Eakins, and Sutton (2013), who proved that under shock loading, this assumption leads to models that invariably break causality, introducing numerous artifacts that invalidate quasi- static simulation techniques. This chapter posits that these limitations can only be overcome with a fully time-dependent formulation of the elastic fields of dislocations. In this chapter, following the works of Markenscoff and Clifton (1981) and Gurrutxaga- Lerma et al. (2013), a truly dynamic formulation for the creation, annihilation, and nonuniform motion of straight edge dislocations is derived. These solutions extend the DDP framework to a fully elastodynamic formulation that has been called dynamic discrete dislocation plasticity (D3P). This chapter describes t
Swinburne TD, Dudarev SL, Sutton AP, 2014, Classical Mobility of Highly Mobile Crystal Defects, PHYSICAL REVIEW LETTERS, Vol: 113, ISSN: 0031-9007
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- Citations: 16
Gurrutxaga-Lerma B, Balint DS, Dini D, et al., 2014, Dynamic Discrete Dislocation Plasticity, Advances in Applied Mechanics, Vol: 47, ISSN: 0065-2156
This chapter concerns with dynamic discrete dislocation plasticity (D3P), a two- dimensional method of discrete dislocation dynamics aimed at the study of plastic relaxation processes in crystalline materials subjected to weak shock loading. Traditionally, the study of plasticity under weak shock loading and high strain rate has been based on direct experimental measurement of the macroscopic response of the material. Using these data, well-known macroscopic constitutive laws and equations of state have been formulated. However, direct simulation of dislocations as the dynamic agents of plastic relaxation in those circumstances remains a challenge. In discrete dislocation dynamics (DDD) methods, in particular the two-dimensional discrete dislocation plasticity (DDP), the dislocations are modeled as discrete discontinuities in an elastic continuum. However, current DDP and DDD methods are unable to adequately simulate plastic relaxation because they treat dislocation motion quasi- statically, thus neglecting the time-dependent nature of the elastic elds and assuming that they instantaneously acquire the shape and magnitude predicted by elastostatics. This chapter reproduces the ndings by Gurrutxaga-Lerma, Balint, Dini, Eakins, and Sutton (2013), who proved that under shock loading, this assumption leads to models that invariably break causality, introducing numerous artifacts that invalidate quasi- static simulation techniques. This chapter posits that these limitations can only be overcome with a fully time-dependent formulation of the elastic elds of dislocations. In this chapter, following the works of Markensco and Clifton (1981) and Gurrutxaga- Lerma et al. (2013), a truly dynamic formulation for the creation, annihilation, and nonuniform motion of straight edge dislocations is derived. These solutions extend the DDP framework to a fully elastodynamic formulation that has been called dynamic discrete dislocation plasticity (D3P). This chapter describes the s
Broadbent RJ, Spencer JS, Mostofi AA, et al., 2014, Accelerated simulations of aromatic polymers: application to polyether ether ketone (PEEK), MOLECULAR PHYSICS, Vol: 112, Pages: 2672-2680, ISSN: 0026-8976
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- Citations: 4
Gurrutxaga-Lerma B, Balint D, Dini D, et al., 2013, A dynamic discrete dislocation plasticity method for the simulation of plastic relaxation under shock loading, Proceedings of the Royal Society A: Mathematical, Physical & Engineering Sciences, Vol: 469, ISSN: 1364-5021
In this article, it is demonstrated that current methods of modelling plasticity as the collective motion of discrete dislocations, such as two-dimensional discrete dislocation plasticity (DDP), are unsuitable for the simulation of very high strain rate processes (106 s−1 or more) such as plastic relaxation during shock loading. Current DDP models treat dislocations quasi-statically, ignoring the time-dependent nature of the elastic fields of dislocations. It is shown that this assumption introduces unphysical artefacts into the system when simulating plasticity resulting from shock loading. This deficiency can be overcome only by formulating a fully time-dependent elastodynamic description of the elastic fields of discrete dislocations. Building on the work of Markenscoff & Clifton, the fundamental time-dependent solutions for the injection and non-uniform motion of straight edge dislocations are presented. The numerical implementation of these solutions for a single moving dislocation and for two annihilating dislocations in an infinite plane are presented. The application of these solutions in a two-dimensional model of time-dependent plasticity during shock loading is outlined here and will be presented in detail elsewhere.
Race CP, Mason DR, Foo MHF, et al., 2013, Quantum-classical simulations of the electronic stopping force and charge on slow heavy channelling ions in metals, JOURNAL OF PHYSICS-CONDENSED MATTER, Vol: 25, ISSN: 0953-8984
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- Citations: 16
Swinburne TD, Dudarev SL, Fitzgerald SP, et al., 2013, Theory and simulation of the diffusion of kinks on dislocations in bcc metals, PHYSICAL REVIEW B, Vol: 87, ISSN: 1098-0121
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- Citations: 53
Mason DR, Race CP, Foo MHF, et al., 2012, Resonant charging and stopping power of slow channelling atoms in a crystalline metal, NEW JOURNAL OF PHYSICS, Vol: 14, ISSN: 1367-2630
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- Citations: 15
Race CP, Mason DR, Sutton AP, 2012, A new directional model for the electronic frictional forces in molecular dynamics simulations of radiation damage in metals, JOURNAL OF NUCLEAR MATERIALS, Vol: 425, Pages: 33-40, ISSN: 0022-3115
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- Citations: 9
Broadbent RJ, Spencer JS, Livingston AG, et al., 2012, A multi-scale model for polymer membranes, EUROMEMBRANE CONFERENCE 2012, Vol: 44, Pages: 489-490, ISSN: 1877-7058
Mason DR, Race CP, Foulkes WMC, et al., 2011, Quantum mechanical simulations of electronic stopping in metals, Nucl. Instrum. Meth. Phys. Res. B, Vol: 269, Pages: 1640-1645, ISSN: 0168-583X
Race CP, Mason DR, Finnis MW, et al., 2010, The treatment of electronic excitations in atomistic models of radiation damage in metals, REPORTS ON PROGRESS IN PHYSICS, Vol: 73, ISSN: 0034-4885
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- Citations: 102
McEniry EJ, Wang Y, Dundas D, et al., 2010, Modelling non-adiabatic processes using correlated electron-ion dynamics, EUROPEAN PHYSICAL JOURNAL B, Vol: 77, Pages: 305-329, ISSN: 1434-6028
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- Citations: 28
Race CP, Mason DR, Sutton AP, 2010, An improved model of interatomic forces for large simulations of metals containing excited electrons, NEW JOURNAL OF PHYSICS, Vol: 12, ISSN: 1367-2630
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- Citations: 11
Chua AL-S, Benedek NA, Chen L, et al., 2010, A genetic algorithm for predicting the structures of interfaces in multicomponent systems, NATURE MATERIALS, Vol: 9, Pages: 418-422, ISSN: 1476-1122
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- Citations: 135
Race CP, Mason DR, le Page J, et al., 2010, Aiding the design of radiation resistant materialswith multiphysics simulations of damage processes, 2009 MRS Fall Meeting, Publisher: Cambridge University Press
von Alfthan S, Benedek NA, Chen L, et al., 2010, The Structure of Grain Boundaries in Strontium Titanate: Theory, Simulation, and Electron Microscopy, ANNUAL REVIEW OF MATERIALS RESEARCH, VOL 40, Vol: 40, Pages: 557-599, ISSN: 1531-7331
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- Citations: 43
Mason DR, Foulkes WMC, Sutton AP, 2010, A simple model for large-scale simulations of fcc metals with explicit treatment of electrons, PHILOSOPHICAL MAGAZINE LETTERS, Vol: 90, Pages: 51-60, ISSN: 0950-0839
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- Citations: 2
Bailey AG, Lowe CP, Sutton AP, 2009, REVLD: A coarse-grained model for polymers, Conference on Computational Physics (CCP 2008), Publisher: ELSEVIER SCIENCE BV, Pages: 594-599, ISSN: 0010-4655
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- Citations: 1
Race CP, Mason DR, Sutton AP, 2009, Electronic excitations and their effect on the interionic forces in simulations of radiation damage in metals, JOURNAL OF PHYSICS-CONDENSED MATTER, Vol: 21, ISSN: 0953-8984
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- Citations: 28
Bailey AG, Lowe CP, Sutton AP, 2008, Efficient constraint dynamics using MILC SHAKE, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 227, Pages: 8949-8959, ISSN: 0021-9991
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- Citations: 17
Benedek NA, Chua AL-S, Elsaesser C, et al., 2008, Interatomic potentials for strontium titanate:: An assessment of their transferability and comparison with density functional theory, PHYSICAL REVIEW B, Vol: 78, ISSN: 1098-0121
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- Citations: 70
Pruessner G, Sutton AP, 2008, Phase-field model of interfaces in single-component systems derived from classical density functional theory, PHYSICAL REVIEW B, Vol: 77, ISSN: 1098-0121
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- Citations: 4
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