I have a post-doc position for up to 28 months at Imperial College London, working on dislocation mechanics modelling for problems in nuclear materials, advert snippet below, full advert and application from the link below. Closing date 30th October 2019, starting as soon as possible, at least within the next 6 months.
A demonstration through an example is given of how the Volterra dislocation formulation in linear elasticity can be viewed as a (formal) limit of a problem in plasticity theory. Interestingly, from this point of view the Volterra dislocation formulation with discontinuous displacement, and non-square-integrable energy appears as a large-length scale limit of a smoother microscopic problem. This is in contrast to other formulations using SBV functions as well as the theory of Structured deformations where the microscopic problem is viewed as discontinuous and the smoother plasticity formulation appears as a homogenized large length-scale limit.
(To appear in Journal of Elasticity).
Title of the project: Ab initio modelling of interactions between dislocations and solutes in body-centered cubic metals
Research area: Solid State Physics, Materials Science
Summary of the project:
Amit Acharya
(in Journal of Elasticity)
The kinematic theory of Weingarten-Volterra line defects is revisited, both at small and fi nite deformations. Existing results are clari fied and corrected as needed, and new results are obtained. The primary focus is to understand the relationship between the disclination strength and Burgers vector of deformations containing a Weingarten-Volterra defect corresponding to di fferent cut-surfaces.
Given a distribution of defects on a structured surface, such as those represented by 2-dimensional crystalline materials, liquid crystalline surfaces, and thin sandwiched shells, what is the resulting stress field and the deformed shape? Motivated by this concern, we first classify, and quantify, the translational, rotational, and metrical defects allowable over a broad class of structured surfaces. With an appropriate notion of strain, the defect densities are then shown to appear as sources of strain incompatibility.
Chiqun Zhang Amit Acharya
The utility of the notion of generalized disclinations in materials science is discussed within the physical context of modeling interfacial and bulk line defects like defected grain and phase boundaries, dislocations and disclinations. The Burgers vector of a disclination dipole in linear elasticity is derived, clearly demonstrating the equivalence of its stress field to that of an edge dislocation. We also prove that the inverse deformation/displacement jump of a defect line is independent of the cut-surface when its g.disclination strength vanishes. An explicit formula for the displacement jump of a single localized composite defect line in terms of given g.disclination and dislocation strengths is deduced based on the Weingarten theorem for g.disclination theory at finite deformation. The Burgers vector of a g.disclination dipole at finite deformation is also derived.
Short course at Centre International de Sciences Mechanique (CISM), Udine.
May 22-26, 2017
Lecturers: S Forest, I Groma, D McDowell, S Mesarovic, J-N Roux, H Zbib
The flyer is attached. Register at: http://www.cism.it/courses/C1703/
Summary
Akanksha Garg, Craig Maloney
(accepted mannuscript in Journal of Mechanics and Physics of Solids)
Amit Acharya Michael Widom
To appear in Journal of the Mechanics and Physics of Solids
Motivated by results of the topological theory of glasses accounting for geometric frustration,
we develop the simplest possible continuum mechanical model of defect dynamics in metallic
glasses that accounts for topological, energetic, and kinetic ideas. A geometrical description
of ingredients of the structure of metallic glasses using the concept of local order based on
Frank-Kasper phases and the notion of disclinations as topological defects in these structures is
proposed. This novel kinematics is incorporated in a continuum mechanical framework capable
of describing the interactions of disclinations and also of dislocations (interpreted as pairs of
opposite disclinations). The model is aimed towards the development of a microscopic understanding
of the plasticity of such materials. We discuss the expected predictive capabilities of
the model vis-a-vis some observed physical behaviors of metallic glasses.
