On the correspondence between a screw dislocation in gradient elasticity and a regularized vortex

We show the correspondence between a screw dislocation in gradient elasticity and a regularized vortex. The effective Burgers vector, nonsingular distortion and stress fields of a screw dislocation and the effective circulation, smoothed velocity and momentum of a vortex are given and discussed.Comment: 6 pages, 2 figure

Twist disclination in the field theory of elastoplasticity

In this paper we study the twist disclination within the elastoplastic defect theory. Using the stress function method, we found exact analytical solutions for all characteristic fields of a straight twist disclination in an infinitely extended linear isotropic medium. The elastic stress, elastic strain and displacement have no singularities at the disclination line. We found modified stress functions for the twist disclination. In addition, we calculate the disclination density, effective Frank vector, disclination torsion and effective Burgers vector of a straight twist disclination. By means of gauge theory of defects we decompose the elastic distortion into the translational and rotational gauge fields of the straight twist disclination.Comment: 21 pages, 4 figure

The fundamentals of non-singular dislocations in the theory of gradient elasticity: dislocation loops and straight dislocations

The fundamental problem of non-singular dislocations in the framework of the theory of gradient elasticity is presented in this work. Gradient elasticity of Helmholtz type and bi-Helmholtz type are used. A general theory of non-singular dislocations is developed for linearly elastic, infinitely extended, homogeneous, and isotropic media. Dislocation loops and straight dislocations are investigated. Using the theory of gradient elasticity, the non-singular fields which are produced by arbitrary dislocation loops are given. `Modified' Mura, Peach-Koehler, and Burgers formulae are presented in the framework of gradient elasticity theory. These formulae are given in terms of an elementary function, which regularizes the classical expressions, obtained from the Green tensor of the Helmholtz-Navier equation and bi-Helmholtz-Navier equation. Using the mathematical method of Green's functions and the Fourier transform, exact, analytical, and non-singular solutions were found. The obtained dislocation fields are non-singular due to the regularization of the classical singular fields.Comment: 29 pages, to appear in: International Journal of Solids and Structure

On the fundamentals of the three-dimensional translation gauge theory of dislocations

We propose a dynamic version of the three-dimensional translation gauge theory of dislocations. In our approach, we use the notions of the dislocation density and dislocation current tensors as translational field strengths and the corresponding response quantities (pseudomoment stress, dislocation momentum flux). We derive a closed system of field equations in a very elegant quasi-Maxwellian form as equations of motion for dislocations. In this framework, the dynamical Peach-Koehler force density is derived as well. Finally, the similarities and the differences between the Maxwell field theory and the dislocation gauge theory are presented.Comment: 17 pages, to appear in: Mathematics and Mechanics of Solid

Screw dislocations in the field theory of elastoplasticity

A (microscopic) static elastoplastic field theory of dislocations with moment and force stresses is considered. The relationship between the moment stress and the Nye tensor is used for the dislocation Lagrangian. We discuss the stress field of an infinitely long screw dislocation in a cylinder, a dipole of screw dislocations and a coaxial screw dislocation in a finite cylinder. The stress fields have no singularities in the dislocation core and they are modified in the core due to the presence of localized moment stress. Additionally, we calculated the elastoplastic energies for the screw dislocation in a cylinder and the coaxial screw dislocation. For the coaxial screw dislocation we find a modified formula for the so-called Eshelby twist which depends on a specific intrinsic material length.Comment: 19 pages, LaTeX, 2 figures, Extended version of a contribution to the symposium on "Structured Media'' dedicated to the memory of Professor Ekkehart Kr\"oner, 16-21 September 2001, Pozna\'n, Poland. to appear in Annalen der Physik 11 (2002

On the non-uniform motion of dislocations: The retarded elastic fields, the retarded dislocation tensor potentials and the Li\'enard-Wiechert tensor potentials

The purpose of this paper is the fundamental theory of the non-uniform motion of dislocations in two and three space-dimensions. We investigate the non-uniform motion of an arbitrary distribution of dislocations, a dislocation loop and straight dislocations in infinite media using the theory of incompatible elastodynamics. The equations of motion are derived for non-uniformly moving dislocations. The retarded elastic fields produced by a distribution of dislocations and the retarded dislocation tensor potentials are determined. New fundamental key-formulae for the dynamics of dislocations are derived (Jefimenko type and Heaviside-Feynman type equations of dislocations). In addition, exact closed-form solutions of the elastic fields produced by a dislocation loop are calculated as retarded line integral expressions for subsonic motion. The fields of the elastic velocity and elastic distortion surrounding the arbitrarily moving dislocation loop are given explicitly in terms of the so-called three-dimensional elastodynamic Li\'enard-Wiechert tensor potentials. The two-dimensional elastodynamic Li\'enard-Wiechert tensor potentials and the near-field approximation of the elastic fields for straight dislocations are calculated. The singularities of the near-fields of accelerating screw and edge dislocations are determined.Comment: 31 pages, to appear in: Philosophical Magazin