A semi-discrete line-free method of monopoles for dislocation dynamics

We develop a semi-discrete particle method for Volterra dislocation currents in which the particles, or monopoles, represent an element of line and carry a Burgers vector. The monopoles move according to mobility kinetics driven by elastic and applied forces. The divergence constraint of Volterra dislocation currents is enforced weakly through mesh-free interpolation and an explicit linear connectivity, or ‘sequence’, between the monopoles need not be defined. In this sense, the method is ‘line-free’, i. e., it sidesteps the need to track dislocation lines. This attribute offers significant computational advantages in terms of simplicity, robustness and efficiency, especially as regards the tracking of complex dislocation patterns, including topological transitions. We illustrate the range and scope of the method, by means of an example of application concerned with the plastic hardening of nano-sized grains under monotonic loading

Glyph reader app: multisensory stimulation through ICT to intervene literacy disorders in the classroom

This article shows the experience in the implementation of a tool called Glyph Reader, which is an application that has two interfaces, Web and Mobile and that responds to the need for an educational and interactive resource whose main objective is the Multisensory stimulation for literacy training in a population with cognitive disabilities and/specific learning disorder. The design of the activities that this application has is based on the theoretical model of multisensory stimulation Orton Gillingham, which seeks the development of basic skills for decoding isolated words based on a phonetic - graphic analysis of them. The techniques within this model use the basic concepts of intersensory integration of simultaneous visual-auditory-kinesthetic- tactile differentiation (VAKT), to which the Glyph Reader application takes full advantage, by including graphic phonetic recognition and training activities of syllables/words (exercises with symphons and exercises with combinations of consonants or working syllables), which pass from basic levels to complex levels of decoding, necessary for the development of literacy skills. The study sample for software validation is 250 students from the Eustorgio Salgar educational institution, in the municipality of Puerto Colombia, in the department of Atlántico – Colombi

Homogenization and continuum limit of mechanical metamaterials

When used in bulk applications, mechanical metamaterials set forth a multiscale problem with many orders of magnitude in scale separation between the micro and macro scales. However, mechanical metamaterials fall outside conventional homogenization theory on account of the flexural, or bending, response of their members, including torsion. We show that homogenization theory, based on calculus of variations and notions of Gamma-convergence, can be extended to account for bending. The resulting homogenized metamaterials exhibit intrinsic generalized elasticity in the continuum limit. We illustrate these properties in specific examples including two-dimensional honeycomb and three-dimensional octet-truss metamaterials

Coupled thermoelastic simulation of nanovoid cavitation by dislocation emission at finite temperature

In this work we study the early onset of void growth by dislocation emission at finite temperature in single crystal of copper under uniaxial loading conditions using the HotQC method. The results provide a detailed characterization of the cavitation mechanism, including the geometry of the emitted dislocations, the dislocation reaction paths and attendant macroscopic quantities of interest such as the cavitation pressure. In addition, this work shows that as prismatic dislocation loops grow and move away from the void, the material surrounded by these loops is pushed away from the void surface, giving rise to a flux of material together with a heat flux through the crystal

A Line-free Method of Monopoles for 3D Dislocation Dynamics

We develop an approximation scheme for three-dimensional dislocation dynamics in which the dislocation line density is concentrated at points, or monopoles. Every monopole carries a Burgers vector and an element of line. The monopoles move according to mobility kinetics driven by elastic and applied forces. The divergence constraint, expressing the requirement that the monopoles approximate a boundary, is enforced weakly. The fundamental difference with traditional approximation schemes based on segments is that in the present approach an explicit linear connectivity, or 'sequence', between the monopoles need not be defined. Instead, the monopoles move as an unstructured point set subject to the weak divergence constraint. In this sense, the new paradigm is 'line-free', i. e., it sidesteps the need to track dislocation lines. This attribute offers significant computational advantages in terms of simplicity, robustness and efficiency, as demonstrated by means of selected numerical examples