No abstract

This paper is dedicated to Gilles Canova, who initiated and participated in the development of the numerical simulations presented in this paper.

Note: The following files were submitted by the author for peer review, but cannot be converted to PDF. You must view these files (e.g. movies) online. Climb_basic3D_final.tex climb_PhilMag.bib philmag.bst rotating.sty tPHM2e.cls upmath.sty http://mc.manuscriptcentral.com/pm-pml

We employ a discrete computational model to study the entanglement transition of non-cross-linked semiflexible fibers during isostatic compressions. We determine, as a function of the fiber aspect ratio, packing densities and caging numbers, i.e., the density and number of contacts per fiber at the entanglement transition. The caging number is found to be 8 for short fibers and to drop down to 4 for longer fibers. Compressions beyond the entanglement transition allow us to determine, for these networks that deform primarily by bending, the scaling exponents of the pressure and of the bulk modulus (=3), as well as of the number of contacts per fiber (=1).

A three-dimensional (3D) dislocation simulation has been developed in the last few years in order to fill the gap between atomistic simulations and the more macroscopic approaches. The specific role of such a simulation is to combine all mechanisms responsible for the hardening (e.g. the forest mechanism) and the multiplication of dislocations which typically occur in three dimensions.Many problems involve the presence of interfaces, which can come from cracks, oxide layers, particles etc. The present work deals with a method to tackle such problems in a 3D simulation. It is firstly restricted to the image stress case. A method of calculating the image stress field of dislocation segments due to the presence of a semi-infinite free surface has been proposed by Gosling and Willis. An alternative method is proposed here based on the Boussinesq problem of point loading in a half-space. It is firstly shown on simple cases that the methods are equivalent. The latter one is used in the present simulation, and the image stress field due to populations of dislocations is investigated. From a practical point of view, we calculate the depths within which all dislocations have to be taken into account, in order to get reasonable accuracy on the image stresses, and we also investigate how this stress field decays in space.

No abstract

No abstract

No abstract