A. A. Benzerga | Searcharxiv

arXiv2026

An assessment of mechanism-based plasticity models for polycrystalline magnesium alloys

The objective of this work is to assess computationally efficient coarse-grained plasticity models against high-fidelity crystal plasticity simulations for magnesium polycrystals over a wide range of textures and grain sizes. A basic requirement is that such models are able to capture {\it evolving} plastic anisotropy and tension-compression asymmetry. To this end, two-surface and three-surface plasticity models are considered. The two-surface constitutive formulation separately accounts for slip and twinning, while the three-surface model further apportions the contributions of basal and nonbasal slip. Model identification is based on stress-strain responses for loading along six orientations under both tension and compression. The evolution of overall plastic anisotropy, as well as microscale relative activities of slip and twin systems, is analyzed in detail. The prospects of using coarse-grained plasticity models in guiding the development of physically sound damage models for magnesium alloys are discussed.

cond-mat.mtrl-sci↗

arXiv2024

A discrete dislocation analysis of size-dependent plasticity in torsion

A method for solving three dimensional discrete dislocation plasticity boundary-value problems using a monopole representation of the dislocations is presented. At each time step, the displacement, strain and stress fields in a finite body are obtained by superposition of infinite body dislocation fields and an image field that enforces the boundary conditions. The three dimensional infinite body fields are obtained by representing dislocations as being comprised of points, termed monopoles, that carry dislocation line and Burgers vector information. The image fields are obtained from a three dimensional linear elastic finite element calculation. The implementation of the coupling of the monopole representation with the finite element method, including the interaction of curved dislocations with free surfaces, is presented in some detail because it differs significantly from an implementation with a line based dislocation representation. Numerical convergence and the modeling of dislocation loop nucleation for large scale computations are investigated. The monopole discrete dislocation plasticity framework is used to investigate the effect of size and initial dislocation density on the torsion of wires with diameters varying over three orders of magnitude. Depending on the initial dislocation source density and the wire diameter, three regimes of torsion-twist response are obtained: (i) for wires with a sufficiently small diameter, plastic deformation is nucleation controlled and is strongly size dependent; (ii) for wires with larger diameters dislocation plasticity is dislocation interaction controlled, with the emergence of geometrically necessary dislocations and dislocation pile-ups playing a key role, and is strongly size dependent; and (iii) for wires with sufficiently large diameters plastic deformation becomes less heterogeneous and the dependence on size is greatly diminished.

cs.CE↗