A full-field crystal-plasticity analysis of bimodal polycrystals

Abstract

A full field crystal plasticity modelling of bimodal polycrystals is presented. Bimodal polycrystals are generated using a controlled Laguerre-Voronoi algorithm and a modified phenomenological law is used to take into account the grain size effect through a Hall-Petch term. A focus is particularly made on the effects of grain size and of grain size ratio between ultrafine grains and coarse grains populations on local and global mechanical responses. The effect of the spatial distribution of the coarse grains (clustered or isolated) is also analysed in terms of strain localisation and stress concentration at the local scale.

Generating polycrystalline microstructures with prescribed tensorial texture coefficients

“…As orientation assignment is typically treated as a post-processing step in microstructure generation, it is possible to couple the proposed algorithm with well-established microstructure generators [21][22][23]. With this modular structure, it is possible to use TOP for generating polycrystalline representations for a variety of applications [94,95]. As an additional benefit, for generating orientations, the TOP method requires only nine (or 22 variables, depending on the highest texture coefficient rank considered) to be stored, contrasting with methods that rely on the entire experimental database.…”

Elucidating the Effect of Bimodal Grain Size Distribution on Plasticity and Fracture Behavior of Polycrystalline Materials

“…As illustrated by EBSD scans presented therein, CG are commonly observed to be embedded in the matrix of FG as isolated inclusions. Previous numerical analyses [20] have shown that in such a configuration of isolated CG, a domain containing at least 9 CG should be considered to obtain quantitatively representative macroscopic properties; yet a 2D domain containing a single CG could provide qualitativaly representative properties, especially for the analyses of local CG-FG interactions. This is the retained configuration of study in this paper, also motivated by the reduction in computational resources and the comfort of analysis it provides.…”

“…for CG and FG families and a unimodal microstructure containing 256 grains and with a mean GS corresponding to either CG or FG. They result from Laguerre-Voronoi tessellations with specific settings on the nucleation and growth processes [20,23]. The Neper software was used to generate these microstructure and to obtain the finite elements meshes [24,25].…”

“…All the material parameters have been identified on the basis of experimental tensile stress-strain curves of the considered 316L steel elaborated by spark plasma sintering, for different mean GS of unimodal polycrystals. It is worth noting that the Hall-Petch dependence introduced in the slip system scale results also in a Hall-Petch dependence of the macroscopic scale of a unimodal polycrystal [20].…”

“…Some of these proposals rely on mean field hypotheses of self-consistent homogenization approaches [15,16,17] or on the idealization of a GS population as a homogeneous phase [18], or are restricted to the early stages of plastic deformation [19]. In the study [20], a comprehensive presentation of a full field crystal plasticity modelling applied to bimodal polycrystals has been provided. Yet, although this modelling approach provides a very fine description of the elastoplastic mechanisms originally taking place in a bimodal polycrystal, its applicability is restricted to crystal plasticity.…”