Search results for "Polycrystalline materials"
showing 8 items of 28 documents
A computationally effective 3D Boundary Element Method for polycrystalline micromechanics
2015
An effective computational framework for homogenization and microcracking analysis of polycrystalline RVEs is presented. The method is based on a recently developed grain-boundary formulation for polycrystalline materials and several enhancements over the original technique are introduced to reduce the computational effort needed to model three-dimensional polycrystalline aggregates, which is highly desirable, especially in a multiscale perspective. First, a regularization scheme is used to remove pathological entities, usually responsible for unduly large mesh refinements, from Voronoi polycrystalline morphologies. Second, an improved meshing strategy is used, with an aim towards meshing r…
Effects of voids and flaws on the mechanical properties and on intergranular damage and fracture for polycrystalline materials
2013
It is widely recognized that the macroscopic material properties depend on the features of the microstructure. The understanding of the links between microscopic and macroscopic material properties, main topic of Micromechanics, is of relevant technological interest, as it may enable the deep understanding of the mechanisms governing materials degradation and failure. Polycrystalline materials are used in many engineering applications. Their microstructure is determined by distribution, size, morphology, anisotropy and orientation of the crystals. It worth noting that also the physical-chemical properties of the intergranular interfaces, as well as the presence of micro-imperfections within…
Computational modelling of brittle failure in polycrystalline materials using cohesive-frictional grain-boundary elements
2014
A 3D grain-level formulation for the study of brittle failure in polycrystalline microstructures is presented. The microstructure is represented as a Voronoi tessellation and the boundary element method is used to model each crystal of the aggregate. The continuity of the aggregate is enforced through suitable conditions at the intergranular interfaces. The grain-boundary model takes into account the onset and evolution of damage by means of an irreversible linear cohesive law, able to address mixed-mode failure conditions. Upon interface failure, a non-linear frictional contact analysis is introduced for addressing the contact between micro-crack surfaces. An incremental-iterative algorith…
Multiscale modeling of polycrystalline materials: A boundary element approach to material degradation and fracture
2015
Abstract In this work, a two-scale approach to degradation and failure in polycrystalline materials is proposed. The formulation involves the engineering component level (macro-scale) and the material grain level (micro-scale). The macro-continuum is modeled using a three-dimensional boundary element formulation in which the presence of damage is formulated through an initial stress approach to account for the local softening in the neighborhood of points experiencing degradation at the micro-scale. The microscopic degradation is explicitly modeled by associating Representative Volume Elements (RVEs) to relevant points of the macro continuum, for representing the polycrystalline microstruct…
A computational framework for low-cycle fatigue in polycrystalline materials
2021
Abstract A three-dimensional framework for low-cycle fatigue analysis of polycrystalline aggregates is proposed in this work. First, a cohesive law coupling plasticity and damage is developed for modelling cycle-by-cycle degradation of material interfaces up to complete de-cohesion and failure. The law may model both quasi-static degradation under increasing monotonic load and degradation under cyclic loading, through a coupled plasticity-damage model whose activation and flow rules are formulated in a thermodynamically consistent framework. The proposed interface laws have been then implemented and coupled with a multi-region boundary element formulation, with the aim of analysing low-cycl…
Modelling Polycrystalline Materials: An Overview of Three-Dimensional Grain-Scale Mechanical Models
2014
International audience; A survey of recent contributions on three-dimensional grain-scale mechanical modelling of polycrystalline materials is given in this work. The analysis of material micro-structures requires the generation of reliable micro-morphologies and affordable computational meshes as well as the description of the mechanical behavior of the elementary constituents and their interactions. The polycrystalline microstructure is characterized by the topology, morphology and crystallographic orientations of the individual grains and by the grain interfaces and microstructural defects, within the bulk grains and at the inter-granular interfaces. Their analysis has been until recentl…
A computational framework for microstructural modelling of polycrystalline materials with damage and failure
2017
In the present thesis, a computational framework for the analysis of the deformation and damage phenomena occurring at the scale of the constituent grains of polycrystalline materials is presented. The research falls within the area of Computational Micro-mechanics that has been attracting remarkable technological interest due to the capability of explaining the link between the micro-structural details of heterogenous materials and their macroscopic response, and the possibility of fine-tuning the macroscopic properties of engineered components through the manipulation of their micro-structure. However, despite the significant developments in the field of materials characterisation and the…
A Cohesive-frictional Grain-boundary Technique for Microstructural Analysis of Polycrystalline Materials
2018
The development of a 3D microstructural model for the analysis of degradation and failure in polycrystalline materials is reviewed in the present chapter. The material is explicitly modelled at the grain level, using integral equations in conjunction with a phenomenological crystal plasticity framework for the bulk grains, and with cohesive-frictional laws to represent inter-granular micro-cracking processes. The method allows to capture the initiation, development and coalescence of damage or plasticity at the aggregate scale. The formulation’s key feature is the representation of the mechanical problem in terms of inter-granular variables only, which allows to reduce the computational cos…