Search results for " Micromechanics"
showing 10 items of 15 documents
Intergranular damage and fracture in polycrystalline materials. A novel 3D microstructural grain-boundary formulation
2013
The design of advanced materials requires a deep understanding of degradation and failure pro- cesses. It is widely recognized that the macroscopic material properties depend on the features of the microstructure. The knowledge of this link, which is the main subject of Micromechanics [1], is of relevant technological interest, as it may enable the design of materials with specific requirements by means of suitable manipulations of the microstructure. Polycrystalline materials are used in many technological applications. Their microstructure is characterized by the grains morphology, size distribution, anisotropy, crystallographic orientation, stiffness and toughness mismatch and by the phy…
A multiscale approach to polycrystalline materials damage and failure
2015
A two-scale three-dimensional approach for degradation and failure in polycrystalline materials is presented. The method involves the component level and the grain scale. The damageinduced softening at the macroscale is modelled employing an initial stress boundary element approach. The microscopic degradation is explicitly modelled associating Representative Volume Elements (RVEs) to relevant points of the macro continuum and employing a cohesive-frictional 3D grain-boundary formulation to simulate intergranular degradation and failure in the Voronoi morphology. Macro-strains are downscaled as RVEs' periodic boundary conditions, while overall macro-stresses are obtained upscaling the micro…
Porosity effects on elastic properties of polycrystalline materials: a three-dimensional grain boundary formulation
2013
Polycrystalline materials are widely used in many technological applications of engineering interest. They constitute an important class of heterogeneous materials, and the investigation of the link between their macro and micro properties, main task of the micromechanics [1], is of relevant technological concern. The internal structure of a polycrystalline material is determined by the size and the shape of the grains, by their crystallographic orientation and by different type of defects within them. In this sense, the presence of internal voids, pores, is important to take into account in the determination of the polycrystalline aggregate properties. Porosity exists in almost all materia…
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…
Polycrystalline materials with pores: effective properties through a boundary element homogenization scheme
2014
In this study, the influence of porosity on the elastic effective properties of polycrystalline materials is investigated using a formulation built on a boundary integral representation of the elastic problem for the grains, which are modeled as 3D linearly elastic orthotropic domains with arbitrary spatial orientation. The artificial polycrystalline morphology is represented using 3D Voronoi tessellations. The formulation is expressed in terms of intergranular fields, namely displacements and tractions that play an important role in polycrystalline micromechanics. The continuity of the aggregate is enforced through suitable intergranular conditions. The effective material properties are ob…
A BOUNDARY ELEMENT FORMULATION FOR MICROMECHANICAL HOMOGENIZATION OF POLYCRYSTALLINE MATERIALS WITH PIEZOELECTRIC COUPLING
2019
A novel boundary element formulation for the evaluation of the effective properties of threedimensional polycrystalline aggregates with piezoelectric coupling is presented. The aggregates are modelled at the scale of their constituent crystals and are artificially generated through Voronoi-Laguerre tessellations. The electro-mechanical behaviour of each crystal is represented upon introducing an ad-hoc mesh of its boundary and a generalised integral representation of the governing equations of the piezoelectric problem. The behaviour of the whole aggregate is then retrieved upon introducing a suitable set of electro-mechanical interface conditions at the grain boundaries. With respect to cl…
Toward high performance renewable agave reinforced biocomposites: Optimization of fiber performance and fiber-matrix adhesion analysis
2017
Abstract The increasing sensitivity toward the environmental pollution and the recent laws on the environmental protection, have led to an increasing attention to the so called biocomposites, i.e. to ecofriendly or renewable composite materials, obtained from biopolymers reinforced by natural fibers. Although the contribution of various works reported in literature, focused on biocomposites reinforced by agave fibers, such materials are still exclusively used in the automotive industry for non-structural applications, and the implementation of high performance biocomposites for semi-structural and structural applications, is an expected, but not yet reached objective. Therefore, the present…
Elucidating the Effect of Bimodal Grain Size Distribution on Plasticity and Fracture Behavior of Polycrystalline Materials
2020
The refinement of grains in a polycrystalline material leads to an increase in strength but as a counterpart to a decrease in elongation to fracture. Different routes are proposed in the literature to try to overpass this strength-ductility dilemma, based on the combination of grains with highly contrasted sizes. In the simplest concept, coarse grains are used to provide relaxation locations for the highly stressed fine grains. In this work, a model bimodal polycrystalline system with a single coarse grain embedded in a matrix of fine grains is considered. Numerical full-field micro-mechanical analyses are performed to characterize the impact of this coarse grain on the stress-strain const…
A Microstructural Model for Micro-Cracking in Piezoceramics
2018
Piezoelectric ceramics are employed in several applications for their capability to couple mechanical and electrical fields, which can be advantageously exploited for the implementation of smart functionalities. The electromechanical coupling, which can be employed for fast accurate micro-positioning devices, makes such materials suitable for application in micro electromechanical systems (MEMS). However, due to their brittleness, piezoceramics can develop damage leading to initiation of micro-cracks, affecting the performance of the material in general and the micro-devices in particular. For such reasons, the development of accurate and robust numerical tools is an important asset for the…
A three-dimensional cohesive-frictional grain-boundary micromechanical model for intergranular degradation and failure in polycrystalline materials
2013
Abstract In this study, a novel three-dimensional micro-mechanical crystal-level model for the analysis of intergranular degradation and failure in polycrystalline materials is presented. The polycrystalline microstructures are generated as Voronoi tessellations, that are able to retain the main statistical features of polycrystalline aggregates. The formulation is based on a grain-boundary integral representation of the elastic problem for the aggregate crystals, that are modeled as three-dimensional anisotropic elastic domains with random orientation in the three-dimensional space. The boundary integral representation involves only intergranular variables, namely interface displacement di…