Intergranular damage and fracture in polycrystalline materials. A novel 3D microstructural grain-boundary formulation

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Abstract

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 featuresof 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 specificrequirements by means of suitable manipulations of the microstructure.Polycrystalline materials are used in many technological applications. Their microstructure ischaracterized by the grains morphology, size distribution, anisotropy, crystallographic orientation,stiffness and toughness mismatch and by the physical-chemical properties of the intergranularinterfaces. These aspects have a direct influence on the initiation and evolution of micro-damage,which is also sensitive to the presence of micro-imperfections. Any theory trying to explain thefailure mechanisms in these materials must then accommodate a relevant number of parameters.In this study, a novel 3D grain-boundary micro-mechanical model for the analysis of intergranulardegradation and failure in polycrystalline materials is presented. The microstructure is generatedby means of Voronoi tessellations, able to retain the main statistical features of polycrystals. Theformulation is built on a boundary integral representation of the elastic problem for the crystals,that are modeled as 3D anisotropic elastic domains with arbitrary orientation [2]. This representa-tion involves only mechanical variables at the grains interfaces, i.e. displacement jumps and trac-tions, that play an important role in the micromechanics of polycrystals. The aggregate integrityis restored by enforcing suitable intergranular conditions. The onset and evolution of intergranulardamage is modeled using an extrinsic irreversible cohesive law, able to address mixed-mode fail-ure conditions. Upon interface failure, a non-linear frictional contact analysis is used, to addressseparation, sliding or sticking between the formed micro-crack surfaces. The incremental-iterativealgorithm for tracking the micro-evolution is presented. Several numerical tests on pseudo andfully three-dimensional microstructures are discussed. The present formulation is a promising toolin the framework of multiscale analysis of degradation and failure in polycrystalline materials.
Lingua originaleEnglish
Numero di pagine1
Stato di pubblicazionePublished - 2013

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