Integrated multiscale characterization and modeling of ductile fracture in heterogeneous aluminum alloys

Ductile fracture in heterogeneous materials is strongly dependant on size, shape and distribution of heterogeneities in microstructure. Modeling mechanical response of such materials with explicit representation of microstructure morphology is computationally expensive and hence constrains the size of model. But analysis of a small microstructural model is not sufficient for prediction of fracture in a heterogeneous material. This demands the necessity of multi-scale analysis that can capture the material response over a large microstructural domain with explicit micro-mechanical analysis only in regions of dominant fracture.;Addressing various pre-requisites to multi-scale modeling, a three step Morphology based Domain Partitioning (MDP) is introduced. The first step in MDP is generating high resolution microstructure images of the entire computational domain. Subsequently, morphology based metrics are identified to relate microstructural features to mechanical response of material. In the third step, entire computational domain is partitioned to identify statistically homogeneous and inhomogeneous regions. This delineation forms the basis for macroscopic and microscopic length scales respectively, for a coupled multi-scale analysis.;The multiscale finite element model for ductile fracture developed in this work performs coupled analysis of macroscopic (level-0), and microscopic (level-2) length scales along with an intermediate swing region (level-1). The constitutive relations for macroscopic length scale are obtained by homogenization of microscopic representative volume element. Microscopic regions are analyzed with explicit representation of microstructure, using locally enhanced Voronoi Cell Finite Element Model (VCFEM) for ductile fracture. During the analysis, a macroscopic level-0 element adaptively evolves into level-1 and level-2, based on accumulation of damage. Macroscopic discretization error is minimized with h-adaptivity and modeling error is minimized by successive level change. The macroscopic and microscopic length scales are connected with an interface layer. Coupling is performed across the interface layer with Lagrange multipliers using hybrid variational formulation.;The multiscale model developed in this work captures detailed microscopic crack initiation and propagation in a large domain with minimal computational expense. The effectiveness of this multiscale characterization-modeling framework is demonstrated by studying structure-property relation and simulating ductile fracture in cast Aluminum alloy A319.