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A multi-scale representative volume element (RVE) for simulating the mechanical behaviour of a grapheneenhanced polymer is proposed in this study. The RVE integrates nanomechanics and continuum mechanics, thus bridging the length scales from the nano-through to macro scale. The mechanical response of both armchair and zigzag graphene is described by a finite element (FE) model based on molecular mechanics. At the graphene sheet and matrix interface a simplification is introduced, perfect bonding is assumed. The C-C bonds of the graphene sheet in the analysis are described by beam elements with nodal translations and rotations in a space frame configuration, representing its atomic structure. The effect of geometric parameters of graphene platelet on the tensile response of the nanocomposite RVE is investigated. [ABSTRACT FROM AUTHOR]

The microstructure of low alloyed ferritic-martensitic Dual-Phase (DP) steels consists of hard coarse grained martensite islands embedded in a soft ferrite matrix. Therefore, the macroscopic mechanical properties of DP steels mostly derive from their microstructures, such as volume fractions, morphology of martensite, phase distributions and ferrite grain size. Recently, micromechanical approaches are used to predict ductility and failure mode of DP steels under varying mechanical loading scenarios. In this work, an artificial microstructure generator inspired by topology optimization was developed to construct representative volume element (RVE) with predefined design parameters within a mofidied Vorono¨ı tessellation. Micromechanical modeling of DP steel was performed on the generated artificial RVE. The plastic flow behavior of each single phase in DP steel were calculated by using a dislocation based theory. After numerical simulation, the flow curve on macro scale can be obtained from an asymptotic expansion homogenization (AEH) scheme. This approach allows studying the influence of individual microstructure features on local and global stress-strain response. To improve the robustness of this artificial microstructure generator, a proper orthogonal decomposition (POD) reduction was introduced to identify the optimal design parameters. This approach used a collection of artificial microstructures (snapshots) to find the most representative one of the real microstructure. [ABSTRACT FROM AUTHOR]

In paper the wire drawing processes was investigated in two levels — steady-state solve using the 2-dimensional rigid-plastic finite element method (macro-level) and modeling of a microstructure change (micro-level). In macro level the joint deformation-temperature problem was considered. In micro-level the process of deformation of representative volume element — RVE was considered. The pearlitic colony deformation and orientation of cementite lamellas change in RVE was modeled with help of a FEM. The micro-level model to rigid-plastic finite element code was implemented. The experimental data of microstructure and orientation of cementite lamellas change was compared with results of a simulations. The influence of multi-pass drawing parameters (as friction, drawing schedule) on orientation of cementite lamellas was investigated. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

PBXs are complex composites geometrically (irregularly shaped grains vary greatly in size), and constitutively (grains are anisotropic, twin and fracture). Heterogeneity at the grain scale results in localized damage and the creation of hot spots. To develop accurate, quantitative and predictive models it is imperative to develop a sound physical understanding of the grain scale material response. Numerical simulation is a useful tool to further model development. Here an inherent advantage of a particle method in discretizing geometrically complex materials is exploited to import three-dimensional material configurations from x-ray microtomography data, i.e. “real” microstructures. Numerical simulations determine representative volume element size and generate statistics on grain scale strain heterogeneity. These statistics calibrate the Stochastic Transformation Field Analysis bulk constitutive model. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]