Representative elementary volume

About: Representative elementary volume is a research topic. Over the lifetime, 4105 publications have been published within this topic receiving 86863 citations.

Elastic Properties of Open-Cell Foams with Tetrakaidecahedral Cells Using Finite Element Analysis

Abstract: A finite-element-method-based micromechanics has been used for predicting the orthotropic properties of open-cell foams that have tetrakaidecahedral unit cells. Foams with equisided and Kelvin-elongated tetrakaidecahedron as unit cells are studied. The results for elastic constants from the finite element models agree well with those of available analytical models. The struts were modeled using both Euler-Bernoulli and Timoshenko beam elements. It is found that classical beam theory overpredicts the elastic moduli when the struts have smaller length-to-thickness ratios. The effect of varying strut cross section on the elastic constants is studied. The variation is assumed to be such that the strut cross section gradually decreases from maximum value at the support ends to minimum value at the beam midsection. It is found that for the same relative density, foams with varying cross sections have much lower elastic moduli than foams with uniform cross sections.

Numerically-aided 3D printed random isotropic porous materials approaching the Hashin-Shtrikman bounds

Abstract: The present study introduces a methodology that allows to combine 3D printing, experimental testing, numerical and analytical modeling to create random closed-cell porous materials with statistically controlled and isotropic overall elastic properties that are extremely close to the relevant Hashin-Shtrikman bounds. In this first study, we focus our experimental and 3D printing efforts to isotropic random microstructures consisting of single-sized (i.e. monodisperse) spherical voids embedded in a homogeneous solid matrix. The 3D printed specimens are realized by use of the random sequential adsorption method. A detailed FE numerical study allows to define a cubic representative volume element (RVE) by combined periodic and kinematically uniform (i.e. average strain or affine) boundary conditions. The resulting cubic RVE is subsequently assembled to form a standard dog-bone uniaxial tension specimen, which is 3D printed by use of a photopolymeric resin material. The specimens are then tested at relatively small strains by a proper multi-step relaxation procedure to obtain the effective elastic properties of the porous specimens.

Representative volume element model of lithium-ion battery electrodes based on X-ray nano-tomography

Abstract: A new model that keeps all major advantages of the single-particle model of lithium-ion batteries (LIBs) and includes three-dimensional structure of the electrode was developed. Unlike the single spherical particle, this model considers a small volume element of an electrode, called the representative volume element (RVE), which represents the real electrode structure. The advantages of using RVE as the model geometry were demonstrated for a typical LIB electrode consisting of nano-particle LiFePO4 (LFP) active material. The three-dimensional morphology of the LFP electrode was reconstructed using a synchrotron X-ray nano-computed tomography at the Advanced Photon Source of the Argonne National. A 27 μm3 cube from reconstructed structure was chosen as the RVE for the simulation purposes. The model was employed to predict the voltage curve in a half-cell during galvanostatic operations and validated with experimental data. The simulation results showed that the distribution of lithium inside the electrode microstructure is very different from the results obtained based on the single-particle model. The range of lithium concentration is found to be much greater, successfully illustrating the effect of microstructure heterogeneity.