Indirect Determination of Material Properties of Closed-Cell Metal Foam: Comparison of Voxel and Tetrahedral Finite Element Models

Abstract

In this paper a comprehensive evaluation of the microstructural finite element (microFE) models of closed-cell aluminum metal foam is given. Comparison of models developed using high resolution three-dimensional image data obtained using microtomographic scanning of a sample with different resolutions is presented. Two sets of micro-finite element models are prepared using the same image data: i) voxel finite element models in which every 3-D pixel (voxel) is directly converted to one hexahedral element and ii) tetrahedral finite element models which are prepared by filling a triangular surface mesh of the foam’s microstructure. A virtual uni-axial compression test is simulated in three mutually perpendicular directions to obtain the elastic moduli and the maximum values of the principal stresses as well as to quantify the anisotropy of the back-calculated material characteristics. The material model used in the finite element simulations is based on previously published results obtained from an experimental-numerical study of the base material used for production of the reference foam. The elastic constants acquired from the finite element simulations of the most detailed models are in good agreement with the experimental results provided that the overall porosity of the material is well represented by the finite element models. The requirements in terms of the minimal spatial resolution of the microtomographic images needed for proper estimation of elastic properties of a closed-cell metal foams are given. The superiority of the voxel finite element models over the tetrahedral models is clearly demonstrated in the paper. The results obtained using tetrahedral finite element models at the lower resolution are poor compared with results obtained from the voxel models with the same resolution.