Material Characterization and Microstructural Simulation of Hollow Sphere Steel Foam

The objective of this research is to characterize the mechanical properties of hollow spheres and PCM steel foams under compressive and tensile loading, and to develop and validate microstructural computational models for such foams that account for micro-scale buckling of the cell walls and localized material yielding. Such models allow the virtual investigation of the relationship between microstructural design parameters and macroscopic material properties. Steel foams are a new class of structural materials that have the potential to provide enhanced energy dissipation, stiffness, and buckling mitigation by virtue of their unusual mechanical properties. Through physical experiments we characterize some previously unreported properties of the material such as the compressive unloading modulus and its evolution with increasing plastic deformation, the Poisson’s ratio of the material in the plastic range, and the tensile yield and fracture strengths. Our three dimensional finite element models are among the first to treat the material microstructure as random while incorporating both material and geometric nonlinearity at the micro-scale. The experimental characterization of the material properties feeds directly into work being performed to develop candidate applications of steel foam in civil structures, and the computational work is being used to suggest novel microstructural designs that lead to improved macroscopic material properties.

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