Compression behavior of individual thin-walled metallic hollow spheres with patterned distributions of microporosity

This paper presents an integrated experimental and computational study of the compression behavior of individual thin-walled metallic hollow spheres (MHS) with patterned distributions of microporosity. Quasi-static compression testing, including purely elastic loading, was conducted on two groups of individual MHS with two different sizes to examine the entire deformation process as well as the purely elastic response. Three-dimensional finite element modeling was then performed to investigate the effects of different microporosity distribution patterns on the MHS compression behavior and to understand the pertinent deformation and failure mechanisms. Results show that the Young's modulus and collapse stress of individual MHS with a uniform microporosity distribution decrease nonlinearly with porosity, which follows the same power-law functions developed for the porous wall material. For other patterned (i.e., vertical, horizontal, and random) distributions of microporosity involving localized weak wall sections, buckling commences at the weak sections, generating "buckling lines", followed by buckling failure along these adjacent or converged "buckling lines". Moreover, among the "buckling lines" generate some hinges that contribute to the increased load-bearing capability during the densification process. These findings can shed lights on the design, manufacturing, and modeling of individual MHS and MHS-based materials with specifically tailored engineering performance.