Shock-driven Metal Foams for Studying Shallow Bubble Collapse

Study of shock-driven ejecta has historically focused on Richtmeyer-Meshkov instability (RMI) growth as the primary mechanism, but a fundamentally different method, termed Shallow Bubble Collapse (SBC), has recently been established. SBC describes the process by which a release after a shock forms cavitation bubbles directly beneath the surface, and a subsequent shock collapses these bubbles. This releases significantly more ejecta than the RMI mechanism. In this work, the cavitation bubble collapse and ejecta release process is isolated by shocking a porous aluminum foam with a strong single shock. This simplified problem allows for more control over the sample and shock conditions, while also enabling better diagnostic access. Results are compared for differences in pore size, morphology, and pore fraction in the foam. These experiments, supported by numerical simulation, have shown this method accurately reproduces the physical processes taking place in SBC, therefore enabling faster model development.