Quantitative Imaging of Shock-driven Pore Collapse: Deformation, Failure, and Interaction Mechanics

Porous materials are prevalent in engineering, with applications in structural and energetic materials, spanning length scales of microns to millimeters. Pores are linked to failure and localization phenomena, especially under shock loading conditions, where the pores rapidly collapse, leading to large deformations. In structural materials, failure occurs due to stress concentrations generated by pores, and pore collapse in energetic materials may cause mechanically-induced hot spots.

Until now, experimental investigation of pore collapse has been limited to continuum measurements, observations of pore shape evolution, and post-mortem analysis of failure and localization. In this study, we develop a technique to enable internal, full-field strain measurements during shock compression experiments. Target specimens are fabricated with internal spherical pores and speckle pattern for digital image correlation (DIC), and impacted by a flyer plate to generate a controlled, planar shock which induces pore collapse. High speed imaging and DIC enable time-resolved strain measurements around the pore and analysis of the pore shape evolution.

Experiments on a single pore reveal the development of self-organized adiabatic shear bands around the pore, and a transition, at higher pressures, to shear fracture. Further, the interaction of multiple pores is investigated in various configurations. Finally, the results are further analyzed through comparison to elastic theory and numerical modeling.