Hypervelocity Impact on Pumice: Scale Effects on Experiments and Simulations

Hypervelocity tests with aluminum spheres of 1 and 1.75 inch (2.54 and 4.45 cm)-diameter impacting pumice boulders at 2.1 km/s have been performed at Southwest Research Institute. The results and analysis of the impacts are the main objective of a companion paper, while this work focuses on finding the material properties of the pumice and the computer simulations of the impact. The pumice material was tested in compression both unconfined and confined. The crush-up curve was implemented in a foam model in CTH and in the Holmquist-Johnson concrete model in EPIC. Results of the simulations like depth of penetration, crater diameter, and momentum enhancement are compared with the tests. It is found that these simple models provide reasonable results for crater depth and diameter but more work needs to be performed to properly predict the momentum enhancement, i.e. the ejecta from the pumice target.