Micro-spalling of metal under explosive loading

Spallation process of melted metal on release or shock attracts considerable attention for basic weapon physics studies and engineering applications. In the present study, numerous cavitations within the shocked metal were initiated to induce the liquid fragments, defined as the micro-spall, revealing discrete and quasi-continuous spatial distributions, validated by proton radiography experiments. Here we improved the traditional Asay-window technique by attaching a thin LiF layer on the impacted plate of the LiF window and contriving a diffuse reflection interface. With these two optimized design, we successfully detected high-quality signals of micro-spalling fragments. Combining the medium-energy X-ray with the DPS diagnostic technique, we obtained clear volume-density distributions and evolution character for micro-spalling productions of melting Sn at different moments. We found the semiquantitative findings among the two tools are in good agreement. These clear images provide convinced experimental evidences for understanding the mechanism of the micro-spalling phenomenon and also offer useful data for theoretical modeling.