High-Speed DIC on Inside Perma-Gel During Ballistic Peneration

摘要

Perma-Gel is a melt-castable, reusable synthetic ballistic gelatin used as a soft tissue simulant in research, forensics, and shooting sports. It can also be used to study the temporary wound cavity that forms during a penetrating injury from a ballistic projectile such as a small arms bullet or a blast fragment. This cavity is typically imaged with high-speed video cameras and its measured manually in each video frame. The dynamic cavity size alone, however, does not directly provide data on the strain that material nearby, but outside of, the wound cavity is subject to. In a recent project, SwRI determined that it would be feasible to embed a dot pattern inside of the Perma-Gel block and use DIC to directly measure the strain field surrounding the wound cavity. Successfully and reliably embedding a dot pattern on a flat plane in the middle of the gel block proved to be challenging, in part because casting on top of a set layer with the pattern tended to melt the bottom layer and distort the pattern. After some modifications, a successful technique was developed. The method developed and example applications of it and the resulting DIC strain fields measured from a variety of projectiles and impact speeds are presented. The data demonstrate that DIC is an effective technique for measuring dynamic response of ballistic penetration in Perma-Gel, and can provide new insights that may be difficult or impossible to achieve with other measurement techniques.