The Novel “Fracture” Gun at the DEVCOM Army Research Laboratory for Precise, Highly Instrumented Impact Experiments

Abstract

This paper describes the novel “fracture” gun recently built at the US Army Research Laboratory (ARL) to study dynamic deformation and fracture mechanisms under impact loading using high-speed cameras with DIC. This gun combines the precise projectile/target alignment capabilities typical of a plate impact experiment with the ability to observe phenomena over wide spatial and temporal scales. The velocity capabilities and the target tank will be outlined. The target tank is small with large windows, so that cameras can be placed very close to the impact location which allows for small fields of view that are not typically achievable in these experiments. Velocity measurement, triggering, and lighting solutions will be presented. Of special concern are the DIC errors that develop when imaging through a window that distorts due to a vacuum being pulled in the target chamber; these errors have been quantified. There are very few experimental methods to probe fundamental deformation and fracture mechanisms within the ballistic regime, but this gun and the associated instrumentation are a big step toward better understanding these mechanisms.