Using the SURF Model to Simulate Fragment Impact on Energetic Materials

Abstract

The Scaled Uniform Reactive Front (SURF) model developed by Menikoff and Shaw (Comb. Theory Model., 2012) is a High Explosive (HE) reactive burn model. It has been shown to accurately model plate impact shock experiments while requiring only a minimal number of calibration parameters. We have implemented SURF into the Eulerian code Pagosa. SURF has been shown to suitably model high-speed impact and accurately capture the entire Shock-to-Detonation Transition (SDT) process. SURF is also able to model short shocks and dead zones, critical for finite sized impactors such those used in fragment impact investigations. Many burn models cannot do this. The success of SURF is derived from it being based on the physics of hotspots, triggered by the leading shock, and thus can naturally account for properties like shock desensitization. SURF needs to be calibrated for each explosive modeled and for that we use plate impact experiments. For the three explosives considered in this work, PBX 9501, PBX 9502 and Composition B, we use the data of Gustavsen and Dattelbaum (Embedded electromagnetic gauge measurements and modeling of shock initiation in the TATB based explosives PBX 9502 and LX-17. LA-UR-01-3339). After discussing the model, its calibration, we apply SURF to model fragment impact experiments where the effects of release waves originating from finite sized impactors is critical. For example, we use SURF to investigate fragment impact on PBX9502, diagnosed using high speed photography, to support our numerical study of the effect of lateral and back surface release wave on the detonation process. SURF is also applied to successfully model ball impact on the explosive PBX 9501. These successes support the notion that SURF is a reliable tool for modeling impacted explosives.