Numerical Modelling of Shock Initiation of a HNIW‐Based Explosive

AbstractTo investigate shock‐to‐detonation transition (SDT) characteristics of a HNIW‐based explosive, a rate law based on the Forest Fire model was calibrated by conducting five wedge tests. In the wedge tests, initial shock pressure at wedge‐shaped test explosive charges was varied from 5 to 11 GPa. In each test, the shock trajectory along the wedge‐shaped explosive charge was recorded with a streak camera. The streak records showed that sharp SDT occurred in the test explosive. The shock Hugoniot of the test explosive was determined from the free‐surface velocity of PMMA attenuators measured with a VISAR instrument and the early shock velocity in the wedges, determined from the shock trajectories. The Pop plot for the test explosive was obtained from run distances to detonation estimated based on the shock trajectories. The Forest Fire rate of the test explosive was calibrated from the experimental Hugoniot and the Pop plot. The wedge tests were numerically simulated with the calibrated rate by using a one‐dimensional Lagrangian hydrodynamic code. The calculated shock trajectories closely reproduced experimental observations. The rate was further applied to two‐dimensional numerical simulations of large‐scale gap tests (LSGTs). The estimated critical gap thickness by the LSGT simulations was 43.7 mm, which was in good agreement with experimental data of 46.67 mm. The results of these two types of numerical simulations suggested that the calibrated rate could be used to model most SDT‐related applications.