Capturing early fragment dynamics in dense explosion clouds

Abstract

Accurate measurement of initial fragment velocities is critical for characterizing dispersion and shocked fragment interactions inside the explosion cloud. Conventional techniques yield only time-averaged data, missing early-stage dynamics inside harsh explosive environments. This study employs Digital Inline Holography (DIH) with sub-µs exposure to track early-stage dynamics of preformed fragments in single- and three-fragment configurations using two electric detonators, Det-1 and Det-2, with different explosive masses. Despite its higher explosive mass, Det-1 produced lower fragment velocities than Det-2 due to higher energy absorption through deformation and fracture. In the three-fragment inline setup, the outermost fragment consistently attained the highest velocity, driven by shock transmission. The fragments showed significant deceleration due to increased density inside the cloud in both detonator configurations. Energy absorbed in fragment deformation was analyzed using SEM and XRD. Results showed that fragments from Det-1 absorbed more energy, resulting in lower initial velocities. A velocity decay model, incorporating effective density and drag, supported experimental trends. Overall, this study provides continuous time-resolved fragment velocity characterization in harsh explosive environments, offering critical insights into shock–fragment interactions, energy partitioning, and preformed fragmentation behaviour. © 2026 Elsevier Ltd