Ejecta are particles ejected from a material's surface following the release of an extreme shock compression state. These high-velocity ballistic particulates can inform additive manufacturing (AM) as impact-induced adhesion can have many positive benefits in AM technologies (Cormier et al. 2016) and cold spray applications (Assadi et al. 2016) via the buildup of layers of microparticles. However, production and collision of micron-sized ejecta at velocities of ~1 km/s are difficult phenomena to study experimentally due to the small time and length scales involved. Other large-scale ejecta source experiments have high costs due to the vast amount of high explosive (HE) required, typically 10–100 grams (Monfared et al. 2014). This expensive and destructive testing requires long reset times and ultimately yields few precision measurements. Therefore, a safe-to-use ejecta platform utilizing a small amount of HE that can achieve high-throughput at low-cost would benefit a range of experimental facilities.
We performed detailed continuum hydrodynamics simulations to highlight the feasibility of such a platform. Next, we designed a low-cost, high-throughput ejecta source platform—the High Explosive First Ejecta Shock Test Source (HEFESTUS)—to elucidate the ejecta formation process and quantify ejecta production rates. The design utilizes small HE charges (less than 1 g) for ease of use in experimental facilities. We investigated HEFESTUS's sensitivity to generate melt-on-release ejecta with platform geometry, mesh refinement, and materials' equations of state. This research enables us to build an experimental platform to generate first shock ejecta on tin coupons with minimal HE masses to obtain a high-throughput of experiments at relatively low cost.
This research advances Lawrence Livermore National Laboratory's core competencies in advanced materials and additive manufacturing and supports ongoing research the Laboratory's HE physics, chemistry, and materials science R&D challenge areas. The project leverages the strength of the DOE national laboratory complex as HEFESTUS is designed to utilize the Argonne National Laboratory synchrotron for further study in the formation of ejecta. Resulting ejecta physics insights expand DOE and NNSA science and technology capabilities.
Assadi, H., et al. 2016. "Cold spraying a materials perspective." Acta Materialia 116, 382–407. doi:https://doi.org/10.1016/j.actamat.2016.06.034.
Cormier, Y., et al. 2016. "Pyramidal fin arrays performance using streamwise anisotropic materials by cold spray additive manufacturing." Journal of Thermal Spray Technology 25 (1) 170–182. doi: 10.1007/s11666-015-0267-6.
Monfared, S. et al. 2014. "Experimental observations on the links between surface perturbation parameters and shock-induced mass ejection." Journal of Applied Physics 116 (6) 063504. doi:10.1063/1.4891449.
Kirsch, L., et al. 2019. "Hydrodynamics of a low-cost, high-throughput, and compact high-explosive ejecta platform." American Physical Society 29th Shock Compression of Condensed Matter Meeting, Portland, OR, June 2019. LLNL-PRES-774901.
Najjar, F. and J. Sinibaldi. 2019. "On design of high-throughput compact high-explosive ejecta source platform." TMS 2020: Understanding and Predicting Dynamic Behavior of Materials, San Diego, CA. LLNL-ABS-780220.
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