Séminaire - Imaging Shock Waves to Study Initiation in Energetic Materials - Leora Dresselhaus-Cooper

IMPMC - Sorbonne Université - 4 place Jussieu, 75005 Paris, tour 23, 4^e étage, couloir 22-23, salle 401

Lundi 3 décembre 2018, 10 h 30

Leora Dresselhaus-Cooper - Lawrence Livermore National Laboratory - Lawrence Postdoctoral Fellow

Abstract

Shock waves push materials far from equilibrium, causing transformations that permanently alter them. Characterizing the exotic phase transformations or fracture in-situ requires new ultrafast techniques, as shocks irreversibly transform the material at sub-nanosecond timescales. I present a novel imaging diagnostic to capture an ultrafast sequence of images in a single acquisition and use it to characterize the material dynamics initiated by a 150-μm diameter cylindrically converging shock wave. Using a new machine-learning algorithm to quantify the data in these images, I demonstrate new opportunities for shock characterization.

With these and other methods, I then demonstrate how shock waves initiate chemistry in the reactive material 1,3,5-triaza-1,3,5-trinitrocyclohexane (RDX). As much is still unknown about how shock waves initiate chemistry across length-scales, my in-situ experiments and characterization after recovery with single crystals of RDX reveal new insights into the link between mechanics and chemistry. This work demonstrates the ultrafast progression of shock-induced deformations, voids and chemistry, showing strongly thresholded and reproducible dynamics, despite the complicated shock geometry. Our new insight into RDX’s response demonstrates new experimental capabilities that are now possible across shock physics. This work was performed in part under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.