Title: Sensitivity of pore collapse heating to the melting temperature and shear viscosity of HMX

Abstract

A multiscale modeling strategy is used to quantify factors governing the temperature rise in hot spots formed by pore collapse from supported and unsupported shock waves in the high explosive HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). Two physical aspects are examined in detail, namely the melting temperature and liquid shear viscosity. All-atom molecular dynamics simulations of phase coexistence are used to predict the pressure-dependent melting temperature up to 5 GPa. Equilibrium simulations and the Green–Kubo formalism are used to obtain the temperature- and pressure-dependent liquid shear viscosity. Starting from a simplified continuum-based grain-scale model of HMX, in this study we systematically increase the complexity of treatments for the solid–liquid phase transition and liquid shear viscosity in simulations of pore collapse. Using a realistic pressure-dependent melting temperature completely suppresses melting for supported shocks, which is otherwise predicted when treating it as a constant determined at atmospheric pressure. Alternatively, melt pools form around collapsed pores when the pressure (and melting temperature) are reduced during the release stage of unsupported shocks. Capturing the pressure dependence of the shear viscosity increases the peak temperature of melt pools by hundreds of Kelvin through viscous work. The complicated interplay of the solid-phase plastic work, solid–liquid phase transition, and liquid-phase viscousmore » work identified here motivate taking a systematic approach to building increasingly complex grain-scale models.« less

Authors:

Kroonblawd, Matthew P.  ^[1];

• Search DOE PAGES for author "Kroonblawd, Matthew P."
• Search DOE PAGES for ORCID "0000-0002-5009-5998"

Austin, Ryan A.  ^[1]

• Search DOE PAGES for author "Austin, Ryan A."
• Search DOE PAGES for ORCID "0000-0002-4548-6783"

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+ Show Author Affiliations

1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:

Mon Nov 02 00:00:00 EST 2020

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1769080

Alternate Identifier(s):

OSTI ID: 1776453

Report Number(s):

LLNL-JRNL-809399
Journal ID: ISSN 0167-6636; 1015388

Grant/Contract Number:  

AC52-07NA27344

Resource Type:

Accepted Manuscript

Journal Name:

Mechanics of Materials

Additional Journal Information:

Journal Volume: 152; Journal ID: ISSN 0167-6636

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; hot spots; melting; multiscale modeling; molecular crystals; shock waves; momentum transport