On resolving meso-scale calculations of pore-collapse-generated hotspots in energetic crystals for consistency with atomistic models

Chukwudubem Okafor; Jacob Herrin; Catalin R Picu; Tommy Sewell; John Brennan; James Larentzos; H. S Udaykumar

doi:10.48550/arxiv.2410.22174

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On resolving meso-scale calculations of pore-collapse-generated hotspots in energetic crystals for consistency with atomistic models

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On resolving meso-scale calculations of pore-collapse-generated hotspots in energetic crystals for consistency with atomistic models

Chukwudubem Okafor, Jacob Herrin, Catalin R Picu, Tommy Sewell, John Brennan, James Larentzos and H. S Udaykumar

ArXiv.org

Cornell University

10/29/2024

DOI: 10.48550/arxiv.2410.22174

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Preprint (Author's original) This preprint has not been evaluated by subject experts through peer review. Preprints may undergo extensive changes and/or become peer-reviewed journal articles. Open Access

Abstract

Meso-scale calculations of pore collapse and hotspot formation in energetic crystals provide closure models to macro-scale hydrocodes for predicting the shock sensitivity of energetic materials. To this end, previous works obtained atomistics-consistent material models for two common energetic crystals, HMX and RDX, such that pore collapse calculations adhered closely to molecular dynamics (MD) results on key features of energy localization, particularly the profiles of the collapsing pores, appearance of shear bands, and the transition from viscoplastic to hydrodynamic collapse. However, some important aspects such as the temperature distributions in the hotspot were not as well captured. One potential issue was noted but not resolved adequately in those works, namely the grid resolution that should be employed in the meso-scale calculations for various pore sizes and shock strengths. Conventional computational mechanics guidelines for selecting meshes as fine as possible, balancing computational effort, accuracy and grid independence, were shown not to produce physically consistent features associated with shear localization. Here, we examine the physics of pore collapse, shear band evolution and structure, and hotspot formation, for both HMX and RDX; we then evaluate under what conditions atomistics-consistent models yield physically correct (considering MD as ground truth) hotspots for a range of pore diameters, from nm to microns, and for a wide range of shock strengths. The study provides insights into the effects of pore size and shock strength on pore collapse and hotspots, identifying aspects such as size-independent behaviors, and proportion of energy contained in shear as opposed to jet impact-heated regions of the hotspot. Areas for further improvement of atomistics-consistent material models are also indicated.

Physics - Computational Physics

Physics - Materials Science

Physics - Mesoscale and Nanoscale Physics

Details

Title: Subtitle: On resolving meso-scale calculations of pore-collapse-generated hotspots in energetic crystals for consistency with atomistic models
Creators: Chukwudubem Okafor - University of Iowa
Jacob Herrin - University of Iowa
Catalin R Picu - Rensselaer Polytechnic Institute
Tommy Sewell - University of Missouri
John Brennan - DEVCOM Army Research Laboratory
James Larentzos - DEVCOM Army Research Laboratory
H. S Udaykumar - University of Iowa
Resource Type: Preprint
Publication Details: ArXiv.org
DOI: 10.48550/arxiv.2410.22174
ISSN: 2331-8422
Publisher: Cornell University; Ithaca, New York
Language: English
Date posted: 10/29/2024
Academic Unit: IIHR--Hydroscience and Engineering; Injury Prevention Research Center; Mechanical Engineering
Record Identifier: 9984740960002771

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