Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session Z2: TMS: Mesoscale Explosive Initiation V |
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Chair: Avinash Dongare, UCONN Room: Grand Ballroom II |
Friday, June 21, 2019 11:00AM - 11:15AM |
Z2.00001: A unified view of burn models for energy localization due to hotspot ignition and growth in shocked energetic materials H. S. Udaykumar, Sangyup Lee, Nirmal Rai, Angela Diggs, Barrett Hardin Shock-to-detonation transition (SDT) in an energetic material can occur if the rate of chemical energy deposition is sufficiently rapid that there is a coupling between the shock and chemical reactions. Arrhenius kinetics cannot meet the time scale requirement. Therefore, ``burn models'' have traditionally been used to provide the power deposition needed for modeling of SDT. We show that burn models, such as the multiple Arrhenius reactors viewpoint, the SURF model and the ignition-and-growth (IG) model, all lead to a common time scale for the energy deposition rate. Tthis common time scale is shown to depend on the average void size in the control volume, is inversely proportional to the porosity and is inversely proportional to the rate of area change of a representative hot spot. This is consistent with experiments and physical expectations, since smaller voids and larger porosity will increase sensitivity; larger rates of change of areas will also increase the sensitivity. The common time scale among ignition-and-growth based burn models allows for a unified approach to construct meso-informed reactive burn models using high-fidelity meso-scale numerical simulations; this approach is applied to construct a surrogate model for energy localization rate. [Preview Abstract] |
Friday, June 21, 2019 11:15AM - 11:30AM |
Z2.00002: Multi-scale modeling of the shock response of energetic materials: Comparing HMX and TATB Anas Nassar, Nirmal Kumar Rai, Oishik Sen, H. S. Udaykumar Hot spots in heterogenous energetic materials (HEs) are localized sites where self-sustaining chemical reactions are initiated. Hotspots in HEs subjected to shock loading can result from the closure of voids, cracks, or defects within the micro-structure, i.e. at the meso-scale. Macro-scale quantities of interest (QoIs), such as shock to detonation transition (SDT), run-to-detonation distance, and criticality hinge on the rates of chemical reactions initiated at meso-scale hotspots. In previous work, we developed multi-scale models coupling the meso- and macro-scales for pressed HMX. The bridge between scales is provided by surrogate models (a.k.a. metamodels) that encapsulate energy localization phenomena at hotspots. The work presented here compares metamodels for two HEs, viz. HMX and TATB, along with their criticality criteria. High resolution meso-scale calculations supply the input data to construct metamodels which facilitate comparison of the behaviors of the two different materials. The physics underlying the differences in sensitivity of the two materials is elucidated by the calculations of void collapse and hotspot ignition and growth in the two materials. Metamodels for the materials and the way in which macro-scale sensitivity relates to meso-scale physics are also revealed by the results obtained from this work. [Preview Abstract] |
Friday, June 21, 2019 11:30AM - 11:45AM |
Z2.00003: Establishing structure-property-performance linkages for energetic materials Sidhartha Roy, Oishik Sen, Nirmal Rai, Min-Yeong Moon, Kyung Choi, Chirstopher Molek, Eric Welle, Angela Diggs, David Hardin, H S Udaykumar This work details a framework for establishing structure-property-performance linkages for energetic materials using a multi-scale simulation approach. A MESo-informed Ignition and Growth model (MES-IG) is used to quantify performance, i.e. loading conditions for shock-to-detonation transition. Physical descriptors are used to characterize SEM-imaged microstructures for three classes of HMX based pressed energetics. Meso-scale reactive void collapse simulations are performed to establish the link between the meso-structure and meso-scale physical response; structure-property linkages. The structure-property linkage is then encapsulated in a surrogate model for the rate of ignition and growth of reaction fronts. The machine-learned surrogate models are used to provide closure at the macroscale, resulting in microstructure aware simulations of shock-to-detonation transition. James curves and pop plots are developed for each Class of the pressed HMX and compared with experimental data. The uncertainty due to stochastic micro-structures are quantified by constructing probability distributions of the microstructural descriptors and quantifying the effects of individual descriptors on the macroscale QoIs. This framework can be used to design a wide variety of energetic materials. [Preview Abstract] |
Friday, June 21, 2019 11:45AM - 12:00PM |
Z2.00004: Three-dimensional Microstructure-explicit and Void-explicit Mesoscale Simulations of the Detonation of HMX Daniel Olsen, Christopher Miller, Yaochi Wei, Min Zhou 3D microstructure-explicit and void-explicit mesoscale simulations of the shock-to-detonation (SDT) process of pressed granular HMX are performed. The overall size scale of the models are up to $3\times3\times15$ millimeters. The models account for the heterogeneous material microstructure, constituent distribution, morphology, and voids. A viscoplastic constitutive law, the Mie-Gr{\"u}neisen EOS, and the HVRB (History Variable Reactive Burn) chemistry model are used. Companion two-dimensional simulations are also carried out using cross-sections of the 3D samples to assess the differences between the 2D and 3D simulations in a fully consistent setting. Statistically equivalent microstructure sample sets (SEMSS) are generated and used, allowing the prediction of the statistical and probabilistic Pop plots (PP). The predictions are in agreement with available experimental data in the literature. It is found that both the microstructure (heterogeneous grain size, morphology, and distribution) and voids significantly affect the PP. These effects are systematically delineated and quantified via different combinations of simulations for homogenous material with no microstructure and voids and simulations that account for microstructure, voids, and both microstructure and voids. [Preview Abstract] |
Friday, June 21, 2019 12:00PM - 12:15PM |
Z2.00005: Mesoscale microstructure-explicit simulations for predicting the ignition thresholds of polymer-bonded explosives Yaochi Wei, Ju Hwan Shin, Christopher Miller, Min Zhou Two-dimensional (2D) and three-dimensional (3D), Lagrangian, microstructure-explicit simulations are carried out to systematically assess how microstructural heterogeneities affect the ignition behaviors of polymer-bonded explosives (PBXs). The analysis provides explicit account of the heterogeneous material microstructure and captures the effects of mechanical, thermal, and chemical processes up to and around the ignition in samples at scales up to tens of millimeters. The specific mechanisms considered include viscoelasticity, viscoplasticity, fracture, post-fracture contact, frictional heating, and heat conduction. The Henson chemical decomposition model is used to track the species during reaction. Ignition behaviors are studied for piston velocities ranging between 600 m/s - 1200 m/s (shock pressures of 4 - 11 GPa). Statistically equivalent microstructure sample sets (SEMSS) are generated and used, enabling a probabilistic characterization of the ignition thresholds. The effects of microstructural attributes, including size and morphology of grains and content and size distribution of voids on ignition are delineated. [Preview Abstract] |
Friday, June 21, 2019 12:15PM - 12:30PM |
Z2.00006: ABSTRACT WITHDRAWN |
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