Modeling mesoscale energy localization in shocked HMX, part I: machine-learned surrogate models for the effects of loading and void sizes

Nassar, Anas; K., N.; Sen, Oishik; Udaykumar, H. S.

doi:10.1007/s00193-018-0874-5

Cited by 40 publications

(39 citation statements)

References 38 publications

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“…Wherever possible, fundamental information from experiment is also used. For energetic materials, this sequential approach is the one most commonly used for multiscale model development [5][6][7][8][9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Tandem Molecular Dynamics and Continuum Studies of Shock‐Induced Pore Collapse in TATB

Zhao

Lee

Sewell

et al. 2020

Propellants Explo Pyrotec

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All‐atom molecular dynamics (MD) and Eulerian continuum simulations, performed using the LAMMPS and SCIMITAR3D codes, respectively, were used to study thermo‐mechanical aspects of the shock‐induced collapse of an initially cylindrical 50 nm diameter pore in single crystals of 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB). Three impact speeds, 0.5 km s−1, 1.0 km s−1 and 2.0 km s−1, were used to generate the shocks. These impact conditions are expected to yield collapse mechanisms ranging from predominantly visco‐plastic to hydrodynamic. For the MD studies, three crystal orientations (relative to shock‐propagation direction) were examined that span the limiting cases with respect to the crystalline anisotropy in TATB. An isotropic constitutive model was used for the continuum simulations, thus crystal anisotropy is absent. The evolution of spatiotemporally resolved quantities during collapse is reported including local pressure, temperature, pore size and shape, and material flow. Multiple models for the melting curve and specific heat were studied. Within the isotropic elastic/perfectly plastic continuum framework and for the range of impact conditions studied, the specific heat and melting curve sub‐models are shown to have modest effects on the continuum hotspot predictions in the present inert calculation. Treating the MD predictions as ‘ground truth’, albeit with a classical rather than quantum‐like heat capacity, it is clear that – at a minimum – an extension of the constitutive model to account for crystal plasticity and anisotropic strength will be required for a high‐fidelity continuum description.

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Section: Introductionmentioning

confidence: 99%

Tandem Molecular Dynamics and Continuum Studies of Shock‐Induced Pore Collapse in TATB

Zhao

Lee

Sewell

et al. 2020

Propellants Explo Pyrotec

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“…Part I [3] and this work together describe the techniques to construct surrogate models. While Part I [3] constructed the surrogate model for energy localization due to collapse of isolated cylindrical voids, in this work the effects of void shape variations and void-void interactions are quantified. were constructed in Part I [3].…”

Section: Introductionmentioning

confidence: 99%

Modeling mesoscale energy localization in shocked HMX, Part II: training machine-learned surrogate models for void shape and void–void interaction effects

Roy

Sen

et al. 2019

Shock Waves

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Surrogate models for hotspot ignition and growth rates were presented in Part I, where the hotspots were formed by the collapse of single cylindrical voids. Such isolated cylindrical voids are idealizations of the void morphology in real meso-structures. This paper therefore investigates the effect of non-cylindrical void shapes and void-void interactions on hotspot ignition and growth. Surrogate models capturing these effects are constructed using a Bayesian Kriging approach. The training data for machine learning the surrogates are derived from reactive void collapse simulations spanning the parameter space of void aspect ratio (AR), void orientation ( ), and void fraction ( ). The resulting surrogate models portray strong dependence of the ignition and growth rates on void aspect ratio and orientation, particularly when they are oriented at acute angles with respect to the imposed shock. The surrogate models for void interaction effects show significant changes in hotspot ignition and growth rates as the void fraction increases. The paper elucidates the physics of hotspot evolution in void fields due to the creation and interaction of multiple hotspots. The results from this work will be useful not only for constructing meso-informed macro-scale models of HMX, but also for understanding the physics of void-void interactions and sensitivity due to void shape and orientation.

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“…Considering the different numerical modelling and simulation efforts for heterogeneous explosives, many of these can be divided into one of two approaches. One approach is aimed at studying explosives initiation (mesoscale) , while the other is aimed at studying propagation (continuum) . A third approach, atomistic simulations, is acknowledged here as it pertains to the mesoscale, but it is not discussed in detail.…”

Section: Introductionmentioning

confidence: 99%

“…Current research is progressing to close this knowledge gap from both sides. Finite element analysis (FEA) and Eulerian/Lagrangian hydrocodes, together with modern computing resources allow for an image to computation approach for mesoscale modelling ; in this approach, microstructure images are obtained both experimentally and synthetically .…”

Section: Introductionmentioning

confidence: 99%

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Modelling the Fluctuations of Reactive Shock Waves in Heterogeneous Solid Explosives as Stochastic Processes

Kittell

Yarrington

Lechman

et al. 2019

Propellants Explo Pyrotec

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While current phenomenological burn models are useful for describing the average or bulk reactive flow behaviour of heterogeneous explosives, one fundamental weakness inherent to these models is the loss of detailed microstructural information at the scale of the calculation. In order to include the effects of the microstructure, and in particular the underlying material heterogeneities that influence the build‐up to detonation, a new paradigm is put forth for modelling sub‐grid, reaction‐induced fluctuations (i. e. “hot spots”) at the continuum level. This modelling approach assumes that the reaction rate is stochastic, rather than deterministic, and it uses Langevin‐type equations with a mathematical framework built upon Itô calculus and Lambourn's CIM model for shocked heterogeneous explosives. This approach follows directly from our previous letter, Ref. [1], and is inspired by the probability density function (pdf) methods used in turbulent reactive flows. Here, the stochastic burn model is derived, implemented, and exercised far beyond what has been shown in previous work. New hydrocode simulation results demonstrate the role of stochastic fluctuations during shock initiation; these fluctuations are approximated by collections of discrete particles, that evolve with drift (i. e. deterministic) and diffusion (i. e. stochastic) coefficients. Additionally, the particle values are propagated and averaged to calculate the heat release, yield strength, and material impedance in each computational cell. Hydrocode simulation results further show how the fluctuating hot spot energy may or may not be transmitted to the wave front, and result in a detonation wave‐like structure. The fundamental stochastic nature of this model permits simulations to have varying outcomes with the same initial conditions; this allows for go/no‐go estimation (e. g., marginal or failed detonations), which might possibly be calibrated using the statistical distributions from real materials. Mesoscale calculations of shocked heterogeneous explosives also show that these fluctuations are physically justified (i. e., Ref. [2]), and it is hypothesized that the pdf functions provide a link between the meso(grain) and continuum scales for practical engineering calculations. Thus, our approach is a paradigm shift for building efficient, reduced order continuum burn models, that represent the sub‐grid stochastic behaviour of shocked heterogeneous solid explosives.

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Modeling mesoscale energy localization in shocked HMX, part I: machine-learned surrogate models for the effects of loading and void sizes

Cited by 40 publications

References 38 publications

Tandem Molecular Dynamics and Continuum Studies of Shock‐Induced Pore Collapse in TATB

Tandem Molecular Dynamics and Continuum Studies of Shock‐Induced Pore Collapse in TATB

Modeling mesoscale energy localization in shocked HMX, Part II: training machine-learned surrogate models for void shape and void–void interaction effects

Modelling the Fluctuations of Reactive Shock Waves in Heterogeneous Solid Explosives as Stochastic Processes

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